Colloidal silica and method for producing same

Abstract

Provided are a colloidal silica having few microparticles, and a method for producing the colloidal silica.

Description

Technical Field

[0001] This invention relates to a colloidal silica with few particles. Background Technology

[0002] In the CMP (Chemical Mechanical Polishing) process of semiconductor manufacturing, the presence of residual particles on the polished surface is a recurring problem. These particles can lead to a decrease in yield during semiconductor manufacturing.

[0003] With the advancement of semiconductor miniaturization, it is necessary to further reduce the amount of particles remaining on the polishing surface. Correspondingly, the amount of particles contained in CMP slurry also needs to be reduced.

[0004] Colloidal silica is used as the abrasive material for CMP slurries. Colloidal silica typically contains trace amounts of particles smaller than the main particles, which contribute to the residue problem on the aforementioned abrasive surfaces.

[0005] Methods for manufacturing colloidal silica with few particulate particles are disclosed in the prior art (Patent Documents 1 and 2). Patent Document 1 discloses that in the hydrolysis and condensation reactions of alkoxysilanes or their condensates, by adjusting the reaction conditions so that the conductivity value does not change by more than 90% from the moment the conductivity first reaches its maximum value after the start of the reaction until the end of the reaction, silica sol with few particulate particles can be obtained. Patent Document 2 discloses that in the hydrolysis and condensation reactions of tetraalkoxysilanes, by keeping the water concentration in the reaction system within 3% by mass from the start of the hydrolysis and condensation reactions to the end of the reactions, silica sol with few particulate particles can be obtained.

[0006] In addition, existing technologies also disclose the following methods: a solvent replacement treatment method that reduces the concentration of organic solvent to less than 1% by mass by heating and distilling the prepared colloidal silica (Patent Document 3); a method of adding a neutral oxidant (Patent Document 4); and a method of using an ultrafiltration membrane to reduce particulates (Patent Document 5). Patent Document 3 discloses a method of removing organic solvents coexisting with colloidal silica by distillation, resulting in a residual organic solvent concentration of less than 1% by mass in the colloidal silica prepared by the sol-gel method, thereby obtaining colloidal silica with a particle size distribution ratio of less than 10% for particles with a particle size of less than 40% of the volume average particle size. Patent Document 4 discloses a method of obtaining a silica sol with less intermediate products (unreacted products) by adding a neutral oxidant (containing hydrogen peroxide) to the silica sol obtained by the sol-gel method. Patent document 5 discloses a method for removing intermediate products by ultrafiltration of silica sol obtained by hydrolysis and condensation of tetraalkoxysilane using an ultrafiltration membrane with a molecular weight cutoff of 5,000 to 80,000.

[0007] Even with these existing technologies, it is still impossible to obtain colloidal silicon dioxide with particle counts that are low enough to meet the requirements of advanced technology node semiconductor CMP processes.

[0008] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2020-164351 Patent Document 2: Japanese Patent Application 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: Japanese Patent Application Publication No. 2021-116208 Summary of the Invention

[0009] The problem that the invention aims to solve This invention provides a colloidal silica with fewer particulates.

[0010] Technical solutions for solving the problem The inventors of this invention have conducted in-depth research and developed a technique for manufacturing colloidal silica with low particle content by including specific heat treatment in the manufacturing process of colloidal silica.

[0011] The present invention includes colloidal silica and a method for manufacturing colloidal silica.

[0012] Item 1. A method for manufacturing colloidal silica, comprising a step of heating a silica sol composed of water and silica particles at atmospheric pressure using the boiling point of water.

[0013] Item 2. A method for manufacturing colloidal silica as described in Item 1 above, wherein, The pH of the silica sol during the above heat treatment was between pH 9.0 and pH 10.5. The above heat treatment time is 11 to 35 hours. In the above heat treatment, when every 1m 3 The stirring power for the silica sol was set to 0.01 kW / m³. 3 ~0.40kW / m 3 Under the conditions specified, the silica sol was stirred.

[0014] Item 3. A method for manufacturing colloidal silica as described in Item 1 or 2 above, wherein, The aforementioned silica sol was obtained through the following method: (a) Adding solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) Under the condition that the addition rate of the alkoxysilane contained in the above solution B relative to 1 kg of the above solution A is set to 0.8 mol / h / kg to 2.50 mol / h / kg, the alkoxysilane is subjected to hydrolysis and dehydration condensation.

[0015] Item 4. A method for manufacturing colloidal silica as described in Item 1 or 2 above, wherein, The aforementioned silica sol was obtained through the following method: (a) Adding solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) Under the condition that the concentration of alkoxysilane contained in the above solution B is set to 60% to 98% by mass, the alkoxysilane is subjected to hydrolysis and dehydration condensation.

[0016] Item 5. A colloidal silica, wherein the particle content parameter 1 defined as described below is 15.0 or less.

[0017] Definition of particle content parameter 1: (i) Add ultrapure water (hereinafter referred to as "ultrapure water") with a resistivity of 18.2 MΩ or higher to colloidal silica to dilute it to achieve a silica concentration of 2% by mass (wt%) (diluent).

[0018] (ii) Take 9.1g of the diluted solution into a centrifuge sedimentation tube (model: S303922A) made by Eppendorf Himac Technologies Co., Ltd., and centrifuge it using a centrifuge 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 made by Eppendorf Himac Technologies Co., Ltd.).

[0019] (iii) After centrifugation, extract 2 mL of supernatant from the centrifuge sedimentation tube, and mix the 2 mL of supernatant after centrifugation with silica sol obtained by diluting the ultra-high purity colloidal silica PL-3 manufactured by Fuso Chemical Industry Co., Ltd. by 10 times with ultrapure water in the following mass ratio (mixture).

[0020] The supernatant after centrifugation is 9 parts by 10 parts by 1 part by 1 (mass ratio) of PL-3 dilution. (iv) The particle size distribution of the obtained mixture was determined by using a particle size distribution measuring device based on the scanning electromobility particle size determination method.

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

[0022] Formula (1): Particle content parameter 1 = (total number of particles below 15nm) ÷ (total number of particles above 25nm).

[0023] The colloidal silica of the present invention contains a low content of particulate matter. When CMP is performed using the colloidal silica of the present invention as abrasive, the amount of residual particulate matter on the polishing surface is significantly reduced compared to the use of conventional colloidal silica as abrasive, and the surface roughness of the polishing surface is also reduced.

[0024] Invention Effects This invention can provide colloidal silica with fewer particles. Detailed Implementation

[0025] The present invention will now be described in detail.

[0026] The embodiments of the present invention are described in order to better understand the key points of the invention, and unless otherwise specified, they do not limit the content of the invention.

[0027] In this invention, the concepts of "comprise" and "containing" include any of the following: "comprise", "consist essentially of", and "consist of".

[0028] In this invention, when the numerical range is represented by "A~B", it means "above A and below B".

[0029] In this invention, portions, percentages, etc. are typically used.

[0030] In this invention, unless otherwise specified, parts by mass or % by mass (wt%) are used to represent mass.

[0031] [1] Method for manufacturing colloidal silica This invention includes a method for manufacturing colloidal silica.

[0032] The method for manufacturing colloidal silica of the present invention includes a step of heating a silica sol composed of water and silica particles at atmospheric pressure using the boiling point of water.

[0033] The pH of the silica sol during heat treatment is preferably between pH 9.0 and pH 10.5.

[0034] The preferred heating time is 11 to 35 hours.

[0035] The preferred heat treatment is to heat every 1m 3 The stirring power for the silica sol was set to 0.01 kW / m³. 3 ~0.40kW / m 3 Under these conditions, the silica sol was stirred.

