Colloidal silica and its manufacturing method

Abstract

We provide colloidal silica with a low concentration of fine particles. [Solution] A colloidal silica is provided, wherein the proportion of fine particles evaluated by a scanning electron microscope (SEM) as defined below is 0.1% or less, and the average secondary particle diameter is 20 nm to 69.3 nm. Definition of the proportion of fine particles evaluated by SEM: (i) A dispersion of 7.5 mL methanol, 1.5 mL water, 1 mL of 0.01 M HCl, and 5 μL of 20% colloidal silica is dropped onto a sample stage and allowed to dry. This sample stage is set in an SEM and an SEM image is taken. (ii) Images of 1,000 silica particles taken by SEM are each approximated as an ellipse using image analysis software, and the minor axis of the ellipse is measured. (iii) In the frequency distribution of the minor axis of the ellipse obtained from the SEM image analysis described above, particles whose minor axis is 25% or less of the average value are defined as fine particles, and the proportion of fine particles is calculated.

Description

[Technical Field]

[0001] This invention relates to colloidal silica with a low concentration of fine particles. [Background technology]

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

[0003] As semiconductor miniaturization progresses, there is a growing need to further reduce the amount of fine particles remaining on the polished surface, and consequently, there is a need to reduce the amount of fine particles contained in the CMP slurry. It is.

[0004] Colloidal silica is used as an abrasive material for CMP slurry. These particles typically contain a small amount of fine particles that are smaller than the main particles, 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 hydrolysis and condensation reaction of alkoxysilane or its condensate, From 5 minutes after the point at which electrical conductivity first reaches its maximum after the start of the reaction, until the end of the reaction, the electrical conductivity By adjusting the reaction conditions so that the value does not change by more than 90%, a silica sol with fewer fine particles can be obtained. Disclosed. Patent Document 2 describes the hydrolysis and condensation reaction of tetraalkoxysilanes, This invention discloses how to obtain a silica sol with fewer fine particles by keeping the change in water concentration within the reaction system within 3% by mass from the start to the end of the water splitting and condensation reactions.

[0006] Further, there have been disclosed a method of subjecting produced colloidal silica to solvent replacement treatment by heating distillation 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 by distilling off the organic solvent coexisting with colloidal silica produced by a sol-gel method such that the concentration of residual organic solvent in the colloidal silica is less than 1% by mass, 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. Patent Document 4 discloses that by adding a neutral oxidizing agent (including hydrogen peroxide) to a silica sol obtained by a sol-gel method, a silica sol with few intermediate products (unreacted substances) is obtained. Patent Document 5 discloses that by subjecting a silica sol obtained by hydrolyzing and condensing tetraalkoxysilane to ultrafiltration using an ultrafiltration membrane with a fractional molecular weight of 5,000 to 80,000, intermediate products are removed.

[0007] Even with these conventional techniques, colloidal silica having a fine particle content reduced to a level that sufficiently satisfies the requirements of semiconductor CMP processes for advanced technology nodes has not been obtained.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

[0009] This invention provides colloidal silica with fewer fine particles. [Means for solving the problem]

[0010] As a result of diligent research, the inventors of this 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 manufacturing process of colloidal silica.

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

[0012] Section 1. A method for producing colloidal silica, A process of heating a silica sol, which consists of water and silica particles, at the boiling point of water under normal pressure. A method for producing colloidal silica, including the method described above.

[0013] Section 2. The pH of the silica sol during the heat treatment is pH 9.0 to pH 10.5. The duration of the aforementioned heat treatment is 11 to 35 hours. The aforementioned heat treatment involves silica sol 1 m 3 The stirring power per unit is 0.01 kW / m 3 ~0.40kW / m 3 Under these conditions, the silica sol is stirred. The method for producing colloidal silica as described in item 1 above.

[0014] Section 3. The silica sol is (a) Add solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) A silica sol obtained by hydrolyzing and dehydrating the alkoxysilane contained in solution B to 1 kg of solution A at a rate of 0.8 mol / hour / kg to 2.50 mol / hour / kg. A method for producing colloidal silica as described in item 1 or 2 above.

[0015] Section 4. The silica sol is (a) Add solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) A silica sol obtained by hydrolyzing and dehydrating condensing the alkoxysilane contained in solution B under conditions where the alkoxysilane concentration is 60% to 98% by mass. A method for producing colloidal silica as described in item 1 or 2 above.

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

[0017] Definition of particulate matter content parameter 1 (i) Add ultrapure water with an electrical resistivity of 18.2 MΩ or higher (hereinafter referred to as "ultrapure water") to colloidal silica to dilute it to a silica concentration of 2% by mass (wt%) (diluted solution).

[0018] (ii) Dilute 9.1 g is placed in an Eppendorf Highmac Technologies centrifuge tube (model number: S303922A), and centrifuged using a centrifuge rotor S58A and centrifuge CS100FNX at a centrifugal speed of 50,000 rpm, a centrifugal temperature of 5°C, and a centrifugal time of 60 minutes (all Eppendorf (Manufactured by Fu-Hi-Mac Technologies, Inc.)

[0019] (iii) After centrifugation, take 2 mL of the supernatant from the centrifuge tube, and mix this 2 mL of centrifugation supernatant with Fusoka Mix ultra-high-purity colloidal silica PL-3 manufactured by Gaku Kogyo Co., Ltd. with silica sol obtained by diluting it 10 times with ultrapure water in the following mass ratio (mixture).

[0020] Centrifuged supernatant: 10-fold dilution of PL-3 = 9:1 (mass ratio) (iv) The particle size distribution of the obtained mixture is measured using a particle size distribution analyzer based on the scanning electrical mobility diameter measurement method.

