Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B37/00—Lapping machines or devices; Accessories
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
  • C01B33/141—Preparation of hydrosols or aqueous dispersions
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
  • C01B33/141—Preparation of hydrosols or aqueous dispersions
  • C01B33/142—Preparation of hydrosols or aqueous dispersions by acidic treatment of silicates
  • C01B33/143—Preparation of hydrosols or aqueous dispersions by acidic treatment of silicates of aqueous solutions of silicates
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09G—POLISHING COMPOSITIONS; SKI WAXES
  • C09G1/00—Polishing compositions
  • C09G1/02—Polishing compositions containing abrasives or grinding agents
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K3/00—Materials not provided for elsewhere
  • C09K3/14—Anti-slip materials; Abrasives
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P52/00—Grinding, lapping or polishing of wafers, substrates or parts of devices
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/51—Particles with a specific particle size distribution
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area

Definitions

• the present invention relates to a dispersion of silica fine particles suitable for polishing various electronic materials such as silicon wafers, silicon carbide wafers, sapphire wafers, compound semiconductor wafers, and magnetic disks.
• silica sol, fumed silica, and fumed alumina have been used as polishing particles.
• aluminum wiring is formed on a silicon wafer, and an oxide film such as silica is placed on top of this as an insulating film. In this case, unevenness is created by the wiring, so this oxide film is polished to flatten it.
• polishing such substrates what is required is a flat surface without steps or unevenness, a smooth surface without microscopic scratches, and a high polishing speed.
• Patent Document 1 As a method for obtaining large-sized irregularly shaped particles, as shown in Patent Document 1, a method is known in which porous silica gel is pulverized using a bead mill or the like to prepare an irregularly shaped porous gel, and this irregularly shaped porous gel is grown into particles using silicic acid or the like to obtain large-sized irregularly shaped particles with a high degree of irregularity.
• the irregularly shaped particles (non-spherical particles) described in Patent Document 1 have a relatively high polishing rate when used in polishing applications compared to spherical particles.
• the irregularly shaped particles described in Patent Document 1 have the problem that they tend to deteriorate the surface roughness and surface waviness of the polished substrate after polishing processing, and are prone to scratching.
• multiple attempts to manufacture irregularly shaped particles using the manufacturing method described in Patent Document 1 revealed problems such as poor reproducibility of particle size and tendency for polishing performance to vary.
• the spherical silica microparticles with a broad particle size distribution described in Patent Document 2 have a superior polishing rate as far as they are compared with spherical silica microparticles with a sharp particle size distribution.
• the present invention aims to provide a dispersion of silica microparticles for polishing that, when applied to polishing purposes, exhibits an excellent polishing rate and can suppress the occurrence of scratches on the substrate being polished.
• a dispersion of silica fine particles for polishing which is obtained by dispersing in a solvent a particle group containing silica fine particles (having a particle size calculated based on a specific surface area in the range of 5 nm to 200 nm) and which satisfies the following requirements 1) to 4): 1) The average sphericity of the particle group is in the range of 0.85 to 1.00.
• the cumulative 10% particle size (D 10 ), cumulative 90% particle size (D 90 ), and cumulative 50% particle size (D 50 ), calculated from the smaller particle size satisfy the following formula (F1): 0.5 ⁇ (D 90 -D 10 )/D 50 ⁇ 3.0...(F1) 3)
• the particle group has a weight-converted particle size distribution having a peak on the large particle size side.
• the particle group contains irregularly shaped particles in an amount of 0.01% by number to 10% by number.
• a polishing composition comprising the silica fine particle dispersion for polishing according to the one aspect of the present invention and at least one selected from a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster, and a pH buffer.
• a method for producing a dispersion of fine silica particles for polishing comprising the following steps 1a to 3a.
• Step 1a A step of introducing the seed particle dispersion and an alkali into a reaction vessel kept in an unheated state to obtain a prepared liquid
• step 2a Following step 1a, the prepared liquid is stirred uniformly, then heated to 40°C or higher and 98°C or lower and maintained at the same temperature range, and then the next steps A and B are carried out simultaneously, and the reaction liquid is further aged at 40°C or higher and 98°C or lower for 20 minutes to 120 minutes.
• Step A A reaction liquid is prepared by continuously or intermittently adding an acidic silicic acid solution and an alkali to the reaction vessel filled with the prepared liquid.
• Step B A part of the reaction liquid is continuously or intermittently withdrawn from the reaction vessel (step 3a). A step of mixing the reaction liquid remaining in the reaction vessel at the end of the step 2a with the reaction liquid extracted in the treatment B of the step 2a to obtain a dispersion of silica fine particles for polishing.
• a method for producing a dispersion of silica fine particles for polishing comprising the following steps 1b to 4b.
• Step 1b A step of introducing an acidic silicic acid solution and an alkali into a reaction vessel that is kept unheated to obtain a first mixed solution.
• Step 2b Following step 1b, the first preparation is stirred uniformly, then heated to 40°C or higher and 98°C or lower, and maintained at the same temperature range. Then, while maintaining the temperature range, an acidic silicic acid liquid is added continuously or intermittently to obtain a second preparation.
• Step 3b A step of simultaneously carrying out the next process A and process B following the step 2b.
• Treatment A An acidic silicic acid solution and an alkali are added continuously or intermittently to the reaction vessel filled with the second preparation liquid to prepare a reaction liquid.
• Treatment B A part of the reaction solution in the reaction vessel of Treatment A is withdrawn continuously or intermittently.
• the reaction liquid obtained in the treatments A and B of the step 3b is aged at a temperature in the range of 40°C to 98°C for 20 minutes to 120 minutes, and then the reaction liquid extracted in the treatment B of the step 3b is added and mixed to obtain a dispersion of silica fine particles for polishing.
• the present invention provides a silica microparticle dispersion for polishing that, when applied to polishing purposes, exhibits an excellent polishing rate and can suppress the occurrence of scratches on the substrate to be polished, and a method for producing the same.
• the silica fine particle dispersion for polishing according to this embodiment is prepared by dispersing a particle group containing silica fine particles as abrasive grains in a solvent.
• the particle group must satisfy the following requirements 1 to 4.
• the "dispersion of silica fine particles for polishing” may be simply referred to as "dispersion”.
• the "particle group containing silica fine particles” dispersed in the dispersion of silica fine particles for polishing may be simply referred to as "particle group”.
• the silica microparticle dispersion for polishing according to this embodiment exhibits an excellent polishing rate, improves the surface roughness of the substrate to be polished, and suppresses the occurrence of scratches when applied to polishing purposes are not entirely clear, but the inventors speculate as follows. That is, the particle group according to this embodiment has a broad particle size distribution. Therefore, compared with conventional polishing abrasive grains, the polishing speed can be improved. Furthermore, the particle size distribution has a peak on the large particle size side, that is, the large particle size side does not tail, so no extremely large particles are included. Furthermore, since the shape is spherical, the surface roughness can be improved and the occurrence of scratches can be suppressed.
• the particle group according to this embodiment contains a small amount of irregular silica fine particles while being mainly composed of spherical silica fine particles.
• the irregular silica fine particles can improve the polishing speed, and since the amount of the irregular silica fine particles is small, there is little adverse effect on the surface roughness or scratches.
• the inventors presume that the above-mentioned effects of the present invention can be achieved in the above manner.
• seed particles are added to a non-heated reaction vessel during preparation, and the seed particles are not added to the reaction vessel thereafter.
• the aggregation of the seed particles can be prevented, and since the seed particles are not added during preparation, the load on the manufacturing equipment can be reduced, the load on process management can be reduced, and it is possible to efficiently manufacture the silica fine particle dispersion for polishing.
• the inventors speculate that the above-mentioned effects of the present invention are achieved in the above-mentioned manner.
• the second manufacturing method of the silica microparticle dispersion liquid for polishing is a process of adding acidic silicic acid liquid to a non-heated reaction vessel when charging.Therefore, it is possible to prevent the acidic silicic acid liquid from drying, and in step 3b, seed particles are not added during mixing, so the load on the manufacturing equipment can be reduced, the load on process management can be reduced, and it is possible to efficiently manufacture the silica microparticle dispersion liquid for polishing.
• the inventors presume that the above-mentioned effect of the present invention is achieved in the above-mentioned way.
• the requirements and characteristics of the silica microparticle dispersion for polishing according to this embodiment including the specific surface area converted particle size, average sphericity, weight converted cumulative particle size distribution, peak of particle size distribution, irregular particle rate, and coefficient of variation of particle size distribution area.
• the explanation of the effect or performance due to each requirement or characteristic means the effect or performance when the silica microparticle dispersion for polishing according to this embodiment is applied to polishing purposes.
• the particle diameter in terms of specific surface area of the particle group according to this embodiment must be in the range of 5 nm to 200 nm. If the particle diameter in terms of specific surface area is within the above range, it is suitable for use in silicon wafers, magnetic disks, or semiconductors.
• a high polishing rate can be obtained and furthermore, the occurrence of scratches on the object to be polished can be suppressed, and polishing can be performed smoothly.
• the surface of the object can be made smoother. If the particle size is less than 5 nm, it becomes difficult to achieve a practically sufficient polishing rate.
• the particle size of the particle group converted into specific surface area is preferably in the range of 10 nm or more and 150 nm or less, and more preferably in the range of 20 nm or more and 100 nm or less.
• the average sphericity of the particle group according to this embodiment must be in the range of 0.85 or more and 1.00 or less (requirement 1).
• the particle group includes spherical particles.
• the spherical particles refer to particles having an average sphericity in the range of 0.85 to 1.00, and the average sphericity can be calculated by calculating the minor axis/major axis of each silica fine particle from the observation results of an electron microscope photograph described later and calculating the simple average thereof.
• the average sphericity value of the particle group is 0.85 or more
• the silica microparticle dispersion liquid for polishing according to the present embodiment which is made by dispersing such particle group in a solvent, is used for polishing
• the surface roughness of the polishing substrate can be smoothed, and the occurrence of scratches can also be suppressed.
• the particle group contains irregular particles in the range of 0.01 number % or more and 10.0 number % or less, as long as the average sphericity of the particle group is within the above range, scratches can also be suppressed. Note that the action and effect of the irregular particles (irregular silica particles) contained in the particle group will be described later.
• the average sphericity of the particle group is preferably in the range of 0.90 or more and 1.00 or less, and more preferably in the range of 0.92 or more and 1.00 or less.
• the specific method for measuring the average sphericity of the particle group according to this embodiment is as described later.
• the cumulative 10% particle size (D 10 ), cumulative 90% particle size (D 90 ), and cumulative 50% particle size ( D 50 ) must satisfy the following formula (F1) (requirement 2).
