WO2010104085A1

WO2010104085A1 - Semiconductor polishing agent, method for producing the same, and polishing method

Info

Publication number: WO2010104085A1
Application number: PCT/JP2010/053919
Authority: WO
Inventors: 勝鈴木; 伯人中沢; 聡竹宮; 喜則金; 浩一岡田
Original assignee: 旭硝子株式会社
Priority date: 2009-03-13
Filing date: 2010-03-09
Publication date: 2010-09-16
Also published as: TW201037066A; JP2012109287A

Abstract

Provided is a semiconductor polishing agent that simultaneously has dispersion stability, excellent polishing properties, and excellent polishing planarization properties. The semiconductor polishing agent contains cerium oxide abrasive grains, water, and a polysaccharide, and further contains one or more selected from the group consisting of water-soluble organic polymers and anionic surfactants.

Description

Abrasive for semiconductor, manufacturing method thereof and polishing method

The present invention relates to a semiconductor polishing agent and a polishing method for chemical mechanical polishing in a semiconductor device manufacturing process, and more particularly to a semiconductor polishing agent containing cerium oxide suitable for shallow trench isolation and planarization of an interlayer insulating film, The present invention relates to a manufacturing method and a polishing method.

In recent years, development of microfabrication technology for increasing the density of elements has been promoted due to the demand for higher integration and higher functionality of semiconductor devices. In particular, the importance of a planarization technique by a chemical mechanical polishing method (hereinafter referred to as CMP) is increasing. For example, as semiconductor devices are miniaturized and wiring layers are increased, surface irregularities (steps) on each layer in the manufacturing process tend to increase. In order to prevent the problem that this step exceeds the depth of focus of photolithography and sufficient resolution cannot be obtained, a technique for flattening an interlayer insulating film and embedded wiring in the multilayer wiring forming process is important.

In addition, in a conventional semiconductor device, a selective thermal oxidation method of a silicon substrate called a LOCOS (Local Oxidation of Silicon) method has been used in order to electrically isolate elements such as transistors, but it is formed by thermal oxidation. There is a problem that the separation region to be generated generates unevenness on the surface due to volume expansion. Further, there is a problem that oxidation proceeds in the lateral direction and bites into the element region, which is an obstacle to miniaturization. Therefore, in recent years, a shallow trench isolation (hereinafter referred to as STI) has been introduced. In this method, a trench groove is provided in a silicon substrate in order to electrically insulate an element region, and an insulating film such as a silicon oxide film is embedded in the trench groove.

The STI process will be described with reference to FIG. In FIG. 1A, an element region is masked with a silicon nitride film 3 or the like, a trench groove 10 is formed in the silicon substrate 1, and then an insulating film such as a silicon oxide film 2 is deposited so as to fill the trench groove 10. State. In this state, by CMP, the excess silicon oxide film 2 on the silicon nitride film 3 that is the convex portion is polished and removed, and the insulating film in the trench groove 10 that is the concave portion is left, so that the insulating film is embedded in the trench. An element isolation structure is obtained. At the time of CMP, a silicon nitride film polishing rate and a silicon nitride film polishing rate are made to have a selection ratio, and the silicon nitridation is completed when the silicon nitride film 3 is exposed as shown in FIG. It is common to use the membrane 3 as a stopper. Giving this polishing rate a selective ratio is a great effect for CMP abrasives, which is an effect that cannot be realized with ordinary abrasives.

Here, if the polishing is excessive, the silicon oxide film embedded in the trench groove portion 10 is polished and recessed as shown in FIG. 1C, and structural defects such as the recess 20 called dishing occur. In some cases, flattening may be insufficient, or electrical performance may deteriorate. The degree of dishing depends on the width of the trench groove, and the dishing tends to increase particularly in a wide trench groove.

Conventionally, silica abrasive grains are generally used as polishing abrasive grains used in CMP. However, since the selection ratio between the polishing speed of the silicon oxide film and the polishing speed of the silicon nitride film is small, polishing for these is performed in the STI process. A cerium oxide abrasive having excellent selectivity has been used.

In Patent Document 1, a convex portion is preferentially polished and flattened with respect to a concave portion by an abrasive containing a cerium oxide abrasive and an organic compound containing a hydrophilic group composed of a carboxyl group or a salt of a carboxyl group as an additive. Technology is disclosed. The additive referred to here improves the trench groove width dependency of dishing, and the above-mentioned additive concentration needs to be high in order to reduce dishing even in a wide trench groove. However, when the additive concentration is increased, the aggregation of the cerium oxide abrasive grains is promoted, so that the abrasive grains are precipitated and the dispersion stability of the abrasive is lowered. In addition, when agglomeration of abrasive grains occurs, there is a problem that scratches increase and the device becomes defective.

For example, Japanese Patent No. 3278532 discloses an example of a polishing liquid containing pure water containing 1% cerium oxide as polishing grains as abrasive grains and 6.0% ammonium polycarboxylate as an additive. ing. However, since the additive is in a high concentration, the agglomeration of the abrasive grains is remarkable, and when the polishing liquid is allowed to stand, the cerium oxide abrasive grains completely settle within a few minutes. In the CMP polishing process, since there is a waiting time during which polishing is not performed, the settling of abrasive grains may occur in portions where the abrasive is not constantly stirred or flowed, which may cause blockage of piping parts.

In order to prevent this, there is a method of adding additives to the abrasive in the piping immediately before or on the polishing pad, but the mixing tends to be insufficient or the concentration tends to be non-uniform, resulting in unstable polishing characteristics. Prone. In addition, since the abrasive grains easily aggregate and adhere on the pad, there is also a problem that scratches increase.

