JP7038031B2 - Abrasive grain dispersion for polishing containing ceria-based composite fine particle dispersion, its manufacturing method, and ceria-based composite fine particle dispersion. - Google Patents

Description

The present invention relates to a ceria-based composite fine particle dispersion suitable as a polishing agent used in semiconductor device manufacturing and the like, and in particular, a film to be polished formed on a substrate is flattened by chemical mechanical polishing (CMP). The present invention relates to a ceria-based composite fine particle dispersion, a method for producing the same, and a polishing abrasive grain dispersion containing the ceria-based composite fine particle dispersion.

Semiconductor devices such as semiconductor boards and wiring boards have achieved high performance by increasing the density and miniaturization. So-called chemical mechanical polishing (CMP) is applied in the manufacturing process of this semiconductor. Specifically, it is an essential technology for separating shallow trench elements, flattening an interlayer insulating film, and forming contact plugs and Cu damascene wiring. It has become.

Generally, an abrasive for CMP is composed of abrasive grains and a chemical component, and the chemical component plays a role of promoting polishing by oxidizing or corroding the target film. On the other hand, the abrasive grains have a role of polishing by mechanical action, and colloidal silica, fumed silica, and ceria particles are used as the abrasive grains. In particular, ceria particles show a specifically high polishing rate with respect to the silicon oxide film, and are therefore applied to polishing in the shallow trench element separation step.
In the shallow trench element separation step, not only the silicon oxide film is polished, but also the silicon nitride film is polished. In order to facilitate element separation, it is desirable that the polishing rate of the silicon oxide film is high and the polishing rate of the silicon nitride film is low, and this polishing rate ratio (selection ratio) is also important.

Conventionally, as a method for polishing such a member, a relatively rough primary polishing process is then performed, and then a precise secondary polishing process is performed to obtain a smooth surface or an extremely high-precision surface with few scratches and the like. How to get is done.
Conventionally, for example, the following methods have been proposed with respect to the polishing agent used for the secondary polishing as such finish polishing.

For example, in Patent Document 1, an aqueous solution of first cerium nitrate and a base are stirred and mixed at an amount ratio of 5 to 10 and then rapidly heated to 70 to 100 ° C. and aged at that temperature. A method for producing ultrafine particles of cerium oxide (average particle diameter of 10 to 80 nm) made of a cerium oxide single crystal is described, and further, according to this production method, the particle size is highly uniform and the particle shape is high. It is stated that cerium oxide ultrafine particles having high uniformity can be provided.

Further, Non-Patent Document 1 discloses a method for producing ceria-coated silica, which comprises a production process similar to the method for producing cerium oxide ultrafine particles described in Patent Document 1. This method for producing ceria-coated silica does not have a firing-dispersion step as included in the production method described in Patent Document 1.

Further, Patent Document 2 has child particles containing crystalline ceria as a main component on the surface of a mother particle containing amorphous silica as a main component, and further has a silica film on the surface of the child particles. , A silica-based composite fine particle dispersion liquid containing silica-based composite fine particles having an average particle diameter of 50 to 350 nm and having the following characteristics [1] to [3] is described. [1] The silica-based composite fine particles have a mass ratio of 100: 11 to 316 between components other than ceria and ceria. [2] When the silica-based composite fine particles are subjected to X-ray diffraction, a crystal phase of ceria and a crystal phase of a crystalline inorganic oxide are detected. [3] The silica-based composite fine particles have a crystallinity diameter of 10 to 25 nm on the (111) plane of the crystalline ceria, which is measured by subjecting it to X-ray diffraction. Further, according to such silica-based composite fine particles, even a silica film, a Si wafer or a difficult-to-process material can be polished at high speed, and at the same time, high surface accuracy (low scratch, surface roughness of the substrate to be polished (low scratch, surface roughness of the substrate to be polished) ( It is possible to provide a silica-based composite fine particle dispersion liquid that can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring substrates because Ra) can be achieved (such as low) and contains no impurities. Are listed.

Japanese Patent No. 2,746,861 International Publication No. 2016/159167 Pamphlet

Seung-Ho Lee, Zhenyu Lu, S.M. V. Babu and Egon Matijevic, "Chemical mechanical polishing of thermal oxide films sillica particles coated with 27 seria", Journal of

However, when the present inventor actually manufactured and examined the cerium oxide ultrafine particles described in Patent Document 1, the polishing speed was low, and further, defects on the surface of the polishing substrate (deterioration of surface accuracy, increase in scratches, It was found that the residual abrasive material on the surface of the polishing substrate) is likely to occur.
This is because the method for producing cerium oxide ultrafine particles described in Patent Document 1 does not include a firing step and is a liquid phase, as compared with a method for producing ceria particles including a firing step (the degree of crystallization of ceria particles is increased by firing). Since the cerium oxide particles are only crystallized from (an aqueous solution containing primary cerium nitrate), the degree of crystallization of the generated cerium oxide particles is relatively low, and since the cerium oxide particles are not fired, the cerium oxide is solidified with the mother particles. The present inventor presumes that the main factor is that cerium oxide remains on the surface of the polished substrate without being attached.

Further, since the ceria-coated silica described in Non-Patent Document 1 is not fired, it is considered that the actual polishing rate is low, and since it is not fixedly integrated with the silica particles, it easily falls off and the polishing rate is lowered. In addition, the stability of polishing is lacking, and there is a concern that particles may remain on the surface of the polishing substrate.

Further, the silica-based composite fine particle dispersion liquid described in Patent Document 2 can exhibit excellent polishing performance (polishing speed, high surface accuracy, etc.) in polishing applications, but further increases the density of semiconductor devices. -With the increase in integration, there is a demand for an abrasive grain dispersion liquid that exhibits better polishing performance for semiconductor substrates.

An object of the present invention is to solve the above problems. That is, the present invention can polish a silica film, a Si wafer, or a difficult-to-process material at high speed, and at the same time, it has high surface accuracy (low scratch, less abrasive residue on the substrate, and improvement of the substrate Ra value. Etc.) and can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring substrates when they can achieve and do not contain impurities. It is an object of the present invention to provide an abrasive grain dispersion liquid for polishing containing.

The present inventor has diligently studied to solve the above problems and completed the present invention.
The present invention is the following (1) to (9).
(1) Contains ceria-based composite fine particles having the following characteristics [1] to [5], a minor axis / major axis ratio in the range of 0.2 to 1.0, and an average particle diameter of 50 to 1000 nm. Ceria-based composite fine particle dispersion.
[1] The ceria-based composite fine particles have a mother particle, a cerium-containing coating layer on the surface of the mother particle, and child particles dispersed inside the cerium-containing coating layer, and the mother particle is The main component is crystalline inorganic oxide, and the child particles are mainly composed of crystalline cerium.
[2] The coefficient of variation (CV value) in the particle size distribution of the child particles is 14 to 60%.
[3] The ceria-based composite fine particles have a mass ratio of a component other than ceria and ceria in the range of 100: 11 to 316.
[4] When the ceria-based composite fine particles are subjected to X-ray diffraction, the crystal phase of ceria and the crystal phase of the crystalline inorganic oxide are detected.
[5] The ceria-based composite fine particles have an average crystallinity diameter of 10 to 25 nm, which is measured by subjecting them to X-ray diffraction.
(2) The ceria-based composite fine particle dispersion liquid according to (1) above, wherein the crystalline inorganic oxide is at least one selected from the group consisting of alumina, titania and zirconia.
(3) The ceria-based composite fine particle dispersion liquid according to (1) or (2) above, wherein the cerium-containing coating layer contains the same elements and cerium as the mother particles.
(4) The ceria-based composite fine particle dispersion liquid according to any one of (1) to (3) above, wherein the cerium-containing coating layer contains silica.
(5) The ceria-based composite fine particle dispersion liquid according to any one of (1) to (4) above, wherein the compression fracture strength of the mother particles is 1.0 to 3.0 MPa.
(6) A polishing abrasive grain dispersion liquid containing the ceria-based composite fine particle dispersion liquid according to any one of (1) to (5) above.
(7) The abrasive grain dispersion liquid for polishing according to (6) above, which is used for flattening a semiconductor substrate on which a silica film is formed.
(8) A method for producing a ceria-based composite fine particle dispersion, which comprises the following steps 1 to 3.
Step 1: Stir the crystalline inorganic oxide fine particle dispersion liquid in which the crystalline inorganic oxide fine particles having a minor axis / major axis ratio of 0.1 or more and less than 1.0 are dispersed in a solvent, and set the temperature to 0 to 20. A precursor particle dispersion containing precursor particles by continuously or intermittently adding a metal salt of cerium to the temperature, pH of 7.0 to 9.0, and redox potential of 50 to 500 mV. The process of obtaining.
Step 2: The precursor particle dispersion is dried, calcined at 700 to 1,200 ° C., a solvent is added to the obtained calcined product, and the mixture is crushed in a wet manner in the range of pH 8.6 to 10.8. A process of processing to obtain a calcined body crushed dispersion.
Step 3: A step of centrifuging the fired body crushed dispersion at a relative centrifugal acceleration of 300 G or more, and subsequently removing the sedimentation component to obtain a ceria-based composite fine particle dispersion.
(9) In step 1, the crystalline inorganic oxide fine particle dispersion is stirred, and the temperature is maintained at 0 to 20 ° C., the pH is 7.0 to 9.0, and the redox potential is 50 to 500 mV. The method for producing a ceria-based composite fine particle dispersion according to (8) above, which is a step of continuously or intermittently adding a metal salt of cerium and a component containing silicon to obtain the precursor particle dispersion. ..

When the ceria-based composite fine particle dispersion of the present invention is used for polishing as an abrasive grain dispersion for polishing, for example, even if the target is a difficult-to-process material containing a silica film, a Si wafer, etc., it can be polished at high speed. At the same time, high surface accuracy (low scratch, low surface roughness (Ra) of the substrate to be polished, etc.) can be achieved. The method for producing a ceria-based composite fine particle dispersion liquid of the present invention provides a method for efficiently producing a ceria-based composite fine particle dispersion liquid exhibiting such excellent performance.
In the method for producing a ceria-based composite fine particle dispersion liquid of the present invention, impurities contained in the ceria-based composite fine particles can be significantly reduced and the purity can be increased. The highly purified ceria-based composite fine particle dispersion obtained by the preferred embodiment of the method for producing a ceria-based composite fine particle dispersion of the present invention contains no or almost no impurities, and therefore, a semiconductor substrate, a wiring substrate, etc. It can be preferably used for polishing the surface of a semiconductor device.
Further, the ceria-based composite fine particle dispersion of the present invention is effective for flattening the surface of a semiconductor device when used as an abrasive grain dispersion for polishing, and is particularly suitable for polishing a substrate on which a silica insulating film is formed. be.

It is a schematic diagram of the cross section of the composite fine particle of this invention.

The present invention will be described.
The present invention includes the following features [1] to [5], a ceria-based composite fine particles having a minor axis / major axis ratio in the range of 0.2 to 1.0 and an average particle diameter of 50 to 1000 nm. , Ceria-based composite fine particle dispersion.
[1] The ceria-based composite fine particles have a mother particle, a cerium-containing coating layer on the surface of the mother particle, and child particles dispersed inside the cerium-containing coating layer, and the mother particle is The main component is crystalline inorganic oxide, and the child particles are mainly composed of crystalline cerium.
[2] The coefficient of variation (CV value) in the particle size distribution of the child particles is 14 to 60%.
[3] The ceria-based composite fine particles have a mass ratio of a component other than ceria and ceria in the range of 100: 11 to 316.
[4] When the ceria-based composite fine particles are subjected to X-ray diffraction, the crystal phase of ceria and the crystal phase of the crystalline inorganic oxide are detected.
[5] The ceria-based composite fine particles have an average crystallinity diameter of 10 to 25 nm, which is measured by subjecting them to X-ray diffraction.

Ceria-based composite fine particles having the above-mentioned characteristics [1] to [5] and having a minor axis / major axis ratio in the range of 0.2 to 1.0 and an average particle diameter of 50 to 1000 nm are referred to as "composite of the present invention" below. Also called "fine particles".
Further, such a ceria-based composite fine particle dispersion is also referred to as "dispersion of the present invention" below.

Further, the present invention is a method for producing a ceria-based composite fine particle dispersion liquid, which comprises the following steps 1 to 3.
Step 1: Stir the crystalline inorganic oxide fine particle dispersion liquid in which the crystalline inorganic oxide fine particles having a minor axis / major axis ratio of 0.1 or more and less than 1.0 are dispersed in a solvent, and set the temperature to 0 to 20. A precursor particle dispersion containing precursor particles by continuously or intermittently adding a metal salt of cerium to the temperature, pH of 7.0 to 9.0, and redox potential of 50 to 500 mV. The process of obtaining.
Step 2: The precursor particle dispersion is dried, calcined at 700 to 1,200 ° C., a solvent is added to the obtained calcined product, and the mixture is crushed in a wet manner in the range of pH 8.6 to 10.8. A process of processing to obtain a calcined body crushed dispersion.
Step 3: A step of centrifuging the fired body crushed dispersion at a relative centrifugal acceleration of 300 G or more, and subsequently removing the sedimentation component to obtain a ceria-based composite fine particle dispersion.
Such a manufacturing method is also referred to as "the manufacturing method of the present invention" below.

The dispersion liquid of the present invention is preferably produced by the production method of the present invention.

In the following, when the term "invention" is simply used, it means any of the dispersion liquid of the present invention, the composite fine particles of the present invention, and the production method of the present invention.

<Composite fine particles of the present invention>
The composite fine particles of the present invention will be described.
The composite fine particles of the present invention have the structure illustrated in FIG. 1 (a) and 1 (b) are both schematic views of a cross section of the composite fine particles of the present invention. FIG. 1A is a type in which a part of the child particles is exposed to the outside, and FIG. 1B is a buried type in which all the child particles are not exposed to the outside.
As shown in FIG. 1, the composite fine particles 20 of the present invention include the mother particles 10, the cerium-containing coating layer 12 on the surface of the mother particles 10, and the child particles 14 dispersed inside the cerium-containing coating layer 12. Have. Note that ▲ in FIG. 1 is an example of measurement points X to Z for performing STEM-EDS analysis, which will be described later.

The present inventor presumes the mechanism by which the cerium-containing coating layer is formed in the composite fine particles of the present invention and the mechanism by which the child particles are dispersed and exist inside the cerium-containing coating layer as follows. ..
As will be described later, representative examples of the crystalline inorganic oxide constituting the crystalline inorganic oxide fine particles include alumina, titania, and zirconia, and there are cases where silica is further contained. In the following, crystalline inorganic oxidation A case where the substance is alumina will be described.
For example, crystalline inorganic obtained by adding ammonia to aluminum isopropoxide, performing hydrolysis / shrink polymerization operations, and further drying and firing to disperse crystalline inorganic oxide fine particles in a solvent. When the alkali is added in parallel with the solution of the cerium salt to the oxide particle dispersion, the solution of the cerium salt is neutralized. Then, the hydroxyl group on the surface of the crystalline inorganic oxide fine particles reacts with the product (cerium hydroxide, etc.) obtained by neutralizing the solution of the cerium salt, and as an example, Ce (OH) / Al (OH) -like A layer containing CeO ₂ , Al ₂ O ₃ , Al (OH) and CeO ₂ ultrafine particles (particle size of 2.5 nm or more and less than 10 nm) on the surface of crystalline inorganic oxide fine particles via a compound ( Hereinafter, it is also referred to as “CeO ₂ ultrafine particle-containing layer”, which means a layer composed of CeO ₂ ultrafine particles and cerium aluminumate). Since the cerium atom phase-separated from the cerium aluminate is deposited on the CeO ₂ ultrafine particles in the firing step, the CeO ₂ ultrafine particles formed on the surface of the crystalline inorganic oxide fine particles grow into particles. In order to obtain the crystal size (10 to 25 nm) of the ceria child particles to achieve the required polishing rate, if the crystallite diameter obtained by the formulation is less than 2.5 nm, higher temperature firing is required. It is said that. However, when treated at a high temperature, the alumina generated in the phase separation becomes an adhesive, and the single crystalline ceria-based composite fine particles of the present invention cannot be obtained by crushing in a subsequent step.
Since the crystalline inorganic oxide is alumina here, the CeO ₂ ultrafine particle-containing layer is a layer composed of CeO ₂ ultrafine particles and cerium aluminate, but as a crystalline inorganic oxide, alumina is used. If it is titania, the CeO ₂ ultrafine particle-containing layer is a layer composed of CeO ₂ ultrafine particles and cerium titanate, and if the crystalline inorganic oxide is zirconia instead of alumina, the CeO ₂ ultrafine particle-containing layer is , CeO ₂ Ultrafine particles and cerium zirconate.