• F1 weight equivalent cumulative particle size distribution
• the value of (D 90 -D 10 )/D 50 in the formula (F1) indicates the width of the particle size distribution, and the larger the value of (D 90 -D 10 )/D 50 , the wider the particle size distribution. That is, when the value of (D 90 -D 10 )/D 50 is large, it indicates that the particles have both small and large particle diameters.
• Particles with a large particle size exhibit a high polishing rate, and small particles exhibit a scratch repair effect. Therefore, a silica microparticle dispersion with such a particle size distribution can achieve both a high polishing rate and the suppression of scratch generation. It can be said that. If the value of (D 90 -D 10 )/D 50 is in the range of 0.5 to 3.0, the particle size distribution is sufficiently broad and contains an appropriate amount of small particles and large particles. Generally, the larger the particle size, the higher the polishing rate. However, as the particle size increases, the problem of scratches on the substrate increases.
• the value of ((D 90 -D 10 )/D 50 ) is preferably in the range of 0.6 to 2.0, and more preferably in the range of 0.8 to 1.8.
• the particle group contains non-spherical irregular-shaped particles at 0.01% by number or more and 10.0% by number or less (requirement 4).
• the irregularly shaped particles that are not spherical are particles with a minor axis/major axis ratio of less than 0.85, which can be calculated from the observation results of the electron microscope photograph described later.
• Such irregularly shaped particles generally exhibit a high polishing rate, but tend to cause scratches on the substrate surface.
• the irregularly shaped particle ratio (number of irregularly shaped particles/total number of particles x 100) is in the range of 0.01% by number to 10.0% by number
• the irregularly shaped particles contained in the range of the number percent contribute to a high polishing rate, while the remaining spherical particles suppress the generation of scratches on the substrate surface, and further the generated scratches can be repaired, so that both a high polishing rate and the achievement of smoothness of the polished substrate surface after polishing can be achieved.
• the irregularly shaped particle ratio of the particle group is less than 0.01% by number, the effect of improving the polishing rate by the irregularly shaped particles is not observed.
• the irregular particle ratio is preferably in the range of 0.05% by number to 10.0% by number, more preferably in the range of 0.10% by number to 10.0% by number, and particularly preferably in the range of 1.0% by number to 10.0% by number.
• irregular particles refer to irregular silica particles.
• the irregular particle ratio may be in the range of 0.01% by number to 8.0% by number, or may be in the range of 0.01% by number to 5.0% by number.
• the irregular particle ratio can be measured as follows. That is, the silica microparticle dispersion is observed in a photograph or image obtained by an electron microscope at a magnification of 200,000 times. Specifically, an image is taken so that 200 or more particles are included in the same field of view, and the minor axis/major axis ratio of each of the 200 or more silica microparticles in the obtained photograph or image is measured, the number of particles (n) having a minor axis/major axis ratio of less than 0.85 (irregularly shaped particles) is calculated, and the irregular particle ratio is calculated by the following formula.
• the irregular particle rate in the particle group according to this embodiment is preferably in the range of 1.3% by number or more and 9.0% by number or less, more preferably in the range of 1.8% by number or more and 8.0% by number or less, and particularly preferably in the range of 2.0% by number or more and 7.0% by number or less.
• the particle group further satisfies the following requirement 5).
• the particle size distribution consisting of the particle size/particle number of the particle group when the particle size range from the cumulative 1% particle size ( D1 ) to the cumulative 99% particle size ( D99 ) integrated from the smaller particle size side is divided into 6 equal particle size ranges S1, S2, S3, S4, S5, and S6, the coefficient of variation (CV value) of the particle size distribution area corresponding to each particle size range is in the range of 20.0% or more and 70.0% or less. Since the particle size distribution of ordinary silica sol shows a normal distribution, the CV value is a high value of more than 70.0%.
• the CV value when the CV value is in the range of 20.0% or more and 70.0% or less, the area of S1 to S6 is relatively uniform, and the shape of the particle size distribution is generally close to a trapezoid or a rectangle while having a peak on the large particle diameter side.
• large particles with a high polishing rate, small particles that suppress scratches, and medium particles with a good balance between polishing rate and scratch suppression are relatively uniformly included. Therefore, it is possible to achieve both a high polishing rate and scratch suppression.
• the CV value is less than 20.0%, it is difficult to obtain such a particle size distribution.
• the polishing rate tends to be slow because it is close to a normal distribution.
• the CV value is more preferably in the range of 22.0% or more and 65.0% or less, and particularly preferably in the range of 25.0% or more and 62.0% or less.
• the dispersion liquid of fine silica particles for polishing further satisfies the following requirement 6).
• the mass ratio of polyethyleneimine to the mass of silica at the equivalence point is in the range of 1.0 to 1.9.
• the ratio (V/ SiO2 ) of the amount (V [g]) of the cationic solid content [cationic polymeric polyethyleneimine (weight average molecular weight 600)] added in the cationic titration solution in the Knick to the SiO2 solid content [g] is in the range of 1.0 or more and 1.9 or less.
• V/ SiO2 is in the range of 1.0 or more and 1.9 or less, a good polishing rate can be obtained when such a silica fine particle dispersion is used for polishing.
• V/ SiO2 is less than 1.0, when a cationic additive is mixed into the polishing liquid and used for polishing, the polishing rate may decrease due to a decrease in dispersion stability of the silica fine particles, which is not preferable.Also, if V/ SiO2 is more than 1.9, when a cationic additive is mixed into the polishing liquid and used for polishing, the polishing rate may decrease due to the cationic additive excessively adsorbed on the silica fine particles inhibiting polishing, which is not preferable. More preferably, V/ SiO2 is in the range of 1.3 to 1.8. V/ SiO2 is determined by cation titration.
• silica fine particles The fact that the silica microparticles according to this embodiment are made of silica can be confirmed, for example, by an ICP device (inductively coupled plasma emission spectrometry device).
• ICP device inductively coupled plasma emission spectrometry device
• 1 g of the aqueous dispersion containing the silica microparticles according to this embodiment is collected in a 30 mL zirconia bowl with a lid, dried (200° C., 20 minutes), and then 2 g of Na 2 O 2 and 1 g of NaOH are added and melted for 15 minutes.
• 10 mL of 98% by mass sulfuric acid and 10 mL of pure water are added to dissolve, and then the mixture is diluted with pure water to 500 mL to obtain a sample.
• the silicon content of the obtained sample can be measured using an ICP device (Shimadzu Corporation, ICPS-8100, analysis software ICPS-8000).
• the particle group according to the present embodiment is made of silica, but may contain 10 mass % or less of components other than silica, such as Al, Ti, Fe, Ca, Mg, Cr, Ni, Cu, Zn, K, Na, or oxides thereof.
• components other than silica such as Al, Ti, Fe, Ca, Mg, Cr, Ni, Cu, Zn, K, Na, or oxides thereof.
• the particle group of the present invention is made of silica using, for example, an ICP device.
• the content of components other than silica that may be contained in the particle group of the present invention can be specified and quantified, for example, using an inductively coupled plasma optical emission spectrometer.
• Ni, Cu, K and Na can be specified and quantified using an atomic absorption spectrophotometer.
• the dispersion according to this embodiment is obtained by dispersing the particle group according to this embodiment in a solvent.
• the solvent include water, alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, and water-soluble organic solvents such as ethers, esters, and ketones.
• a mixed solvent consisting of water and an organic solvent may also be used.
• the content of the particle group in the dispersion according to this embodiment is preferably in the range of 1% by mass to 50% by mass, and more preferably in the range of 10% by mass to 50% by mass.
• the content of the particle group according to the present embodiment is determined by subjecting the silica microparticle dispersion liquid to ignition loss at 1000°C, weighing the obtained solid content, and subtracting the separately calculated alkali content converted into an oxide (e.g., Na2O ).
• the polishing composition of this embodiment contains the silica microparticle dispersion for polishing of this embodiment or the particle group of this embodiment and a solvent, and further contains components that impart necessary performance including polishing performance.
• the components that impart the necessary performance include polishing accelerators, surfactants, hydrophilic compounds, heterocyclic compounds, pH adjusters, and pH buffers.
• the polishing composition may contain only one of these components as the components that impart the necessary performance, or may contain two or more of them.
• the polishing composition according to this embodiment is also called "polishing slurry.”
• the silica microparticle dispersion or polishing composition according to this embodiment can be used, for example, as a CMP slurry to polish semiconductor wafers such as silicon wafers, or to polish substrates for hard disk drives, liquid crystal glass, sapphire substrates, compound semiconductors, GaN substrates, or SiC substrates.
• polishing accelerator examples include acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and hydrofluoric acid, or the sodium salts, potassium salts, and ammonium salts of these acids, and mixtures thereof.
• acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and hydrofluoric acid
• the polishing rate of a specific component of the material to be polished can be accelerated, and a flat polished surface can be finally obtained.
• the polishing composition according to this embodiment contains a polishing accelerator, the content thereof is preferably in the range of 0.1 mass % or more and 10 mass % or less, and more preferably in the range of 0.5 mass % or more and 5 mass % or less.
• surfactants and hydrophilic compounds cationic, anionic, nonionic, or amphoteric surfactants or hydrophilic compounds can be added to improve the dispersibility and stability of the polishing composition.
• Both the surfactant and the hydrophilic compound have the effect of reducing the contact angle with the surface to be polished, and thus promoting uniform polishing.
• At least one of the surfactant and the hydrophilic compound may be selected from the following group, for example:
• anionic surfactants include carboxylates, sulfonates, sulfates, and phosphates.
• carboxylates include soaps, N-acylamino acid salts, polyoxyethylene or polyoxypropylene alkyl ether carboxylates, and acylated peptides.
• sulfonates include alkylsulfonates, alkylbenzene and alkylnaphthalenesulfonates, naphthalenesulfonates, sulfosuccinates, ⁇ -olefinsulfonates, and N-acylsulfonates.
• sulfate ester salts examples include sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfates, and alkyl amide sulfates.
• phosphate ester salts examples include alkyl phosphates, polyoxyethylene or polyoxypropylene alkyl allyl ether phosphates, and the like.
• Cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, and imidazolinium salts.
• Amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate salts, imidazolinium betaine, lecithin, and alkylamine oxide.
• Nonionic surfactants include ether type, ether ester type, ester type, and nitrogen-containing type.
• Ether types include polyoxyethylene alkyl and alkylphenyl ethers, alkylarylformaldehyde condensed polyoxyethylene ethers, polyoxyethylene polyoxypropylene block polymers, and polyoxyethylene polyoxypropylene alkyl ethers.