Moreover, although cerium oxide abrasive grains have better polishing characteristics than conventional silica abrasive grains, they tend to settle due to their large specific gravity. Furthermore, when an additive is excessively added for improving the polishing characteristics, there is a problem that aggregation is promoted and aggregation and sedimentation are remarkable.

Patent Document 2 discloses an abrasive containing cerium oxide particles, water, and an anionic surfactant as an abrasive applicable to shallow trench separation, and the pH and viscosity (mPa · s) thereof are set to pH. Is represented by (x, y) coordinates where x is the viscosity and y is the viscosity, point A (5.5, 0.9), point B (5.5, 3.0), point C (10.0, 3) 0.0) and D points (9.0, 0.9) are disclosed as preferred in the range of the region surrounded by the four points. In order to achieve global planarization, it is necessary to adjust the addition amount and pH of the surfactant so that the polishing rate of the pattern recesses is sufficiently smaller than the polishing rate of the projections. In addition, it is described that the viscosity of the abrasive is preferably 1.0 to 2.5 mPa · s.

In addition, since the viscosity increases with the addition amount of the surfactant, in order to realize a planarization characteristic with less pattern dependency by setting the viscosity within the range of 1.0 to 1.4 mPa · s, the surfactant is used. The pH of the abrasive after addition is preferably 5.5 to 9, and it is described that the selective ratio between the polishing rate of the silicon oxide film and the polishing rate of the silicon nitride film can be increased in this pH range. Moreover, it is illustrated that a trace amount of dispersant is added to the abrasive grains in advance.

However, when an abrasive is prepared based on the examples of this publication, the average particle size is 2 to 3 of the average particle size of the abrasive dispersion by adding a surfactant to the liquid in which the abrasive is dispersed. Aggregate twice. Therefore, the dispersibility of the abrasive grains in the abrasive was poor, the abrasive grains settled within a few minutes, it was difficult to use, and the polishing rate was insufficient. In addition, when the surfactant concentration is high, the dishing variation is small and the flattening characteristics are excellent. It was not good.

Furthermore, as the surfactant concentration increases, the number of scratches increases rapidly. This is presumably because when the concentration of the surfactant is high, aggregation and sedimentation of the cerium oxide abrasive grains are promoted and accumulated on the polishing pad. That is, it is considered that if there are even a few coarse particles that cause scratches in the polishing abrasive grains, the abrasive grains aggregate on the polishing pad and accumulate, thereby causing an increase in scratches. Moreover, it is considered that the abrasive grains aggregates that have become enormous due to the aggregation itself may cause scratches.

Thus, in the prior art, an abrasive having both the dispersion stability of the abrasive and excellent scratch characteristics and excellent planarization characteristics of an abrasive has not been obtained, and a semiconductor device having sufficient characteristics has not been obtained. It was difficult to get.
Further, pullulan is known as an additive for abrasives (see, for example, Patent Document 3). However, Patent Document 3 is an abrasive for the barrier layer and not for silicon oxide as in the present application. Different objects to be polished should have different problems and effects to be solved.

Japanese Patent No. 3278532 (US Pat. No. 6,224,464) JP 2000-160137 A Japanese Patent Laying-Open No. 2005-294798 (US Patent Publication No. 2007/0004210)

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a semiconductor polishing agent having simultaneously dispersion stability, excellent polishing characteristics, and excellent polishing flattening characteristics.

That is, the present invention has the following features. That is, it is a semiconductor polishing slurry that contains cerium oxide abrasive grains, water, and polysaccharides, and further includes at least one selected from the group consisting of a water-soluble organic polymer and an anionic surfactant.

The abrasive of the present invention can realize excellent polishing characteristics and excellent polishing flattening characteristics by using a specific additive.

FIG. 3 is a schematic cross-sectional view when a semiconductor device substrate is polished with a semiconductor abrasive in an STI process. The figure which shows an example of the grinding | polishing apparatus applicable to the grinding | polishing method of this invention.

Hereinafter, the present invention will be described in detail.

In the present invention, cerium oxide is used as the abrasive grains. However, in polishing glass-based materials such as silicon oxide films, the cerium oxide abrasive grains exhibit a specifically high polishing rate. This is because when cerium oxide and silicon oxide in the material to be polished come into contact with each other, a chemical bond is generated between the two and a polishing force more than a mere mechanical action is generated. Therefore, in polishing using cerium oxide, it is important to control the contact between the abrasive grains and the object to be polished, and problems that did not occur with silicon oxide may occur.

In the STI process and the interlayer insulating film CMP process, it is required to efficiently planarize an object to be polished such as a silicon oxide film having an uneven surface. That is, it is desirable to selectively polish the convex portion. In order to achieve this, it is important to include an additive in the polishing agent that adsorbs to the surface of the cerium oxide abrasive grains to prevent direct contact with a polishing target such as a silicon oxide film and suppress polishing. is there. By adding such an additive, when a high pressure is applied, the additive adsorbed on the surface of the cerium oxide abrasive grains is peeled off, and contact with the object to be polished occurs, whereby polishing proceeds.

In a general polishing method in which a polishing object is pressed against a polishing pad or the like and moved in a relative manner, the pressure applied to the surface of the polishing object varies locally depending on the surface shape. Because the pressure applied to the convex portion is higher than that of the concave portion, the additive adsorbed on the surface of the cerium oxide abrasive grains easily peels off at the convex portion, and contact with the object to be polished occurs, making it easy to proceed with polishing. It becomes possible to selectively polish the recess.

The cerium oxide abrasive grains are not particularly limited, but for example, cerium oxide abrasive grains disclosed in JP-A-11-12561 or JP-A-2001-35818 can be preferably used. That is, a cerium oxide powder obtained by adding an alkali to a cerium (IV) ammonium nitrate aqueous solution to prepare a cerium hydroxide gel, filtering, washing and baking can be preferably used. Further, cerium oxide abrasive grains obtained by pulverizing and firing high-purity cerium carbonate, and further pulverizing and classifying the cerium carbonate can be preferably used.

