Silica microparticle dispersion for polishing, slurry for polishing, and method for producing silica microparticle dispersion for polishing

Abstract

To provide a silica microparticle dispersion which, when applied to polishing, shows an excellent polishing speed.SOLUTION: A silica microparticle dispersion for polishing comprises a silica microparticle dispersion obtained by dispersing silica microparticles in a solvent, the silica microparticles satisfying the following conditions 1) to 3): 1) the average particle size (the particle size in terms of specific surface area) (Dc) is in a range of 38 nm to 50 nm; 2) the value of the short diameter / long diameter ratio is 0.47 to 0.90; and 3) in the pore volume distribution of the silica microparticles when dry, the average pore diameter is in the range of 6.0 nm to 17.0 nm, and in D10, D50 and D90 (where D10 is the 10% cumulative pore diameter from the smallest pore diameter, D50 is likewise the 50% cumulative pore diameter, and D90 is likewise the 90% cumulative pore diameter) in the pore volume distribution, the value of (D90-D10) / D50 is 2.3 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a silica fine particle dispersion liquid applicable to a polishing slurry or a polishing composition for polishing electronic components such as magnetic recording media such as hard disks or semiconductor substrates, a method for producing the same, and a polishing slurry containing the silica fine particle dispersion liquid for polishing. In particular, the present invention relates to a polishing slurry suitable for surface polishing of substrates for magnetic recording media such as aluminum magnetic disk substrates or glass magnetic disk substrates.

Background Art

[0002] Conventionally, as means for improving the polishing rate by a polishing abrasive grain dispersion liquid or a polishing slurry, typically, means based on characteristics such as the material of the polishing abrasive grain, the shape of the polishing abrasive grain, the particle size distribution of the polishing abrasive grain, and a polishing abrasive grain in which different kinds of abrasive grains are mixed have been proposed. Known polishing abrasive grains (polishing particles) include, for example, silica fine particle dispersion liquids (silica sols), inorganic composite fine particle dispersion liquids, fumed silica, or fumed alumina.

[0003] As an example focusing on the material of the polishing abrasive grain, for example, Patent Document 1 discloses a polishing composition that can further highly suppress defects caused by alumina abrasive grains and residual alumina by using silica particles having a specific aspect ratio and not containing alumina abrasive grains as the abrasive grains.

[0004] As an example focusing on the shape of the polishing abrasive grain, for example, Patent Document 2 discloses a method of preparing irregularly shaped porous gels by pulverizing porous silica gels with a bead mill or the like, and growing the particles of the irregularly shaped porous gels with silicic acid or the like to obtain particles having a large size and a high degree of irregularity.

[0005] As an example focusing on the particle size distribution of abrasive grains for polishing, for example, Patent Document 3 describes silica-based particle groups that have a wide particle size distribution from the small particle size side to the large particle size side, the particle size distribution is a non-normal distribution, and the areas of the regions of the particle size distribution corresponding to each particle size range have a relatively uniform distribution. And although this silica-based particle group extends over a wide particle size range, the proportion of ultra-small particles and ultra-large particles is extremely small. Therefore, it is disclosed that the silica-based particle dispersion shows a high polishing rate, can suppress the residue of ultra-small particles on the substrate, and can also suppress scratches caused by ultra-large particles.

[0006] As an example focusing on abrasive grains for polishing in which different types of abrasive grains for polishing are mixed, for example, Patent Document 4 discloses that in a silica particle dispersion in which two types of silica particles with non-overlapping average particle size ranges are dispersed in a solvent, when the diameter ratio range between the dry particle interstice diameter of the silica particles with a relatively large particle size range and the average particle size of the silica particles with a relatively small particle size, and the mass ratio range between the two are within specific ranges, the polishing rate is high and the decrease in the polishing rate can be suppressed over a longer period.

[0007] Also, Patent Document 5 describes a polishing liquid composition for a magnetic disk substrate containing non-spherical silica particles and spherical silica particles, in which the mass ratio range between the non-spherical silica particles and the spherical silica particles, the degree of non-sphericity of the non-spherical silica particles (the ratio between the volume average particle size by the dynamic light scattering method and the particle size converted to the specific surface area), and the total overlapping frequency of the volume particle size distribution are all within specific ranges. It is disclosed that this polishing liquid composition for a magnetic disk substrate does not use alumina particles that cause protrusion defects, so it can significantly reduce protrusion defects after rough polishing and finish polishing, and can further improve the removal rate of long-period defects without impairing productivity.

[0008] In the production of the polishing liquid composition for a magnetic disk substrate of Patent Document 5, it is necessary to adjust the mass ratio of non-spherical silica particles to spherical silica particles, the degree of irregularity of the non-spherical silica particles, and the overlapping frequency of the volume particle size distributions of both particles. There are many conditions to be considered during production, and it is not clear regarding the improvement of the polishing rate.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0010] As one method of obtaining a high polishing rate, as in Patent Document 4, a method of adding small-sized particles to relatively large particles with a relatively uniform particle size is known. In this method, during polishing, when the particles are pressed against the polishing pad and a packing structure is formed on the surface of the polishing pad, the small particles are filled into the inter-particle voids formed by the large particles. The inventors presume that this improves the density of the packing structure, and as a result, the polishing rate is improved by increasing the contact area between the abrasive grains and the polishing substrate. Therefore, in Patent Document 4, it is described that, as a guideline for the filling structure during polishing, attention is paid to the dry void size of large particles and the size of small particles, and the sizes are selected so that the dry void size formed by the large particles and the size of the small particles generally match. However, from the perspective of demanding a higher polishing rate, the polishing rate was insufficient. Although this is desirable from the perspective of increasing the density of the packing structure, when a load is further applied to the packing structure due to the unevenness of the pad during polishing or the rocking of the polishing platen, since the structure is too dense, it cannot become a denser structure, so the inventors presume that the structure is easily destroyed and instead becomes a sparse structure. The present inventors focused on the relationship between the pore information (pore volume distribution) of the dry aggregate of a silica fine particle dispersion obtained by mixing a non-spherical silica fine particle dispersion and a spherical silica fine particle dispersion with the polishing rate, and found that the polishing rate improves when a specific pore volume distribution is exhibited, thereby completing the present invention. That is, the silica fine particle dispersion of the present invention uses non-spherical particles as the large particle component and true spherical fine particles as the small particles, selects an optimal number ratio, and forms a structure such that the pore distribution of the packing structure formed by these two components of particles on the polishing pad during polishing becomes wide. That is, by selecting an optimal number ratio, a structure that does not become too dense is formed, and as a result, the pore distribution becomes wide. In the case of such a loose structure, even when a load is applied due to rocking from the platen or the like during polishing, a denser structure can be obtained and the packing structure is difficult to be destroyed. As a result, it is presumed that a dense packing structure is maintained, the contact area between the abrasive grains and the substrate is maintained, and the polishing rate is kept high. And the present inventors found that such a packing structure during polishing can be estimated by measuring the pore diameter or pore distribution of the dry powder of the silica fine particles.

[0011] An object of the present invention is to provide a silica fine particle dispersion for polishing, a slurry for polishing, and a method for producing a silica fine particle dispersion for polishing, which exhibit an excellent polishing rate when applied to polishing applications.

