Colloidal silica and production method of the same

Abstract

To provide colloidal silica with a small amount of fine particles.SOLUTION: Colloidal silica having a fine particle content parameter 2 as defined below of 8.0% or less and an average secondary particle diameter of 20 nm to 69.3 nm is provided. Definition of fine particle content parameter 2: (i) Ultra-pure water having an electrical resistivity of 18.2 MΩ or more is added to a colloidal silica sample to be measured to dilute the same so that the silica concentration after dilution becomes 0.1 mass%. The obtained diluted solution is used as a measurement sample 2. (ii) The particle size distribution of the measurement sample 2 is measured by a particle size distribution measuring device based on a scanning electrical mobility diameter measurement method. (iii) From the measured values of the obtained particle size distribution, the fine particle content parameter 2 of the colloidal silica sample is calculated using the following formula. Fine particle content parameter 2=(total number of detected particles of 15 nm or less)÷(total number of detected particles of all particles)×100 [%]SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to colloidal silica with a low content of fine particles. [Background technology]

[0002] In the CMP (Chemical Mechanical Polishing) process in semiconductor manufacturing, the residue of particles on the polished surface is a frequent problem, which leads to a decrease in yield in semiconductor manufacturing.

[0003] As semiconductors become increasingly miniaturized, there is a demand to further reduce the amount of particles remaining on the polished surface, and this in turn requires a reduction in the amount of particles contained in CMP slurry. are.

[0004] Colloidal silica is used as an abrasive material for CMP slurries. Usually, a small amount of fine particles smaller than the main particles are contained in the polished surface, and these fine particles cause the problem of remaining on the polished surface.

[0005] Conventionally, methods for producing colloidal silica with few fine particles have been disclosed (Patent Documents 1 and 2). Patent Document 1 describes a method for producing colloidal silica with few fine particles in the hydrolysis and condensation reaction of an alkoxysilane or a condensate thereof. From 5 minutes after the reaction started, when the electrical conductivity first reached its maximum, the electrical conductivity By adjusting the reaction conditions so that the value does not change by more than 90%, it is possible to obtain silica sol with few fine particles. Patent Document 2 discloses that in the hydrolysis and condensation reaction of tetraalkoxysilane, It is disclosed that silica sol with few fine particles can be obtained by keeping the change in water concentration in the reaction system within 3 mass % from the start of the hydrolysis reaction and condensation reaction to the end of the reaction.

[0006] Also disclosed are a method of subjecting the produced colloidal silica to solvent substitution treatment by heating and distilling it so that the organic solvent concentration is less than 1% by mass (Patent Document 3), a method of adding a neutral oxidizing agent (Patent Document 4), and a method of reducing fine particles by ultrafiltration using an ultrafiltration membrane (Patent Document 5). Patent Document 3 discloses that colloidal silica in which the number distribution ratio of fine particles having a particle size of 40% or less of the volume average particle size is 10% or less is obtained by distilling off the organic solvent coexisting with colloidal silica so that the concentration of residual organic solvent in the colloidal silica produced by the sol-gel method is less than 1% by mass. Patent Document 4 discloses that a silica sol with a small amount of intermediate products (unreacted substances) is obtained by adding a neutral oxidizing agent (including hydrogen peroxide) to a silica sol produced by the sol-gel method. Patent Document 5 discloses that a tetraalkoxysilane is subjected to a hydrolysis reaction and a condensation reaction to obtain a silica sol with a small amount of intermediate products (unreacted substances). The obtained silica sol is ultrafiltered using an ultrafiltration membrane with a molecular weight cutoff of 5,000 to 80,000. This method discloses that intermediate products are removed.

[0007] Even with these conventional techniques, the requirements of semiconductor CMP processes at advanced technology nodes cannot be fully met. However, no colloidal silica has been obtained in which the amount of fine particles is reduced to a level that satisfies the requirements. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-164351 [Patent Document 2] Japanese Patent Publication No. 2022-109711 [Patent Document 3] International Publication No. WO2016 / 117560A1 [Patent Document 4] Japanese Patent Application Publication No. 2020-75830 [Patent Document 5] Patent Publication No. 2021-116208 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides colloidal silica with few fine particles. [Means for solving the problem]

[0010] As a result of extensive research, the inventors of the present invention have developed a technology that enables the production of colloidal silica with a low content of fine particles by including a specific heat treatment in the colloidal silica production process.

[0011] The present invention encompasses the following colloidal silica and a method for producing the colloidal silica.

[0012] Section 1. A method for producing colloidal silica, comprising: A process in which silica sol, which consists of water and silica particles, is heated at the boiling point of water under normal pressure. A method for producing colloidal silica, comprising:

[0013] Section 2. The pH of the silica sol during the heat treatment is pH 9.0 to pH 10.5, The heat treatment time is 11 hours to 35 hours, The heat treatment is carried out on the silica sol. 3 The stirring power per unit is 0.01kW / m 3 ~0.40kW / m 3 The silica sol is stirred under the conditions of Item 1. A method for producing colloidal silica.

[0014] Section 3. The silica sol is (a) Solution B containing alkoxysilane is added to solution A containing water and an alkali catalyst; (b) A silica sol obtained by hydrolyzing and dehydrating condensation of alkoxysilane contained in said solution B under the condition that the addition rate of alkoxysilane contained in said solution B per 1 kg of said solution A is 0.8 mol / hour / kg to 2.50 mol / hour / kg. Item 3. The method for producing colloidal silica according to Item 1 or 2.

[0015] Section 4. The silica sol is (a) Solution B containing alkoxysilane is added to solution A containing water and an alkali catalyst; (b) A silica sol obtained by hydrolyzing and dehydrating condensation of alkoxysilane under conditions in which the concentration of alkoxysilane contained in the solution B is 60% by mass to 98% by mass. Item 3. The method for producing colloidal silica according to Item 1 or 2.

[0016] Section 5. Colloidal silica, A colloidal silica having a fine particle content parameter 1, defined as follows, of 15.0 or less.

[0017] Definition of fine particle content parameter 1 (i) Colloidal silica is diluted with ultrapure water (hereinafter referred to as "ultrapure water") having an electrical resistivity of 18.2 MΩ or more to a silica concentration of 2% by mass (wt%) (diluted solution).

[0018] (ii) 9.1 g of the diluted solution is transferred to a centrifuge tube (model number: S303922A) manufactured by Eppendorf Himac Technologies Co., Ltd., and centrifuged using a centrifugal rotor S58A and a centrifuge CS100FNX at a centrifuge speed of 50,000 rpm, a centrifuge temperature of 5°C, and a centrifuge time of 60 minutes (all in Eppendorf). (Manufactured by Hu-Himac Technologies Co., Ltd.)

[0019] (iii) After centrifugation, 2 mL of the supernatant was collected from the centrifuge tube, and this 2 mL of the supernatant was mixed with Fuso Ultra-high purity colloidal silica PL-3 manufactured by Gakushu Kogyo Co., Ltd. was diluted 10 times with ultra-pure water to form a silica sol, which was then mixed in the following mass ratio (mixture).

[0020] Supernatant after centrifugation: 10-fold diluted PL-3 solution = 9:1 (mass ratio) (iv) The particle size distribution of the resulting mixture is measured using a particle size distribution measuring device based on scanning electrical mobility diameter measurement.

[0021] (v) The value calculated from the measured particle size distribution using the following formula (1) is defined as the fine particle content parameter 1 of the colloidal silica.

[0022] Equation (1) Fine particle content parameter 1 = (Total number of particles detected of 15 nm or less) ÷ (Total number of particles detected of 25 nm or more) The colloidal silica of the present invention has a low content of fine particles. When CMP is performed using the colloidal silica of the present invention as abrasive grains, the results are comparable to those when conventional colloidal silica is used as abrasive grains. In comparison, the amount of remaining particles on the polished surface is significantly reduced, and the surface roughness of the polished surface can be reduced. [Effects of the Invention]

[0023] The present invention can provide colloidal silica with few fine particles. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be described in detail below.

[0025] The embodiments of the present invention are intended to provide a better understanding of the gist of the invention, and unless otherwise specified, do not limit the content of the invention.

[0026] In this specification, the terms "comprise" and "contain" are concepts that encompass all of "comprise," "consist essentially of," and "consist only of."

[0027] In this specification, when a numerical range is expressed as "A to B," it means "not less than A and not more than B."

