JP2017206410A - Manufacturing method of silica-based composite fine particle dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a silica-based composite particle dispersion capable of polishing even a silica film, a Si wafer or a hardly processing material at high speed and achieving high face accuracy.SOLUTION: There are provided a silica-based composite particle dispersion and a manufacturing method therefor including following processes. A process for stirring a silica fine particle dispersion by dispersing silica fine particles having a ratio between secondary particle diameter (D2) and specific surface area conversion particle diameter (DS), [D2/DS] of more than 1.0, continuously or intermittently adding metal salt of cerium to the same while maintaining temperature and pH in a specific range to obtain a precursor particle dispersion containing a precursor particle. A process for drying the precursor particle dispersion, burning the same at 400 to 1200°C, and treating the resulting burned body to obtain a burned body crushed dispersion. A process for conducting a centrifugal separation treatment at relative centrifugal acceleration of 300 G or more on the burned body crushed dispersion, and then removing a precipitation component to obtain the silica-based composite particle dispersion.SELECTED DRAWING: None

Description

  TECHNICAL FIELD The present invention relates to a method for producing a silica-based composite fine particle dispersion suitable as an abrasive used in the production of semiconductor devices, and in particular, a film to be polished formed on a substrate is subjected to chemical mechanical polishing (Chemical Mechanical Polishing, CMP). The present invention relates to a method for producing a silica-based composite fine particle dispersion for planarization. The present invention also relates to a silica-based composite fine particle dispersion obtained from the production method and a polishing slurry containing the silica-based composite fine particle dispersion.

  Semiconductor devices such as semiconductor substrates and wiring boards achieve high performance through high density and miniaturization. In this semiconductor manufacturing process, so-called chemical mechanical polishing (CMP) is applied. Specifically, this technology is indispensable for shallow trench isolation, planarization of interlayer insulating films, formation of contact plugs and Cu damascene wiring, etc. It has become.

In general, an abrasive for CMP comprises abrasive grains and a chemical component, and the chemical component plays a role of promoting polishing by oxidizing or corroding a target film. On the other hand, abrasive grains have a role of polishing by mechanical action, and colloidal silica, fumed silica, and ceria particles are used as abrasive grains. In particular, since ceria particles exhibit a high polishing rate specifically with respect to a silicon oxide film, they are applied to polishing in a shallow trench element separation step.
In the shallow trench isolation process, not only the silicon oxide film but also the silicon nitride film is polished. In order to facilitate element isolation, 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 polishing method for such a member, after performing a relatively rough primary polishing process, and then performing a precise secondary polishing process, a smooth surface or a highly accurate surface with few scratches such as scratches can be obtained. The way to get done.
Conventionally, for example, the following methods have been proposed for the abrasive used for the secondary polishing as the finish polishing.

  For example, in Patent Document 1, an aqueous solution of cerium nitrate and a base are stirred and mixed in an amount ratio of pH 5 to 10, followed by rapid heating to 70 to 100 ° C. and aging at that temperature. A method for producing cerium oxide ultrafine particles (average particle size of 10 to 80 nm) composed of a single crystal of cerium oxide characterized by the following is described. Further, according to this production method, the particle size is highly uniform and the particle shape It is described that ultrafine cerium oxide particles can be provided.

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

  Furthermore, Patent Document 2 discloses that the surface of the amorphous silica particles A has at least one selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium. A silica-based composite particle characterized by having a crystalline oxide layer B containing an element is described. As a preferred embodiment, an amorphous oxide layer containing an element such as aluminum on the surface of the amorphous silica particles A, which is different from the amorphous silica layer A crystalline oxide layer having C and further containing one or more elements selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium Silica-based composite particles characterized by having B are described. And since such a silica type composite particle has the crystalline oxide layer B on the surface of the amorphous silica particle A, it can improve a grinding | polishing speed and pre-process on a silica particle. By suppressing the sintering of particles during firing, the dispersibility in the polishing slurry can be improved, and further, the amount of cerium oxide used can be greatly reduced without containing cerium oxide. Therefore, it is described that it is possible to provide an abrasive that is inexpensive and has high polishing performance. Further, it is described that those having an amorphous oxide layer C between the silica-based particles A and the oxide layer B are particularly excellent in the effect of suppressing the sintering of particles and the effect of improving the polishing rate.

Japanese Patent No. 2746861 JP 2013-119131 A

Seung-Ho Lee, Zhenyu Lu, S .; V. Babu and Egon Matijevic, "Chemical mechanical polishing of thermal oxide filming using silicon part 27, the second of the two", Journal of Mathematics, 27

However, the cerium oxide ultrafine particles described in Patent Document 1 were actually manufactured and examined by the inventor, and the polishing rate was low. Further, the surface of the polishing base material had defects (deterioration of surface accuracy, increased scratches, It has been found that the residue of the abrasive on the surface of the polishing substrate tends to occur.
This is because the method for producing ultrafine cerium oxide particles described in Patent Document 1 does not include a firing step as compared with a method for producing ceria particles including a firing step (the degree of crystallinity of ceria particles is increased by firing). Since the cerium oxide particles are only crystallized from the aqueous solution containing cerium nitrate (the aqueous solution containing cerium nitrate), the cerium oxide particles that are produced have a relatively low degree of crystallinity, and the cerium oxide does not solidify with the mother particles because it does not undergo a firing treatment. The inventor presumes that the main factor is that cerium oxide does not adhere and remains on the surface of the polishing substrate.

  In addition, 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 there is a concern that particles remain on the surface of the polishing substrate.

  Furthermore, when polishing using the silica-based composite particles having the oxide layer C described in Patent Document 2, impurities such as aluminum remain on the surface of the semiconductor device, which may adversely affect the semiconductor device. The inventor found out.

  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 has high surface accuracy (low scratch, little abrasive grains remaining on the substrate, and improved substrate Ra value. It is an object of the present invention to provide a method for producing a silica-based composite fine particle dispersion that can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate or a wiring substrate.

The inventor has intensively studied to solve the above-mentioned problems, and has completed the present invention.
The present invention includes the following (1) to (4).
(1) A method for producing a silica-based composite fine particle dispersion, comprising the following steps 1 to 3.
Step 1: Non-spherical silica fine particles having a ratio [(D2) / (DS)] of the secondary particle size (D2) to specific surface area converted particle size (DS) of greater than 1.0 are dispersed in a solvent. While stirring the silica fine particle dispersion and maintaining the temperature at 5 to 98 ° C. and the pH in the range 7.0 to 9.0, the metal salt of cerium was added continuously or intermittently to the precursor particles. The process of obtaining the precursor particle dispersion liquid containing.
Step 2: The precursor particle dispersion is dried and fired at 400 to 1,200 ° C., and the fired body obtained is subjected to the following treatment (i) or (ii) to obtain a fired body crushed dispersion liquid. Obtaining.
(I) Crushing and pulverizing by a dry method, and adding a solvent to carry out a solvent dispersion treatment.
(Ii) A solvent is added, and the mixture is crushed and pulverized by a wet process.
Step 3: A step of obtaining a silica-based composite fine particle dispersion by subjecting the calcined dispersion to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more and subsequently removing a sediment component.
(2) The method for producing a silica-based composite fine particle dispersion according to claim 1, wherein the content ratio of impurities contained in the silica fine particles is as shown in the following (a) and (b).
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr are each 100 ppm or less.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are each 10 ppm or less.
(3) A part of the surface of the non-spherical silica fine particles in which the ratio [(D2) / (DS)] of the secondary particle size (D2) to the specific surface area converted particle size (DS) is larger than 1.0 is silica. A fine silica particle dispersion coated with crystalline ceria coated on the surface.
(4) A polishing slurry containing the silica fine particle dispersion described in (3) above.

According to the present invention, even a silica film, Si wafer or difficult-to-process material can be polished at high speed, and at the same time, high surface accuracy (low scratch, low surface roughness (Ra) of substrate to be polished, etc.) It is possible to provide a method for producing a silica-based composite fine particle dispersion that can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate or a wiring substrate.
The silica-based composite fine particle dispersion obtained by the production method of the present invention is effective for planarizing the surface of a semiconductor device, and is particularly suitable for polishing a substrate on which a silica insulating film is formed.

1A is an SEM image (magnification: 100,000 times) of the silica-based composite fine particle dispersion obtained in Example 1, and FIG. 1B is a silica-based composite fine particle obtained in Example 1. 1 is a TEM image (magnification: 100,000 times) of the dispersion, and FIG. 1 (c) is an SEM image (magnification: 300,000 times) of the silica-based composite fine particle dispersion obtained in Example 1. 2 is an X-ray diffraction pattern obtained in Example 1. FIG. 3A is a SEM image (magnification: 100,000 times) of fumed silica used as a raw material in Example 1, and FIG. 3B is a TEM of fumed silica used as a raw material in Example 1. 3 (c) is an SEM image (magnification: 300,000 times) of fumed silica used as a raw material in Example 1. FIG.

The present invention will be described.
The present invention is a method for producing a silica-based composite fine particle dispersion, comprising the following steps 1 to 3.
Step 1: Non-spherical silica fine particles having a ratio [(D2) / (DS)] of the secondary particle size (D2) to specific surface area converted particle size (DS) of greater than 1.0 are dispersed in a solvent. While stirring the silica fine particle dispersion and maintaining the temperature at 5 to 98 ° C. and the pH in the range 7.0 to 9.0, the metal salt of cerium was added continuously or intermittently to the precursor particles. The process of obtaining the precursor particle dispersion liquid containing.
Step 2: The precursor particle dispersion is dried and fired at 400 to 1,200 ° C., and the fired body obtained is subjected to the following treatment (i) or (ii) to obtain a fired body crushed dispersion liquid. Obtaining.
(I) Crushing and pulverizing by a dry method, and adding a solvent to carry out a solvent dispersion treatment.
(Ii) A solvent is added, and the mixture is crushed and pulverized by a wet process.
Step 3: A step of obtaining a silica-based composite fine particle dispersion by subjecting the calcined dispersion to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more and subsequently removing a sediment component.
Hereinafter, the method for producing such a silica-based composite fine particle dispersion is also referred to as “the production method of the present invention”.

<Method for Producing Silica-Based Composite Fine Particle Dispersion of the Present Invention>
A method for producing the silica-based composite fine particle dispersion of the present invention will be described. (Hereinafter, the method for producing a silica-based composite fine particle dispersion of the present invention is also referred to as “the method of the present invention”.
The production method of the present invention includes steps 1 to 3 described below.

