JP5860587B2 - Polishing silica sol, polishing composition, and method for producing polishing silica sol - Google Patents

Description

  The present invention relates to a polishing silica sol suitable for polishing glass hard disks, semiconductor wafers, alumina hard disks, and the like, a polishing composition, and a method for producing a polishing silica sol.

  In a semiconductor device such as a semiconductor substrate or a wiring substrate, an alumina hard disk, a glass hard disk, or an optical material, these surface states affect semiconductor characteristics or optical characteristics. For this reason, it is required that the surfaces and end faces of these parts be polished with extremely high accuracy. Conventionally, as a method for polishing such a member, for example, after performing a relatively rough primary polishing process, a precise secondary polishing process is performed to obtain a highly accurate surface with few scratches such as line marks. The way to get has been taken.

  A polishing composition containing silica sol is used for finish polishing such as this secondary polishing. For example, Patent Document 1 describes an example in which a silicon dioxide film is polished using an abrasive in which true spherical colloidal silica having an average particle diameter of 10 to 100 nm is dispersed. Patent Document 2 describes that colloidal silica having a special shape having a major axis of 7 to 1000 nm (minor axis / major axis) = 0.3 to 0.7 is suitable for semiconductor wafer polishing. Patent Document 3 describes plate-like aluminum oxide particles that exhibit excellent performance as abrasive particles. However, this type of known plate-like aluminum oxide particles has a large particle size of submicron and is suitable for rough polishing applications, but is not suitable for precision polishing such as finish polishing.

On the other hand, cerium oxide particles are known as an abrasive for polishing treatment that requires a high polishing rate such as primary polishing, and as an abrasive for secondary finish polishing. For example, Patent Document 4 discloses an example of polishing an SiO ₂ insulating film using an aqueous dispersion of cerium oxide particles. The cerium oxide particles have a lower hardness than the above silica-based and alumina-based abrasive particles, but exhibit excellent polishing speed and finish polishing characteristics. That is, unlike conventional abrasive particles, by utilizing its chemical properties, it exhibits an excellent polishing rate and finish polishability that cannot be obtained with other abrasives. However, on the other hand, it is difficult to control the particle size and particle size distribution, and it relies on imports and the number of producing countries is limited.

  It is also known to use other abrasive particles mixed with a cerium oxide-based abrasive. For example, Patent Document 5 discloses an example in which cerium oxide particles and colloidal silica particles are mixed and used. In this case, although an intermediate characteristic between cerium oxide particles and colloidal silica can be obtained, the above problem has not been essentially solved. Further, when two or more kinds of abrasive particles are mixed to obtain a polishing composition (slurry), the dispersibility and sedimentation properties of the particles in the medium are different, and thus the stability as a slurry tends to be lowered. In order to increase the polishing power using a mixture of silica and cerium oxide particles, it is effective to use particles having a large particle diameter. In this case, while a high rate of polishing power can be obtained, many scratches are generated, and it is difficult to finish the surface precisely. Further, since the abrasive particles are large, the settling rate due to the elapsed time of the abrasive particles is high, and the concentration gradient of the abrasive particles in the polishing liquid is likely to occur. Therefore, it is necessary to perform mixing and stirring before polishing, and there is a problem that storage stability as a polishing liquid is poor.

JP-A-8-267356 Japanese Patent Laid-Open No. 7-221059 Japanese Patent Laid-Open No. 1-109082 JP-A-9-270402 JP-A-9-132770

  As discussed above, there is a need for silica-based abrasives that can replace ceria, which is widely used as an abrasive for glass substrates, etc. There was a limit.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a polishing silica sol having a high polishing rate and suitable for precision polishing, a polishing composition, and a method for producing a polishing silica sol. .

The polishing silica sol according to the present invention is obtained by dispersing non-spherical silica fine particles having an average particle diameter in the range of 5 to 300 nm measured by a dynamic light scattering method in a dispersion medium, and a solid content concentration of 10 to 60 mass. % Silica sol,
²⁹ The chemical shift at the time of Si-NMR spectrum measurement The area of Q4 in the peak area of −73 to −120 ppm is 88% or more and 91% or less, the area of Q3 is 8% or more and 11% or less ,
When the average particle diameter of the non-spherical silica fine particles measured by the dynamic light scattering method is [A] and the average particle diameter [B] measured by the nitrogen adsorption method is A / B value of the non-spherical silica fine particles. Is in the range of 2.0 to 5.0 .
However, the chemical shift uses tetramethylsilane as a reference substance, Q4 is a peak in the range of −100 to −120 ppm, and Q3 is a peak in the range of −82 to −100 ppm.

The polishing silica sol may have the following characteristics.
(A ) The polishing silica sol having the following characteristics.
1) The value of the molar ratio defined by SiO ₂ / MOH (M is Na, K or quaternary amine) of the silica sol is 100 to 420,
2) The silica sol has a molar ratio of 400 to 1000 defined by SiO ₂ / X (X is SO ₄ ²⁻ , Cl ⁻ , NO ₃ ⁻ or PO ₄ ³⁻ ).
( B ) The absolute value of the surface charge density of the non-spherical silica fine particles is in the range of 0.3 to 1.3 [μeq / m ² ].

  Further, the polishing composition according to another invention is one kind selected from the above-described polishing silica sol and an additive group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster and a pH buffer. It contains the above additive, It is characterized by the above-mentioned.

Next, the method for producing a polishing silica sol of the present invention comprises mixing an alkali silicate and an inorganic acid, adjusting the pH of the mixed solution to a range of 3 to 7, and adjusting a solution containing silica hydrogel;
Washing and removing the salt contained in the solution obtained in this step;
The solution obtained by adding an alkali solution to the silica hydrogel after the salt has been removed is stirred while maintaining the temperature range of 60 to 100 ° C., and the silica hydrogel is peptized to contain non-spherical silica fine particles. Obtaining a silica sol;
Holding the solution containing the silica sol obtained in this step in a temperature range of 130 to 300 ° C. and a pressure range of 0.13 to 0.30 MPa to perform a first hydrothermal treatment to grow non-spherical silica fine particles; ,
An alkali species and an anion species are added to a silica sol containing non-spherical silica fine particles grown by the first hydrothermal treatment, and maintained at a temperature range of 130 to 300 ° C. and a pressure range of 0.13 to 0.30 MPa. to perform a second hydrothermal treatment, viewed contains a step to advance the condensation of silanol groups in the silica particles, and
The addition amount of alkali species and anion species in the second hydrothermal treatment step satisfies the following conditions 1) and 2) .
1) The alkali species is selected from the group of alkali species consisting of NaOH, KOH and quaternary amine, and the molar ratio of alkali species to silica in the silica sol is SiO ₂ / MOH (M is Na, K or quaternary amine). ), The molar ratio value is 100 to 420,
2) The anionic species is selected from the group of anionic species consisting of SO ₄ ²⁻ , Cl ⁻ , NO ₃ ⁻ or PO ₄ ^3−, and the molar ratio of the anionic species to silica in the silica sol is SiO ₂ / X ( When X is represented by SO ₄ ²⁻ , Cl ⁻ , NO ₃ ⁻ or PO ₄ ³⁻ ), the molar ratio value is 400 to 1000.