In order to obtain CeO ₂ ultrafine particles having an average particle diameter of 2.5 nm or more in the compounding step (step 1), a crystalline inorganic oxide is added when the cerium salt is added in order to suppress the reaction between the cerium salt and the alumina. The temperature of the fine particle dispersion is preferably 20 ° C. or lower. At this time, some CeO ₂ ultrafine particles are already crystallized without heating and aging by keeping the redox potential during preparation within a predetermined range. On the other hand, even if the mixture is prepared at a temperature of more than 20 ° C. and then heat-treated and aged in the liquid phase, the CeO ₂ ultrafine particles do not grow to 2.5 nm or more, and crystallization tends to be difficult to occur.

In the CeO ₂ ultrafine particle-containing layer, the surface of the crystalline inorganic oxide fine particles is formed by the reaction between the surface hydroxyl group of the crystalline inorganic oxide fine particles and the product (cerium hydroxide, etc.) obtained by neutralizing the solution of the cerium salt. It is presumed that it was formed by elution and solidification due to the influence of oxygen and the like (derived from the blown air and the like).
Then, when it is dried and fired at about 700 to 1200 ° C., the CeO ₂ ultrafine particles having a particle size of 2.5 nm or more and less than 10 nm existing inside the CeO ₂ ultrafine particle-containing layer are cerium aluminum. The cerium atom contained in the nate is taken in to grow the particle size, and finally, the crystalline ceria particles (ceria child particles) are grown to an average crystallite diameter of about 10 to 25 nm. Further, cerium aluminate becomes a cerium-containing coating layer by thermal decomposition, thermal diffusion, or the like. Therefore, the crystalline ceria particles are present in a dispersed state in the cerium-containing coating layer. In addition, crystalline ceria particles (child particles) formed by such a mechanism are unlikely to cause coalescence of particles. Since a part of cerium contained in the cerium silicate layer cannot be completely formed into crystalline ceria particles and remains, a cerium-containing coating layer is formed.

When the compounding temperature exceeds 20 ° C. and the redox potential is kept within a predetermined range, the reactivity between cerium hydroxide and the like and the crystalline inorganic oxide fine particles increases, and the elution amount of the crystalline inorganic oxide fine particles increases. The number of crystalline inorganic oxide fine particles after preparation is significantly increased, and the particle size of the prepared crystalline inorganic oxide fine particles is reduced by, for example, about 1/2, and the volume is reduced by 80 to 90%. The dissolved alumina is contained in the CeO ₂ ultrafine particle-containing layer, and in the case of the above example, the composition of the CeO ₂ ultrafine particle-containing layer is such that the alumina concentration is about 40% and the ceria concentration is about 60%, and the CeO ₂ ultrafine particle content is contained. The proportion of alumina in the layer increases. Then, when the ceria particles are crystal-grown to 10 to 25 nm by firing, the cerium atoms phase-separated from the cerium aluminate layer are deposited and grown on the ceria particles, and as a result, the phase separation (diffusion) of the cerium atoms results in the cerium atoms. The generated alumina coats the ceria particles, adheres to the mother particle alumina, and the ceria child particles are covered with the alumina film. At this time, if the firing temperature is high, the alumina coated with the ceria-coated mother particles acts as an adhesive and promotes the coalescence of the particles. Can not. If the firing temperature is low, crushing is easy, but since ceria particles do not grow, the polishing rate cannot be obtained.

Further, when the compounding temperature is over 20 ° C. and the oxidation-reduction potential is kept within a predetermined range, the crystallite diameter of the compounded cerium particles becomes as small as 2.5 nm or less, and the cerium particles are crystallized to a predetermined size by firing. In order to grow, more cerium atoms need to be diffused from the cerium aluminate, and as a result, the alumina concentration in the cerium aluminate increases, and the alumina film covering the child particles tends to increase.

When the compounding temperature at the time of reaction between the crystalline inorganic oxide fine particle dispersion and the metal salt of cerium is 0 to 20 ° C. and the redox potential is kept within a predetermined range, cerium hydroxide or the like and the crystalline inorganic oxide fine particles are used. The reactivity of the crystalline inorganic oxide fine particles is suppressed, and the crystalline inorganic oxide fine particles after preparation are reduced, for example, the particle size is reduced by about 1 to 5% and the volume is reduced by about 3 to 15%. It can be suppressed. Therefore, in the case of the above example, the composition of the CeO ₂ ultrafine particle-containing layer has an alumina concentration of about 10% and a ceria concentration of about 90%, the proportion of ceria in the CeO ₂ ultrafine particle-containing layer increases, and cerium is contained after firing. A coating layer is formed. Further, since the crystal size of ceria after preparation is about 2.5 nm or more and less than 10 nm (6 to 8 nm as an example), the amount of diffusion of cerium atoms for growing ceria particles to a predetermined size by firing is small. Well, as a result, a large amount of cerium remains in the cerium aluminate, crystal growth occurs by low-temperature firing, and ceria particles having an average particle diameter of 10 to 25 nm can be obtained. Therefore, when the mixture is prepared at 0 to 20 ° C., a cerium-containing coating layer is formed on the surface of the mother particles, and the ceria child particles are dispersed in this layer.

Further, in the compounding stage, when the ceria particles have an average particle diameter of 10 nm or more, the ceria particles are coalesced with each other, and the uniform ceria particles are not monodispersed on the surface of the mother particles, so that excellent polishing characteristics tend not to be obtained. be.

In the schematic diagram of FIG. 1, the mother particle 10, the cerium-containing coating layer 12, and the child particles 14 are clearly distinguished for easy understanding, but the composite fine particles of the present invention are formed by the above mechanism. In reality, they exist as one, and the mother particle 10, the cerium-containing coating layer 12, and the child particle 14 are clearly defined except for the contrast or EDS analysis in the STEM / SEM image. It is difficult to distinguish between.
However, when the cross section of the composite fine particles of the present invention is subjected to STEM-EDS analysis and the element concentration of Ce is measured, it can be confirmed that the structure is as shown in FIG.

That is, EDS analysis is performed in which an electron beam is selectively irradiated to a location specified by a scanning transmission electron microscope (STEM), and the element concentration of Ce at the measurement point X of the cross section of the composite fine particles of the present invention shown in FIG. 1 is measured. Then, it becomes less than 3%. Further, when the element concentration of Ce at the measurement point Z is measured, it becomes more than 50%. Then, when the elemental concentration of Ce at the measurement point Y is measured, it is 3 to 50%.
Therefore, in the element map obtained by performing STEM-EDS analysis, the mother particles 10 and the cerium-containing coating layer 12 in the composite fine particles of the present invention can be distinguished by a line having a Ce molar concentration of 3%. Further, in the element map obtained by performing STEM-EDS analysis, the cerium-containing coating layer 12 and the child particles 14 in the composite fine particles of the present invention can be distinguished by a line having a Ce molar concentration of 50%.

In the present specification, the STEM-EDS analysis shall be performed by observing at 800,000 times.

Since the composite fine particles of the present invention have the embodiment shown in FIG. 1, when STEM-EDS analysis is performed on the cross section and element mapping is performed, the mother particles (crystalline inorganic oxide) from the outermost shell to the center are obtained. On the way to (main component), it often has at least one layer (consisting of ceria fine particles) having a relatively high concentration of ceria.

<Mother particle>
The mother particles in the composite fine particles of the present invention will be described.
As described above, when the composite fine particles of the present invention are subjected to STEM-EDS analysis and the Ce element concentration (molar concentration) in the cross section of the composite fine particles of the present invention shown in FIG. 1 is measured, the concentration is less than 3%. ..

The substance constituting the mother particle is not particularly limited as long as it is a crystalline inorganic oxide, and may contain a plurality of types of elements.
The crystalline inorganic oxide constituting the mother particle is preferably at least one selected from the group consisting of alumina, titania and zirconia.

As will be described later, since the average particle size of the composite fine particles of the present invention is in the range of 50 to 1000 nm, the average particle size of the mother particles in the composite fine particles of the present invention is inevitably smaller than 1000 nm. The composite fine particles of the present invention in which the average particle size of the mother particles in the composite fine particles of the present invention is in the range of 30 to 700 nm are preferably used.
When the dispersion liquid of the present invention obtained by using the mother particles having an average particle diameter in the range of 30 to 700 nm as a raw material is used as an abrasive, the generation of scratches due to polishing is reduced. When the average particle size of the mother particles is less than 30 nm, the polishing rate tends not to reach a practical level when a dispersion obtained by using such mother particles is used as an abrasive. Further, when the average particle diameter of the mother particles exceeds 700 nm, the polishing rate also tends to not reach a practical level, which tends to reduce the surface accuracy of the substrate to be polished. The mother particles are more preferably those showing monodispersity.

The average particle size of the mother particles in the composite fine particles of the present invention shall be measured as follows.
First, the mother particles are identified by observing at 800,000 times by STEM-EDS analysis and identifying the line where the Ce molar concentration is 3%. Next, the maximum diameter of the mother particle is set as the major axis, the length is measured, and the value is defined as the major axis (DL). In addition, a point that divides the major axis into two equal parts is determined on the major axis, two points where a straight line (minor axis) orthogonal to the point intersects the outer edge of the mother particle are obtained, and the distance between the two points is measured and the minor axis (minor axis). DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the particle diameter of the mother particle.
In this way, the particle diameters of 50 mother particles are measured, and the value obtained by simple averaging them is taken as the average particle diameter.

The shape of the mother particles in the composite fine particles of the present invention is not particularly limited, but specifically, the range of the minor axis / major axis ratio of the parent particles in the composite fine particles of the present invention is 0.2 or more. It is preferably 0 or less.
The minor axis / major axis ratio of the mother particles in the composite fine particles of the present invention shall be measured as follows.
First, the mother particles are identified by observing at 800,000 times by STEM-EDS analysis and identifying the line where the Ce molar concentration is 3%. Next, the maximum diameter of the mother particle is set as the major axis, the length is measured, and the value is defined as the major axis (DL). In addition, a point that divides the long axis into two equal parts on the long axis is determined, two points where a straight line orthogonal to the point intersects the outer edge of the mother particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). .. Then, the ratio (DS / DL) of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the minor axis / major axis ratio of the mother particle. The range of the minor axis / major axis ratio is preferably 0.25 or more and 1.0 or less.

The mother particles are mainly composed of crystalline inorganic oxides, and are usually crystalline inorganic oxide fine particles. As the crystalline inorganic oxide fine particles, those having a non-spherical or spherical shape and having a uniform particle size can be easily prepared, and those having various particle sizes can be prepared, so that they can be preferably used.

It can be confirmed, for example, that the mother particle contains a crystalline inorganic oxide as a main component by the following method. After the dispersion containing the composite fine crystals of the present invention is dried, it is pulverized using a dairy pot to obtain an X-ray diffraction pattern by, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). For example, since it exhibits a crystal phase such as a crystal phase of α-alumina, a crystal phase of anatase-type titania, and a crystal phase of cubic zirconia, it is indicated that the mother particle contains a crystalline inorganic oxide as a main component. You can check. Further, in such a case, it is assumed that the mother particle contains a crystalline inorganic oxide as a main component.
Further, the dispersion liquid of the present invention is dried, embedded in a resin, and then sputter coated with Pt to prepare a cross-sectional sample using a conventionally known focused ion beam (FIB) device. For example, when an FFT pattern is obtained by using a conventionally known TEM device for a prepared cross-sectional sample and using a fast Fourier transform (FFT) analysis, a diffraction pattern corresponding to the crystal structure of the mother particle appears, and the mother particle is crystalline inorganic. It can be confirmed that the main component is an oxide. Further, in such a case, it is assumed that the mother particle contains a crystalline inorganic oxide as a main component.

The mother particle contains a crystalline inorganic oxide as a main component, and may contain other substances such as an amorphous substance (amorphous silica and the like) and a compound other than the oxide.
For example, in the mother particles, the content of each element of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni and Zn (hereinafter, may be referred to as “specific impurity group 1”) is different. It is preferably 5000 ppm or less, preferably 1000 ppm or less, and preferably 100 ppm or less. Further, it is preferably 50 ppm or less, more preferably 25 ppm or less, further preferably 5 ppm or less, and even more preferably 1 ppm or less. Further, the content of each element of U, Th, Cl, NO ₃ , SO ₄ and F (hereinafter, may be referred to as “specific impurity group 2”) in the mother particles is preferably 5 ppm or less. ..

Here, the content of the specific impurity group 1 or the specific impurity group 2 in the mother particles, the composite fine particles of the present invention described later, and the crystalline inorganic oxide fine particles described later means the content rate with respect to the dry amount.
The content ratio with respect to the dry amount is the measurement target object (specific impurity group 1 or specific impurity group 2) with respect to the mass of the solid content contained in the object (mother particles, composite fine particles of the present invention or crystalline inorganic oxide fine particles described later). ) Shall mean the value of the weight ratio (percentage). The impure content of the mother particles is almost the same as the impure content of the crystalline inorganic oxide fine particles if there is no contamination due to contamination or the like.

Generally, the crystalline inorganic oxide fine particles prepared from water glass as a raw material contain the specific impurity group 1 and the specific impurity group 2 derived from the raw water glass in a total of about several thousand ppm.
In the case of a dispersion liquid in which such crystalline inorganic oxide fine particles are dispersed in a solvent, it is possible to reduce the content of the specific impurity group 1 and the specific impurity group 2 by performing an ion exchange treatment. Even in that case, the specific impurity group 1 and the specific impurity group 2 remain in a total of several ppm to several hundred ppm. Therefore, when crystalline inorganic oxide fine particles made from water glass are used, impurities are also reduced by acid treatment or the like.
On the other hand, in the case of a dispersion liquid in which crystalline inorganic oxide fine particles synthesized from alkoxysilane are dispersed in a solvent, the content of each element in the specific impurity group 1 is usually 100 ppm or less. The content is preferably 20 ppm or less, and the content of each element and each anion in the specific impurity group 2 is preferably 20 ppm or less, and more preferably 5 ppm or less.

In the present invention, the contents of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Zn, U, Th, Cl, NO ₃ , SO ₄ and F in the mother particles are respectively. The value is measured and obtained by using the following method.
-Na and K: Atomic absorption spectroscopic analysis-Ag, Ca, Cr, Cu, Fe, Mg, Ni, Zn, U and Th: ICP-MS (inductively coupled plasma emission spectroscopic mass spectrometry)
・ Cl: Potentiometric titration method ・ NO ₃ , SO ₄ and F: Ion chromatograph

The mother particle preferably has a compressive fracture strength of 1.0 to 3.0 MPa. The reason is that the compression fracture strength is in this range, which can prevent the composite fine particles from collapsing during polishing, and further suppress the stress relaxation due to the deformation of the composite fine particles, effectively transmitting the pressure to the substrate. It is possible and a high polishing speed can be obtained.
Here, the compressive fracture strength of the mother particle is measured by the following method.
The dispersion liquid of the present invention was crushed by a sand mill and classified and separated by a centrifuge to obtain a mother particle in which ceria child particles were shed from the mother particle, and the obtained mother particle was subjected to a microcompression test manufactured by Shimadzu Corporation. The compression fracture strength was measured using a machine (MCT-W500).