• Ether ester types include polyoxyethylene ethers of glycerin esters, polyoxyethylene ethers of sorbitan esters, and polyoxyethylene ethers of sorbitol esters.
• Ester types include polyethylene glycol fatty acid esters, glycerin esters, polyglycerin esters, sorbitan esters, propylene glycol esters, and sucrose esters.
• Nitrogen-containing types include fatty acid alkanolamides, polyoxyethylene fatty acid amides, and polyoxyethylene alkyl amides.
• Other examples include fluorine-based surfactants.
• the surfactant is preferably an anionic surfactant or a nonionic surfactant.
• the salt may be an ammonium salt, a potassium salt, or a sodium salt, with the ammonium salt and potassium salt being particularly preferred.
• esters such as glycerin esters, sorbitan esters, and alanine ethyl esters
• ethers polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol alkyl ethers, polyethylene glycol alkenyl ethers, alkyl polyethylene glycols, alkyl polyethylene glycol alkyl ethers, alkyl polyethylene glycol alkenyl ethers, alkenyl polyethylene glycols, alkenyl polyethylene glycol alkyl ethers, alkenyl polyethylene glycol alkenyl ethers, polypropylene glycol alkyl ethers, polypropylene glycol alkenyl ethers, alkyl polypropylene glycols, alkyl polypropylene glycol alkyl ethers, alkyl polypropylene glycol alkenyl ethers, and alkenyl polypropy
• any surfactant can be suitably used.
• the substrate is a silicon substrate for semiconductor integrated circuits or the like, and the effects of contamination by alkali metals, alkaline earth metals, halides, or the like must be avoided, it is preferable to use an acid or its ammonium salt surfactant.
• the polishing composition according to this embodiment contains at least one of a surfactant and a hydrophilic compound
• the total content thereof is preferably 0.001 g to 10 g, more preferably 0.01 g to 5 g, and particularly preferably 0.1 g to 3 g, per 1 L of the polishing composition according to this embodiment.
• the surfactant or hydrophilic compound may be of one type, or of two or more types, and different types may be used in combination.
• the polishing composition according to this embodiment may contain a heterocyclic compound in order to form a passivation layer or a dissolution-suppressing layer on the metal and suppress the erosion of the substrate to be polished when the substrate to be polished contains a metal.
• a heterocyclic compound refers to a compound having a heterocycle containing one or more heteroatoms.
• heteroatom refers to an atom other than a carbon atom or a hydrogen atom.
• heterocycle refers to a cyclic compound having at least one heteroatom.
• heteroatom refers only to atoms that form a part of the ring system of a heterocycle, and does not refer to atoms that are located outside the ring system, that are separated from the ring system by at least one non-conjugated single bond, or that are part of a further substituent of the ring system.
• Preferred examples of heteroatoms include, but are not limited to, nitrogen atoms, sulfur atoms, oxygen atoms, selenium atoms, tellurium atoms, phosphorus atoms, silicon atoms, and boron atoms.
• heterocyclic compounds that can be used include imidazole, benzotriazole, benzothiazole, and tetrazole.
• examples include 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, but are not limited to these.
• the content is preferably in the range of 0.001% by mass to 1.0% by mass, more preferably in the range of 0.001% by mass to 0.7% by mass, and even more preferably in the range of 0.002% by mass to 0.4% by mass.
• the pH of the polishing composition can be adjusted by adding an acid or base as necessary.
• an alkaline pH adjuster is used.
• sodium hydroxide, aqueous ammonia, ammonium carbonate, or an amine such as ethylamine, methylamine, triethylamine, or tetramethylamine is used.
• an acidic pH adjuster is used.
• hydroxy acids such as lactic acid, citric acid, malic acid, tartaric acid, and glyceric acid are used.
• a pH buffer may be used.
• pH buffers that can be used include phosphates and borates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium tetraborate tetrahydrate, or organic acids.
• the concentration of the abrasive particles in the polishing composition according to this embodiment is preferably in the range of 0.5% by mass to 50% by mass, and more preferably in the range of 5% by mass to 30% by mass. If the concentration is less than 0.5% by mass, depending on the type of substrate or insulating film, the concentration may be too low, slowing the polishing rate and causing productivity problems. If the concentration of the abrasive particles exceeds 50% by mass, the stability of the abrasive becomes insufficient, and the polishing rate and polishing efficiency do not improve further. Furthermore, dried matter may be generated and adhered during the process of supplying the dispersion liquid for the polishing process, which may cause scratches.
• Step 1a a seed particle dispersion and an alkali are introduced as raw materials into a reaction vessel kept in an unheated state, and a solvent is added as necessary to prepare a mixed liquid.
• a solvent is added as necessary to prepare a mixed liquid.
• splashing occurs on the bottom or inner wall of the reaction vessel or on the liquid surface (the liquid surface of the introduced seed particle dispersion and alkali). If the raw materials are introduced into a heated reaction vessel at this time, the splashed raw materials are likely to dry out and large aggregates are likely to occur, which can be problematic. If the raw materials are introduced gradually so as not to cause splashing, the blending time becomes longer and economic efficiency deteriorates.
• the seed particle dispersion and alkali are added to a heated reaction vessel, the seed particle dispersion and alkali are heated from the beginning of the addition, which also creates the problem that aggregation of the seed particles is likely to occur at an early stage.
• the non-heated state means that no operation for increasing the temperature of the reaction vessel is performed.
• the temperature of the reaction vessel exceeds 40°C in the non-heated state due to seasonal high temperatures, it is recommended to cool the reaction vessel so that the temperature is less than 40°C.
• the temperatures of the seed particle dispersion and the alkali when introduced into the reaction vessel are both preferably less than 40°C.
• a silica fine particle dispersion is used as described later.
• the amounts of the seed particle dispersion and the alkali are added so that the molar ratio of silica to alkali (in terms of oxide) in the prepared solution is in the range of 20 to 160, and further, a solvent is added as necessary to adjust the silica concentration in the prepared solution to be in the range of 1 mass % to 15 mass %.
• the molar ratio of silica to alkali in terms of oxide
• the amount of alkali is excessive, so that the ionic strength in the preparation is excessively high, and the silica fine particles aggregate, making it difficult to obtain spherical particles or prone to sedimentation. Even if sedimentation does not occur, the number of aggregates of silica fine particles increases, making it difficult to obtain a monodispersed silica sol.
• the molar ratio of silica to alkali (oxide equivalent) exceeds 160, the alkali concentration in the preparation liquid will be low, and when an acidic silicic acid solution is added in the subsequent step 2a, the pH of the reaction solution will be significantly low.
• the molar ratio of silica to alkali is preferably in the range of 40 to 140, more preferably in the range of 50 to 130, and particularly preferably in the range of 60 to 120.
• the silica concentration in the preparation is less than 1 mass%, it is easy to obtain monodispersed silica microparticles, but the silica concentration in the preparation is low, so it is not efficient to produce and is uneconomical.
• the silica concentration in the preparation is more preferably in the range of 2 mass% to 10 mass%, and particularly preferably in the range of 3 mass% to 8 mass%.
• the silica microparticles contained in the silica microparticle dispersion according to this embodiment are mostly spherical particles, but contain irregularly shaped particles in an amount of 1.0% by number to 10% by number.
• the seed particle dispersion used in step 1a may be a silica fine particle dispersion.
• the seed particles are silica fine particles.
• the size of the seed particles (particle diameter converted into specific surface area) is not particularly limited, since it can be arbitrarily selected depending on the size of the silica microparticle dispersion liquid to be finally prepared. Usually, a size smaller than the size of the silica microparticles to be finally prepared is selected. Note that, when the silica microparticle dispersion liquid to be finally prepared is used for polishing purposes, it is preferable that the particle diameter converted into specific surface area of the seed particles is selected in the range of 5 nm to 200 nm.
• the silica concentration of the seed particle dispersion is preferably in the range of 1% by mass to 50% by mass, more preferably in the range of 3% by mass to 50% by mass. If the silica concentration is less than 1% by mass, the production efficiency in steps 1a to 3a decreases, which is not preferred. If the silica concentration exceeds 50% by mass, the stability of the silica fine particles decreases, and for example, aggregated particles are more likely to occur, which is not preferred.
• alkali examples of the alkali to be added in step 1a include alkali silicates such as sodium silicate (water glass) and potassium silicate, alkali metals such as sodium hydroxide, potassium hydroxide and lithium hydroxide, ammonia, and organic alkalis such as organic amines.
• the alkali is usually added as an aqueous alkali solution.
• the alkali concentration of the aqueous alkali solution is not particularly limited, but is usually used in the range of 1 mass % to 50 mass %.
• solvent examples of the solvent added in step 1a as necessary include water, ion-exchanged water, pure water, ultrapure water, a mixed solvent containing water and a water-soluble organic solvent, and a water-soluble organic solvent.
• Step 2a the preparation liquid prepared in step 1a is stirred uniformly, heated, and maintained at a temperature (40° C. or higher and 98° C. or lower) for a certain period of time, and then the following treatments A and B are carried out simultaneously.
• Treatment A A reaction liquid is prepared by continuously or intermittently adding an acidic silicic acid liquid and an alkali to the reaction vessel filled with the prepared liquid.
• Process B A portion of the reaction solution is continuously or intermittently withdrawn from the reaction vessel.
• step 2a the preparation obtained in step 1a is heated to a temperature of 40° C. or more and 98° C. or less while stirring, and is held at the same temperature range for a certain time.
• the holding time is preferably in the range of 20 minutes or more and 120 minutes or less, and more preferably in the range of 30 minutes or more and 90 minutes or less.
• This temperature holding activates the surface of the seed particles, making them suitable for particle growth in the subsequent treatment. In addition, this temperature holding can sufficiently homogenize the preparation.
• the holding time is less than 20 minutes, the surface activation is insufficient, and the particle growth by the subsequent addition of the acidic silicic acid solution is likely to be non-uniform, and self-nucleation by silicic acid may occur.
• the holding time is more than 120 minutes, the surface activity of the seed particles does not progress further, and the holding time becomes longer, which reduces production efficiency and worsens economic efficiency.
• the holding temperature as described above, it is preferable to hold it in the range of 40° C. or more and 98° C. or less, and it is desirable to keep it constant within this temperature range.
• a process A is carried out in which the seed particles are grown to a desired size by adding an acidic silicic acid liquid (here, the addition of an alkali and the addition of an acidic silicic acid liquid for particle growth are carried out simultaneously in order to maintain the pH of the reaction liquid), and a process B is carried out in which a part of the reaction liquid is extracted from the reaction vessel.