The method for producing the silica sol may have the following characteristics.
(D) The first hydrothermal treatment is performed at a silica fine particle concentration of 2 to 5% by weight in the silica sol, and the second hydrothermal treatment is performed at a silica fine particle concentration of 10 to 20% by weight in the silica sol. % To be done .

  According to the present invention, by increasing the siloxane bond of silicon atoms in non-spherical silica fine particles and improving the density and denseness of the silica fine particles, it is suitable for precision polishing and has a high polishing rate. A silica sol can be obtained.

[Non-spherical silica fine particles]
The silica sol of the present invention contains silica fine particles. The silica fine particles can be obtained, for example, by peptizing and heating silica hydrogel (gel silicic acid) obtained by neutralizing an alkali silicate such as sodium silicate with an acid. Silica hydrogel does not necessarily contain SiO ₂ , and for example, various types of silicic acid such as those in which Si (OH) ₂ are bonded together by hydrogen bonds are included. The silica fine particles mainly contain siloxane bonds (Si—O—Si) in which two silicon atoms are connected via oxygen atoms, and silicon atoms partially bonded to hydroxyl groups.

When attention is focused on silicon having a siloxane bond and a hydroxyl group, the silica fine particles are composed of a monomer (Si (OH) ₄ ) (hereinafter referred to as Q0 structure) bonded to four hydroxyl groups, an oligomer containing one siloxane bond and three hydroxyl groups. (Si—O—Si (OH) ₃ ) (hereinafter referred to as Q1 structure) Oligomer ((Si—O) ₂ —Si (OH) ₂ ) (hereinafter referred to as Q2 structure) including two siloxane bonds and two hydroxyl groups ) Oligomer containing three siloxane bonds and one hydroxyl group ((Si—O) ₃ —Si—OH) (hereinafter referred to as Q3 structure), and oligomer containing four siloxane bonds (Si— (O—Si) ₄ (Hereinafter referred to as Q4 structure).

When the portion containing each of the above-described Q0 to Q4 structures contained in the silica fine particles is referred to as a siloxane structure part, as the content ratio of the Q4 structure or the Q3 structure in the siloxane structure part increases, the bonds between silicon increase. Silica fine particles having a high density and high density and exhibiting an excellent polishing rate can be obtained. Here, although the siloxane bond is not included in the Q0 structure, in the present specification, the monomer having the Q0 structure is also included in the siloxane structure portion for the convenience of explanation in evaluating the polishing performance of silicon fine particles.
The present invention was made based on such a concept, and the content ratio of the Q4 structure contained in the siloxane structure part is 88 mol% or more of silicon in the siloxane structure part, and the inclusion of the Q3 structure The ratio is 11 mol% or less, and the total content of the Q0 to Q2 structures is the balance.

The abundance ratio of silicon having a Q0 to Q4 structure can be determined by ²⁹ Si-NMR (nuclear magnetic resonance). ^When silica sol containing silica fine particles of the present invention is prepared with silicon containing ²⁹ Si and ²⁹ Si-NMR analysis is performed using, for example, tetramethylsilane as a reference substance, the chemical shift of the Q0 to Q2 structure is −73. Appears in the range of 0.0 to -120.0 ppm. Specifically, the chemical shift of the Q0 structure is in the region of −73.0 to −73.5 ppm, the chemical shift of the Q1 structure is in the region of −73.5 to −78.0 ppm, and the chemical shift of the Q2 structure is −78.0. In the region of -82.0 ppm, the chemical shift of the Q3 structure appears in the region of -82.0 to -100.0 ppm, and the chemical shift of the Q4 structure appears in the region of -100.0 to -120.0 ppm.

  Since the area of the chemical shift appearing in each region corresponds to the number of moles of silicon having a Q0 to Q4 structure contained in the siloxane structure, the Q4 with respect to the peak area having a chemical shift in the range of -73.0-120.0 ppm. The peak area ratio of the chemical shift of the Q3 structure represents the molar ratio of silicon having the Q4 and Q3 structures contained in the siloxane structure. Therefore, it can be said that silicon fine particles having a high ratio of the chemical shift peak area ratio of the Q4 and Q3 structures have a high density and an excellent polishing rate.

From this point of view, the silicon fine particles of the present invention have a chemical shift in the spectrum obtained by conducting ²⁹ Si-NMR analysis of silica sol containing tetramethylsilane as a reference substance and containing the silicon particles. The area of Q4 with respect to the peak area in the range is 88% or more and the area of Q3 is 11% or less. In other words, the content ratio of the total silicon having the Q3 and Q4 structures is in the range of 88 to 100 mol% of the entire Q0 to Q4 structure, while the content ratio of Q3 alone does not exceed 11 mol%. It has become.

  When the content ratio of silicon having a Q4 structure is less than 88 mol%, the density and denseness of the silica fine particles cannot be sufficiently improved, and the polishing rate becomes low. On the other hand, when the content ratio of silicon having the Q4 structure is 88 mol%, it is difficult to set the content ratio of silicon having the Q3 structure to 11 mol% or more.

  Further, the content ratio of silicon having the Q0 to Q2 structure is the remainder of silicon having the Q3 and Q4 structures, and there is no particular limitation. However, the smaller the number of siloxane bonds, the lower the density of the siloxane structure portion and the lower the density, so it is better to have, for example, as few Q0 and Q1 structures as possible. In this respect, silicon having Q0 and Q1 structures is suppressed to, for example, 0 to 1 mo1% of the whole silicon having Q0 to Q4 structures (chemical shifts of Q0 and Q1 with respect to peak areas in the range of −73.0 to −120.0 ppm). It is preferable that the peak area ratio is 0 to 1%) and the balance is Q2.

The polishing silica sol of the present invention contains more siloxane structures having such characteristics.
The concentration of the silica fine particles contained in the polishing silica sol is preferably in the range of 10 to 60% by mass, more preferably in the range of 20 to 50% by mass. When the concentration of silica fine particles is less than 10% by mass, the polishing rate is low and the productivity is poor. When it is larger than 60% by mass, the polishing rate is high, but the polishing liquid dries at the time of polishing, and there is a tendency that agglomerated particles are mixed and the generation of scratches increases.

  The particle diameter of the non-spherical silica fine particles is preferably in the range of 5 to 300 nm, more preferably in the range of 10 to 250 nm when the fine particles of silica in the silica sol are measured by a dynamic light scattering method. . If this average particle size is smaller than 5 nm, the scratch is good, but the polishing rate is remarkably lowered and the productivity is also deteriorated. When the average particle size is larger than 300 nm, the polishing rate is good, but the generation of scratches increases.