Means for Solving the Problems

[0012] The inventors focused on the relationship between the pore information (pore volume distribution) of the dry aggregate of a silica particle dispersion obtained by mixing a non-spherical silica particle dispersion and a spherical silica particle dispersion, and the polishing rate, and found that the polishing rate improves when a specific pore volume distribution is exhibited. Further, the inventors found that there is a relationship between the pore volume distribution in the dry aggregate of the particles serving as abrasive grains and the polishing rate by the abrasive grains, and completed the present invention. That is, the inventors found that the above problems can be solved by the following configuration.

[0013] According to one aspect of the present invention, there is provided a silica particle dispersion for polishing, which is composed of a silica particle dispersion in which silica particles satisfying the following conditions 1) to 3) are dispersed in a solvent. 1) The average particle diameter [particle diameter in terms of specific surface area] (Dc) is in the range of 38 nm or more and 50 nm or less. 2) The value of the minor axis / major axis ratio [image analysis method] is in the range of 0.47 or more and 0.90 or less. 3) In the pore volume distribution at the time of drying of the silica particles, the average pore diameter is in the range of 6.0 nm or more and 17.0 nm or less, and in D 10 , D 50 and D 90 (the cumulative 10% pore diameter from the smaller pore diameter is D 10 , the cumulative 50% pore diameter is similarly D 50 , and the cumulative 90% pore diameter is similarly D 90 ), the value of (D 90 - D 10 ) / D 50 is 2.3 or more. In the present specification, the particle diameter in terms of specific surface area of all the silica particles contained in the silica particle dispersion for polishing is represented by (Dc). Further, the particle diameter in terms of specific surface area of all the silica particles contained in the non-spherical silica particle dispersion as a raw material of the silica particle dispersion for polishing is represented by (NDc), and the particle diameter in terms of specific surface area of all the silica particles contained in the spherical silica particle dispersion is similarly represented by (SDc). Furthermore, let the average particle diameter of the non-spherical silica fine particles contained in the silica fine particle dispersion for polishing be represented by (NDi) and the average particle diameter of the spherical silica fine particles by (SDi) according to the image analysis method.

[0014] According to one aspect of the present invention, there is provided a polishing slurry containing the silica fine particle dispersion for polishing according to one aspect of the present invention, hydrogen peroxide, and an inorganic acid.

[0015] According to one aspect of the present invention, there is provided a method for producing the silica fine particle dispersion for polishing according to one aspect of the present invention, which contains non-spherical silica fine particles having a short-axis / long-axis ratio [image analysis method] value of less than 0.9 and having an average particle diameter [NDc] of the silica fine particles in the range of 45 nm or more and 360 nm or less, and spherical silica fine particles having a short-axis / long-axis ratio [image analysis method] value of 0.9 or more and having an average particle diameter [SDc] of the silica fine particles in the range of 10 nm or more and 45 nm or less. The non-spherical silica fine particle dispersion and the spherical silica fine particle dispersion are mixed so as to satisfy the following conditions A) and B). A) The value [SDc / NDc] of the ratio of the average particle diameter [SDc] of the silica fine particles in the spherical silica fine particle dispersion to the average particle diameter [NDc] of the silica fine particles in the non-spherical silica fine particle dispersion is in the range of 0.05 or more and 0.80 or less. B) The ratio (mass%) [in terms of silica content] of the non-spherical silica fine particle dispersion to the entire silica fine particle dispersion for polishing is in the range of 75 mass% or more and 98 mass% or less. In the present specification, non-spherical silica fine particles having a short-axis / long-axis ratio [image analysis method] value of less than 0.9 are also referred to as "irregularly shaped silica fine particles".

Advantages of the Invention

[0016] According to the method for producing the silica fine particle dispersion for polishing according to the present invention, by preliminarily adjusting the average particle diameters, the ratio of the average particle diameters, and the weight ratio of the non-spherical silica fine particles and the spherical silica fine particles, and selecting the optimal mixing ratio of the non-spherical silica fine particles and the spherical silica fine particles, the silica fine particle dispersion for polishing according to the present invention can be prepared. The silica fine particle dispersion liquid for polishing of the present invention satisfies a characteristic pore volume distribution during drying and is applied to the polishing of a magnetic disk substrate to obtain an excellent polishing rate.

Embodiments for Carrying Out the Invention

[0017] [Silica Fine Particle Dispersion Liquid for Polishing] First, the silica fine particle dispersion liquid for polishing according to this embodiment will be described. The silica fine particle dispersion liquid for polishing according to this embodiment is one in which silica fine particles are dispersed in a solvent as abrasive grains for polishing. Here, the silica fine particles need to satisfy the following conditions 1) to 3). 1) The average particle diameter [particle diameter in terms of specific surface area] (Dc) is in the range of 38 nm or more and 50 nm or less. 2) The value of the minor axis / major axis ratio [image analysis method] is in the range of 0.47 or more and 0.90 or less. 3) In the pore volume distribution of the silica fine particles during drying, the average pore diameter is in the range of 6.0 nm or more and 17.0 nm or less, and in D in the pore volume distribution 10 , D 50 and D 90 (the cumulative 10% pore diameter from the smaller pore diameter is D 10 , similarly the cumulative 50% pore diameter is D 50 , similarly the cumulative 90% pore diameter is D 90 ), (D 90 - D 10 ) / D 50 is 2.3 or more. In this specification, the "silica fine particle dispersion liquid for polishing" may sometimes be simply referred to as the "dispersion liquid".

[0018] (Average Particle Diameter of Silica Fine Particles) The average particle diameter [particle diameter in terms of specific surface area] (Dc) of the silica fine particles dispersed in the dispersion liquid according to this embodiment is the particle diameter in terms of specific surface area. This measurement method is described in the examples of this specification. The average particle diameter (Dc) of the silica fine particles needs to be in the range of 38 nm or more and 50 nm or less as described above. If it is within this range, the polishing rate is high, scratches are less likely to occur, and the surface roughness of the substrate is also good. When the average particle diameter is less than 38 nm, the polishing rate decreases because the size is small. On the other hand, when the average particle diameter exceeds 50 nm, although a high polishing rate can be obtained, scratches are likely to occur and the surface roughness of the polished substrate deteriorates. From the same viewpoint, the average particle diameter (Dc) of the silica fine particles is preferably in the range of 39 nm or more and 48 nm or less.

[0019] (Aspect ratio of the minor axis to the major axis of the silica fine particles) The aspect ratio [image analysis method] of the silica fine particles dispersed in the dispersion according to the present embodiment needs to be in the range of 0.47 or more and 0.90 or less as described above. This measurement method is described in the examples of this specification. If the aspect ratio of the silica fine particles is in the range of 0.47 or more and 0.90 or less, since it is composed of irregularly shaped particles and spherical particles with an appropriate degree of irregularity, the polishing rate is high, and scratches and the surface roughness of the substrate can be kept low. When the aspect ratio of the silica fine particles is less than 0.47, since the proportion of irregularly shaped particles is too high or the proportion of particles with a high degree of irregularity is large, although the polishing rate is high, scratches are likely to occur. On the other hand, when the aspect ratio of the silica fine particles exceeds 0.90, the proportion of spherical particles is high or the proportion of irregularly shaped particles is low, so the polishing rate decreases. From the same viewpoint, the aspect ratio of the silica fine particles is preferably in the range of 0.50 or more and 0.89 or less.