<Production method of the present invention>
<Step 1>
In step 1, non-spherical silica fine particles having a ratio [(D2) / (DS)] of the secondary particle size (D2) to the specific surface area converted particle size (DS) of greater than 1.0 are dispersed in the solvent. A silica fine particle dispersion is prepared.
Here, the shape of the silica fine particles contained in the silica fine particle dispersion used as a raw material is non-spherical. In this case, the ratio [(D2) / (DS)] between the secondary particle diameter (D2) and the specific surface area converted particle diameter (DS) is larger than 1.0. As the value of this ratio [(D2) / (DS)] becomes larger than 1, the shape of the silica fine particles deviates from the spherical shape. That is, the value of this ratio [(D2) / (DS)] indicates the degree to which the shape of the silica fine particles deviates from the spherical shape.
In addition, the measuring method of a secondary particle diameter (D2) and a specific surface area conversion particle diameter (DS) was mentioned later.
The upper limit value of the ratio [(D2) / (DS)] is not particularly limited, but is usually 11000 or less. The silica fine particles preferably have a specific surface area equivalent particle diameter (DS) of 5 nm to 100 nm. The silica fine particles preferably have a secondary particle diameter (D2) of 0.1 μm to 60 μm.
The silica fine particles satisfy the D2 / DS ratio, and more preferably, the secondary particle diameter is not particularly limited as long as the secondary particle diameter is within the above range, and hydrogel, xerogel, etc. are used. It is preferably dosilica. The fumed silica used as an example means an amorphous and spherical structure in which silica fine particles composed of primary particles are connected. Fumed silica can be obtained, for example, by vaporizing silicon tetrachloride and performing a gas phase reaction in a high-temperature hydrogen flame. Silica fine particles made of crushed xerogel or fumed silica usually exist as aggregated particles of primary particles. The secondary particle diameter (D2) in the present application means the particle diameter of the aggregated particles.
The measurement method of the secondary particle diameter (D2) in this application means the value measured by the dynamic light scattering method or the laser diffraction scattering method as mentioned later.
The xerogel pulverized silica here refers to a gel composed of multi-particles including air such as silica gel derived from water glass, white carbon, alkoxide and the like, and a group of particles obtained by pulverizing them. It should be noted that a crushed xerogel and fumed silica dispersed in water can be used, as well as a hydrogel crushed product that has not undergone a drying step.

Specifically, as the raw material silica fine particles used in the production method of the present invention, the value of [(D2) / (DS)] is larger than 1 and in the range of 11,000 or less, and the specific surface area equivalent particle diameter (DS ) Is preferably in the range of 5 nm to 100 nm, and non-spherical silica particles made of xerogel silica having a secondary particle diameter (D2) in the range of 0.1 μm to 60 μm.
The raw material silica fine particles used in the production method of the present invention are not particularly limited as long as they satisfy the above-mentioned secondary particle diameter and D2 / DS ranges. It is desirable to reduce the content of coarse particles. Examples of the method for reducing the coarse particles include filtration, centrifugation, and crushing, but the method is not limited thereto as long as the coarse particles can be reduced.
In the present invention, “defect” means a polishing flaw (scratch) generated in an object to be polished when the silica-based composite fine particle dispersion obtained by the production method of the present invention is applied for polishing.

When preparing a silica-based composite fine particle dispersion to be applied to polishing of semiconductor devices and the like by the production method of the present invention, silica fine particles produced by hydrolysis of alkoxysilane are dispersed in a solvent as the silica fine particle dispersion. It is preferable to use a silica fine particle dispersion. When a conventionally known silica fine particle dispersion (such as a silica fine particle dispersion prepared from water glass as a raw material) is used as a raw material, the silica fine particle dispersion is preferably acid-treated and further deionized. . In this case, 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 contained in the silica fine particles This is because it can be reduced to 100 ppm or less.
Specifically, those satisfying the following conditions (a) and (b) are preferably used as the silica fine particles in the silica fine particle dispersion, which is the raw material used in step 1.
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr are each 100 ppm or less.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are each 10 ppm or less.

The silica fine particles preferably have a specific surface area of 30 to 500 m ² / g, and more preferably 35 to 410 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 put in a measurement cell, degassed in a nitrogen gas stream at 250 ° C. for 40 minutes, and then the sample is a mixed gas of 30% by volume of nitrogen and 70% by volume of helium. Liquid nitrogen temperature is maintained in a stream of air, and nitrogen is adsorbed to the sample by equilibrium. Next, the temperature of the sample is gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that time is detected, and the specific surface area of the sample is measured using a calibration curve prepared in advance.
Such a BET specific surface area measurement method (nitrogen adsorption method) can be performed using, for example, a conventionally known surface area measurement device.
In the present invention, the specific surface area means a value obtained by such a method unless otherwise specified.

  In step 1, the silica fine particle dispersion in which the nonspherical silica fine particles are dispersed in a solvent as described above is stirred, and the temperature is maintained at 5-98 ° C. and the pH range is 7.0-9.0. A metal salt of cerium is added continuously or intermittently to obtain a precursor particle dispersion containing precursor particles.

  The dispersion medium in the silica fine particle dispersion preferably contains water, and an aqueous silica fine particle dispersion (water sol) is preferably used.

The solid concentration in the silica fine particle dispersion is preferably 1 to 40% by mass in terms of SiO ₂ . When this solid content concentration is too low, the silica concentration in the production process becomes low, and the productivity may deteriorate.

  Also, extract impurities with cation exchange resin or anion exchange resin, mineral acid, organic acid, etc., and perform deionization treatment of silica fine particle dispersion as necessary using ultrafiltration membrane etc. Can do. A silica fine particle dispersion from which impurity ions and the like are removed by deionization treatment is more preferable because a hydroxide containing silicon is easily formed on the surface. The deionization process is not limited to these.

In Step 1, the silica fine particle dispersion as described above is stirred, and the cerium metal salt is continuously or intermittently added thereto while maintaining the temperature at 5 to 98 ° C. and the pH range at 7.0 to 9.0. Add to.
The type of cerium metal salt is not limited, but cerium chloride, nitrate, sulfate, acetate, carbonate, metal alkoxide, and the like can be used. Specific examples include cerium nitrate, cerium carbonate, cerium sulfate, and cerium chloride. Of these, ceric nitrate and ceric chloride are preferred.
An aqueous solution of a metal salt of cerium nitrate or cerium chloride is added to the silica fine particle dispersion, and crystalline cerium oxide is formed from the solution that becomes supersaturated at the same time as neutralization. Since it aggregates and deposits on the surface of the fine particles and adheres firmly to the surface of the silica fine particles, it can be said that the reaction efficiency in the process is preferable.
However, sulfate ions, chloride ions, nitrate ions, etc. contained in some of the various metal salts listed above are corrosive, so cerium metal salts containing a relatively large amount of these ions (cerium sulfate) Cerium chloride, cerium nitrate, etc.) are not suitable for the main use of the silica-based composite fine particle dispersion obtained by the production method of the present invention (for polishing a semiconductor substrate or the like). In order to suppress the influence of corrosive ions such as sulfate ions, chloride ions, and nitrate ions derived from raw materials, the precursor particle dispersion obtained in step 1 of the production method of the present invention or the production method of the present invention It is preferable to wash the silica-based composite fine particle dispersion obtained in step 1 and reduce the concentration of each ion to 5 ppm or less.
In the case of carbonates such as cerium carbonate, carbonic acid is released as carbon dioxide gas in the process, and therefore it is preferable because there is little need for removal. Further, in the case of cerium alkoxide, the alkoxide is decomposed to become alcohol, and for example, volatilizes during the drying or baking in the above-mentioned step 2. Therefore, it is preferable because there is little need for removal again.

  In the production method of the present invention, cerium metal salt is added to the silica fine particles of the silica fine particle dispersion used as a raw material in terms of oxides, for example, in the range of 100: 11 to 316, whereby silica and ceria. A silica-based composite fine particle dispersion in which silica-based composite fine particles having a mass ratio of 100: 11 to 316 are dispersed in a solvent can be prepared. As described later, in the production method of the present invention, unless the ceria and silica used are dissolved and removed, the amount of ceria and silica used and the silica contained in the silica composite fine particle dispersion as the final product are used. The analysis values with the system composite fine particles are in good agreement.

The temperature at the time of stirring after adding the metal salt of cerium to the silica fine particle dispersion is preferably 5 to 98 ° C, more preferably 10 to 95 ° C. If the temperature is too low, the solubility of the silica is remarkably lowered, so that ceria crystallization is not controlled, and coarse ceria crystalline oxides are generated, which may be difficult to adhere to silica fine particles. . Furthermore, since the solubility of the silica fine particle dispersion is difficult to proceed because the solubility is too low, the particle size distribution of the silica-based composite fine particle dispersion of the present invention is increased, so that polishing characteristics such as scratches are not sufficient. It is possible.
On the other hand, if this temperature is too high, the solubility of silica is remarkably increased, and the formation of crystalline ceria oxide is considered to be suppressed. Furthermore, scale and the like are likely to occur on the reactor wall surface, which is not preferable.

Moreover, it is preferable that the time at the time of stirring is 0.5 to 24 hours, and it is more preferable that it is 0.5 to 18 hours. If this time is too short, crystalline cerium oxide cannot be formed sufficiently, which is not preferable. Conversely, even if this time is too long, the formation of crystalline cerium oxide is uneconomical because the reaction does not proceed any further. In addition, after adding the said cerium metal salt, you may age at 5-98 degreeC if desired. By aging, the reaction in which the cerium compound is deposited on the mother particles can be further promoted.
Further, when the cerium compound is deposited on the surface of the silica mother particles, it is presumed that a part of the silica mother particles is dissolved to form a cerium silicate compound. This is because when particles in the preparation process or after the preparation process are observed with an electron micrograph, fine particles of several nanometers are present on the particle surface, voids are observed in part of the inside, and the size of the silica mother particles It is clear that is smaller than the original size. Further, when the crystallite diameter is measured by X-ray diffraction at this stage, a crystallite diameter of several nanometers is confirmed, and therefore, the nanocrystals are deposited on the surface in the form of coexistence of ceria crystal particles and cerium silicate compound. It is estimated.