  When the average diameter of the non-spherical silica fine particles by dynamic light scattering method is [A] and the average particle diameter measured by nitrogen adsorption method is [B], the value of “A / B” is 2.0 to 2.0. A range of 5.0 is preferred. The dynamic light scattering method is a method of measuring a dynamic equivalent diameter based on the diffusion coefficient of non-spherical silica fine particles in silica sol. On the other hand, in the nitrogen adsorption method, the surface area of the non-spherical silica fine particles is obtained by using, for example, the BET equation based on the result of measuring the amount of nitrogen gas adsorbed on the surface of the non-spherical silica fine particles, and this surface area is supported. This is a method for calculating the equivalent diameter of a sphere.

  Therefore, the value of “A / B” indicates the ratio of the dynamic equivalent diameter to the equivalent diameter of the non-spherical silica fine particles based on the surface area. As shown in the examples described later, the value of A / B is When it is in the range of 2.0 to 5.0, it is understood that the silica sol containing the non-spherical silica fine particles can exhibit good polishing performance. The reason why good polishing performance can be obtained when the value of A / B is within this range is not necessarily clear, but in the case of “A / B = 1”, the silica fine particles are close to the true sphere, and unevenness suitable for polishing. This is considered to be because the friction coefficient is reduced and the polishing effect is reduced. On the other hand, if the value of A / B becomes too large, the silica particles become too distorted from the spherical shape, resulting in an irregular shape, the strength of the particles themselves is weak during polishing, and they are easily destroyed. There is also a possibility that sufficient polishing performance cannot be exhibited. From this point of view, it can be inferred that the non-spherical silica particles having an A / B value in the range of 2.0 to 5.0 may have irregularities suitable for polishing.

  The dispersion medium for dispersing the non-spherical silica fine particles having the characteristics described above is not limited in terms of properties and types as long as it has the ability to disperse the silica fine particles and can be subjected to polishing treatment. For example, water, soluble organic alcohol, glycol and the like can be mentioned.

  The dispersion medium containing the above-mentioned non-spherical silica fine particles and forming a silica sol may contain substances originating from alkali species or anionic species added during the production of the silica sol. Examples of the alkali species added during the production of silica sol include NaOH, KOH, and quaternary amine. Specific examples of the quaternary amine include tetramethylammonium hydroxide (hereinafter referred to as TMAH). When the alkali species added to the silica sol raw material is contained in the silica sol of the product, there is an effect that the pH is high and the stability is high.

The content of these alkali species in the silica sol is calculated by converting the silicon in the silica sol to SiO ₂ in terms of mole, and converting the alkali species into the hydroxide hydroxide MOH (M is Na, K or a quaternary amine). When converted to mole, the molar ratio represented by SiO ₂ / MOH is preferably in the range of 100 to 420. When SiO ₂ / MOH is less than 100, there is a problem that the pH becomes high and the dissolution of silica particles becomes large and becomes unstable, and when it exceeds 420, the pH decreases and the long-term stability is impaired. There is a risk.

Examples of the anionic species added during the production of silica sol include SO ₄ ²⁻ , Cl ⁻ , NO ₃ ⁻ or PO ₄ ³⁻ . When the anionic species added to the silica sol raw material is contained in the silica sol of the product, the viscosity of the silica dispersion is lowered, and there is an effect that clogging of the polishing cloth and the like can be reduced.

The content of these anionic species in the silica sol is such that when the silicon in the silica sol is converted into SiO ₂ by mole and the number of moles of the anionic species is represented by X, the molar ratio represented by SiO ₂ / X is It is preferable to be in the range of 400-1000. When SiO ₂ / X is less than 400, the pH is lowered. There is a problem that it becomes unstable. If it exceeds 1000, the viscosity increases, the moving speed of the silica particles decreases, and the polishing efficiency may decrease.

However, the silica sol according to the present embodiment is not limited to the case where the dispersion medium contains various alkali species and anion species and the non-spherical silica fine particles are grown, and the non-spherical silica fine particles are grown. Those obtained by subjecting the silica fine particles to solid-liquid separation from the solution thus prepared and dispersing them in another dispersion medium are also included in the technical scope of the present invention.
The surface charge density of the non-spherical silica fine particles in the silica sol is preferably in the range of 0.3 to 1.3 [μeq / m ² ] as an absolute value. When the absolute value of the surface charge density is smaller than 0.3 [μeq / m ² ], the non-spherical silica fine particles may be aggregated. On the other hand, in the particle size range of 5 to 300 nm, the absolute value of the surface charge density is set to 1. It is difficult to make it larger than 3 [μeq / m ² ].

[Polishing composition]
The silica sol containing the above-mentioned non-spherical silica fine particles is polished by adding one or more additives selected from the group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster and a pH buffer. It may be a composition for use.

  As examples of polishing accelerators, other examples of polishing accelerators include acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and hydrofluoric acid, or sodium salts, potassium salts, ammonium salts, and mixtures thereof. And so on. In the case of a polishing composition containing these polishing accelerators, when polishing a material to be polished consisting of composite components, the polishing rate is accelerated for a specific component of the material to be polished, thereby finally achieving flat polishing. You can get a plane.

  Surfactants play a role in improving the dispersibility and stability of the polishing composition, and include cationic systems such as aliphatic amine salts and aliphatic quaternary ammonium salts, anionic systems such as carboxylates and sulfonates, Nonionic surfactants such as oxyethylene alkyl and glycerol ester polyoxyethylene ether, amphoteric surfactants such as carboxybetaine type and sulfobetaine type can be added. Any of the surfactants has an action of reducing the contact angle with the surface to be polished, and has an action of promoting uniform polishing. Moreover, you may add hydrophilic compounds, such as glycerol ester and sorbitan ester, as an additive which show | plays the effect similar to surfactant.

  The heterocyclic compound is added for the purpose of suppressing the erosion of the substrate to be polished by forming a passive layer or a dissolution inhibiting layer on the metal when the substrate to be polished contains a metal. A “heterocyclic compound” is a compound having a heterocyclic ring containing one or more heteroatoms. A hetero atom means an atom other than a carbon atom or a hydrogen atom. A heterocycle means a cyclic compound having at least one heteroatom. A heteroatom means only those atoms that form part of a heterocyclic ring system, either external to the ring system, separated from the ring system by at least one non-conjugated single bond, Atoms that are part of a further substituent of are not meant. Preferred examples of the hetero atom include, but are not limited to, a nitrogen atom, a sulfur atom, an oxygen atom, a selenium atom, a tellurium atom, a phosphorus atom, a silicon atom, and a boron atom. Examples of the heterocyclic compound include imidazole and benzotriazole.