[0028] In this specification, the expressions parts, % and the like are generally used.

[0029] In this specification, unless otherwise specified, all parts by mass or % by mass (wt%) are used.

[0030] [1] Method for producing colloidal silica The present invention includes a method for producing colloidal silica.

[0031] The method for producing colloidal silica of the present invention includes a step of heat-treating a silica sol consisting of water and silica particles at the boiling point of water under normal pressure.

[0032] The pH of the silica sol during the heat treatment is preferably pH 9.0 to pH 10.5.

[0033] The heat treatment time is preferably 11 to 35 hours.

[0034] The heat treatment is preferably carried out by heating the silica sol. 3 The stirring power per unit is 0.01kW / m 3 ~0.40kW / m 3 The silica sol is stirred under the conditions described above.

[0035] The silica sol (silica sol consisting of water and silica particles) is preferably (a) Solution B containing alkoxysilane is added to solution A containing water and an alkali catalyst; (b) A silica sol obtained by hydrolyzing and dehydrating condensation of alkoxysilane contained in Solution B under the condition that the addition rate of alkoxysilane contained in Solution B is 0.8 mol / hour / kg to 2.50 mol / hour / kg per 1 kg of Solution A.

[0036] mol / hour / kg is the mass of alkoxysilane added per hour to 1 kg of solution A. The value is converted into the amount of silica.

[0037] The silica sol (silica sol consisting of water and silica particles) is preferably (a) Solution B containing alkoxysilane is added to solution A containing water and an alkali catalyst; (b) A silica sol obtained by hydrolyzing and dehydrating condensation of alkoxysilane under conditions in which the concentration of alkoxysilane contained in the solution B is 60% by mass to 98% by mass.

[0038] The colloidal silica of the present invention has a low content of fine particles. When CMP is performed using the colloidal silica obtained by the production method of the present invention as an abrasive, the amount of fine particles remaining on the polished surface is The amount of the polished surface is significantly reduced, and the surface roughness of the polished surface can be reduced.

[0039] In the method for producing colloidal silica of the present invention, preferably, silica is produced by the alkoxide method. (ii) synthesize particles (particle synthesis), (iii) concentrate the particle concentration by thermal distillation (thermal concentration), and (iv) (1) Substitute the solvent with water by heated distillation (heated water substitution), and (2) Reduce the fine particles by heat treatment (heat treatment). By undergoing this series of operations, colloidal silica with fewer fine particles can be produced.

[0040] (1) Silica particle synthesis process In the method for producing colloidal silica of the present invention, silica particles are preferably obtained by hydrolyzing and dehydrating condensation of alkoxysilane to obtain silica sol (particle synthesis step by the alkoxide method).

[0041] Three-component method (silica particle synthesis method) The synthesis of silica particles is preferably a three-liquid process, comprising water, an alkali catalyst, and an alcohol. Solution B containing alkoxysilane (tetraalkoxysilane) and solution C containing water are added to solution A containing and a condensation reaction to synthesize silica particles. The silica particles are preferably synthesized by a three-liquid method, which provides excellent control of the hydrolysis reaction and the condensation reaction.

[0042] Solution A (three-component method) In the synthesis of silica particles, a three-liquid method is employed, and the water concentration (mass %, wt%) of Solution A is preferably 3 wt% to 25 wt%, more preferably 3 wt% to 23 wt%, even more preferably 3 wt% to 20 wt%, and most preferably 3 wt% to 18 wt%. By adjusting the water concentration of Solution A to preferably 3 wt% to 25 wt%, the solubility of silicic acid produced by the hydrolysis reaction in the reaction solution is excellent.

[0043] In the synthesis of silica particles, a three-liquid method is employed, and the alkali catalyst concentration (mass %, wt%) of solution A is preferably 0.1 wt% to 3.0 wt%, more preferably 0.2 wt% to 2.5 wt%, even more preferably 0.3 wt% to 2.0 wt%, and most preferably 0.5 wt% to 1.6 wt%. By adjusting the alkali catalyst concentration to preferably 0.1 wt % to 3.0 wt %, aggregation of silica particles is suppressed, and the dispersion stability of silica particles in the dispersion liquid is excellent.

[0044] The alkali catalyst is preferably an organic base catalyst containing no metal component, in order to avoid contamination with metal impurities, and more preferably an organic base catalyst containing nitrogen.

[0045] The alkaline catalyst is preferably ammonia.

[0046] The organic base catalyst is preferably ethylenediamine, diethylenetriamine, triethylenetetraamine, urea, monoethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide (TMAH), tetramethylguanidine, 3-ethoxypropylamine (3-EOPA), dipropylamine, triethylamine, or the like.

[0047] Ammonia is preferably used because it has an excellent catalytic action, is highly volatile, and can be easily removed in a subsequent step.

[0048] From the viewpoint of increasing the true specific gravity of the silica particles, it is preferable to select an organic base catalyst with a boiling point of 90°C or higher so that it is less likely to volatilize even when the reaction temperature is increased. Preferably, tetramethylammonium hydroxide, 3-ethoxypropylamine, etc. are used.

[0049] The alkali catalyst may be used alone or in the form of a mixture (blend) of two or more kinds.

[0050] The alcohol is preferably methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, 1,4-butanediol, or the like.

[0051] The alcohol may be used alone or in the form of a mixture (blend) of two or more kinds.

[0052] Solution B (3 liquid method) The silica sol is preferably (a) Solution B containing alkoxysilane is added to solution A containing water and an alkali catalyst; (b) A silica sol obtained by hydrolyzing and dehydrating condensation of alkoxysilane under conditions in which the concentration (mass %, wt %) of alkoxysilane contained in the solution B is 60 mass % to 98 mass %.

[0053] In the synthesis of silica particles, a three-liquid method is employed, and the alkoxysilane concentration of Solution B is preferably 60 wt% to 98 wt%, more preferably 65 wt% to 98 wt%, even more preferably 68 wt% to 98 wt%, and most preferably 70 wt% to 95 wt%. By adjusting the concentration to preferably 60 wt % to 98 wt %, the amount of solvent used can be reduced, resulting in excellent productivity of silica particles.

[0054] The silica sol is preferably (a) Solution B containing alkoxysilane is added to solution A containing water and an alkali catalyst; (b) A silica sol obtained by hydrolyzing and dehydrating condensation of alkoxysilane contained in Solution B under the condition that the addition rate of alkoxysilane contained in Solution B is 0.8 mol / hour / kg to 2.50 mol / hour / kg per 1 kg of Solution A.

[0055] In the synthesis of silica particles, a three-liquid method is employed, and the addition rate (mol / hour / kg) of alkoxysilane in solution B is preferably 0.8 mol / hour / kg to 2.5 mol / hour / kg, more preferably The addition rate of the alkoxysilane in solution B is preferably 1.1 mol / hour / kg to 2.4 mol / hour / kg. Preferably, the reaction time is shortened by adjusting the flow rate to 0.8 mol / hr / kg to 2.5 mol / hr / kg. Excellent productivity.

[0056] mol / hour / kg is the mass of alkoxysilane added per hour to 1 kg of solution A. The value is converted into the amount of silica.

[0057] The alkoxysilane is preferably a tetra C silane such as tetramethoxysilane (TMOS), tetraethoxysilane, or tetraisopropoxysilane. 1-8 An alkoxysilane is used. The alkoxysilane is preferably tetra C 1-4Alkoxysilane is used, and more preferably, tetramethoxysilane (TMOS), tetraethoxysilane, or the like is used.

[0058] The alkoxysilane may be used alone or in the form of a mixture (blend) of two or more kinds.

[0059] The alcohol is preferably methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, 1,4-butanediol, or the like.

[0060] The alcohol may be used alone or in the form of a mixture (blend) of two or more kinds.

[0061] Solution C (3 liquid method) In the synthesis of silica particles, a three-liquid method is employed, and the alkali catalyst concentration (mass %, wt%) of solution C is preferably 0 wt% to 9 wt%, more preferably 0 wt% to 8 wt%, even more preferably 0 wt% to 7 wt%, and most preferably 0 wt% to 6 wt%. By adjusting the content of the hydroxybenzoate to preferably 0 wt % to 9 wt %, the reaction does not proceed excessively slowly, and excellent controllability is achieved.

[0062] The alkaline catalyst is preferably ammonia.