  Moreover, the pH range of the silica fine particle dispersion when adding a cerium metal salt to the silica fine particle dispersion and stirring is 7.0 to 9.0, but is preferably 7.6 to 8.6. . At this time, it is preferable to adjust the pH by adding an alkali or the like. A publicly known alkali can be used as an example of such an alkali. Specific examples include aqueous ammonia, alkali hydroxide, alkaline earth metal, and aqueous amines, but are not limited thereto.

  When adding the cerium metal salt to the silica fine particle dispersion, the mixture containing the silica fine particle dispersion and the cerium metal salt should be sufficiently stirred, added with an oxidizing agent (hydrogen peroxide, etc.) or air blown, etc. By taking this means, it is possible to suppress the formation of cerium single particles without the cerium compound being deposited on the surface of the silica fine particles. In addition, the said preparation liquid processed by the said means normally maintains a redox potential in a positive value.

  A dispersion containing particles (hereinafter, also referred to as “precursor particles”) that is a precursor of silica-based composite fine particles contained in the silica-based composite fine particle dispersion obtained by the production method of the present invention by such a step 1. (Hereinafter also referred to as “precursor particle dispersion”).

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

  In addition, it is preferable that the solid content concentration in a precursor particle dispersion is 1-27 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.

<Process 2>
In step 2, the precursor particle dispersion is dried and then fired at 400 to 1,200 ° C.

The method for 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.
In addition, it is recommended that the pH of the precursor particle dispersion before drying is preferably 6.0 to 7.0. It is because surface activity can be suppressed when the pH of the precursor particle dispersion before drying is 6.0 to 7.0.
After drying, the firing temperature is 400 to 1200 ° C, preferably 1050 to 1200 ° C, and more preferably 1100 to 1200 ° C. When fired in such a temperature range, crystallization of ceria proceeds sufficiently, and the silica film present on the surface of the ceria fine particles is appropriately thickened. A strong bond between the particles (silica fine particles) and the child particles (ceria fine particles) can be formed.
In addition, by firing in such a temperature range, ceria crystals of several nanometers produced in the preparation process become nuclei and cerium silicate compound diffuses to grow crystals, and Si enters the ceria crystals simultaneously with ceria crystal growth. Mold solid solution occurs. The inventors presume that when Si dissolves in the ceria crystal, the crystal is distorted, oxygen defects are generated, and the chemical reactivity with respect to the SiO ₂ film is increased to increase the polishing rate. In the baking method, interstitial solid solution of Si easily occurs in the ceria crystal. However, if Si is interstitial-type substituted, it is not limited to the baking method, and for example, a liquid phase method may be used.
Furthermore, silica separates from the cerium silicate compound as the ceria crystal grows, and this silica coats a portion of the surface of the ceria and precipitates at the interface between the mother particles and the ceria to firmly bond the ceria to the mother particles.

  As the calcination temperature exceeds 1200 ° C., ceria crystals grow abnormally, and the silica composite fine particles obtained by the production method of the present invention, which will be described later, have a tendency to cause a decrease in polishing characteristics due to excessively large particle size. . In addition, although the silica coating on the ceria particles becomes thicker, the bond between the ceria particles (child particles) and the silica particles (mother particles) becomes stronger, but the silica coating becomes excessively thick, so that the silica-based composite There is also a possibility of causing fusion of fine particles.

In step 2, the fired body obtained by firing is subjected to the following treatment (i) or (ii) to obtain a fired body crushed dispersion.
(I) Crushing and pulverizing by a dry method, and adding a solvent to carry out a solvent dispersion treatment.
(Ii) A solvent is added, and the mixture is crushed and pulverized by a wet process.
As the dry crushing / pulverizing apparatus, conventionally known apparatuses can be used, and examples thereof include an attritor, a ball mill, a vibration mill, and a vibration ball mill.
Conventionally known apparatus can be used as a wet crushing / pulverizing apparatus. For example, a batch type bead mill such as a basket mill, a horizontal type, a vertical type or an annular type continuous bead mill, a sand grinder mill, a ball mill, etc. , Rotor-stator type homogenizer, ultrasonic dispersion type homogenizer, and wet medium stirring mill (wet crusher) such as an impact pulverizer that collides fine particles in the dispersion. Examples of the beads used in the wet medium stirring mill include beads made of glass, alumina, zirconia, steel, flint stone, and the like.
In both the processes (i) and (ii), water and / or an organic solvent are used as the solvent. For example, it is preferable to use water such as pure water, ultrapure water, or ion exchange water. Moreover, although the solid content concentration of the baked body disintegration dispersion liquid obtained by the process of (i) or (ii) is not specifically limited, For example, it exists in the range of 0.3-50 mass%. Is preferred. Of the treatments (i) or (ii), the wet treatment of (ii) is more preferably used in practice. By performing the crushing treatment in this way, coarse particles that cause defects can be reduced while adjusting to a desired particle diameter.

  The manufacturing method of the present invention further includes a step 3 described below.

<Step 3>
In Step 3, the fired body disintegrated dispersion obtained in Step 2 is centrifuged at a relative centrifugal acceleration of 300 G or more, and subsequently the sediment component is removed to obtain a silica-based composite fine particle dispersion. Classifies the fired body pulverized dispersion by centrifugation. The relative centrifugal acceleration in the centrifugation process is set to 300 G or more. After the centrifugal separation treatment, the precipitated components can be removed to obtain a silica-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.
Here, the relative centrifugal acceleration is expressed as a ratio of the gravitational acceleration of the earth as 1G.
In step 3, it is necessary to provide a centrifugal separation process that satisfies the above conditions. When the centrifugal acceleration does not satisfy the above conditions, coarse particles remain in the silica-based composite fine particle dispersion. Cause it to occur.

  You may repeat the process performed at the process 3 twice or more. It is because the coarse particle which generate | occur | produced in the drying and baking process can be reduced effectively by performing it repeatedly, and a defect can be reduced. Further, the coarse particles cause clogging of the polishing pad at the time of polishing, and it becomes difficult to feed the polishing slurry continuously, thereby deteriorating the stability of the polishing rate. Therefore, by removing the coarse particles, the fluidity of the slurry between the polishing pad and the substrate is improved, and the stability of the polishing rate is increased.

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

  By such a production method of the present invention, a silica-based composite fine particle dispersion can be obtained.

By the production method of the present invention, a silica-based composite fine particle dispersion described below can be produced.
The silica-based composite fine particle dispersion has child particles mainly containing crystalline ceria on the surface of mother particles mainly containing amorphous silica, and further has a silica coating on the surface of the child particles. A silica-based composite fine particle dispersion containing silica-based composite fine particles having an average particle diameter of 50 nm to 350 nm having the following features [1] to [3].
[1] The silica-based composite fine particles have a mass ratio of silica and ceria of 100: 11 to 316.
[2] When the silica-based composite fine particles are subjected to X-ray diffraction, only the ceria crystal phase is detected.
[3] In the silica-based composite fine particles, the minor axis / major axis ratio measured by an image analysis method is 0.80 or less.

In the dispersion of the present invention, it is preferable that the content ratio of impurities contained in the silica-based composite fine particles is as follows (a) and (b).
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr are each 100 ppm or less.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are each 10 ppm or less.

  If desired, the silica-based composite fine particle dispersion obtained by the production method of the present invention has a flow rate before cation colloid titration when the pH value is in the range of 3 to 8, that is, when the titer is zero. The potential is preferably a negative potential. This is because the cerium silicate compound produced in the preparation step is separated in the firing step and a part or all of the surface of the silica-based composite fine particles is covered with silica. This is because when the flow potential is maintained at a negative potential, it is difficult for the abrasive grains (silica-based composite fine particles) to remain on the polishing substrate that also exhibits a negative surface potential.

  Hereinafter, the silica-based composite fine particles contained in the silica-based composite fine particle dispersion obtained by the production method of the present invention are also referred to as “composite fine particles obtained by the production method of the present invention”.

  The composite fine particles obtained by the production method of the present invention will be described.

<Mother particles>
In the composite fine particles obtained by the production method of the present invention, the mother particles are mainly composed of amorphous silica.

  The silica fine particles contained in the silica fine particle dispersion used as a raw material in step 1 of the production method of the present invention serve as the mother particles of the composite fine particles. Whether the silica fine particles are amorphous can be confirmed, for example, by the following method. The dispersion liquid (silica microparticle dispersion liquid) containing the mother particles (silica microparticles) is dried and then pulverized using a mortar. For example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Corporation) is used. When an X-ray diffraction pattern is obtained, the peak of crystalline silica such as Cristobalite does not appear. From this, it can be confirmed that the silica contained in the mother particles (silica fine particles) is amorphous.

The “main component” means that the content is 90% by mass or more. That is, in the mother particles, the content of amorphous silica is 90% by mass or more. The content is preferably 95% by mass or more, more preferably 98% by mass or more, and more preferably 99.5% by mass or more.
In the following description of the present invention, the term “main component” is used in this sense.

The mother particles are mainly composed of amorphous silica and may contain other materials such as crystalline silica and impurity elements.
For example, in the mother particle (silica fine particle), each element of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr (hereinafter referred to as “specific impurity group 1”). In some cases) is preferably 100 ppm or less. Furthermore, it is preferably 50 ppm or less, more preferably 25 ppm or less, still more preferably 5 ppm or less, and even more preferably 1 ppm or less. The content of each element of U, Th, Cl, NO ₃ , SO ₄ and F (hereinafter sometimes referred to as “specific impurity group 2”) in the base particles (silica fine particles) is 10 ppm or less. Preferably there is.
Generally, silica fine particles prepared using water glass as a raw material contain about a few thousand ppm in total of the specific impurity group 1 and the specific impurity group 2 derived from the raw water glass.
In the case of such a silica fine particle dispersion in which silica fine particles are dispersed in a solvent, it is possible to reduce the contents of the specific impurity group 1 and the specific impurity group 2 by performing ion exchange treatment. However, the specific impurity group 1 and the specific impurity group 2 remain several ppm to several hundred ppm in total. Therefore, when silica 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 silica fine particle dispersion in which silica fine particles synthesized using alkoxysilane as a raw material are dispersed in a solvent, the content of each element and each anion in the specific impurity group 1 and the specific impurity group 2 is usually Are each 20 ppm or less.
In general, fumed silica synthesized from silicon tetrachloride as a raw material has a total content of about 20 ppm of the specific impurity group 1 and the specific impurity group 2 derived from the raw material silicon tetrachloride even in a powder state. is there.
In the present invention, Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, NO ₃ , SO ₄ in the mother particles (silica fine particles) are used. Each of the contents of F and F is a value determined by measurement using the following method.
Na and K: atomic absorption spectroscopic analysis Ag, Al, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, Zr, U and Th: ICP (inductively coupled plasma emission spectroscopic analysis)
・ Cl: Potentiometric titration method ・ NO ₃ , SO ₄ and F: Ion chromatograph

  As described later, the average particle size of the silica-based composite fine particles in the silica-based composite fine particle dispersion obtained by the production method of the present invention is 50 nm to 350 nm (depending on the value measured by the dynamic light scattering method or the laser diffraction scattering method). The average particle diameter of the mother particles (silica fine particles) is usually smaller than 350 nm.