<Child particles>
In the composite fine particles of the present invention, the child particles containing crystalline ceria as a main component (hereinafter, also referred to as “ceria child particles”) are dispersed in the cerium-containing coating layer arranged on the mother particles.
Further, the mother particles in the composite fine particles of the present invention have a minor axis / major axis ratio in the range of 0.2 to 0.7, and it is preferable that the surface thereof has irregularities. That is, it is preferable to provide a concave portion and a convex portion. In the composite fine particles of the present invention, the child particles mainly have the following forms (a), (b) or (c).
(A) A form in which child particles are bonded to the convex portion of the mother particle via a part of a cerium-containing coating layer.
(B) A form in which child particles are bonded to both the convex portion and the concave portion of the mother particle via a part of the cerium-containing coating layer.
(C) Form in which child particles are bonded to the recesses of the mother particle via a part of the cerium-containing coating layer It is desirable that the forms of (a), (b) or (c) are present at the same time. This is because when the dispersion liquid of the present invention is used as the abrasive grain dispersion liquid for polishing, the mother particles have a step, so that the child particles in the form (a) are first subjected to the substrate to be polished during polishing. Polishing is performed in contact with. Even if the child particles of the form (a) come off, wear, or break due to the polishing pressure, the ceria child particles of the form (b) and (c) then come into contact with the substrate to be polished, and the contact area is reduced. This is because the polishing can be kept high, so that polishing with a stable polishing speed can be performed efficiently.
According to the production method of the present invention described later, it is easy to obtain the dispersion liquid of the present invention containing the composite fine particles of the present invention in which the child particles of the forms (a), (b) or (c) are simultaneously present.

Further, the ceria particles may be laminated in the cerium-containing coating layer, and the shape thereof is not particularly limited to a spherical shape, an elliptical shape, a rectangular shape, etc., and even if the particle size distribution is uniform, it is sharp. Also, there may be a step in the ceria child particles due to the mother particles having protrusions or uneven shapes.
Some of the ceria particles are buried in the cerium-containing coating layer, while others are partially exposed from the cerium-containing coating layer.

As described above, when STEM-EDS analysis was performed on the composite fine particles of the present invention and the Ce element concentration in the cross section of the composite fine particles of the present invention shown in FIG. 1 was measured, the child particles had a Ce molar concentration of more than 50%. Is the part that becomes.

The child particles containing crystalline ceria as a main component in the present invention are dispersed in the cerium-containing coating layer arranged on the mother particles, and the coefficient of variation (CV value) in the particle size distribution of the child particles is 14 to 14. It is 60%. That is, the width of the particle size distribution of the child particles is large. When the dispersion liquid of the present invention having such ceria particles having a large particle size distribution width is used as the abrasive grain dispersion liquid for polishing, the child particles having a large particle size come into contact with the substrate to be polished at the initial stage of polishing. Polishing is performed. Then, even if the child particles come off due to the polishing pressure, or are abraded or broken, the child particles having a small particle diameter then come into contact with the substrate to be polished, so that the contact area can be kept high. Therefore, polishing with a stable polishing rate is performed efficiently.

In the present invention, the coefficient of variation (CV value) in the particle size distribution of the child particles dispersed in the cerium-containing coating layer is 14 to 60%, preferably 17 to 50%, preferably 20 to 40%. It is more preferable to have.

In the present invention, the particle size distribution of the child particles shall be measured as follows.
First, the composite fine particles of the present invention are observed by STEM-EDS analysis at a magnification of 800,000 times, and the child particles are specified by specifying the line where the Ce molar concentration is 50%. Next, the maximum diameter of the child particles is set as the major axis, the length is measured, and the value is defined as the major axis (DL). In addition, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the child particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). .. Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the particle diameter of the child particles.
In this way, the particle size of 100 or more child particles can be measured and the particle size distribution can be obtained.

In the present invention, the coefficient of variation (CV value) in the particle size distribution of the child particles is the standard deviation and the number mean value using the particle size distribution obtained as described above as a population, and then the standard deviation is the number mean value. Divide by and multiply by 100 (ie, standard deviation / number mean x 100).

The average particle size of the child particles is preferably 10 to 25 nm, more preferably 14 to 23 nm.
When the average particle size of the child particles exceeds 25 nm, the precursor particles having such ceria child particles tend to be sintered or condensed after firing and difficult to be crushed in the step 2. Such a ceria-based composite fine particle dispersion is not preferable because it causes scratches on the object to be polished even if it is used for polishing. When the average particle size of the child particles is less than 10 nm, it tends to be difficult to obtain a practically sufficient polishing rate when the particles are also used for polishing.

In the present invention, the average particle size of the child particles means the number average diameter in the particle size distribution obtained as described above.

The child particles may be laminated. That is, a plurality of them may be present on a radial line from the center of the mother particles inside the cerium-containing coating layer.
Further, the child particles may be buried in the cerium-containing coating layer or may be partially exposed to the outside of the cerium-containing coating layer, but when the child particles are buried in the cerium-containing coating layer, cerium It is desirable that the child particles are buried in the cerium-containing coating layer because the surface of the containing coating layer improves storage stability and polishing stability, and the amount of abrasive grains remaining on the substrate after polishing is reduced. ..

The shape of the child particles is not particularly limited. For example, it may be spherical, elliptical, or rectangular. When the dispersion liquid of the present invention is used for polishing purposes and a high polishing rate is to be obtained, the child particles are preferably non-spherical, more preferably rectangular.

The child particles dispersed in the cerium-containing coating layer arranged on the surface of the mother particles may be in a monodispersed state, and may be in a state in which the child particles are laminated (that is, a plurality of child particles in the thickness direction of the cerium-containing coating layer). It may be in a state where the child particles of the above are stacked and exist), or in a state where a plurality of child particles are connected.

In the present invention, the child particles contain crystalline ceria as a main component.
The fact that the child particles contain crystalline ceria as a main component is that, for example, the dispersion liquid of the present invention is dried and then the obtained solid substance is pulverized using a dairy pot to obtain the composite fine particles of the present invention. After that, this is analyzed by X-ray analysis using, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.), and in the obtained X-ray diffraction pattern, the crystalline phase of ceria and crystalline inorganic oxidation It can be confirmed from the fact that the crystal phase of the object is detected. In such a case, it is assumed that the child particles contain crystalline ceria as a main component. The crystal phase of ceria is not particularly limited, and examples thereof include Ceriaite and the like.

The child particles are mainly composed of crystalline ceria (crystalline Ce oxide), and may contain other elements such as elements other than cerium. Further, a hydrous cerium compound may be contained as an auxiliary catalyst for polishing.
However, as described above, when the composite fine particles of the present invention are subjected to X-ray diffraction, the crystal phase of ceria and the crystal phase of the crystalline inorganic oxide are detected. That is, even if a crystal phase other than ceria is contained, its content is low or it is dissolved in the ceria crystal, so that it is out of the detection range by X-ray diffraction.

The average crystallite diameter of the ceria particle is calculated using the full width at half maximum of the maximum peak appearing in the chart obtained by subjecting the composite fine particles of the present invention to X-ray diffraction. Then, for example, the average crystallite diameter of the (111) plane is 10 to 25 nm (full width at half maximum is 0.86 to 0.34 °) and 14 to 23 nm (full width at half maximum is 0.62 to 0.37 °). It is preferably 15 to 22 nm (half width is 0.58 to 0.38), and more preferably. In many cases, the intensity of the peak of the (111) plane is the maximum, but the intensity of the peak of another crystal plane, for example, the (100) plane may be the maximum. In that case, the calculation can be performed in the same manner, and the size of the average crystallite diameter in that case may be the same as the average crystallite diameter of the (111) plane described above.

The method for measuring the average crystallite diameter of the child particles is shown below by taking the case of the (111) plane (near 2θ = 28 degrees) as an example.
First, the composite fine particles of the present invention are pulverized using a mortar, and an X-ray diffraction pattern is obtained, for example, by a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). Then, the full width at half maximum of the peak of the (111) plane near 2θ = 28 degrees in the obtained X-ray diffraction pattern is measured, and the average crystallite diameter can be obtained by the following Scherrer equation.
D = Kλ / βcosθ
D: Average crystallite diameter (Angstrom)
K: Scherrer constant (K = 0.94 in the present invention)
λ: X-ray wavelength (1.5419 angstrom, Cu lamp)
β: Full width at half maximum (rad)
θ: Reflection angle

In the composite fine particles of the present invention, it is preferable that atoms (aluminum, titanium, zirconium, etc.) contained in the crystalline inorganic oxide are solid-dissolved in the crystalline ceria which is the main component of the child particles. In general, solid solution means that two or more kinds of elements (which may be metal or non-metal) are dissolved in each other to form a uniform solid phase as a whole, and a solid solution obtained by solid solution is , It is classified into a substitution type solid solution and an intrusive type solid solution. It is known that the substituted solid solution can easily occur in an atom having a close atomic radius. For example, Zr is known to dissolve in a state where the crystal structure of Cerianite is maintained, and Al is a CeAlO ₃ composition. The perovskite structure is known. Further, it may be an intrusive solid solution.
Conventionally, it is known that when a substrate with a silica film or a glass substrate is polished using ceria particles as abrasive particles, a specifically higher polishing rate is exhibited as compared with the case where other inorganic oxide particles are used. .. One of the reasons why the ceria particles show a particularly high polishing rate with respect to the substrate with a silica film is that the trivalent cerium contained in the ceria particles has a high chemical reactivity with the silica film on the substrate to be polished. It is pointed out to have. Cerium in cerium oxide can have trivalent and tetravalent valences, but high-purity cerium oxide particles used as abrasives for semiconductors are high-purity cerium salts such as cerium carbonate at a high temperature of about 700 ° C. It has undergone a firing process. Therefore, the valence of cerium in the calcined ceria particles is mainly tetravalent, and even if it contains trivalent cerium, its content is not sufficient.
In a preferred embodiment of the composite fine particles of the present invention, it is considered that atoms such as Al in the child particles (ceria fine particles) existing on the outer surface side thereof are infiltrated into the CeO ₂ crystal. Due to the solid dissolution of atoms such as Al, crystal strain of CeO ₂ crystals occurs, so that oxygen defects increase even when fired at high temperature, and a large amount of trivalent cerium chemically active with SiO ₂ is generated, resulting in CeO. As a result of promoting the chemical reactivity of ₂ , it is presumed that the above-mentioned high polishing rate is exhibited. Further, in order to increase the trivalent cerium content, La, Zr or the like may be doped.

The ceria-based composite fine particles of the present invention have the following characteristics because the mother particles are mainly composed of crystalline inorganic oxides.
1) The general shape of the ceria-based composite fine particles can also take a shape such as a cube, a columnar shape, a plate shape, or a needle shape, reflecting the crystal habit of the mother particles. By providing such a shape, when used as an abrasive grain, when the semiconductor substrate to be polished comes into contact with a portion corresponding to the apex of the abrasive grain, the contact area becomes smaller, resulting in stress concentration. Deep cutting and polishing progresses, and a high polishing speed can be obtained. Further, when contact is made at a portion corresponding to the surface or side of the abrasive grain, the contact area is increased, and as a result, larger friction is generated, and a higher polishing speed can be obtained.
2) Since the mother particle has high physical stability and chemical stability, it is possible to prevent contamination of the polishing substrate due to elution of the mother particle component and the impure component contained in the mother particle.
3) By having high rigidity, stress relaxation due to deformation of abrasive grains during polishing is less likely to occur, stress concentration on the substrate progresses, and a higher polishing rate can be obtained. In addition, since particle decay is unlikely to occur, a higher polishing rate can be obtained.

<Cerium-containing coating layer>
The composite fine particles of the present invention have a cerium-containing coating layer on the surface of the mother particles. Then, the child particles are dispersed inside the cerium-containing coating layer.

By adopting such a structure, it is difficult for the child particles to fall off due to the crushing process at the time of manufacturing or the pressure at the time of polishing, and even if some of the child particles are missing, many of the child particles can be dropped. Since it is present in the cerium-containing coating layer without deterioration, the polishing function is not deteriorated.

Further, it is preferable that the cerium-containing coating layer contains silica.
For example, when the mother particles contain crystalline alumina as a main component, the cerium-containing coating layer preferably contains Ce and Si.
Further, for example, when the mother particle contains crystalline titania as a main component, the cerium-containing coating layer preferably contains Ce and Si.
Further, for example, when the mother particle contains crystalline zirconia as a main component, the cerium-containing coating layer preferably contains Ce and Si.

The cerium-containing coating layer preferably contains the same elements as the mother particles.
For example, when the mother particles contain crystalline alumina as a main component, the cerium-containing coating layer preferably contains Al and Ce.
Further, for example, when the mother particle contains crystalline titania as a main component, the cerium-containing coating layer preferably contains Ti and Ce.
Further, for example, when the mother particle contains crystalline zirconia as a main component, the cerium-containing coating layer preferably contains Zr and Ce.

Further, it is preferable that the cerium-containing coating layer further contains silica.
For example, when the mother particle contains crystalline alumina as a main component, the cerium-containing coating layer preferably contains Ce, Al and Si.
Further, for example, when the mother particle contains crystalline titania as a main component, the cerium-containing coating layer preferably contains Ce, Ti and Si.
Further, for example, when the mother particle contains crystalline zirconia as a main component, the cerium-containing coating layer preferably contains Ce, Zr and Si.

As described above, when STEM-EDS analysis was performed on the composite fine particles of the present invention and the elemental concentration of Ce in the cross section of the composite fine particles of the present invention shown in FIG. 1 was measured, the cerium-containing coating layer had a Ce molar concentration of 3. It is a part that becomes ~ 50%.

In the image (TEM image) obtained by observing the composite fine particles of the present invention using a transmission electron microscope, the image of the child particles appears dark on the surface of the mother particle, but the periphery and the outside of the child particles, that is, the present invention. A part of the cerium-containing coating layer also appears on the surface side of the composite fine particles as a relatively thin image. When STEM-EDS analysis was performed on this portion to determine the molar concentration of Al, Ti, Zr, etc. and the Ce molar concentration contained in the crystalline inorganic oxide of the portion, it was confirmed that the molar concentration of Al, etc. was very high. can do.

The average thickness of the cerium-containing coating layer is not particularly limited, but is preferably, for example, 10 to 40 nm, more preferably 12 to 30 nm.
The average thickness of the cerium-containing coating layer can be obtained by drawing a straight line at any 12 points from the center of the mother particle of the composite fine particles of the present invention to the outermost shell and performing STEM-EDS analysis as described above. Measure the distance (distance on the line passing through the center of the mother particle) between the line where the Ce molar concentration specified from the elemental map is 3% and the outermost shell of the composite fine particles of the present invention, and simply average them. It shall be sought. The center of the mother particle is assumed to mean the intersection of the long axis and the short axis described above.