The average particle diameter of the cerium oxide abrasive is preferably 0.05 to 0.5 μm, more preferably 0.05 to 0.3 μm, and even more preferably 0.05 to 0.2 μm. If the average particle size is too large, there is a possibility that polishing scratches such as scratches are likely to occur on the surface of the semiconductor substrate. On the other hand, if the average particle size is too small, the polishing rate may be lowered. Moreover, since the ratio of the surface area per unit volume is large, it is easily influenced by the surface state, and the abrasive may be easily aggregated depending on conditions such as pH and additive concentration.

For the measurement of the average particle size, a particle size distribution analyzer such as a laser diffraction / scattering type, a dynamic light scattering type, or a photon correlation type can be used. When the particle size is large and easily settles, a laser diffraction / scattering particle size distribution meter is preferable, and the above range is a preferable range when measured using a laser diffraction / scattering particle size distribution meter. .

The cerium oxide abrasive is preferably contained in the range of 0.1 to 5.0% by mass, particularly 0.15 to 0.35% by mass with respect to the total mass of the abrasive. If it is less than 0.1% by mass, a sufficient polishing rate may not be obtained. If it exceeds 5.0% by mass, the viscosity of the abrasive becomes high and handling becomes difficult in many cases.

In the abrasive | polishing agent in this invention, 1 or more types chosen from the group which consists of a water-soluble organic polymer and an anionic surfactant are contained.
As the water-soluble organic polymer, those having a carboxylic acid group or a carboxylic acid group are preferable. Specifically, a homopolymer of a monomer having a carboxylic acid group such as acrylic acid, methacrylic acid or maleic acid, or the polymer. Homopolymers in which the carboxylic acid group moiety is a salt such as an ammonium salt. A copolymer of a monomer having a carboxylic acid group and a monomer having a carboxylic acid group, or a monomer having a carboxylic acid group and a derivative such as an alkyl ester of carboxylic acid is also preferred. Furthermore, water-soluble organic polymers such as polyvinyl alcohol, and anionic surfactants such as ammonium oleate, ammonium lauryl sulfate, and triethanolamine lauryl sulfate can be preferably used.

As the water-soluble organic polymer and the anionic surfactant, a polymer having a carboxylic acid group or a salt thereof is particularly preferable. Specific examples include polyacrylic acid or a polymer in which at least a part of the carboxylic acid group of polyacrylic acid is substituted with an ammonium carboxylate base (hereinafter, referred to as ammonium polyacrylate). When the abrasive of the present invention contains an inorganic acid or an inorganic acid salt, which will be described later, ammonium polyacrylate is particularly preferable in order to adjust the pH to the range of the abrasive of the present invention. Here, when a water-soluble organic polymer such as ammonium polyacrylate is used as an additive, the molecular weight is preferably 1000 to 50000, particularly 2000 to 30000. However, the water-soluble organic polymer and the anionic surfactant are not necessarily contained.

The total content of the water-soluble organic polymer and the anionic surfactant is 0.001 to 0.5% by mass, particularly 0.001 to 0.2% by mass, for the purpose of maintaining dispersion stability. Is preferably 0.005 to 0.1% by mass.

On the other hand, in-plane uniformity of the polishing rate in a silicon wafer that is an object to be polished is important. STI CMP will be described as an example. In STI CMP, polishing is usually performed until the silicon oxide film on the silicon nitride film is completely removed at all points in the wafer surface. At this time, if the in-plane uniformity is poor, the silicon nitride film is exposed first in the portion where the polishing rate is high, while the silicon nitride film is not exposed yet in the portion where the polishing rate is low. If polishing is continued until the silicon nitride film is exposed at a portion where the polishing rate is low, polishing of the oxide film at the trench portion proceeds at a portion where the polishing rate is high, resulting in a problem that the amount of dents increases.
This increase in the amount of dents causes variations in the thickness of the trench oxide film having an element isolation function, causing a device defect, and as a result, the yield may be reduced.

The abrasive in the present invention contains a polysaccharide. Polysaccharide means a substance in which a number of monosaccharide molecules are polymerized by glycosidic bonds, specifically amylose, amylopectin, glycogen, hydroxyethylcellulose, hydroxypropylcellulose, mannan, hyaluronic acid, chondroitin, pullulan, chitin, agarose, Carrageenan, pectin, pevaline, xyloglucan, dextrin and the like. The polysaccharide is preferably hydroxyethyl cellulose, hydroxypropyl cellulose, hyaluronic acid, chondroitin or pullulan, particularly preferably pullulan. Pullulan is a polysaccharide in which maltotriose, in which three molecules of glucose are α-1,4 bonded, is further α-1,6 bonded.
Pullulan, which is such a polysaccharide, is preferable because it improves the in-plane uniformity of the polishing rate. When pullulan is added, the in-plane uniformity of the polishing rate is improved. The reason is not clear, but due to the interaction between the hydroxyl group of the abrasive grain surface, the hydroxyl group of pullulan, the hydroxyl group of the silicon oxide film as the object to be polished, and the terminal group of the polishing pad, the abrasive grains, silicon oxide film, polishing pad It is conceivable that the in-plane uniformity is improved by improving the affinity and improving the lubricity during polishing.
Pullulan is highly effective when the weight average molecular weight is in the range of 10,000 to 1,000,000. The presence of hydroxyl groups is considered to be an important factor. If the weight average molecular weight is less than 10,000, the effect of improving the polishing rate is small, and even if the weight average molecular weight exceeds 1,000,000, a significant increase in effect cannot be expected. In particular, a range of 50,000 to 300,000, particularly 50,000 to 200,000, and more preferably 100,000 to 200,000 is preferable. The weight average molecular weight can be measured by gel permeation chromatography (GPC). Moreover, the polysaccharide may contain not only 1 type but multiple types.