  The pH adjuster is an acid or salt added as necessary to adjust the pH of the polishing composition for the purpose of enhancing the effect of adding the various additives described above. As a pH adjuster for adjusting the polishing composition to pH 7 or more, alkaline sodium hydroxide, aqueous ammonia, or the like is used. When adjusting the pH to less than 7, acids such as lactic acid and citric acid are used. .

  The pH buffer serves to keep the pH value of the polishing composition constant, and for example, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and the like can be used.

[Production method]
An example of a method for producing a silica sol having the characteristics described above will be described.
First, an alkali silicate salt, which is a raw material for silica fine particles, is dissolved in an aqueous solution. The concentration of the alkali silicate aqueous solution is preferably adjusted to 1 to 10% by weight, more preferably 2 to 8% by weight in terms of SiO ₂ . When the content of silicon as SiO ₂ is less than 1% by weight, the polymerization (gelation) of silicic acid is insufficient, and the silica outflow from the filter cloth is large at the time of salt washing such as sodium sulfate. There is a problem that the yield of ₂ is low. On the other hand, if this concentration exceeds 10% by weight as SiO ₂ , the aqueous solution cannot be neutralized uniformly, and the silicic acid polymerization becomes non-uniform, resulting in variations in the size of the non-spherical silica fine particles finally obtained. Increase.

  Silica hydrogel is obtained by neutralizing silicic acid by adding inorganic acid (mineral acid) such as hydrochloric acid, sulfuric acid, nitric acid, etc. so that the pH is in the range of 3-7 to the prepared silicate aqueous solution. A solution containing is obtained. In order to obtain a uniform hydrogel, the pH of the solution after neutralization is preferably in the range of 3-7. When the pH of the solution after neutralization is less than 3, the hydrogel structure does not sufficiently develop, and silica is easily eluted from the filter cloth during washing. On the other hand, when the pH of the solution exceeds 7, a part of siloxane bond occurs in the hydrogel, and the silica gel is peptized into silica fine particles having the target particle size during the subsequent treatment for peptizing the hydrogel. There is a drawback that it is difficult to do.

  Thus, after neutralizing the aqueous solution of an alkali silicate salt with an acid to obtain a silica hydrogel, it is preferably allowed to stand at a temperature range of 15 to 35 ° C. for about 10 hours for aging. Regarding the aging time, a range of 10 minutes to 3 hours is usually recommended.

The aged silica hydrogel is washed with pure water or ammonia water to remove salts generated by neutralization. The silica hydrogel is washed by supplying a solution containing the silica hydrogel to a filter such as an Oliver filter, and then continuously supplying the washing liquid. For example, when sodium silicate is used as the alkali silicate salt and neutralization is performed using sulfuric acid, sodium sulfate is generated. In this case, the concentration of sodium sulfate after washing is desirably 0.05% by weight or less with respect to the solid content as SiO ₂ contained in the silica hydrogel. When the content of sodium sulfate is within this range, the time required for peptization is short and the influence on productivity is small. On the other hand, when the concentration of sodium sulfate is increased, the negative potential of the sol particles is decreased, the peptization is insufficient, and the aggregate remains and a stable sol solution cannot be obtained. Here, even if the silica hydrogel contains other types of salts, the salt content in the silica hydrogel after washing is based on the solid content as SiO ₂ for the same reason as in the case of sodium sulfate. It is preferably 0.05% by weight or less.

  An alkali solution is added to the silica hydrogel that has been washed, and the silica hydrogel is peptized to obtain a silica sol. As an example of a specific operation procedure, by adding water to a silica hydrogel and stirring with a stirrer, a slurry-like silica hydrogel dispersion is prepared, and an appropriate amount of alkali is added thereto and stirred. Silica hydrogel peptization takes place.

  As the alkali added to the dispersion, alkali metal hydroxides such as KOH and NaOH, ammonium hydroxide, and an aqueous amine solution can be used. The amount of alkali added is adjusted so that the pH of the silica hydrogel dispersion after alkali addition is in the range of 5-11. When the pH is less than 5, the dispersion becomes highly viscous, and it becomes difficult to obtain a stable silica sol. When the pH exceeds 11, the silica is easily dissolved and the target particle diameter cannot be maintained, and partially agglomerated particles are likely to be obtained, which is likely to be unstable particularly in a high concentration region.

  The temperature at which the silica hydrogel is peptized with an alkali is preferably in the range of 60 to 100 ° C, and more preferably in the range of 70 to 95 ° C. When the temperature is less than 60 ° C., sufficiently uniform peptization may not be possible. When the temperature exceeds 100 ° C., the shape of the silica fine particles obtained tends to be spherical. After the alkali is added to the silica hydrogel, the silica hydrogel is peptized by stirring in the temperature range of 60 to 100 ° C., usually for about 10 minutes to 3 hours.

The concentration of the dispersion liquid of the silica hydrogel in performing peptization, the content of SiO ₂ is preferably 0.5 to 10 wt%, more preferably recommended range of 3 to 7 wt% with respect to the dispersion. When this concentration is less than 0.5% by weight, the proportion of silica dissolved in the dispersion increases, and the average particle size of the silica fine particles obtained decreases, so that during the particle growth performed in the next step The grain growth rate tends to be significantly slower. On the other hand, if this concentration exceeds 10% by weight as SiO ₂ , the average particle diameter of silica fine particles obtained by peptization tends to be non-uniform.

  When the silica hydrogel is peptized in this way to obtain a silica sol containing silica fine particles, the silica sol is grown in the temperature range of 130 to 300 ° C., more preferably 150 to 200 ° C. for the purpose of growing and stabilizing the silica fine particles. In the temperature range of 0.13 to 0.30 MPa (gauge pressure), more preferably in the pressure range of 0.15 to 0.20 MPa for 10 minutes to 6 hours, and the first hydrothermal treatment (first Hydrothermal treatment is performed. As a result, the silica in the dispersion grows by dissolving the small particles due to the difference in dissolution rate, growing on the large particles (Ostwald ripening), or silanol groups (—Si—OH) existing inside the particles. ) Grows non-spherical silica fine particles. The concentration of the silica fine particles in the silica sol at the start of the first hydrothermal treatment is preferably within the range of 2 to 5% by weight of the dispersion in consideration of the ease of transport of the slurry liquid.

  When the average particle diameter of the non-spherical silica fine particles measured by the dynamic light scattering method reaches a desired value in the range of 5 to 300 nm, the hydrothermal treatment is finished. The resulting silica sol is washed by filtering the silica sol with an ultrafiltration membrane while adding a new dispersion medium such as water, and then the supply of the dispersion medium is stopped and the filtration is continued. The concentration of the non-spherical silica fine particles is adjusted to, for example, 10 to 16% by mass within the range of 10 to 20% by weight. The timing at which the silica fine particles have a desired average particle diameter can be specified by grasping the relationship between the treatment time and the particle diameter in advance using the temperature and pressure of hydrothermal treatment as parameters.