It is considered that the cerium-containing coating layer in the composite fine particles of the present invention promotes the bonding force between the child particles (ceria fine particles containing crystalline ceria as a main component) and the mother particles dispersed and grown in the cerium-containing coating layer during the firing process. .. Therefore, for example, in the step of obtaining the dispersion liquid of the present invention, if necessary, the fired body crushed dispersion obtained by firing is pre-crushed by a dry method, then crushed by a wet method, and further. A ceria-based composite fine particle dispersion can be obtained by performing the centrifugation treatment, and it is considered that the cerium-containing coating layer has an effect of preventing the child particles from coming off from the mother particles. In this case, there is no problem in local shedding of the child particles, and the entire surface of the child particles does not have to be covered with a part of the cerium-containing coating layer. It suffices if the child particles are strong enough not to be separated from the mother particles in the crushing process.
Due to such a structure, when the dispersion liquid of the present invention is used as an abrasive, it is considered that the polishing speed is high and the surface accuracy and scratches are not deteriorated.

Further, in the composite fine particles of the present invention, at least a part of the surface of the child particles is covered with the cerium-containing coating layer. Therefore, when the cerium-containing coating layer contains Si, the outermost surface (outermost) of the composite fine particles of the present invention. The shell) will have a —OH group of silica. Therefore, when used as an abrasive, if the cerium-containing coating layer of the composite fine particles of the present invention contains Si, they repel each other due to the charge due to the -OH group on the surface of the polishing substrate, and as a result, the adhesion to the surface of the polishing substrate is small. It is considered to be.

In general, ceria has a different potential from silica, a polishing substrate, and a polishing pad, and the negative zeta potential decreases as the pH shifts from alkaline to near neutral, and the opposite positive potential in the weakly acidic region. have. Therefore, in the acidic pH at the time of polishing, ceria adheres to the polishing base material or the polishing pad due to the difference in the magnitude of the potential or the difference in the polarity, and tends to remain on the polishing base material or the polishing pad. On the other hand, when the cerium-containing coating layer of the composite fine particles of the present invention contains Si, silica is present in the outermost shell as described above, and the potential becomes a negative charge due to silica, so that the pH is alkaline. It maintains a negative potential from to acidic to acidic, and as a result, it is unlikely that abrasive particles will remain on the polishing substrate or polishing pad. When crushing while maintaining pH 8.6 to 10.8 during the crushing process of step 2 in the production method of the present invention, when silica is used as a part of the raw material in step 1, silica on the surface of the composite fine particles of the present invention Part of (silica in the cerium-containing coating layer) dissolves. If the dispersion liquid of the present invention produced under the above conditions is adjusted to pH <7 when applied to a polishing application, the dissolved silica is deposited on the composite fine particles (abrasive particles) of the present invention. The surface will have a negative potential. When the potential is low, silicic acid may be added to appropriately reinforce the cerium-containing coating layer.

In order to adjust the potential of the child particles, it is possible to adjust the potential with a polymer organic substance such as polyacrylic acid, but when the cerium-containing coating layer is the composite fine particles of the present invention containing Si, silica softly adhered to the surface. Adjusts the potential, so the use of organic matter is reduced, and organic matter-induced defects (residue of organic matter, etc.) on the substrate are less likely to occur. Further, since the silica attached to this soft has not undergone a firing step, it is a low-density, soft and easily soluble silica layer. This easily soluble silica layer has an adhesive action with the substrate, and the effect of improving the polishing rate is recognized. This easily soluble silica layer can be confirmed by keeping the dispersion liquid of the present invention at pH 9 and measuring the silica concentration in the solution separated into solid and liquid.
In the dispersion liquid of the present invention in which the cerium-containing coating layer contains the composite fine particles of the present invention containing Si, there are various aspects in which silica is present, and the composite fine particles of the present invention are not formed and are dispersed in a solvent. Alternatively, it may be dissolved or exist in a state of being attached to the surface of the composite fine particles of the present invention.

<Composite fine particles of the present invention>
The composite fine particles of the present invention will be described.
As described above, the composite fine particles of the present invention are [1] the ceria-based composite fine particles are dispersed inside the mother particles, the cerium-containing coating layer on the surface of the mother particles, and the cerium-containing coating layer. The mother particles are mainly composed of crystalline inorganic oxides, and the child particles are mainly composed of crystalline ceria. [2] Fluctuation coefficient (CV value) in the particle size distribution of the child particles. ) Is 14 to 60%. [4] When the ceria-based composite fine particles are subjected to X-ray diffraction, the crystal phase of ceria and the crystal phase of the crystalline inorganic oxide are detected, and [5] the ceria-based composite particles are detected. The fine particles have an average crystallite diameter of 10 to 25 nm, which is measured by subjecting them to X-ray diffraction.
Further, the composite fine particles of the present invention are further characterized in that [3] the ceria-based composite fine particles have a mass ratio of 100: 11 to 316 between components other than ceria and ceria, and have a minor axis / major axis. Ceria-based composite fine particles having a ratio in the range of 0.2 or more and 1.0 or less and having an average particle diameter of 50 to 1000 nm.

In the composite fine particles of the present invention, the mass ratio of the component other than ceria to ceria (CeO ₂ ) is 100: 11 to 316, preferably 100: 30 to 230, and preferably 100: 30 to 150. It is more preferably 100:60 to 100:120. The mass ratio of the components other than ceria to ceria is considered to be approximately the same as the mass ratio of the mother particle and the child particles. If the amount of child particles is too small with respect to the mother particles, the mother particles or the composite fine particles may be bonded to each other to generate coarse particles. In this case, the polishing agent (polishing slurry) containing the dispersion liquid of the present invention may cause defects (decrease in surface accuracy such as increase in scratches) on the surface of the polishing base material. Moreover, if the amount of ceria is too large for components other than ceria, not only the cost becomes high, but also the resource risk increases. Further, the fusion of the particles progresses. As a result, the roughness of the surface of the substrate increases (deterioration of the surface roughness Ra), scratches increase, free ceria remains on the substrate, and the polishing equipment adheres to the waste liquid piping, etc. Easy to get along with.
When silica is contained in the component other than ceria when calculating the mass ratio of the component other than ceria and ceria (CeO ₂ ), the silica is all silica (SiO) contained in the composite fine particles of the present invention. ₂ ) means. Therefore, it means the total amount of the silica component constituting the mother particle, the silica component contained in the cerium-containing coating layer arranged on the surface of the mother particle, and the silica component that can be contained in the child particles.

The content (% by mass) of components other than ceria and ceria (CeO ₂ ) in the composite fine particles of the present invention is first determined by weighing the solid content concentration of the dispersion liquid of the present invention by burning at 1000 ° C.
Next, the content (mass%) of cerium (Ce) contained in a predetermined amount of the composite fine particles of the present invention is determined by ICP plasma emission spectrometry and converted into an oxide mass% (CeO ₂ % by mass, etc.). Then, components other than CeO ₂ constituting the composite fine particles of the present invention can be calculated.
In the production method of the present invention, the mass ratio of the components other than ceria to the ceria is calculated from the amount of the substance that can constitute the mother particle and the ceria source substance that were added when preparing the dispersion of the present invention. You can also do it. This can be applied when the process is not such that the substances that can form ceria or mother particles are dissolved and removed. In such cases, the amount of substances that can form ceria or mother particles and the analytical values are good. Show a match.

The composite fine particles of the present invention have a cerium-containing coating layer formed on the surface of the mother particles, are firmly bonded to each other, and particulate crystalline ceria (child particles) are dispersed in the cerium-containing coating layer. Has a surface shape of.

The minor axis / major axis ratio of the composite fine particles of the present invention is 0.2 to 1.0.
Since the minor axis / major axis ratio of the composite fine particles of the present invention is in a specific range, when the dispersion liquid of the present invention is used for polishing, it is possible to improve the polishing rate of the substrate to be polished, and at the same time, on the substrate to be polished. The surface roughness of the surface can be reduced.

Here, the minor axis / major axis ratio shall be measured by the following image analysis method.
First, in a photographic projection drawing obtained by taking a photograph of the composite fine particles of the present invention at a magnification of 300,000 times (or 500,000 times) with a transmission electron microscope, the maximum diameter of the particles is set as the major axis and the length is measured. Then, the value is taken as the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). From this, the minor axis / major axis ratio (DS / DL) is obtained. Then, in any 50 particles observed in the photographic projection drawing, the minor axis / major axis ratio (DS / DL) of each composite fine particle is obtained, and the average value is taken as the value of the minor axis / major axis ratio of the composite fine particles. did.

As described above, the shape of the composite fine particles of the present invention needs to have a minor axis / major axis ratio in the range of 0.2 to 1.0. As long as it is within the range of the minor axis / major axis ratio, the composite fine particles of the present invention may be a "particle connected type" in which a plurality of particles are bonded, or a "single particle type" composed of independent particles. It doesn't matter. Of these, the particle connection type is more preferable because the contact area with the substrate can be kept high and the high polishing speed can be exhibited. In the particle-connected type, more specifically, two or more mother particles are partially bonded to each other, and the number of connected particles is preferably 3 or less. In the particle-connected composite fine particles, at least one (preferably both) of the mother particles is welded at their contact points, or has a history of solidification due to the intervention of ceria, so that they are firmly bonded to each other. Conceivable. Here, there is a case where a cerium-containing coating layer is formed on the surface of the mother particles after they are bonded to each other, and a case where a cerium-containing coating layer is formed on the surface of the mother particles and then bonded to another particle. However, it is a particle-connected type.
If it is a connected type, a large contact area with the substrate can be taken, so that polishing energy can be efficiently transmitted to the substrate. Therefore, the polishing speed is high.
The particle-connected particles mean particles (condensed particles) in which chemical bonds that cannot be redispersed are generated between the particles and the particles are connected. Further, the single particle means a particle in which a plurality of particles are not connected and is not aggregated regardless of the morphology of the particles.

When applied to polishing applications, for example, the composite fine particles of the present invention are preferably of a particle-connected type and have a minor axis / major axis ratio of 0.2 to 1.0 measured by an image analysis method. Also, 0.65 or less is more preferable.
Here, in the particle-connected type, the minor axis / major axis ratio measured by the image analysis method is usually 0.2 to 1.0.
The shape of the composite fine particles of the present invention is not particularly limited, and may be a particle-connected particle or a single particle type (non-connected particle), and is usually a mixture of both. ..

When the dispersion liquid of the present invention is applied to a polishing application, a composite having a minor axis / major axis ratio in the range of 0.2 to 1.0 in all the composite fine particles of the present invention contained in the dispersion liquid of the present invention. The number ratio of the fine particles is preferably 60% or more, and more preferably 70% or more.

The number of coarse particles of 0.51 μm or more that can be contained in the dispersion liquid of the present invention is preferably 100 million / cc or less in terms of dryness. The number of coarse particles is preferably 100 million particles / cc or less, and more preferably 80 million particles / cc or less. Coarse particles of 0.51 μm or more may cause polishing scratches and further deteriorate the surface roughness of the polishing substrate. Normally, when the polishing speed is high, the polishing speed is high, but on the other hand, polishing scratches occur frequently and the surface roughness of the substrate tends to deteriorate. However, when the composite fine particles of the present invention are of the particle-connected type, a high polishing rate can be obtained, while when the number of coarse particles of 0.51 μm or more is 100 million / cc or less, there are few polishing scratches and the surface surface. Roughness can be kept low.

The method for measuring the number of coarse particles that can be contained in the dispersion liquid of the present invention is as follows.
After diluting and adjusting the sample to 0.1% by mass with pure water, 5 ml is collected and injected into a conventionally known coarse particle number measuring device. Then, the number of coarse particles of 0.51 μm or more is obtained. This measurement is performed three times to obtain a simple average value, and the value is multiplied by 1000 to obtain a value having a coarse particle number of 0.51 μm or more.

The composite fine particles of the present invention preferably have a specific surface area of 4 to 100 m ² / g, more preferably 20 to 70 m ² / g.

Here, a method for measuring the specific surface area (BET specific surface area) will be described.
First, a dried sample (0.2 g) is placed in a measurement cell, degassed at 250 ° C. for 40 minutes in a nitrogen gas stream, and then the sample is mixed with 30% by volume of nitrogen and 70% by volume of helium. Keep the liquid nitrogen temperature in the air stream and allow nitrogen to equilibrate and adsorb to the sample. Next, the temperature of the sample is gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that period is detected, and the specific surface area of the sample is measured by a calibration curve prepared in advance.
Such a BET specific surface area measuring method (nitrogen adsorption method) can be performed, for example, by using a conventionally known surface area measuring device.
In the present invention, the specific surface area means a value obtained by measuring by such a method unless otherwise specified.

The average particle size of the composite fine particles of the present invention is preferably 50 to 1000 nm, more preferably 100 to 300 nm. When the average particle size of the composite fine particles of the present invention is in the range of 50 to 1000 nm, the polishing rate becomes high when applied as an abrasive, which is preferable.
The average particle size of the composite fine particles of the present invention means the number average value of the average particle size measured by the image analysis method.
The method of measuring the average particle size by the image analysis method will be described. In a photographic projection drawing obtained by taking a photograph of the composite fine particles of the present invention at a magnification of 300,000 times (or 500,000 times) with a transmission electron microscope, the maximum diameter of the particles is set as the major axis, and the length thereof is measured. , Let the value be the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the average particle diameter of the composite fine particles.
In this way, the average particle size of 50 or more composite particles is measured, and the average number of them is calculated.

In the composite fine particles of the present invention, the content of each element in the specific impurity group 1 is preferably 100 ppm or less. Further, it is preferably 50 ppm or less, more preferably 25 ppm or less, further preferably 5 ppm or less, and even more preferably 1 ppm or less.
Further, the content of each element of the specific impurity group 2 in the composite fine particles of the present invention is preferably 5 ppm or less. The method for reducing the element content of each of the specific impurity group 1 and the specific impurity group 2 in the composite fine particles of the present invention is as described above.
The content of each element of the specific impurity group 1 and the specific impurity group 2 in the composite fine particles of the present invention is the case where the specific impurity group 1 and the specific impurity group 2 contained in the mother particles are measured. It can be measured by the same method as.

<Dispersion liquid of the present invention>
The dispersion liquid of the present invention will be described.
The dispersion liquid of the present invention is one in which the composite fine particles of the present invention as described above are dispersed in a dispersion solvent.

The dispersion liquid of the present invention contains water and / or an organic solvent as the dispersion solvent. As the dispersion solvent, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. Further, the dispersion liquid of the present invention is polished by adding one or more selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster and a pH buffer as an additive for controlling the polishing performance. It is suitably used as a slurry.

Further, as the dispersion solvent provided with the dispersion liquid of the present invention, alcohols such as methanol, ethanol, isopropanol, n-butanol, methylisocarbinol and the like; acetone, 2-butanone, ethyl amylketone, diacetone alcohol, isophorone and cyclohexanone. Ketones such as; amides such as N, N-dimethylformamide, N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran. Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate; acetic acid Ethers such as methyl, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethylene carbonate; aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as hexane, heptane, isooctane and cyclohexane; chloride Halogenated hydrocarbons such as methylene, 1,2-dichloroethane, dichloropropane, chlorbenzene; sulfoxides such as dimethylsulfoxide; organics such as pyrrolidones such as N-methyl-2-pyrrolidone, N-octyl-2-pyrrolidone A solvent can be used. These may be mixed with water and used.

The solid content concentration contained in the dispersion liquid of the present invention is preferably in the range of 0.3 to 50% by mass.

In the dispersion liquid of the present invention, the ratio (V) of the flow potential change amount (ΔPCD) represented by the following formula (1) and the addition amount (V) of the cationic colloid titration solution in the knick when the cationic colloid titration is performed. It is preferable that a flow potential curve having a ΔPCD / V) of −250.0 to −5.0 can be obtained.
ΔPCD / V = (IC) / V ... Equation (1)
C: Flow potential (mV) in the knick
I: Flow potential (mV) at the start point of the flow potential curve
V: Addition amount (ml) of the cationic colloid titration solution in the knick

Here, the cationic colloid titration is performed by adding the cationic colloid titration solution to 80 g of the dispersion liquid of the present invention in which the solid content concentration is adjusted to 1% by mass. A 0.001N polydiallyl dimethylammonium chloride solution is used as the cationic colloid titration solution.