The concentration of pullulan in the abrasive is 0.005 to 20% by mass, particularly 0.005 to 5% by mass, more preferably 0.005 to 1% by mass, 0.005 from the viewpoint of obtaining a sufficient effect of promoting polishing. To 5% by mass and 0.005 to 0.2% by mass. The concentration of pullulan in the abrasive is preferably set within the above range in consideration of the polishing rate, the uniformity of the abrasive slurry, and the like.

When ammonium polyacrylate is used as the water-soluble organic polymer and the anionic surfactant, the proportion of pullulan and ammonium polyacrylate is from 1: 0.0005 to 1: 100, especially 1: It is preferably 0.001 to 1:40. In-plane uniformity can be further improved by coexisting pullulan and ammonium polyacrylate.

As another additive in the abrasive, ammonium nitrate may be included. It is estimated that the inclusion of ammonium nitrate has an effect of increasing the polishing rate. The concentration of ammonium nitrate in the abrasive is 0.01 to 0.5% by mass, particularly 0.01 to 0.2% by mass from the viewpoint of obtaining a sufficient effect of promoting polishing. When the pullulan further contains ammonium nitrate, it is preferable that the concentration of the pullulan in the abrasive is appropriately set in consideration of the polishing rate, the uniformity of the abrasive slurry, and the like. The ratio of pullulan to ammonium nitrate is preferably in the range of 1: 0.0005 to 1: 100, particularly 1: 0.02 to 1:40, by mass. By allowing the pullulan and ammonium nitrate to coexist in the above range, the polishing rate can be improved while maintaining good in-plane uniformity.

Further, as another additive in the abrasive, an antibacterial agent and a bactericidal agent may be included for the purpose of suppressing generation and increase of microorganisms and fungi.

The pH of the present polishing agent is preferably 4 to 10, particularly 5 to 9, for obtaining a sufficient polishing rate and maintaining dispersion stability.

The abrasive of the present invention may contain an inorganic acid or an inorganic acid salt. Examples of the inorganic acid or inorganic acid salt include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, boric acid, carbonic acid, and ammonium salts or potassium salts thereof. The pH of the abrasive can be adjusted with an inorganic acid or an inorganic acid salt.

In order to adjust the abrasive to a predetermined pH, a basic compound may be added to the abrasive separately from the acid. As the basic compound, ammonia, potassium hydroxide, or quaternary ammonium hydroxide such as tetramethylammonium hydroxide or tetraethylammonium hydroxide (hereinafter referred to as TEAH) can be used. Ammonia is preferred when it is desirable not to include an alkali metal.

In consideration of the isoelectric point and gelation region of the cerium oxide abrasive grains, it is preferable to adjust to the optimum pH value of the present abrasive within the above-mentioned range. For this purpose, a pH buffer may be used. As the pH buffering agent, any substance having general pH buffering ability can be used, but it is selected from succinic acid, citric acid, oxalic acid, phthalic acid, tartaric acid and adipic acid which are polyvalent carboxylic acids. One or more are preferred.
Moreover, glycylglycine and alkali carbonate can also be used. The concentration of the pH buffer in the abrasive is preferably 0.01 to 10% by mass with respect to the total mass of the abrasive. Ammonium nitrate not only functions as a pH adjuster, but may contribute to an increase in the polishing rate depending on the concentration of other additives.

This abrasive preferably uses water as a solvent in order to exhibit the effect as an abrasive. The water content is preferably 50 to 99.9% by mass, particularly 80 to 99.9% by mass, and more preferably 90 to 99% by mass. The water used in the abrasive of the present invention is not particularly limited, but pure water, ultrapure water, ion-exchanged water, etc. can be used because of its influence on other components, additives, impurities, pH, etc. It can be preferably used.

In addition, it is preferable that the abrasive | polishing agent for semiconductors does not contain metal impurities, such as an alkali metal, alkaline-earth metal, and a heavy metal. The content concentration of metal impurities is preferably less than 100 ppm by mass. More preferably, it is less than 10 ppm by mass, more preferably less than 1 ppm by mass.

In view of the long-term storage stability of the abrasive and the stability of various polishing properties, the method for producing an abrasive of the present invention includes a liquid A containing cerium oxide abrasive grains and water, and a liquid B containing an additive and water. Is used, and a liquid A and a liquid B are mixed before polishing to obtain a semiconductor abrasive. As a mixing method of the A liquid and the B liquid, there is a method of mixing in the pipe immediately before or on the polishing pad or on the polishing pad, but the semiconductor abrasive of the present invention hardly agglomerates after mixing and is practically sufficient. Since it is stable for a long period of time, it may be mixed in advance. That is, it is possible to use a commonly used semiconductor abrasive supply device in which the liquid A and the liquid B are put in a semiconductor abrasive storage tank and agitated and mixed with a propeller agitator or the like, or the abrasive is constantly flowed through a circulation line.

In the present invention, in order to sufficiently mix the cerium oxide abrasive grains and the additive and stabilize the adsorption state of the additive on the abrasive grain surface, the liquid A containing cerium oxide abrasive grains and water, the additive, It is preferable to use the polishing liquid after previously mixing and stirring the B liquid containing water. The polishing liquid can be used immediately after mixing the A liquid and the B liquid, but is preferably used after mixing for several minutes or more. In particular, it is preferable to use the abrasive after 15 minutes or more have elapsed after mixing. CMP polishing can be stably performed by supplying a mixed semiconductor polishing agent to a polishing apparatus via a pump. A circulation line may be provided in the supply line to make the semiconductor abrasive uniform.