[0036] Silica sol (a silica sol composed of water and silica particles) is preferably a silica sol obtained by means of the following method.

[0037] (a) Adding solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) Under the condition that the addition rate of the alkoxysilane contained in the above solution B relative to 1 kg of the above solution A is set to 0.8 mol / h / kg to 2.50 mol / h / kg, the alkoxysilane is subjected to hydrolysis and dehydration condensation.

[0038] mol / h / kg represents the amount of silicon dioxide equivalent to the mass of alkoxysilane added to 1 kg of solution A every hour.

[0039] Silica sol (a silica sol composed of water and silica particles) is preferably a silica sol obtained by means of the following method.

[0040] (a) Adding solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) Under the condition that the concentration of alkoxysilane contained in the above solution B is set to 60% to 98% by mass, the alkoxysilane is subjected to hydrolysis and dehydration condensation.

[0041] The colloidal silica of the present invention contains a low content of particulate matter. When CMP is performed using the colloidal silica obtained by the preparation method of the present invention as abrasive, the amount of residual particulate matter on the polishing surface is significantly reduced, and the surface roughness of the polishing surface can also be reduced.

[0042] In the method for manufacturing colloidal silica of the present invention, it is preferable to manufacture colloidal silica with fewer particles by a series of operations including (i) synthesizing silica particles using the alkoxide method (particle synthesis), (ii) concentrating the particle concentration by heating distillation (heat concentration), (iii) replacing the solvent with water by heating distillation (heat water replacement), and (iv) reducing the particles by heating treatment (heat treatment).

[0043] (1) Synthesis process of silica particles In the method for manufacturing colloidal silica of the present invention, silica particles are preferably obtained by hydrolyzing and dehydrating condensation of alkoxysilanes to obtain silica sol (using the particle synthesis step of the alkoxide method).

[0044] Three-liquid method (a method for synthesizing silica particles) The preferred method for synthesizing silica particles is the three-liquid method. This involves adding a solution B containing an alkoxysilane (tetraalkoxysilane) and a solution C containing water to a solution A containing water, an alkaline catalyst, and an alcohol. This causes the alkoxysilane (tetraalkoxysilane) to undergo hydrolysis and condensation reactions, thus synthesizing silica particles. The three-liquid method is preferred for synthesizing silica particles because it offers excellent control over the hydrolysis and condensation reactions.

[0045] Solution A (Three-liquid method) When synthesizing silica particles, a three-liquid method is used. The water concentration (mass%, wt%) of solution A is preferably 3wt% to 25wt%, more preferably 3wt% to 23wt%, further preferably 3wt% to 20wt%, and most preferably 3wt% to 18wt%. By adjusting the water concentration of solution A to preferably 3wt% to 25wt%, the silicic acid generated by the hydrolysis reaction has excellent solubility in the reaction solution.

[0046] In the synthesis of silica particles, a three-liquid method is used. The concentration (mass%, wt%) of the alkaline catalyst in solution A is preferably 0.1wt% to 3.0wt%, more preferably 0.2wt% to 2.5wt%, further preferably 0.3wt% to 2.0wt%, and most preferably 0.5wt% to 1.6wt%. By adjusting the concentration of the alkaline catalyst in solution A to the preferred 0.1wt% to 3.0wt%, the aggregation of silica particles can be suppressed, and the dispersion stability of silica particles in the dispersion is excellent.

[0047] From the perspective of avoiding the introduction of metal impurities, the alkaline catalyst is preferably an organic alkaline catalyst that does not contain metal components, and more preferably a nitrogen-containing organic alkaline catalyst.

[0048] The preferred alkaline catalyst is ammonia.

[0049] The preferred organic base catalysts are ethylenediamine, diethylenetriamine, triethylenetetramine, urea, monoethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide (TMAH), tetramethylguanidine, 3-ethoxypropylamine (3-EOPA), dipropylamine, triethylamine, etc.

[0050] Considering its excellent catalytic effect, high volatility, and ease of removal in subsequent processes, ammonia is preferred.

[0051] From the perspective of increasing the true specific gravity of silica particles, in order to prevent volatilization even when the reaction temperature is increased, it is preferable to select an organic base catalyst with a boiling point of 90°C or higher, such as tetramethylammonium hydroxide or 3-ethoxypropylamine.

[0052] Alkali catalysts can be used alone or in combination (blending) of two or more.

[0053] The preferred alcohols are methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, 1,4-butanediol, etc.

[0054] Alcohols can be used alone or in combination (blending) of two or more.

[0055] Solution B (three-liquid method) The silica sol is preferably obtained by the following method.

[0056] (a) Adding solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) Under the condition that the concentration (mass%, wt%) of alkoxysilane contained in the above solution B is set to 60% to 98% by mass, the alkoxysilane is subjected to hydrolysis and dehydration condensation.

[0057] In the synthesis of silica particles, a three-liquid process is used. The alkoxysilane concentration in solution B is preferably 60wt%–98wt%, more preferably 65wt%–98wt%, further preferably 68wt%–98wt%, and most preferably 70wt%–95wt%. By adjusting the alkoxysilane concentration of solution B to the preferred 60wt%–98wt%, the amount of solvent used can be reduced, resulting in excellent silica particle production efficiency.

[0058] The silica sol is preferably obtained by the following method.

[0059] (a) Adding solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) Under the condition that the addition rate of the alkoxysilane contained in the above solution B relative to 1 kg of the above solution A is set to 0.8 mol / h / kg to 2.50 mol / h / kg, the alkoxysilane is subjected to hydrolysis and dehydration condensation.

[0060] In the synthesis of silica particles, a three-liquid process is employed. The preferred addition rate (mol / h / kg) of alkoxysilane in solution B is 0.8 mol / h / kg to 2.5 mol / h / kg, more preferably 1.1 mol / h / kg to 2.4 mol / h / kg. By adjusting the addition rate of alkoxysilane in solution B to the preferred 0.8 mol / h / kg to 2.5 mol / h / kg, the reaction time is shortened and the productivity is excellent.

[0061] mol / h / kg represents the amount of silicon dioxide equivalent to the mass of alkoxysilane added to 1 kg of solution A every hour.

[0062] Alkoxysilanes are preferably tetramethoxysilane (TMOS), tetraethoxysilane, tetraisopropoxysilane, etc., which are tetracarbonyl groups. 1-8 Alkoxysilanes. Alkoxysilanes are more preferably tetracarbon-based. 1-4 Alkoxysilanes are preferred, with tetramethoxysilane (TMOS) and tetraethoxysilane being further preferred.

[0063] Alkoxysilanes can be used alone or in combination (blending) of two or more.

[0064] The preferred alcohols are methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, 1,4-butanediol, etc.

[0065] Alcohols can be used alone or in combination (blending) of two or more.

[0066] Solution C (three-liquid method) In the synthesis of silica particles, a three-liquid method is used. The concentration (mass%, wt%) of the alkaline catalyst in solution C is preferably 0wt% to 9wt%, more preferably 0wt% to 8wt%, further preferably 0wt% to 7wt%, and most preferably 0wt% to 6wt%. By adjusting the concentration of the alkaline catalyst in solution C to the preferred 0wt% to 9wt%, the reaction does not become too slow and has excellent controllability.

[0067] The preferred alkaline catalyst is ammonia.

[0068] The preferred organic base catalysts are ethylenediamine, diethylenetriamine, triethylenetetramine, urea, monoethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide (TMAH), tetramethylguanidine, 3-ethoxypropylamine, dipropylamine, triethylamine, etc.

[0069] Considering its excellent catalytic effect, high volatility, and ease of removal in subsequent processes, ammonia is preferred.