[0063] The organic base catalyst is preferably ethylenediamine, diethylenetriamine, triethylenetetraamine, urea, monoethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide (TMAH), tetramethylguanidine, 3-ethoxypropylamine, dipropylamine, triethylamine, or the like.

[0064] Ammonia is preferably used because it has an excellent catalytic action, is highly volatile, and can be easily removed in a subsequent step.

[0065] From the viewpoint of increasing the true specific gravity of the silica particles, it is preferable to select an organic base catalyst with a boiling point of 90°C or higher so that it is less likely to volatilize even when the reaction temperature is increased. Preferably, tetramethylammonium hydroxide, 3-ethoxypropylamine, etc. are used.

[0066] The alkali catalyst may be used alone or in the form of a mixture (blend) of two or more kinds.

[0067] Hydrolysis and condensation reactions In the synthesis of silica particles, a three-liquid method is used to initiate the hydrolysis and condensation reactions. The maximum concentration of water in the reaction system (mass %, wt%) from the start of the reaction to the end of the reaction is preferably 28 wt% The concentration is preferably 25 wt% or less, more preferably 25 wt% or less, even more preferably 20 wt% or less, and most preferably 18 wt% or less. The maximum water concentration in the reaction system is preferably adjusted to 28 wt% or less. The solubility of alkoxysilane (tetraalkoxysilane, etc.) in the reaction solution is good, and the silane It is possible to suppress the generation of fine particles of silicon dioxide.

[0068] In the synthesis of silica particles, a three-liquid method is used to initiate the hydrolysis and condensation reactions. The change in water concentration (mass %, wt%) in the reaction system from the start to the end of the reaction is preferably 15 wt% or less. The change in water concentration in the reaction system from the start of the hydrolysis reaction and the condensation reaction to the end of the reaction is preferably adjusted to 15 wt% or less, and the amount of water produced by the reaction is preferably 13 wt% or less, more preferably 11 wt% or less, and most preferably 8 wt% or less. The solubility of the resulting silicic acid is maintained, and the generation of fine silica particles can be suppressed.

[0069] In the synthesis of silica particles, a three-liquid method is adopted, and the reaction temperature (°C) is preferably 10°C to 80°C, more preferably 12°C to 70°C, and even more preferably 15°C to 60°C. The most preferred temperature is 18° C. to 55° C. By adjusting the reaction temperature for synthesizing silica particles to preferably 10° C. to 80° C., the reaction does not proceed excessively slowly, and excellent controllability is achieved.

[0070] In the method for producing colloidal silica of the present invention, in addition to a production method in which alkoxysilane is hydrolyzed and dehydration-condensed to obtain a silica sol (a method for synthesizing silica particles by the alkoxide method), a production method in which sodium silicate is ion-exchanged to prepare active silicic acid, and then condenses silicic acid species under basic conditions to obtain a silica sol may also be used.

[0071] (2) Heating concentration process The method for producing colloidal silica of the present invention preferably includes a heat concentration step in which the particle concentration is concentrated by heat distillation. By including the heat concentration step in the method for producing colloidal silica, it is possible to reduce the number of fine silica particles contained in the colloidal silica.

[0072] In the heat concentration step, the Pv value (stirring power per unit volume) is preferably 0.01 kW / m 3 ~0.40kW / m 3 and more preferably 0.01 kW / m 3 ~0.30kW / m 3 and more preferably 0.01 kW / m 3 ~0.20kW / m 3 and most preferably 0.01 kW / m 3 ~0.10kW / m 3 The Pv value of the heat concentration treatment is preferably 0.40 kW / m 3 By adjusting the following, the concentration and temperature of the silica particles can be made uniform and the Pv value can be kept below a certain value, thereby suppressing aggregation of the silica particles.

[0073] The heating and concentration time (minutes, min) in the heating and concentration step is preferably 60 to 600 minutes. By adjusting the heating and concentration time in the heating and concentration step to preferably 60 to 600 minutes, the silica particles can be The fine particles of silica particles can be reduced without significantly changing the average secondary particle size or degree of association.

[0074] (3) Heating water replacement process (production of silica sol consisting of water and silica particles) The colloidal silica to be subjected to the heat treatment is preferably one in which the concentration of silica particles has been concentrated by heat distillation and the solvent has been replaced with water. By performing heat concentration and heated water replacement under the following conditions, the content of fine particles of 15 nm or less can be reduced from the point before the heat treatment. By subjecting colloidal silica with a low content of fine particles obtained by heat concentration and heated water substitution under the conditions above to heat treatment under the above conditions, colloidal silica with an even lower content of fine particles can be obtained.

[0075] The method for producing colloidal silica of the present invention preferably includes a heated water substitution step in which the solvent is substituted with water by heated distillation. By including the heated water substitution step in the method for producing colloidal silica, it is possible to reduce the number of fine silica particles contained in the colloidal silica.

[0076] In the heated water replacement step, the Pv value (stirring power per unit volume) is preferably 0.01 kW / m 3 ~0.40kW / m 3 and more preferably 0.01 kW / m 3 ~0.30kW / m 3 and more preferably , 0.01kW / m 3 ~0.20kW / m 3 and most preferably 0.01 kW / m 3 ~0.10kW / m 3 The Pv value of the heated water replacement treatment is preferably 0.40 kW / m 3 By adjusting the following, the concentration and temperature of the silica sol can be made uniform and the Pv value can be kept below a certain value, thereby suppressing the aggregation of silica particles.

[0077] The heated water replacement time (minutes, min) in the heated water replacement step is preferably 60 to 600 minutes. By adjusting the heated water replacement time in the heated water replacement step to preferably 60 to 600 minutes, The fineness of silica particles can be reduced without significantly changing the average secondary particle size or degree of association of silica particles.

[0078] In the hot water replacement step, the methanol concentration (ppm) after the hot water replacement is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 1,000 ppm or less, and most preferably 500 ppm or less. By adjusting the methanol concentration after the hot water replacement to preferably 10,000 ppm or less, the fineness of the silica particles contained in the colloidal silica can be reduced. It is possible to reduce the number of children.

[0079] (4) Heat Treatment Step (Method for Producing Colloidal Silica) The colloidal silica to be subjected to the heat treatment is preferably one in which the concentration of silica particles has been concentrated by heat distillation and the solvent has been replaced with water. By heat concentration and replacement with heated water, the content of fine silica particles of 15 nm or less can be reduced from the point before the heat treatment. By heat treating the colloidal silica with a low fine silica particle content obtained by heat concentration and replacement with heated water, colloidal silica with an even lower fine particle content can be obtained.

[0080] The method for producing colloidal silica of the present invention includes a step of heat-treating a silica sol composed of water and silica particles at the boiling point of water under normal pressure. In the method for producing colloidal silica of the present invention, the heat treatment can reduce the number of fine silica particles contained in the colloidal silica.

[0081] In the heat treatment step, the heating temperature is the boiling point of water under reflux, which makes it possible to reduce the fineness of the silica particles without significantly changing the average secondary particle size or degree of association of the silica particles.

[0082] In the heat treatment step, heating is performed at atmospheric pressure, which makes it possible to reduce the fineness of the silica particles without significantly changing the average secondary particle size or degree of association of the silica particles.

[0083] The pH of the silica sol during the heat treatment is preferably pH 9.0 to pH 10.5.

[0084] The pH of the silica sol is preferably adjusted to pH 9.0 to pH 10.5 using 3-ethoxypropylamine (3-EOPA), ammonia, ethylenediamine, diethylenetriamine, or the like.

[0085] The minimum pH value of the silica sol during the heat treatment is preferably 9.0 or more, more preferably , 9.2 or more, more preferably 9.4 or more, and most preferably 9.5 or more. The minimum pH value of the silica sol during the heat treatment is preferably adjusted to 9.0 or more, thereby It is possible to reduce the fine particles of silica particles contained in idal silica.

[0086] The maximum pH value of the silica sol during the heat treatment is preferably 10.5 or less, more preferably 10.3 or less, even more preferably 10.1 or less, and most preferably 10.0 or less. By adjusting the maximum pH value of the silica sol during the heat treatment to preferably 10.5 or less, the silica It is possible to suppress the aggregation of silica particles.

[0087] The heat treatment is preferably carried out with 1 ml of silica sol. 3 The stirring power per unit (Pv value) is 0.01kW / m 3 ~0.40kW / m 3 The silica sol is stirred under the conditions described above.