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

[0022] Equation (1) Particulate matter content parameter 1 = (Total number of particles detected that are 15 nm or smaller) ÷ (Total number of particles detected that are 25 nm or larger) 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 an abrasive grain, it is compared to when conventional colloidal silica is used as an abrasive grain. In comparison, the amount of residual fine particles on the polished surface is significantly reduced, and the surface roughness of the polished surface can also be reduced. [Effects of the Invention]

[0023] This invention can provide colloidal silica with fewer fine particles. [Modes for carrying out the invention]

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

[0025] The embodiments illustrating the present invention are intended to provide a better understanding of the invention's intent and, unless otherwise specified, do not limit the scope of the invention.

[0026] In this specification, "contains" and "include" are concepts that encompass all of "comprise," "consist essentially of," and "consist of."

[0027] In this specification, when a numerical range is indicated as "A to B", it means "greater than or equal to A and less than or equal to B".

[0028] In this specification, the notations "parts," "%," etc., are generally used.

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

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

[0031] The present invention provides a method for producing colloidal silica, which includes a step of heating 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 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 performed using silica sol 1 m 3 The stirring power per unit is 0.01 kW / m 3 ~0.40kW / m 3 The silica sol is stirred under the following conditions.

[0035] Silica sol (silica sol consisting of water and silica particles) is preferably, (a) Add solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) A silica sol obtained by hydrolyzing and dehydrating condensing the alkoxysilane contained in solution B to 1 kg of solution A, under conditions where the addition rate of the alkoxysilane contained in solution B is 0.8 mol / hour / kg to 2.50 mol / hour / kg.

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

[0037] Silica sol (silica sol consisting of water and silica particles) is preferably, (a) Add solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) A silica sol obtained by hydrolyzing and dehydrating condensing an alkoxysilane in solution B under conditions where the alkoxysilane concentration is 60% 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 manufacturing method of the present invention as an abrasive, the amount of remaining fine particles on the polished surface is low. It is possible to significantly reduce the amount of material produced and to reduce the surface roughness of the polished surface.

[0039] In the present invention's method for producing colloidal silica, preferably (i) silica is obtained by the alkoxide method. (ii) Synthesize particles (particle synthesis), (ii) concentrate the particle concentration by heating and distillation (heat concentration), (iii) (iv) By going through a series of operations, including (iv) replacing the solvent with water by heated distillation (heated water substitution) and (iv) reducing the fine particles by heat treatment (heat treatment), colloidal silica with fewer fine particles can be produced.

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

[0041] Three-liquid method (method for synthesizing silica particles) The synthesis of silica particles is preferably carried out by a three-liquid process, using water, an alkaline catalyst, and alcohol. Solution A containing alkoxysilane (tetraalkoxysilane) is mixed with solution B containing alkoxysilane and solution C containing water, and the alkoxysilane (tetraalkoxysilane) undergoes a hydrolysis reaction. Silica particles are synthesized by a condensation reaction. Preferably, the synthesis of silica particles is carried out using a three-liquid method, which provides excellent control over the hydrolysis and condensation reactions.

[0042] Solution A (3-solution method) In the synthesis of silica particles, a three-liquid method is employed, and the water concentration (mass%, wt%) of solution A is preferably 3wt% to 25wt%, more preferably 3wt% to 23wt%, even more preferably 3wt% to 20wt%, and most preferably 3wt% to 18wt%. By adjusting the water concentration of solution A to preferably 3wt% to 25wt%, 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%, the aggregation of silica particles is suppressed, and the dispersion stability of silica particles in the dispersion is excellent.

[0044] The alkali catalyst is preferably an organic base catalyst that does not contain metal components, in order to avoid contamination with metal impurities, and more preferably an organic base catalyst that contains 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, etc.

[0047] Ammonia is preferred because it exhibits excellent catalytic activity, is highly volatile, and can be easily removed in subsequent processes.

[0048] From the viewpoint of increasing the true specific gravity of silica particles, it is preferable to select an organic base catalyst with a boiling point of 90°C or higher so that it does not easily volatilize even when the reaction temperature is high. Preferably, tetramethylammonium hydroxide, 3-ethoxypropylamine, etc., are used.

[0049] Alkaline catalysts may be used individually or in mixtures (blends) of two or more types.

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

[0051] Alcohols may be used individually or in mixtures (blends) of two or more types.

[0052] Solution B (3 liquid method) The silica sol is preferably, (a) Add solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) A silica sol obtained by hydrolyzing and dehydrating condensing an alkoxysilane under conditions where the alkoxysilane concentration (mass%, wt%) in solution B is 60% by mass to 98% by 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 silica particle productivity.

[0054] The silica sol is preferably, (a) Add solution B containing alkoxysilane to solution A containing water and an alkaline catalyst, (b) A silica sol obtained by hydrolyzing and dehydrating condensing the alkoxysilane contained in solution B to 1 kg of solution A, under conditions where the addition rate of the alkoxysilane contained in solution B is 0.8 mol / hour / kg to 2.50 mol / hour / kg.

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

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

[0057] The alkoxysilane is preferably tetramethoxysilane (TMOS), tetraethoxysilane, tetraisopropoxysilane, etc. 1-8 Alkoxysilanes are used. More preferably, tetraC alkoxysilanes are used. 1-4Alkoxysilanes are used, and more preferably, tetramethoxysilane (TMOS), tetraethoxysilane, etc.

[0058] Alkoxysilanes may be used individually or as a mixture (blend) of two or more types.

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

[0060] Alcohols may be used individually or in mixtures (blends) of two or more types.

[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 0wt% to 9wt%, more preferably 0wt% to 8wt%, even more preferably 0wt% to 7wt%, and most preferably 0wt% to 6wt%. Preferably, by adjusting the amount to 0 wt% to 9 wt%, the reaction does not proceed excessively slowly, resulting in excellent controllability.

[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, etc.

[0064] Ammonia is preferred because it exhibits excellent catalytic activity, is highly volatile, and can be easily removed in subsequent processes.