[0070] From the perspective of increasing the true specific gravity of silica particles, in order to prevent volatilization even when the reaction temperature is increased, it is preferable to select an organic base catalyst with a boiling point of 90°C or higher, such as tetramethylammonium hydroxide or 3-ethoxypropylamine.

[0071] Alkali catalysts can be used alone or in combination (blending) of two or more.

[0072] Hydrolysis and condensation reactions In the synthesis of silica particles, a three-liquid method is employed. The maximum water concentration (mass%, wt%) in the reaction system from the start of the hydrolysis and condensation reactions to the end of the reactions is preferably 28 wt% or less, more preferably 25 wt% or less, further preferably 20 wt% or less, and most preferably 18 wt% or less. By adjusting the maximum water concentration in the reaction system from the start of the hydrolysis and condensation reactions to preferably 28 wt% or less, the alkoxysilanes (tetraalkoxysilanes, etc.) exhibit good solubility in the reaction solution, thus suppressing the formation of silica particles.

[0073] In the synthesis of silica particles, a three-liquid method is employed. The change in water concentration (mass%, wt%) within the reaction system from the start of the hydrolysis and condensation reactions to the end of the reactions is preferably 15 wt% or less, more preferably 13 wt% or less, further preferably 11 wt% or less, and most preferably 8 wt% or less. By adjusting the change in water concentration within the reaction system to preferably 15 wt% or less from the start of the hydrolysis and condensation reactions to the end of the reactions, the solubility of the silicic acid generated by the reactions can be ensured, and the formation of silica particles can be suppressed.

[0074] The three-liquid process is used to synthesize silica particles, and the reaction temperature (°C) is preferably 10°C to 80°C, more preferably 12°C to 70°C, further preferably 15°C to 60°C, and most preferably 18°C ​​to 55°C. By adjusting the reaction temperature for synthesizing silica particles to the preferred 10°C to 80°C, the reaction does not become too slow and has excellent controllability.

[0075] In the method for manufacturing colloidal silica of the present invention, in addition to the method of obtaining silica sol by hydrolyzing and dehydrating condensation of alkoxysilane (the method of synthesizing silica particles by alkoxide method), an alternative method can be adopted to prepare active silicic acid by ion exchange of sodium silicate, and then to obtain silica sol by condensation of silicic acid under alkaline conditions.

[0076] (2) Heating and concentration process In the method for manufacturing colloidal silica of the present invention, a heating concentration step is preferably included, in which the particle concentration is concentrated by heating distillation. By including the heating concentration step in the method for manufacturing colloidal silica, the particle size of the silica particles contained in the colloidal silica can be reduced.

[0077] In the heating and concentration process, the Pv value (stirring power per unit volume) is preferably 0.01 kW / m³. 3 ~0.40kW / m 3 More preferably 0.01kW / m 3 ~0.30kW / m3 A further preferred value is 0.01 kW / m³. 3 ~0.20kW / m 3 The optimal value is 0.01 kW / m 3 ~0.10kW / m 3 By adjusting the Pv value of the heat concentration treatment to a preferred 0.40 kW / m³ 3 The following methods can homogenize the concentration and temperature of silica particles, keeping the Pv value below a certain value, thereby suppressing the aggregation of silica particles.

[0078] The heating and concentration time (in minutes) of the heating and concentration process is preferably 60 to 600 minutes. By adjusting the heating and concentration time of the heating and concentration process to the preferred 60 to 600 minutes, the average secondary particle size and degree of association of silica particles will not change significantly, and the particle size of silica particles can be reduced.

[0079] (3) Heating water replacement process (manufacturing of silica sol composed of water and silica particles) Colloidal silica for heat treatment is preferably colloidal silica obtained by concentrating the concentration of silica particles through thermal distillation and replacing the solvent with water. By performing heat concentration and water replacement under the following conditions, the content of particles smaller than 15 nm can be reduced from the moment before heat treatment. Colloidal silica with low particle content obtained by heat concentration and water replacement under the following conditions can be further heat-treated to obtain colloidal silica with a further reduced particle content.

[0080] In the method for manufacturing colloidal silica of the present invention, a heating water displacement step is preferably included, in which the solvent is replaced with water by heating and distillation. By including the heating water displacement step in the method for manufacturing colloidal silica, the particle size of the silica particles contained in the colloidal silica can be reduced.

[0081] In the heating water replacement process, the Pv value (stirring power per unit volume) is preferably 0.01 kW / m³. 3 ~0.40kW / m 3 More preferably 0.01kW / m 3 ~0.30kW / m 3 A further preferred value is 0.01 kW / m³. 3 ~0.20kW / m 3 The optimal value is 0.01 kW / m 3 ~0.10kW / m 3 The Pv value of the heated water replacement treatment was adjusted to an optimal 0.40 kW / m³. 3The following methods can homogenize the concentration and temperature of silica sol, keeping the Pv value below a certain level, thereby suppressing the aggregation of silica particles.

[0082] The preferred heating water replacement time (in minutes) for the heating water replacement process is 60 to 600 minutes. By adjusting the heating water replacement time to the preferred 60 to 600 minutes, the average secondary particle size and degree of association of silica particles will not change significantly, thus reducing the particle size of silica particles.

[0083] In the heated water replacement process, the methanol concentration (ppm) after heated water replacement is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, further preferably 1,000 ppm or less, and most preferably 500 ppm or less. By adjusting the methanol concentration after heated water replacement to preferably 10,000 ppm or less, the particulate matter of silica particles contained in colloidal silica can be reduced.

[0084] (4) Heat treatment process (method for manufacturing colloidal silica) Colloidal silica for heat treatment is preferably colloidal silica obtained by concentrating the concentration of silica particles through heating distillation, thereby replacing the solvent with water. By performing heating concentration and water replacement, the content of silica particles smaller than 15 nm can be reduced from the moment before heat treatment. By heat treating colloidal silica with a low particle content obtained through heating concentration and water replacement, colloidal silica with a further reduced particle content can be obtained.

[0085] The method for manufacturing colloidal silica of the present invention includes a step of heating a silica sol composed of water and silica particles at atmospheric pressure using the boiling point of water. In the method for manufacturing colloidal silica of the present invention, the particle size of the silica particles contained in the colloidal silica can be reduced by performing the heating treatment.

[0086] In the heat treatment process, the heating temperature is the boiling point of water, and the process involves reflux heating. By reflux heating at the boiling point of water, the average secondary particle size and degree of association of the silica particles do not change significantly, thus reducing the particle size of the silica particles.

[0087] In the heat treatment process, the heating pressure is maintained at atmospheric pressure. By maintaining atmospheric pressure during the process, the average secondary particle size and degree of association of the silica particles do not change significantly, thus reducing the particle size of the silica particles.

[0088] The preferred pH of the silica sol during heat treatment is pH 9.0 to pH 10.5.

[0089] Regarding the pH of silica sol, it is preferable to adjust it to pH 9.0–10.5 using 3-ethoxypropylamine (3-EOPA), ammonia, ethylenediamine, diethylenetriamine, etc.

[0090] The minimum pH value of the silica sol during heat treatment is preferably 9.0 or higher, more preferably 9.2 or higher, further preferably 9.4 or higher, and most preferably 9.5 or higher. By adjusting the minimum pH value of the silica sol during heat treatment to preferably 9.0 or higher, the particulate matter of silica particles contained in colloidal silica can be reduced.

[0091] The maximum pH value of the silica sol during heat treatment is preferably 10.5 or less, more preferably 10.3 or less, further preferably 10.1 or less, and most preferably 10.0 or less. By adjusting the maximum pH value of the silica sol during heat treatment to preferably 10.5 or less, the aggregation of silica particles can be suppressed.