[0088] In the heat treatment step, the Pv value (stirring power per unit volume) is preferably 0.01 kW / m3 ~0.40kW / m 3 and more preferably 0.01 kW / m 3 ~0.30kW / m 3 and more preferably 0.01 kW / m 3 ~0.20kW / m 3 and most preferably 0.01 kW / m 3 ~0.10kW / m 3 The Pv value during the heat treatment is preferably 0.40 kW / m 3 By adjusting the following, the concentration and temperature of the silica sol can be made uniform and the Pv value can be kept below a certain value, thereby suppressing the aggregation of silica particles.

[0089] The heat treatment time is preferably 11 to 35 hours. In the heat treatment step, the heating time (hours) is preferably 11 to 35 hours, more preferably 12 to 30 hours, even more preferably 14 to 28 hours, and most preferably 15 to 25 hours. By adjusting the heat treatment time to preferably 11 to 35 hours, it is possible to reduce the fineness of the silica particles without significantly changing the average secondary particle size or degree of association of the silica particles.

[0090] In the heat treatment step, the concentration (mass %, wt %) of the silica sol during heating is preferably 2 wt % to 50 wt %, more preferably 4 wt % to 45 wt %, and even more preferably 6 wt % to 40 wt %; The most preferred range is 8 wt% to 35 wt%. By adjusting the silica sol concentration during the heat treatment to preferably 2 wt% to 50 wt%, it is possible to reduce the fine particles of the silica particles without significantly changing the average secondary particle size or degree of association of the silica particles.

[0091] [2] Colloidal silica The present invention includes colloidal silica.

[0092] The colloidal silica of the present invention has a fine particle content parameter 1, defined as follows, of 15.0 or less.

[0093] Definition of fine particle content parameter 1 (i) Colloidal silica is diluted with ultrapure water (hereinafter referred to as "ultrapure water") having an electrical resistivity of 18.2 MΩ or more to a silica concentration of 2% by mass (wt%) (diluted solution).

[0094] (ii) 9.1 g of the diluted solution is transferred to a centrifuge tube (model number: S303922A) manufactured by Eppendorf-Himac Technologies Co., Ltd., and centrifuged using a centrifugal rotor S58A and a centrifuge CS100FNX at a rotation speed of 50,000 rpm, a temperature of 5°C, and a centrifugation time of 60 minutes (all manufactured by Eppendorf-Himac Technologies Co., Ltd.).

[0095] (iii) After centrifugation, 2 mL of the supernatant was collected from the centrifuge tube, and this 2 mL of the supernatant was mixed with Fuso Ultra-high purity colloidal silica PL-3 manufactured by Gakushu Kogyo Co., Ltd. was diluted 10 times with ultra-pure water to form a silica sol, which was then mixed in the following mass ratio (mixture).

[0096] Supernatant after centrifugation: 10-fold diluted PL-3 solution = 9:1 (mass ratio)

[0097] (iv) The particle size distribution of the resulting mixture is measured using a particle size distribution measuring device based on scanning electrical mobility diameter measurement.

[0098] (v) The value calculated from the measured particle size distribution using the following formula (1) is defined as the fine particle content parameter 1 of the colloidal silica.

[0099] Equation (1) Fine particle content parameter 1 = (Total number of particles detected of 15 nm or less) ÷ (Total number of particles detected of 25 nm or more) The colloidal silica of the present invention has (i) an average secondary particle diameter of 20 nm to 250 nm, and (ii) a fine particle content parameter 1 of 15.0 or less.

[0100] The colloidal silica of the present invention has a low content of fine particles. When CMP is performed using the colloidal silica obtained by the production method of the present invention as an abrasive, the amount of fine particles remaining on the polished surface is The amount of the polished surface is significantly reduced, and the surface roughness of the polished surface can be reduced.

[0101] The silica concentration (mass %, wt %) of the colloidal silica is preferably 2 wt % to 55 wt %; The silica concentration of the colloidal silica is preferably adjusted to 2 wt% to 55 wt%, and most preferably 3 wt% to 40 wt%. By adjusting the silica concentration of the colloidal silica to 2 wt% to 55 wt%, an excellent polishing rate can be achieved.

[0102] [3] Methods for evaluating the physical properties of colloidal silica In the present invention, the physical properties of silica particles are evaluated as follows.

[0103] (1-1) Measurement method for particle content parameter 1 (i) Add ultrapure water (hereinafter referred to as "ultrapure water") with an electrical resistivity of 18.2 MΩ or more to the colloidal silica sample to be measured, and dilute it to a silica concentration of 2 mass % (wt%) (dilution liquid).

[0104] (ii) 9.1 g of the diluted solution is transferred to a centrifuge tube (model number: S303922A) manufactured by Eppendorf-Himac Technologies Co., Ltd., and centrifuged using a centrifugal rotor S58A and a centrifuge CS100FNX at a rotation speed of 50,000 rpm, a temperature of 5°C, and a centrifugation time of 60 minutes (all manufactured by Eppendorf-Himac Technologies Co., Ltd.).

[0105] (iii) After centrifugation, 2 mL of the supernatant was collected from the centrifuge tube, and this 2 mL of the supernatant was mixed with Fuso Ultra-high purity colloidal silica PL-3 manufactured by Gakushu Kogyo Co., Ltd. is diluted 10 times with ultra-pure water to form a silica sol, which is mixed in the following mass ratio.

[0106] Supernatant after centrifugation: 10-fold diluted PL-3 solution = 9:1 (mass ratio) The resulting mixture was designated as measurement sample 1.

[0107] (iv) The particle size distribution of the measurement sample 1 is measured using a particle size distribution measuring device based on the scanning electrical mobility diameter measurement method. The particle size distribution measuring device based on the scanning electrical mobility diameter measurement method is, for example, Liquid Nanoparticle Sizer System Model 9310 (LNS) manufactured by KANOMAX Co., Ltd., and the following procedure is performed using the LNS. Measurement is carried out under the particle size distribution measurement conditions described in (1-2) above.

[0108] (v) From the obtained particle size distribution measurement values, the colloidal silica sample was calculated using the following formula: Calculate the fine particle content parameter 1.

[0109] Equation (1) Fine particle content parameter 1 = (Total number of particles detected of 15 nm or less) ÷ (Total number of particles detected of 25 nm or more)

[0110] (1-2) Particle size distribution measurement conditions (i) The air used for measurement is compressed air generated by a compressor and passed through an air filter. Purified dry air is used using a filter (manufactured by CKD, FCS500-88-P90).

[0111] (ii) Measurements are carried out for 24 hours or more with ultrapure water and the above dry air supplied to the LNS device. Conduct pre-operation.

[0112] (iii) The inside of the measuring device is washed with ultrapure water. The particle concentration of the ultrapure water is measured under the conditions shown in Table 1. The washing is completed when the total number of detected particles is less than 5.0E+11 (# / mL).

[0113] (iv) Under the measurement conditions shown in Table 1, measurement is performed using LNS Volumetric Standard manufactured by KANOMAX as the standard particle.

[0114] (v) Use ultrapure water to clean the inside of the measuring device. Measure the particle concentration of the ultrapure water under the conditions shown in Table 1. Cleaning is completed when the total number of detected particles is less than 1.0E+11 (# / mL).

[0115] (vi) Measurement sample 1 is measured under the measurement conditions shown in Table 1.

[0116] The colloidal silica has a particle content parameter 1 of 15.0 or less as measured by the above-mentioned measurement method.

[0117] The colloidal silica has a particle content parameter 1 measured by the above-mentioned measuring method of 15.0 or less, preferably 12.0 or less, more preferably 10.0 or less, and even more preferably 8.0 or less. By adjusting the particle content parameter 1 to 15.0 or less, This can reduce the amount of fine particles remaining on the polished surface.

[0118] (2-1) Measurement method for particle content parameter 2 (%) (i) Add ultrapure water with an electrical resistivity of 18.2 MΩ or more (hereinafter referred to as "ultrapure water") to the colloidal silica sample to be measured, and dilute it so that the silica concentration after dilution is 0.1 mass % (wt%). The resulting diluted solution is used as measurement sample 2.

