Colloidal silicon dioxide and a method for its production

Abstract

The present invention relates to colloidal silicon dioxide containing silicon dioxide particles with a small average secondary particle size and dispersion stability that can be maintained for extended periods even under strongly acidic conditions at a pH of 3 or less, and to a method for its preparation. The present invention relates to colloidal silicon dioxide comprising silicon dioxide particles, wherein the silicon dioxide particles have an average secondary particle size of 20 nm or less, as measured by dynamic light scattering, and a zeta potential of -20 mV or less, as measured at a pH of 3, and are surface-modified with a sulfonic acid group.

Description

Technical field

[0001] The present invention relates to colloidal silicon dioxide and a method for its production. Technical background

[0002] Colloidal silicon dioxide is a dispersion of silicon dioxide particles in a medium such as water. It is used to improve the physical properties of paper, textiles, steel, and similar materials, and also serves as an abrasive for polishing electronic materials such as semiconductor wafers (CMP).

[0003] With the reduction of semiconductor conduction width, electronic materials undergoing CMP must exhibit higher surface smoothness and lower defect rates. To meet these requirements, silicon dioxide particles with a small average secondary particle size and good dispersion stability are needed. In general, silicon dioxide particles with a smaller particle size are more prone to aggregation and become less stable under acidic conditions as their zeta potential approaches the isoelectric point.

[0004] Colloidal silicon dioxide with small silicon dioxide particles having an average particle size of 20 nm or less has been proposed (see PTL 1). However, the silicon dioxide colloid disclosed in PTL 1 cannot maintain good dispersion stability under strongly acidic conditions with a pH of 3 or less, and the particles continue to aggregate over time.

[0005] To improve dispersion stability under acidic conditions, a method for modifying the surface of silicon dioxide particles with a sulfonic acid group was proposed (see PTL 2). In the method disclosed in PTL 2, fine colloidal silicon dioxide with an average particle size of 20 nm or less is modified with sulfonic acid to produce sulfonic acid-modified fine colloidal silicon dioxide with an average particle size of 20 nm or less.

[0006] However, the sulfonic acid-modified fine colloidal silicon dioxide particles disclosed in PTL 2 are not sufficiently surface-modified with a sulfonic acid group. Therefore, the absolute value of the zeta potential in the acidic range is low, and the colloidal silicon dioxide cannot maintain long-term dispersion stability under strongly acidic conditions with a pH of approximately 3.

[0007] Therefore, there is a need for the development of colloidal silicon dioxide with a small average secondary particle size that can maintain dispersion stability over long periods even under strongly acidic conditions with a pH of 3, as well as for a method to produce it. List of citations from patent literature PTL 1: JP2004-315300A PTL 2: WO2023-007938 Brief description of the invention: Technical problem

[0008] The present invention was developed taking into account the aforementioned circumstances and aims to provide colloidal silicon dioxide containing silicon dioxide particles with a small average secondary particle size and a dispersion stability that can be maintained even under strongly acidic conditions with a pH of 3 for long periods of time, as well as a method for its production. Solution to the problem

[0009] As a result of extensive investigations to solve the aforementioned problem, the inventors found that the aforementioned problem can be solved with colloidal silicon dioxide containing silicon dioxide particles in which the silicon dioxide particles have an average secondary particle size of 20 nm or less, measured by dynamic light scattering, and a zeta potential of -20 mV or less, measured at a pH of 3, and are surface-modified with a sulfonic acid group. The present invention was thus completed.

[0010] In particular, the present invention relates to the following colloidal silicon dioxide and a method for its production. Item 1. Colloidal silicon dioxide, comprising silicon dioxide particles, wherein the silicon dioxide particles have an average secondary particle size of 20 nm or less, as measured by dynamic light scattering, and a zeta potential of -20 mV or less, as measured at a pH of 3, and are surface-modified with a sulfonic acid group. Point 2. The colloidal silicon dioxide according to point 1, wherein the silicon dioxide particles have a sulfonic acid group content of 0.02 atm% or more. Point 3. The colloidal silicon dioxide according to point 1 or 2, where the silicon dioxide particles have an average primary particle size of 18 nm or less, calculated from a BET-specific surface area. Item 4. The process for producing colloidal silicon dioxide, wherein the process comprises a step in which a silane adhesion promoter with a mercapto group and an oxidizing agent are added to colloidal silicon dioxide, wherein the temperature of the colloidal silicon dioxide in this step is 65°C or higher. Point 5. The manufacturing process according to point 4, wherein the silane adhesion promoter with a mercapto group is at least one selected from the group consisting of 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane and 2-mercaptoethyltriethoxysilane. Point 6. The manufacturing process according to point 4 or 5, wherein the oxidizing agent is at least one selected from the group consisting of nitric acid, hydrogen peroxide, oxygen, ozone, organic peracid, bromine, hypochlorite, potassium permanganate and chromic acid. Advantageous effects of the invention