The average particle diameter of the silica fine particles contained in the silica fine particle dispersion used as a raw material in the production method of the present invention means a value measured by a dynamic light scattering method or a laser diffraction scattering method. Specifically, it means a value obtained by measurement by the following method. Silica fine particles are dispersed in water or the like to obtain a silica fine particle dispersion, and then the silica fine particle dispersion is separated from a particle size measuring device by a known dynamic light scattering method (for example, Microtrack UPA device manufactured by Nikkiso Co., Ltd., Measurement is performed using a measurement apparatus (PAR-III manufactured by Otsuka Electronics Co., Ltd.) or a laser diffraction scattering method (for example, LA-950 manufactured by HORIBA).
In addition, a measuring apparatus is selectively used according to the objective of each process, the assumed particle diameter, and a particle size distribution. Specifically, PAR-III is used for the raw material monodisperse silica fine particles having a uniform particle size of about 100 nm or less, and monodisperse raw silica fine particles having a large size of 100 nm or more are measured with LA-950, and the micrometer is obtained by crushing. It is preferable to use Microtrac UPA or LA-950 in the crushing process in which the particle diameter varies widely from 1 to nanometer.

  As the silica fine particles contained in the silica fine particle dispersion used as a raw material in Step 1 of the production method of the present invention, non-spherical silica fine particles are preferably used. Examples of the non-spherical shape include a bowl shape, a short fiber shape, a tetrahedron shape (triangular pyramid shape), a hexahedron shape, an octahedron shape, a plate shape, and an indefinite shape. Such non-spherical silica fine particles may have a ridge-like protrusion on the surface or a confetti-like shape, but are not limited thereto.

The shape of the silica fine particles contained in the silica fine particle dispersion used as a raw material in the step 1 is preferably non-spherical. In this case, the ratio [(D2) / (DS)] between the secondary particle diameter (D2) and the specific surface area converted particle diameter (DS) is larger than 1.0. As the value of this ratio [(D2) / (DS)] increases, the shape of the silica fine particles deviates from the spherical shape. That is, the value of this ratio [(D2) / (DS)] indicates the degree to which the shape of the silica fine particles deviates from the spherical shape.
In addition, the measuring method of a secondary particle diameter (D2) and a specific surface area conversion particle diameter (DS) is described in description of the Example mentioned later.
The upper limit of this ratio [(D2) / (DS)] may be 11000. When such non-spherical silica mother particles are used as raw materials, the silica-based composite fine particles also become non-spherical, and the non-spherical particles have a large contact area with the substrate, so that the polishing rate increases. Further, by selecting the shape of the silica mother particles, the shape of the silica-based composite fine particles can be easily controlled.

  The composite fine particles contained in the silica-based composite fine particle dispersion obtained by the production method of the present invention have child particles on the surface of the mother particles as described above. Here, it is preferable that the child particle is bonded to the surface of the mother particle. Further, for example, the child particles that are entirely covered with the silica coating may be bonded to the mother particles through the silica coating. Even such an embodiment is an embodiment in which child particles are present on the surface of the mother particle, and is included in the technical scope of the present invention.

  In the composite fine particles, the child particles are mainly composed of crystalline ceria.

  The fact that the child particles are crystalline ceria is, for example, that the dispersion liquid of the present invention is dried and then pulverized using a mortar, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Corporation). In the X-ray diffraction pattern obtained by (1), only the ceria crystal phase is detected. Examples of the ceria crystal phase include Ceriaite.

The child particles are mainly composed of crystalline ceria (crystalline Ce oxide), and may contain other elements, for example, elements other than cerium.
However, as described above, when the composite fine particles of the present invention are subjected to X-ray diffraction, only the ceria crystal phase is detected. That is, even if a crystal phase other than ceria is included, its content is small, and thus it is outside the detection range by X-ray diffraction.
The definition of “principal component” is as described above.

  If the said child particle is crystalline ceria, it can be used conveniently. As such crystalline ceria, for example, when the composite fine particles of the present invention are measured by X-ray diffraction, the crystalline ceria has a crystallite diameter of 10 to 25 nm on the (111) plane (near 2θ = 28 degrees). A range is desirable. The larger the ceria crystallite size, the larger the contact area with the substrate and the faster the polishing speed.However, if the ceria crystal is too large, the ceria crystals fall off from the mother particles during crushing or polishing. The speed is reduced. If it is the said range, a ceria particle will fully contact and it can prevent a ceria particle falling off.

The crystallite diameter of the (111) plane of crystalline ceria (around 2θ = 28 degrees) means a value obtained by the method described below.
First, the composite fine particles of the present invention are pulverized using a mortar, and an X-ray diffraction pattern is obtained by using, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Corporation). Then, the half width of the peak of the (111) plane in the vicinity of 2θ = 28 degrees in the obtained X-ray diffraction pattern is measured, and the crystallite diameter can be obtained by the following Scherrer equation.
D = Kλ / βcos θ
D: Crystallite diameter (angstrom)
K: Scherrer constant λ: X-ray wavelength (1.7789 angstrom, Cu lamp)
β: Half width (rad)
θ: Reflection angle

  The size of the child particles is smaller than that of the mother particles, preferably an average particle diameter of 11 to 26 nm, and more preferably 12 to 23 nm. The size of the child particles is a value obtained by measuring the average particle diameter of any 50 child particles in a photograph projection view enlarged 300,000 times using a transmission electron microscope, and simply averaging them. means.

<Silica coating>
The composite fine particles of the present invention have the child particles on the surface of the mother particles, and further have a silica coating on the surface of the child particles. Here, it is preferable that the child particles are bonded to the surface of the mother particles and further has a silica coating covering them. That is, it is preferable that the silica coating covers a part or the whole of the composite particles formed by bonding the child particles to the surface of the mother particles. Therefore, a silica coating is present on the outermost surface of the composite fine particles of the present invention.

In the image (TEM image) obtained by observing the composite fine particles contained in the silica-based composite fine particle dispersion obtained by the production method of the present invention using a transmission electron microscope, the image of the child particles is deep on the surface of the mother particles. Although it appears, a silica coating appears as a relatively thin image outside the child particle, that is, on the surface side of the composite fine particle of the present invention. Further, it is preferable that the child particles (ceria fine particles) are bonded to the mother particles (silica fine particles), and the child particles whose silica coating covers all or part of the mother particles are interposed via the silica coating. May be bonded to.
Further, when the composite fine particles are subjected to EDS analysis to obtain an element distribution, a portion with a high Ce concentration appears on the surface side of the particles, but a portion with a high Si concentration appears on the outer side.
Further, when EDS measurement was performed by selectively applying an electron beam to the silica coating portion specified by the transmission electron microscope as described above, the Si atom number% and Ce atom number% of the part were obtained. It can be confirmed that several percent is very high. Specifically, the ratio of Si atom number% to Ce atom number% (Si atom number% / Ce atom number%) is 0.9 or more.

Such a silica coating is considered to promote the bond (force) between the child particles (ceria crystal particles) and the mother particles (silica fine particles). Thus, for example, in the step of obtaining the dispersion of the present invention, the silica-based composite fine particles obtained by firing are crushed and pulverized by a wet process to obtain a silica-based composite fine particle dispersion. It is considered that there is an effect of preventing the child particles (ceria crystal particles) from coming off from the mother particles (silica fine particles). In this case, local dropout of the child particles is not a problem, and the entire surface of the child particles may not be covered with the silica coating. It is sufficient that the child particles are strong enough not to be separated from the mother particles in the crushing / grinding process.
With such a structure, it is considered that when the dispersion liquid of the present invention is used as an abrasive, the polishing rate is high, and the surface accuracy and scratch are less deteriorated. Further, since it is crystallized, there are few —OH groups on the surface of the particles, and there is little interaction with the —OH groups on the surface of the polishing substrate.
In addition, ceria has a potential different from that of silica, a polishing substrate, and a polishing pad, and the pH decreases from a negative zeta potential in the vicinity of neutral to neutral, and has a reverse positive potential in a weakly acidic region. For this reason, it adheres to the polishing substrate or polishing pad due to the difference in the magnitude of the potential or the polarity, and tends to remain on the polishing substrate or the polishing pad. On the other hand, in the silica-based composite fine particles of the present invention, since ceria as a child particle is at least partially covered with a silica coating, the pH is maintained at a negative potential from alkaline to acidic. It is difficult for abrasive grains to remain on the pad.

  The thickness of the silica coating is generally determined from the TEM image or SEM image in terms of how the ceria child particles on the mother particles are covered with the silica coating. That is, as described above, in the TEM image, a child particle having a particle size of about 20 nm appears on the surface of the mother particle, and a silica coating appears as a relatively thin image outside the child particle. The thickness of the silica coating can be roughly determined by comparing with the size of. If the child particles can be clearly confirmed as irregularities from the SEM image and irregularities are seen in the outline of the silica-based composite fine particles from the TEM image, the thickness of the silica coating may be much less than 20 nm. It is done.

  As described above, the silica coating of the outermost layer (opposite to the mother particle side) may not completely cover the entire child particles (ceria fine particles). That is, the silica film is present on the outermost surface of the composite fine particles of the present invention, but there may be a portion where the silica film is not present. Further, there may be a portion where the base particle of the silica-based composite fine particle is exposed.

<Composite fine particles contained in silica-based composite fine particle dispersion obtained by the production method of the present invention>
As described above, the composite fine particles of the present invention have the above child particles on the surface of the mother particles.