[0092] In heat treatment, it is preferable to heat every 1m 3 The stirring power (Pv value) for the silica sol was set to 0.01 kW / m³. 3 ~0.40kW / m 3 Under these conditions, the silica sol was stirred.

[0093] In the heat treatment process, the Pv value (stirring power per unit volume) is preferably 0.01 kW / m³. 3 ~0.40kW / m 3 More preferably 0.01kW / m 3 ~0.30kW / m 3 A further preferred value is 0.01 kW / m³. 3 ~0.20kW / m 3 The optimal value is 0.01 kW / m 3 ~0.10kW / m 3 By adjusting the Pv value during heat treatment to a preferred 0.40 kW / m³. 3 The following methods can homogenize the concentration and temperature of silica sol, keeping the Pv value below a certain level, thereby suppressing the aggregation of silica particles.

[0094] The heat treatment time is preferably 11 to 35 hours. In the heat treatment process, the heating time (hours, hr) is preferably 11 to 35 hours, more preferably 12 to 30 hours, further preferably 14 to 28 hours, and most preferably 15 to 25 hours. By adjusting the heat treatment time to the preferred 11 to 35 hours, the average secondary particle size and association degree of the silica particles do not change significantly, thus reducing the particle size of the silica particles.

[0095] In the heat treatment process, the concentration (mass%, wt%) of the silica sol during heating is preferably 2wt% to 50wt%, more preferably 4wt% to 45wt%, further preferably 6wt% to 40wt%, and most preferably 8wt% to 35wt%. By adjusting the concentration of the silica sol during heat treatment to preferably 2wt% to 50wt%, the average secondary particle size and degree of association of the silica particles do not change significantly, and the particle size of the silica particles can be reduced.

[0096] [2] Colloidal silica This invention includes colloidal silicon dioxide.

[0097] The particle content parameter 1 of the colloidal silica of the present invention, as defined below, is 15.0 or less.

[0098] Definition of particulate content parameter 1 (i) Add ultrapure water (hereinafter referred to as "ultrapure water") with a resistivity of 18.2 MΩ or higher to colloidal silica to dilute it to achieve a silica concentration of 2% by mass (wt%) (diluent).

[0099] (ii) Take 9.1g of the diluted solution into a centrifuge sedimentation tube (model: S303922A) made by Eppendorf Himac Technologies Co., Ltd., and centrifuge it using a centrifuge 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 made by Eppendorf Himac Technologies Co., Ltd.).

[0100] (iii) After centrifugation, extract 2 mL of supernatant from the centrifuge sedimentation tube, and mix the 2 mL of supernatant after centrifugation with silica sol obtained by diluting the ultra-high purity colloidal silica PL-3 manufactured by Fuso Chemical Industry Co., Ltd. by 10 times with ultrapure water in the following mass ratio (mixture).

[0101] The supernatant after centrifugation is 9 parts by 10 parts by 1 part by 1 (mass ratio) of PL-3 dilution. (iv) The particle size distribution of the obtained mixture was determined by using a particle size distribution measuring device based on the scanning electromobility particle size determination method.

[0102] (v) The value calculated using the following formula (1) based on the obtained particle size distribution is defined as the particle content parameter 1 of colloidal silica.

[0103] Formula (1): Particle content parameter 1 = (Total number of particles below 15nm detected) ÷ (Total number of particles above 25nm detected) The colloidal silica of the present invention satisfies (i) an average secondary particle size of 20 nm to 250 nm and (ii) a particle content parameter 1 of 15.0 or less.

[0104] The colloidal silica of the present invention contains a low content of particulate matter. When CMP is performed using the colloidal silica obtained by the manufacturing method of the present invention as abrasive, the amount of residual particulate matter on the polishing surface is significantly reduced, and the surface roughness of the polishing surface can be reduced.

[0105] The silica concentration (mass%, wt%) of the colloidal silica is preferably 2wt% to 55wt%, more preferably 2wt% to 50wt%, further preferably 2wt% to 45wt%, and most preferably 3wt% to 40wt%. By adjusting the silica concentration of the colloidal silica to the preferred 2wt% to 55wt%, the grinding rate is excellent.

[0106] [3] Evaluation methods for the physical properties of colloidal silica In this invention, the physical properties of the silica particles are evaluated as described below.

[0107] (1-1) Determination method of particulate content parameter 1 (i) Add ultrapure water (hereinafter referred to as "ultrapure water") with a resistivity of 18.2 MΩ or higher to the colloidal silica sample to dilute it (diluent) so as to achieve a silica concentration of 2% by mass (wt%).

[0108] (ii) Take 9.1g of the diluted solution into a centrifuge sedimentation tube (model: S303922A) made by Eppendorf Himac Technologies Co., Ltd., and centrifuge it using a centrifuge 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 made by Eppendorf Himac Technologies Co., Ltd.).

[0109] (iii) After centrifugation, extract 2 mL of supernatant from the centrifuge sedimentation tube, and mix the 2 mL of supernatant after centrifugation with silica sol obtained by diluting the ultra-high purity colloidal silica PL-3 manufactured by Fuso Chemical Industry Co., Ltd. by 10 times with ultrapure water in the following mass ratio.

[0110] The supernatant after centrifugation is 9 parts by 10 parts by 1 part by 1 (mass ratio) of PL-3 dilution. The resulting mixture was used as sample 1 for testing.

[0111] (iv) The particle size distribution of sample 1 was determined using a particle size distribution measuring device based on the scanning electromobility particle size determination method. For example, a particle size distribution measuring device based on the scanning electromobility particle size determination method is the Liquid Nanoparticle Sizer System Model 9310 (LNS) manufactured by KANOMAX. The LNS was used to perform the measurement under the particle size distribution determination conditions described in (1-2) below.

[0112] (v) Calculate the particle content parameter 1 of the colloidal silica sample using the following formula based on the obtained particle size distribution measurement.

[0113] Formula (1): Particle content parameter 1 = (Total number of particles below 15nm detected) ÷ (Total number of particles above 25nm detected) (1-2) Particle size distribution determination conditions (i) The air used for measurement is dry air obtained by refining compressed air generated by a compressor using an air filter (CKD, FCS500-88-P90).

[0114] (ii) The LNS apparatus is supplied with ultrapure water and the aforementioned dry air, and a pre-operation is performed for more than 24 hours before the measurement.

[0115] (iii) Clean the measuring device with ultrapure water. 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 5.0E+11 (# / mL).

[0116] (iv) Under the test conditions shown in Table 1, the determination of KANOMAX-manufactured LNSVolumetric Standard, which serves as the standard particle, was carried out.

[0117] (v) Clean the measuring apparatus with ultrapure water. 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).

[0118] The determination of sample 1 was carried out under the determination conditions shown in Table 1 (vi).

[0119] The particle content parameter 1 of colloidal silica, as determined by the above-mentioned method, is below 15.0.

[0120] The particle content parameter 1 of colloidal silica, as measured by the above-described method, is 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, the amount of residual particles on the polishing surface can be reduced.

[0121] (2-1) Determination method of particulate content parameter 2 (%) (i) Add ultrapure water (hereinafter referred to as "ultrapure water") with a resistivity of 18.2 MΩ or higher to the colloidal silica sample to dilute it to a silica concentration of 0.1% by mass (wt%). Use the resulting diluted solution as sample 2.

[0122] (ii) The particle size distribution of sample 2 was determined using a particle size distribution measuring device based on the scanning electromobility particle size determination method. For example, a particle size distribution measuring device based on the scanning electromobility particle size determination method is the Liquid Nanoparticle Sizer System Model 9310 (LNS) manufactured by KANOMAX. The LNS was used to perform the measurement under the following particle size distribution determination conditions (2-2).