The flow potential curve obtained by this cation colloid titration is a graph in which the addition amount (ml) of the cation titration solution is taken on the X-axis and the flow potential (mV) of the dispersion liquid of the present invention is taken on the Y-axis.
The knick is a point (inflection point) where the flow potential changes rapidly in the flow potential curve obtained by cationic colloid titration. Then, the flow potential at the inflection is C (mV), and the amount of the cationic colloid titration solution added at the inflection is V (ml).
The starting point of the flow potential curve is the flow potential in the dispersion liquid of the present invention before titration. Specifically, the starting point is the point where the addition amount of the cationic colloid titration solution is 0. Let the flow potential at this starting point be I (mV).

When the above value of ΔPCD / V is −250.0 to −5.0, when the dispersion liquid of the present invention is used as an abrasive, the polishing speed of the abrasive is further improved. This ΔPCD / V reflects the degree of coating of the child particles by the cerium-containing coating layer on the surface of the composite fine particles of the present invention and / or the degree of exposure of the child particles on the surface of the composite fine particles or the presence of a mother particle component that is easily desorbed. it is conceivable that. The present inventor estimates that when the value of ΔPCD / V is within the above range, the child particles are less likely to be desorbed during crushing by a wet method and the polishing rate is high. On the contrary, when the value of ΔPCD / V is larger than -250.0, the surface of the composite fine particles is entirely covered with the cerium-containing coating layer, so that the child particles are unlikely to fall off in the crushing step, but polishing. Sometimes the cerium-containing coating layer is difficult to remove and the polishing rate decreases. On the other hand, if the absolute value is smaller than -5.0, it is considered that dropout is likely to occur. Within the above range, the present inventor presumes that the surface of the child particles is appropriately exposed during polishing, the child particles are less likely to fall off, and the polishing speed is further improved. ΔPCD / V is more preferably -230.0 to −5.0, and even more preferably -230.0 to -10.0.

When the pH value of the dispersion of the present invention is in the range of 3 to 8, the flow potential before starting the cationic colloid titration, that is, when the titration amount is zero, becomes a negative potential. Is preferable. This is because when the flow potential maintains a negative potential, it is difficult for abrasive grains (ceria-based composite fine particles) to remain on the polishing substrate, which also exhibits a negative surface potential.

<Manufacturing method of the present invention>
The manufacturing method of the present invention will be described.
The manufacturing method of the present invention includes steps 1 to 3 described below.

<Step 1>
In step 1, a crystalline inorganic oxide fine particle dispersion liquid in which the crystalline inorganic oxide fine particles are dispersed in a solvent is prepared.
In this specification, "step 1" may be referred to as "blending step".

The embodiment of the crystalline inorganic oxide fine particles used in step 1 is not particularly limited, but is more preferable as long as it has the same average particle size and shape as the above-mentioned mother particles. Further, the crystalline inorganic oxide fine particles are mainly composed of the crystalline inorganic oxide, like the above-mentioned mother particles. Here, the definition of the principal component is the same as that of the mother particle. That is, after the crystalline inorganic oxide fine particle dispersion is dried, it is pulverized using a dairy pot, and an X-ray diffraction pattern is obtained by, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). And, when only the peak of the crystalline inorganic oxide appears, it means that it is the main component.

The average particle size of the crystalline inorganic oxide fine particles in the crystalline inorganic oxide fine particle dispersion used as a raw material in step 1 is the average of the ceria-based composite fine particles in the ceria-based composite fine particle dispersion obtained by the production method of the present invention. Those smaller than the particle size are used. Preferably, crystalline inorganic oxide fine particles in the range of 15 nm or more and less than 350 nm are used.
The average particle size of the crystalline inorganic oxide fine particles in this crystalline inorganic oxide fine particle dispersion is taken as the average particle size based on the values calculated based on the photographic projections obtained by taking photographs using a transmission electron microscope. can do. The specific measuring method is the same as the above-mentioned measuring method of the average particle size in the composite fine particles of the present invention.

The minor axis / major axis ratio of the crystalline inorganic oxide fine particles in the crystalline inorganic oxide fine particle dispersion used as a raw material in step 1 must be 0.1 or more and less than 1.0. desirable. Further, as a more desirable range, a range of a minor axis / major axis ratio of 0.2 or more and 0.7 or less can be mentioned.
The minor axis / major axis ratio of the crystalline inorganic oxide fine particles in this crystalline inorganic oxide fine particle dispersion is the minor axis based on the values calculated based on the photographic projections obtained by taking photographs using a transmission electron microscope. / Can be a major axis ratio. The specific measuring method is the same as the above-mentioned measuring method of the minor axis / major axis ratio in the composite fine particles of the present invention.

When the dispersion liquid of the present invention to be applied to polishing of semiconductor devices and the like is to be prepared by the production method of the present invention, crystalline inorganic oxidation produced by hydrolysis of a metal alkoxide as a crystalline inorganic oxide fine particle dispersion liquid is used. It is preferable to use a crystalline inorganic oxide fine particle dispersion liquid in which fine particles are dispersed in a solvent, but other conventionally known crystalline inorganic oxide fine particle dispersion liquid may be used as a raw material.
Specifically, for example, as the crystalline inorganic oxide fine particles in the crystalline inorganic oxide fine particle dispersion liquid as a raw material, those satisfying the following conditions (a) and (b) are preferably used.
(A) The contents of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni and Zn are 100 ppm or less, respectively.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are 5 ppm or less, respectively.

Further, as the crystalline inorganic oxide fine particles, those having an appropriate reactivity with cerium (dissolved weight of the crystalline inorganic oxide fine particles per weight of ceria) are preferably used. In the crystalline inorganic oxide fine particles, by adding a metal salt of cerium in the compounding step of step 1 in the production method of the present invention, a part of the crystalline inorganic oxide is dissolved by cerium hydroxide or the like, and the crystalline inorganic oxide is formed. The size of the oxide fine particles is reduced, and a precursor of a cerium-containing coating layer containing fine crystals of cerium is formed on the surface of the dissolved crystalline inorganic oxide fine particles. At this time, when the crystalline inorganic oxide fine particles are made of a crystalline inorganic oxide having high reactivity with cerium, the precursor of the cerium-containing coating layer becomes thick, and the cerium-containing coating layer generated by firing becomes thick. This is because the proportion of crystalline inorganic oxide in the layer becomes excessively high, which makes crushing difficult in the crushing step. Further, when the crystalline inorganic oxide fine particles are made of a crystalline inorganic oxide having extremely low reactivity with cerium, the cerium-containing coating layer is not sufficiently formed, and the ceria particles are likely to fall off. When the reactivity with cerium is appropriate, the dissolution of excess crystalline inorganic oxide is suppressed, the cerium-containing coating layer becomes an appropriate thickness and prevents the falling off of child particles, and the strength is the strength between the composite fine particles. It is desirable because it is considered to be larger than the above and it is easy to crush.

In step 1, the crystalline inorganic oxide fine particle dispersion liquid in which the crystalline inorganic oxide fine particles are dispersed in a solvent is stirred, the temperature is 0 to 20 ° C., the pH range is 7.0 to 9.0, and the redox potential. By continuously or intermittently adding a metal salt of cerium to the metal salt of cerium to neutralize the metal salt of cerium, a precursor particle dispersion liquid containing the precursor particles is obtained.

Here, in addition to the metal salt of cerium, it is preferable to add a component containing silicon.
As a typical example of the component containing silicon, a compound containing a silicon atom such as a silicate can be mentioned. In addition, alkoxysilanes such as tetraethoxysilane can be mentioned as components containing silicon.
While stirring the crystalline inorganic oxide fine particle dispersion, maintaining the temperature at 0 to 20 ° C., the pH at 7.0 to 9.0, and the redox potential at 50 to 500 mV, the metal salt of cerium and silicon are here. When the component containing the above is continuously or intermittently added, the composite fine particles of the present invention in which at least a part of the cerium-containing coating layer is made of silica can be obtained.

When the crystalline inorganic oxide fine particles have protrusions, the temperature of the crystalline inorganic oxide fine particle dispersion liquid when adding a metal salt of cerium (preferably a component further containing silicon) is 3 to 20 ° C. Is preferable.

The dispersion medium in the crystalline inorganic oxide fine particle dispersion liquid preferably contains water, and it is preferable to use an aqueous-based crystalline inorganic oxide fine particle dispersion liquid (water sol).

The solid content concentration in the crystalline inorganic oxide fine particle dispersion is preferably 1 to 40% by mass on an oxide conversion basis. If the solid content concentration is too low, the concentration of the inorganic oxide in the manufacturing process may be low and the productivity may be deteriorated.

In the production method of the present invention, for example, when the reaction temperature between the crystalline inorganic oxide fine particles and the metal salt of cerium (preferably a component further containing silicon) in step 1 is 40 to 50 ° C., ceria and the inorganic oxide are used. The reactivity of the crystallized inorganic oxide fine particles is increased, and the dissolution of the crystalline inorganic oxide fine particles is promoted. As a result, the particle size of the CeO ₂ ultrafine particles in the precursor particles obtained by drying in the intermediate step of step 2 is less than 2.5 nm. This means that when the inorganic oxide reacts with ceria in the liquid phase in the high temperature region, the inorganic oxide inhibits the particle growth of ceria, so that the average particle size of the dried ceria becomes smaller than 2.5 nm. Is shown.
Even with such precursor particles, it is possible to set the average crystallite diameter of the ceria child particles to 10 nm or more by setting the firing temperature to 1200 ° C. or higher, but in this case, the cerium-containing coating is used. A film of an inorganic oxide is formed without forming a layer, and the tendency of the film of the inorganic oxide to firmly coat the ceria particles is increased, which causes a problem in that crushing becomes difficult. Therefore, by keeping the reaction temperature at 0 to 20 ° C and appropriately suppressing the reaction between the inorganic oxide and ceria in the liquid phase, the average crystallite diameter of the CeO ₂ ultrafine particles in the dried precursor particles is 2.5 nm. The above is possible, and the particles are easy to crush. Further, since the average crystallite diameter after drying is large, the firing temperature for setting the average crystallite diameter of the ceria particles to 10 nm or more can be lowered, and the thickness of the cerium-containing coating layer formed by firing becomes excessive. It does not thicken and can be easily crushed.

Further, impurities are extracted with a cation exchange resin or an anion exchange resin, a mineral acid, an organic acid, etc., and an ultrafiltration membrane or the like is used to deionize the crystalline inorganic oxide fine particle dispersion as necessary. Processing can be performed. A crystalline inorganic oxide fine particle dispersion liquid from which impurity ions and the like have been removed by a deionization treatment is more preferable because it is easy to form a hydroxide containing an inorganic oxide on the surface. The deionization treatment is not limited to these.

In step 1, the crystalline inorganic oxide fine particle dispersion as described above is stirred, and the temperature is maintained at 0 to 20 ° C., the pH range is 7.0 to 9.0, and the redox potential is maintained at 50 to 500 mV. A metal salt of cerium (preferably a component further containing silicon) is continuously or intermittently added thereto. When the redox potential is low, crystals such as rods are formed, so that they are difficult to deposit on the crystalline inorganic oxide fine particles.
Furthermore, if the redox potential is not adjusted to a predetermined range, the CeO ₂ ultrafine particles produced in the compounding step tend to be difficult to crystallize, and the uncrystallized CeO ₂ ultrafine particles can be crystallized by heating and aging after the compounding. Crystallization is not promoted. Therefore, in order to crystallize to a predetermined size in the firing in step 2, firing at a high temperature is required, which makes crushing difficult.

The type of the metal salt of cerium is not limited, but chloride, nitrate, sulfate, acetate, carbonate, metal alkoxide and the like of cerium can be used. Specific examples thereof include first cerium nitrate, cerium carbonate, first cerium sulfate, and first cerium chloride. Of these, trivalent cerium salts such as primary cerium nitrate, primary cerium chloride, and cerium carbonate are preferable. Crystalline cerium oxide, cerium hydroxide, etc. are generated from the solution that becomes supersaturated at the same time as neutralization, and they are rapidly aggregated and deposited on the crystalline inorganic oxide fine particles, and finally the CeO ₂ ultrafine particles are monodispersed. Because it is formed by. Further, the trivalent cerium salt appropriately reacts with the crystalline inorganic oxide fine particles, and a cerium-containing coating layer is likely to be formed. Further, trivalent cerium having high reactivity with the silica film formed on the polishing substrate is easily formed in the ceria crystal, which is preferable. However, sulfate ions, chloride ions, nitrate ions and the like contained in these metal salts are corrosive. Therefore, if desired, it is necessary to wash the mixture in a post-process after preparation and remove it to 5 ppm or less. On the other hand, the carbonate is released as carbon dioxide gas during preparation, and the alkoxide is decomposed into an alcohol, so that it can be preferably used.

The amount of the metal salt of cerium added to the crystalline inorganic oxide fine particle dispersion is such that the mass ratio of the component other than ceria to the ceria in the obtained ceria-based composite fine particles is the same as in the case of the above-mentioned composite fine particles of the present invention. , 100: 11 to 316.

After adding the metal salt of cerium to the crystalline inorganic oxide fine particle dispersion, the temperature at the time of stirring is preferably 0 to 20 ° C, more preferably 3 to 20 ° C, and 3 to 18 ° C. It is more preferable to have. If this temperature is too low, the reactivity between the ceria and the inorganic oxide is lowered, and the solubility of the inorganic oxide is significantly lowered, so that the crystallization of the ceria is not controlled. As a result, coarse crystalline oxide of ceria is generated, abnormal growth of CeO ₂ ultrafine particles occurs on the surface of the crystalline inorganic oxide fine particles, and it becomes difficult to be crushed after firing, or the inorganic oxide made of a cerium compound is used. Since the amount of dissolved in the cerium is reduced, the amount of inorganic oxide supplied to the cerium-containing coating layer is reduced. For this reason, the inorganic oxide that serves as a binder between the mother particle and the ceria child particle is insufficient (the inorganic oxide laminated on the mother particle is insufficient), and the immobilization of the ceria child particle to the mother particle is unlikely to occur. It is possible that it will be. On the contrary, if this temperature is too high, the solubility of the inorganic oxide may be remarkably increased and the formation of crystalline ceria oxide may be suppressed. There is a possibility that it cannot be crushed, and moreover, scales and the like are likely to occur on the wall surface of the reactor, which is not preferable. Further, the crystalline inorganic oxide fine particles are preferably those that are difficult to dissolve in a cerium compound (neutralized product of a cerium salt). In the case of crystalline inorganic oxide fine particles that are easily dissolved, the crystal growth of ceria is suppressed by the inorganic oxide, and the particle size of the CeO ₂ ultrafine particles at the compounding stage is less than 2.5 nm.
If the particle size of the CeO ₂ ultrafine particles at the compounding stage is less than 2.5 nm, it is necessary to raise the firing temperature in order to make the ceria particle size after firing 10 nm or more. In that case, the cerium-containing coating layer May cover the mother particles tightly, making crushing difficult. Crystalline inorganic oxide fine particles that are easily dissolved can be suppressed in solubility when used as a raw material after being dried at 100 ° C. or higher.