In the composite fine particles contained in the silica-based composite fine particle dispersion obtained by the production method of the present invention, the mass ratio of silica to ceria is 100: 11 to 316, preferably 100: 30 to 316, 100: More preferably, it is 30-316, and it is further more preferable that it is 100: 110-316. The mass ratio between silica and ceria is considered to be approximately the same as the mass ratio between the mother particles and the child particles. If the amount of the child particles relative to the mother particles is too small, the mother particles may be bonded to generate coarse particles. In this case, the abrasive (polishing slurry) containing the dispersion of the present invention may cause defects (decrease in surface accuracy such as an increase in scratches) on the surface of the polishing substrate. Further, if the amount of ceria relative to silica is too large, not only is the cost high, but the resource risk increases. Furthermore, the fusion of the particles proceeds. As a result, the roughness of the substrate surface increases (deterioration of the surface roughness Ra), scratches increase, free ceria remains on the substrate, and causes such as adhesion to the waste liquid piping of the polishing apparatus. It's easy to get along.
In addition, the silica used as the object in calculating the mass ratio includes both the following (I) and (II).
(I) A silica component constituting the mother particle.
(II) A silica component contained in a silica coating covering composite fine particles formed by binding child particles (ceria component) to mother particles.

The content (mass%) of silica (SiO ₂ ) and ceria (CeO ₂ ) in the composite fine particles contained in the silica-based composite fine particle dispersion obtained by the production method of the present invention is the silica obtained by the production method of the present invention. The solid content concentration of the dispersion liquid of the system composite fine particles (the dispersion liquid of the present invention) is determined by weighing 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 analysis, and converted to CeO ₂ mass%. Then, assuming that the components other than CeO ₂ constituting the composite fine particles of the present invention are SiO ₂ , SiO ₂ mass% can be calculated.
In the production method of the present invention, the mass ratio of silica and ceria can be calculated from the amount of silica source material and ceria source material used when the dispersion of the present invention is prepared. This can be applied when ceria and silica are not dissolved and removed, and in such a case, the amount of ceria or silica used and the analytical value are in good agreement.

The composite fine particles contained in the silica-based composite fine particle dispersion obtained by the production method of the present invention are those in which particulate crystalline ceria (child particles) are bonded to the surface of the silica fine particles (parent particles) by sintering or the like. Since it is, it has an uneven surface shape.
That is, it is preferable that at least one (preferably both) of the mother particle and the child particle is sinter-bonded and firmly bonded at their contact points. However, the child particles covered with the silica coating may be bonded to the mother particles through the silica coating.

The shape of the composite fine particles is not particularly limited, but it is preferable in practice to have an anisotropic shape. The anisotropic shape means that the minor axis / major axis ratio measured by the method described later is smaller than 1.
If the shape is anisotropic, a large contact area with the substrate can be obtained, so that polishing energy can be efficiently transmitted to the substrate. Therefore, the polishing rate is high. Further, since the polishing pressure per particle is lower than that of a single particle, there is little scratching.

  In the composite fine particles, the number ratio of particles having a minor axis / major axis ratio measured by an image analysis method of 0.80 or less (preferably 0.67 or less) is preferably 50% or more. Here, particles having a minor axis / major axis ratio measured by an image analysis method of 0.80 or less are considered to be of a particle-binding type in principle.

  A method for measuring the minor axis / major axis ratio by the image analysis method will be described. In a photograph projection view obtained by photographing a composite fine particle of the present invention at a magnification of 250,000 times (or 500,000 times) with a transmission electron microscope, the maximum diameter of the particles is taken as the major axis, and the length is measured. The value is taken as the major axis (DL). Further, a point that bisects the major axis on the major axis is determined, two points where a straight line perpendicular to the major axis intersects the outer edge of the particle are obtained, and a distance between the two points is measured to obtain a minor axis (DB). From this, the minor axis / major axis ratio (DB / DL) is obtained. Then, the number ratio (%) of particles having a minor axis / major axis ratio of 0.80 or less in any 50 particles observed in the photographic projection diagram is obtained.

  In the composite fine particles, the number ratio of particles having a minor axis / major axis ratio of 0.80 or less (preferably 0.67 or less) is preferably 55% or more, and more preferably 65% or more. The composite fine particles of the present invention in this range are preferable because the polishing rate becomes high when used as an abrasive.

  The composite fine particles preferably have the anisotropic shape described above, but may have other shapes, for example, spherical particles.

The composite fine particles preferably have a specific surface area of 4 to 100 m ² / g, and more preferably 30 to 60 m ² / g.

The composite fine particles preferably have an average particle size of 50 nm to 350 nm, and more preferably 170 nm to 260 nm. When the average particle size of the composite fine particles of the present invention is in the range of 50 nm to 350 nm, it is preferable because the polishing rate becomes high when applied as an abrasive.
The average particle diameter of the composite fine particles means a value measured by a dynamic light scattering method or a laser diffraction scattering method. Specifically, it means a value obtained by measurement by the following method. The composite fine particles of the present invention are dispersed in water, and this composite fine particle dispersion is used as a particle size measuring device by a known dynamic light scattering method (for example, Nikkiso Co., Ltd. Microtrac UPA device or Otsuka Electronics PAR-III). ) Or a measurement apparatus using a laser diffraction scattering method (for example, LA-950 manufactured by HORIBA).

In the composite fine particles, the content of each element of the specific impurity group 1 is preferably 100 ppm or less. Furthermore, it is preferably 50 ppm or less, more preferably 25 ppm or less, still more preferably 5 ppm or less, and even more preferably 1 ppm or less. Moreover, it is preferable that the content rate of each element of the said specific impurity group 2 in the composite fine particle of this invention is 10 ppm or less, respectively. As the method for reducing 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, the method described for the mother particles (silica fine particles) can be applied.
Note that the content of each element of the specific impurity group 1 and the specific impurity group 2 in the composite fine particle is a value obtained by measurement using an ICP (inductively coupled plasma emission spectrometer).

<Dispersion of the present invention>
The dispersion liquid of the present invention will be described.
The dispersion of the present invention includes a silica-based composite fine particle dispersion obtained by the production method of the present invention. Of course, the dispersion of the present invention may be the silica-based composite fine particle dispersion itself.
The dispersion liquid of the present invention is such that the composite fine particles of the present invention as described above are dispersed in a dispersion solvent.

  The dispersion of the present invention contains water and / or an organic solvent as a dispersion solvent. For example, water such as pure water, ultrapure water, or ion exchange water is preferably used as the dispersion solvent. Furthermore, the dispersion of the present invention may contain one or more selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster, and a pH buffer as an additive.

  Examples of the dispersion solvent provided with the dispersion of the present invention include alcohols such as methanol, ethanol, isopropanol, n-butanol, and methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Ketones such as N; N-dimethylformamide, amides such as N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, and 3,4-dihydro-2H-pyran Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxy Glycol ether acetates such as ethyl acetate; esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and ethylene carbonate; aromatic hydrocarbons such as benzene, toluene, xylene; hexane, heptane, isooctane, Aliphatic hydrocarbons such as cyclohexane; Halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane and chlorobenzene; Sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone, N-octyl- Organic solvents such as pyrrolidones such as 2-pyrrolidone can be used. These may be used by mixing with water.

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

  When the pH of the dispersion of the present invention is in the range of 3 to 8, before the start of cationic colloid titration, that is, when the titer is zero, the flow potential is negative. Is preferred. This is because when this flow potential is maintained at a negative potential, it is difficult for abrasive grains (silica-based composite fine particles) to remain on the polishing substrate that also exhibits a negative surface potential.

<Slurry for polishing>
The liquid containing the dispersion of the present invention can be preferably used as a polishing slurry (hereinafter also referred to as “the polishing slurry of the present invention”). In particular, it can be suitably used as a polishing slurry for planarizing a semiconductor substrate on which a SiO ₂ insulating film is formed.

  The polishing slurry of the present invention has a high polishing rate when polishing a semiconductor substrate and the like, and is excellent in effects such as few scratches (scratches) on the polishing surface and little residual abrasive grains on the substrate during polishing.

  The polishing slurry of the present invention contains water and / or an organic solvent as a dispersion solvent. For example, water such as pure water, ultrapure water, or ion exchange water is preferably used as the dispersion solvent. Furthermore, the polishing slurry of the present invention may contain one or more selected from the group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster and a pH buffer as an additive.

<Polishing accelerator>
In the polishing slurry according to the present invention, a conventionally known polishing accelerator can be used as necessary, although it varies depending on the type of material to be polished. Examples of such include hydrogen peroxide, peracetic acid, urea peroxide 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, nitric acid, phosphoric acid, oxalic acid and hydrofluoric acid, organic acids such as acetic acid, or sodium, potassium, ammonium and amine salts of these acids And the like. In the case of a polishing composition containing these polishing accelerators, when polishing a material to be polished consisting of composite components, the polishing rate is accelerated for a specific component of the material to be polished, thereby finally achieving flat polishing. You can get a plane.

  When the polishing slurry according to the present invention contains a polishing accelerator, the content thereof is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass.

<Surfactant and / or hydrophilic compound>
In order to improve the dispersibility and stability of the polishing slurry, a cationic, anionic, nonionic or amphoteric surfactant or a hydrophilic compound can be added. Both the surfactant and the hydrophilic compound have an action of reducing a contact angle to the surface to be polished and 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 carboxylate, sulfonate, sulfate ester salt and phosphate ester salt. Examples of the carboxylate salt include soap, N-acyl amino acid salt, polyoxyethylene or polyoxypropylene alkyl ether carboxyl. Acid salt, acylated peptide; as sulfonate, alkyl sulfonate, alkyl benzene and alkyl naphthalene sulfonate, naphthalene sulfonate, sulfosuccinate, α-olefin sulfonate, N-acyl sulfonate; sulfate ester Salts include sulfated oil, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfates, alkyl amide sulfates; phosphate ester salts such as alkyl phosphates, polyoxyethylene or polyoxypropyls. Can pyrene alkyl allyl ether phosphates.

  As cationic surfactant, aliphatic amine salt, aliphatic quaternary ammonium salt, benzalkonium chloride salt, benzethonium chloride, pyridinium salt, imidazolinium salt; as amphoteric surfactant, carboxybetaine type, sulfobetaine type, Mention may be made of aminocarboxylates, imidazolinium betaines, lecithins, alkylamine oxides.

  Nonionic surfactants include ether type, ether ester type, ester type and nitrogen-containing type. Ether type includes polyoxyethylene alkyl and alkylphenyl ether, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene poly Examples include oxypropylene block polymer, polyoxyethylene polyoxypropylene alkyl ether, ether ester type, glycerin ester polyoxyethylene ether, sorbitan ester polyoxyethylene ether, sorbitol ester polyoxyethylene ether, ester type, Polyethylene glycol fatty acid ester, glycerin ester, polyglycerin ester, sorbitan ester, propylene glycol ester , Sucrose esters, nitrogen-containing type, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amide, and the like. In addition, a fluorine-type surfactant etc. are mentioned.