  The silica sol obtained by finishing the first hydrothermal treatment contains non-spherical silica fine particles having a desired average particle diameter, and the silica fine particles contain impurities such as Na and K. In addition, the content ratio of the Q4 structure and the Q3 structure in the siloxane structure is small. Therefore, in this embodiment, the silica sol after the growth of the non-spherical silica fine particles is subjected to the second hydrothermal treatment (second hydrothermal treatment) to remove impurities from the silica fine particles and develop siloxane bonds. To increase the content ratio of the Q4 structure and the Q3 structure.

  In the second hydrothermal treatment, non-spherical silica fine particles are grown in the first hydrothermal treatment, washed, and subjected to concentration adjustment to the silica sol prepared to a concentration of 10 to 16% by weight. Add. In the second hydrothermal treatment, the alkali species develops a siloxane bond in the silica fine particles and plays a role of increasing the ratio of the Q4 structure or the Q3 structure in the siloxane structure. The anion also forms a salt with a cation such as Na, thins the hydrated layer on the surface of the silica fine particles, accelerates the growth rate of the silica particles during the second hydrothermal treatment, Plays the role of keeping it spherical.

  The alkali species added to the silica sol in the second hydrothermal treatment is selected from the alkali species group consisting of NaOH, KOH, quaternary amines and the like. Specific examples of the quaternary amine include tetramethylammonium hydroxide (hereinafter referred to as TMAH).

The amount of the alkali species added during the second hydrothermal treatment is as follows: silicon in the silica sol is converted into SiO ₂ in terms of mole, and the alkali species is converted to its cation oxide MOH (M is Na, K or second). When converted to a quaternary amine), the molar ratio represented by SiO ₂ / MOH is preferably in the range of 100 to 420. When SiO ₂ / MOH is less than 100, the solubility of silica in the solvent is increased, and the amount of the silica dissolved during the concentration using an ultrafiltration membrane or the like flows out into the filtrate to increase the yield. Becomes worse. In addition, the silica particles in the silica particles do not develop and the amount of low-molecular silica increases, and the number of silica particles is large at a constant volume during concentration, which not only increases the viscosity, but also increases the frequency of particle collision and agglomerates. There is a fear. On the other hand, if SiO ₂ / MOH exceeds 420, the pH of the dispersion medium becomes too low, and SiO ₂ is generated, which inhibits the development of siloxane bonds.

On the other hand, the anionic species added to the silica sol in the second hydrothermal treatment is selected from the group of anionic species consisting of SO ₄ ²⁻ , Cl ⁻ , NO ₃ ⁻ or PO ₄ ³⁻ . The amount of the anionic species added to the silica sol is such that when the silicon in the silica sol is converted into SiO ₂ by mole and the number of moles of the anionic species is represented by X, the molar ratio represented by SiO ₂ / X is 400 to 1000. It is preferable that it exists in the range. When SiO ₂ / X is less than 400, the silica sol has a low pH and a low zeta potential, so that the silica fine particles tend to aggregate during the hydrothermal treatment. On the other hand, when SiO ₂ / X exceeds 1000, the silica solubility increases and the average particle size of the silica fine particles decreases, or the viscosity of the silica sol increases and a stable silica sol cannot be obtained. . Anions are added by, for example, adding a solution in which an acid or salt containing these anions is dissolved.

  The silica sol to which a predetermined amount of alkali species and anionic species are added is, for example, a temperature range of 130 to 300 ° C., more preferably a temperature range of 150 to 200 ° C., and a pressure range of 0.13 to 0.30 MPa (gauge pressure). More preferably, the second hydrothermal treatment is performed by heating in the pressure range of 0.15 to 0.20 MPa for 0.5 to 10 hours. As a result, the impurities contained in the silica particles are eluted in the dispersion medium, the condensation reaction between silanol groups proceeds, the siloxane bond is developed, and the content ratio of the Q3 structure and Q4 structure of the siloxane structure portion increases. To do. As a result, it is possible to obtain silica fine particles having a high density and high density and suitable for polishing.

The timing of finishing the second hydrothermal treatment can be determined by grasping in advance the relationship between the treatment time and the content ratio of the Q3 structure and Q4 structure in the siloxane structure part, using the temperature and pressure of the hydrothermal treatment as parameters.
Further, the concentration of the silica fine particles in the silica sol at the start of the second hydrothermal treatment is preferably performed within a range of 10 to 20% by weight of the dispersion. When the concentration of the silica fine particles is less than 10% by weight, the amount of the silica fine particles re-dissolved in the dispersion medium to which the alkali species is added increases, resulting in a poor yield. On the other hand, when the concentration of the silica fine particles exceeds 20% by weight, the amount of scale attached to the processing container increases and not only the yield of the silica particles deteriorates but also the aggregation of the silica fine particles proceeds.

  When the second hydrothermal treatment is completed as described above, the silica sol is concentrated to, for example, 30 to 32% by mass within a range of 10 to 60% by mass using a rotary evaporator or the like. A silica sol according to the morphology is obtained. Further, it is a matter of course that the silica sol prepared by solid-liquid separation of the silica sol after the second hydrothermal treatment and dispersing the obtained solid content in another dispersion medium is also included in the technical scope of the present invention. It is.

  The silica sol according to the present embodiment has the following effects. By increasing the siloxane bond of the silicon atom in the non-spherical silica fine particles and improving the density and denseness of the silica fine particles, it is possible to obtain a polishing silica sol suitable for precision polishing and having a high polishing rate. . Since the polishing silica sol has a high polishing rate, it can be used as an alternative polishing material for ceria which has been used for polishing conventional glass substrates, particularly glass hard disks. The polishing silica sol and polishing composition can be suitably used for polishing applications such as glass hard disks and semiconductor wafers.

The second hydrothermal treatment may be performed on a silica sol containing commercially available non-spherical silica fine particles, for example. In this case, a predetermined amount of the above-mentioned alkali species or anionic species is added to the commercially available silica sol, and a second hydrothermal treatment is performed to condense the silanol groups contained in the siloxane structure in the silica fine particles. Thus, the non-spherical silica fine particles can be modified into properties suitable for polishing. By performing such modification, the area of the Q4 structure portion is 88% or more and the area of the Q3 structure portion is 11% at the peak area of chemical shift of −73.0 to −120.0 ppm at the time of ²⁹ Si-NMR spectrum measurement. Of course, the following silica sol containing silica fine particles is also included in the technical scope of the present invention.

