Colloidal silica and its manufacturing method

Abstract

This invention provides a colloidal silica that, when used as an abrasive for grinding, does not easily leave silica particles on the grinding surface and can form a grinding surface with reduced surface roughness. The colloidal silica is formed by dispersing silica particles in a solvent, characterized in that the true specific gravity of the silica particles based on a liquid-phase displacement method is 1.60 or more and 2.20 or less, and the value of the composite parameter 1 calculated by a specific formula is 10 or more and 200 or less.

Description

Technical Field

[0001] This invention relates to colloidal silicon dioxide and a method for manufacturing colloidal silicon dioxide. Prior Technology

[0002] Colloidal silica is obtained by dispersing silica particles in a medium such as water. In addition to being used as a property modifier in the fields of paper, fiber, and steel, it is also used as a raw material for polishing compositions used in chemical mechanical polishing (CMP) of semiconductor wafers and other semiconductor devices.

[0003] In CMP (Continuous Polishing) during the manufacturing process of semiconductor devices, the surface of the polished substrate needs to be smoothed at the nanometer level. If the smoothing of the substrate surface is insufficient, that is, if the surface of the polished substrate is rough, it is easy to cause wire breakage and short circuit, which can easily damage the reliability of the electrical connection of the semiconductor.

[0004] In addition, since silicon dioxide particles remain on the surface of the substrate after polishing, the yield is easily reduced. Therefore, a polishing composition that can smooth the substrate surface with high precision and prevent particles from remaining on the substrate surface is required.

[0005] As a method for manufacturing colloidal silica that does not easily leave silica particles on the surface of a polished substrate, Patent Document 1 discloses a method for adjusting the addition of an alkaline catalyst during the synthesis of silica particles based on the hydrolysis and condensation reaction of alkoxysilanes. The concentration of Si in the solvent of colloidal silica is controlled as an indicator of the concentration of silica-containing compounds, thereby enabling the manufacture of colloidal silica that does not easily remain on the surface of a substrate.

[0006] In addition, as a method for manufacturing colloidal silica that does not easily leave silica particles on the surface of a polished substrate, Patent Document 2 discloses that after synthesizing silica particles by hydrolysis and condensation reaction of alkoxysilanes, a pressure heating treatment is performed (specifically, a heating treatment at 140~200°C under pressure conditions in the examples) to control the density of silanol groups on the particle surface, thereby enabling the manufacture of colloidal silica that does not easily leave silica particles on the surface of a substrate. [Previous Technical Documents] [Patent Literature]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2021-054684 [Patent Document 2] Japanese Patent Application Publication No. 2020-183329 Summary of the Invention

[0008] [The technical problem that the invention aims to solve] However, the inventors of this invention conducted research and determined that even when using colloidal silica obtained by the manufacturing method described in Patent Document 1, it is difficult to obtain a grinding composition in which silica particles are not easily retained on the grinding surface. This is believed to be because, from the perspective of particle dispersion stability, most grinding compositions using colloidal silica as raw material are adjusted to be alkaline. Silica particles are usually easy to dissolve in an alkaline environment. Therefore, in order to prepare grinding compositions in which silica particles do not easily remain on the substrate surface, colloidal silica with controlled Si concentration in the solvent under alkaline conditions is required.

[0009] Furthermore, the inventors of this invention conducted research and determined that although the polishing composition using colloidal silica obtained by the manufacturing method described in Patent Document 2 does not easily leave silica particles on the polishing surface, it is difficult to obtain a polishing surface with reduced surface roughness. It is believed that this is because the true specific gravity of colloidal silica particles obtained by high-temperature and high-pressure treatment using an autoclave, as described in Patent Document 2, increases, and the mechanical strength is easily increased. Therefore, when used in grinding compositions, the flatness of the grinding surface is easily damaged.

[0010] The purpose of this invention is to provide colloidal silica that, when used as abrasive grains for grinding, does not easily leave silica particles on the grinding surface and can form a grinding surface with reduced surface roughness, as well as a method for manufacturing colloidal silica. [Technical means]

[0011] In order to solve the above-mentioned technical problems, the inventors of the present invention conducted in-depth research and found that a novel colloidal silica, which is formed by dispersing silica particles in a solvent, has a true specific gravity of 1.60 or more and 2.20 or less based on the liquid phase displacement method, and a composite parameter 1 defined by a specific formula has a value of 10 or more and 200 or less, can solve the above-mentioned technical problems. Based on this insight, the present invention was completed.

[0012] That is, the present invention lies in, (1) A colloidal silicon dioxide, which is a colloidal silicon dioxide formed by dispersing silicon dioxide particles in a solvent, characterized in that, The true specific gravity of the aforementioned silicon dioxide particles based on the liquid-phase displacement method is above 1.60 and below 2.20. The value of the composite parameter 1 calculated by the following formula (1) is 10 or more and 200 or less. Wherein, A: the silica concentration (ppm) in the solvent after the silica particle concentration is set to 10% by mass, the pH is adjusted to 10.5 and left for 24 hours; B: the silanol group density of the aforementioned silica particles (units / nm2) determined by the Sears method; and C: the average secondary particle size (nm) of the aforementioned silica particles determined by dynamic light scattering method. (2) According to the colloidal silicon dioxide described in (1) above, wherein the average secondary particle size of the silicon dioxide particles measured by the aforementioned dynamic light scattering method is 3~200 nm. (3) The colloidal silicon dioxide according to (1) or (2) above, wherein the content of metallic impurities is less than 1 ppm by mass. And, (4) A method for manufacturing colloidal silicon dioxide, comprising a method for manufacturing the colloidal silicon dioxide described in any one of (1) to (3) above, characterized in that, The aforementioned method for manufacturing colloidal silicon dioxide includes: The reaction procedure involves contacting a mother liquor containing an alkaline catalyst, water, and alcohol with a starting material solution containing alcohol and tetraalkoxysilane to obtain a reaction solution; and The maturation process involves adjusting the reaction solution obtained in the aforementioned reaction process to a water concentration of 0-6% by mass, and then heating and stirring at atmospheric pressure and a temperature of 55-65°C for more than 50 hours. (5) The method for manufacturing colloidal silica according to (4) above, wherein the alkaline catalyst is ammonia, the alcohol in the mother liquor is methanol, the alcohol in the raw material solution is methanol, and the tetraalkoxysilane is tetramethoxysilane. [Effects of the Invention]

[0013] According to the present invention, a colloidal silica that, when used as an abrasive for grinding, does not easily leave silica particles on the grinding surface and can form a grinding surface with reduced surface roughness, and a method for manufacturing colloidal silica, are provided. Implementation

[0014] First, the colloidal silicon dioxide involved in this invention will be described. The colloidal silica involved in this invention is a colloidal silica formed by dispersing silica particles in a solvent, characterized in that... The true specific gravity of the aforementioned silicon dioxide particles based on the liquid-phase displacement method is above 1.60 and below 2.20. The value of the composite parameter 1 calculated by the following formula (1) is 10 or more and 200 or less. Wherein, A: the silica concentration (ppm) in the solvent after the silica particle concentration is set to 10% by mass, the pH is adjusted to 10.5 and left for 24 hours; B: the silanol group density of the aforementioned silica particles (units / nm2) determined by the Sears method; and C: the average secondary particle size (nm) of the aforementioned silica particles determined by dynamic light scattering method.