  As the surfactant, an anionic surfactant or a nonionic surfactant is preferable, and as the salt, ammonium salt, potassium salt, sodium salt and the like can be mentioned, and ammonium salt and potassium salt are particularly preferable.

  Further, other surfactants and hydrophilic compounds 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, 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 Ethers such as recall, alkyl polypropylene glycol alkyl ether, alkyl polypropylene glycol alkenyl ether, alkenyl polypropylene glycol; polysaccharides such as alginic acid, pectic acid, carboxymethyl cellulose, curdlan and pullulan; amino acid salts such as glycine ammonium salt and glycine sodium salt; Polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), poly Acrylic acid, polyacrylamide, aminopolyacrylamide, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, Polycarboxylic acids such as lyamidic acid, polyamic acid ammonium salt, polyamic acid sodium salt and polyglyoxylic acid and their salts; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein; methyl tauric acid ammonium salt, methyl tauric acid sodium salt , Methyl sulfate sodium salt, ethyl ammonium sulfate salt, butyl ammonium sulfate salt, vinyl sulfonic acid sodium salt, 1-allyl sulfonic acid sodium salt, 2-allyl sulfonic acid sodium salt, methoxymethyl sulfonic acid sodium salt, ethoxymethyl sulfonic acid ammonium salt Salts, sulfonic acids such as 3-ethoxypropylsulfonic acid sodium salt and the salts thereof; propionamide, acrylamide, methylurea, nicotinamide, succinic acid amide and sulfite Examples thereof include amides such as an amide.

  Note that when the substrate to be polished is a glass substrate or the like, any surfactant can be suitably used. However, in the case of a silicon substrate for a semiconductor integrated circuit or the like, alkali metal, alkaline earth In the case where the influence of contamination by a metal or a halide is disliked, it is desirable to use an acid or an ammonium salt surfactant.

  When the polishing slurry according to the present invention contains a surfactant and / or a hydrophilic compound, the total content is preferably 0.001 to 10 g in 1 L of the polishing slurry. It is more preferable to set it as 01-5g, and it is especially preferable to set it as 0.1-3g.

  In order to obtain a sufficient effect, the content of the surfactant and / or the hydrophilic compound is preferably 0.001 g or more in 1 L of the polishing slurry, and preferably 10 g or less from the viewpoint of preventing the polishing rate from being lowered.

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

<Heterocyclic compound>
Regarding the polishing slurry of the present invention, when a metal is contained in the substrate to be polished, a heterocyclic compound is formed for the purpose of suppressing the erosion of the substrate to be polished by forming a passive layer or a dissolution suppressing layer on the metal. May be included. Here, the “heterocyclic compound” is a compound having a heterocyclic ring containing one or more heteroatoms. A hetero atom means an atom other than a carbon atom or a hydrogen atom. A heterocycle means a cyclic compound having at least one heteroatom. A heteroatom means only those atoms that form part of a heterocyclic ring system, either external to the ring system, separated from the ring system by at least one non-conjugated single bond, Atoms that are part of a further substituent of are not meant. Preferred examples of the hetero atom include, but are not limited to, a nitrogen atom, a sulfur atom, an oxygen atom, a selenium atom, a tellurium atom, a phosphorus atom, a silicon atom, and a boron atom. As examples 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 can be mentioned, but is not limited thereto.

  About content in the case of mix | blending a heterocyclic compound with the slurry for polishing which concerns on this invention, it is preferable that it is 0.001-1.0 mass%, and it is more that it is 0.001-0.7 mass%. Preferably, it is 0.002-0.4 mass%.

<PH adjuster>
In order to enhance the effects of the above additives, an acid or a base can be added as necessary to adjust the pH of the polishing composition.

  When adjusting the polishing slurry to pH 7 or higher, an alkaline one is used as a pH adjuster. Desirably, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, tetramethylamine are used.

  When the polishing slurry is adjusted to a pH of less than 7, an acidic one is used as a pH adjuster. 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 buffering agent>
In order to keep the pH value of the polishing slurry constant, a pH buffer may be used. Examples of the pH buffering agent that can be used include phosphates and borates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium tetraborate tetrahydrate, and organic acids.

  Examples of the dispersion solvent for the polishing slurry of the present invention include alcohols such as methanol, ethanol, isopropanol, n-butanol, and methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Ketones such as N; N-dimethylformamide, amides such as N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, and 3,4-dihydro-2H-pyran Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-but Glycol ether acetates such as ciethyl acetate; Esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate and ethylene carbonate; Aromatic hydrocarbons such as benzene, toluene and xylene; Hexane, heptane and isooctane Aliphatic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone, N-octyl Organic solvents such as pyrrolidones such as -2-pyrrolidone can be used. These may be used by mixing with water.

  The solid content concentration contained in the polishing slurry of the present invention is not particularly limited as long as the required polishing rate is obtained. Usually, it is preferable that it exists in the range of 0.3-50 mass%. If this solid content concentration is too low, the polishing rate may decrease.

When the cation colloid titration is performed, the silica-based composite fine particle dispersion obtained by the production method of the present invention has a flow potential change amount (ΔPCD) represented by the following formula (1) and a cation colloid titration liquid in a knick. It is preferable that a flow potential curve having a ratio (ΔPCD / V) to the addition amount (V) of −110.0 to −15.0 is obtained.
ΔPCD / V = (I−C) / V (1)
C: Streaming potential (mV) at the nick
I: Streaming potential (mV) at the starting point of the streaming potential curve
V: Amount of the colloid titration solution added in the nick (ml)

  Here, the cation colloid titration is performed by adding the cation colloid titration liquid 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 polydiallyldimethylammonium chloride solution is used as the cationic colloid titrant.

The flow potential curve obtained by the cation colloid titration is a graph in which the addition amount (ml) of the cation titrant is taken on the X axis and the flow potential (mV) of the dispersion of the present invention is taken on the Y axis.
A knick is a point (inflection point) where the streaming potential changes suddenly in the streaming potential curve obtained by cationic colloid titration. The flow potential at this inflection point is C (mV), and the addition amount of the cation colloid titrant at point A is V (ml).
The streaming potential in the silica-based composite fine particle dispersion before titration is the starting point of the streaming potential curve, and the starting point is usually the point where the addition amount of the cationic colloid titrating solution is zero. Further, the flow potential at the starting point is I (mV).

  When the value of ΔPCD / V is −110.0 to −15.0, when the silica-based composite fine particle dispersion obtained by the production method of the present invention is used as an abrasive, the polishing rate of the abrasive is More improved. This ΔPCD / V reflects the coating condition of the silica coating on the surface of the composite fine particles obtained by the production method of the present invention and / or the exposure condition of the child particles on the surface of the composite fine particles or the presence of silica that is easily detached. Conceivable. When the value of ΔPCD / V is within the above range, the present inventor presumes that the child particles are hardly detached at the time of wet pulverization / pulverization and the polishing rate is high. Conversely, if the absolute value of ΔPCD / V is larger than −110.0, the surface of the composite fine particles is entirely covered with a silica coating, so that it is difficult for the child particles to fall off during the crushing and pulverization process. Sometimes the silica is difficult to desorb and the polishing rate decreases. On the other hand, when the absolute value is smaller than -15.0, it is considered that dropout is likely to occur. The inventor presumes that within the above range, the surface of the child particles is appropriately exposed at the time of polishing so that the child particles are not dropped off and the polishing rate is further improved. ΔPCD / V is more preferably −100.0 to −15.0, and further preferably −100.0 to −20.0.

  When the pH value of the silica-based composite fine particle dispersion obtained by the production method of the present invention is in the range of 3 to 8, before the start of cationic colloid titration, that is, when the titer is zero, the streaming potential is zero. Is preferably a negative potential. This is because when this flow potential is maintained at a negative potential, it is difficult for abrasive grains (silica-based composite fine particles) to remain on the polishing substrate that also exhibits a negative surface potential.

In addition, when performing the crushing and grinding | pulverization by wet of the process 2 * (ii) of the manufacturing method of this invention, crushing and grinding | pulverization by wet are performed, maintaining the pH of a solvent at 8.6-10.8. Is preferred. When the pH is maintained in this range, when the cationic colloid titration is performed, the change in streaming potential (ΔPCD) represented by the above formula (1) and the addition amount (V) of the cationic colloid titrant in the knick A silica-based composite fine particle dispersion in which a flow potential curve having a ratio (ΔPCD / V) of -110.0 to -15.0 is obtained can be finally obtained more easily.
That is, it is preferable to perform pulverization and pulverization to such an 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 a preferred embodiment is used as an abrasive, the polishing rate is further improved. About this, the inventor is that the silica coating on the surface of the composite fine particles of the present invention is moderately thin, and / or the child particles are exposed to a part of the surface of the composite fine particles, the polishing rate is further improved, In addition, it is estimated that the falling of ceria particles can be controlled. Further, since the silica coating is thin or peeled off, it is estimated that the child particles are easily detached to some extent during polishing. ΔPCD / V is more preferably −100.0 to −15.0, and further preferably −100.0 to −20.0.

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

<Experiment 1>
First, 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.

[Analysis of ingredients]
[Silica fine particles (mother particles)]
The SiO ₂ weight of fumed silica described later was determined by weighing after performing a 1000 ° C. loss reduction. Further, the SiO ₂ by weight of the silica fine particle dispersion, in the case of the silica fine particles of sodium silicate as a raw material was determined by weighing performed 1000 ° C. ignition loss. In the case of silica fine particles using alkoxysilane as a raw material, the silica fine particle dispersion was dried at 150 ° C. for 1 hour and then weighed.

[Silica composite fine particles]
The content rate of each element shall be measured with the following method.
First, about 1 g (solid content: 20% by mass) of a sample composed of a silica-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. Once dry, add a small amount of water and 50 ml of nitric acid to dissolve and place in a 100 ml volumetric flask and add water to make 100 ml. In this solution, Na and K are measured with an atomic absorption spectrometer (for example, Z-2310, manufactured by Hitachi, Ltd.). Next, the operation of collecting 10 ml of the liquid separation from the solution in 100 ml into the 20 ml volumetric flask is repeated 5 times to obtain 5 10 ml of the liquid separation. Using this, standard addition method for Al, Ag, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, Zr, U and Th with an ICP plasma emission spectrometer (for example, SPS5520 manufactured by SII) Measure with. Here, a blank is also measured by the same method, and the blank is subtracted and adjusted to obtain measured values for each element.
Hereinafter, unless otherwise specified, the content (content) of the components of Na, Al, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U and Th in the present invention is as follows. The value obtained by measurement by such a method is meant.