[0020] (Pore volume distribution of silica fine particles in the polishing silica fine particle dispersion liquid when dried) In the present invention, the packing structure formed by the particles on the polishing pad during polishing was inferred from the pore state of the dried body obtained by drying the silica fine particle dispersion liquid, and it was found that there is an optimal pore distribution. That is, D in the pore volume distribution of the dried body obtained by drying the silica fine particle dispersion liquid 10 , D 50 , D 90 (The cumulative 10% diameter from the smaller size is D10 and, similarly, the cumulative 50% diameter is D 50 and, similarly, the cumulative 90% diameter is D 90 In the case where (let them be), the pore distribution width (D 90 - D 10 ) / D 50 is 2.3 or more, it has been found that the polishing rate is improved. It is said that the polishing abrasive grains form a dense packing structure between the pad and the substrate to which pressure is applied, particularly at the convex portions of the pad, and polishing is performed by contacting the substrate as this structure. The present inventors have found that the pore distribution width is effective as a measure indicating the state of this packing structure. When the pore distribution width of the dried body is large, it indicates that the packing structure of the silica particles formed on the polishing pad forms a somewhat loose structure, and when the pore distribution width is small, it indicates that a dense structure is formed. During polishing, a load is applied to this packing structure due to various factors such as minute irregularities on the polishing pad or the substrate, oscillation of the polishing platen, and pressure fluctuations. However, when the packing structure is dense, since it cannot take a denser structure any more, the structure is broken, and conversely, it becomes a sparse structure and the polishing rate decreases. On the other hand, in the case where the pore distribution is wide, that is, in the case of a somewhat loose structure, it is estimated by the present inventors that a denser structure can be formed even when a load is applied, and thus a high polishing rate is exhibited.

[0021] Regarding the silica fine particles dispersed in the dispersion liquid according to the present embodiment, as described above, the average pore diameter is in the range of 6.0 nm or more and 17.0 nm or less, and in the pore volume distribution, D 10 , D 50 and D 90 (the cumulative 10% pore diameter from the smaller pore diameter side is D 10 , similarly, the cumulative 50% pore diameter is D 50 , similarly, the cumulative 90% pore diameter is D 90 let them be), in (D 90 - D 10 ) / D 50 , the value needs to be 2.3 or more. If the average pore diameter is in the range of 6.0 nm or more and 17.0 nm or less, the sizes and the number ratio of the small particle component and the large particle component are optimal, so that a high polishing rate can be exhibited while suppressing scratches or surface roughness. When it exceeds 17.0 nm, both the large particle component and the small particle component have large sizes or their balance is poor, and the average particle diameter is too large. Therefore, although the polishing rate is high, scratches and surface roughness deteriorate. When the pore diameter is less than 6.0 nm, since the small particle component is excessive, the polishing rate is insufficient. From the same viewpoint, the average pore diameter is preferably in the range of 6.3 nm or more and 13.0 nm or less. Also, (D 90 -D 10 ) / D 50 If the value of is 2.3 or more, a loose structure is formed, and even if there is a load change due to swinging, a relatively dense packing structure can be maintained, showing a high polishing rate. On the other hand, when it is less than 2.3, since the packing structure is too dense, the packing structure cannot be maintained due to the load change caused by swinging, and instead, a sparse structure is formed, and the polishing rate decreases, which is not preferable. In addition, (D 90 -D 10 ) / D 50 The upper limit of the value of is not particularly limited. However, from a practical viewpoint, for example, (D 90 -D 10 ) / D 50 The value of is preferably 2.3 or more and 5.0 or less.

[0022] (Ratio of the number of non-spherical silica fine particles) In the dispersion according to the present embodiment, the ratio of the number of non-spherical silica fine particles having a short diameter / long diameter ratio [image analysis method] of less than 0.9 is preferably in the range of 7% by number or more and 50% by number or less. The number ratio of non-spherical silica fine particles affects the polishing rate and scratches or surface roughness. If this number ratio is in the range of 7% to 50% by number, since the ratio of irregular particles to true spherical particles is appropriate, a high polishing rate, low scratches, and low surface roughness can be achieved. When this number ratio is less than 7% by number, the number of irregular particles decreases, and the polishing rate tends to be low. On the other hand, when the number ratio exceeds 50%, although the polishing rate is high, scratches are likely to occur, and the surface roughness of the substrate also tends to deteriorate. From the same perspective, the number ratio of non-spherical silica fine particles is more preferably in the range of 9% to 45% by number.

[0023] (Average particle diameter, etc. by image analysis method of silica fine particles) In the dispersion liquid according to this embodiment, the average particle diameter [image analysis method] (NDi) of non-spherical silica fine particles with a minor axis / major axis ratio [image analysis method] value less than 0.9 and the average particle diameter [image analysis method] (SDi) of spherical silica fine particles with a minor axis / major axis ratio [image analysis method] value of 0.9 or more preferably satisfy the conditions shown by the following mathematical formula (F1). 0.1 ≦ SDi / NDi ≦ 0.6 ··· (F1) This value of SDi / NDi indicates the particle diameter ratio of irregular particles with a large size and true spherical particles with a small size, that is, it is one of the factors determining the density or looseness of the packing structure formed during polishing. If 0.1 ≦ SDi / NDi ≦ 0.6, the size difference between irregular particles and true spherical particles is appropriate, and the true spherical particles are appropriately filled in the inter-particle voids of the irregular particles, so that a packing structure that is not too dense and is somewhat loose can be formed, and the polishing rate is improved. When the value of SDi / NDi exceeds 0.6, the size of the true spherical particles is too large, and the true spherical particles cannot be well filled in the inter-particle voids of the irregular particles, and the packing structure becomes sparse, and the polishing rate tends to decrease. When the value of SDi / NDi is less than 0.1, the size of the true spherical particles is too small, and although a dense packing structure can be obtained, it becomes too dense, and the structure is easily broken, so the polishing rate tends to decrease. From the same perspective, the value of SDi / NDi is more preferably in the range of 0.2 or more and 0.6 or less.

[0024] (Concentration and pH of the silica fine particle dispersion liquid) The silica concentration of the dispersion liquid according to this embodiment is preferably in the range of 1% by mass or more and 50% by mass or less. If the silica concentration is within the above range, the stability of the silica fine particle dispersion liquid is maintained, and it is more economical and suitable. When the silica concentration is less than 1% by mass, the concentration is too low more than necessary, so the handling amount becomes too large, and the economy tends to deteriorate in transportation and storage. When the silica concentration exceeds 50% by mass, the stability of the silica sol becomes low, and aggregation tends to occur. From the same perspective, the silica concentration is more preferably in the range of 3% by mass or more and 50% by mass or less. The pH of the dispersion liquid according to this embodiment is preferably in the range of 9.0 or more and 11.0 or less. If the pH is within the above range, aggregation of the silica sol is suppressed, and it is possible to ensure stability and it is suitable. When the pH is less than 9.0, the stability of the silica sol becomes low, and aggregation tends to occur. When the pH exceeds 11.0, the stability of the silica sol becomes low, and aggregation tends to occur. From the same perspective, the pH is more preferably in the range of 9.5 or more and 10.5 or less.