[0065] From the viewpoint of increasing the true specific gravity of silica particles, it is preferable to select an organic base catalyst with a boiling point of 90°C or higher so that it does not easily volatilize even when the reaction temperature is high. Preferably, tetramethylammonium hydroxide, 3-ethoxypropylamine, etc., are used.

[0066] Alkaline catalysts may be used individually or in mixtures (blends) of two or more types.

[0067] Hydrolysis reactions and condensation reactions In the synthesis of silica particles, a three-liquid method was adopted to initiate the hydrolysis and condensation reactions. The maximum concentration of water in the reaction system from the start to the end of the reaction (mass%, wt%) is preferably 28 wt%. The following is the case, more preferably 25 wt% or less, even more preferably 20 wt% or less, and most preferably 18 wt% or less. From the start of the hydrolysis reaction and the condensation reaction to the end of the reaction. By adjusting the maximum concentration of water in the reaction system up to a certain point, preferably to 28 wt% or less, the reaction The solubility of alkoxysilanes (such as tetraalkoxysilanes) in the solution is improved, This can suppress the generation of fine particles of lichen.

[0068] In the synthesis of silica particles, a three-liquid method was adopted to initiate the hydrolysis and condensation reactions. The change in water concentration (mass%, wt%) within the reaction system from the start to the end of the reaction is preferably 15 wt% or less. The water content is preferably 13 wt% or less, more preferably 11 wt% or less, and most preferably 8 wt% or less. By adjusting the change in water concentration in the reaction system from the start to the end of the hydrolysis and condensation reactions to preferably 15 wt% or less, the reaction produces The solubility of the resulting silica is maintained, and the generation of fine silica particles can be suppressed.

[0069] In the synthesis of silica particles, a three-liquid method is employed. The reaction temperature (°C) is preferably 10°C to 80°C, more preferably 12°C to 70°C, and still more preferably 15°C to 60°C, and most preferably 18°C to 55°C. By adjusting the reaction temperature for the synthesis of 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 the production method of obtaining silica sol by hydrolyzing and dehydration-condensing alkoxysilane (a method for synthesizing silica particles by the alkoxide method), a production method of obtaining silica sol by ion-exchanging sodium silicate to prepare active silicic acid, and then condensing silicic acid species under basic conditions may also be used.

[0071] (2) Heating concentration process The method for producing colloidal silica of the present invention preferably includes a heating and concentration step, and concentrates the particle concentration by heating distillation. By including the heating and concentration step in the method for producing colloidal silica, fine particles of silica particles contained in the colloidal silica can be reduced.

[0072] In the heating and concentration step, the Pv value (stirring power per unit volume) is preferably 0.01kW / m 3 ~0.40kW / m 3 , more preferably 0.01kW / m 3 ~0.30kW / m 3 , still more preferably 0.01kW / m 3 ~0.20kW / m 3 , and most preferably 0.01kW / m 3 ~0.10kW / m 3 . By adjusting the Pv value of the heating and concentration treatment to preferably 0.40kW / m 3 or lower, the concentration and temperature of the silica particles can be homogenized, and by setting the Pv value to a certain value or lower, aggregation of silica particles can be suppressed.

[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 are... This method can reduce the amount of silica particles without significantly altering the average secondary particle size or degree of association.

[0074] (3) Heating water displacement process (production of silica sol consisting of water and silica particles) The colloidal silica subjected to heat treatment is preferably obtained by concentrating the silica particle concentration and replacing the solvent with water by heat distillation. By heat concentration and heat water replacement under the following conditions, the content of fine particles smaller than 15 nm can be reduced from the point before heat treatment. By heating and concentrating and replacing with heated water under the above conditions, colloidal silica with a low particulate matter content can be obtained by further heat-treating the resulting colloidal silica with an even lower particulate matter content under the same conditions.

[0075] The present invention's method for producing colloidal silica preferably includes a heated water substitution step, in which the solvent is replaced with water by heated distillation. By including the heated water substitution step in the method for producing colloidal silica, the amount of fine silica particles contained in the colloidal silica can be reduced.

[0076] In the heated water replacement step, the Pv value (stirring power per unit volume) is preferably 0.01 kW / m³. 3 ~0.40kW / m 3 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 for the heated water displacement treatment is preferably 0.40 kW / m². 3 By making the following adjustments, 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 heating water replacement time (minutes, min) in the heating water replacement step is preferably 60 to 600 minutes. By adjusting the heating water replacement time in the heating water replacement step to preferably 60 to 600 minutes, the silica This method can reduce the number of silica particles without significantly altering the average secondary particle size or degree of association of the silica particles.

[0078] In the heated water replacement step, the methanol concentration (ppm) after heated 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 heated water replacement to preferably 10,000 ppm or less, the silica particles contained in colloidal silica are finely divided. It can reduce the number of children.

[0079] (4) Heat treatment process (method for producing colloidal silica) The colloidal silica subjected to heat treatment is preferably obtained by concentrating the silica particle concentration and replacing the solvent with water by heating and distillation. By heating and concentrating and replacing the solvent with heated water, the content of fine silica particles smaller than 15 nm can be reduced from the point before heat treatment. By heat-treating the colloidal silica with a low content of fine silica particles obtained by heating and concentrating and replacing the solvent with heated water, it is possible to obtain colloidal silica with an even lower content of fine particles.

[0080] The present invention provides a method for producing colloidal silica, which includes a step of heating a silica sol, consisting of water and silica particles, at the boiling point of water under normal pressure. In this method for producing colloidal silica, the heat treatment reduces the number of fine silica particles contained in the colloidal silica.

[0081] In the heat treatment process, the heating temperature is set to the boiling point of water under reflux. By heating at the boiling point of water under reflux, it is possible to reduce the amount of silica particles without significantly changing the average secondary particle size or degree of association of the silica particles.