• the "prepared liquid” is referred to as the "reaction liquid” after the start of the addition of the acidic silicic acid liquid, because the particle growth reaction of the seed particles progresses due to the addition of the acidic silicic acid liquid.
• the reaction liquid extracted in the above-mentioned treatment B can be mixed with the reaction liquid remaining in the reaction vessel in step 3a to obtain a silica fine particle dispersion liquid having a broader particle size distribution (wider particle size distribution range).
• the acidic silicic acid solution can be obtained by dealkalizing an aqueous solution of alkaline silicate with a cation exchange resin.
• concentration of the acidic silicic acid solution is preferably in the range of 0.1% by mass to 10% by mass, more preferably in the range of 1% by mass to 7% by mass, calculated as SiO2 .
• the pH of the acidic silicic acid solution is preferably in the range of 1 to 3.
• the value of Ma/Ms is preferably in the range of 1 to 20.
• the value of Ma/Ms is more preferably in the range of 2 to 15. If the value of Ma/Ms is less than 1, the growth of silica particles in the silica particle dispersion obtained by the manufacturing method according to this embodiment is slow, and the distribution is not very broad, so that the polishing speed is insufficient even when used as an abrasive.
• the particle size of the silica particles in the silica particle dispersion obtained by the manufacturing method according to this embodiment becomes too large, and when used as an abrasive, scratches may occur significantly at least on the polished substrate, which is undesirable.
• the preparation time becomes very long, and the economic efficiency is deteriorated.
• the temperature of the preparation liquid or reaction liquid when the acidic silicic acid liquid is added to the preparation liquid or reaction liquid is preferably in the range of 40°C to 98°C.
• the temperature of the preparation liquid or reaction liquid is less than 40°C, the added acidic silicic acid liquid is difficult to dissolve, and therefore difficult to deposit on the surface of the seed particles. Therefore, self-nucleation by silicic acid occurs, and the desired size cannot be obtained.
• the temperature of the preparation liquid or reaction liquid is more than 98°C, the added acidic silicic acid liquid is sufficiently dissolved and the seed particles grow, but the temperature of the preparation liquid or reaction liquid is too high, which is problematic in terms of energy efficiency and safety.
• the temperature of the preparation liquid or reaction liquid when the acidic silicic acid liquid is added to the preparation liquid or reaction liquid is more preferably in the range of 50°C to 98°C.
• the addition rate of the acidic silicic acid liquid when it is added to the reaction vessel filled with the preparation liquid is expressed as dry-g [g] of silica in the acidic silicic acid liquid added per minute per mass [g] of silica particles contained in the solution in the reaction vessel.
• [g/min ⁇ g] is used as the unit of the addition rate of the acidic silicic acid liquid to the liquid.
• the "solution" is a convenient name for the liquid filled in the reaction vessel, and before the start of treatment A, the reaction vessel is filled only with the preparation liquid, and as the addition of the acidic silicic acid liquid starts, the particle growth reaction progresses and becomes the reaction liquid.
• the solution includes the preparation liquid or the reaction liquid, and means the liquid present in the reaction vessel.
• the addition rate of the acidic silicic acid liquid to the liquid is preferably in the range of 0.0001 g/min ⁇ g or more and 0.05 g/min ⁇ g or less. Within the above range, the acidic silicic acid liquid added for particle growth is dissolved by the alkali in the preparation liquid and precipitates on the seed particle surface, thereby promoting the particle growth of the seed particles.
• the addition rate of the acidic silicic acid liquid to the liquid is less than 0.0001 g/min ⁇ g, the preparation time becomes too long for practical use, so that the practicality and economic efficiency are reduced. If the addition rate of the acidic silicic acid liquid to the liquid exceeds 0.05 g/min ⁇ g, it is not desirable because the silicic acid may not be precipitated on the particle surface and self-nucleation may proceed.
• the addition rate of the acidic silicic acid liquid to the liquid is more preferably in the range of 0.0005 g/min ⁇ g to 0.02 g/min ⁇ g, and particularly preferably in the range of 0.002 g/min ⁇ g to 0.01 g/min ⁇ g.
• the addition rate of the acidic silicic acid liquid to the liquid can be calculated as the addition rate (S) of the acidic silicic acid liquid (converted to dry silica) per unit mass of dry silica contained in the solution in the reaction vessel using the following formula.
• (S) (addition rate of acidic silicic acid solution per dry silica) [g/min] ⁇ (mass of dry silica in the solution in the reaction vessel) [g]
• the addition rate of the acidic silicic acid solution per dry silica mass changes in two stages, the dry silica mass of the particles in the reaction vessel is calculated using the dry silica mass in the reaction vessel at the end of the first and second stages of addition, respectively.
• the addition rate does not change, it is calculated using the dry silica mass in the reaction vessel at the end of treatment A in step 2a.
• the addition rate of the acidic silicic acid liquid is calculated as described above in terms of the amount of acidic silicic acid liquid added (in terms of dry silica) per unit mass (unit area of seed particle) per unit time, whether the addition of the acidic silicic acid liquid is continuous or intermittent.
• n is a positive integer. That is, it is preferable to change the addition rate of the acidic silicic acid liquid during preparation at least once and gradually reduce the addition rate.
• step 2a in order to grow particles to a desired size, acidic silicic acid liquid is added to grow particles, but in the present invention, the reaction liquid is continuously extracted, so the number of particles decreases. Therefore, the acidic silicic acid liquid may not be deposited on the particle surface, and self-nucleation by silicic acid may occur. By reducing the addition rate of the acidic silicic acid liquid from the second stage onwards, the occurrence of self-nucleation can be prevented and particles can be grown to a desired size.
• Alkali Addition Rate In the treatment A of step 2a, it is desirable to add an alkali continuously or intermittently to the prepared solution simultaneously with the addition of the acidic silicic acid solution in order to maintain the pH of the reaction solution.
• the rate of addition of the alkali depends on the type and concentration of the alkali and cannot be uniformly limited, but it is desirable to add the alkali so that the pH of the reaction solution falls within the range of 8.5 to 13.0.
• step 2a the acidic silicic acid solution is added continuously or intermittently to the solution in the reaction vessel, but the reaction solution (hereinafter also referred to as “extracted solution”) is continuously or intermittently extracted, so that the pH of the reaction solution tends to decrease.
• the reaction solution hereinafter also referred to as "extracted solution”
• the pH of the reaction solution tends to decrease.
• the added acidic silicic acid solution becomes difficult to dissolve, so that self-nucleation by silicic acid tends to occur easily. Therefore, in order to maintain the pH of the solution in the reaction vessel, it is desirable to add an alkali to adjust the pH.
• the SiO 2 /A 2 O molar ratio of the solution in the reaction vessel can be adjusted to a desired pH by adding an alkali so that the SiO 2 /A 2 O molar ratio is in the range of 20 to 160.
• the type of alkali to be added to adjust the SiO 2 /A 2 O molar ratio of the solution in the reaction vessel to 20 or more and 160 or less is not particularly limited, but examples thereof include sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia, and organic amines.
• the pH of the reaction solution adjusted by adding an alkali is preferably in the range of 8.5 to 13.0, more preferably in the range of 9.0 to 12.5. If the pH is more than 13.0, the ionic strength in the reaction solution becomes too high, causing the silica fine particles to aggregate and settle, or the particles to become deformed, making it difficult to obtain the desired particles. If the pH is less than 8.5, the added acidic silicic acid solution becomes difficult to dissolve, so that self-nucleation by silicic acid tends to occur easily.
• an acidic silicic acid solution is continuously or intermittently added to the solution in the reaction vessel while the withdrawn liquid is continuously withdrawn.
• the particle growth reaction has started but the seed particles have not yet grown sufficiently, so small silica fine particles are withdrawn, but in the later stage of the withdrawal, the seed particles have grown sufficiently, so large silica fine particles are withdrawn.
• silica fine particles with a wide particle size distribution are obtained from the withdrawn liquid. It is also preferable to mix the reaction liquid remaining in the reaction vessel with the withdrawn liquid.
• step 2a the withdrawal is performed continuously, but it is preferable to perform the withdrawal under conditions in which the preparation remains in the reaction vessel.
• the remaining preparation is the particle with the largest particle size that has grown the most.
• the shape of the distribution can be adjusted to a distribution shape that has a peak on the small particle side by adjusting the withdrawal speed ratio, and the peak ratio between the small particle side and the large particle side can also be adjusted.
• the distribution shape does not have a peak on the large particle side.
• the production method according to this embodiment is characterized in that, while an acidic silicic acid liquid is added to the reaction liquid to cause particle growth, the reaction liquid is withdrawn in order to broaden the particle size distribution.
• the addition rate [g/min] (calculated as dry silica) of the acidic silicic acid liquid in treatment A of step 2a is X
• the withdrawal rate [g/min] (calculated as dry silica) of the reaction liquid (withdrawn liquid) in treatment B of step 2a is Z
• the withdrawal rate ratio (X/Z) defined by the following formula is preferably in the range of 0.2 to 3.0, more preferably in the range of 0.5 to 2.0, and particularly preferably in the range of 0.6 to 1.8.
• Withdrawal rate ratio (X/Z) (dry silica [g] of acidic silicic acid solution per hour)/(dry silica [g] of withdrawn solution per hour)
• the rate of dry silica added to the reaction vessel is the same as the rate of dry silica withdrawn, so the dry silica in the reaction vessel is constant, and although it depends on the concentration of the raw material, the liquid level in the reaction vessel is generally constant.
• the withdrawal rate ratio is more than 1.0, the amount of withdrawal is small, so the dry silica in the reaction vessel increases, and the liquid level in the reaction vessel usually gradually rises.
• the withdrawal rate ratio is less than 1.0
• the dry silica in the reaction vessel decreases, and the liquid level in the reaction vessel usually gradually drops.
• the withdrawal speed ratio is less than 0.2
• the withdrawal speed is too fast
• the reaction vessel becomes empty or nearly empty in a short reaction time, and the reaction must be terminated, and the particle size distribution is not broad enough.
• the withdrawal speed ratio is more than 3.0
• the addition speed of the acidic silicic acid liquid is too fast, and self-nucleation by the acidic silicic acid liquid is likely to occur.
• the silica dry in the reaction vessel gradually increases, and the level of the prepared liquid usually rises. Therefore, the reaction vessel may overflow. Even if it does not overflow, the size of the reaction vessel needs to be increased, which is not economical.
• step 2a after carrying out treatment A and treatment B, it is preferable to heat-age the remaining reaction liquid.