[0025] (Solvent) The dispersion liquid according to this embodiment is formed by dispersing silica fine particles (hereinafter, may also be referred to as a particle group) that satisfy the conditions of 1) to 3) above in a solvent. Here, examples of the solvent include water, alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, water-soluble organic solvents such as ethers, esters, and ketones. A mixed solvent composed of water and an organic solvent may also be used.

[0026] [Composition for polishing a magnetic disk substrate] Next, the composition for polishing a magnetic disk substrate according to this embodiment will be described. The composition for polishing a magnetic disk substrate according to the present embodiment contains the dispersion liquid according to the present embodiment, or a particle group satisfying the conditions 1) to 3), hydrogen peroxide, and an inorganic acid. The composition for polishing a magnetic disk substrate is a concept including a polishing slurry. A composition for polishing a magnetic disk substrate having a low solid content or a composition for polishing a magnetic disk substrate diluted with water or the like is usually referred to as a polishing slurry. In this specification, the "composition for polishing a magnetic disk substrate" may be simply referred to as "composition".

[0027] The composition according to the present embodiment may further contain other components in the dispersion liquid according to the present embodiment. As the other components, at least one component selected from a polishing accelerator, a surfactant, a hydrophilic compound, a heterocyclic compound, a pH adjuster, and a pH buffer can be used.

[0028] Examples of the polishing accelerator include acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and hydrofluoric acid, or sodium salts, potassium salts, ammonium salts of these acids, and mixtures thereof. When the composition according to the present embodiment contains these polishing accelerators, when polishing a workpiece made of a composite component, by promoting the polishing rate of a specific component of the workpiece, a finally flat polishing surface can be obtained. In the composition according to the present embodiment, it is preferable to contain an inorganic acid as the polishing accelerator.

[0029] When the composition according to the present embodiment contains a polishing accelerator, its content is preferably in the range of 0.1% by mass or more and 10% by mass or less, and more preferably in the range of 0.5% by mass or more and 5% by mass or less. In order to improve the dispersibility and stability of the composition according to the present embodiment, a cationic, anionic, nonionic, or amphoteric surfactant, or a hydrophilic compound can be added.

[0030] Both the surfactant and the hydrophilic compound have the effect of reducing the contact angle with the surface to be polished and promoting uniform polishing. As at least one of the surfactant and the hydrophilic compound, for example, those selected from the following group can be used.

[0031] Examples of the anionic surfactant include carboxylates, sulfonates, sulfate esters, and phosphate esters. Examples of the carboxylate include soap, N-acyl amino acid salts, polyoxyethylene or polyoxypropylene alkyl ether carboxylates, and acylated peptides. Examples of the sulfonate include alkyl sulfonates, alkyl benzene and alkyl naphthalene sulfonates, naphthalene sulfonates, sulfosuccinates, α-olefin sulfonates, and N-acyl sulfonates. Examples of the sulfate ester include sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfates, and alkyl amide sulfates. Examples of the phosphate ester include alkyl phosphates, polyoxyethylene or polyoxypropylene alkyl allyl ether phosphates.

[0032] Examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, and imidazolinium salts. Examples of the amphoteric surfactant include carboxybetaine type, sulfobetaine type, aminocarboxylates, imidazolinium betaine, lecithin, and alkylamine oxides.

[0033] Examples of the nonionic surfactant include ether type, ether ester type, ester type, and nitrogen-containing type. As the ether type, polyoxyethylene alkyl and alkylphenyl ethers, alkyl allyl formaldehyde condensed polyoxyethylene ethers, polyoxyethylene polyoxypropylene block polymers, and polyoxyethylene polyoxypropylene alkyl ethers, etc. can be mentioned. As the ether ester type, polyoxyethylene ethers of glycerin esters, polyoxyethylene ethers of sorbitan esters, and polyoxyethylene ethers of sorbitol esters, etc. can be mentioned. As the ester type, polyethylene glycol fatty acid esters, glycerin esters, polyglycerin esters, sorbitan esters, propylene glycol esters, and sucrose esters, etc. can be mentioned. As the nitrogen-containing type, fatty acid alkanolamides, polyoxyethylene fatty acid amides, and polyoxyethylene alkyl amides, etc. can be mentioned. In addition, fluorine-based surfactants, etc. can be mentioned.

[0034] As the surfactant, an anionic surfactant or a nonionic surfactant is preferable. Also, as the salt, ammonium salts, potassium salts, and sodium salts, etc. can be mentioned, and particularly, ammonium salts and potassium salts are preferable.

[0035] Furthermore, as other surfactants, hydrophilic compounds, etc., esters (such as glycerin esters, sorbitan esters, and alanine ethyl esters), ethers (such as 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 glycol, alkyl polypropylene glycol alkyl ether, alkyl polypropylene glycol alkenyl ether, and 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), polycarboxylic acids and their salts (such as polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, ammonium polymethacrylate salt, sodium polymethacrylate salt, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly(p-styrenecarboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, ammonium polyacrylate salt, sodium polyacrylate salt, polyamic acid, ammonium polyamic acid salt, sodium polyamic acid salt, and polyglyoxylic acid), vinyl polymers (such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrolein), sulfonic acids and their salts (such as ammonium methyl taurate salt, sodium methyl taurate salt, sodium methyl sulfate salt, ammonium ethyl sulfate salt, ammonium butyl sulfate salt, sodium vinyl sulfonate salt, sodium 1-allyl sulfonate salt, sodium 2-allyl sulfonate salt, sodium methoxymethyl sulfonate salt, ammonium ethoxymethyl sulfonate salt, sodium 3-ethoxypropyl sulfonate salt, etc.), and amides (such as propionamide,Examples include acrylamide, methylurea, nicotinamide, succinamide, and sulfanilamide, etc.

[0036] In addition, when the substrate to be polished is a glass substrate or the like, any surfactant can be preferably used. However, when the substrate to be polished is a silicon substrate for semiconductor integrated circuits or the like and it is desired to avoid the influence of contamination by alkali metals, alkaline earth metals, or halides, etc., it is desirable to use an acid or its ammonium salt-based surfactant.

[0037] When the composition according to this embodiment contains at least one of a surfactant and a hydrophilic compound, the content thereof is preferably 0.001 g or more and 10 g or less, more preferably 0.01 g or more and 5 g or less, and particularly preferably 0.1 g or more and 3 g or less per liter of the composition according to this embodiment as the total amount.

[0038] The surfactant or the hydrophilic compound may be only one kind, or two or more kinds may be used, and different kinds can also be used in combination.

[0039] Regarding the composition according to this embodiment, when the substrate to be polished contains a metal, a passive layer or a dissolution inhibition layer may be formed on the metal, and a heterocyclic compound may be contained for the purpose of suppressing the erosion of the substrate to be polished. Here, the "heterocyclic compound" is a compound having a heterocyclic ring containing one or more heteroatoms. The heteroatom means an atom other than a carbon atom or a hydrogen atom. The heterocyclic ring means a cyclic compound having at least one heteroatom. The heteroatom means only an atom forming a constituent part of the ring system of the heterocyclic ring, and does not mean an atom located outside the ring system, separated from the ring system by at least one non-conjugated single bond, or a part of a further substituent of the ring system. Preferred heteroatoms 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, and tetrazole 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-amino-1,2,4-triazole, and 3,5-diamino-1,2,4-triazole can be mentioned, but are not limited thereto.