[Evaluation method]
The evaluation method of the polishing silica sol in each example is described below.
[1] ²⁹ Si-NMR
The silica sol for polishing according to each example is put in a dedicated glass cell, 5% by weight of tetramethylsilane is added as a reference material, and NMR apparatus (JNM-EX270 type, analysis software; manufactured by JEOL Ltd .; manufactured by JEOL Ltd.) Excalibur), a ²⁹ Si-NMR spectrum was obtained by a single pulse non-decoupling method. The resulting total area _{S T} peaks in the range of chemical shift -73.0~-120.0ppm NMR spectra and peak area of the siloxane structure portion (Q0 structure ~Q4 structure), the chemical shift of -100. The range of 0 to −120.0 ppm was defined as the peak area (S ₄ ) of the Q4 structure, and the range of −82.0 to −100.0 ppm was also defined as the peak area (S ₃ ) of the Q3 structure. The ratio of the peak area of each structure was calculated by (S _i / S _T ) × 100 [%] (i = 3 or 4).

[2] Measurement of average particle size by dynamic light scattering method
The silica sol is diluted with 0.58% aqueous ammonia to adjust the solid content concentration of the silica fine particles to 1% by weight. The silica sol is filled in a 10 mm square plastic cell, and a laser particle analyzer (manufactured by Otsuka Electronics Co., Ltd.). Laser particle size analysis system: LP-510 model PAR-III, measurement principle: dynamic light scattering method, measurement angle 90 °, light receiving element: photomultiplier tube 2 inches, measurement range: 3 nm to 5 μm, light source: He—Ne The average particle diameter A [nm] was measured using a laser (5 mW, 632.8 nm) The silica sol in the cell was adjusted to 25 ° C.

[3] Measurement of average particle size by nitrogen adsorption method
A sample prepared by adjusting 50 mL of silica sol to 3.5 with HNO ₃ , adding 40 mL of 1-propanol, and drying at 110 ° C. for 16 hours was pulverized in a mortar and then calcined at 500 ° C. for 1 hour in a muffle furnace. A sample was prepared. And the specific surface area was computed by the BET 1 point method from the adsorption amount of nitrogen using the nitrogen adsorption method (BET method) using the specific surface area measuring apparatus (The product made from Yuasa Ionics, model number multisorb 12).

In the specific surface area measuring apparatus, 0.5 g of the baked sample is placed in a measurement cell, degassed for 20 minutes at 300 ° C. in a mixed gas stream of nitrogen 30 v% / helium 70 v%, and the sample is mixed with the above mixed gas. Liquid nitrogen temperature was maintained in an air stream, and nitrogen was adsorbed on the sample in an equilibrium manner. Next, the sample temperature was gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that time was detected, and the specific surface area SA of the silica fine particles in the sample was calculated using a calibration curve prepared in advance. Moreover, the average particle diameter B [nm] was calculated | required from the following (1) formula.
B = 6000 / (ρ × SA) (1)
Where ρ: density of the sample (2.2 [g / cm ³ ] was used for silica)
SA: specific surface area of the sample [m ² / g]

[4] Polishing test
(1) Substrate to be polished
As the substrate to be polished, a glass substrate made of aluminosilicate for hard disk was used. This glass substrate made of aluminosilicate for a hard disk is a donut-shaped substrate (outer diameter 65 mmΦ / inner diameter 20 mmΦ−thickness 0.635 mm). This substrate was first polished and the surface roughness (RA) was 0.3 nm.

(2) Polishing test
The substrate to be polished is set in a polishing apparatus (Nano Factor Co., Ltd .: NF300), and a polishing pad ("Polytex" manufactured by Nitta Haas) is used, with a substrate load of 0.05 MPa and a table rotation speed of 30 rpm. Polishing was performed by supplying a polishing silica sol having a solid content concentration of 15 wt% at a rate of 20 g / min for 5 minutes.

(3) Polishing rate ratio
The polishing rate was calculated from the difference in weight of the polishing substrate before and after polishing and the polishing time. The polishing rate ratio was calculated by setting the polishing rate of the Cataloid SI-80P of Comparative Example 5 to 1.0.

(4) Particle Substrate Remaining For the particle substrate remaining, the front surface was visually observed at 15 using an ultra fine defect / visualization macro apparatus (manufactured by VISION PSYTEC, product name: Micro-MAX), 65 where there is no white stain-like defects good present in polished substrate surface corresponding to .97cm ² (○), when the disabled (×), thereof is white stain significant area is observed Those in between were evaluated as (Δ).

(5) Measurement of scratches (linear marks)
Regarding the occurrence of scratches, after polishing the aluminum disk substrate by the method described in (2), using an ultra fine defect / visualization macro apparatus (product name: Micro-MAX, manufactured by VISION PSYTEC), Zoom 15 The number of scratches (linear traces) having a length of 100 μm or more present on the polished substrate surface corresponding to 65.97 cm ² was counted and totaled. The case where the number of scratches was 3 or less was evaluated as good (◯), the case where it was 4 to 20 was acceptable (Δ), and the case where it was 20 or more was evaluated as impossible (×).

Example 1
After dissolving 462.5 g of sodium silicate in water and preparing a 24 wt% sodium silicate aqueous solution in terms of SiO ₂ , 25 wt% sulfuric acid was added so that the pH was 4.5, and silica hydrogel was added. A solution containing is obtained. The silica hydrogel solution is maintained at a temperature of 21 ° C. in a thermostatic bath and left to stand for 5.75 hours for aging, and then the content of sodium sulfate is 0 with respect to silicon as SiO ₂ contained in the silica hydrogel. Wash with pure water until the content becomes 0.05% by weight (corresponding to a molar ratio of [SiO ₂ ] / [SO ₄ ²⁻ ] of 6208). 15% by weight ammonia water was added as an alkaline solution (corresponding to a molar ratio of [SiO ₂ ] / [NH ₃ ] corresponding to 1) so that the pH of the silica hydrogel dispersion after washing was 10.5. The resulting dispersion was maintained at 95 ° C. while stirring with a stirrer and held for 4 hours to peptize the silica hydrogel to obtain a silica sol containing silica fine particles. The concentration of silica hydrogel in the dispersion was 3% by weight as the SiO ₂ content.

The obtained silica sol was heated in an autoclave at a temperature of 150 ° C. and a pressure of 0.15 MPa for 1.3 hours (first hydrothermal treatment), and the average particle size of silica fine particles was 17 nm (measured by a nitrogen adsorption method). Grown up to. The appearance of the silica fine particles observed with an electron microscope was non-spherical. Subsequently, 650 mL of pure water was supplied to 3.3 L of silica sol after the first hydrothermal treatment was performed, and the concentration in terms of SiO ₂ was adjusted to 15% by weight with an ultrafiltration membrane while washing. 14.8 mL of 5 wt% NaOH was added, and 5.3 mL of 5 wt% sulfuric acid was added as a source of SO ₄ ²⁻ anionic species. The molar ratio of “SiO ₂ / NaOH” was 360, and the molar ratio of “SiO ₂ / SO ₄ ²⁻ ” was 611. The silica sol to which alkali species and anion species are added is heated in an autoclave at a temperature of 160 ° C. and a pressure of 0.16 MPa for 1 hour (second hydrothermal treatment) to remove impurities in the silica fine particles and to remove silanol groups. Condensation was performed.