• the aging temperature is preferably in the range of 40°C to 98°C, more preferably in the range of 60°C to 98°C.
• the aging time is preferably in the range of 20 minutes to 120 minutes, more preferably in the range of 30 minutes to 90 minutes. Such heat-ageing can complete the reaction. If heat-ageing is not carried out, the added acidic silicic acid liquid may remain without being deposited on the particle surface, and the stability of the silica sol may be impaired.
• a base can be added as a pH adjuster, if necessary, in order to adjust the pH of the dispersion to the above range.
• bases include alkali metal hydroxides such as NaOH and KOH, metal carbonates such as potassium oxide, sodium carbonate, and ammonium carbonate, amines such as ammonia, monoethanolamine, and piperazine, and basic nitrogen compounds such as quaternary ammonium hydroxides such as tetramethylammonium.
• step 3a the reaction liquid remaining in the reaction vessel at the end of step 2a is mixed with the reaction liquid extracted in treatment B of step 2a to obtain a dispersion of fine silica particles for polishing.
• the reaction liquid is continuously withdrawn, but it is desirable to withdraw the reaction liquid under conditions in which the reaction liquid remains in the reaction vessel.
• the reaction liquid remaining in the reaction vessel is the particle with the largest particle size that has grown the most. This is because by mixing this reaction liquid with the withdrawn liquid, particles with a wider distribution can be obtained.
• this reaction liquid is mixed with the withdrawn liquid, the particle size distribution becomes a distribution with a peak on the large particle side.
• the shape of the distribution can be adjusted to a distribution shape with a peak on the small particle side by adjusting the withdrawal speed ratio, and the peak ratio between the small particle side and the large particle side can also be adjusted.
• the distribution shape does not have a peak on the large particle side.
• the silica fine particle dispersion for polishing obtained by the first manufacturing method of the silica fine particle dispersion for polishing according to the present embodiment including the steps 1a to 3a may be concentrated to a desired concentration after adjusting the temperature to a range of room temperature to about 50° C.
• the concentration means is not particularly limited, but may be concentrated using an ultrafiltration membrane, a rotary evaporator, or the like. If desired, coarse particles may be removed by centrifugation or a filtration process using a filter, or the like.
• step 1b the acidic silicic acid solution and the alkali are introduced as raw materials into a reaction vessel kept in an unheated state, and a solvent is added as necessary to prepare a first preparation.
• the first preparation is also referred to as a "step 1b solution.”
• the blending time becomes longer and the cost becomes poor.
• a seed particle dispersion liquid and an alkali are added to a heated reaction vessel as in the process of Patent Document 2, the seed particle dispersion liquid and the alkali are heated from the beginning of the addition, which gives rise to a problem that aggregation of the seed particles is likely to occur at an early stage.
• the non-heated state means that no operation for increasing the temperature of the reaction vessel is performed.
• the temperature of the reaction vessel exceeds 40°C in the non-heated state due to seasonal high temperatures, it is recommended to cool the reaction vessel so that the temperature is less than 40°C.
• the temperatures of the acidic silicic acid solution and the alkali when introduced into the reaction vessel are preferably both less than 40°C.
• the acidic silicic acid solution can be obtained by dealkalizing an aqueous solution of alkaline silicate with a cation exchange resin .
• the concentration of the acidic silicic acid solution is preferably in the range of 0.1% by mass to 10% by mass, more preferably in the range of 1% by mass to 7% by mass, and particularly preferably in the range of 2% by mass to 6% by mass, calculated as SiO2.
• the pH of the acidic silicic acid solution is preferably in the range of 1 to 3.
• the amounts of the acidic silicic acid solution and alkali used are added so that the molar ratio of silica to alkali (in terms of oxide) in the first preparation liquid is in the range of 1 to 10, and further adjusted by adding a solvent as necessary so that the silica concentration in the preparation liquid is in the range of 0.1% by mass to 15% by mass.
• the molar ratio of silica to alkali in terms of oxide
• the amount of alkali is excessive, so that the ionic strength in the first preparation liquid becomes excessively high, and the silica fine particles produced in the subsequent steps 2b and 3b aggregate, making it difficult to obtain spherical particles or to generate sediment. Even if sedimentation does not occur, the aggregates of silica fine particles increase, making it difficult to obtain a monodispersed silica sol.
• the molar ratio of silica to alkali oxide equivalent
• the molar ratio of silica to alkali is preferably in the range of 2 to 8, more preferably in the range of 2.5 to 6.
• the silica concentration in the first preparation is less than 0.1% by mass, it is easy to obtain monodispersed silica microparticles, but the silica concentration in the first preparation is low, so that it is not economical to produce efficiently.
• the silica concentration in the first preparation is more preferably in the range of 0.2% by mass to 10% by mass, and particularly preferably in the range of 0.3% by mass to 8% by mass.
• the silica fine particles contained in the silica fine particle dispersion according to this embodiment are mostly spherical particles, but contain irregularly shaped particles in an amount of 1.0% by number to 10% by number.
• alkali examples of the alkali to be added in step 1b include alkali silicates such as sodium silicate (water glass) and potassium silicate, alkali metals such as sodium hydroxide, potassium hydroxide and lithium hydroxide, ammonia, and organic alkalis such as organic amines.
• the alkali is usually added as an aqueous alkali solution.
• the alkali concentration of the aqueous alkali solution is not particularly limited, but is usually in the range of 1 mass% to 50 mass%.
• solvent examples of the solvent added in step 1b as necessary include water, ion-exchanged water, pure water, ultrapure water, a mixed solvent containing water and a water-soluble organic solvent, and a water-soluble organic solvent.
• step 2b the preparation liquid prepared in step 1b is stirred uniformly, heated, and held at a constant temperature (40°C to 98°C) for a certain period of time, and then, while maintaining the same temperature range, an acidic silicic acid liquid is added continuously or intermittently to generate silica fine particles, thereby obtaining a second preparation liquid.
• the second preparation liquid obtained in step 2b is also referred to as "step 2b liquid”.
• step 2b the first preparation prepared in step 1b is heated to a temperature of 40°C to 98°C while stirring, and is maintained at the same temperature range for a certain period of time.
• the holding time is preferably in the range of 10 minutes to 120 minutes, and more preferably in the range of 20 minutes to 90 minutes. This temperature holding can sufficiently homogenize the preparation. If the holding time is less than 10 minutes, homogenization is insufficient, and the generation of silica fine particles and particle growth by the subsequent addition of the acidic silicic acid liquid are likely to be non-uniform. If the holding time is more than 120 minutes, the homogenization of the preparation does not proceed any further, and the longer the holding time, the lower the production efficiency and the worse the economic efficiency.
• silica microparticles are generated by adding an acidic silicic acid liquid while maintaining the temperature of this preparation at 40° C. to 98° C.
• core particles polymers of silicic acid
• the time for adding the acidic silicic acid solution is preferably 3 hours or more and 48 hours or less. If it is less than 3 hours, the rate of adding the acidic silicic acid solution is too fast, and it is easy for self-nucleation by the acidic silicic acid solution to occur in addition to the desired silica fine particles.
• the particle size distribution of the silica fine particles generated in this step 2b shows a normal distribution and is a relatively sharp particle size distribution.
• the amount (total amount) of the acidic silicic acid solution added in step 2b when the molar ratio of SiO2 contained in the second preparation liquid is M2S and the molar ratio of the alkali A contained in the second preparation liquid in terms of oxide (i.e., A2O conversion) is M2A, the value of M2S/M2A is preferably in the range of 20 to 160.
• the value of M2S/M2A is less than 20, the growth of the silica fine particles in the silica fine particle dispersion obtained by the manufacturing method according to this embodiment is slow, and the size is small, so that the polishing speed is insufficient even when used as an abrasive.
• the value of M2S/M2A exceeds 160, the particle size of the silica fine particles in the silica fine particle dispersion obtained by the manufacturing method according to this embodiment becomes too large, and when used as an abrasive, scratches may occur significantly at least on the substrate to be polished, which is undesirable. In addition, in such a case, the preparation time becomes very long, and the economic efficiency is deteriorated.
• the value of M2S/M2A is more preferably in the range of 40 to 140, even more preferably in the range of 50 to 130, and particularly preferably in the range of 60 to 120.
• Step 3b In step 3b, following step 2b, the following process A and process B are carried out simultaneously.
• Treatment A An acidic silicic acid solution and an alkali are added continuously or intermittently to the reaction vessel filled with the second preparation liquid to prepare a reaction liquid.
• Process B A part of the reaction solution in the reaction vessel is continuously or intermittently withdrawn.
• step 3b a process A is carried out to prepare a reaction liquid in which an acidic silicic acid liquid is added to the second preparation liquid filled in the reaction vessel to grow silica microparticles to a desired size (here, an alkali is added to maintain the pH of the reaction liquid and an acidic silicic acid liquid is added simultaneously to grow the particles), and a process B is carried out to extract a portion of the reaction liquid from the reaction vessel.
• an acidic silicic acid liquid is added to the second preparation liquid filled in the reaction vessel to grow silica microparticles to a desired size (here, an alkali is added to maintain the pH of the reaction liquid and an acidic silicic acid liquid is added simultaneously to grow the particles)
• a process B is carried out to extract a portion of the reaction liquid from the reaction vessel.
• the second prepared liquid (Step 2b liquid) is also referred to as the "reaction liquid” or “Step 3b liquid” for convenience after the start of addition of the acidic silicic acid liquid in Step 3b.
• the reaction liquid remaining in the reaction vessel after step 3b is aged at high temperature, and then the reaction liquid extracted in the treatment B is added and mixed to obtain the silica microparticle dispersion for polishing according to this embodiment having a broader particle size distribution (wider particle size distribution range).
• the value of M3S/M3A is in the range of 20 or more and 160 or less. If the value of M3S/M3A is less than 20, the growth of the silica fine particles in the silica fine particle dispersion obtained by the manufacturing method according to this embodiment is slow, and the size becomes small and it is difficult to obtain a broad distribution, so that the polishing speed is insufficient even when used as an abrasive.
• the value of M3S/M3A is more than 160, the particle size of the silica fine particles in the silica fine particle dispersion obtained by the manufacturing method according to this embodiment becomes too large, and when used as an abrasive, at least the occurrence of scratches on the polished substrate may become significant, which is undesirable. In addition, in such a case, the preparation time becomes very long, and the economic efficiency is deteriorated.
• the value of M3S/M3A is more preferably in the range of 40 or more and 140 or less, further preferably in the range of 50 or more and 130 or less, and particularly preferably in the range of 60 or more and 120 or less.