[0040] When the composition according to this embodiment contains a heterocyclic compound, its content is preferably 0.001% by mass or more and 1.0% by mass or less, more preferably 0.001% by mass or more and 0.7% by mass or less, and particularly preferably 0.002% by mass or more and 0.4% by mass or less.

[0041] If necessary, such as to enhance the effects of the above additives, an acid or a base can be added to adjust the pH of the polishing composition.

[0042] When adjusting the composition according to this embodiment to pH 7 or higher, an alkaline substance can be used as the pH adjuster. As the pH adjuster, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, and tetramethylamine can be used.

[0043] When adjusting the composition according to this embodiment to a pH less than 7, an acidic substance can be used as the pH adjuster. As the pH adjuster, hydroxy acids such as lactic acid, citric acid, malic acid, tartaric acid, and glyceric acid can be used.

[0044] In order to keep the pH value of the composition according to this embodiment constant, a pH buffer may be used. As the pH buffer, for example, phosphates and borates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium tetraborate tetrahydrate, or organic acids can be used.

[0045] [Method for producing silica fine particle dispersion for polishing] Next, the method for producing the dispersion according to this embodiment will be described. The method for producing the dispersion according to this embodiment is a method for producing the dispersion according to the above-described embodiment. And it contains non-spherical silica fine particles having a value of the minor axis / major axis ratio [image analysis method] of less than 0.9 and an average particle diameter [NDc] of the silica fine particles in the range of 45 nm or more and 360 nm or less, and a minor axis / major axis ratio [image analysis method] of 0.9 or more. A spherical silica fine particle dispersion containing spherical silica fine particles and having an average particle diameter [SDc] of the silica fine particles in the range of 10 nm or more and 45 nm or less is mixed so as to satisfy the following conditions A) and B). A) The value [SDc / NDc] of the ratio of the average particle diameter [SDc] of the silica fine particles in the spherical silica fine particle dispersion to the average particle diameter [NDc] of the silica fine particles in the non-spherical silica fine particle dispersion is in the range of 0.05 or more and 0.80 or less. B) The ratio (mass%) [in terms of silica content] of the non-spherical silica fine particle dispersion to the entire silica fine particle dispersion for polishing is in the range of 75 mass% or more and 98 mass% or less.

[0046] (Dispersion of Non-spherical Silica Fine Particles and Dispersion of Spherical Silica Fine Particles) The non-spherical silica fine particle dispersion used as a raw material preferably has an average particle diameter [NDc] of the non-spherical silica fine particles contained therein in the range of 45 nm or more and 360 nm or less, and a minor axis / major axis ratio in the range of 0.45 or more and less than 0.9. Here, the average particle diameter of the non-spherical silica fine particles represents the particle diameter in terms of specific surface area conversion. If the average particle diameter is within the above range, when used in the silica fine particle dispersion according to the present embodiment, while showing a high polishing rate, scratches can be suppressed. When the average particle diameter is less than 45 nm, since the size is too small, when used in the silica fine particle dispersion according to the present embodiment, the polishing rate decreases. When the average particle diameter exceeds 360 nm, since the size is too large, when used in the silica fine particle dispersion according to the present embodiment, scratches tend to occur frequently. From the same viewpoint, the average particle diameter of the non-spherical silica fine particles is preferably in the range of 45 nm or more and 100 nm or less. The minor axis / major axis ratio of the non-spherical silica fine particles used as a raw material is desirably 0.45 or more and less than 0.9. When the minor axis / major axis ratio is 0.45 or more and less than 0.9, since the degree of irregularity is appropriate, the polishing rate is high and scratches can also be suppressed. When the minor axis / major axis ratio is less than 0.45, since the degree of irregularity is high, although the polishing rate is fast, scratches are likely to occur. On the other hand, when the minor axis / major axis ratio exceeds 0.9, since the degree of irregularity is small, scratches are less likely to occur but the polishing rate decreases. From the same viewpoint, the minor axis / major axis ratio is preferably in the range of 0.5 or more and 0.86 or less.

[0047] (Dispersion of Spherical Silica Fine Particles) The spherical silica fine particle dispersion used as a raw material preferably has an average particle diameter [NDc] of the non-spherical silica fine particles contained therein in the range of 10 nm or more and 45 nm or less, and a minor axis / major axis ratio in the range of 0.9 or more and 1 or less. Here, the average particle diameter of the spherical silica fine particles represents the particle diameter in terms of specific surface area conversion. If the average particle diameter is within the above range, it is preferable because it has an excellent balance between the polishing rate and scratches. Also, it is preferable because it enters the inter-particle voids of irregularly shaped particles with a large size and forms an appropriate packing structure. When the average particle diameter is less than 10 nm, since the size is too small, the polishing rate decreases. Also, when it enters the inter-particle voids of irregularly shaped particles, it is not preferable because it forms a dense packing structure. Further, when the average particle diameter exceeds 45 nm, it becomes difficult to enter the inter-particle voids of irregularly shaped particles, and thus the polishing rate tends not to improve. From the same viewpoint, the average particle diameter is preferably in the range of 10 nm or more and 35 nm or less. Also, if the minor axis / major axis ratio is within the above range, such particles can be said to be almost spherical. Such spherical particles are preferable because they are easily filled into the inter-particle voids of irregularly shaped particles with a large size. For example, the minor axis / major axis ratio is preferably 0.92 or more.

[0048] (Ratio of the average particle diameter of spherical silica fine particles to the average particle diameter of non-spherical silica fine particles) In the method for producing the dispersion according to the present embodiment, the value [SDc / NDc] of the ratio of the average particle diameter [SDc] of the silica fine particles in the spherical silica fine particle dispersion to the average particle diameter [NDc] of the silica fine particles in the non-spherical silica fine particle dispersion needs to be in the range of 0.05 or more and 0.80 or less. If the value of the ratio [SDc / NDc] is within the above range, since the size difference between the large-sized irregular silica and the small-sized spherical particles is appropriate, the spherical silica is appropriately filled into the inter-particle voids of the irregular silica, a loose packing structure is formed, and a desired pore distribution width is easily obtained. When the value of the ratio [SDc / NDc] is less than 0.05, the size of the spherical particles is too large, making it difficult to enter the inter-particle voids of the irregular silica particles, and it is difficult to obtain a desired pore distribution width. When the value of the ratio [SDc / NDc] exceeds 0.80, since the particle diameter difference is too large, a dense packing structure is formed in the inter-particle voids of the irregular particles, and it is difficult to obtain a desired pore distribution width. From the same viewpoint, the range of the value of the ratio [SDc / NDc] is preferably in the range of 0.10 or more and 0.70 or less.

[0049] (Ratio of non-spherical silica fine particle dispersion in silica fine particle dispersion for polishing) In the method for producing the dispersion according to the present embodiment, the ratio (mass%) [in terms of silica content] of the non-spherical silica fine particle dispersion to the entire silica fine particle dispersion for polishing needs to be in the range of 75% by mass or more and 98% by mass or less. If it is within this range, spherical particles can appropriately fill the inter-particle voids of irregularly shaped particles with a large size, and a desired pore size distribution width can be easily obtained. When the ratio is less than 75% by mass, the number of irregularly shaped silica particles with a large size is insufficient, and spherical particles become excessive beyond the inter-particle voids, so that the desired pore diameter and pore size distribution width cannot be obtained, and the polishing rate tends to decrease. When the ratio exceeds 98% by mass, the number of spherical particles is insufficient, so that the inter-particle voids are not sufficiently filled with spherical particles, and the desired pore diameter and pore size distribution width tend to be difficult to obtain. From the same viewpoint, the ratio of the non-spherical silica fine particle dispersion is preferably in the range of 78% by mass or more and 96% by mass or less.