In the preparation of the liquid A, a method in which cerium oxide abrasive grains are dispersed in pure water or deionized water is preferable. At the time of dispersion, an ultrasonic disperser that disperses the agglomerates using ultrasonic energy and disperses the abrasive grains in water. , Homogenizers, homogenizers (product name, manufactured by Sugino Machine Co., Ltd.), nanomizers (product name, manufactured by Yoshida Machine Industry Co., Ltd.) Etc. are preferably used. Moreover, it is preferable to add a dispersing agent simultaneously in that case. Here, the dispersant is added in order to stably disperse the abrasive grains in a dispersion medium such as pure water. As the dispersant, the same additives as those described above can be used. That is, the additive in the present invention can be added not only to the B liquid but also to the A liquid as having a function of a dispersant.

For example, when a water-soluble organic polymer such as ammonium polyacrylate is added as a dispersant, the concentration is 0.1 to 1.0% by mass with respect to the mass of the cerium oxide abrasive, A range of 0.3 to 0.7% is preferable. If the concentration of the dispersant is lower than this concentration range, the dispersibility of the abrasive grains tends to be insufficient, and if the concentration of the dispersant is higher than this range, the aggregation of the abrasive particles tends to progress gradually.

In the preparation of solution B, a method of dissolving additives such as the above-mentioned polysaccharides, water-soluble organic polymers and anionic surfactants in pure water or deionized water can be exemplified. Further, by adding an inorganic acid or an inorganic acid salt to the B liquid and adjusting the pH in advance, the pH of the semiconductor abrasive prepared by mixing the A liquid and the B liquid can be set to a predetermined value. . In addition, as a method for adjusting the pH of the semiconductor abrasive after mixing to a predetermined value, a method of controlling the pH of the additive can also be employed. For example, when a copolymer composed of a carboxylic acid and a carboxylic acid salt is used as an additive, a method of adjusting the pH by controlling the polymerization ratio of the carboxylic acid and the carboxylic acid salt can also be employed.

The concentration of the A solution and the B solution can be set to a predetermined concentration by setting the concentration of the A solution and the B solution at a mass ratio of 1: 1, for example, twice the concentration at the time of polishing. For the convenience of storage and transportation, for example, the concentration of liquid A and liquid B is about 10 times the concentration of abrasive grains, additives, etc. when used for polishing, and diluted to twice the concentration when used. Further, the liquid A and the liquid B may be mixed at a mass ratio of 1: 1 so that a predetermined concentration is obtained. In addition, it is possible to achieve a predetermined concentration by mixing 10 times concentration of liquid A, liquid B and deionized water so that the mass ratio is 1: 1: 8. It is not limited to these.

As a semiconductor substrate to be polished with the semiconductor abrasive of the present invention, the above-described STI substrate for shallow trench isolation can be cited as a preferred example. As described above, the semiconductor polishing slurry of the present invention has high polishing rate selectivity with respect to the silicon oxide film and the silicon nitride film, and can polish the silicon oxide film at a high polishing rate with little dishing. Therefore, the abrasive of the present invention is effective when polishing a semiconductor substrate in which the silicon oxide film 2 and the silicon nitride film 3 are formed on the silicon substrate 1. Furthermore, as an application, the abrasive of the present invention is also effective for polishing for planarizing an interlayer insulating film between multilayer wirings.

Examples of the silicon oxide film 2 include a so-called PE-TEOS film formed by plasma CVD using tetraethoxysilane as a raw material. In addition, a so-called HDP film formed by a high-density plasma CVD method is also exemplified. An example of the silicon nitride film 3 is a film formed by low pressure CVD or plasma CVD using silane or dichlorosilane and ammonia as raw materials. In place of the silicon oxide film, a SiOF film, a BPSG (boro-phospho-silicate glass) film, a PSG (phospho-silicate glass) film, or the like can also be used. In addition, a SiON film, a SiCN film, or the like can be used instead of the silicon nitride film.

As a method for polishing a semiconductor substrate using the semiconductor polishing slurry of the present invention, a silicon oxide film and a polishing pad formed on the surface to be polished of the semiconductor substrate, for example, the surface of the semiconductor substrate, while supplying the semiconductor polishing slurry. A polishing method is preferably performed by bringing them into contact with each other and moving them relative to each other. A general polishing apparatus can be used as the polishing apparatus. For example, FIG. 2 is a diagram showing an example of a polishing apparatus applicable to the polishing method of the present invention. While supplying the semiconductor polishing agent 36 from the polishing agent supply pipe 35, the semiconductor substrate 31 is held on the polishing head 32, brought into contact with the polishing pad 34 attached to the surface of the polishing surface plate 33, and the polishing head 32 and the polishing constant are fixed. Although it is a system which rotates the board 33 and carries out relative movement, it is not limited to this.

Here, the polishing head 34 may not only rotate but also move linearly. The polishing surface plate 33 and the polishing pad 34 may be as large as or smaller than the semiconductor substrate 31. In that case, it is preferable that the entire polishing surface of the semiconductor substrate can be polished by relatively moving the polishing head 32 and the polishing surface plate 33. Further, the polishing surface plate 33 and the polishing pad 34 may not be a rotary type, and may be a belt type that moves in one direction, for example.

The polishing conditions are not particularly limited, but the polishing rate can be improved by changing the pressure applied to the polishing pad 34 by applying a load to the polishing head 34. The polishing pressure at this time is preferably about 0.5 to 50 kPa, and about 3 to 40 kPa is particularly preferable from the viewpoint of polishing rate uniformity within the semiconductor substrate, flatness, and prevention of polishing defects such as scratches. The rotation speed of the polishing platen and polishing head is preferably about 50 to 500 rpm, but is not limited thereto.