[0082] In the heat treatment process, the heating pressure is set to atmospheric pressure. By using atmospheric pressure during heating, it is possible to reduce the amount of silica particles without significantly changing the average secondary particle diameter or degree of association of the silica particles.

[0083] The pH of the silica sol during 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, etc.

[0085] The minimum pH value of the silica sol during heat treatment is preferably 9.0 or higher, and more preferably It is 9.2 or higher, more preferably 9.4 or higher, and most preferably 9.5 or higher. By adjusting the minimum pH of the silica sol during heat treatment to preferably 9.0 or higher, This can reduce the amount of fine silica particles contained in idal silica.

[0086] The maximum pH of the silica sol during 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 of the silica sol during heat treatment to preferably 10.5 or less, This can suppress the aggregation of licorice particles.

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

[0088] 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, 0.01 kW / m 3 ~0.30kW / m 3 And more preferably 0.01 kW / m 3 ~0.20kW / m 3 The most preferred value is 0.01 kW / m². 3 ~0.10kW / m 3 The Pv value during heat treatment is preferably 0.40 kW / m². 3 By making the following adjustments, 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 process, the heating time (hours, hr) is preferably 11 hr to 35 hr, more preferably 12 hr to 30 hr, even more preferably 14 hr to 28 hr, and most preferably 15 hr to 25 hr. By adjusting the heat treatment time to preferably 11 to 35 hours, it is possible to reduce the amount of fine silica particles without significantly changing the average secondary particle diameter and degree of association of the silica particles.

[0090] In the heat treatment process, the concentration of silica sol (mass %, wt%) 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%. Most preferably, the concentration is 8 wt% to 35 wt%. By adjusting the concentration of silica sol during heat treatment to preferably 2 wt% to 50 wt%, it is possible to reduce the amount of fine silica particles without significantly changing the average secondary particle size or degree of association of the silica particles.

[0091] [2] Colloidal silica This invention encompasses colloidal silica.

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

[0093] Definition of particulate matter content parameter 1 (i) Add ultrapure water with an electrical resistivity of 18.2 MΩ or higher (hereinafter referred to as "ultrapure water") to colloidal silica to dilute it to a silica concentration of 2% by mass (wt%) (diluted solution).

[0094] (ii) Place 9.1 g of the diluent into an Eppendorf Highmac Technologies centrifuge tube (model number: S303922A), and centrifuge it using a centrifuge rotor S58A and a centrifuge CS100FNX at a centrifugal speed of 50,000 rpm, a centrifugal temperature of 5°C, and a centrifugal time of 60 minutes (all manufactured by Eppendorf Highmac Technologies ).

[0095] (iii) After centrifugation, take 2 mL of the supernatant from the centrifuge tube, and mix this 2 mL of centrifugation supernatant with Fusoka Mix ultra-high-purity colloidal silica PL-3 manufactured by Gaku Kogyo Co., Ltd. with silica sol obtained by diluting it 10 times with ultrapure water in the following mass ratio (mixture).

[0096] Centrifuged supernatant: 10-fold dilution of PL-3 = 9:1 (mass ratio)

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

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

[0099] Equation (1) Particulate matter content parameter 1 = (Total number of particles detected that are 15 nm or smaller) ÷ (Total number of particles detected that are 25 nm or larger) 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 manufacturing method of the present invention as an abrasive, the amount of remaining fine particles on the polished surface is low. It is possible to significantly reduce the amount of material produced and to reduce the surface roughness of the polished surface.

[0101] The silica concentration (mass%, wt%) of colloidal silica is preferably 2wt% to 55wt%. More preferably, the silica concentration is 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 preferably 2 wt% to 55 wt%, the polishing rate is improved.

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

[0103] (1-1) Method for measuring particulate matter content parameter 1 (i) Dilute the colloidal silica sample to be measured by adding ultrapure water with an electrical resistivity of 18.2 MΩ or higher (hereinafter referred to as "ultrapure water") to a silica concentration of 2% by mass (wt%). liquid).

[0104] (ii) Place 9.1 g of the diluent into an Eppendorf Highmac Technologies centrifuge tube (model number: S303922A), and centrifuge it using a centrifuge rotor S58A and a centrifuge CS100FNX at a centrifugal speed of 50,000 rpm, a centrifugal temperature of 5°C, and a centrifugal time of 60 minutes (all manufactured by Eppendorf Highmac Technologies ).

[0105] (iii) After centrifugation, take 2 mL of the supernatant from the centrifuge tube, and mix this 2 mL of centrifugation supernatant with Fusoka Mix ultra-high-purity colloidal silica PL-3 manufactured by Gaku Kogyo Co., Ltd. with silica sol obtained by diluting it 10 times with ultrapure water in the following mass ratio.

[0106] Centrifuged supernatant: 10-fold dilution of PL-3 = 9:1 (mass ratio) The resulting mixture will be designated as sample 1.

[0107] (iv) The particle size distribution of sample 1 is measured using a particle size distribution measuring device based on the scanning electrical mobility diameter measurement method. An example of a particle size distribution measuring device based on the scanning electrical mobility diameter measurement method is the Liquid Nanoparticle Sizer System Model 9310 (LNS) manufactured by KANOMAX, and using the LNS... The measurement will be performed under the particle size distribution measurement conditions (1-2) described below.

[0108] (v) From the obtained particle size distribution measurements, the colloidal silica sample is calculated using the following formula. Calculate the particulate matter content parameter 1.

[0109] Equation (1) Particulate matter content parameter 1 = (Total number of particles detected that are 15 nm or smaller) ÷ (Total number of particles detected that are 25 nm or larger)

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

[0111] (ii) Measurements are taken for 24 hours or more while ultrapure water and the above-mentioned dry air are supplied to the LNS apparatus. A preliminary test run will be conducted.