[0119] (ii) The particle size distribution of the measurement sample 2 is measured using a particle size distribution measuring device based on the scanning electrical mobility diameter measurement method. The particle size distribution measuring device based on the scanning electrical mobility diameter measurement method is, for example, the Liquid Nanoparticle Sizer System Model 9310 (LNS) manufactured by KANOMAX Co., Ltd., and the following procedure is performed using the LNS. Measurement is carried out under the particle size distribution measurement conditions described in (2-2) above.

[0120] (iii) From the measured particle size distribution, the colloidal silica sample size is calculated using the following formula: Calculate the particle content parameter 2 of the sample.

[0121] Equation (3) Fine particle content parameter 2 = (Total number of particles detected of 15 nm or less) ÷ (Total number of all particles detected) × 100 [%]

[0122] (2-2) Particle size distribution measurement conditions (i) The air used for measurement is compressed air generated by a compressor and passed through an air filter. Purified dry air is used using a filter (manufactured by CKD, FCS500-88-P90).

[0123] (ii) Measurements are carried out for 24 hours or more with ultrapure water and the above dry air supplied to the LNS device. Conduct pre-operation.

[0124] (iii) The inside of the measuring device is washed with ultrapure water. The particle concentration of the ultrapure water is measured under the conditions shown in Table 1. The washing is completed when the total number of detected particles is less than 5.0E+11 (# / mL).

[0125] (iv) Under the measurement conditions shown in Table 1 (LNS measurement conditions), LNS Vol. Measure the umetric standard.

[0126] (v) Use ultrapure water to clean the inside of the measuring device. Measure the particle concentration of the ultrapure water under the conditions shown in Table 1. Cleaning is completed when the total number of detected particles is less than 1.0E+11 (# / mL).

[0127] (vi) Measurement sample 2 is measured under the measurement conditions shown in Table 1.

[0128] The colloidal silica has a particle content parameter 2 of 8.0% or less as measured by the above-mentioned measurement method.

[0129] The colloidal silica has a particle content parameter 2 measured by the above-mentioned measurement method of 8.0% or less, preferably 7.0% or less, more preferably 6.0% or less, and even more preferably 5.0% or less. By adjusting the particle content parameter 2 to 8.0% or less, the amount of particles remaining on the polished surface can be reduced.

[0130] [Table 1]

[0131] (3) Percentage of fine particles evaluated by SEM (%) (i) A dispersion liquid made by mixing 7.5 mL of methanol, 1.5 mL of water, 1 mL of 0.01M HCl, and 5 μL of 20% colloidal silica is dropped onto a sample stage and allowed to dry. This sample stage is then placed in a scanning electron microscope (SEM). The sample is then scanned and an SEM image is taken.

[0132] (ii) Images of 1,000 silica particles taken with a scanning electron microscope were each approximated to an ellipse using image analysis software (Mitani Shoji Co., Ltd.'s "WinRoof2018"), and the minor axis of the ellipse was measured.

[0133] (iii) In the number frequency distribution of the minor axis of an ellipse obtained by the SEM image analysis described above, particles whose minor axis of an ellipse is 25% or less of the average value are defined as fine particles, and the number ratio of fine particles is calculated.

[0134] The proportion of fine particles in the colloidal silica as evaluated by SEM is preferably 0.1% or less. By adjusting the proportion of fine particles in rhodium silica to 0.1% or less as evaluated by SEM, the polished surface This can reduce the amount of residual particles on the surface.

[0135] (4) Average primary particle diameter (nm) Colloidal silica is pre-dried on a hot plate and then heat-treated at 800°C for 1 hour to prepare a measurement sample. The BET specific surface area is measured using the prepared measurement sample. Silica The true specific gravity is 2.2, and the BET specific surface area (m 2 / g) and convert it to the value of the colloidal silica The average primary particle diameter (nm) of silica particles.

[0136] The average primary particle diameter of the colloidal silica is preferably 5 nm to 130 nm, more preferably 10 nm to 120 nm, even more preferably 12 nm to 110 nm, and most preferably 14 nm to 100 nm. The average primary particle diameter of the colloidal silica is preferably adjusted to 5 nm to 130 nm. By doing so, it is possible to reduce the roughness of the polished surface.

[0137] (5) Average secondary particle diameter (nm) A 0.3% by mass aqueous solution of citric acid is added to the colloidal silica to dilute it to a silica concentration of 1.0% by mass (wt%) (diluted solution).

[0138] The diluted solution is used as a measurement sample, and the average secondary particle diameter of the measurement sample is measured by dynamic light scattering (ELSZ-2000, manufactured by Otsuka Electronics Co., Ltd.).

[0139] The average secondary particle diameter (nm) of the colloidal silica is preferably 20 nm to 250 nm, more preferably The average secondary particle size of the colloidal silica is preferably 24 nm to 200 nm, more preferably 27 nm to 170 nm, and most preferably 30 nm to 140 nm. By adjusting the average secondary particle size of the colloidal silica to preferably 20 nm to 250 nm, the roughness of the polished surface can be reduced.

[0140] (6) Association ratio The association ratio of silica particles in colloidal silica is a value obtained by calculating the average secondary particle size / average primary particle size of silica particles in colloidal silica.

[0141] The association ratio of silica particles in the colloidal silica is preferably 1.0 or more, more preferably Preferably, it is 1.1 or more, more preferably 1.2 or more, and most preferably 1.3 or more. By adjusting the lower limit of the association ratio of colloidal silica to 1.0 or more, The polishing rate is further improved when polishing with a blade.

[0142] The association ratio of colloidal silica is preferably 4.0 or less, more preferably 3.5 or less, even more preferably 3.0 or less, and most preferably 2.9 or less. By adjusting the upper limit of the association ratio of colloidal silica to 4.0 or less, it is possible to use colloidal silica. It is possible to reduce the roughness of the polished surface.

[0143] (7) Silica concentration (mass% (wt%)) Colloidal silica was pre-dried on a hot plate, then heat-treated at 800°C for 1 hour, and the residual amount was calculated.

[0144] The silica concentration of the colloidal silica is preferably 2 wt% to 55 wt%, more preferably 2 wt% to 50 wt%, even more preferably 2 wt% to 45 wt%, and most preferably 3 wt% to 40 wt%. By adjusting the silica concentration of the colloidal silica to 2 wt% to 55 wt%, The polishing rate when polishing silica is further improved.

[0145] (8) Silanol group density (number / nm 2 ) The silanol group density of colloidal silica can be determined by the Sears method. The Sears method was performed with reference to the description in GW Sears, Jr., "Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide," Analytical Chemistry, 28(12), 1981 (1956). For measurement, a 1% by weight (wt%) silica dispersion was used, titrated with a 0.1 mol / L aqueous sodium hydroxide solution, and the silanol group density was calculated using the following formula:

[0146] ρ = (a × f × 6022) ÷ (c × S) In the above formula, ρ: Silanol group density (number / nm 2 ), a: Drop volume (mL) of 0.1 mol / L sodium hydroxide solution at pH 4-9, f: Factor of 0.1 mol / L sodium hydroxide solution, c: Silica particles mass (g), S: BET specific surface area (m 2 / g).

[0147] The silanol group density of the silica particles in the colloidal silica is preferably 1.5 / nm 2 More preferably, 1.6 particles / nm 2 More preferably, it is 1.8 particles / nm 2 or more, and most preferably 2.0 particles / nm 2 The lower limit of the silanol group density is set to 1.5 / nm 2 By making the above adjustments, the occurrence of scratches on the workpiece can be further reduced.

[0148] The silanol group density is preferably 10.0 / nm 2 More preferably, 9.5 particles / nm 2 More preferably, 9.0 particles / nm 2 or less, and most preferably 8.8 particles / nm 2 The upper limit of the silanol group density is 10.0 / nm 2By adjusting the following, the abrasiveness of colloidal silica can be further improved.

[0149] (9) True specific gravity In this specification, the true specific gravity is the value measured after drying colloidal silica on a hot plate at 150°C. After keeping it in a 300°C furnace for 1 hour, it can be measured by the liquid phase substitution method using ethanol.

[0150] The true specific gravity of the silica particles contained in the colloidal silica is preferably 1.0 or more. More preferably, it is 1.2 or more, even more preferably, it is 1.4 or more, and most preferably, it is 1.5 or more. By adjusting the lower limit of the true specific gravity to 1.0 or more, the colloidal silica of the present invention can be obtained. The polishing properties are further improved.