[0011] The present invention was developed taking into account the aforementioned circumstances and aims to provide colloidal silicon dioxide containing silicon dioxide particles with a small average secondary particle size and a dispersion stability that can be maintained for long periods of time even under strongly acidic conditions at a pH of 3 or less, and a method for its production. Description of the embodiments

[0012] The colloidal silicon dioxide of the present invention is a colloidal silicon dioxide containing silicon dioxide particles, wherein the silicon dioxide particles have an average secondary particle size of 20 nm or less, as measured by dynamic light scattering, and a zeta potential of -20 mV or less, as measured at pH 3, and are surface-modified with a sulfonic acid group. In the colloidal silicon dioxide of the present invention, the silicon dioxide particles have an average secondary particle size of 20 nm or less, as measured by dynamic light scattering, and a zeta potential of -20 mV or less, as measured at pH 3. Thus, even under acidic conditions at pH 3 or less, the silicon dioxide particles have a small average secondary particle size of 20 nm or less.Therefore, a surface polished with colloidal silicon dioxide as an abrasive exhibits low surface roughness. The surface of the colloidal silicon dioxide of the present invention is modified with a sulfonic acid group. Accordingly, the average secondary particle size of the silicon dioxide particles can be maintained at a small particle size of 20 nm or less, and the zeta potential measured at pH 3 can be maintained at -20 mV or less. The colloidal silicon dioxide with the aforementioned properties exhibits high dispersion stability under acidic conditions at pH 3 or less and can achieve a high degree of surface smoothness when used as an abrasive.

[0013] The manufacturing process of the present invention comprises a step in which a silane adhesion promoter with a mercapto group and an oxidizing agent are added to colloidal silicon dioxide, wherein the temperature of the colloidal silicon dioxide in this step is 65°C or higher. In the manufacturing process of the present invention, a silane adhesion promoter with a mercapto group and an oxidizing agent are added to colloidal silicon dioxide within a specific temperature range of 65°C or higher, thereby preventing silicon dioxide particles from aggregating upon modification with a sulfonic acid group. This prevents the average secondary particle size from increasing above 20 nm, and the modification with a sulfonic acid group improves the dispersion stability of the silicon dioxide particles, making it possible to maintain the state in which aggregation is suppressed over long periods.

[0014] The colloidal silicon dioxide of the present invention and a method for its production are described in detail below. 1. Colloidal silicon dioxide

[0015] The colloidal silicon dioxide of the present invention contains silicon dioxide particles. The silicon dioxide particle content of the colloidal silicon dioxide is preferably 1% or more by mass, more preferably 3% or more by mass, and even more preferably 5% or more by mass, based on 100% by mass of the colloidal silicon dioxide. The silicon dioxide particle content of the colloidal silicon dioxide is preferably 50% or less by mass, more preferably 40% or less by mass, and even more preferably 30% or less by mass, based on 100% by mass of the colloidal silicon dioxide. If the lower limit of the silicon dioxide particle content of the colloidal silicon dioxide lies within the aforementioned ranges, the colloidal silicon dioxide exhibits further improved polishing performance when used as an abrasive.Since the upper limit of the silicon dioxide particle content lies within the aforementioned ranges, the silicon dioxide particles exhibit a further improved dispersion stability.

[0016] In the present description, the silicon dioxide particle content of the colloidal silicon dioxide can be calculated by drying and solidifying 10.0 g of the colloidal silicon dioxide on a hot plate at 150°C, heating the colloidal silicon dioxide for 1 hour at 800°C to remove moisture, and inserting the amount of solids obtained, Wg, into the following formula: Silicon dioxide particle content of the colloidal silicon dioxide [%] = (W / 10,0) × 100.