[0015] In the colloidal silica involved in this invention, the true specific gravity of the silica particles constituting the colloidal silica based on the liquid phase displacement method is 1.60 or more and 2.20 or less, ideally 1.70 or more and 2.18 or less, and more ideally 1.75 or more and 2.15 or less.

[0016] In the colloidal silica of the present invention, by ensuring that the true specific gravity of the silica particles constituting the colloidal silica, based on the liquid-phase displacement method, is within the above-mentioned range, when the colloidal silica of the present invention is used as abrasive grains for grinding, it can exhibit excellent abrasiveness and easily form a grinding surface with reduced surface roughness.

[0017] Furthermore, in this application, the true specific gravity based on the liquid phase displacement method refers to the value determined by using ethanol after the test sample has been dried on a hot plate at 150°C, heated in a furnace at 300°C for 1 hour.

[0018] In the colloidal silicon dioxide involved in this invention, the value of the composite parameter 1 calculated by the following formula (1) is 10 or more and 200 or less. Wherein, A: the silica concentration (ppm) in the solvent after the silica particle concentration is set to 10% by mass, the pH is adjusted to 10.5 and left for 24 hours; B: the silanol group density of the aforementioned silica particles (units / nm2) determined by the Sears method; and C: the average secondary particle size (nm) of the aforementioned silica particles determined by dynamic light scattering method.

[0019] In the colloidal silicon dioxide involved in this invention, the composite parameter 1 is 200 or less, ideally 185 or less, more ideally 155 or less, and even more ideally 100 or less. By setting the composite parameter 1 to a value below the above (upper limit), when using the colloidal silicon dioxide involved in this invention as abrasive grains for grinding, the number of particles remaining on the grinding surface can be suppressed.

[0020] In the colloidal silicon dioxide involved in this invention, the composite parameter 1 is 10 or more, ideally 19 or more, more ideally 24 or more, and even more ideally 35 or more. By setting the composite parameter 1 to a value above the aforementioned (lower limit), the flatness of the grinding surface can be further improved when the colloidal silicon dioxide involved in this invention is used as a grinding abrasive.

[0021] It is believed that when colloidal silica is used as abrasive grains for grinding, the silica particles constituting the colloidal silica bind to the grinding surface via silanol groups on the particle surface as reaction sites, thus remaining on the grinding surface. It is believed that the binding of these silica particles to the grinding surface is promoted by silicon (Si) compounds dissolved in a solvent. Furthermore, it is believed that the dissolution of silica particles is promoted under alkaline conditions, thus further promoting the binding of these silica particles to the grinding surface under alkaline conditions. In addition, there is a tendency that the smaller the particle size of the silica particles that make up colloidal silica, the easier it is for them to remain on the polishing surface.

[0022] Based on the above background, the inventors of the present invention conducted in-depth research and found that when the composite parameter 1 shown in the following formula (1) is controlled to be low within a predetermined range, the silica particles are less likely to remain on the grinding surface when the colloidal silica is used as abrasive grains for grinding. Wherein, A: the silica concentration (ppm) in the solvent after the silica particle concentration is set to 10% by mass, the pH is adjusted to 10.5 and left for 24 hours; B: the silanol group density of the aforementioned silica particles (units / nm2) determined by the Sears method; and C: the average secondary particle size (nm) of the aforementioned silica particles determined by dynamic light scattering method.

[0023] In the colloidal silica involved in this invention, "A" constituting composite parameter 1 refers to the silica concentration (mass ppm) in the solvent after the silica particle concentration is set to 10% by mass, the pH is adjusted to 10.5, and 24 hours have passed. The concentration of silicon dioxide particles in the solvent after the concentration of the silicon dioxide particles is set to 10% by mass, the pH is adjusted to 10.5, and 24 hours have passed represents the solubility of the silicon dioxide particles under alkaline conditions. In the colloidal silica involved in this invention, the silica concentration "A" in the solvent after the silica particle concentration is set to 10% by mass, the pH is adjusted to 10.5, and after 24 hours is ideally 5 ppm by mass or more and 400 ppm by mass or less.

[0024] In the colloidal silica involved in this invention, the silica concentration "A" in the solvent after the silica particle concentration is set to 10% by mass and the pH is adjusted to 10.5 and after 24 hours is ideally 400 ppm by mass or less, more ideally 350 ppm by mass or less, even more ideally 300 ppm by mass or less, and particularly ideally 275 ppm by mass or less.

[0025] In the colloidal silica involved in this invention, by setting the silica particle concentration to 10% by mass and adjusting the pH to 10.5, and after 24 hours, the silica concentration "A" in the solvent is below the above value (upper limit value), thereby easily suppressing the residue of silica particles on the grinding surface when the colloidal silica involved in this invention is used as abrasive for grinding.

[0026] In the colloidal silica involved in this invention, the silica concentration "A" in the solvent after the silica particle concentration is set to 10% by mass and the pH is adjusted to 10.5 and after 24 hours is ideally 5 ppm by mass or more, more ideally 20 ppm by mass or more, even more ideally 40 ppm by mass or more, and particularly ideally 60 ppm by mass or more.

[0027] In the colloidal silica involved in this invention, when the silica particle concentration is set to 10% by mass, the pH is adjusted to 10.5, and the silica concentration "A" in the solvent is above the above value (lower limit value) after 24 hours, the grinding performance can be further improved when the colloidal silica involved in this invention is used as abrasive grains for grinding.

[0028] Furthermore, in this application, the silicon concentration "A" (mass ppm) in the solvent after the silicon dioxide particle concentration is set to 10% by mass and the pH is adjusted to 10.5 and after 24 hours refers to the value calculated by the following method. First, the colloidal silica was diluted with an alkaline catalyst such as ultrapure water or ammonia to set the silica particle concentration to 10% by mass and adjust the pH to 10.5. Next, the colloidal silica with a silica particle concentration of 10% by mass and a pH of 10.5 was placed in an incubator at 25°C and removed after 24 hours. 10 mL of colloidal silicon dioxide taken from the incubator was transferred to a centrifuge tube and centrifuged at 260,000 G for 2 hours. Then, 2 mL of supernatant was collected from the top of the centrifuge tube. The silicon concentration (silicon atom concentration) in the obtained supernatant was determined using the absolute standard curve method and an inductively coupled plasma optical emission spectrometry (ICP-AES) instrument. The obtained value was taken as the silicon concentration "A" (mass ppm) in the solvent.

[0029] In the colloidal silica involved in this invention, "B" constituting composite parameter 1 refers to the density of silanol groups (numbers / nm2) of silica particles as determined by the Sears method. In the colloidal silica involved in this invention, the silanol group density "B" of the silica particles, as determined by the Sears method, is ideally 1.5 or more per nm² and 10.0 or less per nm².

[0030] In the colloidal silica involved in this invention, the silanol group density "B" (numbers / nm2) of the silica particles determined by the Sears method is ideally 10.0 numbers / nm2 or less, more ideally 9.5 numbers / nm2 or less, even more ideally 9.0 numbers / nm2 or less, and particularly ideally 8.8 numbers / nm2 or less.