• the temperature of the step 3b liquid when the acidic silicic acid liquid is added to the step 3b liquid is preferably in the range of 40°C to 98°C.
• the temperature of the step 3b liquid is less than 40°C, the added acidic silicic acid liquid is difficult to dissolve, and therefore difficult to deposit on the surface of the silica fine particles. Therefore, self-nucleation by silicic acid occurs, and the desired size cannot be obtained.
• the temperature of the step 3b liquid is more than 98°C, the added acidic silicic acid liquid is sufficiently dissolved and the silica fine particles grow, but the temperature of the silica fine particle dispersion liquid or reaction liquid is excessively high, which is problematic in terms of energy efficiency and safety. It is more preferable that the temperature of the step 3b liquid when the acidic silicic acid liquid is added to the step 3b liquid is in the range of 50°C to 98°C.
• the addition rate of the acidic silicic acid liquid when it is added to the reaction vessel filled with the process 3b liquid is expressed as the dry silica [g] in the acidic silicic acid liquid added per minute per mass [g] of silica particles contained in the solution in the reaction vessel.
• [g/min ⁇ g] is used as the unit of the addition rate of the acidic silicic acid liquid to the liquid.
• the "solution” is a convenient name for the liquid filled in the reaction vessel, and the silica fine particle dispersion liquid filled in the reaction vessel progresses the particle growth reaction with the start of the addition of the acidic silicic acid liquid in the process A and becomes a reaction liquid.
• the solution includes the silica fine particle dispersion liquid or the reaction liquid, and means the liquid present in the reaction vessel.
• the silica component contained in the liquid is also referred to as "silica dry”.
• the addition rate of the acidic silicic acid liquid to the liquid is preferably in the range of 0.0001 g/min ⁇ g or more and 0.05 g/min ⁇ g or less.
• the acidic silicic acid liquid added for particle growth is dissolved by the alkali in the step 3 liquid and precipitates on the surface of the silica fine particles, thereby promoting particle growth of the silica fine particles. If the addition rate of the acidic silicic acid liquid to the liquid is less than 0.0001 g/min ⁇ g, the mixing time becomes too long for practical use, so that practicality and economic efficiency are reduced. If the addition rate of the acidic silicic acid liquid to the liquid exceeds 0.05 g/min ⁇ g, it is undesirable because silicic acid may not be precipitated on the particle surface and self-nucleation may proceed.
• the addition rate of the acidic silicic acid liquid to the liquid is more preferably in the range of 0.0005 g/min ⁇ g to 0.02 g/min ⁇ g, and particularly preferably in the range of 0.001 g/min ⁇ g to 0.01 g/min ⁇ g.
• the addition rate of the acidic silicic acid liquid to the liquid can be calculated by the following formula as the addition rate (S) of the acidic silicic acid liquid (in terms of dry silica) per unit mass of dry silica contained in the solution in the reaction vessel.
• (S) (addition rate of acidic silicic acid solution per dry silica) [g/min] ⁇ (mass of dry silica in the solution in the reaction vessel) [g]
• the addition rate of the acidic silicic acid solution per dry silica mass changes in two stages
• the dry silica mass of the particles in the reaction vessel is calculated using the dry silica mass in the reaction vessel at the end of the first and second stages of addition, respectively.
• the addition rate does not change, it is calculated using the dry silica mass in the reaction vessel at the end of treatment A in step 3b.
• the addition rate of the acidic silicic acid liquid is calculated as described above in terms of the amount of acidic silicic acid liquid added (in terms of dry silica) per unit mass (unit area of silica microparticles) per unit time, whether the addition of the acidic silicic acid liquid is continuous or intermittent.
• n is a positive integer. That is, it is desirable to change the addition rate of the acidic silicic acid liquid during preparation once or more and gradually reduce the addition rate.
• step 3b in order to grow the particles to a desired size, the acidic silicic acid liquid is added to grow the particles, but in the present invention, the reaction liquid is continuously extracted, so the number of particles decreases. Therefore, the acidic silicic acid liquid may not be deposited on the particle surface, and self-nucleation by silicic acid may occur. By reducing the addition rate of the acidic silicic acid liquid from the second stage onwards, the occurrence of self-nucleation can be prevented and the particles can be grown to a desired size.
• step 3b it is desirable to add an alkali continuously or intermittently to the solution of step 3b simultaneously with the addition of the acidic silicic acid solution in order to maintain the pH of the reaction solution.
• the rate of addition of alkali depends on the type and concentration of alkali, so it cannot be uniformly limited, but it is desirable to add it so that the pH of the reaction solution is in the range of 8.5 to 13.0. If the pH of the reaction solution is more than 13.0, the ionic strength in the reaction solution becomes too high, so that the silica fine particles aggregate and settle, or the particles become irregular, so that it is difficult to obtain the desired particles. If the pH is less than 8.5, the added acidic silicic acid solution is difficult to dissolve, so that self-nucleation by silicic acid tends to occur. It is more preferable that the pH of the reaction solution is in the range of 9.0 to 12.5.
• step 3b the acidic silicic acid solution is added continuously or intermittently to the solution in the reaction vessel, while the reaction solution is continuously or intermittently extracted, so that the pH of the reaction solution tends to decrease.
• the pH of the reaction solution tends to decrease.
• the added acidic silicic acid solution becomes difficult to dissolve, so that self-nucleation by silicic acid tends to occur easily. Therefore, in order to maintain the pH of the solution in the reaction vessel, it is desirable to add an alkali to adjust the pH.
• the SiO 2 /A 2 O molar ratio of the solution in the reaction vessel can be adjusted to a desired pH by adding an alkali so that the SiO 2 /A 2 O molar ratio is in the range of 20 to 160.
• the type of alkali to be added to adjust the SiO 2 /A 2 O molar ratio of the solution in the reaction vessel to 20 or more and 160 or less is not particularly limited, but examples thereof include sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia, and organic amines.
• the pH of the reaction solution adjusted by adding an alkali is preferably in the range of 8.5 to 13.0, more preferably in the range of 9.0 to 12.5. If the pH is more than 13.0, the ionic strength in the reaction solution becomes too high, causing the silica fine particles to aggregate and settle, or the particles to become deformed, making it difficult to obtain the desired particles. If the pH is less than 8.5, the added acidic silicic acid solution becomes difficult to dissolve, so that self-nucleation by silicic acid tends to occur easily.
• the acidic silicic acid solution is continuously or intermittently added to the solution in the reaction vessel to generate a reaction solution, and at the same time, a part of the reaction solution is continuously withdrawn.
• the withdrawn reaction solution is also called the "withdrawn liquid".
• the particle growth reaction has started but the silica fine particles have not yet grown sufficiently, so that small silica fine particles are withdrawn, but in the later stage of withdrawal, the silica fine particles have grown sufficiently and so that large silica fine particles (particle diameter) are withdrawn.
• step 3b the withdrawal is performed continuously, but it is preferable to perform the withdrawal under conditions in which the preparation remains in the reaction vessel.
• the remaining preparation is the particle with the largest particle size that has grown the most.
• the shape of the distribution can be adjusted to a distribution shape that has a peak on the small particle side by adjusting the withdrawal speed ratio, and the peak ratio between the small particle side and the large particle side can also be adjusted.
• the distribution shape does not have a peak on the large particle side.
• the inventors performed a tracing experiment, it was found that in a process in which a seed particle dispersion and an acidic silicic acid liquid are continuously added in a reaction vessel equipped with an overflow line, as in the manufacturing method of Patent Document 1, even if the withdrawal speed ratio is adjusted, the particle size distribution does not have a peak on the large particle side as in the present invention.
• the production method according to this embodiment is characterized in that, while an acidic silicic acid liquid is added to the reaction liquid to cause particle growth, the reaction liquid is withdrawn in order to broaden the particle size distribution.
• the addition rate [g/min] (calculated as dry silica) of the acidic silicic acid liquid in the treatment A of step 3b is X
• the withdrawal rate [g/min] (calculated as dry silica) of the reaction liquid (withdrawn liquid) in the treatment B of step 3b is Z
• the withdrawal rate ratio (X/Z) defined by the following formula is preferably in the range of 0.2 or more and 3.0 or less, more preferably in the range of 0.5 or more and 2.0 or less, and particularly preferably in the range of 0.6 or more and 1.8 or less.
• Withdrawal rate ratio (X/Z) (dry silica [g] of acidic silicic acid solution per hour)/(dry silica [g] of withdrawn solution per hour)
• the rate of dry silica added to the reaction vessel is the same as the rate of dry silica withdrawn, so the dry silica in the reaction vessel is constant, and although it depends on the concentration of the raw material, the liquid level in the reaction vessel is generally constant.
• the withdrawal rate ratio is more than 1.0, the amount of withdrawal is small, so the dry silica in the reaction vessel increases, and the liquid level in the reaction vessel usually gradually rises.
• the withdrawal rate ratio is less than 1.0
• the dry silica in the reaction vessel decreases, and the liquid level in the reaction vessel usually gradually drops.
• the withdrawal speed ratio is less than 0.2
• the withdrawal speed is too fast
• the reaction vessel becomes empty or nearly empty in a short reaction time, and the reaction must be terminated, and the particle size distribution is not broad enough.
• the withdrawal speed ratio is more than 3.0
• the addition speed of the acidic silicic acid liquid is too fast, and self-nucleation by the acidic silicic acid liquid is likely to occur.
• the silica dry in the reaction vessel gradually increases, and the level of the prepared liquid usually rises. Therefore, the reaction vessel may overflow. Even if it does not overflow, the size of the reaction vessel needs to be increased, which is not economical.
• a base can be added as a pH adjuster, if necessary, in order to adjust the pH of the dispersion to the above range.
• a basic nitrogen compound such as an alkali metal hydroxide such as NaOH or KOH, a metal carbonate such as potassium oxide, sodium carbonate, or ammonium carbonate, an amine such as ammonia, monoethanolamine, or piperazine, or a quaternary ammonium hydroxide such as tetramethylammonium can be used.
• step 4b the reaction liquid remaining in the reaction vessel at the end of step 3b is heated and aged, and then mixed with the reaction liquid extracted in treatment B of step 3b to obtain a dispersion of fine silica particles for polishing.
• the aging temperature must be in the range of 40°C to 98°C, and more preferably in the range of 60°C to 98°C.
• the aging time must be in the range of 20 minutes to 120 minutes, and more preferably in the range of 30 minutes to 90 minutes. Such heat-ageing can complete the reaction. If heat-ageing is not performed, the added acidic silicic acid liquid may remain without being deposited on the particle surface, and the stability of the silica sol may be impaired.