Further, the time for stirring the crystalline inorganic oxide fine particle dispersion liquid after adding the metal salt of cerium is preferably 0.5 to 24 hours, more preferably 0.5 to 18 hours. If this time is too short, the CeO ₂ ultrafine particles aggregate and become difficult to react with the inorganic oxide on the surface of the crystalline inorganic oxide fine particles, which is preferable in that composite fine particles that are difficult to be crushed tend to be formed. do not have. On the contrary, even if this time is too long, the formation of the CeO ₂ ultrafine particle-containing layer is uneconomical because the reaction does not proceed any further. After the addition of the cerium metal salt, it may be aged at 0 to 80 ° C., if desired. This is because the aging has the effect of accelerating the reaction of the cerium compound and at the same time adhering the liberated CeO ₂ ultrafine particles on the crystalline inorganic oxide fine particles without adhering to the crystalline inorganic oxide fine particles.

Further, the pH range of the crystalline inorganic oxide fine particle dispersion liquid when a metal salt of cerium is added to the crystalline inorganic oxide fine particle dispersion liquid and stirred is set to 7.0 to 9.0, but 7.6 to 9.0. It is preferably 8.6. At this time, it is preferable to add an alkali or the like to adjust the pH. As an example of such an alkali, a known alkali can be used. Specific examples thereof include, but are not limited to, an aqueous solution of ammonia, an alkali hydroxide, an alkaline earth metal, and an aqueous solution of amines.

Further, a metal salt of cerium (preferably a component further containing silicon) is added to the crystalline inorganic oxide fine particle dispersion, and the redox potential of the fine particle dispersion at the time of stirring is adjusted to 50 to 500 mV. The redox potential is preferably 100 to 300 mV. This is because when a trivalent cerium metal salt is used as a raw material, the acid reduction potential of the fine particle dispersion liquid decreases during preparation. Further, by keeping the redox potential in this range, the crystallization of the produced CeO ₂ ultrafine particles is promoted. When the redox potential is 50 mV or less or negative, the cerium compound may not be deposited on the surface of the crystalline inorganic oxide fine particles, and plate-shaped or rod-shaped ceria single particles or composite ceria particles may be generated. Further, the reactivity of cerium hydroxide or the like with respect to the crystalline inorganic oxide fine particles is lowered, and the CeO ₂ ultrafine particle-containing layer is not formed. Even if it is formed, the proportion of the inorganic oxide in the CeO ₂ ultrafine particle layer is extremely high. It gets lower. Therefore, the cerium-containing coating layer containing the ceria particles is not formed after firing, and the ceria particles tend to be exposed and arranged on the surface of the mother particles of the inorganic oxide.
Examples of the method of keeping the redox potential within the above range include a method of adding an oxidizing agent such as hydrogen peroxide and a method of blowing air, oxygen and ozone. If these methods are not performed, the redox potential tends to be negative or 50 mV or less.

By such step 1, a dispersion liquid (precursor particle dispersion liquid) containing particles (precursor particles) which are precursors of the composite fine particles of the present invention can be obtained. In this step, it is possible to obtain particles having an average crystallite diameter of 2.5 nm or more and less than 10 nm of CeO ₂ ultrafine particles contained in the precursor particles. If the reactivity between the inorganic oxide and ceria is too high, the average crystallite diameter of the CeO ₂ ultrafine particles contained in the precursor particles tends to be less than 2.5 nm. It is necessary to bake at an excessively high temperature. As a result, the adhesion between the particles becomes strong, which may make crushing difficult.

As described above, in step 1, the crystalline inorganic oxide fine particle dispersion is stirred, and the temperature is maintained at 0 to 20 ° C., the pH is 7.0 to 9.0, and the redox potential is 50 to 500 mV. The metal salt of cerium (preferably a component further containing silicon) is continuously or intermittently added thereto, after which the temperature is over 20 ° C. and 98 ° C. or lower, the pH is 7.0 to 9.0, and the redox is redox. It is preferable to continuously or intermittently add the metal salt of the cerium (preferably a component further containing silicon) to the potential while maintaining the potential at 50 to 500 mV to obtain the precursor particle dispersion.
That is, in step 1, the treatment is carried out at a temperature of 0 to 20 ° C., and then the treatment is carried out by changing the temperature to over 20 ° C. and 98 ° C. or lower to obtain the precursor particle dispersion liquid.
This is because when such step 1 is performed, it is easy to obtain the dispersion liquid of the present invention containing the composite fine particles of the present invention in which the coefficient of variation in the particle size distribution of the child particles is a suitable value.
The pH and redox potential in the case of treatment at a temperature of more than 20 ° C. and 98 ° C. or lower, the adjustment method and the like are the same as in the case of treatment at a temperature of 0 to 20 ° C.

On the contrary, it is preferable to obtain the precursor particle dispersion liquid by performing the treatment at a temperature of more than 20 ° C. and 98 ° C. or lower before performing the treatment at a temperature of 0 to 20 ° C. That is, the cerium is here while stirring the crystalline inorganic oxide fine particle dispersion, maintaining the temperature above 20 ° C. and 98 ° C. or lower, the pH at 7.0 to 9.0, and the redox potential at 50 to 500 mV. Metal salt (preferably a component further containing silicon) is added continuously or intermittently, and then the temperature is maintained at 0 to 20 ° C., the pH is maintained at 7.0 to 9.0, and the redox potential is maintained at 50 to 500 mV. However, it is preferable to continuously or intermittently add the metal salt of the cerium (preferably a component further containing silicon) to the precursor particle dispersion liquid.
This is because when such step 1 is performed, it is easy to obtain the dispersion liquid of the present invention containing the composite fine particles of the present invention in which the coefficient of variation in the particle size distribution of the child particles is a suitable value.
The pH and redox potential in the case of treatment at a temperature of more than 20 ° C. and 98 ° C. or lower, the adjustment method and the like are the same as in the case of treatment at a temperature of 0 to 20 ° C.
Even when the compound is prepared by changing the temperature during the compounding as described above, the composite fine particles have the same formation mechanism as described above as long as the step of performing the compounding at a temperature of 0 to 20 ° C. is included. ..

When the reaction is carried out in the range of 0 to 20 ° C, the reactivity of cerium with the inorganic oxide is suppressed, so that large-sized CeO ₂ ultrafine particles are produced. _When the metal salt of Cerium is added, the reactivity of cerium with the inorganic oxide is increased and the dissolution of the inorganic oxide is promoted. Generate. In this way, the reaction temperature in the compounding step (step 1) is essential to be 0 to 20 ° C., the reaction temperature is changed to more than 20 ° C. and 98 ° C. or less, and a metal salt of cerium is added to obtain CeO ₂ ultrafine particles and. The particle size distribution of ceria particles can be widened. If there is a step of adding a metal salt of cerium in the compounding temperature range of 0 to 20 ° C., the reaction at a temperature of more than 20 ° C. and 98 ° C. or lower may be performed before or after the reaction at 0 to 20 ° C. However, the temperature may be changed three or more times.
Further, the amount of the cerium metal salt added in the step of reacting at 0 to 20 ° C. when the reaction temperature is carried out in two or more steps shall be in the range of 10 to 90% by mass with respect to the total amount of the cerium metal salt added. Is preferable. If it exceeds this range, the proportion of large (or small) CeO ₂ ultrafine particles and ceria particles is small, so that the particle size distribution is not so wide.

The precursor particle dispersion obtained in step 1 may be further diluted or concentrated with pure water, ion-exchanged water, or the like before being subjected to step 2, and then subjected to the next step 2.

The solid content concentration in the precursor particle dispersion is preferably 1 to 27% by mass.

If desired, the precursor particle dispersion may be deionized using a cation exchange resin, an anion exchange resin, an ultrafiltration membrane, an ion exchange membrane, centrifugation or the like.

<Step 2>
In step 2, the precursor particle dispersion is dried and then calcined at 700 to 1,200 ° C.

The method of drying is not particularly limited. It can be dried using a conventionally known dryer. Specifically, a box-type dryer, a band dryer, a spray dryer, or the like can be used.
It is preferable that the pH of the precursor particle dispersion before drying is 6.0 to 7.0. This is because the surface activity can be suppressed when the pH of the precursor particle dispersion liquid before drying is set to 6.0 to 7.0.

After drying, the firing temperature is 700 to 1200 ° C., preferably 710 to 1100 ° C., more preferably 720 to 1090 ° C., and most preferably 730 to 1090 ° C. When fired in such a temperature range, the crystallization of cerium progresses sufficiently, the cerium-containing coating layer in which the cerium child particles are dispersed has an appropriate film thickness, and the cerium-containing coating layer firmly forms the mother particles. The particles that are bonded and dispersed in the cerium-containing coating layer are less likely to fall off. Further, by firing in such a temperature range, cerium hydroxide and the like are less likely to remain. If this temperature is too high, ceria crystals may grow abnormally, the cerium-containing coating layer may become too thick, the crystalline inorganic oxides that make up the mother particles may crystallize, and the particles may be fused together. be.

Alkali metals, alkaline earth metals, sulfates and the like can be added as flux components during firing to promote crystal growth of ceria, but the flux components can cause metal contamination and corrosion of the polished substrate. Therefore, the content of the flux component at the time of firing is preferably 100 ppm or less, more preferably 50 ppm or less, and most preferably 40 ppm or less per precursor particle (dry).
In addition, the flux component may be brought in from the raw material or used as an alkali used for neutralizing the cerium metal salt at the time of preparation, but when an alkali metal or an alkaline earth metal coexists at the time of preparation, it is crystalline. Since the polymerization of the inorganic oxide fine particles is promoted and densified, the reactivity between cerium hydroxide or the like and the crystalline inorganic oxide fine particles is lowered. Further, since the surface of the crystalline inorganic oxide fine particles is protected by an alkali metal or an alkaline earth metal, the reactivity with cerium hydroxide or the like is suppressed, and the cerium-containing coating layer tends not to be formed. Further, since the dissolution of the inorganic oxide is suppressed during the preparation, it becomes difficult for the atoms of the inorganic oxide to dissolve in the ceria particles.

Further, when fired in such a temperature range, the atom of the inorganic oxide is solid-solved in the crystalline ceria which is the main component of the child particles. Therefore, for cerium atoms and inorganic oxide atoms contained in child particles, when the interatomic distance between cerium and inorganic oxide is R ₁ and the interatomic distance between cerium and cerium is R ₂ , R ₁ <R ₂ Can satisfy the relationship of.

In step 2, a solvent is added to the calcined body obtained by calcining, and a wet crushing treatment is performed in the range of pH 8.6 to 10.8 to obtain a calcined body crushed dispersion.
Here, the fired body may be crushed by a dry method before the fired body is subjected to the wet crushing treatment, and then the crushed body may be subjected to the wet crushing treatment.

As the dry crushing device, a conventionally known device can be used, and examples thereof include an attritor, a ball mill, a vibration mill, and a vibration ball mill.
A conventionally known device can be used as the wet crushing device, but for example, a batch type bead mill such as a basket mill, a horizontal / vertical / annual type continuous bead mill, a sand grinder mill, a ball mill, or the like, and a rotor. -A wet medium stirring type mill (wet crusher) such as a stator type homogenizer, an ultrasonic dispersion type homogenizer, and an impact crusher that collides fine particles in a dispersion liquid with each other can be mentioned. Examples of the beads used in the wet medium stirring mill include beads made of glass, alumina, zirconia, steel, flint stone, organic resin and the like.
Water and / or an organic solvent is used as the solvent used when crushing the fired body in a wet manner. For example, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. The solid content concentration of the fired body crushed dispersion is not particularly limited, but is preferably in the range of, for example, 0.3 to 50% by mass.

When wet crushing is performed on the fired body, it is preferable to perform wet crushing while maintaining the pH of the solvent at 8.6 to 10.8. When the pH is maintained in this range, when cationic colloid titration is performed, the flow potential change amount (ΔPCD) represented by the above formula (1) and the addition amount (V) of the cationic colloid titrator in the knick are set. Finally, a ceria-based composite fine particle dispersion liquid having a flow potential curve having a ratio (ΔPCD / V) of -110.0 to -15.0 can be obtained more easily.
That is, it is preferable to carry out crushing to the extent that the dispersion liquid of the present invention corresponding to the above-mentioned preferable embodiment can be obtained. This is because, as described above, when the dispersion liquid of the present invention corresponding to the preferred embodiment is used as the polishing agent, the polishing speed is further improved. Regarding this, the present inventor further improves the polishing speed by appropriately thinning the cerium-containing coating layer on the surface of the composite fine particles of the present invention and / or appropriately exposing the child particles to a part of the surface of the composite fine particles. Moreover, it is presumed that the shedding of ceria particles can be controlled. Further, during crushing, the inorganic oxide in the cerium-containing coating layer is dissolved and deposited again, so that a soft and easily soluble inorganic oxide layer is formed in the outermost layer, and the easily soluble inorganic oxide is formed. It is estimated that the layer adheres to the substrate to improve the frictional force and the polishing speed. In addition, since the cerium-containing coating layer is thin or peeled off, it is estimated that the child particles are likely to be detached to some extent during polishing. ΔPCD / V is more preferably -100.0 to -15.0, and even more preferably -100.0 to -20.0.
If the pH is out of the predetermined pH range, such as loosening the calcined powder without going through the wet crushing step as in step 2, only dry crushing / crushing, or even wet crushing, ΔPCD. / V is unlikely to be in the range of -100.0 to -15, and it is difficult to form a soft and easily soluble cerium-containing coating layer.

<Process 3>
In step 3, the calcined body crushed dispersion obtained in step 2 is subjected to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and then the sedimentation component is removed to obtain a ceria-based composite fine particle powder.
Specifically, the fired body crushed dispersion is classified by centrifugation. The relative centrifugal acceleration in the centrifugation process is 300 G or more. After the centrifugation treatment, the sedimentation component can be removed to obtain a ceria-based composite fine particle dispersion. The upper limit of the relative centrifugal acceleration is not particularly limited, but is practically used at 10,000 G or less.

In step 3, it is necessary to provide a centrifugation treatment satisfying the above conditions. If the centrifugal acceleration does not meet the above conditions, coarse particles will remain in the ceria-based composite fine particle dispersion, and scratches will occur when used for polishing applications such as abrasives using the ceria-based composite fine particle dispersion. It causes the occurrence.

In the present invention, the ceria-based composite fine particle dispersion obtained by the above-mentioned production method can be further dried to obtain ceria-based composite fine particles. The drying method is not particularly limited, and for example, it can be dried using a conventionally known dryer.

The dispersion liquid of the present invention can be obtained by such a production method of the present invention.

<Abrasive grain dispersion for polishing>
The liquid containing the dispersion liquid of the present invention can be preferably used as a polishing abrasive grain dispersion liquid (hereinafter, also referred to as "polishing abrasive grain dispersion liquid of the present invention"). In particular, it can be suitably used as an abrasive grain dispersion liquid for polishing for flattening a semiconductor substrate on which a SiO ₂ insulating film is formed. Further, a chemical component can be added to control the polishing performance, and the polishing slurry can be suitably used.

The abrasive grain dispersion liquid for polishing of the present invention has excellent effects such as high polishing speed when polishing a semiconductor substrate, less scratches (scratches) on the polished surface during polishing, and less residual abrasive grains on the substrate. ing.

The abrasive grain dispersion liquid for polishing of the present invention contains water and / or an organic solvent as a dispersion solvent. As the dispersion solvent, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. Further, the polishing abrasive grain dispersion liquid of the present invention is selected from the group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster and a pH buffer as an additive for controlling the polishing performance1. It is suitably used as a polishing slurry by adding seeds or more.

<Abrasive accelerator>
Although it depends on the type of the material to be polished, it can be used as a polishing slurry by adding a conventionally known polishing accelerator to the abrasive grain dispersion liquid for polishing of the present invention, if necessary. Examples of such include hydrogen peroxide, peracetic acid, urea peroxide and the like, and mixtures thereof. When such an abrasive composition containing a polishing accelerator such as hydrogen peroxide is used, the polishing rate can be effectively improved when the material to be polished is a metal.