[0112] (iii) Clean the inside of the measuring device with ultrapure water. Measure the particle concentration of the ultrapure water under the conditions shown in Table 1, and complete the cleaning when the total number of detected particles is less than 5.0E+11(# / mL).

[0113] (iv) Measurements will be performed using KANOMAX's LNS Volumetric Standard as the standard particle under the measurement conditions shown in Table 1.

[0114] (v) Clean the inside of the measuring device with ultrapure water. Measure the particle concentration of the ultrapure water under the conditions shown in Table 1, and complete the cleaning when the total number of detected particles is less than 1.0E+11(# / mL).

[0115] (vi) Perform the measurement of sample 1 under the measurement conditions shown in Table 1.

[0116] Colloidal silica has a particulate matter content parameter 1 of 15.0 or less, as measured by the measurement method described above.

[0117] Colloidal silica has a particulate matter content parameter 1 measured by the above-described measurement method that 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 particulate matter content parameter 1 to 15.0 or less, This reduces the amount of residual fine particles on the polished surface.

[0118] (2-1) Method for measuring particulate matter content parameter 2 (%) (i) Add ultrapure water with an electrical resistivity of 18.2 MΩ or higher (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% by mass (wt%). The resulting diluted solution will be designated as sample 2.

[0119] (ii) The particle size distribution of sample 2 is measured using a particle size distribution measuring device based on the scanning electrical mobility diameter measurement method. An example of a particle size distribution measuring device based on the scanning electrical mobility diameter measurement method is the Liquid Nanoparticle Sizer System Model 9310 (LNS) manufactured by KANOMAX, and using the LNS... The measurement will be performed under the particle size distribution measurement conditions described in (2-2) below.

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

[0121] Equation (3) Particulate matter content parameter 2 = (Total number of particles smaller than 15 nm detected) ÷ (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 air filter Purified dry air is used, produced by a filter (CKD, FCS500-88-P90).

[0123] (ii) Measurements are taken for 24 hours or more while ultrapure water and the above-mentioned dry air are supplied to the LNS apparatus. A preliminary test run will be conducted.

[0124] (iii) Clean the inside of the measuring device with ultrapure water. Measure the particle concentration of the ultrapure water under the conditions shown in Table 1, and complete the cleaning 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), the standard particle used was LNS Vol, manufactured by KANOMAX. Perform measurements using the Umetric Standard.

[0126] (v) Clean the inside of the measuring device with ultrapure water. Measure the particle concentration of the ultrapure water under the conditions shown in Table 1, and complete the cleaning when the total number of detected particles is less than 1.0E+11(# / mL).

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

[0128] Colloidal silica has a particulate matter content parameter 2, measured by the above-described measurement method, of 8.0% or less.

[0129] The colloidal silica has a fine particle content parameter 2 measured by the above-described measurement method that 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 fine particle content parameter 2 to 8.0% or less, the amount of remaining fine particles on the polished surface can be reduced.

[0130] [Table 1]

[0131] (3) Percentage of particulate matter amount evaluated by SEM (%) (i) A dispersion of 7.5 mL methanol, 1.5 mL water, 1 mL of 0.01 M HCl, and 5 μL of 20% colloidal silica is dropped onto a sample stage and allowed to dry. This sample stage is then scanned using a scanning electron microscope (SEM). Set it up and take an SEM image.

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

[0133] (iii) In the number frequency distribution of the elliptic minor axis obtained from the SEM image analysis described above, particles whose elliptic minor axis is 25% or less of the mean value are defined as microparticles, and the number proportion of microparticles is calculated.

[0134] The percentage of fine particles in colloidal silica, as evaluated by SEM, is preferably 0.1% or less. By adjusting the percentage of fine particles in roydal silica, as evaluated by SEM, to 0.1% or less, the polished surface The amount of residual particulate matter can be reduced.

[0135] (4) Average primary particle diameter (nm) Colloidal silica is pre-dried on a hot plate, then heat-treated at 800°C for 1 hour to prepare a sample for measurement. The BET specific surface area is measured using the prepared sample. Silica Assuming the true specific gravity is 2.2, 2727 / BET specific surface area (m 2 Convert the value ( / g) to the amount in colloidal silica This is the average primary particle diameter (nm) of the silica particles.

[0136] The average primary particle size of 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 size of colloidal silica is preferably adjusted to 5 nm to 130 nm. By doing so, the surface roughness of the polished surface can be reduced.

[0137] (5) Average secondary particle diameter (nm) Dilute colloidal silica by adding a 0.3% by mass citric acid aqueous solution to achieve a silica concentration of 1.0% by mass (wt%) (diluted solution).

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

[0139] The average secondary particle size (nm) of colloidal silica is preferably 20 nm to 250 nm, and more Preferably, the particle size is 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 surface 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 ratio of the average secondary particle diameter to the average primary particle diameter of the silica particles in colloidal silica.

[0141] The association ratio of silica particles in colloidal silica is preferably 1.0 or higher, and more preferably Or, 1.1 or higher, more preferably 1.2 or higher, and most preferably 1.3 or higher. Yes. By adjusting the lower limit of the association ratio of colloidal silica to 1.0 or higher, colloidal silica The polishing speed is further improved when using a polishing tool.

[0142] 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, colloidal silica can be used This can reduce the surface roughness of the polished surface.

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

[0144] The silica concentration of 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 colloidal silica to 2 wt% to 55 wt%, colloidal The polishing speed when polishing silica is improved.

[0145] (8) Silanol group density (particles / nm) 2 ) The silanol group density of colloidal silica can be determined by the Sears method. The Sears method was performed in reference to GWSears, Jr., “Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide”, Analytical Chemistry, 28(12), 1981(1956). A 1% by mass (wt%) silica dispersion was used for the measurement, and titration was performed with a 0.1 mol / L aqueous sodium hydroxide solution. The silanol group density was calculated based on the following formula.