As the polishing pad, a general nonwoven fabric, foamed polyurethane, porous resin, non-porous resin or the like can be used. In addition, grooves such as lattices, concentric circles, and spirals may be formed on the surface of the polishing pad in order to promote the supply of the semiconductor polishing agent or to collect a certain amount of the semiconductor polishing agent. Good.

Examples of the present invention will be described below. Examples 1 to 9 and 17 to 21 are examples, and examples 10 to 16 are comparative examples. In the examples, “%” means mass% unless otherwise specified. The characteristic value was evaluated by the following method.
(PH)
The pH was measured with Yokogawa Electric Corporation pH81-11.

(Polishing characteristics)
Polishing was performed with the following equipment and conditions.
Polishing machine: fully automatic CMP apparatus Mirra (manufactured by Applied Materials).
Abrasive supply rate: 200 ml / min.
Polishing pad: 2-layer pad IC-1400, K-groove. (Rohm & Haas)
Polishing pad conditioning: MEC100-PH3.5L. (Mitsubishi Materials Corporation)
Polishing pressure: 14 kPa
Number of rotations of polishing platen: 77 rpm
Rotation speed of polishing head: 73rpm

(Polished object)
A silicon wafer substrate in which a silicon oxide film (film thickness: 1000 nm) is formed on the surface of an 8-inch silicon wafer substrate by a plasma CVD method (PE-TEOS) using ethyl orthosilicate (TEOS) as a raw material.

(Measurement of polishing rate)
For the measurement of the polishing rate, a film thickness meter UV-1280SE manufactured by KLA-Tencor was used. The polishing rate was calculated by taking the difference between the film thickness before polishing and the film thickness after polishing for 1 minute. The average value of polishing rate and in-plane uniformity were used as evaluation indexes by the following methods.
Polishing rate (Å / min): Average polishing rate of 49 points in the wafer surface In-plane uniformity (%): Standard deviation / average value × 100
[Example 1]
Mixing cerium oxide abrasive grains and 100 mass% cerium oxide abrasive grains with 0.7 mass% ammonium polyacrylate as a water-soluble organic polymer with stirring in deionized water, ultrasonic dispersion, filter Rings were applied to prepare an abrasive mixture having an abrasive concentration of 10% by mass and a water-soluble organic polymer concentration of 0.07% by mass. Next, this was diluted 20 times with deionized water to prepare an abrasive mixture A having an abrasive concentration of 0.5 mass% and a water-soluble organic polymer concentration of 0.0035 mass%. Its pH was 8.1. Next, in deionized water, ammonium polyacrylate is dissolved as a water-soluble organic polymer so as to have a concentration of 0.1% by mass. Further, ammonium nitrate is 0.1% by mass, and polysaccharide is 0.02% by mass. It added so that additive liquid B1 was produced. By mixing the abrasive mixture liquid A and the additive liquid B1 with stirring, the abrasive concentration is 0.25% by mass, the ammonium polyacrylate (molecular weight 5000) concentration is 0.05% by mass, and the ammonium nitrate concentration is 0.05 mass. %, And a pullulan concentration of 0.01% by mass was prepared for a semiconductor abrasive. Its pH was 7.73. The abrasive concentration means the concentration of cerium oxide abrasive particles, and the dispersant concentration means the concentration of ammonium polyacrylate added to the abrasive mixture A.

The polishing characteristics of the obtained semiconductor abrasive were evaluated by the polishing rate and in-plane uniformity by the method as described above. The composition of the abrasive for semiconductors is shown in Table 1, and the evaluation results are shown in Table 2.

[Example 2]
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water to a concentration of 0.1% by mass, and ammonium nitrate is further added to 0.2% by mass and pullulan is added to 0.02% by mass. Was made. By mixing the abrasive mixture A and the additive liquid B2 while stirring, the abrasive concentration is 0.25% by mass, the ammonium polyacrylate concentration is 0.05% by mass, the ammonium nitrate concentration is 0.1% by mass, and the pullulan concentration. A 0.01% by mass semiconductor abrasive was prepared. Its pH was 7.54.
The obtained semiconductor abrasive was evaluated in the same manner as in Example 1. The composition of the abrasive for semiconductors is shown in Table 1, and the evaluation results are shown in Table 2.

[Example 3]
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water to a concentration of 0.1% by mass, and ammonium nitrate is further added to 0.4% by mass and pullulan is added to 0.02% by mass. Was made. By mixing the abrasive liquid mixture A and the additive liquid B3 while stirring, the abrasive grain concentration is 0.25% by mass, the ammonium polyacrylate concentration is 0.05% by mass, the ammonium nitrate concentration is 0.2% by mass, and the pullulan concentration. A 0.01% by mass semiconductor abrasive was prepared. Its pH was 7.33.

Evaluation of the obtained abrasive for semiconductor was carried out in the same manner as in Example 1. The composition of the abrasive for semiconductors is shown in Table 1, and the evaluation results are shown in Table 2.

[Example 4]
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water to a concentration of 0.1% by mass, and further, ammonium nitrate is added to 0.1% by mass and pullulan is added to 0.02% by mass. Was made. By mixing the abrasive liquid mixture A and the additive liquid B4 with stirring, the abrasive concentration is 0.25% by mass, the ammonium polyacrylate concentration is 0.05% by mass, the ammonium nitrate concentration is 0.05% by mass, and the pullulan concentration. A 0.005 mass% abrasive for semiconductor was produced. Its pH was 7.33.