[0123] (iii) Calculate the particle content parameter 2 of the colloidal silica sample using the following formula based on the obtained particle size distribution measurement.

[0124] Equation (3): Particle content parameter 2 = (Total number of particles detected below 15nm) ÷ (Total number of all particles detected) × 100 [%] (2-2) Particle size distribution determination conditions (i) The air used for measurement is dry air obtained by refining compressed air generated by a compressor using an air filter (CKD, FCS500-88-P90).

[0125] (ii) The LNS apparatus is supplied with ultrapure water and the aforementioned dry air, and a pre-operation is performed for more than 24 hours before the measurement.

[0126] (iii) Clean the measuring device with ultrapure water. 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 5.0E+11 (# / mL).

[0127] (iv) Under the test conditions shown in Table 1 (LNS test conditions), the LNS Volumetric Standard manufactured by KANOMAX was tested as a standard particle.

[0128] (v) Clean the measuring apparatus with ultrapure water. 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).

[0129] (vi) The determination of sample 2 was carried out under the determination conditions shown in Table 1.

[0130] The particle content parameter 2 of colloidal silica, as determined by the above-mentioned method, is below 8.0%.

[0131] The particle content parameter 2 of the colloidal silica, as measured by the above-described method, is 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 residual particles on the polishing surface can be reduced.

[0132] [Table 1] (3) The proportion of particles evaluated using SEM (%) (i) A dispersion consisting of 7.5 mL methanol, 1.5 mL water, 1 mL 0.01 M HCl, and 5 μL 20% colloidal silica was dropped onto the sample stage and allowed to dry. The sample stage was then placed on a scanning electron microscope (SEM) and an SEM image was taken.

[0133] (ii) Using image analysis software (WinRoof2018, Mitani Corporation), the images of 1,000 silica particles captured by a scanning electron microscope were approximated as ellipses, and the minor axis of the ellipses was determined.

[0134] (iii) In the frequency distribution of the number of minor axes of the ellipse obtained by SEM image analysis above, particles whose minor axes are less than 25% of the average value are defined as microparticles, and the proportion of microparticles is calculated.

[0135] The proportion of colloidal silica with particle content evaluated by SEM is preferably 0.1% or less. By adjusting the proportion of colloidal silica with particle content evaluated by SEM to 0.1% or less, the amount of residual particles on the polishing surface can be reduced.

[0136] (4) Average primary particle size (nm) Colloidal silica was pre-dried on a hot plate and then heat-treated at 800°C for 1 hour to prepare a sample for measurement. The BET specific surface area was measured using the prepared sample. The true specific gravity of silica was set to 2.2. The conversion was 2727 / BET specific surface area (m²). 2 The value of ( / g) is used as the average primary particle size (nm) of silica particles in colloidal silica.

[0137] The average primary particle size of colloidal silica is preferably 5 nm to 130 nm, more preferably 10 nm to 120 nm, further preferably 12 nm to 110 nm, and most preferably 14 nm to 100 nm. By adjusting the average primary particle size of colloidal silica to preferably 5 nm to 130 nm, the surface roughness during grinding can be reduced.

[0138] (5) Average secondary particle size (nm) Add 0.3% by mass of citric acid aqueous solution to colloidal silica to dilute it to a silica concentration of 1.0% by mass (wt%) (diluent).

[0139] The diluent was used as the sample for measurement. The average secondary particle size was determined using the sample by dynamic light scattering (manufactured by Otsuka Electronics Co., Ltd., ELSZ-2000).

[0140] The average secondary particle size (nm) of colloidal silica is preferably 20nm to 250nm, more preferably 24nm to 200nm, further preferably 27nm to 170nm, and most preferably 30nm to 140nm. By adjusting the average secondary particle size of colloidal silica to preferably 20nm to 250nm, the roughness of the polished surface can be reduced.

[0141] (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.

[0142] The association ratio of silica particles in colloidal silica is preferably 1.0 or more, more preferably 1.1 or more, further 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 grinding speed when using colloidal silica for grinding is further improved.

[0143] Furthermore, 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, the surface roughness of the polished surface when using colloidal silica for polishing can be reduced.

[0144] (7) Silica concentration (mass % (wt%)) After pre-drying the colloidal silica on a hot plate, it is heat-treated at 800°C for 1 hour, and the remaining amount is calculated.

[0145] The silica concentration of the colloidal silica is preferably 2wt% to 55wt%, more preferably 2wt% to 50wt%, further preferably 2wt% to 45wt%, and most preferably 3wt% to 40wt%. By adjusting the silica concentration of the colloidal silica to 2wt% to 55wt%, the grinding speed when grinding the colloidal silica is further improved.

[0146] (8) Silanol group density (number / nm) 2 ) The silanol density of colloidal silica can be determined using the Sears method. The Sears method is performed according to the description in GWSears, Jr., “Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide”, Analytical Chemistry, 28(12), 1981(1956). The determination was performed using a 1 wt% silica dispersion titrated with a 0.1 mol / L sodium hydroxide aqueous solution, and the silanol density was calculated based on the following formula.

[0147] ρ=(a×f×6022)÷(c×S) In the above formula, ρ represents the density of silanol groups (numbers / nm). 2 ), a represents the volume (mL) of 0.1 mol / L sodium hydroxide aqueous solution with pH 4-9 added, f represents the factor of 0.1 mol / L sodium hydroxide aqueous solution, c represents the mass (g) of silica particles, and S represents the BET specific surface area (m²). 2 / g).

[0148] The preferred density of silanol groups in colloidal silica particles is 1.5 groups / nm. 2 The above, and more preferably 1.6 per nm 2 The above, and more preferably 1.8 per nm 2 The above, and the optimal value is 2.0 units / nm. 2 The above. By adjusting the lower limit of the silanol group density to 1.5 groups / nm. 2 The above measures can further reduce damage to the workpiece being ground.

[0149] In addition, the density of silanol groups is preferably 10.0 groups / nm. 2 The following, and more preferably, is 9.5 per nm. 2 The following, and more preferably 9.0 per nm 2 The optimal value is 8.8 per nm. 2 The following is an example of adjusting the upper limit of silanol group density to 10.0 groups / nm.2 The abrasiveness of colloidal silica is further improved below.

[0150] (9) True specific gravity In this invention, the true specific gravity can be determined by drying and curing colloidal silica on a hot plate at 150°C, maintaining it in an oven at 300°C for 1 hour, and then using ethanol via liquid-phase displacement method.

[0151] The true specific gravity of the silica particles contained in the colloidal silica is preferably 1.0 or more, more preferably 1.2 or more, further preferably 1.4 or more, and most preferably 1.5 or more. By adjusting the lower limit of the true specific gravity to 1.0 or more, the abrasiveness of the colloidal silica of the present invention is further improved.

[0152] Furthermore, 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 upper limit of the true specific gravity to 3.0 or less, damage to the workpiece being ground can be further reduced.

[0153] (10) Metal impurity content (ppm) The content of metallic impurities was determined using an atomic absorption spectrometer. The total content of sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt in colloidal silica was taken as the content of metallic impurities.

[0154] The content of metallic impurities in colloidal silica is preferably below 1 ppm. By adjusting the content of metallic impurities in colloidal silica to below 1 ppm, it is suitable for CMP slurry applications.

[0155] (11) RMS (nm) of the ground surface roughness Ultrapure water was added to colloidal silica to dilute it to a silica concentration of 3.0% by mass (wt%), thus preparing a grinding composition.

[0156] Using the obtained polishing composition, a 3 cm square silicon chip with a silicon oxide film formed on its surface was polished under the following conditions.