[0031] In the colloidal silica involved in this invention, the silanol group density "B" of the silica particles, as determined by the Sears method, is below the above-mentioned value (upper limit value), thereby making it easy to suppress the residue of silica particles on the grinding surface when the colloidal silica involved in this invention is used as abrasive grains for grinding.

[0032] In the colloidal silica involved in this invention, the silanol group density "B" (numbers / nm2) of the aforementioned silica particles, as determined by the Sears method, is ideally 1.0 or more per nm2, more ideally 1.5 or more per nm2, even more ideally 1.7 or more per nm2, and particularly ideally 2.0 or more per nm2.

[0033] In the colloidal silica involved in this invention, the silanol group density "B" of the aforementioned silica particles, as determined by the Sears method, is at or above the aforementioned value (lower limit value), thereby further improving the grinding performance when the colloidal silica of this invention is used as abrasive grains for grinding.

[0034] Furthermore, in this application, the silanol group density "B" (units / nm2) of silicon dioxide particles determined by the Sears method refers to the value calculated by the following method. That is, it refers to the Sears method described in GWSears, Jr., “Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide”, Analytical Chemistry, 28(12), 1981(1956)., in which the concentration of colloidal silica particles to be measured is adjusted to 1% by mass, and the silanol group density “B” (numbers / nm2) is calculated based on the following formula during titration with 0.1 mol / L sodium hydroxide aqueous solution. B = (a × f × 6022) ÷ (c × S) B: Silicon alcohol group density (numbers / nm2) a: Volume (mL) of 0.1 mol / L sodium hydroxide aqueous solution with pH 4 to pH 9. f: Factor of 0.1 mol / L sodium hydroxide aqueous solution c: Mass of silicon dioxide particles (g) S: BET specific surface area (m2 / g)

[0035] In the colloidal silica involved in this invention, "C" constituting composite parameter 1 refers to the average secondary particle size (nm) of silica particles measured by dynamic light scattering method. In the colloidal silica involved in this invention, the average secondary particle size "C" of the silica particles, as determined by dynamic light scattering, is ideally above 3 nm and below 200 nm.

[0036] In the colloidal silica involved in this invention, the average secondary particle size "C" (nm) of the silica particles, as determined by dynamic light scattering, is ideally less than 200 nm, more ideally less than 175 nm, even more ideally less than 150 nm, and particularly ideally less than 100 nm.

[0037] In the colloidal silica involved in this invention, the average secondary particle size "C" of the silica particles, as measured by dynamic light scattering, is below the above-mentioned value (upper limit value). Therefore, when the colloidal silica involved in this invention is used as abrasive grains for grinding, the flatness of the grinding surface is easily improved.

[0038] In the colloidal silica involved in this invention, the average secondary particle size "C" (nm) of the aforementioned silica particles, as determined by dynamic light scattering method, is ideally 3 nm or more, more ideally 5 nm or more, even more ideally 8 nm or more, and particularly ideally 10 nm or more.

[0039] In the colloidal silica involved in this invention, the average secondary particle size "C" of the silica particles, as determined by dynamic light scattering, is at or above the aforementioned value (lower limit value). Therefore, when the colloidal silica involved in this invention is used as abrasive grains for grinding, the grinding performance can be further improved.

[0040] Furthermore, in this application, the average secondary particle size "C" (nm) of the aforementioned silicon dioxide particles, determined by dynamic light scattering, refers to the value calculated by the following method. That is, firstly, 0.3% by mass of citric acid aqueous solution is added to colloidal silica to dilute it to a silica concentration of 0.8% by mass, and the resulting diluted solution is used as the sample for determination. Using the above-mentioned sample, the average particle size (nm) of the silicon dioxide particles was determined by dynamic light scattering using the "ELSZ-2000S" Zeta potential, particle size and molecular weight measurement system manufactured by Otsuka Electronics Co., Ltd.

[0041] Furthermore, the average primary particle size of the silica particles contained in the colloidal silica involved in this invention refers to the value determined by the BET method described below. First, colloidal silicon dioxide was pre-dried on a hot plate at 150°C and then heat-treated at 800°C for 1 hour to prepare a sample for measurement. The specific surface area (BET specific surface area) S' based on the BET method was measured using the obtained sample. In roughly spherical particles, the average primary particle size (nm) is calculated by the following formula. Average primary particle size (nm) = 6000 / (BET specific surface area S' (m2 / g) × true density (g / cm3)) The true density of silicon dioxide particles is set to 2.20 g / cm3, and the average primary particle size (nm) of silicon dioxide particles can be calculated by the following formula. The average primary particle size (nm) of silicon dioxide particles = 2727 / BET specific surface area S' (m2 / g)

[0042] In the colloidal silica involved in this invention, the agglomeration ratio of silica particles calculated by the following formula is ideally 1.0 or more and 3.0 or less. Agglomeration ratio = Average secondary particle size of silicon dioxide particles (nm) ÷ Average primary particle size of silicon dioxide particles (nm)

[0043] In the colloidal silica involved in this invention, the agglomeration ratio of silica particles is ideally 3.0 or less, more ideally 2.8 or less, and even more ideally 2.5 or less. In the colloidal silica involved in this invention, by making the agglomeration ratio below the above-mentioned value (upper limit value), the flatness of the grinding surface can be easily improved when the colloidal silica involved in this invention is used as abrasive grains for grinding.

[0044] In the colloidal silica involved in this invention, the agglomeration ratio of silica particles is ideally 1.0 or more, more ideally 1.2 or more, and even more ideally 1.4 or more. In the colloidal silica involved in this invention, by making the agglomeration ratio of silica particles at or above the above-mentioned value (lower limit value), the grinding performance when the colloidal silica involved in this invention is used as abrasive grains for grinding can be easily improved.

[0045] The pH of the colloidal silica involved in this invention can be set appropriately according to its application, without any particular limitation, but ideally it is above 2.0 and below 11.0.

[0046] The colloidal silicon dioxide involved in this invention has an ideal pH of 2.0 or higher, more ideally 2.5 or higher, and even more ideally 3.0 or higher. By setting the pH of the colloidal silica involved in this invention to a value above the aforementioned (lower limit), the long-term dispersion stability of the silica particles in the colloidal silica involved in this invention can be easily improved.

[0047] In addition, the pH of the colloidal silicon dioxide involved in this invention is ideally below 11.0, more ideally below 10.7, and even more ideally below 10.5. By setting the pH of the colloidal silica involved in this invention below the above-mentioned value (upper limit), the long-term dispersion stability of the colloidal silica can also be easily improved.

[0048] In this application document, pH refers to the value measured by a benchtop pH water quality analyzer (F-2000PI manufactured by Horiba Manufacturing Co., Ltd.).

[0049] The content of silica particles in the colloidal silica involved in this invention is not particularly limited. Ideally, the content of colloidal silica should be more than 2% by mass and less than 50% by mass, provided that the content of colloidal silica is set to 100% by mass.

[0050] When the content of colloidal silica is set to 100% by mass, the content of silica particles (silicon dioxide particle concentration) in the colloidal silica involved in the present invention is ideally 2% by mass or more, more ideally 3% by mass or more, and even more ideally 5% by mass or more.

[0051] By ensuring that the content of silica particles in the colloidal silica involved in this invention is at or above the aforementioned value (lower limit), the grinding performance when the colloidal silica involved in this invention is used as abrasive grains for grinding can be further improved.