[Example 5]
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water so as to have a concentration of 0.1% by mass, and further, ammonium nitrate is added at 0.1% by mass and pullulan is added at 0.04% by mass to obtain additive liquid B5. Was made. By mixing the abrasive mixture liquid A and the additive liquid B5 with stirring, the abrasive concentration is 0.25% by mass, the ammonium polyacrylate concentration is 0.05% by mass, the ammonium nitrate concentration is 0.05% by mass, and the pullulan concentration. A 0.02 mass% abrasive for semiconductor was produced. Its pH was 7.73.

[Example 6]
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water to a concentration of 0.04% by mass, and ammonium nitrate is further added to a concentration of 0.1% by mass and pullulan is added to a concentration of 0.02% by mass. B6 was produced. By mixing the abrasive mixture liquid A and the additive liquid B6 with stirring, the abrasive concentration is 0.25% by mass, the ammonium polyacrylate concentration is 0.02% by mass, the ammonium nitrate concentration is 0.05% by mass, and the pullulan concentration. A 0.01% by mass semiconductor abrasive was prepared. Its pH was 7.61.

[Example 7]
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, an additive solution B7 was prepared by adding 0.1% by mass of ammonium nitrate and 0.02% by mass of pullulan in deionized water. By mixing the abrasive mixture A and the additive liquid B7 with stirring, the abrasive concentration 0.25% by mass, ammonium polyacrylate concentration 0.002% by mass, ammonium nitrate concentration 0.05% by mass, pullulan concentration A 0.01% by mass semiconductor abrasive was prepared. Its pH was 7.02.

[Example 8]
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate was dissolved in deionized water to a concentration of 0.1% by mass, and pullulan was added to a concentration of 0.02% by mass to prepare an additive solution B8. By mixing the abrasive mixture A and the additive liquid B8 while stirring, for semiconductors having an abrasive concentration of 0.25% by mass, an ammonium polyacrylate concentration of 0.05% by mass, and a pullulan concentration of 0.01% by mass. An abrasive was prepared. Its pH was 8.15.

[Example 9]
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water to a concentration of 0.04% by mass, and nitric acid is added to 0.004% by mass and pullulan to 0.02% by mass, and additive solution B9 is added. Was made. By mixing the abrasive mixture A and the additive liquid B9 with stirring, the abrasive concentration 0.25% by mass, the ammonium polyacrylate concentration 0.02% by mass, the nitric acid concentration 0.002% by mass, and the pullulan concentration. A 0.01% by mass semiconductor abrasive was prepared. Its pH was 7.63.

[Example 10] (Comparative Example)
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate was dissolved in deionized water to a concentration of 0.1% by mass to prepare additive liquid B10. By mixing the abrasive grain mixture A and the additive liquid B10 with stirring, a semiconductor abrasive having an abrasive grain concentration of 0.25 mass% and an ammonium polyacrylate concentration of 0.05 mass% was produced. Its pH was 8.2.

[Example 11] (Comparative Example)
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate was dissolved in deionized water to a concentration of 0.1% by mass, and ammonium nitrate was further added to a concentration of 0.1% by mass to prepare additive solution B11. By mixing this abrasive grain mixture A and additive liquid B11 while stirring, for semiconductors having an abrasive grain concentration of 0.25 mass%, an ammonium polyacrylate concentration of 0.05 mass%, and an ammonium nitrate concentration of 0.05 mass% An abrasive was prepared. Its pH was 7.69.

[Example 12] (Comparative example)
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate was dissolved in deionized water to a concentration of 0.1% by mass, and nitric acid was added to a concentration of 0.009% by mass to prepare additive solution B12. By mixing the abrasive liquid mixture A and the additive liquid B12 while stirring, for semiconductors having an abrasive grain concentration of 0.25% by mass, an ammonium polyacrylate concentration of 0.05% by mass, and a nitric acid concentration of 0.0045% by mass. An abrasive was prepared. Its pH was 7.48.

[Example 13] (Comparative example)
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water so as to have a concentration of 0.1% by mass, and further, ammonium nitrate is added to 0.1% by mass and glucose is added to 0.04% by mass. Was made. By mixing the abrasive liquid mixture A and the additive liquid B13 while stirring, the abrasive grain concentration is 0.25% by mass, the ammonium polyacrylate concentration is 0.05% by mass, the ammonium nitrate concentration is 0.05% by mass, and the glucose concentration. A 0.02 mass% abrasive for semiconductor was produced. Its pH was 7.7.

[Example 14] (Comparative Example)
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water so as to have a concentration of 0.1% by mass, and further, ammonium nitrate is added at 0.1% by mass and trehalose is added at 0.05% by mass to obtain additive liquid B14. Was made. By mixing the abrasive mixture A and the additive liquid B14 with stirring, the abrasive concentration is 0.25% by mass, the ammonium polyacrylate concentration is 0.05% by mass, the ammonium nitrate concentration is 0.05% by mass, and the trehalose concentration. A 0.025% by mass semiconductor abrasive was prepared. Its pH was 7.7.

[Example 15] (Comparative example)
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water to a concentration of 0.1% by mass, and further ammonium nitrate is 0.1% by mass and PEG (polyethylene glycol molecular weight 20000) is 0.05% by mass. Additive solution B15 was prepared by addition. By mixing the abrasive mixture liquid A and the additive liquid B15 while stirring, the abrasive grain concentration is 0.25% by mass, the ammonium polyacrylate concentration is 0.05% by mass, the ammonium nitrate concentration is 0.05% by mass, polyethylene glycol. An abrasive for semiconductor having a (PEG) concentration of 0.025% by mass was prepared. Its pH was 7.7.