[0151] The true specific gravity is preferably 3.0 or less, more preferably 2.8 or less, even more preferably 2.5 or less, and most preferably 2.3 or less. By adjusting the angle, the occurrence of scratches on the workpiece can be further reduced.

[0152] (10) Metal impurity content (ppm) The content of metal impurities was measured using an atomic absorption spectrometer. The sum of the contents of sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt in the colloidal silica was defined as the content of metal impurities. did.

[0153] The content of metal impurities contained in the colloidal silica is preferably 1 ppm or less. By adjusting the content of metal impurities contained in colloidal silica to 1 ppm or less, it becomes more suitable for use as a CMP slurry.

[0154] (11) Polished surface roughness RMS (nm) Add ultrapure water to colloidal silica to make the silica concentration 3.0% by mass (wt%). The mixture is diluted to prepare a polishing composition.

[0155] The polishing composition was used to polish a 3 cm square silicon wafer with a silicon oxide film formed on its surface. The wafer is polished under the following conditions:

[0156] Polishing machine: Nanofactor Co., Ltd., NF-300CMP Polishing pad: Nitta DuPont, IC1000TMPad Slurry feed rate: 50 mL / min Head rotation speed: 32 rpm Platen rotation speed: 32 rpm Grinding pressure: 4 psi Polishing time: 2 min After polishing, the surface roughness of the polished surface of the wafer is evaluated using an atomic force microscope under the following conditions.

[0157] Atomic force microscope: Shimadzu Corporation SPM-9700HT Cantilever: OLYMPUS MICRO CANTILEVER OMCL-AC240TS-R3 Observation mode: Dynamic Scanning range: 3.0 μm square Scanning speed: 1.00 Hz Number of observation fields: Five fields are observed per polished wafer.

[0158] Surface roughness calculation method: The average value of the root mean square roughness of five fields of view was taken as the polished surface roughness RMS.

[0159] The polished surface roughness RMS (nm) is preferably 3.00 nm or less.

[0160] (12) Number of particles remaining on the polished surface (particles / μm 2 ) Add ultrapure water to colloidal silica to make the silica concentration 3.0% by mass (wt%). The mixture is diluted to prepare a polishing composition.

[0161] The polishing composition was used to polish a 3 cm square silicon wafer with a silicon oxide film formed on its surface. The wafer is polished under the following conditions:

[0162] Polishing machine: Nanofactor Co., Ltd., NF-300CMP Polishing pad: Nitta DuPont, IC1000TMPad Slurry feed rate: 50 mL / min Head rotation speed: 32 rpm Platen rotation speed: 32 rpm Grinding pressure: 4 psi Polishing time: 2 min The polished silicon wafers are cleaned by scrubbing them with a PVA roll brush in the scrubbing section built into the cleaning and drying equipment MAT ZAB-8S1M under the following conditions. To secure the silicon wafer, a jig is used with a frame made of glass epoxy resin and the wafer securing portion made of polyurethane.

[0163] Brush: AION SCL Brush Roller 48 (40 / 26) x 224 mm Scrubbing time: 1 min Brush rotation speed: 200 rpm Spin rotation speed of silicon wafer fixing part: 50 rpm After scrubbing, ultrapure water is allowed to flow over the polished substrate at 750 mL / min for 1 minute, and the substrate is then treated at 1800 rpm for 20 seconds in a spin dryer built into the above equipment.

[0164] After drying, the number of particles remaining on the polished surface of the silicon wafer is measured using an SPM-9700HT manufactured by Shimadzu Corporation.

[0165] Number of particles remaining on the polished surface (particles / μm 2 ) is preferably 3 pieces / μm 2 The following is the result.

[0166] [4] Polishing composition The present invention includes a polishing composition containing the colloidal silica of the present invention.

[0167] The polishing composition is useful for CMP applications.

[0168] The polishing composition contains colloidal silica and may further contain additives such as a diluent, an oxidizing agent, a pH adjuster, an anticorrosive agent, a stabilizer, and a surfactant.

[0169] The content of colloidal silica in the polishing composition (mass %, wt %, silica concentration) is preferably 0.01 wt % to 20 wt %, more preferably 0.1 wt % to 15 wt %, even more preferably 1 wt % to 10 wt %, and particularly preferably 2 wt % to 5 wt %.

[0170] Although the embodiments of the present invention have been described above, the present invention is not limited to these examples and can be embodied in various forms without departing from the spirit and scope of the present invention. [Example]

[0171] The present invention will be specifically explained by showing examples.

[0172] However, the present invention is not limited to the examples.

[0173] [1] Production of colloidal silica (1) Example 1 (with heat treatment) Preparation of heated water-displaced silica sol Solution A was a mixture of 976g of methanol, 97g of water, and 58g of 29% ammonia water. Solution B was a mixture of 190g of methanol and 506g of tetramethoxysilane (TMOS), and solution B was a mixture of 119g of pure water. Solution C (pH = 7.85) was added at a constant rate over 75 minutes.

[0174] In preparing the reaction solution, the temperature of each solution before mixing was kept at 35°C, and the temperature of the reaction solution was adjusted so that it decreased from the initial reaction temperature of 35°C at the start of adding Solution B to Solution A (start of synthesis) to the final reaction temperature of 24.5°C at the end of the addition (end of synthesis). The entire amounts of the solutions B and C were added to the mixture at equal speeds.

[0175] The reaction mixture was heated and concentrated under stirring, and the residue was replaced with heated water. After the replacement with heated water, the methanol concentration was 301 ppm.

[0176] Colloidal silica production (heat treatment) For 100 parts by mass of the silica sol obtained above after the substitution with heated water, 3-ethoxypropyl 0.65 parts by mass of amine (3-EOPA) was added, the pH was adjusted to 9.9, and the silica sol was stirred. The mixture was heated at 100° C. under normal pressure conditions. The point at which the silica sol reached 100° C. was regarded as the start of the heat treatment, and samples were taken every 0.5 hours from the start of the heat treatment to measure the pH.

[0177] 0.5 hours after the start of the heat treatment, the pH had reached 9.6, so 0.2 parts by mass of 3-EOPA was added again. The pH was adjusted to 9.9. The above procedure was repeated every 1.5 hours from the start of the heat treatment to the end of the heat treatment. 2.2 parts by mass of 3-EOPA was added from the start of the heat treatment to the end of the heat treatment.

[0178] The heat treatment was carried out for 16 hours to obtain colloidal silica.

[0179] Measurement of methanol concentration A gas chromatograph (Thermo, FocusGC), an autosampler (Thermo, AS3000, or a device with equivalent or higher performance), and an air compressor (capable of supplying compressed air of 0.4 MPa or higher) were used. A 1 μL sample was drawn into a 10 μL syringe and the syringe was placed in the autosampler. The device was set up and measurements were taken.

[0180] (2) Example 2 (with heat treatment) Preparation of heated water-displaced silica sol Solution A was a mixture of 7.7 g of pure water, 96.8 g of methanol, and 4.5 g of 29% by mass ammonia water. Solution B was a mixture of 100 g of TMOS and 17.7 g of methanol, and Solution C was a mixture of 31.7 g of pure water and 4.7 g of 29% by mass ammonia water. These were added at a constant rate over 217 minutes while maintaining the liquid temperature at 36°C.

[0181] After the addition was completed, the reaction mixture was stirred for an additional 30 minutes while maintaining the temperature at 36°C.

[0182] The reaction mixture was heated and concentrated under stirring, and the residue was replaced with heated water. After the replacement with heated water, the methanol concentration was 212 ppm.

[0183] Colloidal silica production (heat treatment) To 100 parts by mass of the silica sol obtained above after the hot water substitution, 0.6 parts by mass of 3-EOPA was added, the pH was adjusted to 9.8, and the silica sol was stirred and heated at 100°C under normal pressure conditions. The heating treatment started when the silica sol reached 100°C, and samples were taken every 0.5 hours from the start of the heating treatment to measure the pH.

[0184] 0.5 hours after the start of the heat treatment, the pH had reached 9.6, so 0.12 parts by mass of 3-EOPA was added again to adjust the pH to 9.8. The above procedure was repeated every 1.0 hour from the start of the heat treatment to the end of the heat treatment. 2.76 parts by mass of 3-EOPA was added from the start of the heat treatment to the end of the heat treatment.

[0185] The heat treatment was carried out for 23.0 hours to obtain colloidal silica.