[0052] When the content of colloidal silica is set to 100% by mass, the content of silica particles (concentration of silica particles) in the colloidal silica involved in the present invention is ideally 50% by mass or less, more ideally 40% by mass or less, and even more ideally 35% by mass or less. By reducing the content of silica particles in the colloidal silica involved in this invention to below the above-mentioned value (upper limit value), the long-term dispersion stability of silica particles can be further improved.

[0053] Furthermore, in this application, the content of silica particles (concentration of silica particles) in colloidal silica involved in this invention refers to the value measured by the following determination method. That is, it refers to the value calculated by drying 10.0g of colloidal silicon dioxide on a hot plate at 150℃, then heating it at 800℃ for 1 hour to remove moisture, and setting the amount of the resulting solid component as Wg. The content (mass%) of silica particles in colloidal silica = (W / 10.0) × 100

[0054] In the colloidal silicon dioxide involved in this invention, the content of metal impurities (total content of metal impurities) is ideally less than 1 ppm by mass. By reducing the metal impurity content to below 1 ppm by mass, the colloidal silicon dioxide involved in this invention can be made suitable as abrasive grains for grinding electronic materials such as semiconductor wafers.

[0055] In the colloidal silicon dioxide involved in this invention, the metallic impurities can be selected from one or more of sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, cobalt, etc.

[0056] Furthermore, in this application document, the metal impurity content refers to the value measured using an atomic absorption spectrometer.

[0057] Next, the method for manufacturing colloidal silicon dioxide according to the present invention will be described. The method for manufacturing colloidal silica according to the present invention is characterized by comprising: The reaction procedure involves contacting a mother liquor containing an alkaline catalyst, water, and alcohol with a starting material solution containing alcohol and tetraalkoxysilane to obtain a reaction solution; and The maturation process involves adjusting the reaction solution obtained in the aforementioned reaction process to a water concentration of 0-6% by mass, and then heating and stirring at atmospheric pressure and a temperature of 55-65°C for more than 50 hours.

[0058] In the method for manufacturing colloidal silica according to the present invention, the alkaline catalyst constituting the mother liquor is preferably selected from one or more organic amines and ammonia, especially more preferably selected from one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, 3-ethoxypropylamine (3-EOPOA), ammonia, urea, ethanolamine and tetramethylammonium hydroxide, and ammonia is even more preferably selected. In the method for manufacturing colloidal silica according to the present invention, when the alkaline catalyst constituting the mother liquor is the above-mentioned substance, the catalytic effect is excellent and the volatility is high, making it easy to remove in subsequent processes.

[0059] In the method for manufacturing colloidal silica according to the present invention, the concentration of alkaline catalyst in the mother liquor is ideally 0.2 to 3.0% by mass, more ideally 0.3 to 2.5% by mass, and even more ideally 0.5 to 1.8% by mass. In the method for manufacturing colloidal silica according to the present invention, by keeping the concentration of alkaline catalyst in the mother liquor within the above-mentioned range, the particle size of silica particles in the obtained colloidal silica can be easily controlled within the desired range.

[0060] In the method for manufacturing colloidal silica according to the present invention, the water used as the mother liquor is ideally pure water or ultrapure water in order to minimize the mixing of metal impurities.

[0061] In the method for manufacturing colloidal silica according to the present invention, the concentration of water constituting the mother liquor is ideally 3.0 to 25.0% by mass, more ideally 5.0 to 20.0% by mass, and even more ideally 5.0 to 18.0% by mass. In the method for manufacturing colloidal silica according to the present invention, by adjusting the concentration of water in the mother liquor to the above-mentioned range and controlling the mixing ratio of the mother liquor and the raw material solution, the hydrolysis and dehydration condensation reaction of tetraalkoxysilane described later can be easily and appropriately promoted.

[0062] In the method for manufacturing colloidal silica according to the present invention, the alcohol constituting the mother liquor is preferably selected from one or more of methanol, ethanol, isopropanol, etc.

[0063] In the method for manufacturing colloidal silica according to the present invention, the alcohol constituting the mother liquor is preferably the same alcohol as that produced by the hydrolysis of the tetraalkoxysilane described later. For example, if the tetraalkoxysilane described later is tetramethoxysilane (TMOS), the alcohol constituting the mother liquor is preferably methanol. In the method for manufacturing colloidal silica according to the present invention, the alcohol constituting the mother liquor can be easily recovered and reused by using the same alcohol as the alcohol produced by the hydrolysis of tetraalkoxysilane described later.

[0064] In the method for manufacturing colloidal silica involved in this invention, the concentration of alcohol constituting the mother liquor is ideally 70-90% by mass, more ideally 72-88% by mass, and even more ideally 74-86% by mass. In the method for manufacturing colloidal silica according to the present invention, by keeping the concentration of alcohol in the mother liquor within the above-mentioned range, the tetraalkoxysilane described later exhibits excellent dispersibility and readily and appropriately promotes the hydrolysis reaction.

[0065] In the method for manufacturing colloidal silica according to the present invention, the alcohol constituting the raw material solution is preferably selected from one or more of methanol, ethanol, isopropanol, etc.

[0066] In the method for manufacturing colloidal silica according to the present invention, the alcohol constituting the raw material solution is preferably the same alcohol as that produced by the hydrolysis of the tetraalkoxysilane described later. For example, if the tetraalkoxysilane described later is tetramethoxysilane (TMOS), methanol is preferably the alcohol constituting the raw material solution. In the method for manufacturing colloidal silica according to the present invention, the alcohol constituting the raw material solution can be easily recovered and reused by using the same alcohol as the alcohol produced by the hydrolysis of tetraalkoxysilane described later.

[0067] In the method for manufacturing colloidal silica according to the present invention, the tetraalkoxysilane constituting the raw material solution can be listed as the tetraalkoxysilane or its derivative shown in the following general formula (1). Si(OR)4 (1) In the above general formula (1), the R group is an alkyl group having 1 or more but less than 8 carbon atoms.

[0068] In the tetraalkoxysilane or its derivatives represented by general formula (1), the R group is an alkyl group having 1 or more and 8 or fewer carbon atoms, ideally an alkyl group having 1 or more and 4 or fewer carbon atoms.

[0069] In the tetraalkoxysilane or its derivatives represented by general formula (1), the R group can be, for example, selected from one or more of methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, heptyl and octyl, and ideally selected from one or more of methyl, ethyl, propyl, isopropyl and butyl.

[0070] As a tetraalkoxysilane represented by general formula (1), it is ideally a tetramethoxysilane with R group methyl, a tetraethoxysilane with R group ethyl, or a tetraisopropoxysilane with R group isopropyl. In addition, as a derivative of the tetraalkoxysilane shown in general formula (1), a low condensate obtained by partially hydrolyzing the tetraalkoxysilane shown in general formula (1) can be listed. As a tetraalkoxysilane or its derivative represented by general formula (1), the ideal choice is tetramethoxysilane (TMOS) from the aspects of easy control of hydrolysis rate, easy acquisition of small silica particles, and low residue of unreacted substances.

[0071] In the method for manufacturing colloidal silica according to the present invention, the concentration of tetraalkoxysilane in the raw material solution is ideally 4.0~6.5 mol / L, more ideally 4.0~6.0 mol / L, and even more ideally 4.3~6.0 mol / L.