[Example 16] (Comparative Example)
Abrasive grain mixture A was prepared in the same manner as in Example 1. Next, ammonium polyacrylate is dissolved in deionized water to a concentration of 0.1% by mass, and further, ammonium nitrate is 0.1% by mass and PVP (polyvinylpyrrolidone, molecular weight 9000) is 0.02% by mass. To make an additive liquid B16. By mixing the abrasive mixture liquid A and the additive liquid B16 with stirring, the abrasive concentration is 0.25% by mass, the ammonium polyacrylate concentration is 0.05% by mass, the ammonium nitrate concentration is 0.05% by mass, polyvinylpyrrolidone. A semiconductor polishing agent having a (PVP) concentration of 0.01% by mass was produced. Its pH was 7.7.

The obtained semiconductor abrasive was evaluated in the same manner as in Example 1. The composition of the abrasive for semiconductors is shown in Table 1, and the evaluation results are shown in Table 2.
[Example 17] to [Example 21]
A semiconductor abrasive was produced in the same manner as in Example 8 except that the concentrations described in Table 3 were used.
The obtained semiconductor abrasive was evaluated in the same manner as in Example 1. The composition of the abrasive for semiconductors is shown in Table 3, and the evaluation results are shown in Table 4.

As described in Examples 1 to 7 and 17 to 21 in Table 1, when both ammonium nitrate and pullulan are included as additives, good polishing rate and uniformity are maintained, and good results are obtained. Yes. The polishing rate is preferably 1800 (Å / min) or more, and more preferably 1900 (Å / min) or more. Further, the uniformity is preferably 10% or less, particularly preferably 7% or less.

Also, as described in Examples 8 and 9 in Table 1, it can be seen that good results were obtained with pullulan alone, even without ammonium nitrate.

Examples 10 to 12, 15, and 16 in Table 1 are comparative examples that do not contain pullulan, and any of the examples has difficulty in uniformity and is not preferable. In addition, Examples 13 and 14 containing glucose and trehalose are monosaccharide and disaccharide, respectively, and are presumed to be inferior to pullulan because the effect of improving lubricity is lower than that of polysaccharide. The reason is presumed that the lubricity between the silicon oxide film, the polishing pad, and the polishing abrasive grains was improved by adding a polysaccharide such as pullulan during polishing. Moreover, this abrasive | polishing agent does not aggregate an abrasive grain, is excellent also in dispersion stability, and is advantageous also with respect to a polishing defect.

The abrasive of the present invention relates to a semiconductor abrasive and a polishing method for chemical mechanical polishing in a semiconductor device manufacturing process, and is particularly suitably applied to shallow trench isolation and planarization of an interlayer insulating film.
The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2009-061917 filed on March 13, 2009 are incorporated herein as the disclosure of the present invention. .

1: Silicon substrate 2: Silicon oxide film 3: Silicon nitride film 10: Trench groove 20: Depression 31: Semiconductor substrate 32: Polishing head 33: Polishing surface plate 34: Polishing pad 35: Polishing agent supply pipe 36: Polishing agent for semiconductor

Claims

An abrasive for semiconductors, comprising cerium oxide abrasive grains, water and polysaccharides, and further containing at least one selected from the group consisting of water-soluble organic polymers and anionic surfactants.
The semiconductor abrasive according to claim 1, wherein the water-soluble organic polymer and the anionic surfactant are polymers having a carboxylic acid group or a salt thereof.
The abrasive | polishing agent for semiconductors of Claim 1 or 2 which further contains ammonium nitrate.
The content of the cerium oxide is 0.1 to 5.0% by mass, the content of the polysaccharide is 0.005 to 20% by mass, and the total content of the water-soluble organic polymer and the anionic surfactant is The abrasive for semiconductors according to any one of claims 1 to 3, wherein the content is 0.001 to 0.5 mass% and the water content is 50 to 99.9 mass%.
The semiconductor polishing agent according to any one of claims 1 to 4, wherein the polysaccharide is pullulan and has a molecular weight of 50,000 to 300,000.
When ammonium acrylate is used as the water-soluble organic polymer and anionic surfactant, and the polysaccharide is pullulan, the proportion of pullulan and ammonium polyacrylate is 1% by mass. The semiconductor polishing slurry according to any one of claims 1 to 4, which is from .0005 to 1: 100.
The semiconductor abrasive according to claim 3, wherein when the polysaccharide is pullulan, the ratio of pullulan to ammonium nitrate is 1: 0.0005 to 1: 100 in mass%.
The semiconductor abrasive according to any one of claims 1 to 7, wherein the total content of alkali metal and alkaline earth metal is 100 ppm or less.
The semiconductor abrasive according to any one of claims 1 to 8, wherein the pH of the abrasive is 4 to 10.
10. The polishing agent for polishing a silicon oxide film of a substrate for a semiconductor device, comprising at least a silicon oxide film on the surface thereof according to any one of claims 1 to 9.
10. The method for producing a semiconductor abrasive according to claim 1, wherein the liquid A contains the cerium oxide abrasive grains and water, a polysaccharide, a water-soluble organic polymer, and an anionic surfactant. 1 or more types chosen from the group which consists of, and B liquid containing water are mixed, The manufacturing method of the abrasive | polishing agent for semiconductors characterized by the above-mentioned.
A polishing agent for semiconductor according to any one of claims 1 to 9 is used as the polishing agent in a polishing method in which a polishing target and a polishing pad are brought into contact with each other and relatively moved while supplying a polishing agent for semiconductor. A polishing method comprising polishing a semiconductor substrate as the surface to be polished.
13. The polishing method according to claim 12, wherein the semiconductor substrate is a substrate for a semiconductor device including at least a silicon oxide film on a surface thereof, and a surface to be polished is the silicon oxide film.