Other examples of polishing accelerators include inorganic acids such as sulfuric acid, nitrate, phosphoric acid, oxalic acid and hydrofluoric acid, organic acids such as acetic acid, or sodium salts, potassium salts, ammonium salts, amine salts and the like of these acids. And the like. In the case of a polishing composition containing these polishing accelerators, when polishing a material to be polished composed of a composite component, by accelerating the polishing rate for a specific component of the material to be polished, finally flat polishing is performed. You can get a face.

When the abrasive grain dispersion liquid for polishing of the present invention contains a polishing accelerator, the content thereof is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass. ..

<Surfactant and / or hydrophilic compound>
In order to improve the dispersibility and stability of the abrasive grain dispersion liquid for polishing of the present invention, a cationic, anionic, nonionic or amphoteric surfactant or hydrophilic compound can be added. Both the surfactant and the hydrophilic compound have an action of lowering the contact angle with the surface to be polished and have an action of promoting uniform polishing. As the surfactant and / or the hydrophilic compound, for example, those selected from the following groups can be used.

Examples of the anionic surfactant include carboxylates, sulfonates, sulfates and phosphates, and the carboxylates include soaps, N-acylamino acid salts, polyoxyethylene or polyoxypropylene alkyl ether carboxylics. Acid salts, acylated peptides; as sulfonates, alkyl sulfonates, alkylbenzene and alkyl naphthalene sulfonates, naphthalene sulfonates, sulfosuccinates, α-olefin sulfonates, N-acyl sulfonates; sulfate esters. As salts, sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkylallyl ether sulfates, alkylamide sulfates; as phosphate ester salts, alkyl phosphates, polyoxyethylene or poly Oxypropylene alkyl allyl ether phosphate can be mentioned.

As cationic surfactants, aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, imidazolinium salts; as amphoteric surfactants, carboxybetaine type, sulfobetaine type, Aminocarboxylates, imidazolinium betaine, lecithin, alkylamine oxides can be mentioned.

Examples of the nonionic surfactant include an ether type, an ether ester type, an ester type, and a nitrogen-containing type, and examples of the ether type are polyoxyethylene alkyl and alkylphenyl ether, alkylallyl formaldehyde condensed polyoxyethylene ether, and polyoxyethylene poly. Examples thereof include oxypropylene block polymer and polyoxyethylene polyoxypropylene alkyl ether, and examples of the ether ester type include polyoxyethylene ether for glycerin ester, polyoxyethylene ether for sorbitan ester, polyoxyethylene ether for sorbitol ester, and ester type. Examples of polyethylene glycol fatty acid ester, glycerin ester, polyglycerin ester, sorbitan ester, propylene glycol ester, sucrose ester, and nitrogen-containing type include fatty acid alkanolamide, polyoxyethylene fatty acid amide, and polyoxyethylene alkylamide. In addition, a fluorine-based surfactant and the like can be mentioned.

As the surfactant, an anionic surfactant or a nonionic surfactant is preferable, and examples of the salt include an ammonium salt, a potassium salt, a sodium salt and the like, and an ammonium salt and a potassium salt are particularly preferable.

Further, other surfactants, hydrophilic compounds and the like include esters such as glycerin ester, sorbitan ester and alanine ethyl ester; polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol alkyl ether, polyethylene glycol alkenyl ether and alkyl. Polyethylene Glycol, Alkyl Polyethylene Glycol Alkyl Ether, Alkyl Polyethylene Glycol Alkenyl Ether, Alkenyl Polyethylene Glycol, Alkenyl Polyethylene Glycol Alkyl Ether, Alkenyl Polyethylene Glycol Alkenyl Ether, Polypropylene Glycol Alkyl Ether, Polypropylene Glycol Alkenyl Ether, Alkyl Polypropylene Glycol, Alkyl Polypropylene Glycol Alkyl Ether , Alkyl Polypropylene Glycol Alkenyl Ethers, Esteryl Polypropylene Glycols and Other Ethers; Polysaccharides such as Arginic Acid, Pectic Acid, Carboxymethyl Cellulose, Cardolan and Pluran; Amino Acid Salts such as Glycinammonium Salts and Glycin Sodium Salts; Polylysine, polyappleic acid, polymethacrylic acid, polyammonium methacrylate, sodium polymethacrylate, polyamic acid, polymaleic acid, polyitaconic acid, polyfumalic acid, poly (p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, amino Polycarboxylic acids such as polyacrylamide, ammonium polyacrylic acid salt, sodium polyacrylic acid salt, polyamic acid, ammonium polyamic acid salt, sodium polyamic acid salt and polyglioxylic acid and salts thereof; Vinyl-based polyma; ammonium methyltaurate, sodium methyltaurate, methylsodium sulfate, ethylammonium sulfate, butylammonium sulfate, sodium vinylsulfonic acid, sodium 1-allylsulfonic acid, 2-allylsulfonic acid Sulfonic acids and salts thereof such as sodium salt, sodium methoxymethyl sulfonic acid salt, ammonium ethoxymethyl sulfonic acid salt, sodium 3-ethoxypropyl sulfonic acid salt; propionamide, acrylamide, methyl urea, nicotine amide, succinic acid amide and sulf Examples thereof include amides such as ananyl amides.

When the substrate to be polished is a glass substrate or the like, any surfactant can be preferably used, but in the case of a silicon substrate for a semiconductor integrated circuit or the like, alkali metal or alkaline soil can be used. When the influence of contamination by metals or halides is disliked, it is desirable to use an acid or an ammonium salt-based surfactant thereof.

When the abrasive grain dispersion liquid of the present invention contains a surfactant and / or a hydrophilic compound, the total amount thereof shall be 0.001 to 10 g in 1 L of the abrasive grain dispersion liquid for polishing. It is preferably 0.01 to 5 g, more preferably 0.1 to 3 g, and particularly preferably 0.1 to 3 g.

The content of the surfactant and / or the hydrophilic compound is preferably 0.001 g or more in 1 L of the abrasive grain dispersion for polishing, and preferably 10 g or less from the viewpoint of preventing a decrease in the polishing speed in order to obtain a sufficient effect. ..

Only one type of surfactant or hydrophilic compound may be used, two or more types may be used, or different types may be used in combination.

<Heterocyclic compound>
The abrasive grain dispersion liquid for polishing of the present invention has the purpose of suppressing the erosion of the substrate to be polished by forming a passivation layer or a dissolution suppressing layer on the metal when the substrate to be polished contains a metal. Heterocyclic compounds may be contained. Here, the "heterocyclic compound" is a compound having a heterocycle containing one or more heteroatoms. Heteroatom means an atom other than a carbon atom or a hydrogen atom. The heterocycle means a cyclic compound having at least one heteroatom. Heteroatoms refer only to the atoms that form the constituents of the heterocyclic ring system, and may be located outside the ring system, separated from the ring system by at least one unconjugated single bond, or the ring system. It does not mean an atom that is part of a further substituent of. Preferred heteroatoms include, but are not limited to, nitrogen atoms, sulfur atoms, oxygen atoms, selenium atoms, tellurium atoms, phosphorus atoms, silicon atoms, and boron atoms. As an example of the heterocyclic compound, imidazole, benzotriazole, benzothiazole, tetrazole and the like can be used. More specifically, 1,2,3,4-tetrazole, 5-amino-1,2,3,4-tetrazole, 5-methyl-1,2,3,4-tetrazole, 1,2,3- Triazole, 4-amino-1,2,3-triazole, 4,5-diamino-1,2,3-triazole, 1,2,4-triazole, 3-amino1,2,4-triazole, 3,5 -Diamino-1,2,4-triazole and the like can be mentioned, but the present invention is not limited thereto.

The content of the heterocyclic compound in the abrasive grain dispersion liquid for polishing of the present invention is preferably 0.001 to 1.0% by mass, preferably 0.001 to 0.7% by mass. Is more preferable, and 0.002 to 0.4% by mass is further preferable.

<pH adjuster>
The pH of the polishing composition can be adjusted by adding an acid or a base and a salt compound thereof, if necessary, in order to enhance the effect of each of the above additives.

When adjusting the polishing abrasive grain dispersion of the present invention to pH 7 or higher, an alkaline pH adjusting agent is used. Desirably, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, tetramethylamine and the like are used.

When the polishing abrasive grain dispersion liquid of the present invention is adjusted to a pH of less than 7, an acidic one is used as the pH adjusting agent. For example, mineral acids such as hydrochloric acid and nitric acid such as hydroxy acids such as acetic acid, lactic acid, citric acid, malic acid, tartaric acid and glyceric acid are used.

<pH buffer>
A pH buffer may be used to keep the pH value of the abrasive grain dispersion for polishing of the present invention constant. As the pH buffer, for example, phosphates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammo tetrahydrate tetrahydrate, and borates or organic acid salts can be used.

Further, as the dispersion solvent of the abrasive grain dispersion liquid for polishing of the present invention, for example, alcohols such as methanol, ethanol, isopropanol, n-butanol, methylisocarbinol; acetone, 2-butanone, ethyl amylketone, diacetone alcohol, etc. Ketones such as isophorone and cyclohexanone; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran and the like. Ethers; Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; Glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate Kind; Ethers such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethylene carbonate; Fragrant hydrocarbons such as benzene, toluene, xylene; Fat group hydrocarbons such as hexane, heptane, isooctane, cyclohexane Classes; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, chlorbenzene; sulfoxides such as dimethylsulfoxide; pyrrolidones such as N-methyl-2-pyrrolidone, N-octyl-2-pyrrolidone. And other organic solvents can be used. These may be mixed with water and used.

The solid content concentration contained in the abrasive grain dispersion liquid for polishing of the present invention is preferably in the range of 0.3 to 50% by mass. If this solid content concentration is too low, the required polishing rate may not be reached. On the contrary, even if the solid content concentration is too high, the polishing speed is rarely improved further.

Hereinafter, the present invention will be described based on examples. The present invention is not limited to these examples.

<Experiment 1>
First, the details of each measurement method and test method in Examples and Comparative Examples will be described. For each Example and Comparative Example, the following measurement results and test results are shown in Table 1.

The compressive fracture strength of the crystalline inorganic oxide fine particles contained in the crystalline inorganic oxide fine particle dispersion used as a raw material in Examples and Comparative Examples was measured by the following method.
The composite fine particle dispersion was crushed by a sand mill and classified and separated by a centrifuge to obtain mother particles, and the compression fracture strength was measured using a microcompression tester (MCT-W500) manufactured by Shimadzu Corporation.

<Average particle diameter and minor / major diameter ratio>
With respect to the ceria-based composite fine particle dispersions obtained in Examples and Comparative Examples, the average particle diameter and the minor axis / major axis ratio of the ceria-based composite fine particles contained therein were measured by the above-mentioned image analysis method.
That is, the average particle diameter and the minor axis / major axis ratio of the ceria-based composite fine particles in the ceria-based composite fine particle dispersion are calculated based on the photographic projections obtained by taking photographs using a transmission electron microscope as described above. The value obtained was taken as the average particle diameter or the minor / major diameter ratio.

[Measurement of CeO ₂ content and other contents]
The weight of the ceria-based composite fine particle dispersion is reduced by burning at 1000 ° C., and the mass of the solid content is determined.
Next, about 1 g of a sample (adjusted to a solid content of 20% by mass) consisting of a ceria-based composite fine particle dispersion is collected in a platinum dish. Add 3 ml of phosphoric acid, 5 ml of nitric acid and 10 ml of hydrofluoric acid and heat on a sand bath. After drying, add a small amount of water and 50 ml of nitric acid to dissolve and put in a 100 ml volumetric flask, and add water to make 100 ml.
Next, the operation of collecting 10 ml of the separated solution in a 20 ml volumetric flask from the solution contained in 100 ml is repeated 5 times to obtain 5 10 ml of the separated solution.
Then, using this, measurement is performed by a standard addition method with an ICP plasma emission spectrometer (for example, SII, SPS5520). Here, the blank is also measured by the same method, and the blank is subtracted and adjusted to obtain the measured value of Ce.
Then, the content of CeO ₂ and the content other than CeO ₂ are obtained based on the above-mentioned mass of solid content, and the mass ratio of these is calculated.

[Coefficient of variation (CV value)]
The particle size distribution of the child particles is obtained by the above method, the standard deviation and the number mean value are obtained using the particle size distribution as the population, then the standard deviation is divided by the number mean value and multiplied by 100 (that is, the standard). The coefficient of variation (CV value) in the particle size distribution of the child particles was obtained from the deviation / number mean value × 100).

[X-ray diffraction method, measurement of average crystallite diameter]
The ceria-based composite fine particle dispersions obtained in Examples and Comparative Examples were dried using a conventionally known dryer, and the obtained powder was pulverized in a mortar for 10 minutes, and an X-ray diffractometer (Rigaku Denki Co., Ltd.) ), An X-ray diffraction pattern was obtained by RINT1400), and the crystal types of ceria and crystalline inorganic oxide were identified.
Further, the full width at half maximum of the peak of the (111) plane (near 2θ = 28 degrees) near 2θ = 28 degrees in the obtained X-ray diffraction pattern was measured by the above-mentioned method, and the average crystallite was measured by Scherrer's equation. The diameter was calculated.

[Polishing test method]
<Polishing of SiO ₂ film>
The abrasive grain dispersion liquid for polishing containing the ceria-based composite fine particle dispersion liquid obtained in each of the examples and the comparative examples was prepared. Here, the solid content concentration was 0.6% by mass, and nitric acid was added to adjust the pH to 5.0.
Next, as a substrate to be polished, a SiO ₂ insulating film (thickness 1 μm) substrate prepared by a thermal oxidation method was prepared.
Next, this substrate to be polished is set in a polishing device (Nanofactor Co., Ltd., NF300), and a polishing pad (“IC-1000 / SUBA400 concentric circle type” manufactured by Nitta Hearth Co., Ltd.) is used, and the substrate load is 0.5 MPa, the table. Polishing was performed by supplying a polishing abrasive grain dispersion at a rotation speed of 90 rpm for 1 minute at a rate of 50 ml / min.
Then, the polishing rate was calculated by obtaining the weight change of the substrate to be polished before and after polishing.
Further, the smoothness (surface roughness Ra) of the surface of the polishing substrate was measured using an atomic force microscope (AFM, manufactured by Hitachi High-Tech Science Co., Ltd.). Since the smoothness and the surface roughness are generally in a proportional relationship, the surface roughness is shown in Table 1.
The polishing scratches were observed by observing the surface of the insulating film using an optical microscope.

<Aluminum hard disk polishing>
The abrasive grain dispersion liquid for polishing containing the ceria-based composite fine particle dispersion liquid obtained in each of the examples and the comparative examples was prepared. Here, the solid content concentration was 9% by mass, and nitric acid was added to adjust the pH to 2.0.
Set the substrate for the aluminum hard disk in the polishing device (Nanofactor Co., Ltd., NF300), and use the polishing pad (Nitta Hearth Co., Ltd. "Polytex φ12") to prepare the polishing slurry at a substrate load of 0.05 MPa and a table rotation speed of 30 rpm. Polishing is performed by supplying at a rate of 20 ml / min for 5 minutes, and the entire surface is observed with Zoom15 using an ultrafine defect / visualization macro device (manufactured by VISION PSYTEC, product name: Micro-Max), and 65.97 cm ² The number of scratches (linear marks) existing on the surface of the polished substrate corresponding to the above was counted and totaled, and evaluated according to the following criteria.
Number of linear marks Evaluation Less than 50 "Very few"
50 to less than 80 "less"
80 or more "many"
At least 80 or more, too many to count the total number "*"

Examples are described below. The term "solid content concentration" simply means the concentration of fine particles dispersed in a solvent regardless of the chemical species.