[0072] In the method for manufacturing colloidal silica according to the present invention, by keeping the concentration of tetraalkoxysilane in the raw material solution within the above-mentioned range, the hydrolysis and dehydration condensation reaction of tetraalkoxysilane is easily promoted.

[0073] In the method for manufacturing colloidal silica according to the present invention, a reaction procedure is carried out in which a mother liquor containing the above-mentioned alkaline catalyst, water and alcohol is reacted with a raw material solution containing alcohol and tetraalkoxysilane to obtain a reaction solution.

[0074] In the method for manufacturing colloidal silica according to the present invention, during the reaction process, the mother liquor containing the above-mentioned alkaline catalyst, water and alcohol is ideally contacted with the raw material solution containing alcohol and tetraalkoxysilane in such a manner that the raw material solution is 5 to 45 parts by mass relative to 100 parts by mass of the mother liquor, more ideally in a manner that is 8 to 35 parts by mass, and even more ideally in a manner that is 10 to 30 parts by mass.

[0075] In the method for manufacturing colloidal silica according to the present invention, by controlling the contact amount of the above-mentioned raw material solution with 100 parts by mass of the above-mentioned mother liquor within the above-mentioned range, the hydrolysis and dehydration condensation reaction of tetraalkoxysilane in the raw material solution can be carried out easily and effectively.

[0076] In the method for manufacturing colloidal silica according to the present invention, in the reaction process, the mother liquor containing the above-mentioned alkaline catalyst, water and alcohol and the raw material solution containing alcohol and tetraalkoxysilane are ideally reacted such that the ratio of the content of water in the mother liquor in the reaction solution to the content of tetraalkoxysilane in the raw material solution (content of water in the mother liquor in the reaction solution / content of tetraalkoxysilane in the raw material solution in the reaction solution) is 5.0 to 20.0 in moles, more ideally it is 5.0 to 15.0, and even more ideally it is 5.5 to 13.0.

[0077] In the method for manufacturing colloidal silica according to the present invention, in the reaction process, by carrying out the reaction in such a way that the content of water constituting the mother liquor in the reaction solution / the content of tetraalkoxysilane constituting the raw material solution in the reaction solution is within the above-mentioned range, the hydrolysis and dehydration condensation reaction of tetraalkoxysilane in the raw material solution can be easily carried out, and the particle size of silica particles in the obtained colloidal silica can be easily controlled within the desired range.

[0078] In the method for manufacturing colloidal silica according to the present invention, during the reaction process, when the above-mentioned raw material solution is added to the mother liquor, the addition rate of the raw material solution relative to the mother liquor is ideally 0.0010 to 0.0080 parts by mass / minute, more ideally 0.0015 to 0.0070 parts by mass / minute, and even more ideally 0.0018 to 0.0060 parts by mass / minute. By keeping the addition rate of the above-mentioned raw material solution mother liquor relative to the above-mentioned mother liquor within the above-mentioned range, the hydrolysis and dehydration condensation reaction of tetraalkoxysilane can be easily carried out, and the particle size of the silica particles in the obtained colloidal silica can be easily controlled within the desired range.

[0079] In the method for manufacturing colloidal silicon dioxide involved in this invention, the reaction process can be carried out under any pressure conditions, including reduced pressure, normal pressure, and increased pressure, with the ideal conditions being under normal pressure.

[0080] In the method for manufacturing colloidal silica according to the present invention, when adding the above-mentioned raw material solution to the mother liquor during the reaction process, it is ideal to complete the addition of the raw material solution within 10 minutes to 300 minutes, and more ideally within 30 minutes to 200 minutes.

[0081] In the method for manufacturing colloidal silica according to the present invention, the ideal temperature (reaction temperature) during the reaction process when the mother liquor reacts with the raw material solution to obtain the reaction solution is 10.0~85.0℃, more ideally 12.0~65.0℃, and even more ideally 15.0~40.0℃. In the method for manufacturing colloidal silica according to the present invention, by keeping the reaction time and reaction temperature in the reaction process within the above-mentioned range, the reaction of alkoxysilane is suppressed, and silica particles with the desired particle size are easily generated in the liquid phase.

[0082] In the method for manufacturing colloidal silica according to the present invention, in the reaction process, by contacting and mixing the mother liquor with the raw material solution, the hydrolysis and dehydration condensation reaction of tetraalkoxysilane is initiated in the resulting mixture to synthesize silica particles.

[0083] In the method for manufacturing colloidal silica according to the present invention, a aging process is performed. In this aging process, the reaction solution obtained in the reaction process is adjusted so that the water concentration of the reaction solution is 0 to 6% by mass. On this basis, the solution is heated and stirred for more than 50 hours under normal pressure and at a temperature of 55 to 65°C.

[0084] In the method for manufacturing colloidal silica involved in this invention, during the aging process, the water concentration of the reaction solution obtained in the reaction process is controlled to be 0-6% by mass, ideally 0-5% by mass, and even more ideally 0-4% by mass.

[0085] In the method for manufacturing colloidal silica according to the present invention, during the aging process, by controlling the water concentration of the reaction solution within the aforementioned range, that is, by adjusting it to a concentration lower than that in the reaction solution during the hydrolysis and dehydration condensation reaction of previously known tetraalkoxysilanes, and heating it at a predetermined temperature for a predetermined time (as described later), it is possible to control the value of composite parameter 1 within the desired range without significantly increasing the true specific gravity. The detailed mechanism is still uncertain, but it is believed that due to the low water concentration in the reaction solution, the hydrolysis of silica and the dehydration condensation of the hydrolysates occur only near the surface of the silica particles, potentially forming dense siloxane bonds. It is thought that this, in turn, inhibits the solubility of silica particles under alkaline conditions and controls the density of silanol groups on the particle surface. Furthermore, it is speculated that because the dense siloxane bonds are formed only on the particle surface, the true specific gravity will not be significantly increased.

[0086] In the method for manufacturing colloidal silica according to the present invention, the water concentration in the reaction solution during the aging process can be adjusted to the above range by adding alcohol while heating and distilling off the solvent of the reaction solution obtained in the reaction process, or by controlling the composition of the mother liquor or the raw material solution or controlling the mixing ratio of the mother liquor and the raw material solution during the reaction process.

[0087] In the method for manufacturing colloidal silicon dioxide according to the present invention, the heating and stirring in the curing process are carried out under normal pressure.

[0088] In the method for manufacturing colloidal silica according to the present invention, during the aging process, under the condition that the water concentration is controlled, the reaction solution (obtained by mixing the mother liquor and the raw material solution) is heated and stirred at a temperature of 55~65°C, ideally at a temperature of 57~65°C, and more ideally at a temperature of 60~65°C. In the method for manufacturing colloidal silica according to the present invention, by heating and stirring in the aging process at the temperature range described above under normal pressure, the true specific gravity of silica particles based on the liquid phase displacement method in the obtained colloidal silica can be controlled within the desired range.

[0089] In the method for manufacturing colloidal silica according to the present invention, in the aging process, based on the control of water concentration, the reaction solution (obtained by mixing the mother liquor and the raw material solution) is heated and stirred for more than 50 hours under the above-mentioned temperature conditions, ideally for more than 55 hours, and more ideally for more than 60 hours.