Examples

[0050] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Also, regarding the measurement methods of various properties of the silica fine particles or the silica fine particle dispersion in the examples and comparative examples, unless otherwise specified, the methods described below were used.

[0051] 1. Measurement and calculation of the average particle diameter (Dc) in terms of specific surface area conversion of silica fine particles for polishing, etc. The average particle diameter (Dc) in terms of specific surface area conversion of the silica fine particles for polishing can be obtained by measuring the specific surface area Sa of the silica fine particles and using the following formula. Average particle diameter (Dc) (nm) = 6000 / (ρ × Sa) (Here, ρ represents the density of the silica fine particles, 2.2 [g / cm 3 .) The specific surface area of the silica fine particles for polishing is 100m 2When it was 1 / g or more, since sintering proceeded during firing in the BET method, in this case, the specific surface area (SA) was determined by the titration method, and the particle size in terms of specific surface area was calculated from the formula of average particle size (Dc) = 6000 / (ρ × SA). In the present invention, the average particle size in terms of specific surface area is applied not only to the average particle size of the silica fine particles for polishing but also to the average particle sizes of the non-spherical silica fine particle dispersion (non-spherical silica fine particles) and the spherical silica fine particle dispersion (spherical silica fine particles), which are raw materials for producing the silica fine particle dispersion for polishing.

[0052] (BET method) 50 mL of the silica fine particle dispersion for polishing (silica concentration: 40% by mass) was adjusted to pH 3.5 with HNO3, 40 mL of 1-propanol was added, and the sample dried at 110 °C for 16 hours was pulverized in a mortar and then fired at 500 °C for 1 hour in a muffle furnace to obtain a measurement sample. Then, using a specific surface area measuring device (manufactured by Yuasa Ionics, model number Multi-Sorb 12), the specific surface area was calculated by the BET one-point method from the nitrogen adsorption amount using the nitrogen adsorption method (BET method). Specifically, 0.5 g of the sample was placed in a measurement cell, degassed at 300 °C for 20 minutes in a mixed gas stream of 30 v% nitrogen and 70 v% helium, and then the sample was kept at liquid nitrogen temperature in the above mixed gas stream to allow nitrogen to be adsorbed on the sample in equilibrium. Next, while flowing the above mixed gas, the sample temperature was gradually raised to room temperature, the amount of nitrogen desorbed during that time was detected, and the specific surface area of the silica fine particles for polishing was calculated from a calibration curve prepared in advance. Then, the obtained specific surface area (Sa) was substituted into the above-mentioned conversion formula from specific surface area to particle size to obtain the average particle size.

[0053] (Titration method) Here, the titration method is as follows. First, a sample (silica fine particle dispersion for polishing) corresponding to 1.5 g as SiO2 was collected in a beaker and then transferred to a thermostatic reaction tank (25 °C), and pure water was added to make the liquid volume 90 mL. The following operations were carried out in the thermostatic reaction tank maintained at 25 °C. Next, 0.1 mol / L hydrochloric acid aqueous solution was added here to adjust the pH to 3.6. Further, 30 g of sodium chloride was added, diluted to 150 mL with pure water, and stirred for 10 minutes. Then, a pH electrode was set, and while stirring, 0.1 mol / L sodium hydroxide solution was added dropwise to adjust the pH to 4.0. Further, the sample adjusted to pH 4.0 was titrated with 0.1 mol / L sodium hydroxide solution, and the titration volume and pH value in the range of pH 8.7 - 9.3 were recorded at four or more points. Taking the titration volume of 0.1 mol / L sodium hydroxide solution as X and the pH value at that time as Y, a calibration curve was made.

[0054] Then, the consumption volume V (mL) of 0.1 mol / L sodium hydroxide solution required from pH 4.0 to 9.0 per 1.5 g of SiO₂ was determined from the formula V = (A × f × 100 × 1.5) / (W × C), and using this, the specific surface area was determined according to the formula SA = 29.0V - 28. In the above formula, A represents the titration volume (mL) of 0.1 mol / L sodium hydroxide solution required from pH 4.0 to 9.0 per 1.5 g of SiO₂, f represents the titer of 0.1 mol / L sodium hydroxide solution, C represents the SiO₂ concentration (%) of the sample, and W represents the sample collection amount (g). Regarding the measurement of the average particle diameter (NDc) of non-spherical silica fine particles in the non-spherical silica fine particle dispersion liquid and the measurement of the average particle diameter (SDc) of spherical silica fine particles in the spherical silica fine particle dispersion liquid, the measurement was also carried out according to the measurement of the average particle diameter (Dc) of the silica fine particle dispersion liquid for polishing.

[0055] 2. Measurement of the short axis / long axis ratio of the silica fine particles for polishing by the image analysis method In a photographic projection diagram or projected image obtained by photographing a silica fine particle dispersion for polishing at a magnification of 300,000 times (or 500,000 times) with a transmission electron microscope, for 100 randomly selected particles, for each particle, the major axis is the maximum diameter, its length is measured, and the value is defined as the major axis length (La). Also, a point that bisects the major axis on the major axis is determined, two points where a straight line perpendicular to it intersects the outer edge of the particle are obtained, the distance between the two points is measured and defined as the minor axis (Sh). In this way, the minor axis / major axis ratio (Sh / La) is obtained for each particle, and the average value of 100 of them is obtained and used as the minor axis / major axis ratio of the silica fine particles for polishing. In addition, regarding the minor axis / major axis ratio of the non-spherical silica fine particles in the non-spherical silica fine particle dispersion used as the raw material and the minor axis / major axis ratio of the spherical silica fine particles in the spherical silica fine particle dispersion, measurements were also carried out in accordance with the case of the silica fine particle dispersion for polishing.

[0056] 3. Measurement of Pore Volume Distribution and Average Pore Diameter 50 mL of a silica fine particle dispersion for polishing (silica concentration 40% by mass) was adjusted to pH 3.5 with HNO3, 40 mL of 1-propanol was added, the sample dried at 110 °C for 16 hours was placed in a desiccator and cooled to room temperature, and then pulverized in a mortar. Next, it was weighed into a cell, 1 g of the sample was taken separately, degassed under vacuum at 500 °C for 1 hour, and then set in a Microtrac [BELSORP-mini manufactured by BEL Japan, Inc.], N2 was adsorbed onto the sample, and the obtained adsorption isotherm was analyzed by the BJH method to obtain the pore volume distribution and the average pore diameter [nm]. (Calculation of Pore Distribution Width) In the obtained pore volume distribution, from the larger pore diameter side, the values of the cumulative 10% pore diameter (D 10 ) [nm], the cumulative 50% pore diameter (D 50 ) [nm], and the cumulative 90% pore diameter (D 90 ) [nm] were obtained, and the value of (D 90 - D 10 ) / D 50 was calculated.