<Example 1> α-Al ₂ O ₃ core [Preparation of crystalline inorganic oxide dispersion liquid]
To 180 g of α-Al ₂ O ₃ (Advanced Alumina AA-03 manufactured by Sumitomo Chemical Co., Ltd.), 5815.1 g of ion-exchanged water was added, and ultrasonic treatment was performed for 2 hours. Next, 4.9 g of 3% ammonia was added and mixed to obtain 6000 g of a dispersion liquid having an Al ₂ O ₃ solid content concentration of 3% by mass (hereinafter, also referred to as A-1 liquid).

Next, ion-exchanged water was added to cerium nitrate (III) hexahydrate (4N high-purity reagent manufactured by Kanto Chemical Co., Inc.), and a 3.0 mass% cerium nitrate aqueous solution (hereinafter referred to as B-1 solution) in terms of CeO ₂ was added. Also called).

Next, the A-1 solution (6000 g) was kept at 10 ° C., and the B-1 solution (7,186 g, CeO ₂ dry215.6 g) was added thereto over 18 hours while stirring. During this period, the liquid temperature was maintained at 10 ° C., and 3% aqueous ammonia was added as needed to maintain the pH at 7.9 to 8.7. Then, after the addition was completed, aging was carried out at a liquid temperature of 10 ° C. for 4 hours. During the addition and aging of the B-1 liquid, the preparation was carried out while blowing air into the preparation liquid, and the redox potential was maintained at 100 to 300 mV.
Then, washing was performed while replenishing ion-exchanged water with an adventitia. The precursor particle dispersion obtained after washing has a solid content concentration of 4.7% by mass, a pH of 8.2 (at 25 ° C), and a conductivity of 19 μs / cm (at 25 ° C). there were

Next, the obtained precursor particle dispersion was dried in a dryer at 120 ° C. for 16 hours, and then calcined for 2 hours in a muffle furnace at 750 ° C. to obtain a powder (firing body).

After adding 300 g of ion-exchanged water to 100 g of powder (calcined body) obtained after firing and adjusting the pH to 10.1 using a 3% aqueous ammonia solution, φ0.25 mm quartz beads (Daken Kagaku Kogyo Co., Ltd.) Wet crushing (batch type tabletop sand mill manufactured by Kampe Co., Ltd.) was performed for 30 minutes at (manufactured by the company).
Then, after crushing, the beads were separated through a 44 mesh wire mesh. The solid content concentration of the obtained calcined body crushed dispersion was 7.1% by mass, and the weight was 1178 g. During crushing, an aqueous ammonia solution was added to keep the pH at 10.1.

Further, the crushed dispersion was treated with a centrifuge (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at 509G for 60 seconds, and the light liquid was recovered to obtain a ceria-based composite fine particle dispersion.

The average particle size and the minor / major axis ratio of the ceria-based composite fine particles contained in the obtained ceria-based composite fine particle dispersion were measured. The measurement method is an image analysis method based on the transmission electron micrograph as described above.
In addition, the minor axis / major axis ratio of the mother particles in the ceria-based composite fine particles was measured using the above-mentioned STEM-EDS analysis.
In addition, the coefficient of variation (CV value) in the particle size distribution of the child particles was obtained by the above-mentioned method.
In addition, the mass ratio of components other than ceria contained in the ceria-based composite fine particle dispersion and ceria was determined by the above-mentioned method.
In addition, the X-ray diffraction pattern of the ceria-based composite fine particles was obtained by the above-mentioned method, and the crystal types of ceria and the crystalline inorganic oxide were specified. Furthermore, the average crystallite diameter of the ceria-based composite fine particles was determined.
The results are shown in Table 1.

Next, a polishing test was performed using the obtained ceria-based composite fine particle dispersion.
The results are shown in Table 1.

<Example 2> α-Al ₂ O ₃ core After adding 400 g of ion-exchanged water to 100 g of α-Al ₂ O ₃ used in Example 1 and further adjusting the pH to 3.8 with a 7% aqueous nitrate solution. , Wet crushing (batch type tabletop sand mill manufactured by Kampe Co., Ltd.) was performed for 120 minutes instead of ultrasonic treatment with quartz beads (manufactured by Daiken Kagaku Kogyo Co., Ltd.) having a diameter of 0.25 mm.
Then, after crushing, the beads were separated through a 44 mesh wire mesh. The solid content concentration of the obtained α-Al ₂ O ₃ crushed dispersion was 6.6% by mass, and the weight was 1401 g. During crushing, an aqueous nitric acid solution was added to keep the pH at 4.4. Next, 13 g of anion exchange resin (SANUP B manufactured by Mitsubishi Chemical Corporation) was gradually added to 1340 g of this α-Al ₂ O ₃ crushed dispersion, stirred for 9 minutes, and the resin was separated using 1200 g of ion exchange water. did. The pH at this time was 8.4.
Next, the same operation as in Example 1 was carried out except that the amount of the A-1 liquid to be added was 4000 g and the firing temperature was 760 ° C., and the same evaluation was performed.
The results are shown in Table 1.

<Example 3> The same operation as in Example 1 was performed except that the A-1 liquid to be added to the α-Al ₂ O ₃ core was 1100 g and the firing temperature was 950 ° C., and the same evaluation was performed.
The results are shown in Table 1.

<Example 4> TiO ₂ core After changing the α-Al ₂ O ₃ used in Example 1 to anatase-type TiO ₂ and further drying the precursor particle dispersion in a dryer at 120 ° C. for 16 hours. The same operation as in Example 1 was performed except that the firing temperature was set to 950 ° C., and the same evaluation was performed.
The results are shown in Table 1.

<Example 5> ZrO ₂ core The firing temperature after changing α-Al ₂ O ₃ used in Example 1 to ZrO ₂ and further drying the precursor particle dispersion in a dryer at 120 ° C. for 16 hours. The same operation as in Example 1 was performed except that the temperature was set to 900 ° C., and the same evaluation was performed.
The results are shown in Table 1.

<Comparative Example 1>
Preparation of << Silica Fine Particle Dispersion Liquid (Average Particle Diameter of Silica Fine Particles 60 nm) >> 12,090 g of ethanol and 6,363.9 g of ethyl orthosilicate were mixed to prepare _a mixed liquid a1.
Next, 6,120 g of ultrapure water and 444.9 g of 29% ammonia water were mixed to prepare a mixed solution b ₁ .
Next, 192.9 g of ultrapure water and 444.9 g of ethanol were mixed to prepare water for spreading.
Then, the spread water was adjusted to 75 ° C. while stirring, and the mixed liquid a ₁ and the mixed liquid b ₁ were simultaneously added to this so that the addition was completed in 10 hours each. After the addition is completed, the liquid temperature is kept at 75 ° C. for 3 hours for aging, and then the solid content concentration is adjusted to obtain a SiO ₂ solid content concentration of 19% by mass and a dynamic light scattering method (PAR-Made by Otsuka Electronics Co., Ltd.). A silica fine particle dispersion liquid in which silica fine particles having an average particle diameter of 60 nm measured in III) were dispersed in a solvent was obtained in an amount of 9,646.3 g.

Preparation of << Silica Fine Particle Dispersion Solution (Average Particle Diameter of Silica Fine Particles: 108 nm) >> 2,733.3 g of methanol and 1,822.2 g of ethyl orthosilicate were mixed to prepare a mixed solution a ₂ .
Next, 1,860.7 g of ultrapure water and 40.6 g of 29% ammonia water were mixed to prepare a mixed solution b ₂ .
Next, 59 g of ultrapure water and 1,208.9 g of methanol were mixed and used as water to prepare 922.1 g of a silica fine particle dispersion liquid in which silica fine particles having an average particle diameter of 60 nm obtained in the previous step were dispersed in a solvent. added.
Then, the bedding water containing the silica fine particle dispersion liquid was adjusted to 65 ° C. while stirring, and the mixed liquid a ₂ and the mixed liquid b ₂ were simultaneously added to this so that the addition was completed in 18 hours each. rice field. After the addition is completed, the liquid temperature is kept at 65 ° C. for 3 hours for aging, and then the solid content concentration (SiO ₂ solid content concentration) is adjusted to 19% by mass, and 3,600 g of high-purity silica fine particle dispersion liquid is used. Got
The silica fine particles contained in this high-purity silica fine particle dispersion had an average particle diameter of 108 nm as measured by a dynamic light scattering method (PAR-III manufactured by Otsuka Electronics Co., Ltd.). Similarly, when the minor axis / major axis ratio of the silica fine particles was measured based on a transmission electron micrograph, the minor axis / major axis ratio was 1.0. In addition, the content of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, NO ₃ , SO ₄ and F is set to ICP (inductively coupled plasma). When measured using luminescence analysis), it was 1 ppm or less in each case.

Next, 114 g of a cation exchange resin (SK-1BH manufactured by Mitsubishi Chemical Corporation) was gradually added to 1,053 g of this high-purity silica fine particle dispersion (average particle size of silica fine particles: 108 nm), and the resin was stirred for 30 minutes. separated. The pH at this time was 5.1.
Ultrapure water was added to the obtained silica fine particle dispersion to obtain 6,000 g of A-2 liquid having a SiO ₂ solid content concentration of 3% by mass.

Next, ion-exchanged water was added to cerium nitrate (III) hexahydrate (4N high-purity reagent manufactured by Kanto Chemical Co., Inc.) to obtain a B-2 solution of 2.5% by mass in terms of CeO ₂ .

Next, the temperature of liquid A-2 (6,000 g) was raised to 50 ° C., and while stirring, CeO ₂ was added to 100 parts by mass of liquid B-2 (8,453 g, SiO ₂ ). (Corresponding to 4 parts by mass) was added over 18 hours. During this period, the liquid temperature was maintained at 50 ° C., and if necessary, 3% aqueous ammonia was added to maintain the pH at 7.85. During the addition and aging of the B-2 solution, the formulation was carried out while blowing air into the formulation, and the redox potential was maintained at a positive value.
Then, when the addition of the B-2 liquid was completed, the liquid temperature was raised to 93 ° C. and aging was carried out for 4 hours. After the aging was completed, the mixture was allowed to cool by leaving it indoors, cooled to room temperature, and then washed while being replenished with ion-exchanged water with an adventitia. The precursor particle dispersion obtained after washing had a solid content concentration of 7% by mass, a pH of 9.1 (at 25 ° C), and a conductivity of 67 μs / cm (at 25 ° C). ..

Next, a 5 mass% acetic acid aqueous solution was added to the obtained precursor particle dispersion to adjust the pH to 6.5, and the mixture was dried in a dryer at 100 ° C. for 16 hours, and then used in a muffle furnace at 1090 ° C. The mixture was fired for 2 hours to obtain a powder.

310 g of the powder obtained after firing and 430 g of ion-exchanged water were placed in a 1 L patterned beaker, a 3% aqueous ammonia solution was added thereto, and ultrasonic waves were irradiated in an ultrasonic bath for 10 minutes while stirring. A suspension having a pH of 10 (temperature: 25 ° C.) was obtained.
Next, 595 g of quartz beads having a diameter of 0.25 mm were put into a crusher (LMZ06 manufactured by Ashizawa Finetech Co., Ltd.) that had been washed with equipment and operated with water in advance, and the above suspension was further placed in the charge tank of the crusher. It was filled (filling rate 85%). Considering the ion-exchanged water remaining in the crushing chamber of the crusher and the piping, the concentration at the time of crushing is 25% by mass. Then, wet crushing and crushing were performed under the conditions that the peripheral speed of the disk in the crusher was 12 m / sec, the number of passes was 25, and the residence time per pass was 0.43 minutes. In addition, a 3% aqueous ammonia solution was added for each pass so as to maintain the pH of the suspension at the time of crushing and pulverization at 10. In this way, a silica-based composite fine particle dispersion having a solid content concentration of 22% by mass was obtained.
Next, the obtained fine particle dispersion was centrifuged at a relative centrifugal acceleration of 675 G for 1 minute using a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") to remove sedimentation components and disperse silica-based composite fine particles. Obtained liquid.

The silica-based composite fine particle dispersion thus obtained was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

The ceria-based composite fine particles contained in the dispersion liquid of the present invention have low scratch and high polishing speed. Therefore, the polishing abrasive grain dispersion liquid containing the dispersion liquid of the present invention can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring boards. Specifically, it can be preferably used for flattening a semiconductor substrate on which a silica film is formed.

Claims (9)

A ceria-based composite containing the following features [1] to [5], a minor axis / major axis ratio in the range of 0.2 to 1.0, and an average particle diameter of 50 to 1000 nm. Fine particle dispersion.
[1] The ceria-based composite fine particles have a mother particle, a cerium-containing coating layer on the surface of the mother particle, and child particles dispersed inside the cerium-containing coating layer, and the mother particle is The main component is crystalline inorganic oxide, and the child particles are mainly composed of crystalline cerium.
[2] The coefficient of variation (CV value) in the particle size distribution of the child particles is 14 to 60%.
[3] The ceria-based composite fine particles have a mass ratio of a component other than ceria and ceria in the range of 100: 11 to 316.
[4] When the ceria-based composite fine particles are subjected to X-ray diffraction, the crystal phase of ceria and the crystal phase of the crystalline inorganic oxide are detected.
[5] The ceria-based composite fine particles have an average crystallinity diameter of 10 to 25 nm, which is measured by subjecting them to X-ray diffraction. The ceria-based composite fine particle dispersion liquid according to claim 1, wherein the crystalline inorganic oxide is at least one selected from the group consisting of alumina, titania and zirconia. The ceria-based composite fine particle dispersion according to claim 1 or 2, wherein the cerium-containing coating layer contains the same elements and cerium as the mother particles. The ceria-based composite fine particle dispersion according to any one of claims 1 to 3, wherein the cerium-containing coating layer contains silica. The ceria-based composite fine particle dispersion according to any one of claims 1 to 4, wherein the mother particle has a compression fracture strength of 1.0 to 3.0 MPa. An abrasive grain dispersion liquid for polishing containing the ceria-based composite fine particle dispersion liquid according to any one of claims 1 to 5. The abrasive grain dispersion liquid for polishing according to claim 6, which is for flattening a semiconductor substrate on which a silica film is formed. A method for producing a ceria-based composite fine particle dispersion, which comprises the following steps 1 to 3.
Step 1: Stir the crystalline inorganic oxide fine particle dispersion liquid in which the crystalline inorganic oxide fine particles having a minor axis / major axis ratio of 0.1 or more and less than 1.0 are dispersed in a solvent, and set the temperature to 0 to 20. A precursor particle dispersion containing precursor particles by continuously or intermittently adding a metal salt of cerium to the temperature, pH of 7.0 to 9.0, and redox potential of 50 to 500 mV. The process of obtaining.
Step 2: The precursor particle dispersion is dried, calcined at 700 to 1,200 ° C., a solvent is added to the obtained calcined product, and the mixture is crushed in a wet manner in the range of pH 8.6 to 10.8. A process of processing to obtain a calcined body crushed dispersion.
Step 3: A step of centrifuging the fired body crushed dispersion at a relative centrifugal acceleration of 300 G or more, and subsequently removing the sedimentation component to obtain a ceria-based composite fine particle dispersion. In step 1, the crystalline inorganic oxide fine particle dispersion is stirred, and the temperature is maintained at 0 to 20 ° C., the pH is maintained at 7.0 to 9.0, and the redox potential is maintained at 50 to 500 mV. The method for producing a ceria-based composite fine particle dispersion according to claim 8, which is a step of continuously or intermittently adding the metal salt and the component containing silicon to obtain the precursor particle dispersion.

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