[0017] The silicon dioxide particles in the colloidal silicon dioxide of the present invention have an average secondary particle size of 20 nm or less, as measured by dynamic light scattering. The average secondary particle size is preferably 18 nm or less, more preferably 16 nm or less, even more preferably 14 nm or less, and particularly preferably 13.5 nm or less. The lower limit of the average secondary particle size is not particularly limited, but is preferably 2 nm or more, more preferably 4 nm or more, even more preferably 6 nm or more, and particularly preferably 8 nm or more. When the lower limit of the average secondary particle size lies within the aforementioned ranges, the colloidal silicon dioxide exhibits further improved polishing performance when used as an abrasive.

[0018] In this description, the average secondary particle size of the silicon dioxide particles in colloidal silicon dioxide is measured by dynamic light scattering. Specifically, it is a measurement method that is described in the examples (described later).

[0019] The average primary particle size of the silicon dioxide particles is preferably 20 nm or less, more preferably 18 nm or less, and even more preferably 10 nm or less. If the upper limit of the average primary particle size lies within the aforementioned ranges, the colloidal silicon dioxide of the present invention can achieve a further improved surface smoothness when used for polishing. The average primary particle size of the silicon dioxide particles is preferably 3 nm or more, more preferably 5 nm or more, and even more preferably 7 nm or more. If the lower limit of the average primary particle size of the silicon dioxide particles lies within the aforementioned ranges, the colloidal silicon dioxide exhibits further improved storage stability.

[0020] In the present description, the average primary particle size of the silicon dioxide particles in the colloidal silicon dioxide is measured by a method described in the examples (described later).

[0021] In this description, the zeta potential of colloidal silicon dioxide is measured by electrophoretic light scattering using an ELS-Z available from Otsuka Electronics Co. Ltd.

[0022] The colloidal silicon dioxide of the present invention has a zeta potential of -20 mV or less, measured at pH 3. If the zeta potential measured at pH 3 exceeds -20 mV, the dispersion stability of the silicon dioxide particles cannot be maintained for extended periods under strongly acidic conditions. The zeta potential measured at pH 3 is preferably -22 mV or less, more preferably -24 mV or less, and even more preferably -26 mV or less. If the lower limit of the zeta potential lies within the aforementioned ranges, higher dispersion stability can be maintained under strongly acidic conditions. The lower limit of the zeta potential measured at pH 3 is not particularly restricted and may be -120 mV or more, -100 mV or more, or the like.

[0023] In the present description, the zeta potential measured at a pH of 3 is measured using a method described in the examples (described later).

[0024] The silicon dioxide particles in the colloidal silicon dioxide of the present invention are surface-modified with a sulfonic acid group. If the silicon dioxide particles are not surface-modified with a sulfonic acid group, the colloidal silicon dioxide cannot maintain the dispersion stability of the silicon dioxide particles under strongly acidic conditions at a pH of 3 for extended periods.

[0025] In the present description, the surface modification of the silicon dioxide particles in the colloidal silicon dioxide with a sulfonic acid group can be recognized by the fact that the sulfonic acid group content (described later) of the silicon dioxide particles is 0.02 atm% or more.

[0026] The sulfonic acid group content of the silicon dioxide particles in the colloidal silicon dioxide of the present invention is preferably 0.02 atm% or more, more preferably 0.05 atm% or more, even more preferably 0.08 atm% or more, particularly preferably 0.10 atm% or more, and most preferably 0.15 atm% or more. If the lower limit of the sulfonic acid group content lies within the aforementioned ranges, the silicon dioxide particles in the colloidal silicon dioxide of the present invention exhibit further improved dispersion stability and dispersibility over long periods. The upper limit of the sulfonic acid group content is not particularly restricted and can, for example, be 2.00 atm% or less, 1.50 atm% or less, or 1.00 atm% or less.

[0027] In the present description, the sulfonic acid group content of the silicon dioxide particles in the colloidal silicon dioxide is measured by a method described in the examples (described below).

[0028] The aggregation ratio of the silicon dioxide particles in the colloidal silicon dioxide is preferably 1.00 or more, more preferably 1.05 or more, and particularly preferably 1.10 or more. At the same time, the aggregation ratio of the silicon dioxide particles is preferably 4.00 or less, more preferably 3.00 or less, even more preferably 2.00 or less, and particularly preferably 1.50 or less. If the lower limit of the aggregation ratio of the silicon dioxide particles lies within the aforementioned ranges, the polishing rate increases further when the colloidal silicon dioxide is used for polishing. If the upper limit of the aggregation ratio of the silicon dioxide particles lies within the aforementioned ranges, the surface smoothness improves further when the colloidal silicon dioxide is used for polishing.