[0157] Grinding machine: Manufactured by Nano Factor Co., Ltd., NF-300CMP Grinding pad: Made by NidaDuPont, Inc., IC1000TMPad Slurry feed rate: 50 mL / min Grinding head speed: 32 rpm Table speed: 32 rpm Grinding pressure: 4 psi Grinding time: 2 min For the polished chip, the surface roughness of the polished surface was evaluated using atomic force microscopy under the following conditions.

[0158] Atomic force microscope: Shimadzu Corporation SPM-9700HT Cantilever beam: OLYMPUS, MICRO CANTILEVER OMCL-AC240TS-R3 Observation Mode: Dynamic Mode Scan range: 3.0 μm square Scan speed: 1.00 Hz Number of fields of view: Five fields of view are observed for each polished chip.

[0159] Surface roughness calculation method: The average value of the root mean square roughness of 5 fields of view is taken as the surface roughness (RMS) of the grinding surface.

[0160] The surface roughness RMS (nm) of the polished surface is preferably below 3.00 nm.

[0161] (12) Number of residual particles on the grinding surface (number / μm) 2 ) Ultrapure water was added to colloidal silica to dilute it to a silica concentration of 3.0% by mass (wt%), thus preparing a grinding composition.

[0162] Using the obtained polishing composition, a 3 cm square silicon chip with a silicon oxide film formed on its surface was polished under the following conditions.

[0163] Grinding machine: Manufactured by Nano Factor Co., Ltd., NF-300CMP Grinding pad: Made by NidaDuPont, Inc., IC1000TMPad Slurry feed rate: 50 mL / min Grinding head speed: 32 rpm Table speed: 32 rpm Grinding pressure: 4 psi Grinding time: 2 min The polished silicon chip is cleaned using a brush unit built into the MAT ZAB-8S1M cleaning and drying unit, under the following conditions, by contacting a PVA roller brush. To secure the silicon chip, a clamp with a frame made of glass epoxy resin and a chip-fixing portion made of polyurethane is used.

[0164] Brush: Made by AION, AION SCL BRUSH ROLLER 48(40 / 26)×224 mm Scrubbing and cleaning time: 1 min Brush speed: 200 rpm Rotational speed of the silicon chip holder: 50 rpm After brushing and cleaning, ultrapure water is circulated to the upper side of the polishing substrate at 750 mL / min for 1 minute, and then treated for 20 seconds at 1800 rpm using the rotary drying device built into the above device.

[0165] For dried silicon chips, the number of residual particles on the polished surface is measured using the SPM-9700HT manufactured by Shimadzu Corporation.

[0166] Number of residual particles on the grinding surface (number / μm) 2 Preferably 3 / μm 2 the following.

[0167] [4] Grinding composition The present invention includes a grinding composition containing colloidal silica of the present invention.

[0168] The grinding composition is suitable for CMP applications.

[0169] The grinding composition contains colloidal silica and may further contain additives. Examples of additives include diluents, oxidants, pH adjusters, corrosion inhibitors, stabilizers, and surfactants.

[0170] The content (mass%, wt%, silica concentration) of colloidal silica in the grinding composition is preferably 0.01wt% to 20wt%, more preferably 0.1wt% to 15wt%, further preferably 1wt% to 10wt%, and particularly preferably 2wt% to 5wt%.

[0171] The embodiments of the present invention have been described above, but the present invention is not limited to these examples. The present invention can, of course, be implemented in various ways without departing from the spirit of the invention.

[0172] [Example] The present invention will be specifically described by listing examples.

[0173] However, the present invention is not limited to the embodiments described herein.

[0174] [1] Manufacturing of colloidal silica (1) Example 1 (with heat treatment) Preparation of silica sol by heating and water replacement In solution A, which contains 976g of methanol, 97g of water, and 58g of 29% ammonia, 190g of methanol, 506g of tetramethoxysilane (TMOS), and 119g of pure water (pH=7.85) were added at a constant rate over 75 minutes.

[0175] When preparing the reaction solution, the temperature of each liquid before mixing is maintained at 35°C, and the temperature of the reaction solution is adjusted so that the initial reaction temperature of 35°C when adding solution B to solution A (at the start of synthesis) is reduced to the termination reaction temperature of 24.5°C when the addition is completed (at the end of synthesis), while the total amount of solution B and solution C is added to solution A at a uniform rate.

[0176] The reaction solution was concentrated by heating and then replaced with heated water under stirring conditions. The methanol concentration after water replacement was 301 ppm.

[0177] Manufacturing of colloidal silica (heat treatment) 0.65 parts by mass of 3-ethoxypropylamine (3-EOPA) were added to 100 parts by mass of the silica sol obtained above after water replacement to adjust the pH to 9.9. The silica sol was then heated at 100°C under normal pressure while being stirred. The moment the silica sol reached 100°C was taken as the start of the heating treatment. Samples were taken every 0.5 hours after the start of the heating treatment for pH measurement.

[0178] After 0.5 hours from the start of the heat treatment, the pH reached 9.6, so 0.2 parts by weight of 3-EOPA were added to adjust the pH to 9.9. This process was repeated every 1.5 hours from the start to the end of the heat treatment. A total of 2.2 parts by weight of 3-EOPA were added from the start to the end of the heat treatment.

[0179] After undergoing the above-mentioned heating treatment for 16 hours, colloidal silica was obtained.

[0180] Determination of methanol concentration A gas chromatograph (Thermo Fisher Scientific, FocusGC), an autosampler (Thermo Fisher Scientific AS3000 or equivalent or higher), and an air compressor (capable of supplying compressed air at 0.4 MPa or higher) were used. 1 μL of sample was drawn into a 10 μL syringe, which was then attached to the autosampler for analysis.

[0181] (2) Example 2 (with heat treatment) Preparation of silica sol by heating and water replacement In solution A, which is a mixture of 7.7g pure water, 96.8g methanol and 4.5g 29% ammonia, the temperature was maintained at 36℃. Then, solution B, which is a mixture of 100g TMOS and 17.7g methanol, and solution C, which is a mixture of 31.7g pure water and 4.7g 29% ammonia, were added at a constant rate over 217 minutes.

[0182] After the addition is complete, maintain the temperature of the reaction solution at 36°C, and then stir the reaction solution for another 30 minutes under this condition.

[0183] The reaction solution was concentrated by heating and then replaced with heated water under stirring conditions. The methanol concentration after water replacement was 212 ppm.

[0184] Manufacturing of colloidal silica (heat treatment) Add 0.6 parts by mass of 3-EOPA to 100 parts by mass of the silica sol obtained above after water replacement to adjust the pH to 9.8. Then, while stirring the silica sol, heat it at 100°C under normal pressure. The moment the silica sol reaches 100°C is considered the start of the heating treatment. Samples are taken every 0.5 hours after the start of the heating treatment for pH measurement.

[0185] After 0.5 hours from the start of the heat treatment, the pH reached 9.6, so 0.12 parts by weight of 3-EOPA were added to adjust the pH to 9.8. This process was repeated every 1.0 hour from the start to the end of the heat treatment. A total of 2.76 parts by weight of 3-EOPA were added from the start to the end of the heat treatment.

[0186] The above-mentioned heating treatment was carried out for 23.0 hours to obtain colloidal silica.

[0187] (3) Example 3 (Example with heat treatment and small average particle size) Preparation of silica sol by heating and water replacement In solution A, which is a mixture of 463.1 g of pure water, 104.8 g of 26% ammonia solution, and 4255.0 g of methanol, the liquid temperature was maintained at 50°C. Then, solution B, which is a mixture of 3,044.4 g of TMOS and 229.4 g of methanol, and solution C, which is a mixture of 643.2 g of pure water and 104.8 g of 26% ammonia solution, were added at a uniform rate over 150 minutes.