[0186] (3) Example 3 (heat-treated, small average particle size) Preparation of heated water-displaced silica sol Solution A was a mixture of 463.1 g of pure water, 104.8 g of 26% by mass ammonia water, and 4255.0 g of methanol. Solution B was a mixture of 3,044.4 g of TMOS and 229.4 g of methanol, and Solution C was a mixture of 643.2 g of pure water and 104.8 g of 26% by mass ammonia water. These were added at a constant rate over 150 minutes while maintaining the liquid temperature at 50°C.

[0187] The reaction mixture was heated and concentrated under stirring, and then substituted with heated water. The methanol concentration after the substituted with heated water was It was 198 ppm.

[0188] Colloidal silica production (heat treatment) 0.65 parts by mass of 3-EOPA was added to 100 parts by mass of the silica sol obtained above after the replacement with heated water. The pH was adjusted to 9.9, and the silica sol was stirred and heated at 100°C under atmospheric pressure. The point when the silica sol reached 100°C was regarded as the start of the heat treatment, and sampling was carried out every 0.5 hours from the start of the heat treatment, and the pH was measured.

[0189] 0.5 hours after the start of the heat treatment, the pH had reached 9.6, so 0.2 parts by mass of 3-EOPA was added again. The pH was adjusted to 9.9. The above procedure was repeated every 1.0 hour from the start of the heat treatment to the end of the heat treatment. 3.2 parts by mass of 3-EOPA was added from the start of the heat treatment to the end of the heat treatment.

[0190] The heat treatment was carried out for 24.5 hours to obtain colloidal silica.

[0191] (4) Example 4 (heat-treated, large average particle size) Preparation of heated water-displaced silica sol Solution A was a mixture of 1,546.6 g of pure water, 340.6 g of 26% by mass ammonia water, and 8,363.2 g of methanol. Solution B was a mixture of 6,088.0 g of TMOS and 350.0 g of methanol, and Solution C was a mixture of 1,186.2 g of pure water and 340.6 g of 26% by mass ammonia water. These were added at a constant rate over 100 minutes while maintaining the liquid temperature at 20°C.

[0192] The reaction mixture was heated and concentrated under stirring, and the residue was replaced with heated water. After the replacement with heated water, the methanol concentration was 196 ppm.

[0193] Colloidal silica production (heat treatment) 0.65 parts by mass of 3-EOPA was added to 100 parts by mass of the silica sol obtained above after the replacement with heated water. The pH was adjusted to 9.9, and the silica sol was stirred and heated at 100°C under atmospheric pressure. The point at which the silica sol reached 100°C was considered to be the start of the heat treatment, and the time from the start of the heat treatment to the start of the heat treatment was 0.25 Sampling was carried out every hour and pH was measured.

[0194] After 0.25 hours had passed since the start of the heat treatment, the pH had reached 9.7, so 0.15 parts by mass of 3-EOPA was added again. The pH was adjusted to 9.9 by adding 3-EOPA. The above procedure was repeated every 1.0 hour from the start of the heat treatment to the end of the heat treatment. 3.0 parts by mass of 3-EOPA was added from the start of the heat treatment to the end of the heat treatment.

[0195] The heat treatment was carried out for 20.0 hours to obtain colloidal silica.

[0196] (5) Example 5 (Example with heat treatment, low silica concentration during heating) Preparation of heated water-displaced silica sol The reaction solution obtained in Example 1 was subjected to replacement with heated water under stirring conditions. The concentration was 387 ppm.

[0197] Colloidal silica production (heat treatment) 0.65 parts by mass of 3-EOPA was added to 100 parts by mass of the silica sol obtained above after the replacement with heated water. The pH was adjusted to 9.9, and the silica sol was stirred and heated at 100°C under atmospheric pressure. The point when the silica sol reached 100°C was regarded as the start of the heat treatment, and sampling was carried out every 0.5 hours from the start of the heat treatment, and the pH was measured.

[0198] 0.5 hours after the start of the heat treatment, the pH had reached 9.6, so 0.2 parts by mass of 3-EOPA was added again. The pH was adjusted to 9.9. The above procedure was repeated every 1.5 hours from the start of the heat treatment to the end of the heat treatment. 2.4 parts by mass of 3-EOPA was added from the start of the heat treatment to the end of the heat treatment.

[0199] The heat treatment was carried out for 18.0 hours to obtain colloidal silica.

[0200] (6) Example 6 (Example with heat treatment and high silica concentration during heating) Preparation of heated water-displaced silica sol The reaction solution obtained in Example 1 was heated and concentrated under stirring conditions, and the mixture was replaced with heated water. The methanol concentration was 184 ppm.

[0201] Colloidal silica production (heat treatment) 0.65 parts by mass of 3-EOPA was added to 100 parts by mass of the silica sol obtained above after the replacement with heated water. The pH was adjusted to 9.9, and the silica sol was stirred and heated at 100°C under atmospheric pressure. The point when the silica sol reached 100°C was regarded as the start of the heat treatment, and sampling was carried out every 0.5 hours from the start of the heat treatment, and the pH was measured.

[0202] After 0.5 hours of heating, the pH had reached 9.6, so 0.2 parts by mass of 3-EOPA was added again to adjust the pH to 9.9. The above procedure was repeated every 1.5 hours from the start of the heating treatment to the end of the heating treatment. Between the start and end of the heat treatment, 2.0 parts by mass of 3-EOPA was added.

[0203] The heat treatment was carried out for 15.5 hours to obtain colloidal silica.

[0204] (7) Comparative Example 1 (without heat treatment) This is an example that simulates conventional technology (Patent Document 1: JP 2020-164351 A, and Patent Document 3: International Publication No. WO2016 / 117560A1).

[0205] Solution A was a mixture of 976 g of methanol, 97 g of water, and 58 g of 29% by mass ammonia water. Solution B was a mixture of 190 g of methanol, 506 g of tetramethoxysilane (TMOS), and 119 g of pure water. Solution C (pH = 7.85) was added at a constant rate over 75 minutes.

[0206] In preparing the reaction solution, the temperature of each solution before mixing was kept at 35°C, and the temperature of the reaction solution was changed from the initial reaction temperature of 35°C at the start of adding solution B to solution A (at the start of synthesis) to 35°C at the end of the addition ( While adjusting the temperature so that the reaction temperature would drop to 24.5°C (the final reaction temperature at the end of synthesis), the entire amounts of the solutions B and C were added to the solution A at a constant rate.

[0207] The reaction solution was heated and concentrated under stirring, and then heated water was substituted to obtain colloidal silica.

[0208] (8) Comparative Example 2 (without heat treatment) This is an example that simulates the prior art (Patent Document 2: JP 2022-109711 A and Patent Document 3). .

[0209] Solution A was prepared by mixing 7.7 g of pure water, 96.8 g of methanol, and 4.5 g of 29% ammonia water. Solution B, which was a mixture of 100 g of tetramethoxysilane and 17.7 g of methanol, and Solution C, which was a mixture of 31.7 g of pure water and 4.7 g of 29% by mass ammonia water, were added at a constant rate over 217 minutes while maintaining the liquid temperature at 36°C.

[0210] After the addition was completed, the reaction mixture was stirred for an additional 30 minutes while maintaining the temperature at 36°C.

[0211] The reaction solution was heated and concentrated under stirring, and then heated water was substituted to obtain colloidal silica.

[0212] (9) Comparative Example 3 (without heat treatment) This is an example that simulates the prior art (Patent Documents 2 and 3, and Patent Document 4: JP 2020-75830 A). do.

[0213] To the colloidal silica obtained in Comparative Example 2, 35% by mass of hydrogen peroxide was added so that the amount of hydrogen peroxide was 0.5 g per 100 g of tetraalkoxysilane converted into silica, thereby obtaining colloidal silica.

[0214] (10) Comparative Example 4 (without heat treatment) This is an example that simulates conventional technology (Patent Documents 2 to 4, and Patent Document 5: JP 2021-116208 A).

[0215] 120 g of the colloidal silica obtained in Comparative Example 3 was filtered through an ultrafiltration membrane (Asahi Kasei Corporation Lab Module AOP-0013) with a molecular weight cutoff of 80,000 in a pencil-type module (PX-02001) manufactured by Asahi Kasei Corporation, L / S Easy-Load Pump Heads for Precision Tubing, Avantor (MFLX07514-10) manufactured by Masterflex, and L / S Analog Modular Drive Replacement Controllers, Avantor (MFLX07559-04) manufactured by Masterflex, and a silicone peroxide (MFLX07559-04) manufactured by Masterflex, for the tube. Ultrafiltration was carried out using a decomposition tube (96400-25) to obtain colloidal silica.