[0029] In the present description, the aggregation ratio of the silicon dioxide particles in the colloidal silicon dioxide is a value determined by dividing the average secondary particle size by the average primary particle size of the silicon dioxide particles in the colloidal silicon dioxide.

[0030] The pH of the colloidal silicon dioxide of the present invention can be adjusted appropriately according to the application of the colloidal silicon dioxide. The pH is not particularly limited, but is preferably 2.0 or higher and more preferably 3.0 or higher. The pH is preferably 11.0 or lower and more preferably 10.0 or lower. If the lower limit of the pH is within the aforementioned ranges, the silicon dioxide particles in the colloidal silicon dioxide exhibit further improved dispersion stability over long periods. If the upper limit of the pH is within the aforementioned ranges, the colloidal silicon dioxide exhibits further improved dispersion stability over long periods.

[0031] The particle density of the silicon dioxide particles in the colloidal silicon dioxide of the present invention is preferably 1.50 or more, more preferably 1.65 or more, and even more preferably 1.80 or more. If the lower limit of the particle density lies within the aforementioned ranges, the colloidal silicon dioxide of the present invention exhibits a further improved polishing performance. The particle density is preferably 2.30 or less, more preferably 2.20 or less, and particularly preferably 2.16 or less. If the upper limit of the true density lies within the aforementioned ranges, the occurrence of scratches on the polished object is further reduced.

[0032] In the present description, the true density can be measured by a liquid immersion method using ethanol, after the colloidal silicon dioxide has been dried and solidified on a hot plate at 150°C and held in an oven at 300°C for 1 hour.

[0033] The colloidal silicon dioxide of the present invention contains metallic impurities such as sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt, preferably in an amount of no more than 1 ppm. If the content of metallic impurities is no more than 1 ppm, the colloidal silicon dioxide can be used appropriately for polishing electronic materials and other similar materials.

[0034] The colloidal silicon dioxide of the present invention can be used as an agent for improving the physical properties of, for example, paper, textiles, steel, and the like, as well as an abrasive for electronic materials such as semiconductor wafers. When dried into a powder, the colloidal silicon dioxide can also be used as an additive for fillers, as an external additive for toner, and the like. 2. Process for the production of colloidal silicon dioxide

[0035] The process for producing colloidal silicon dioxide according to the present invention is a manufacturing process comprising a step in which a silane adhesion promoter with a mercapto group and an oxidizing agent are added to colloidal silicon dioxide, wherein the temperature of the colloidal silicon dioxide in this step is 65°C or higher. In the manufacturing process of the present invention, a silane adhesion promoter with a mercapto group and an oxidizing agent are added to colloidal silicon dioxide within a specific temperature range of 65°C or higher, thereby suppressing the aggregation of silicon dioxide particles when the silicon dioxide particles are modified with a sulfonic acid group.This prevents the average secondary particle size from increasing above 20 nm, and the modification with a sulfonic acid group improves the dispersion stability of the silicon dioxide particles, making it possible to maintain the state in which aggregation is suppressed over long periods of time.

[0036] In the preceding step, the temperature of the colloidal silicon dioxide is 65°C or higher. If the temperature of the colloidal silicon dioxide is below 65°C, the silicon dioxide particles aggregate when modified with a sulfonic acid group. Therefore, silicon dioxide particles with an average secondary particle size of 20 nm or less cannot be obtained. The upper limit of the temperature is not particularly restricted, as long as the boiling of the reaction solvent can be suppressed. The temperature is preferably 100°C or lower, and more preferably 90°C or lower.

[0037] In the manufacturing process of the present invention, after the addition of a silane adhesion promoter with a mercapto group to colloidal silicon dioxide, the functional group is converted into a sulfonic acid group.

[0038] Any colloidal silicon dioxide can be used as a raw material, provided it has a silanol group on its surface. However, considering the need to avoid diffusible metal impurities or corrosive ions such as chlorine in semiconductors, colloidal silicon dioxide obtained by hydrolysis and condensation of a hydrolyzable silicon compound (e.g., alkoxysilane or its derivative) used as the raw material is preferred. Such a silicon compound can be used singly or in a mixture of two or more.

[0039] In the present invention, the silicon compound is preferably alkoxysilane, represented by the following formula (1) or a derivative thereof. Si(OR)4 (1) where R is an alkyl group, preferably a lower alkyl group with 1 to 8 carbon atoms and more preferably a lower alkyl group with 1 to 4 carbon atoms.