• the reaction liquid is continuously withdrawn, but it is necessary to withdraw the reaction liquid under conditions in which the reaction liquid remains in the reaction vessel.
• the reaction liquid remaining in the reaction vessel is the particle with the largest particle size that has grown the most. This is because by mixing this reaction liquid with the withdrawn liquid, particles with a wider distribution can be obtained.
• the particle size distribution becomes a distribution with a peak on the large particle side.
• the shape of the distribution can be adjusted to a distribution shape with a peak on the small particle side by adjusting the withdrawal speed ratio, and the peak ratio between the small particle side and the large particle side can also be adjusted.
• the distribution shape does not have a peak on the large particle side.
• the silica fine particle dispersion for polishing obtained by the second manufacturing method of the silica fine particle dispersion for polishing according to the present embodiment including the steps 1b to 4b may be concentrated to a desired concentration after adjusting the temperature to a range of room temperature to about 50° C.
• the concentration means is not particularly limited, and may be concentrated using an ultrafiltration membrane, a rotary evaporator, or the like. If desired, coarse particles may be removed by centrifugation or a filtration process using a filter, or the like.
• SA specific surface area
• SA x specific surface area-equivalent particle diameter
• the specific surface area was calculated from the amount of nitrogen adsorption by the BET single point method using a specific surface area measuring device (manufactured by Yuasa Ionics, model number Multisorb 12) using the nitrogen adsorption method (BET method).
• sample 0.5 g was placed in a measuring cell, and degassed for 20 minutes at 300°C in a mixed gas flow of 30v% nitrogen and 70v% helium, and then the sample was kept at liquid nitrogen temperature in the mixed gas flow to equilibrate and adsorb nitrogen onto the sample.
• sample temperature was gradually raised to room temperature while the mixed gas was being passed, and the amount of nitrogen desorbed during this period was detected, and the specific surface area of the silica fine particles was calculated using a calibration curve created in advance.
• ⁇ Titration method> First, a sample equivalent to 1.5 g of SiO2 was placed in a beaker, 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 performed in the thermostatic reaction tank maintained at 25 °C. Next, 0.1 mol/L hydrochloric acid solution was added thereto so that the pH was 3.6, and then 30 g of sodium chloride was added thereto, and the mixture was diluted with pure water to 150 mL and stirred for 10 minutes. Then, a pH electrode was set, and 0.1 mol/L sodium hydroxide solution was added dropwise while stirring to adjust the pH to 4.0.
• the sample adjusted to pH 4.0 was titrated with 0.1 mol/L sodium hydroxide solution, and the titration amount and pH value in the range of pH 8.7 to 9.3 were recorded at four or more points, and a calibration curve was created by setting the titration amount of 0.1 mol/L sodium hydroxide solution as X and the pH value at that time as Y.
• A is the titration amount (mL) of 0.1 mol/L sodium hydroxide solution required per 1.5 g of SiO2 to change the pH to 4.0 to 9.0
• f is the titer of the 0.1 mol/L sodium hydroxide solution
• C is the SiO2 concentration of the sample (%)
• W is the amount of sample taken (g).
• the specific method of measuring the silica fine particles was to define the maximum diameter of the projected silica fine particle image as the major axis, measure the length of the major axis, and define the value as the major axis.
• a point was determined on the major axis that divided the major axis into two equal parts, and two points were determined where a straight line perpendicular to the major axis intersected with the outer edge of the silica fine particle image, and the distance between the two points was measured as the minor axis to determine the irregularity (minor axis/major axis ratio). From the particle size distribution of the particle group, the average sphericity of the particle group and the rate of irregularly shaped particles (number of irregularly shaped particles/total number of particles ⁇ 100) were calculated.
• Polishing test method ⁇ Polishing of SiO2 film>
• the abrasive grain dispersion liquid obtained in each of the Examples and Comparative Examples was prepared, in which the solid content concentration was 1.0 mass % and the pH was adjusted to 6.0 by adding nitric acid.
• a substrate having a SiO 2 insulating film produced by a deposition method or a thermally oxidized film (both 2 ⁇ m thick) made of SiO 2 produced by a thermal oxidation method was prepared as a substrate to be polished.
• the substrate to be polished was set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), and polishing was performed using a polishing pad ("IC-1000/SUBA400 concentric type" manufactured by Nitta Haas Corporation) by supplying a polishing abrasive dispersion liquid for polishing at a rate of 20 mL/min for 15 minutes under a substrate load of 0.08 MPa, a table rotation speed of 87 rpm, and a polishing head rotation speed of 93 rpm.
• the change in weight of the substrate to be polished before and after polishing was then determined, and the polishing rate was calculated.
• the abrasive grain dispersion liquid obtained in each of the Examples and Comparative Examples was prepared, in which the solid content concentration was 9 mass %, and the pH was adjusted to 2.0 by adding nitric acid.
• An aluminum hard disk substrate was set in a polishing device (NF300, manufactured by Nanofactor Co., Ltd.) and polished using a polishing pad ("Polytex ⁇ 12" manufactured by Nitta Haas Corporation) with a substrate load of 0.05 MPa, a table rotation speed of 30 rpm, and a polishing head rotation speed of 60 rpm, while supplying a polishing abrasive dispersion liquid at a rate of 20 mL/min for 10 minutes.
• Cation titration was carried out as follows to determine V/ SiO2 .
• the cation titration was carried out by dropping 0.08% by mass of polyethyleneimine (molecular weight 600) as a cation titrant into 80 g of a silica particle dispersion adjusted to a solid content concentration of 0.5% by mass.
• the amount of the cation titrant added (mL) was plotted on the x-axis and the streaming potential of the dispersion (mV) on the y-axis, and a potential streaming curve was obtained by plotting the relationship between the amount of the titrant added and the streaming potential.
• V The point (inflection point) where the change in streaming potential with respect to the amount of the drop in the potential flow curve changes significantly is called the knick.
• the amount of cationic solid added (V, g) was calculated from the amount of the cationic colloid titrant dropped at the knick. From these results, V/ SiO2 was calculated.
• Example 1-1 Into a non-heated blending tank (reaction vessel, internal volume 10 L), 4527 g of pure water at a temperature of 25°C was charged, and 413.6 g of a silica microparticle dispersion (Cataloid SI-50 manufactured by JGC Catalysts and Chemicals, SiO2 concentration 48.35 mass%, Na2O concentration 0.49 mass%, specific surface area converted particle diameter 26.2 nm, liquid temperature 25°C) was further added to obtain a diluted silica microparticle dispersion.
• a silica microparticle dispersion Cataloid SI-50 manufactured by JGC Catalysts and Chemicals, SiO2 concentration 48.35 mass%, Na2O concentration 0.49 mass%, specific surface area converted particle diameter 26.2 nm, liquid temperature 25°C
• a potassium hydroxide aqueous solution (KOH concentration 48.7% by mass, Super Kali R manufactured by Toagosei Co., Ltd.) was diluted with pure water to a KOH concentration of 4.8% by mass, and 20.83 g of the potassium hydroxide aqueous solution was added to the diluted silica fine particle dispersion liquid and stirred until it became uniform. After stirring, the mixture was heated to 95° C. and maintained for 30 minutes. Subsequently, 14.198 kg of an acidic silicic acid solution ( SiO2 concentration 4.45% by mass) and 1.475 kg of a potassium hydroxide aqueous solution (KOH concentration 1.0% by mass) were each added over 18 hours.
• the addition rate of the acidic silicic acid liquid ( SiO2 concentration 4.45 mass%, pH 2.7) was 14.40 g/min from the start of addition until 9 hours had elapsed, and 11.90 g/min from 9 hours to 18 hours had elapsed.
• the addition rate of the aqueous potassium hydroxide solution (KOH concentration: 1.0 mass %) was 1.54 g/min from the start of addition until 9 hours had elapsed, and was 1.19 g/min from 9 hours to 18 hours.
• 15.04 kg of a part of the reaction solution (hereinafter also referred to as the "extracted liquid”) was extracted from the blending tank.
• the extraction rate of the extracted liquid was 15.93 g/min from the start of extraction until 9 hours had elapsed, and 11.92 g/min from 9 hours to 18 hours had elapsed.
• 5.59 kg of reaction solution remained in the mixing tank. This solution was kept at 95° C. for 1 hour and then cooled to room temperature.
• the ratio of dry silica in the acidic silicic acid solution during the reaction to dry silica in the withdrawn solution (dry silica in acidic silicic acid solution/dry silica in withdrawn solution) is shown in Table 1.
• the silica solid content is also referred to as "dry silica”.
• the reaction liquid remaining in the mixing tank and the extracted liquid were mixed until uniform.
• the resulting mixed liquid had a pH of 10.2, a specific surface area converted particle diameter of 45.5 nm, and a SiO2 concentration of 4.03 mass%.
• This mixed liquid was concentrated using an ultrafiltration membrane SIP-1013 manufactured by Asahi Kasei Corporation until the SiO2 concentration became 12.0 mass%, to obtain a silica fine particle dispersion for polishing.
• the resulting dispersion of fine silica particles for polishing was evaluated in various ways by the above-mentioned methods, and the results are shown in Table 2.
• the conditions for preparing the dispersion of fine silica particles for polishing in Example 1 are shown in Table 1.
• Examples 1-2 and 1-3 A dispersion of fine silica particles for polishing was obtained in the same manner as in Example 1-1, except that the preparation conditions were changed as shown in Table 1. The obtained dispersion of fine silica particles for polishing was evaluated in the same manner as in Example 1-1. The obtained results are shown in Table 2.
• silica fine particle dispersion was evaluated in the same manner as in Example 1. The results are shown in Table 2. The conditions for preparing the silica fine particle dispersion in Comparative Example 1-1 are shown in Table 1.
• Example 1-2 Cataloid SI-45P (silica fine particle dispersion) manufactured by JGC Catalysts and Chemicals, Ltd. was evaluated in the same manner as in Example 1. The results are shown in Table 2.
• Example 2-1 In a mixing tank having an internal volume of 10 L, 304.66 g of pure water was added, and further, 6.72 g of an aqueous potassium hydroxide solution (KOH having a KOH concentration of 48.7% by mass (Super Kali R manufactured by Toagosei Co., Ltd.)) was added. 160.88 g of an acidic silicic acid solution ( SiO2 concentration of 4.55% by mass) was added and stirred until it became uniform. After stirring, the temperature was raised to 98°C and maintained for 30 minutes. Then, 2.918 kg of acidic silicic acid solution (SiO 2 concentration 4.55 mass%) was added over 11 hours.