[0216] The amount of liquid that permeated the ultrafiltration membrane was 63.6 g, and the permeability was 53%.

[0217] (11) Comparative Example 5 (Example of long-term ultrafiltration without heat treatment) This is an example that simulates the prior art (Patent Documents 2 to 5).

[0218] 40 g of the colloidal silica obtained in Comparative Example 4 was filtered through an ultrafiltration membrane (Asahi Kasei Corporation's Lab Module AOP-0013) with a molecular weight cutoff of 80,000 in a pencil-type module (Asahi Kasei Corporation's PX-02001). The pump uses Masterflex L / S Easy-Load Pump Heads for Precision Tubing, Avantor (MFLX07514-10), and Masterflex L / S Analog Modular Drive Replacement Controllers, Avantor (MFLX07559-04). The tubing is made of Masterflex silicone permeable material. Ultrafiltration was carried out using a dissolution tube (96400-25) to obtain colloidal silica.

[0219] During the ultrafiltration, ultrapure water was added to the colloidal silica to maintain the liquid amount of the colloidal silica constant.

[0220] The amount of liquid that permeated the ultrafiltration membrane was 220.5 g, and the time required for ultrafiltration was 152 minutes.

[0221] [Table 2]

[0222] [Table 3]

[0223] [2] Evaluation results Examples 1 to 6 are colloidal silicas produced by a colloidal silica production method including a step of heat-treating a silica sol consisting of water and silica particles at the boiling point of water under normal pressure.

[0224] The colloidal silica of Examples 1 to 6 had (i) an average secondary particle diameter of 20 nm to 250 nm, and (ii) a fine particle content parameter 1 of 15.0 or less.

[0225] The colloidal silica of the examples was able to keep the content of fine particles low.

[0226] Comparative Examples 1 to 5 are colloidal silicas produced by a colloidal silica production method that does not include a heat treatment step.

[0227] Comparative Examples 1 to 5 are examples that simulate the prior art.

[0228] Comparative Example 1 is an example that simulates Patent Documents 1 and 3, and is intended to effectively reduce particles of 15 nm or less. It was not possible to reduce it.

[0229] Comparative Example 2 is an example that simulates Patent Documents 2 and 3, and is intended to effectively reduce particles of 15 nm or less. It was not possible to reduce it.

[0230] Comparative Example 3 is an example that simulates Patent Documents 2 to 4, and is effective in reducing fine particles of 15 nm or less. It was not possible.

[0231] Comparative Example 4 is an example that simulates Patent Documents 2 to 5, and is effective in reducing fine particles of 15 nm or less. It was not possible.

[0232] Comparative Example 5 simulates Patent Documents 2 to 5, and ultrafiltration is performed for a long period of time in an attempt to reduce the amount of fine particles. In this example, an increase in the average secondary particle size due to particle aggregation was confirmed.

[0233] [3] Industrial Applicability The method for producing colloidal silica of the present invention includes a step of heat-treating a silica sol consisting of water and silica particles at the boiling point of water under normal pressure.

[0234] The colloidal silica of the present invention has (i) an average secondary particle diameter of 20 nm to 250 nm, and (ii) a fine particle content parameter 1 defined as below of 15.0 or less.

[0235] Definition of fine particle content parameter 1 (i) Colloidal silica is diluted with ultrapure water (hereinafter referred to as "ultrapure water") having an electrical resistivity of 18.2 MΩ or more to a silica concentration of 2% by mass (wt%) (diluted solution).

[0236] (ii) 9.1 g of the diluted solution is transferred to a centrifuge tube (model number: S303922A) manufactured by Eppendorf-Himac Technologies Co., Ltd., and centrifuged using a centrifugal rotor S58A and a centrifuge CS100FNX at a rotation speed of 50,000 rpm, a temperature of 5°C, and a centrifugation time of 60 minutes (all manufactured by Eppendorf-Himac Technologies Co., Ltd.).

[0237] (iii) After centrifugation, 2 mL of the supernatant was collected from the centrifuge tube, and this 2 mL of the supernatant was mixed with Fuso Ultra-high purity colloidal silica PL-3 manufactured by Gakushu Kogyo Co., Ltd. was diluted 10 times with ultra-pure water to form a silica sol, which was then mixed in the following mass ratio (mixture).

[0238] Supernatant after centrifugation: 10-fold diluted PL-3 solution = 9:1 (mass ratio) (iv) The particle size distribution of the resulting mixture is measured using a particle size distribution measuring device based on scanning electrical mobility diameter measurement.

[0239] (v) The value calculated from the measured particle size distribution using the following formula (1) is defined as the fine particle content parameter 1 of the colloidal silica.

[0240] Equation (1) Fine particle content parameter 1 = (Total number of particles detected of 15 nm or less) ÷ (Total number of particles detected of 25 nm or more) The colloidal silica of the present invention has a low content of fine particles.

[0241] When CMP is carried out using the colloidal silica of the present invention as an abrasive, the conventional colloidal silica Compared to when Rica is used as an abrasive, the amount of remaining particles on the polished surface is significantly reduced, and It is possible to reduce the surface roughness of the polished surface.

Claims

1. A method for producing colloidal silica, comprising: A process in which silica sol, which consists of water and silica particles, is heated at the boiling point of water under normal pressure. A method for producing colloidal silica, comprising:

2. The pH of the silica sol during the heat treatment is pH 9.0 to pH 10.5, The heat treatment time is 11 hours to 35 hours, The heat treatment is carried out on the silica sol. 3 The stirring power per unit is 0.01kW / m 3 ~0.40kW / m 3 The silica sol is stirred under the conditions of 2. The method for producing colloidal silica according to claim 1.

3. The silica sol is (a) Solution B containing alkoxysilane is added to solution A containing water and an alkali catalyst, (b) A silica sol obtained by hydrolyzing and dehydrating condensation of alkoxysilane contained in said solution B under the condition that the addition rate of alkoxysilane contained in said solution B per 1 kg of said solution A is 0.8 mol / hour / kg to 2.50 mol / hour / kg.

3. The method for producing colloidal silica according to claim 1 or 2.

4. The silica sol is (a) Solution B containing alkoxysilane is added to solution A containing water and an alkali catalyst, (b) A silica sol obtained by hydrolyzing and dehydrating condensation of alkoxysilane under conditions in which the concentration of alkoxysilane contained in the solution B is 60% by mass to 98% by mass.

3. The method for producing colloidal silica according to claim 1 or 2.

5. Colloidal silica, A colloidal silica having a fine particle content parameter 1, defined as follows, of 15.0 or less. Definition of fine particle content parameter 1 (i) Colloidal silica is diluted with ultrapure water (hereinafter referred to as "ultrapure water") having an electrical resistivity of 18.2 MΩ or more to a silica concentration of 2 mass % (wt%) (diluted solution). (ii) 9.1 g of the diluted solution is transferred to a centrifuge tube (model number: S303922A) manufactured by Eppendorf-Himac Technologies Co., Ltd., and centrifuged using a centrifugal rotor S58A and a centrifuge CS100FNX at a centrifugal speed of 50,000 rpm, a centrifugation temperature of 5°C, and a centrifugation time of 60 minutes (all manufactured by Eppendorf-Himac Technologies Co., Ltd.). (iii) After centrifugation, 2 mL of the supernatant was collected from the centrifuge tube, and this 2 mL of the supernatant was mixed with Fuso Ultra-high purity colloidal silica PL-3 manufactured by Gakushu Kogyo Co., Ltd. was diluted 10 times with ultra-pure water to form a silica sol, which was then mixed in the following mass ratio (mixture). Supernatant after centrifugation: 10-fold diluted solution of PL-3 = 9:1 (mass ratio) (iv) The particle size distribution of the resulting mixture is measured using a particle size distribution measuring device based on scanning electrical mobility diameter measurement. (v) The value calculated from the measured particle size distribution using the following formula (1) is defined as the fine particle content parameter 1 of the colloidal silica. Equation (1) Fine particle content parameter 1 = (Total number of particles detected of 15 nm or less) ÷ (Total number of particles detected of 25 nm or more)

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