[0040] Examples of R are a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, and a hexyl group. Tetramethoxysilane, wherein R is a methyl group, tetraethoxysilane, wherein R is an ethyl group, and tetraisopropoxysilane, wherein R is an isopropyl group, are preferred. Examples of derivatives of alkoxysilane are low-condensation compounds obtained by partial hydrolysis of alkoxysilane. In the present invention, tetramethoxysilane is preferably used because the hydrolysis rate can be easily controlled, ultrafine silicon dioxide particles in the single-digit nanometer range can be readily obtained, and the amount of unreacted residual material is small.

[0041] The silicon compound is hydrolyzed in a reaction solvent and condensed to colloidal silicon dioxide. Water or a water-containing organic solvent is used as the reaction solvent.

[0042] The organic solvent can be a hydrophilic organic solvent. Examples of organic solvents include alcohols such as methanol, ethanol, isopropanol, n-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, and 1,4-butanediol, as well as ketones such as acetone and methyl ethyl ketone.

[0043] The amount of water added to the organic solvent is not limited, as long as water is present in a quantity required for the hydrolysis of the silicon compound. A preferred amount is approximately 2 to 200 moles per mole of the silicon compound.

[0044] Preferably, a basic catalyst is added to the reaction solvent to make it alkaline. This adjusts the pH of the reaction solvent preferably to 8 to 11, more preferably to 8.5 to 10.5. This enables the rapid formation of colloidal silicon dioxide. The type of basic catalyst is not particularly restricted. The basic catalyst is preferably an organic base catalyst without metal components to avoid contamination by metal impurities. In particular, a nitrogen-containing organic base catalyst is preferred. Examples of such organic base catalysts are ethylenediamine, diethylenetriamine, triethylenetetramine, ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide (TMAH), tetramethylguanidine, 3-ethoxypropylamine, dipropylamine, and triethylamine.These can be used individually or in a combination of two or more. Ammonia is preferred due to its high volatility, excellent catalytic activity, and ease of removal in the subsequent step. To increase the particle density of the silicon dioxide particles, it is preferred to choose an organic base catalyst with a boiling point of 90°C or higher, so that it does not evaporate readily even at higher reaction temperatures. A catalyst consisting of at least one tetramethylammonium hydroxide and 3-ethoxypropylamine is preferred.

[0045] In the present invention, after a silane adhesion promoter with a mercapto group, which can be chemically converted into a sulfonic acid group, is added to the colloidal silicon dioxide, the mercapto group is converted into a sulfonic acid group, thereby modifying the colloidal silicon dioxide with a sulfonic acid group. This is based on the fact that a silane adhesion promoter with a sulfonic acid group is difficult to obtain, since a sulfonic acid group, which has a high acidity, induces hydrolysis.

[0046] Examples of silane adhesion promoters with a mercapto group are 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane and 2-mercaptoethyltriethoxysilane.

[0047] One of the silane adhesion promoters with a mercapto group can be used individually or in a mixture of two or more.

[0048] When an adhesion promoter is added to colloidal silicon dioxide, the colloidal silicon dioxide preferably contains a hydrophilic organic solvent, taking into account the solubility of the adhesion promoter. In this respect, the reaction solution contains alcohol when colloidal silicon dioxide is obtained by the Stöber process, in which alkoxysilane is hydrolyzed and condensed by a basic catalyst in an alcohol-water medium, so that no additional hydrophilic organic solvent needs to be added. In this case, it is preferred if a hydrophilic organic solvent is present in an amount of 5% by mass or more, based on the water content of the colloidal silicon dioxide, so that the reaction solution can be concentrated as needed.

[0049] However, if a silane adhesion promoter is added to the water-dispersed colloidal silicon dioxide, the hydrophilic solvent is added in an amount sufficient to dissolve the silane adhesion promoter. Examples of hydrophilic organic solvents include alcohols such as isopropyl alcohol, ethanol, and methanol. It is particularly preferable to use the same alcohol produced by the hydrolysis of the silicon compound. This is because using the same alcohol produced by the hydrolysis of the silicon compound facilitates the recovery and reuse of the solvent.

[0050] The amount of added adhesion promoter is preferably about 0.1 to 10% by mass, based on silicon dioxide. If the added amount is within the aforementioned range, the zeta potential is more stable under acidic conditions. If the upper limit of the added amount is set within the aforementioned range, the colloidal silicon dioxide exhibits less time-dependent gelation.