[0146] ρ = (a × f × 60²²) ÷ (c × S) In the above formula, ρ: Silanol group density (number / nm 2 a: Droplet volume (mL) of 0.1 mol / L sodium hydroxide aqueous solution with pH 4-9, f: Factor of 0.1 mol / L sodium hydroxide aqueous solution, c: Silica particles Mass (g), S: BET specific surface area (m²) 2 / g) represents each respective part.

[0147] The silanol group density of silica particles in colloidal silica is preferably 1.5 groups / nm. 2 The above is more preferable, 1.6 pieces / nm 2 The above, and more preferably 1.8 particles / nm 2 The above is the most preferred, with 2.0 pieces / nm being the most preferable. 2 That concludes the explanation. The lower limit of silanol group density is 1.5 groups / nm. 2 By making the above adjustments, the occurrence of scratches on the workpiece is further reduced.

[0148] Furthermore, the silanol group density is preferably 10.0 groups / nm 2 The following, and more preferably, 9.5 particles / nm 2 The following, and more preferably 9.0 pieces / nm 2 The following is the most preferred, with 8.8 particles / nm. 2 The following applies: The upper limit for silanol group density is 10.0 groups / nm. 2The polishability of colloidal silica can be further improved by making the following adjustments.

[0149] (9) True specific gravity In this specification, true specific gravity is defined as the amount of colloidal silica after drying on a hot plate at 150°C. After being held in a 300°C furnace for one hour, it can be measured using a liquid-phase displacement method with ethanol.

[0150] The true specific gravity of the silica particles contained in colloidal silica is preferably 1.0 or higher. More preferably, it is 1.2 or higher, even more preferably, 1.4 or higher, and most preferably, 1.5 That concludes the explanation. By adjusting the lower limit of the true specific gravity to 1.0 or higher, the colloidal silica of the present invention Polishing performance is further improved.

[0151] 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. The upper limit of the true specific gravity is 3.0 or less. By making these adjustments, the occurrence of scratches on the workpiece is further reduced.

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

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

[0154] (11) Polished surface roughness RMS (nm) Ultrapure water is added to colloidal silica so that the silica concentration is 3.0% by mass (wt%) to obtain a diluted polishing composition.

[0155] Using the obtained polishing composition, a 3 cm square silicon wafer having a silicon oxide film formed on the surface thereof is polished under the following conditions.

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

[0157] Atomic force microscope: SPM-9700HT, manufactured by Shimadzu Corporation Cantilever: MICRO CANTILEVER OMCL-AC240TS-R3, manufactured by OLYMPUS Observation mode: Dynamic mode Scanning range: 3.0 μm square Scanning speed: 1.00 Hz Number of observation fields of view: 5 fields of view are observed per polished wafer.

[0158] Calculation method of surface roughness: The average value of the root mean square roughness of 5 fields of view is 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 remaining fine particles on the polished surface (particles / μm 2 ) Ultrapure water is added to colloidal silica to achieve a silica concentration of 3.0% by mass (wt%). Dilute to make an abrasive composition.

[0161] Using the obtained polishing composition, a 3 cm square silicon dioxide film is formed on the surface of the silicon dioxide film. Polish the con wafer under the following conditions.

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

[0163] Brush: AION SCL BRUSH ROLLER 48 (40 / 26) x 224 mm (manufactured by AION Corporation) Scrub cleansing time: 1 min Brush rotation speed: 200 rpm Spin rotation speed of the silicon wafer fixing part: 50 rpm After scrubbing, ultrapure water is flowed over the polished substrate at a rate of 750 mL / min for 1 minute, and then the substrate is further processed at 1800 rpm for 20 seconds using the spin dryer built into the above apparatus.

[0164] For silicon wafers after drying, the number of remaining fine particles on the polished surface is measured using a Shimadzu SPM-9700HT.

[0165] Number of remaining fine particles on the polished surface (particles / μm) 2 Preferably, 3 particles / μm 2 The following applies:

[0166] [4] Polishing composition The present invention encompasses polishing compositions containing colloidal silica.

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

[0168] The polishing composition may contain colloidal silica and may further contain additives. Examples of additives include diluents, oxidizing agents, pH adjusters, corrosion inhibitors, stabilizers, and surfactants.

[0169] The colloidal silica content (mass%, wt%, silica concentration) in the polishing composition 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 embodiments of the present invention have been described above, the present invention is not limited in any way to these examples. Naturally, the present invention can be implemented in various forms without departing from the spirit of the invention. [Examples]

[0171] The present invention will be specifically described with reference to examples.

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

[0173] [1] Production of colloidal silica (1) Example 1 (with heat treatment) Preparation of silica sol by heating and water substitution Solution A, prepared by mixing 976g methanol, 97g water, and 58g 29% by mass aqueous ammonia, is mixed with Solution B, prepared by mixing 190g methanol and 506g tetramethoxysilane (TMOS), and 119g 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 is maintained at 35°C, and the temperature of the reaction solution is adjusted so that it decreases 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), while preparing the solution A The entire amounts of solution B and solution C were added to the mixture at a constant rate.

[0175] The reaction solution was heated and concentrated under stirring conditions, and then replaced with heated water. The methanol concentration after replacing with heated water was 301 ppm.

[0176] Manufacturing of colloidal silica (heat treatment) To 100 parts by mass of the heated water-substituted silica sol obtained above, add 3-ethoxypropyl 0.65 parts by mass of amine (3-EOPA) were added, the pH was adjusted to 9.9, and the silica sol was stirred under these conditions. The silica sol was then heated to 100°C under atmospheric pressure. The heat treatment began when the silica sol reached 100°C, and samples were taken every 0.5 hours from the start of the heat treatment, with pH measurements performed.

[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 were added again. The pH was adjusted to 9.9. The above procedure was performed every 1.5 hours from the start to the end of the heat treatment. 2.2 parts by mass of 3-EOPA were added from the start to the end of the heat treatment.