[0057] 4. Measurement of Average Particle Diameter (NDi) of Non-spherical Silica Fine Particles Perform the same measurement as the measurement of the minor axis / major axis ratio by the image analysis method of the silica fine particles for polishing, measure the number of particles corresponding to non-spherical silica fine particles (minor axis / major axis ratio less than 0.9), and perform the measurement in another field of view until the number of these particles exceeds 100. Subsequently, for 100 particles identified as non-spherical silica fine particles, the value of the major axis length of each was determined, and the number average of 100 was determined to obtain the average particle diameter (NDi) of the non-spherical silica fine particles contained in the silica fine particle dispersion for polishing. Here, the major axis means the line segment with the longest length among the line segments connecting two points on the outer edge of the particle in the particle image or the like.

[0058] 5. Measurement of the average particle diameter (SDi) of spherical silica fine particles Perform the same measurement as the measurement of the minor axis / major axis ratio by the image analysis method of the silica fine particles for polishing, measure the number of particles corresponding to spherical silica fine particles (minor axis / major axis ratio 0.9 or more), and perform the measurement in another field of view until the number of these particles exceeds 100. Subsequently, for 100 particles identified as spherical silica fine particles, the value of the major axis length of each was determined, and the number average of 100 was determined to obtain the average particle diameter (SDi) of the spherical silica fine particles contained in the silica fine particle dispersion for polishing. Here, the major axis means the line segment with the longest length among the line segments connecting two points on the outer edge of the particle in the particle image or the like as described above. When the length of the line segment is uniform, the length is taken as the length of the major axis.

[0059] 6. Calculation of the ratio of the average particle diameter (SDi) of spherical silica fine particles to the average particle diameter (NDi) of non-spherical silica fine particles The value of SDi / NDi was obtained from the value of the average particle diameter (NDi) of the non-spherical silica fine particles contained in the silica fine particle dispersion for polishing obtained by the above method and the value of the average particle diameter (SDi) of the spherical silica fine particles.

[0060] 7. Number ratio of non-spherical silica fine particles in the silica fine particle dispersion for polishing In the measurement of the minor axis / major axis ratio of the silica fine particles for polishing by image analysis, the number ratio [% of particles] of non-spherical silica fine particles (minor axis / major axis ratio less than 0.9) in the silica fine particle dispersion for polishing was calculated from the value obtained by dividing the number of particles that became non-spherical silica fine particles by the total number of measured particles by 100.

[0061] 8. Measurement of the silica concentration of the silica-based particle dispersion Add 2 mL of 50% sulfuric acid aqueous solution to 10 g of a sample consisting of the silica fine particle dispersion for polishing, evaporate to dryness on a platinum dish, bake the obtained solid matter at 1000 °C for 1 hour, cool and weigh. Next, dissolve the weighed solid matter in a small amount of 50% sulfuric acid aqueous solution, add 20 mL of hydrofluoric acid, then evaporate to dryness on a platinum dish, bake at 1000 °C for 15 minutes, cool and weigh. From these weight differences, the content of the solid content is determined, and the solid content concentration with respect to the mass of the sample (10 g) can be calculated. Next, the concentration obtained by subtracting the alkali content calculated separately and converted to oxides (such as Na2O) was calculated as the silica content rate in the silica fine particle dispersion for polishing. In addition, the content rate of components other than silica that the silica fine particle dispersion may contain can be specified and quantified using, for example, an inductively coupled plasma optical emission spectrometer. For Ni, Cu, K, and Na, identification and quantification can be performed using an atomic absorption spectrophotometer.

[0062] 9. Measurement of the average particle diameter by dynamic light scattering method The average particle diameter measured by the dynamic light scattering method of the non-spherical silica fine particles in the non-spherical silica fine particle dispersion used as a raw material was measured by the dynamic light scattering method using a particle size distribution measuring device ("nanoSAQLA" manufactured by Otsuka Electronics Co., Ltd.) after preparing a 1 mass% non-spherical silica fine particle dispersion. As the dispersion medium, ammonia water with a concentration of 0.58 mass% was used.

[0063] 10. Polishing test of the polishing slurry As the substrate to be polished, an aluminum substrate coated with nickel plating for hard disks (nickel-plated substrate manufactured by Toyo Kohan Co., Ltd.) was prepared. This substrate to be polished was set in a polishing apparatus ("NF300" manufactured by Nanofactor Co., Ltd.), and using a polishing pad ("Veratrix NO178" manufactured by FILWEL), polishing was performed for 15 minutes while supplying a polishing slurry at a rate of 40 g / min at a substrate load of 0.05 MPa, a platen rotation speed of 50 rpm, and a head rotation speed of 50 rpm. (Calculation of polishing speed ratio) The polishing speed was determined from the weight difference of the polished substrate before and after polishing and the polishing time, and the relative value when Comparative Example 1 was set to 100 was calculated.

[0064] [Preparation Example 1] (Preparation of acidic silicic acid solution) Pure water was added to an aqueous sodium silicate solution (silica concentration 24.06 mass%, Na2O concentration 7.97 mass%) to obtain an aqueous sodium silicate solution (silica concentration 5 mass%). 18 kg of the obtained aqueous sodium silicate solution was passed through 6 L of a strongly acidic cation exchange resin (SK1BH, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h -1 to obtain 18 kg (silica concentration 4.5 mass%, pH 2.7). In the following Synthesis Examples, Examples, and Comparative Examples, this acidic silicic acid solution or an acidic silicic acid solution equivalent to this acidic silicic acid solution was appropriately concentrated or diluted and used as a raw material.

[0065] [Synthesis Example 1] (Synthesis of non-spherical silica fine particle dispersion (1)) 790 g of an aqueous sodium silicate solution (silica concentration 24.3 mass%) was added to 2,278 g of water and stirred until homogeneous. Subsequently, 78 g of an acidic silicic acid solution (silica concentration 4.5 mass%) and 61 g of an aqueous potassium chloride solution (concentration 20 mass%) were added and stirred until homogeneous to obtain a precursor dispersion (silica concentration 6.1 mass%). Subsequently, the obtained precursor dispersion was heated to 98°C and held at 98°C for 40 minutes. While holding at 98°C, 5,984 g of an acidic silicic acid solution (silica concentration 4.5 mass%) was added over 5 hours, and then 2,655 g of water was added and cooled to obtain a seed particle dispersion (1). 4,000 g of the obtained seed particle dispersion (1) was added to 5,900 g of water, and then the temperature was raised to 98°C. While maintaining the temperature at 98°C, 26,451 g of an acidic silica solution (silica concentration: 4.5% by mass) was added over 18 hours to obtain a non-spherical silica fine particle dispersion (1). For the obtained non-spherical silica fine particle dispersion (1), the average particle diameter (Dc) was measured by the specific surface area conversion method and found to be 65 nm. Also, the average particle diameter (DL) was measured by the dynamic light scattering method and found to be 155 nm.