  The obtained silica sol was prepared by adjusting a polishing silica sol so that the solid content would be 30% by weight using a rotary evaporator. To 667 mL of this polishing silica sol, ion-exchanged water is added to adjust the silica concentration to 9% by weight, and 5% by weight NaOH is added as a pH adjusting agent so that the pH becomes 10.5. A product was prepared and subjected to a polishing test. The production conditions of the silica sol relating to (Example 1) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Example 2)
The amount of NaOH added as an alkali species in the second hydrothermal treatment was changed to 33.73 mL, the molar ratio of “SiO ₂ / NaOH” was 158, and the treatment time was 6 hours (Examples) A polishing silica sol and a polishing composition were prepared under the same conditions as in 1). The production conditions of the silica sol relating to (Example 2) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Example 3)
In order to change the amount of NaOH added as an alkali species in the second hydrothermal treatment to 33.73 mL and change the molar ratio of “SiO ₂ / NaOH” to 158, and to change the anionic species to NO ₃ ⁻ , A polishing silica sol and a polishing composition were prepared under the same conditions as in Example 1, except that 0.34 mL of 5 wt% nitric acid was added as an anion seed source. The production conditions of the silica sol relating to (Example 2) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

Example 4
In the second hydrothermal treatment, the amount of NaOH added as an alkali species was changed to 33.73 mL to change the molar ratio of “SiO ₂ / NaOH” to 158, and the anion species was changed to Cl ⁻ , A polishing silica sol and a polishing composition were prepared under the same conditions as in Example 1, except that 2 mL of 5 wt% hydrochloric acid was added as an ion species source. The production conditions of the silica sol relating to (Example 3) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Example 5)
The amount of NaOH added as an alkali species in the second hydrothermal treatment was changed to 17.8 mL, the molar ratio of “SiO ₂ / NaOH” was set to 300, and the processing temperature was set to 200 ° C. A polishing silica sol and a polishing composition were prepared under the same conditions as in Example 1). The production conditions of the silica sol relating to (Example 5) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Example 6)
The same conditions as in Example 1 except that the alkali species added in the second hydrothermal treatment was changed to 5 wt%, 23.7 mL of KOH, and the molar ratio of “SiO ₂ / KOH” was 158. A polishing silica sol and a polishing composition were prepared. The production conditions of the silica sol relating to (Example 6) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Example 7)
Except that the alkali species added in the second hydrothermal treatment was changed to 5 wt%, which is a quaternary amine, 38.4 mL of TMAH and the molar ratio of “SiO ₂ / TMAH” was changed to 158 (Examples) A polishing silica sol and a polishing composition were prepared under the same conditions as in 1). However, (TMAH) indicates “[(CH ₃ ) ₄ N] ⁺ OH ⁻ ”. The production conditions of the silica sol relating to (Example 7) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Example 8)
At the time of washing after ripening, washing with pure water until the content of sodium sulfate is 0.05% by weight with respect to SiO ₂ contained in the silica hydrogel, the mole of [SiO ₂ ] / [SO ₄ ²⁻ ] A point where the ratio was 611, a point where the alkaline solution added when the silica hydrogel was peptized was changed to a 5 wt% NaOH solution (the value of the molar ratio of [SiO ₂ ] / [NaOH] was 158), In the first hydrothermal treatment, the treatment temperature was 160 ° C., the treatment pressure was 0.16 MPa, the silica particles were grown until the average particle size was 21 nm, and NaOH added as an alkali species in the second hydrothermal treatment. For the polishing under the same conditions as in Example 1, except that the amount of slag was changed to 23 mL and the molar ratio of “SiO ₂ / NaOH” was changed to 158 and the second hydrothermal treatment was performed for 6 hours. Silica sol and A polishing composition was prepared. The production conditions of the silica sol relating to (Example 8) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Comparative Example 1)
(Example 1) except that the amount of sulfuric acid added as an anionic species in the second hydrothermal treatment was changed to 1.3 mL and the molar ratio of “SiO ₂ / SO ₄ ²⁻ ” was 2500. A polishing silica sol and a polishing composition were prepared under the same conditions. The manufacturing conditions of the silica sol concerning (Comparative Example 1) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Comparative Example 2)
Under the same conditions as in Example 1, except that the amount of NaOH added as an alkali species in the second hydrothermal treatment was changed to 66.7 mL and the molar ratio of “SiO ₂ / NaOH” was 80. A polishing silica sol and a polishing composition were prepared. The manufacturing conditions of the silica sol relating to (Comparative Example 2) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Comparative Example 3)
To the silica sol after the first hydrothermal treatment, NaOH is added so that the molar ratio of “SiO ₂ / NaOH” is 158, and sulfuric acid is added so that the molar ratio of “SiO ₂ / SO ₄ ²⁻ ” is 611. After the addition, a polishing silica sol and a polishing composition were prepared under the same conditions as in (Example 1) except that the heat treatment was not performed and the second hydrothermal treatment was not performed. The manufacturing conditions of the silica sol concerning (Comparative Example 3) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Comparative Example 4)
The molar ratio of “SiO ₂ / NaOH” is 246 in a commercially available silica sol (manufactured by JGC Catalysts & Chemicals, Cataloid SI-80P, concentration as SiO ₂ ; 3 wt%, silica fine particle shape; sphere, average particle diameter; 80 nm). NaOH was added so that the molar ratio of “SiO ₂ / Cl ⁻ ” was 400, and then heating corresponding to the second hydrothermal treatment was performed under the same conditions as in Example 1. Processing was performed to prepare a polishing silica sol and a polishing composition. The manufacturing conditions of the silica sol concerning (Comparative Example 4) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Comparative Example 5)
A polishing silica sol and a polishing composition were prepared under the same conditions as in (Comparative Example 4) except that the heat treatment was not performed after the addition of the alkali species (NaOH) and the anionic species (Cl ⁻ ). The manufacturing conditions of the silica sol concerning (Comparative Example 5) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Comparative Example 6)
At the time of washing after ripening, washing with pure water until the content of sodium sulfate is 0.05% by weight with respect to SiO ₂ contained in the silica hydrogel, the mole of [SiO ₂ ] / [SO ₄ ²⁻ ] The first hydrothermal treatment was performed for 3 hours under the conditions of a temperature of 160 ° C. and a pressure of 0.16 MPa to obtain a silica sol containing non-spherical silica fine particles having an average particle diameter of 20 nm; The amount of NaOH added as an alkali species after hydrothermal treatment is changed to 33.73 mL so that the molar ratio of “SiO ₂ / NaOH” is 158, and then the second hydrothermal treatment is not performed. A polishing silica sol and a polishing composition were prepared under the same conditions as in Example 1). The manufacturing conditions of the silica sol concerning (Comparative Example 6) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

(Comparative Example 7)
The amount of NaOH added as an alkali species after the first hydrothermal treatment was changed to 33.73 mL to change the molar ratio of “SiO ₂ / NaOH” to 158, and then the second hydrothermal treatment was not performed. A polishing silica sol and a polishing composition were prepared under the same conditions as in Example 1. The production conditions of the silica sol relating to (Comparative Example 7) are shown in (Table 1), and the physical properties of the obtained silica sol and the results of the polishing test are shown in (Table 2).