[0090] In the method for manufacturing colloidal silica according to the present invention, during the aging process, while controlling the water concentration of the mixture (obtained by mixing the mother liquor and the raw material solution) to a low concentration, a long-term heating and stirring treatment is performed as described above under the above-mentioned temperature conditions. This allows the solubility of silica particles under alkaline conditions and the density of silanol groups on the particle surface to be controlled to the desired degree.

[0091] Therefore, in the method for manufacturing colloidal silica according to the present invention, by implementing the above-mentioned aging process, the solubility of silica particles under alkaline conditions can be controlled without significantly increasing the true specific gravity. Therefore, in the obtained colloidal silica, the silica concentration "A" in the solvent after setting the silica particle concentration to 10% by mass and adjusting the pH to 10.5 for 24 hours can be reduced. Furthermore, in the method for manufacturing colloidal silica according to the present invention, by implementing the above-mentioned curing process, the density of silanol groups on the particle surface can be controlled, and the density of silanol groups "B" of silica particles measured by the Sears method can be reduced in the obtained colloidal silica. Therefore, in the method for manufacturing colloidal silica according to the present invention, the obtained colloidal silica can control the composite parameter 1 calculated by the following formula (1) within the desired range. Wherein, A: the silica concentration (ppm) in the solvent after the silica particle concentration is set to 10% by mass, the pH is adjusted to 10.5 and left for 24 hours; B: the silanol group density of the aforementioned silica particles (units / nm2) determined by the Sears method; and C: the average secondary particle size (nm) of the aforementioned silica particles determined by dynamic light scattering method.

[0092] In the method for manufacturing colloidal silica involved in this invention, the aging solution obtained through the aging process contains organic solvents such as alcohols in addition to water. Therefore, in order to improve long-term storage stability, the dispersion medium of the obtained reaction solution can be replaced with water or concentrated as needed.

[0093] There are no particular limitations on the method of replacing the above-mentioned organic solvent with water. For example, the following method can be listed: while using an ultrafiltration membrane to concentrate the aged liquid obtained by the aging process, water is continuously added to replace the organic solvent with water.

[0094] In the method for manufacturing colloidal silicon dioxide involved in this invention, there are no particular limitations on the method for concentrating the aging solution obtained through the aging process, such as heating concentration method, membrane concentration method, etc.

[0095] Thus, in the method for manufacturing colloidal silica according to the present invention, colloidal silica with the desired properties can be obtained.

[0096] In the method for manufacturing colloidal silica involved in this invention, from the viewpoint of not increasing the true specific gravity of silica particles based on the liquid phase displacement method, it is ideal to not include pressurization treatment at temperatures exceeding 100°C, i.e., pressurization heating treatment under high pressure exceeding atmospheric pressure.

[0097] From the viewpoint of not increasing the true specific gravity of silica particles based on the liquid-phase displacement method, the method for manufacturing colloidal silica involved in this invention is ideally a calcination process that does not include silica particles.

[0098] According to the present invention, a simple method for manufacturing colloidal silica can be provided, wherein when the aforementioned colloidal silica is used as abrasive grains for grinding, silica particles are less likely to remain on the grinding surface, and a grinding surface with reduced surface roughness can be formed. [Example]

[0099] Next, embodiments and comparative examples will be listed to further illustrate the present invention in detail, but the present invention is not limited to any of the following examples.

[0100] (Example 1) (1) Mix 785 parts by weight of pure water, 193 parts by weight of 28% ammonia water and 5486 parts by weight of methanol to prepare mother liquor. Next, while maintaining the liquid temperature in the reaction system at 20.5°C, a raw material solution containing 1210 parts by mass of tetramethoxysilane (TMOS) and 326 parts by mass of methanol was injected into the above mother liquor at a constant rate over 46 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) The obtained silica sol reaction solution was heated and distilled under normal pressure while methanol was added. The addition of methanol was stopped when the water concentration in the liquid reached 5.1% by mass. Next, the temperature of the reaction solution, to which the water concentration had been adjusted, was maintained at 60°C while being heated and stirred for 50 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing the target colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0101] (Example 2) (1) Mix 1079 parts by weight of pure water, 185 parts by weight of 28% ammonia water and 5219 parts by weight of methanol to prepare mother liquor. Next, while maintaining the liquid temperature in the reaction system at 19.8°C, a raw material solution containing 1195 parts by mass of tetramethoxysilane (TMOS) and 322 parts by mass of methanol was injected into the above mother liquor at a constant rate over 90 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) While heating and distilling the obtained reaction solution under normal pressure, methanol was added. The addition of methanol was stopped when the water concentration of the solution reached 5.2% by mass. Next, the temperature of the reaction solution, to which the water concentration had been adjusted, was maintained at 63°C while being heated and stirred for 50 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0102] (Example 3) (1) Mix 825 parts by weight of pure water, 254 parts by weight of 28% ammonia water, and 5383 parts by weight of methanol to prepare the mother liquor. Next, while maintaining the liquid temperature in the reaction system at 19.4°C, a raw material solution containing 1211 parts by mass of tetramethoxysilane (TMOS) and 327 parts by mass of methanol was injected into the above mother liquor at a constant rate over 55 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) While heating and distilling the obtained silica sol reaction solution under normal pressure, methanol was added. The addition of methanol was stopped when the water concentration of the solution reached 4.9% by mass. Next, the temperature of the reaction solution, to which the water concentration had been adjusted, was maintained at 58°C while being heated and stirred for 55 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing the target colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0103] (Example 4) (1) Mix 879 parts by weight of pure water, 142 parts by weight of 28% ammonia water and 5411 parts by weight of methanol to prepare mother liquor. Next, while maintaining the liquid temperature in the reaction system at 22.1°C, a raw material solution containing 1235 parts by mass of tetramethoxysilane (TMOS) and 333 parts by mass of methanol was injected into the above mother liquor at a constant rate over 43 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) While heating and distilling the obtained reaction solution under normal pressure, methanol was added. The addition of methanol was stopped when the water concentration of the solution reached 5.8% by mass. Next, the temperature of the reaction solution, to which the water concentration had been adjusted, was maintained at 65°C while being heated and stirred for 70 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0104] (Example 5) (1) Mix 258 parts by weight of pure water, 448 parts by weight of 28% ammonia water and 6348 parts by weight of methanol to prepare mother liquor. Next, while maintaining the liquid temperature in the reaction system at 8.2°C, a raw material solution containing 745 parts by mass of tetramethoxysilane (TMOS) and 201 parts by mass of methanol was injected into the above mother liquor at a constant rate over 48 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) The obtained silica sol reaction solution was heated and distilled under normal pressure while methanol was added. The addition of methanol was stopped when the water concentration of the solution reached 4.7% by mass. Next, the temperature of the reaction solution, to which the water concentration had been adjusted, was maintained at 55°C while being heated and stirred for 50 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing the target colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0105] (Example 6) (1) Mix 1222 parts by weight of pure water, 261 parts by weight of 28% ammonia water, and 5167 parts by weight of methanol to prepare the mother liquor. Next, while maintaining the liquid temperature in the reaction system at 21.1°C, a raw material solution containing 1063 parts by mass of tetramethoxysilane (TMOS) and 287 parts by mass of methanol was injected into the above mother liquor at a constant rate over 90 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) While heating and distilling the obtained silica sol reaction solution under normal pressure, methanol was added. The addition of methanol was stopped when the water concentration of the solution reached 5.2% by mass. Next, the temperature of the reaction solution, to which the water concentration had been adjusted, was maintained at 63°C while being heated and stirred for 50 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing the target colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0106] (Example 7) (1) Mix 1151 parts by weight of pure water, 311 parts by weight of 28% ammonia water, and 5026 parts by weight of methanol to prepare mother liquor. Next, while maintaining the liquid temperature in the reaction system at 20.7°C, a raw material solution containing 1191 parts by mass of tetramethoxysilane (TMOS) and 321 parts by mass of methanol was injected into the above mother liquor at a constant rate over 90 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) While heating and distilling the obtained reaction solution under normal pressure, methanol was added. The addition of methanol was stopped when the water concentration of the solution reached 4.8% by mass. Next, the temperature of the reaction solution, to which the water concentration had been adjusted, was maintained at 60°C while being heated and stirred for 50 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing the target colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0107] (Example 8) (1) Mix 804 parts by weight of pure water, 179 parts by weight of 28% ammonia water and 6086 parts by weight of methanol to prepare mother liquor. Next, while maintaining the liquid temperature in the reaction system at 20.5°C, a raw material solution containing 733 parts by mass of tetramethoxysilane (TMOS) and 198 parts by mass of methanol was injected into the above mother liquor at a constant rate over 33 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) The obtained silica sol reaction solution was heated and distilled under normal pressure while methanol was added. The addition of methanol was stopped when the water concentration in the liquid reached 5.4% by mass. Next, the temperature of the reaction solution, to which the water concentration had been adjusted, was maintained at 65°C while being heated and stirred for 50 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing the target colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0108] (Example 9) (1) Mix 1310 parts by weight of pure water, 150 parts by weight of 28% ammonia water and 4899 parts by weight of methanol to prepare mother liquor. Next, while maintaining the liquid temperature in the reaction system at 19.9°C, a raw material solution containing 1292 parts by mass of tetramethoxysilane (TMOS) and 348 parts by mass of methanol was injected into the above mother liquor at a constant rate over 40 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) While heating and distilling the obtained silica sol reaction solution under normal pressure, methanol was added. The addition of methanol was stopped when the water concentration of the solution reached 5.1% by mass. Next, the reaction solution was heated and stirred at 60°C for 65 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing the target colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0109] (Example 10) (1) Mix 713 parts by weight of pure water, 213 parts by weight of 28% ammonia water, and 5535 parts by weight of methanol to prepare a mother liquor. Next, while maintaining the liquid temperature in the reaction system at 21.3°C, a raw material solution containing 1212 parts by mass of tetramethoxysilane (TMOS) and 327 parts by mass of methanol was injected into the above mother liquor at a constant rate over 49 minutes to prepare a silica sol reaction solution with water and methanol as the dispersion medium. (2) While heating and distilling the obtained silica sol reaction solution under normal pressure, methanol was added. The addition of methanol was stopped when the water concentration of the solution reached 4.9% by mass. Next, the temperature of the reaction solution, to which the water concentration had been adjusted, was maintained at 58°C while being heated and stirred for 65 hours. The stirred solution is passed through a filter module equipped with an ultrafiltration membrane to remove methanol and ammonia while pure water is continuously added, thereby replacing the solvent with water. When the pH reaches below 8, the addition of pure water is stopped, and solvent removal based on membrane concentration continues. Membrane concentration is stopped when the concentration of silica particles in the solution reaches 20% by mass, thus preparing the target colloidal silica. The manufacturing conditions in this embodiment are described in Table 1. In addition, the physical properties of the colloidal silicon dioxide obtained in this embodiment are described in Table 2.