[0066] [Synthesis Example 2] (Synthesis of non-spherical silica fine particle dispersion (2)) 790 g of an aqueous sodium silicate solution (silica concentration: 24.3% by mass) was added to 637 g of water and stirred until homogeneous. Subsequently, 80 g of an acidic silica solution (silica concentration: 4.5% by mass) and 61 g of an aqueous potassium chloride solution (concentration: 20% by mass) were added and stirred until homogeneous to obtain a precursor dispersion (silica concentration: 12.5% by mass). Subsequently, the obtained precursor dispersion was heated to 85°C and held at 85°C for 40 minutes. While maintaining the temperature at 85°C, 6,158 g of an acidic silica solution (silica concentration: 4.5% by mass) was added over 5 hours. Then, 2,230 g of water was added and cooled to obtain a seed particle dispersion (2). 4,000 g of the obtained seed particle dispersion (2) was added to 5,900 g of water, and then the temperature was raised to 98°C. While maintaining the temperature at 98°C, 26,441 g of an acidic silica solution (silica concentration: 4.5% by mass) was added over 18 hours to obtain a non-spherical silica fine particle dispersion (2). For the obtained non-spherical silica fine particle dispersion (2), the average particle diameter (Dc) was measured by the specific surface area conversion method and found to be 49 nm. Also, the average particle diameter (DL) was measured by the dynamic light scattering method and found to be 173 nm.

[0067] [Example 1] (Preparation of silica fine particle dispersion for polishing (1)) The non-spherical silica fine particle dispersion (1) obtained in Synthesis Example 1 and the spherical silica fine particle dispersion (Cataloid SI-30 manufactured by Nippon Shokubai Catalysts & Chemicals, Ltd., SiO2 concentration 30.5 mass%, average particle diameter (SDc) = 11 nm) were mixed at room temperature to obtain a silica fine particle dispersion (1) for polishing. When the silica fine particle dispersion (1) for polishing was dried under the conditions shown in Table 1, the dry weight ratio of the non-spherical silica fine particle dispersion (1) after mixing was 85 mass%, and the dry weight ratio of the spherical silica fine particle dispersion was 15 mass%. (Preparation of polishing slurry) 47.2 g (pH 10.5) of the obtained silica fine particle dispersion (1) for polishing was added to 255.2 g of water, and 124 g of hydrogen peroxide solution (concentration 5 mass%) and 62.5 g of phosphoric acid aqueous solution (concentration 10 mass%) were added to prepare a polishing slurry (1) with a SiO2 concentration of 4.5 mass% and a pH of 1.50.

[0068] And the production conditions of the silica fine particle dispersion for polishing and the polishing slurry are shown in Table 1. Also, the obtained silica fine particle dispersion for polishing and the polishing slurry were subjected to various evaluations by the above-described method. The obtained evaluation results are shown in Tables 1 and 2. Note that the production conditions and evaluation results for the following Examples and Comparative Examples are also shown in Tables 1 and 2.

[0069] [Example 2] (Preparation of silica fine particle dispersion (2) for polishing) The non-spherical silica fine particle dispersion (2) obtained in Synthesis Example 2 and the spherical silica fine particle dispersion (Cataloid SI-50 manufactured by Nippon Shokubai Catalysts & Chemicals, Ltd., SiO2 concentration 48.5 mass%, average particle diameter (SDc) 26 nm) were mixed at room temperature to obtain a silica fine particle dispersion (2) for polishing (pH 10.4). When the silica fine particle dispersion (2) for polishing was dried under the conditions shown in Table 1, the dry weight ratio of the non-spherical silica fine particle dispersion (2) after mixing was 95 mass%, and the dry weight ratio of the spherical silica fine particle dispersion was 5 mass%. (Preparation of polishing slurry (2)) 52.8 g of the obtained silica fine particle dispersion liquid for polishing (2) was added to 258.4 g of water, 124 g of hydrogen peroxide solution (concentration: 5% by mass) and 62.5 g of phosphoric acid aqueous solution (concentration: 10% by mass) were added, and a polishing slurry (2) with a SiO₂ concentration of 4.5% by mass and a pH of 1.50 was prepared.

[0070] [Comparative Example 1] 47.2 g (pH 10.7) of a non-spherical silica fine particle dispersion liquid similar to the non-spherical silica fine particle dispersion liquid (1) obtained in Synthesis Example 1 was added to 255.2 g of water, 124 g of hydrogen peroxide solution (concentration: 5% by mass) and 62.5 g of phosphoric acid aqueous solution (concentration: 10% by mass) were added, and a polishing slurry (R1) with a SiO₂ concentration of 4.5% by mass and a pH of 1.50 was prepared.

[0071]

Table 1

[0072]

Table 2

Claims

1. A silica fine particle dispersion liquid for polishing, which is composed of a silica fine particle dispersion liquid in which silica fine particles satisfying the following conditions 1) to 3) are dispersed in a solvent. 1) The average particle diameter [particle diameter in terms of specific surface area] (Dc) is in the range of 38 nm or more and 50 nm or less. 2) The value of the minor axis / major axis ratio [image analysis method] is in the range of 0.47 or more and 0.90 or less. 3) In the pore volume distribution during drying of the silica fine particles, the average pore diameter is in the range of 6.0 nm or more and 17.0 nm or less, and in the pore volume distribution, D １０ , D ５０ and D ９０ (the cumulative 10% pore diameter from the smaller pore diameter is D １０ , similarly the cumulative 50% pore diameter is D ５０ , and similarly the cumulative 90% pore diameter is D ９０ ), the value of (D ９０ - D １０ ) / D ５０ is 2.3 or more.

2. The silica fine particle dispersion liquid for polishing according to claim 1, wherein the proportion of the number of non-spherical silica fine particles having a minor axis / major axis ratio [image analysis method] value of less than 0.9 in the silica fine particle dispersion liquid for polishing is in the range of 7% by number or more and 50% by number or less.

3. The silica fine particle dispersion liquid for polishing according to claim 1 or claim 2, wherein the average particle diameter [image analysis method] (NDi) of non-spherical silica fine particles having a minor axis / major axis ratio [image analysis method] value of less than 0.9 and the average particle diameter [image analysis method] (SDi) of spherical silica fine particles having a minor axis / major axis ratio [image analysis method] value of 0.9 or more in the silica fine particle dispersion liquid for polishing satisfy the condition represented by the following formula (F1). 0.1 ≦ SDi / NDi ≦ 0.6... (F1)

4. A polishing slurry containing the silica fine particle dispersion liquid for polishing according to claim 1 or claim 2, hydrogen peroxide, and an inorganic acid.

5. A method for producing the silica fine particle dispersion liquid for polishing according to claim 1 or claim 2, a non-spherical silica fine particle dispersion liquid containing non-spherical silica fine particles having a minor axis / major axis ratio [image analysis method] value of less than 0.9 and having an average particle diameter [NDc] of the silica fine particles in the range of 45 nm or more and 360 nm or less, and a spherical silica fine particle dispersion liquid containing spherical silica fine particles having a minor axis / major axis ratio [image analysis method] value of 0.9 or more and having an average particle diameter [SDc] of the silica fine particles in the range of 10 nm or more and 45 nm or less are mixed so as to satisfy the following conditions A) and B). A method for producing a silica fine particle dispersion liquid for polishing. A) The value of the ratio [SDc / NDc] of the average particle diameter [SDc] of the silica fine particles in the spherical silica fine particle dispersion liquid to the average particle diameter [NDc] of the silica fine particles in the non-spherical silica fine particle dispersion liquid is in the range of 0.05 or more and 0.80 or less. B) The proportion (mass%) [in terms of silica content] of the non-spherical silica fine particle dispersion liquid with respect to the entire silica fine particle dispersion liquid for polishing is in the range of 75% by mass or more and 98% by mass or less.

Images