[0188] The reaction solution was concentrated by heating and then replaced with heated water under stirring conditions. The methanol concentration after water replacement was 198 ppm.

[0189] Manufacturing of colloidal silica (heat treatment) Add 0.65 parts by weight of 3-EOPA to 100 parts by weight of the silica sol obtained above after water replacement to adjust the pH to 9.9. Then, while stirring the silica sol, heat it at 100°C under normal pressure. The moment the silica sol reaches 100°C is considered the start of the heat treatment. Samples are taken every 0.5 hours after the start of the heat treatment for pH measurement.

[0190] After 0.5 hours from the start of the heat treatment, the pH reached 9.6, so 0.2 parts by weight of 3-EOPA were added to adjust the pH to 9.9. This process was repeated every 1.0 hour from the start to the end of the heat treatment. A total of 3.2 parts by weight of 3-EOPA were added from the start to the end of the heat treatment.

[0191] The above-mentioned heating treatment was carried out for 24.5 hours to obtain colloidal silica.

[0192] (4) Example 4 (Example with heat treatment and large average particle size) Preparation of silica sol by heating and water replacement In solution A, which is a mixture of 1546.6g of pure water, 340.6g of 26% ammonia, and 8,363.2g of methanol, the temperature was maintained at 20°C. Then, solution B, a mixture of 6,088.0g of TMOS and 350.0g of methanol, and solution C, a mixture of 1,186.2g of pure water and 340.6g of 26% ammonia, were added at a uniform rate over 100 minutes.

[0193] The reaction solution was concentrated by heating and then replaced with heated water under stirring conditions. The methanol concentration after water replacement was 196 ppm.

[0194] Manufacturing of colloidal silica (heat treatment) Add 0.65 parts by weight of 3-EOPA to 100 parts by weight of the silica sol obtained above after water replacement to adjust the pH to 9.9. Then, while stirring the silica sol, heat it at 100°C under normal pressure. The moment the silica sol reaches 100°C is considered the start of the heating treatment. Samples are taken every 0.25 hours after the start of the heating treatment for pH measurement.

[0195] After 0.25 hours from the start of the heat treatment, the pH reached 9.7, so 0.15 parts by weight of 3-EOPA were added to adjust the pH to 9.9. This process was repeated every 1.0 hour from the start to the end of the heat treatment. A total of 3.0 parts by weight of 3-EOPA were added from the start to the end of the heat treatment.

[0196] The above-mentioned heating treatment was carried out for 20.0 hours to obtain colloidal silica.

[0197] (5) Example 5 (Example with heat treatment and low silica concentration during heating) Preparation of silica sol by heating and water replacement The reaction solution obtained in Example 1 was subjected to water replacement under stirring conditions. The methanol concentration after water replacement was 387 ppm.

[0198] Manufacturing of colloidal silica (heat treatment) Add 0.65 parts by weight of 3-EOPA to 100 parts by weight of the silica sol obtained above after water replacement to adjust the pH to 9.9. Then, while stirring the silica sol, heat it at 100°C under normal pressure. The moment the silica sol reaches 100°C is considered the start of the heat treatment. Samples are taken every 0.5 hours after the start of the heat treatment for pH measurement.

[0199] After 0.5 hours from the start of the heat treatment, the pH reached 9.6, so 0.2 parts by weight of 3-EOPA were added to adjust the pH to 9.9. This process was repeated every 1.5 hours from the start to the end of the heat treatment. A total of 2.4 parts by weight of 3-EOPA were added from the start to the end of the heat treatment.

[0200] The above-mentioned heating treatment was carried out for 18.0 hours to obtain colloidal silica.

[0201] (6) Example 6 (Example with heat treatment and high silica concentration during heating) Preparation of silica sol by heating and water replacement The reaction solution obtained in Example 1 was concentrated by heating and replaced with heated water under stirring conditions. The methanol concentration after water replacement was 184 ppm.

[0202] Manufacturing of colloidal silica (heat treatment) Add 0.65 parts by weight of 3-EOPA to 100 parts by weight of the silica sol obtained above after water replacement to adjust the pH to 9.9. Then, while stirring the silica sol, heat it at 100°C under normal pressure. The moment the silica sol reaches 100°C is considered the start of the heat treatment. Samples are taken every 0.5 hours after the start of the heat treatment for pH measurement.

[0203] After 0.5 hours of heating, the pH reached 9.6, so 0.2 parts by weight of 3-EOPA were added to adjust the pH to 9.9. This process was repeated every 1.5 hours from the start to the end of the heating treatment. A total of 2.0 parts by weight of 3-EOPA was added from the start to the end of the heating treatment.

[0204] The above-mentioned heating treatment was carried out for 15.5 hours to obtain colloidal silica.

[0205] (7) Comparative Example 1 (without heat treatment) This is an example of simulating existing technology (Patent Document 1: Japanese Patent Application Publication No. 2020-164351 and Patent Document 3: International Publication No. WO2016 / 117560A1).

[0206] In solution A, which contains 976g of methanol, 97g of water, and 58g of 29% ammonia, 190g of methanol, 506g of tetramethoxysilane (TMOS), and 119g of pure water (pH=7.85) were added at a constant rate over 75 minutes.

[0207] When preparing the reaction solution, the temperature of each liquid before mixing is maintained at 35°C, and the temperature of the reaction solution is adjusted so that the initial reaction temperature of 35°C when adding solution B to solution A (at the start of synthesis) is reduced to the termination reaction temperature of 24.5°C when the addition is completed (at the end of synthesis), while the total amount of solution B and solution C is added to solution A at a uniform rate.

[0208] The reaction solution was heated and concentrated under stirring conditions, and then replaced with hot water to obtain colloidal silica.

[0209] (8) Comparative Example 2 (without heat treatment) This is an example of simulating existing technology (Patent Document 2: Japanese Patent Application Publication No. 2022-109711 and Patent Document 3).

[0210] In solution A, which is a mixture of 7.7g pure water, 96.8g methanol, and 4.5g 29% ammonia, the temperature was maintained at 36℃. At the same time, solution B, which is a mixture of 100g tetramethoxysilane and 17.7g methanol, and solution C, which is a mixture of 31.7g pure water and 4.7g 29% ammonia, were added at a constant rate over a period of 217 minutes.

[0211] After the addition is complete, maintain the temperature of the reaction solution at 36°C and stir the reaction solution for another 30 minutes under this condition.

[0212] The reaction solution was heated and concentrated under stirring conditions, and then replaced with hot water to obtain colloidal silica.

[0213] (9) Comparative Example 3 (without heat treatment) This is an example of simulating existing technology (Patent Documents 2-3 and Patent Document 4: Japanese Patent Application Publication No. 2020-75830).

[0214] In the colloidal silica obtained in Comparative Example 2, 35% by mass of hydrogen peroxide was added in such a way that the content of hydrogen peroxide was 0.5g per 100g of silica relative to tetraalkoxysilane, to obtain colloidal silica.

[0215] (10) Comparative Example 4 (without heat treatment) This is an example of simulating existing technology (Patent Documents 2-4 and Patent Document 5: Japanese Patent Application Publication No. 2021-116208).

[0216] The pencil-type module (PX-02001) manufactured by Asahi Kasei Corporation used an ultrafiltration membrane with a molecular weight cutoff of 80,000 (Laboratory module AOP-0013 manufactured by Asahi Kasei Corporation), the pumps used were Masterflex L / S Easy-Load PumpHeads for Precision Tubing, Avantor (MFLX07514-10) and Masterflex L / S AnalogModular Drive Replacement Controllers, Avantor (MFLX07559-04), and the tubing used was Masterflex silica hydrolysis tubing (96400-25). 120 g of colloidal silica obtained in Comparative Example 3 was ultrafiltered to obtain colloidal silica.