[0110] (Comparative Example 1) A silica sol reaction solution was obtained under the same conditions as in Example 4(1). The obtained silica sol reaction solution was concentrated under normal pressure by heating and distillation. To maintain a constant volume, pure water was added while the concentrate was heated and distilled under normal pressure. Methanol and ammonia in the concentrate were replaced with water. The addition of pure water and heating were stopped when the pH reached below 8, thus preparing colloidal silica with a silica particle concentration of 20% by mass. The physical properties of the colloidal silicon dioxide obtained in this comparative example are shown in Table 3.

[0111] (Comparative Example 2) A silica sol reaction solution was obtained under the same conditions as in Example 8(1). The obtained silica sol reaction solution was concentrated under normal pressure by heating and distillation. To maintain a constant volume, pure water was added while the concentrate was heated and distilled under normal pressure. Methanol and ammonia in the concentrate were replaced with water. The addition of pure water and heating were stopped when the pH reached below 8, thus preparing colloidal silica with a silica particle concentration of 20% by mass. The physical properties of the colloidal silicon dioxide obtained in this comparative example are shown in Table 3.

[0112] (Comparative Example 3) The colloidal silica obtained in Comparative Example 2 was placed in a pressure-resistant container, and a pressure heating treatment was performed for 5 hours while maintaining the internal pressure at 0.4 MPa and the solution temperature at 140°C, thereby producing colloidal silica with a silica particle concentration of 20% by mass. The physical properties of the colloidal silicon dioxide obtained in this comparative example are shown in Table 3.

[0113] (Comparative Example 4) The colloidal silicon dioxide obtained in Comparative Example 2 was calcined in air at 950–1050 °C. The calcined material was then fed into a ball mill and crushed using balls with a diameter of 3 mm. Crushed calcined material (silicon dioxide particles) and pure water were mixed to a silicon dioxide particle concentration of 20% by mass, thereby dispersing the silicon dioxide particles in the water and preparing calcined colloidal silicon dioxide. The physical properties of the colloidal silicon dioxide obtained in this comparative example are shown in Table 3.

[0114] Using the colloidal silicon dioxide obtained in the above embodiments and comparative examples as abrasive grains, the number of residual particles on the grinding surface and the surface roughness were evaluated by the following method. The results are shown in Tables 2 and 3.