[0178] The above 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 equivalent or better), and an air compressor (capable of supplying compressed air at 0.4 MPa or higher) were used. 1 μL of sample was withdrawn into a 10 μL syringe and then fed into the autosampler. The device was set up and the measurement was performed.

[0180] (2) Example 2 (with heat treatment) Preparation of silica sol by heating and water substitution Solution A, prepared by mixing 7.7 g of pure water, 96.8 g of methanol, and 4.5 g of 29% by mass aqueous ammonia, was then mixed with Solution B, prepared by mixing 100 g of TMOS and 17.7 g of methanol, and Solution C, prepared by mixing 31.7 g of pure water and 4.7 g of 29% by mass aqueous ammonia, at a constant rate over 217 minutes while maintaining the liquid temperature at 36°C.

[0181] After the addition was complete, the reaction solution was stirred for another 30 minutes while maintaining its temperature at 36°C.

[0182] The reaction mixture was heated and concentrated under stirring conditions, and then replaced with heated water. The methanol concentration after replacing with heated water was 212 ppm.

[0183] Manufacturing of colloidal silica (heat treatment) To 100 parts by mass of the silica sol obtained above by replacing it with heated water, 0.6 parts by mass of 3-EOPA was added, the pH was adjusted to 9.8, and the silica sol was heated at 100°C under atmospheric pressure while being stirred. The heating treatment was started when the silica sol reached 100°C, and samples were taken every 0.5 hours from the start of the heating treatment, and the pH was measured.

[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 were added again to adjust the pH to 9.8. This procedure was repeated every 1.0 hour from the start to the end of the heat treatment. A total of 2.76 parts by mass of 3-EOPA were added from the start to the end of the heat treatment.

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

[0186] (3) Example 3 (Example with heat treatment and small average particle size) Preparation of silica sol by heating and water substitution Solution A, prepared by mixing 463.1 g of pure water, 104.8 g of 26% by mass aqueous ammonia, and 4255.0 g of methanol, was then mixed with Solution B, prepared by mixing 3,044.4 g of TMOS and 229.4 g of methanol, and Solution C, prepared by mixing 643.2 g of pure water and 104.8 g of 26% by mass aqueous ammonia, 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 conditions, and then replaced with heated water. The methanol concentration after replacement with heated water was The concentration was 198 ppm.

[0188] Manufacturing of colloidal silica (heat treatment) To 100 parts by mass of the heated water-substituted silica sol obtained above, add 0.65 parts by mass of 3-EOPA. The silica sol was added, the pH was adjusted to 9.9, and the silica sol was heated at 100°C under atmospheric pressure while being stirred. The heat treatment was started when the silica sol reached 100°C, and samples were taken 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 were added again. The pH was adjusted to 9.9. The above procedure was performed every 1.0 hour from the start to the end of the heat treatment. 3.2 parts by mass of 3-EOPA were added from the start to the end of the heat treatment.

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

[0191] (4) Example 4 (Example with heat treatment and large average particle size) Preparation of silica sol by heating and water substitution To solution A obtained by mixing 1546.6 g of pure water, 340.6 g of 26 mass% ammonia water, and 8363.2 g of methanol, solution B obtained by mixing 6088.0 g of TMOS and 350.0 g of methanol, and solution C obtained by mixing 1186.2 g of pure water and 340.6 g of 26 mass% ammonia water were added at a constant rate over 100 minutes while maintaining the liquid temperature at 20°C.

[0192] The reaction solution was heated to concentration and subjected to heated water replacement under stirring conditions. The methanol concentration after heated water replacement was 196 ppm.

[0193] Manufacturing of colloidal silica (heat treatment) Based on 100 parts by mass of the silica sol that has undergone heated water replacement obtained above, 0.65 parts by mass of 3-EOPA was added, the pH was adjusted to 9.9, and the silica sol was heated at 100°C under normal pressure conditions while being stirred. The time point when the silica sol reached 100°C was defined as the start of heat treatment, and 0.25 sampling was performed every hour, and pH measurement was carried out.

[0194] After 0.25 hours had elapsed from the start of heat treatment, the pH had become 9.7, so 0.15 parts by mass of 3-EOPA was re-add ed to adjust the pH to 9.9. The above operation was performed every 1.0 hour from the start of heat treatment to the end of heat treatment. A total of 3.0 parts by mass of 3-EOPA was added from the start of heat treatment to the end of heat treatment.

[0195] The above heat treatment was performed for 20.0 hours to obtain colloidal silica.

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

[0197] Manufacturing of colloidal silica (heat treatment) To 100 parts by mass of the heated water-substituted silica sol obtained above, add 0.65 parts by mass of 3-EOPA. The silica sol was added, the pH was adjusted to 9.9, and the silica sol was heated at 100°C under atmospheric pressure while being stirred. The heat treatment was started when the silica sol reached 100°C, and samples were taken 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 were added again. The pH was adjusted to 9.9. The above procedure was performed every 1.5 hours from the start to the end of the heat treatment. 2.4 parts by mass of 3-EOPA were added from the start to the end of the heat treatment.

[0199] The above 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 silica sol by heating and water substitution The reaction solution obtained in Example 1 was heated and concentrated under stirring conditions and then replaced with heated water. The methanol concentration was 184 ppm.

[0201] Manufacturing of colloidal silica (heat treatment) To 100 parts by mass of the heated water-substituted silica sol obtained above, add 0.65 parts by mass of 3-EOPA. The silica sol was added, the pH was adjusted to 9.9, and the silica sol was heated at 100°C under atmospheric pressure while being stirred. The heat treatment was started when the silica sol reached 100°C, and samples were taken every 0.5 hours from the start of the heat treatment, and the pH was measured.

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

[0203] The above 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 simulating prior art (Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-164351, and Patent Document 3: International Publication No. WO2016 / 117560A1).