[0217] The amount of liquid that passed through the ultrafiltration membrane was 63.6g, and its permeation rate was 53%.

[0218] (11) Comparative Example 5 (Example of long-term ultrafiltration without heat treatment) This is an example of simulating existing technology (Patent Documents 2-5).

[0219] The pencil-type module (PX-02001) manufactured by Asahi Kasei Corporation used an ultrafiltration membrane with a molecular weight cutoff of 80,000 (Laboratory module AOP-0013 manufactured by Asahi Kasei Corporation), the pumps used were Masterflex L / S Easy-Load PumpHeads for Precision Tubing, Avantor (MFLX07514-10) and Masterflex L / S AnalogModular Drive Replacement Controllers, Avantor (MFLX07559-04), and the tubing used was Masterflex silica hydrolysis tubing (96400-25). 40 g of colloidal silica obtained in Comparative Example 4 was ultrafiltered to obtain colloidal silica.

[0220] During the ultrafiltration process, ultrapure water is added to the colloidal silica to maintain a constant liquid volume of colloidal silica.

[0221] The amount of liquid that passed through the ultrafiltration membrane was 220.5g, and the ultrafiltration time was 152 minutes.

[0222] [Table 2] [Table 3] [2] Evaluation results Examples 1 to 6 are colloidal silica produced by a method for manufacturing colloidal silica that includes a step of heating a silica sol composed of water and silica particles at atmospheric pressure using the boiling point of water.

[0223] The colloidal silica in Examples 1 to 6 satisfies (i) an average secondary particle size of 20 nm to 250 nm and (ii) a particle content parameter 1 of 15.0 or less.

[0224] The colloidal silica in the embodiments can suppress the content of particles to a low level.

[0225] Comparative Examples 1 to 5 are colloidal silica produced by a method for manufacturing colloidal silica that does not involve a heat treatment step.

[0226] Comparative Examples 1-5 are examples that simulate existing technologies.

[0227] Comparative Example 1, which simulates examples from Patent Documents 1 and 3, failed to effectively reduce particles smaller than 15 nm.

[0228] Comparative Example 2, which simulates examples from Patent Documents 2 and 3, failed to effectively reduce particles smaller than 15 nm.

[0229] Comparative Example 3 simulates the examples in Patent Documents 2-4 and failed to effectively reduce particles smaller than 15 nm.

[0230] Comparative Example 4 simulates the examples in Patent Documents 2-5 and failed to effectively reduce particles smaller than 15 nm.

[0231] Comparative Example 5 simulates patent documents 2-5, examples of long-term ultrafiltration with the intention of reducing particulate matter, and confirms that the average secondary particle size increases due to particle aggregation.

[0232] [3] Industrial availability The method for manufacturing colloidal silica of the present invention includes a step of heating a silica sol composed of water and silica particles at atmospheric pressure using the boiling point of water.

[0233] The colloidal silica of the present invention satisfies (i) an average secondary particle size of 20 nm to 250 nm, and (ii) a particle content parameter 1 as defined below of 15.0 or less.

[0234] Definition of particulate content parameter 1 (i) Add ultrapure water (hereinafter referred to as "ultrapure water") with a resistivity of 18.2 MΩ or higher to colloidal silica to dilute it to achieve a silica concentration of 2% by mass (wt%) (diluent).

[0235] (ii) Take 9.1g of the diluted solution into a centrifuge sedimentation tube (model: S303922A) made by Eppendorf Himac Technologies Co., Ltd., and centrifuge it using a centrifuge 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 made by Eppendorf Himac Technologies Co., Ltd.).

[0236] (iii) After centrifugation, extract 2 mL of supernatant from the centrifuge sedimentation tube, and mix the 2 mL of supernatant after centrifugation with silica sol obtained by diluting the ultra-high purity colloidal silica PL-3 manufactured by Fuso Chemical Industry Co., Ltd. by 10 times with ultrapure water in the following mass ratio (mixture).

[0237] The supernatant after centrifugation is 9 parts by 10 parts by 1 part by 1 (mass ratio) of PL-3 dilution. (iv) The particle size distribution of the obtained mixture was determined by using a particle size distribution measuring device based on the scanning electromobility particle size determination method.

[0238] (v) The value calculated using the following formula (1) based on the obtained particle size distribution is defined as the particle content parameter 1 of colloidal silica.

[0239] Formula (1): Particle content parameter 1 = (Total number of particles below 15nm detected) ÷ (Total number of particles above 25nm detected) The colloidal silica of this invention contains a low content of microparticles.

[0240] When CMP is performed using the colloidal silica of the present invention as abrasive, the amount of residual particles on the grinding surface is significantly reduced compared to the case of using conventional colloidal silica as abrasive, and the surface roughness of the grinding surface is also reduced.

Claims

1. A method for manufacturing colloidal silica, characterized in that, This includes a process of heating a silica sol composed of water and silica particles at atmospheric pressure using the boiling point of water.

2. The method for manufacturing colloidal silica as described in claim 1, characterized in that, The pH of the silica sol during the heat treatment is between pH 9.0 and pH 10.

5. The heat treatment time is 11 to 35 hours. In the heating treatment, the stirring power of the silica sol was set to 0.01 kW / m 3 The stirring power of the silica sol was set to 0.01 kW / m 3 ~ 0.40 kW / m 3 under the condition of 0.01 kW / m2.

3. The method for manufacturing colloidal silica as described in claim 1 or 2, characterized in that, The silica sol is obtained by the following method. (a) Adding solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) Under the condition that the addition rate of the alkoxysilane contained in the solution B relative to 1 kg of the solution A is set to 0.8 mol / h / kg to 2.50 mol / h / kg, the alkoxysilane is subjected to hydrolysis and dehydration condensation.

4. The method for manufacturing colloidal silica as described in claim 1 or 2, characterized in that, The silica sol is obtained by the following method. (a) Adding solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) The alkoxysilane in solution B is hydrolyzed and dehydrated and condensed under the condition that the concentration of alkoxysilane is set to 60% to 98% by mass.

5. A colloidal silica, characterized in that, The particle content parameter 1, as defined below, is below 15.

0. Definition of particle content parameter 1: (i) Add ultrapure water with a resistivity of 18.2 MΩ or higher to colloidal silica to dilute it to a silica concentration of 2% by mass, and obtain a diluted solution; (ii) Take 9.1g of the diluent into a centrifuge sedimentation tube of model S303922A manufactured by Eppendorf Himac Technologies Co., Ltd., and centrifuge it using centrifuge rotor S58A and centrifuge CS100FNX manufactured by Eppendorf Himac Technologies Co., Ltd. at a centrifugation speed of 50,000 rpm, centrifugation temperature of 5°C and centrifugation time of 60 minutes. (iii) After centrifugation, extract 2 mL of supernatant from the centrifuge sedimentation tube, and mix the 2 mL of supernatant after centrifugation with silica sol obtained by diluting the ultra-high purity colloidal silica PL-3 manufactured by Fuso Chemical Industry Co., Ltd. by 10 times with the ultrapure water according to the following mass ratio to obtain a mixture. The mass ratio of supernatant after centrifugation to 10 times diluted PL-3 is 9:

1. (iv) The particle size distribution of the obtained mixture was determined using a particle size distribution measuring device based on the scanning electromobility particle size determination method. (v) The value calculated using the following formula (1) based on the obtained particle size distribution is defined as the particle content parameter 1 of colloidal silica. Formula (1): Particle content parameter 1 = (total number of detected particles of 15 nm or less) ÷ (total number of detected particles of 25 nm or more).

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