  According to the results of (Examples 1 to 8) shown in (Table 2), after performing the first hydrothermal treatment, the second hydrothermal treatment is performed by adding a predetermined amount of alkali species and anionic species. In the silica sol, the ratio of the peak area of the Q4 structure to the total area of peaks in the chemical shift range of -73.0 to -120.0 ppm is 89% to 91% within the range of 88% or more. The ratio of the peak area of the Q3 structure is 8 to 10% within a range of 11% or less. In addition, the ratio of the average particle diameter [A] of the non-spherical silica fine particles measured by the dynamic light scattering method to the average particle diameter [B] measured by the nitrogen adsorption method [A / B] is 2.0 to It was 2.2 to 4.1 within the range of 5.0. At this time, the polishing rate ratio was higher in all examples than in the comparative example, and the evaluation results of the remaining base material for surface particles and scratches were good.

  On the other hand, when the addition amount of the alkali species is excessive as in (Comparative Example 1), or when the addition amount of the anionic species is excessively small as in (Comparative Example 2), the polishing rate ratio is higher than that in the example. Some of the evaluation items were slightly inferior with respect to the remaining base material of the surface particles and scratches.

When the second hydrothermal treatment is not performed as in (Comparative Examples 3, 6, and 7), the ratio of the peak area of the Q4 structure is as low as 86%, and the ratio of the peak area of the Q3 structure is 13%. As the polishing rate increased and the polishing rate ratio decreased, the evaluation of the remaining base material of the surface property particles was bad.
In addition, when a silica sol containing commercially available spherical silica fine particles is used, even if the second hydrothermal treatment is performed as in (Comparative Example 4), it is not necessary to perform this as in (Comparative Example 5). The polishing rate ratio was small.

  From the above, after the first hydrothermal treatment is performed to grow the non-spherical silica fine particles, a predetermined amount of alkali species and anionic species are added and the second hydrothermal treatment is performed to condense the silanol groups. By proceeding, the ratio of the peak area of the Q4 structure to the total area of the peak in the range of the chemical shift of 73.0 to -120.0 ppm of silica fine particles is 88% or more, and the ratio of the peak area of the Q3 structure It can be seen that it can be adjusted to 11% or less. It was confirmed that the polishing silica sol in which silica fine particles having this requirement were dispersed had good polishing characteristics.

Claims (6)

A non-spherical silica fine particle having an average particle diameter measured by a dynamic light scattering method in a range of 5 to 300 nm is dispersed in a dispersion medium, and a silica sol having a solid content concentration of 10 to 60% by mass,
²⁹ The chemical shift at the time of Si-NMR spectrum measurement The area of Q4 in the peak area of −73 to −120 ppm is 88% or more and 91% or less, the area of Q3 is 8% or more and 11% or less ,
When the average particle diameter of the non-spherical silica fine particles measured by the dynamic light scattering method is [A] and the average particle diameter [B] measured by the nitrogen adsorption method is A / B value of the non-spherical silica fine particles. Is a silica sol for polishing, characterized by being in the range of 2.0 to 5.0 .
However, the chemical shift uses tetramethylsilane as a reference substance, Q4 is a peak in the range of −100 to −120 ppm, and Q3 is a peak in the range of −82 to −100 ppm. Abrasive silica sol of claim 1 having the following characteristics.
1) The value of the molar ratio defined by SiO ₂ / MOH (M is Na, K or quaternary amine) of the silica sol is 100 to 420.
2) The value of the molar ratio defined by SiO ₂ / X (X is SO ₄ ²⁻ , Cl ⁻ , NO ₃ ⁻ or PO ₄ ³⁻ ) of the silica sol is 400 to 1000. The non-spherical absolute value of the surface charge density of the silica fine particles 0.3~1.3 [μeq / m ^2] according to claim 1 or claim 2 abrasive silica sol, wherein in the range of. One or more kinds of additives selected from the group consisting of the silica sol for polishing according to any one of claims 1 to 3 and an additive group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster and a pH buffer. Polishing composition characterized by including an agent. Mixing an alkali silicate and an inorganic acid, adjusting the pH of the mixed solution to a range of 3 to 7, and preparing a solution containing silica hydrogel;
Washing and removing the salt contained in the solution obtained in this step;
The solution obtained by adding an alkali solution to the silica hydrogel after the salt has been removed is stirred while maintaining the temperature range of 60 to 100 ° C., and the silica hydrogel is peptized to contain non-spherical silica fine particles. Obtaining a silica sol;
Holding the solution containing the silica sol obtained in this step in a temperature range of 130 to 300 ° C. and a pressure range of 0.13 to 0.30 MPa to perform a first hydrothermal treatment to grow non-spherical silica fine particles; ,
An alkali species and an anion species are added to a silica sol containing non-spherical silica fine particles grown by the first hydrothermal treatment, and maintained at a temperature range of 130 to 300 ° C. and a pressure range of 0.13 to 0.30 MPa. to perform a second hydrothermal treatment, viewed contains a step to advance the condensation of silanol groups in the silica particles, and
A method for producing a polishing silica sol, wherein the addition amount of alkali species and anion species in the second hydrothermal treatment step satisfies the following conditions 1) and 2) .
1) The alkali species is selected from the group of alkali species consisting of NaOH, KOH and quaternary amine, and the molar ratio of alkali species to silica in the silica sol is SiO ₂ / MOH (M is Na, K or quaternary amine). ), The molar ratio value is 100 to 420.
2) The anionic species is selected from the group of anionic species consisting of SO ₄ ²⁻ , Cl ⁻ , NO ₃ ⁻ or PO ₄ ^3−, and the molar ratio of the anionic species to silica in the silica sol is SiO ₂ / X ( When X is represented by SO ₄ ²⁻ , Cl ⁻ , NO ₃ ⁻ or PO ₄ ³⁻ ), the molar ratio value is 400 to 1000. The first hydrothermal treatment is performed in a range of 2 to 5% by weight of silica fine particles in the silica sol, and the second hydrothermal treatment is in a range of 10 to 20% by weight of silica fine particles in the silica sol. The method for producing a polishing silica sol according to claim 5 , wherein