• KOH aqueous potassium hydroxide solution
• SiO2 concentration SiO2 concentration of 4.55% by mass
• the addition rate of the acidic silicic acid solution was 4.42 g / min.
• 351.27 g of pure water was added to maintain the temperature at 98 ° C.
• 14.338 kg of acidic silicic acid solution (SiO 2 concentration 4.55 mass%) and 3.046 kg of potassium hydroxide aqueous solution (KOH concentration 0.5 mass%) were added over 24 hours.
• 17.24 kg of the reaction solution was withdrawn from the blending tank in total.
• the acidic silicic acid solution addition rate, 0.5 mass% potassium hydroxide aqueous solution addition rate and withdrawal rate at each elapsed time are shown in Table 3.
• the silica dry addition rate of the acidic silicic acid solution relative to the silica dry at each elapsed time is shown in Table 3.
• 3.50 kg of the reaction solution remained in the mixing tank. This solution was kept at 98° C. for 1 hour and then cooled to room temperature.
• the ratio of dry silica in the acidic silicic acid solution to dry silica in the withdrawn solution dry silica in acidic silicic acid solution/dry silica in withdrawn solution at each time point during preparation is shown in Table 3.
• the reaction liquid remaining in the mixing tank and the reaction liquid removed were mixed until homogeneous.
• the resulting mixture had a pH of 10.1, a specific surface area converted particle diameter of 36.9 nm, and a SiO2 concentration of 3.75 mass%.
• This mixture was concentrated using an ultrafiltration membrane SIP-1013 manufactured by Asahi Kasei Corporation until the SiO2 concentration reached 12.0% concentration, to obtain a silica fine particle dispersion for polishing.
• the resulting dispersion of fine silica particles for polishing was subjected to various evaluations by the above-mentioned methods, and the evaluation results are shown in Table 4.
• Examples 2-2 and 2-3 Except for changing the preparation conditions as shown in Table 3, the same procedure as in Example 2-1 was carried out to obtain a dispersion of fine silica particles for polishing. The obtained dispersion of fine silica particles for polishing was evaluated in the same manner as in Example 2-1. The obtained results are shown in Table 4.
• Comparative Example 2-1 A dispersion of fine silica particles for polishing was obtained in the same manner as in Comparative Example 1-1. The obtained dispersion of fine silica particles for polishing was evaluated in the same manner as in Example 2-1. The obtained results are shown in Table 4.
• Example 2-2 Cataloid SI-45P (silica fine particle dispersion) manufactured by JGC Catalysts and Chemicals, Ltd. was evaluated in the same manner as in Example 2-1. The results are shown in Table 4.
• addition rate of dry silica of acidic silicic acid solution relative to dry silica means the mass [g] of dry silica in the acidic silicic acid solution added per minute per mass [g] of silica particles (dry silica) contained in the solution in the reaction vessel filled with the step 3b solution in treatment A of step 3b.
• end of the first stage means the end of the first addition when the addition rate of the acidic silicic acid liquid is changed multiple times.
• the first addition refers to the 4th hour, the second to the 8th hour, the third to the 12th hour, and so on.
• Example 3-1 to 3-6 are shown below.
• the conditions for preparation of each example are shown in Table 5.
• the obtained dispersion of silica fine particles for polishing was evaluated in the same manner as in Example 1-1.
• the obtained results are shown in Table 6.
• Example 3-1 Into a mixing tank having an internal volume of 10 L, 4408 g of pure water was added, and further 309.7 g of a silica fine particle dispersion liquid (Cataloid SI-50 manufactured by JGC Catalysts and Chemicals, SiO2 concentration 48.43 mass%, Na2O concentration 0.48 mass%, specific surface area converted particle size 25.5 nm) was added.
• a silica fine particle dispersion liquid Cataloid SI-50 manufactured by JGC Catalysts and Chemicals, SiO2 concentration 48.43 mass%, Na2O concentration 0.48 mass%, specific surface area converted particle size 25.5 nm
• the addition rate of the acidic silicic acid solution, the addition rate of the potassium hydroxide aqueous solution (concentration 0.25 mass%) and the withdrawal rate are shown in Table 5.
• 4.55 kg of the preparation liquid remained in the preparation tank, and this solution was held at 98 ° C for 1 hour and cooled to room temperature.
• the ratio of the acidic silicic acid solution silica dry during preparation and the withdrawn solution silica dry is shown in Table 5.
• the preparation liquid remaining in the mixing tank and the extracted preparation liquid were mixed until uniform.
• the resulting mixture had a pH of 10.2, a specific surface area converted particle size of 44.0 nm, and a SiO2 concentration of 3.17% by mass.
• This mixture was concentrated using an ultrafiltration membrane SIP-1013 manufactured by Asahi Kasei Corporation until the SiO2 concentration became 12.0% by mass.
• Example 3-2 In a mixing tank having an internal volume of 10 L, 4381 g of pure water was added, and further 309.7 g of a silica fine particle dispersion liquid (Cataloid SI-50 manufactured by JGC Catalysts and Chemicals, SiO2 concentration 48.43 mass%, Na2O concentration 0.48 mass%, specific surface area converted particle size 25.5 nm) was added.
• a silica fine particle dispersion liquid Cataloid SI-50 manufactured by JGC Catalysts and Chemicals, SiO2 concentration 48.43 mass%, Na2O concentration 0.48 mass%, specific surface area converted particle size 25.5 nm
• the addition rate of the acidic silicic acid solution, the addition rate of the potassium hydroxide aqueous solution (concentration 0.33 mass%) and the withdrawal rate are shown in Table 5.
• 4.68 kg of the preparation liquid remained in the preparation tank, and this solution was held at 98 ° C for 1 hour and cooled to room temperature.
• the ratio of the acidic silicic acid solution silica dry during preparation and the withdrawn solution silica dry is shown in Table 5. The preparation remaining in the mixing tank and the extracted preparation were mixed until uniform.
• the resulting mixture had a pH of 10.3, a specific surface area converted particle size of 47.8 nm, and a SiO2 concentration of 3.17% by mass.
• This mixture was concentrated using an ultrafiltration membrane SIP-1013 manufactured by Asahi Kasei Corporation until the SiO2 concentration became 12.0% by mass.
• Example 3-3 In a 10 L mixing tank, 4371 g of pure water was added, followed by 309.7 g of silica fine particle dispersion (JGC Catalysts and Chemicals' Cataloid SI-50, SiO2 concentration 48.43 mass%, Na2O concentration 0.48 mass%, specific surface area converted particle size 25.5 nm). 16.88 g of a solution of potassium hydroxide aqueous solution (concentration 48.7 mass%, Toagosei's Super Potassium R) diluted to 4.8 mass% with pure water was added, and the mixture was stirred until homogenous. After stirring, the mixture was heated to 98°C and maintained for 30 minutes.
• JGC Catalysts and Chemicals' Cataloid SI-50 SiO2 concentration 48.43 mass%, Na2O concentration 0.48 mass%, specific surface area converted particle size 25.5 nm.
• Example 3-4 In a mixing tank having an internal volume of 10 L, 4381 g of pure water was added, and further 309.7 g of a silica fine particle dispersion liquid (Cataloid SI-50 manufactured by JGC Catalysts and Chemicals, SiO2 concentration 48.43 mass%, Na2O concentration 0.48 mass%, specific surface area converted particle diameter 25.5 nm) was added.
• a silica fine particle dispersion liquid Cataloid SI-50 manufactured by JGC Catalysts and Chemicals, SiO2 concentration 48.43 mass%, Na2O concentration 0.48 mass%, specific surface area converted particle diameter 25.5 nm
• the addition rate of the acidic silicic acid solution, the addition rate of the potassium hydroxide aqueous solution (concentration 0.33 mass%) and the withdrawal rate are shown in Table 5.
• 4.49 kg of the preparation liquid remained in the preparation tank, and this solution was held at 98 ° C for 1 hour and cooled to room temperature.
• the ratio of the acidic silicic acid solution silica dry during preparation and the withdrawn solution silica dry is shown in Table 5.
• the preparation liquid remaining in the mixing tank and the extracted preparation liquid were mixed until uniform.
• the resulting mixture had a pH of 10.3, a specific surface area converted particle size of 47.0 nm, and a SiO2 concentration of 3.17% by mass.
• This mixture was concentrated using an ultrafiltration membrane SIP-1013 manufactured by Asahi Kasei Corporation until the SiO2 concentration became 12.0% by mass.
• Examples 3-5 In a mixing tank having an internal volume of 200 L, 47.12 kg of pure water was added, and 4,350 g of a silica fine particle dispersion (Cataloid SI-50 manufactured by JGC Catalysts and Chemicals, SiO2 concentration 48.39 mass%, Na2O concentration 0.47 mass%, specific surface area converted particle size 26.2 nm) was further added.
• Cataloid SI-50 manufactured by JGC Catalysts and Chemicals SiO2 concentration 48.39 mass%, Na2O concentration 0.47 mass%, specific surface area converted particle size 26.2 nm
• the addition rate of the acidic silicic acid solution, the addition rate of the potassium hydroxide aqueous solution (concentration 1.0 mass%) and the withdrawal rate are shown in Table 5.
• 48.95 kg of the preparation liquid remained in the preparation tank, and this solution was held at 95 ° C for 1 hour and cooled to room temperature.
• the ratio of the acidic silicic acid solution silica dry during preparation and the withdrawn solution silica dry is shown in Table 5. The preparation remaining in the mixing tank and the extracted preparation were mixed until uniform.
• the resulting mixture had a pH of 10.3, a specific surface area converted particle size of 44.7 nm, and a SiO2 concentration of 4.07% by mass.
• This mixture was concentrated using an ultrafiltration membrane SIP-2013 manufactured by Asahi Kasei Corporation until the SiO2 concentration became 12.0% by mass.
• the addition rate of the acidic silicic acid solution, the addition rate of the potassium hydroxide aqueous solution (concentration 0.5 mass%) and the withdrawal rate are shown in Table 5.
• 3.66 kg of the preparation liquid remained in the preparation tank, and this solution was held at 98 ° C for 1 hour and cooled to room temperature.
• the ratio of the acidic silicic acid solution silica dry during preparation and the withdrawn solution silica dry is shown in Table 5. The preparation remaining in the mixing tank and the extracted preparation were mixed until uniform.
• the resulting mixture had a pH of 10.1, a specific surface area converted particle size of 49.6 nm, and a SiO2 concentration of 3.68% by mass.
• This mixture was concentrated using an ultrafiltration membrane SIP-1013 manufactured by Asahi Kasei Corporation until the SiO2 concentration became 12.0% by mass.

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