The content rate of each anion shall be measured by the following method.
<Cl>
Acetone is added to a 20 g sample (solid content of 20% by mass) composed of a silica-based composite fine particle dispersion to adjust to 100 ml, and 5 ml of acetic acid and 4 ml of 0.001 molar sodium chloride solution are added to this solution to form a 0.002 molar silver nitrate solution. The analysis is carried out by potentiometric titration (Kyoto Electronics: potentiometric titrator AT-610).
Separately, as a blank measurement, 5 ml of acetic acid and 4 ml of 0.001 molar sodium chloride solution were added to 100 ml of acetone, and titration was performed when titrating with 0.002 molar silver nitrate solution, and titration when using a sample. Was subtracted from the sample to obtain a titration amount of the sample.

<NO ₃ , SO ₄ , F>
A 5 g sample (solid content of 20% by mass) composed of a silica-based composite fine particle dispersion is diluted with water to 100 ml, and centrifuged at 4000 rpm for 20 minutes in a centrifuge (HIMAC CT06E manufactured by Hitachi), and the precipitated components are separated. The liquid obtained by the removal was analyzed with an ion chromatograph (ICS-1100, manufactured by DIONEX).

<SiO ₂ , CeO ₂ >
When obtaining the content of silica and ceria in the silica-based composite fine particles, first, the solid content concentration of the dispersion of the silica-based composite fine particles is determined by weighing at 1000 ° C. and by weight reduction. Next, Ce is measured by a standard addition method using an ICP plasma emission spectrometer (for example, SPS5520 manufactured by SII) in the same manner as Al to Th and the like, and CeO ₂ mass% is calculated from the obtained Ce content. . Then, assuming that the components other than CeO ₂ constituting the composite fine particles of the present invention are SiO ₂ , SiO ₂ mass% is calculated.
The content of each element or each anion in the silica fine particles (mother particles) is determined by using the silica fine particle dispersion instead of the silica composite fine particle dispersion in the method for analyzing silica-based composite fine particles. went.

[X-ray diffraction method, measurement of crystallite diameter]
In accordance with the method described above, the silica-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 X-ray diffraction was performed. An X-ray diffraction pattern was obtained by an apparatus (RINT1400, manufactured by Rigaku Corporation), and a crystal form was specified.
Further, as described above, the half width of the peak of the (111) plane (2θ = 28 degrees) near 2θ = 28 degrees in the obtained X-ray diffraction pattern was measured, and the crystallite diameter was calculated according to Scherrer's equation. Asked.

<Average particle diameter (D2)>
For the silica fine particle dispersions and silica-based composite fine particle dispersions obtained in the examples and comparative examples, the average particle diameter (D2) of the particles contained therein was measured by the method described above.
Specifically, LA950 made by HORIBA was used as the silica mother particle, and a Microtrac UPA device made by Nikkiso Co., Ltd. was used for the silica composite fine particles.

<Specific surface area equivalent particle diameter (DS)>
The specific surface area (Sa) of the silica fine particles was measured by the aforementioned BET specific surface area measurement method (nitrogen adsorption method), and DS was determined by substituting this Sa into the following equation.
DS = 6000 / (ρ × Sa)
Here, ρ is the density of the sample, and 2.2 in the case of the silica sample.
In addition, the value of the ratio [(D2) / (DS)] of the secondary particle diameter (D2) and the specific surface area converted particle diameter (DS) is the secondary particle diameter (D2) and the specific surface area converted particle diameter (DS). Both units were calculated in the same way.

<Short diameter / Long diameter ratio>
About each particle | grains which the silica particle dispersion liquid and silica type composite particle dispersion liquid which were obtained in the Example and the comparative example contain, it is a magnification using a transmission electron microscope (Transmission Electron Microscope; Hitachi Ltd. make, model number: S-5500). In a photographic projection obtained by taking a photograph at 250,000 times (or 500,000 times), the maximum diameter of the particles was taken as the major axis, the length was measured, and the value was taken as the major diameter (DL). Further, a point that bisects the major axis on the major axis was determined, two points where a straight line perpendicular to the major axis intersected the outer edge of the particle were determined, and the distance between the two points was measured to obtain a minor axis (DB). And ratio (DB / DL) was calculated | required. This measurement was performed on arbitrary 50 particles, and the number ratio (%) of particles having a minor axis / major axis ratio of 0.8 or less as a single particle was determined.

[Polishing test method]
<Polishing of SiO ₂ film>
A slurry (polishing slurry) containing the silica-based composite fine particle dispersion obtained in each of Examples and 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, the substrate to be polished is set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), and a polishing pad (“IC-1000 / SUBA400 concentric type” manufactured by Nitta Haas) is used. Polishing was performed by supplying a polishing slurry at a rotation speed of 90 rpm at a rate of 50 ml / min for 1 minute.
And the grinding | polishing speed | rate was calculated by calculating | requiring the weight change of the to-be-polished base material before and behind grinding | polishing.
Moreover, 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.).
The polishing scratches were observed by observing the insulating film surface using an optical microscope.

<Aluminum hard disk polishing>
A slurry (polishing slurry) containing the silica-based composite fine particle dispersion obtained in each of Examples and Comparative Examples was prepared. Here, the solid content concentration was 9% by mass and the pH was adjusted to 2.0 by adding nitric acid.
A substrate for aluminum hard disk is set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), and a polishing pad (“Polytex φ12” manufactured by Nitta Haas Co., Ltd.) is used. Polishing is performed by supplying at a rate of 20 ml / min for 5 minutes, and using an ultra-fine defect / visualization macro apparatus (manufactured by VISION PSYTEC, product name: Micro-Max), the entire surface is observed with a Zoom 15, 65.97 cm ² The number of scratches (linear traces) present on the polished substrate surface corresponding to No. 1 was counted and totaled and evaluated according to the following criteria.
Number of linear marks Evaluation Less than 50 “Very few”
50 or more and less than 80
80 or more "Many"
There are at least 80 or more *

<Example 1>
[Preparation of silica fine particle dispersion]
5788.7 g of ultrapure water and 180 g of fumed silica (AEROSIL 50 manufactured by Nippon Aerosil Co., Ltd.) and 41.3 g of 3% ammonia were mixed to obtain 6000 g of Liquid A having a SiO ₂ solid content concentration of 3 mass%. (Hereinafter, in the production process of the silica composite fine particle dispersion, the silica fine particle dispersion is referred to as “liquid A” with respect to the liquid B described later.)
The silica fine particles contained in this liquid A (silica fine particle dispersion) had an average particle diameter (D2) of 46.8 μm (46,800 nm) as measured by LA-950v2 manufactured by Horiba, Ltd. The specific surface area equivalent particle size (DS) was 53 nm. Therefore, D2 / DS was calculated as 883.
Further, for the silica fine particles, Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, NO ₃ , SO ₄ measured by the above measuring method. And the content rate of F was 1 ppm or less. The results are shown in Table 1. (The following examples and comparative examples are also the same)

Next, ion-exchanged water was added to cerium (III) nitrate hexahydrate (manufactured by Kanto Chemical Co., Inc., 4N high-purity reagent) to obtain 2.5 mass% B liquid in terms of CeO ₂ . (Hereinafter, the cerium metal salt dispersion is referred to as “Liquid B”.)

Next, liquid A (6000 g) was heated to 50 ° C. and stirred while liquid B (8453 g, equivalent to 117.4 parts by mass of CeO ₂ with respect to 100 parts by mass of SiO ₂ ). Added over 18 hours. During this time, the liquid temperature was maintained at 50 ° C., and 3% ammonia water was added as necessary to maintain pH 7.85.
And when addition of B liquid was complete | finished, the liquid temperature was raised to 93 degreeC and ageing | curing | ripening was performed for 4 hours. After aging, the product was allowed to cool by allowing it to stand indoors, and after cooling to room temperature, washing was performed while supplying ion-exchanged water with an outer membrane. The precursor particle dispersion obtained after the washing was finished had a solid content concentration of 7% by mass, a pH of 8.7 (at 25 ° C.), and an electric conductivity of 26 μs / cm (at 25 ° C.). .

  Next, 5% by mass acetic acid was added to the obtained precursor particle dispersion to adjust the pH to 6.5, and after drying in a 120 ° C. dryer for 16 hours, using a muffle furnace at 1070 ° C. Firing was performed for 2 hours to obtain a powder (fired body).

After adding 375 g of ion-exchanged water to 125 g of the obtained powder and further adjusting the pH to 10 using a 3% aqueous ammonia solution, φ0.25 mm high-purity silica beads (Daiken Chemical Co., Ltd.), batch type Wet crushing and pulverization were performed using a desktop sand mill, diluted with ion-exchanged water, separated from high-purity silica beads, and 2500 g of a silica-based composite fine particle dispersion having a solid content concentration of 5% by mass was obtained.
Next, the obtained fine particle dispersion is centrifuged for 3 minutes at a relative centrifugal acceleration of 675G in a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number “CR21G”) to remove sediment components, and silica-based composite fine particles are dispersed. A liquid was obtained. The obtained silica-based composite fine particle dispersion had a particle size of 0.130 μm as measured by a laser diffraction scattering method (LA-950, manufactured by HORIBA).

  Table 1 shows the analysis results (content ratios) of various elements or ionic species for the silica-based composite particles contained in the obtained silica-based composite particle dispersion. (The following examples and comparative examples are also the same)

  When the silica-based composite fine particles contained in the obtained silica-based composite fine particle dispersion were measured by an X-ray diffraction method, a Ceriaite diffraction pattern was observed.

Next, a polishing test was performed. Moreover, the minor axis / major axis ratio of the silica-based composite fine particles contained in the polishing slurry was measured. The results are shown in Table 1.
The average particle size of the silica-based composite fine particles was 133 nm as measured using LA-950v2 manufactured by Horiba Ltd.

Further, the silica-based composite fine particles contained in the silica-based composite fine particle dispersion obtained in Example 1 were observed using SEM and TEM. An SEM image and a TEM image (100,000 times) are shown in FIGS.
Moreover, the SEM image (300,000 times) which measured the particle diameter of the child particle is shown in FIG.1 (c).