[0205] With respect to a solution A prepared by mixing 97 g of water and 58 g of 29 mass% aqueous ammonia into 976 g of methanol, solution B prepared by mixing 190 g of methanol and 506 g of tetramethoxysilane (TMOS), and 119 g of pure water and solution C (pH=7.85) were added at a constant rate over 75 minutes.

[0206] In the preparation of the reaction liquid, the temperature of each liquid before mixing was maintained at 35°C, and the temperature of the reaction liquid was changed from an initial reaction temperature of 35°C at the start of addition of the solution B to the solution A (at the start of synthesis) to the entire amounts of the solution B and the solution C were added at a constant rate to the solution A while adjusting the temperature so that the temperature decreased to a final reaction temperature of 24.5°C at the end of synthesis (at the end of addition).

[0207] The reaction liquid was subjected to heating concentration and heating water replacement under stirring conditions to obtain colloidal silica.

[0208] (8) Comparative Example 2 (without heat treatment) This is an example simulating prior art (Patent Document 2: Japanese Unexamined Patent Application Publication No. 2022-109711, and Patent Document 3) .

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

[0210] After the addition was complete, the reaction solution was stirred for another 30 minutes while maintaining its temperature at 36°C.

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

[0212] (9) Comparative Example 3 (without heat treatment) This is an example that simulates the prior art (Patent Documents 2-3 and Patent Document 4: Japanese Patent Publication No. 2020-75830). ru.

[0213] Colloidal silica was obtained by adding 35% by mass of hydrogen peroxide to the colloidal silica obtained in Comparative Example 2, such that the hydrogen peroxide content was 0.5 g per 100 g of tetraalkoxysilane in silica equivalent.

[0214] (10) Comparative Example 4 (without heat treatment) This is an example that simulates prior art (Patent Documents 2-4 and Patent Document 5: Japanese Unexamined Patent Publication No. 2021-116208).

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

[0216] The amount of liquid that passed through the ultrafiltration membrane was 63.6 g, and the transmittance was 53%.

[0217] (11) Comparative Example 5 (Example of ultrafiltration without heat treatment and for a long period of time) This is an example that simulates prior art (Patent Documents 2-5).

[0218] 40 g of colloidal silica obtained in Comparative Example 4 was used in an Asahi Kasei pencil-type module (PX-02001) with an ultrafiltration membrane having a molecular weight cutoff of 80,000 (Asahi Kasei Lab Module AOP-0013). 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), and the tubing uses Masterflex silicone peroxide. Colloidal silica was obtained by ultrafiltration using a decomposition tube (96400-25).

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

[0220] The volume of liquid that passed through 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 silica produced by a method for producing colloidal silica that includes a step of heating 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 used in the example was able to keep the content of fine particles low.

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

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

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

[0230] Comparative Example 3 is an example that simulates Patent Documents 2-4, and effectively reduces fine particles smaller than 15 nm. I was unable to do so.

[0231] Comparative Example 4 is an example that simulates Patent Documents 2-5, and effectively reduces fine particles smaller than 15 nm. I was unable to do so.

[0232] Comparative Example 5 simulates Patent Documents 2-5 and aims to reduce the amount of particulate matter by performing ultrafiltration for a long period of time. This was an example in which an increase in the average secondary particle diameter due to particle aggregation was confirmed.

[0233] [3] Industrial applicability The present invention provides a method for producing colloidal silica, which includes a step of heating 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 particulate matter content parameter 1 (i) Add ultrapure water with an electrical resistivity of 18.2 MΩ or higher (hereinafter referred to as "ultrapure water") to colloidal silica to dilute it to a silica concentration of 2% by mass (wt%) (diluted solution).

[0236] (ii) Place 9.1 g of the diluent into an Eppendorf Highmac Technologies centrifuge tube (model number: S303922A), and centrifuge it using a centrifuge rotor S58A and a centrifuge CS100FNX at a centrifugal speed of 50,000 rpm, a centrifugal temperature of 5°C, and a centrifugal time of 60 minutes (all manufactured by Eppendorf Highmac Technologies ).

[0237] (iii) After centrifugation, take 2 mL of the supernatant from the centrifuge tube, and mix this 2 mL of centrifugation supernatant with Fusoka Mix ultra-high-purity colloidal silica PL-3 manufactured by Gaku Kogyo Co., Ltd. with silica sol obtained by diluting it 10 times with ultrapure water in the following mass ratio (mixture).

[0238] Centrifuged supernatant: 10-fold dilution of PL-3 = 9:1 (mass ratio) (iv) The particle size distribution of the obtained mixture is measured using a particle size distribution measuring device based on the scanning electrical mobility diameter measurement method.

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

[0240] Equation (1) Particulate matter content parameter 1 = (Total number of particles detected that are 15 nm or smaller) ÷ (Total number of particles detected that are 25 nm or larger) The colloidal silica of the present invention has a low content of fine particles.

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

Claims

[Claim 1] colloidal silica, The percentage of particulate matter evaluated by a scanning electron microscope (SEM) as defined below is 0.1% or less. Colloidal silica with an average secondary particle diameter of 20 nm to 69.3 nm. Definition of the percentage of particulate matter evaluated by SEM (i) A dispersion of 7.5 mL methanol, 1.5 mL water, 1 mL of 0.01 M HCl, and 5 μL of 20% colloidal silica is dropped onto the sample stage and allowed to dry. This sample stage is then placed in the SEM and an SEM image is taken. (ii) Images of 1,000 silica particles taken with SEM are approximated as ellipses using image analysis software (Mitani Corporation's "WinRoof2018"), and the minor axis of the ellipse is measured. (iii) In the number frequency distribution of the elliptic minor axis obtained from the SEM image analysis described above, particles whose elliptic minor axis is 25% or less of the average value are defined as microparticles, and the number proportion of microparticles is calculated.

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