[0115] <Number of residual particles on the grinding surface> A grinding composition was prepared by adding ultrapure water and 28% by mass ammonia to colloidal silica to a silica concentration of 3.0% by mass and a pH of 10.5. Using the obtained polishing composition, a 3 cm square silicon wafer with a silicon oxide film on its surface was polished under the following conditions. (Grinding conditions) Grinding machine: NF-300CMP manufactured by Nanofactor Corporation Grinding pad: Manufactured by NITTA DuPont Inc., IC1000TMPad Slurry supply rate: 50 mL / min Head speed: 32 rpm Grinding table speed: 32 rpm Grinding pressure: 4 psi Grinding time: 2 minutes (Cleaning conditions) The polished silicon wafer is cleaned by brushing with a PVA roller brush under the following conditions using the scrubbing section built into the cleaning and drying unit MAT ZAB-8S1M. To secure the silicon wafers, a clamp was used with a frame made of glass epoxy resin and a wafer-fixing part made of polyurethane. Brush: Manufactured by AION, AION SCL BRUSH ROLLER 48(40 / 26)×224mm Scrubbing time: 1 minute Brush speed: 200 rpm Rotation speed of silicon wafer holder: 50 rpm After rinsing, ultrapure water is flowed over the upper side of the polishing substrate at a flow rate of 750 mL / min for 1 minute. Then, the substrate is further treated with a rotary dryer built into the above device at 1800 rpm for 20 seconds. (Conditions for measuring particle number) The number of residual particles on the polished surface of the dried silicon wafer was measured using an atomic force microscope. Atomic Force Microscope: SPM-9700HT manufactured by Shimadzu Corporation Cantilever: OLYMPUS, MICRO CANTILEVER OMCL-AC240TS-R3 Observation Mode: Dynamic Scan range: 3.0 μm square Scan speed: 1.00Hz Number of observation fields: Five random fields of view are observed for each polished wafer (each field of view has an observation range of 3μm×3μm). The number of particles remaining on the polished surface is counted in five fields of view (five fields of view) on the polished surface. The total count in the five fields of view is divided by the area of ​​the five fields of view (45 μm2) to obtain the number of particles remaining on the polished surface (particles / μm2). When measuring the number of residual particles (particles / μm2) on the grinding surface using the above method, if the number of residual particles on the grinding surface is less than 2 (particles / μm2), it is judged that the amount of silicon dioxide particles remaining on the grinding surface is small; if the number of residual particles on the grinding surface exceeds 2 (particles / μm2), it is judged that the amount of silicon dioxide particles remaining on the grinding surface is large.

[0116] <Evaluation Methods for Grinding Surface Roughness> A grinding composition was prepared by adding ultrapure water and 28% by mass ammonia to colloidal silica, and diluting the silica particles to a concentration of 3.0% by mass and a pH of 10.5. Using the obtained polishing composition, a 3 cm square silicon wafer with a silicon oxide film on its surface was polished under the following conditions. (Grinding conditions) Grinding machine: NF-300CMP manufactured by Nanofactor Corporation Grinding pad: Manufactured by NITTA DuPont Inc., IC1000TMPad The grinding slurry supply rate is 50 mL / min. Head speed: 32 rpm Grinding table speed: 32 rpm Grinding pressure: 4 psi Grinding time: 2 min (Cleaning conditions) The polished silicon wafer is cleaned by brushing with a PVA roller brush under the following conditions using the scrubbing section built into the cleaning and drying unit MAT ZAB-8S1M. At this point, in order to fix the silicon wafer, a clamp was used with the frame made of glass epoxy resin and the wafer fixing part made of polyurethane. Brush: Manufactured by AION, AION SCL BRUSH ROLLER 48(40 / 26)×224mm Scrubbing time: 1 minute Brush speed: 200 rpm Rotation speed of silicon wafer holder: 50 rpm After rinsing, ultrapure water is flowed over the upper side of the polishing substrate at a flow rate of 750 mL / min for 1 minute. Then, the substrate is further treated with a rotary dryer built into the above device at 1800 rpm for 20 seconds. (Conditions for measuring surface roughness) After the above cleaning process, the surface roughness of the polished surface is measured using an atomic force microscope under the following conditions on a fully dried wafer. Atomic Force Microscope: SPM-9700HT manufactured by Shimadzu Corporation Cantilever: OLYMPUS, MICRO CANTILEVER OMCL-AC240TS-R3 Observation Mode: Dynamic Scan range: 3.0 μm square Scan speed: 1.00Hz Number of observation fields: Five random fields of view are observed for each polished wafer (each field of view has an observation range of 3μm×3μm). The root mean square roughness xi (nm) was measured in five fields of view (five fields of view) on the wafer grinding surface. The arithmetic mean of the root mean square roughness xi (nm) in the five fields of view was taken as the roughness Rms (nm) of the grinding surface. If the surface roughness Rms is below 3.000 nm, the surface roughness is considered good; if the surface roughness Rms is above 3.000 nm, the surface roughness is considered poor.

[0117]

[0118]

[0119]

[0120] As shown in Table 2, for the colloidal silicon dioxide obtained by the specific manufacturing method in Examples 1 to 10, the true specific gravity of the silicon dioxide particles based on the liquid phase displacement method is 1.60 or more and 2.20 or less, and the value of the composite parameter 1 calculated by the specific formula is 10 or more and 200 or less. Therefore, when used as abrasive grains for polishing silicon wafers, the number of residual particles on the polishing surface is 2 or less (particles / μm2), the residual amount of silicon dioxide particles is small, or the surface roughness Rms is 3.000 nm or less, which can suppress surface roughness.

[0121] On the other hand, as shown in Table 3, for the colloidal silicon dioxide obtained by conventional manufacturing methods in Comparative Example 1 and Comparative Example 2, the value of composite parameter 1 calculated by the specific formula is outside the predetermined range. Therefore, when used as abrasive grains for grinding silicon wafers, the number of residual particles on the grinding surface exceeds 2 (particles / μm2), and the amount of residual silicon dioxide particles is high. Furthermore, as shown in Table 3, for the colloidal silicon dioxide obtained by conventional manufacturing methods in Comparative Examples 3 and 4, the true specific gravity of the silicon dioxide particles based on the liquid phase displacement method is outside the predetermined range. Therefore, when used as abrasive grains for polishing silicon wafers, the surface roughness with a polishing surface roughness Rms greater than 3.000 nm increases. [Industrial applicability]

[0122] According to the present invention, a colloidal silica that, when used as an abrasive for grinding, does not easily leave silica particles on the grinding surface and can form a grinding surface with reduced surface roughness, and a method for manufacturing colloidal silica, are provided.

Claims

1. A colloidal silica, which is a colloidal silica formed by dispersing silica particles in a solvent, characterized in that the true specific gravity of the silica particles based on the liquid-phase displacement method is 1.60 or more and 2.20 or less, and the value of the composite parameter 1 calculated by the following formula (1) is 10 or more and 200 or less, wherein, A: Silicon concentration (ppm) in the solvent after the silica particle concentration is set to 10% by mass, the pH is adjusted to 10.5, and 24 hours have passed. B: Silanol group density of the silica particles (units / nm2) determined by the Sears method. C: Average secondary particle size (nm) of the silica particles determined by dynamic light scattering.

2. The colloidal silicon dioxide as described in claim 1, wherein, The average secondary particle size of silicon dioxide particles determined by this dynamic light scattering method is 3~200 nm.

3. The colloidal silicon dioxide as described in claim 1, wherein, The content of metallic impurities is less than 1 ppm by mass.

4. A method for manufacturing colloidal silica, which is a method for manufacturing colloidal silica as described in any one of claims 1 to 3, characterized in that the method for manufacturing colloidal silica comprises: a reaction process in which a mother liquor containing an alkaline catalyst, water, and an alcohol is contacted with a raw material solution containing an alcohol and a tetraalkoxysilane to obtain a reaction solution; and a aging process in which the reaction solution obtained in the reaction process is adjusted to a water concentration of 0 to 6% by mass, and then heated and stirred at a temperature of 55 to 65°C for at least 50 hours under normal pressure.

5. The method for manufacturing colloidal silicon dioxide as described in claim 4, wherein, The alkaline catalyst is ammonia, the alcohol in the mother liquor is methanol, the alcohol in the raw material solution is methanol, and the tetraalkoxysilane is tetramethoxysilane.