  Furthermore, the X-ray diffraction pattern of the silica-based composite fine particles contained in the silica-based composite fine particle dispersion obtained in Example 1 is shown in FIG.

In the X-ray diffraction pattern of FIG. 2, it is a fairly sharp Ceriaite crystal, and it appears that ceria crystal particles are strongly sintered with the silica surface from TEM and SEM images.
Further, from FIG. 1, it was observed that a thin silica coating was present on the outermost surface of the silica composite fine particles.

<Example 2>
[Preparation of silica fine particle dispersion]
Ion-exchanged water 3986 g was added to 300 g of fumed silica used in Example 1, φ0.25 mm high-purity silica beads (manufactured by Daiken Chemical Industry Co., Ltd.), Ashizawa Finetech Co., Ltd. bead mill LMZ06, Grinding was performed to obtain 4286 g of a silica fine particle dispersion having a solid content concentration of 7% by mass. The particles contained in this silica fine particle dispersion had an average particle diameter (D2) of 0.12 μm (120 nm) measured by LA-950v2 manufactured by HORIBA, Ltd. 8y76. The specific surface area equivalent particle size (DS) was 45 nm. Therefore, D2 / DS was calculated as 2.7.
2577.7 g of the silica fine particle dispersion obtained above was mixed with 3387.7 g of ultrapure water and 29.7 g of 3% ammonia to obtain 6000 g of A liquid having a SiO ₂ solid content concentration of 3 mass%. Then, a silica-based composite particle dispersion containing silica / ceria composite oxide was prepared under the same conditions as in Example 1. The same operation as in Example 1 was performed, and the same measurement was performed. The results are shown in Table 1. The average particle size of the silica-based composite fine particles obtained in Example 2 was 125 nm.

Example 3 [1] Synthetic silica core (when gel from alkoxide is used as raw material)
[Preparation of silica fine particle dispersion]
Synthetic quartz powder manufactured by Mitsubishi Chemical Co., Ltd. 3986 g of ion-exchanged water is added to 300 g of MKC silica. Grinding was performed to obtain 4286 g of a silica fine particle dispersion having a solid content concentration of 7% by mass. The particles contained in this silica fine particle dispersion had an average particle diameter (D2) of 0.20 μm (200 nm) as measured by LA-950v2 manufactured by Horiba Ltd. The specific surface area equivalent particle size (DS) was 5 nm. Therefore, D2 / DS was calculated to be 40.
2577.7 g of the silica fine particle dispersion obtained above was mixed with 3387.7 g of ultrapure water and 29.7 g of 3% ammonia to obtain 6000 g of A liquid having a SiO ₂ solid content concentration of 3 mass%. Then, a silica-based composite particle dispersion containing silica / ceria composite oxide was prepared under the same conditions as in Example 1. The same operation as in Example 1 was performed, and the same measurement was performed. The results are shown in Table 1. The average particle size of the silica-based composite fine particles obtained in Example 3 was 220 nm.

<Example 4> [2] Hydrogel core [Preparation of silica fine particle dispersion]
A sodium silicate aqueous solution having a SiO ₂ concentration of 24% by weight (SiO ₂ / Na ₂ O molar ratio: 3.1) was diluted with ion-exchanged water, and a sodium silicate aqueous solution having a SiO ₂ concentration of 5% by weight (pH 11.3). 8 kg was prepared.
Sulfuric acid was added to neutralize this sodium silicate aqueous solution so that the pH was 6.5, and the mixture was kept at room temperature for 1 hour to prepare a silica hydride gel. This silica hydrogel was thoroughly washed with an Oliver filter with a 28% aqueous ammonia solution (equivalent to about 120 times the SiO ₂ solid content) to remove salts. The sodium sulfate concentration after washing was less than 0.01% based on the SiO ₂ solid content.
Further, the obtained washed silica hydrogel was diluted with ion-exchanged water to prepare 8 kg of a silica hydrogel dispersion having a SiO ₂ concentration of 5% by weight, and a cation exchange resin (manufactured by Rohm & Haas: Duolite C255LFH) was prepared therein. ) 2460 g was charged. After stirring for 10 minutes, the resin was separated using a stainless wire mesh (mesh size: 325). In a separated state, 200 g of pure water was subsequently poured into the resin as water to be recovered in the same manner. Subsequently, 580 g of an anion exchange resin (manufactured by Rohm & Haas: Duolite UP5000) was added to the silica hydrogel dispersion subjected to the cation exchange treatment and stirred for 10 minutes, and then a stainless wire mesh (mesh size: 325) was used. The resin was separated. In a separated state, 400 g of pure water was subsequently poured into the resin as water to be recovered in the same manner to obtain a silica-based fine particle dispersion.
2577.7 g of the silica fine particle dispersion obtained above was mixed with 3387.7 g of ultrapure water and 29.7 g of 3% ammonia to obtain 6000 g of A liquid having a SiO ₂ solid content concentration of 3 mass%. Then, a silica-based composite particle dispersion containing silica / ceria composite oxide was prepared under the same conditions as in Example 1. The same operation as in Example 1 was performed, and the same measurement was performed. The results are shown in Table 1. The average particle size of the silica-based composite fine particles obtained in Example 4 was 220 nm.

<Comparative Example 1>
A polishing test was conducted on the same base particles as used in Example 1 (that is, base particles having an average particle diameter of 46.8 μm of fumed silica were treated as silica-based composite fine particles). The results are shown in Table 1.

<Comparative example 2>
A polishing test was performed on the base particles obtained in Example 2 (that is, base particles having an average particle size of 0.12 μm obtained by wet-pulverizing fumed silica were treated as silica-based composite fine particles).
The results are shown in Table 1.

<Comparative Example 3>
"Silica fine particle dispersion (average particle diameter 60nm of the silica fine particles)" were mixed and prepared ethanol 12,090g and ethyl orthosilicate 6,363.9g of was a mixture a _1.
Next, 6,120 g of ultrapure water and 444.9 g of 29% ammonia water were mixed to obtain a mixed solution b ₁ .
Next, 192.9 g of ultrapure water and 444.9 g of ethanol were mixed and used as bedding water.
Then, the stirring water was adjusted to 75 ° C. while stirring, and the mixed solution a ₁ and the mixed solution b ₁ were simultaneously added so that the addition was completed in 10 hours each. When the addition is completed, the liquid temperature is kept at 75 ° C. for 3 hours and ripened, then the solid content concentration is adjusted, and the SiO ₂ solid content concentration is 19% by mass. 9,646.3 g of a silica fine particle dispersion having an average particle diameter of 60 nm of silica fine particles measured by III was obtained.

"Silica fine particle dispersion (average particle size 108nm of the silica fine particles)" was mixed with prepared methanol 2,733.3g and ethyl orthosilicate 1,822.2g of was a mixture a _2.
Next, 1,860.7 g of ultrapure water and 40.6 g of 29% ammonia water were mixed to obtain a mixed solution b ₂ .
Next, 592.1 g of ultrapure water and 1,208.9 g of methanol were mixed and used as a covering water, and 922.1 g of a silica fine particle dispersion having an average particle diameter of 60 nm obtained in the previous step was added.
Then, the stirring water containing the silica fine particle dispersion is adjusted to 65 ° C. while stirring, and the mixed solution a ₂ and the mixed solution b ₂ are added simultaneously so that the addition is completed in 18 hours each. It was. After the addition is completed, the liquid temperature is kept at 65 ° C. for 3 hours and ripened, 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 Got.
The particles contained in this high-purity silica fine particle dispersion had an average particle diameter of 108 nm as measured by PAR-III manufactured by Otsuka Electronics Co., Ltd.
Further, the content of alkali metals, alkaline earth metals, and the like by ICP measurement was 1 ppm or less. Table 1 shows the analysis results of various elements or ionic species contained in the mother particles.

Next, 114 g of cation exchange SK-1BH (manufactured by Mitsubishi Chemical Corporation) was gradually added to 1,053 g of this high-purity silica fine particle dispersion, followed by stirring for 30 minutes to separate the resin. The pH at this time was 5.1.
Ultrapure water was added to the resulting silica fine particle dispersion to obtain 6,000 g of Liquid A having a SiO ₂ solid content concentration of 3% by mass.

  Then, a silica-based composite particle dispersion containing silica / ceria composite oxide was prepared under the same conditions as in Example 1. The same operation as in Example 1 was performed, and the same measurement was performed. The results are shown in Table 1.

In addition, in the silica type composite fine particle which the silica type composite fine particle dispersion liquid of Example 1 contained, the drop-off | omission of the child particle (ceria crystal particle) by crushing and grinding | pulverization was confirmed slightly.
Further, in the silica-based composite fine particles of Example 1, the mass ratio of silica to ceria (ceria crystal particles) was in the range of 100: 11 to 316.

  Since the composite fine particle of the present invention does not contain impurities, it can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate or a wiring substrate.

Claims (4)

The manufacturing method of the silica type composite fine particle dispersion characterized by including the following process 1-process 3.
Step 1: Non-spherical silica fine particles having a ratio [(D2) / (DS)] of the secondary particle size (D2) to specific surface area converted particle size (DS) of greater than 1.0 are dispersed in a solvent. While stirring the silica fine particle dispersion and maintaining the temperature at 5 to 98 ° C. and the pH in the range 7.0 to 9.0, the metal salt of cerium was added continuously or intermittently to the precursor particles. The process of obtaining the precursor particle dispersion liquid containing.
Step 2: The precursor particle dispersion is dried and fired at 400 to 1,200 ° C., and the fired body obtained is subjected to the following treatment (i) or (ii) to obtain a fired body crushed dispersion liquid. Obtaining.
(I) Crushing and pulverizing by a dry method, and adding a solvent to carry out a solvent dispersion treatment.
(Ii) A solvent is added, and the mixture is crushed and pulverized by a wet process.
Step 3: A step of obtaining a silica-based composite fine particle dispersion by subjecting the calcined dispersion to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more and subsequently removing a sediment component. The method for producing a silica-based composite fine particle dispersion according to claim 1, wherein the content of impurities contained in the silica fine particles is as shown in the following (a) and (b).
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr are each 100 ppm or less.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are each 10 ppm or less.   A portion of the surface of the non-spherical silica fine particles having a ratio [(D2) / (DS)] of the secondary particle size (D2) to the specific surface area converted particle size (DS) of greater than 1.0 is coated with silica. Silica fine particle dispersion coated with crystalline ceria.   A polishing slurry comprising the silica fine particle dispersion according to claim 3.