[0051] The reaction time upon addition of an adhesion promoter is not limited, but is preferably 10 minutes to 10 hours and more preferably 30 minutes to 2 hours. The pH of the colloidal silicon dioxide upon addition of an adhesion promoter is also not limited, but is preferably 7 or higher and 11 or lower. If the upper limit of the pH is set within the aforementioned range, the silane adhesion promoter reacts more readily with the silicon dioxide surface, thereby further suppressing self-condensation between the molecules of the silane adhesion promoter.

[0052] In the step described above, an oxidizing agent is added along with a silane adhesion promoter containing a mercapto group. The mercapto group on the silicon dioxide surface is oxidized by the use of the oxidizing agent.

[0053] Examples of oxidizing agents include nitric acid, hydrogen peroxide, oxygen, ozone, organic peracids (percarboxylic acids), bromine, hypochlorite, potassium permanganate, and chromic acid. Among these oxidizing agents, hydrogen peroxide and organic peracids (peracetic acid, perbenzoic acids) are preferred because they are relatively easy to handle and exhibit good oxidation yields. From the perspective of the byproducts formed during the reaction, hydrogen peroxide is particularly favored.

[0054] One of the oxidizing agents can be used individually or a mixture of two or more.

[0055] The amount of added oxidizing agent is preferably 3 to 100 times the amount of the silane adhesion promoter. The upper limit of the added amount is not particularly restricted, but is preferably about 50 times the amount of the silane adhesion promoter. In the colloidal silicon dioxide and the silane adhesion promoter, functional groups other than those oxidized (converted) to sulfone groups have stable structures in an oxidation reaction, thus suppressing the formation of byproducts.

[0056] The colloidal silicon dioxide with a sulfonic acid group-modified surface, obtained by the above process, sometimes contains a solvent other than water. Therefore, the dispersion medium, which mainly contains the reaction solvent, can be replaced with water to further improve the long-term storage stability of the colloidal silicon dioxide. The reaction solvent can be replaced with water after the addition of an adhesion promoter and before the addition of an oxidizing agent.

[0057] The method for replacing the dispersion medium, which mainly contains the reaction solvent, with water is not particularly limited. In one example, water can be added dropwise while the colloidal silicon dioxide is heated. In another example, the colloidal silicon dioxide is separated from the dispersion medium, which mainly contains the reaction solvent, by precipitation, separation, centrifugation, etc., and the colloidal silicon dioxide is redispersed in water.

[0058] The colloidal silicon dioxide of the present invention described above can be produced by the manufacturing process comprising the steps described above. Examples

[0059] The present invention is specifically described with reference to the examples, which, however, do not limit the present invention. Example 1: Step in the synthesis of colloidal silicon dioxide

[0060] 8836 g of pure water as solvent were placed in a flask and 13.968 g of 3-ethoxypropylamine as an alkaline catalyst were added to prepare a mother liquor. The mother liquor was heated to an internal temperature of 85°C, and then 1534 g of tetramethyl orthosilicate were added to the mother liquor at a constant rate over 15 minutes while the temperature was adjusted to maintain the internal temperature, followed by 30 minutes of stirring, resulting in a reaction solution with a solids concentration of approximately 6% by mass. Modification step with sulfonic acid group

[0061] 900 g of the reaction solution obtained in the step for the synthesis of colloidal silicon dioxide were collected and heated to 80°C under normal pressure. 2.530 g of 3-mercaptopropyltrimethoxysilane and 11.684 g of a 30% aqueous hydrogen peroxide solution were added to the heated reaction solution. Subsequently, methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 6% by mass. Example 2

[0062] 900 g of the reaction solution obtained in the step for the preparation of colloidal silicon dioxide in Example 1 were collected and heated to 80°C under normal pressure. 0.628 g of 3-mercaptopropyltrimethoxysilane and 2.901 g of a 30% aqueous hydrogen peroxide solution were added to the heated reaction solution. Subsequently, methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 6% by mass. Example 3

[0063] 900 g of the reaction solution obtained in the step for the preparation of colloidal silicon dioxide in Example 1 were collected and heated to 65°C under normal pressure. 2.530 g of 3-mercaptopropyltrimethoxysilane and 11.684 g of a 30% aqueous hydrogen peroxide solution were added to the heated reaction solution. Subsequently, methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 6% by mass. Example 4

[0064] The reaction solution obtained in the step for the preparation of colloidal silicon dioxide in Example 1 was heated and concentrated, yielding a concentrate with a solids concentration of 10% by mass. 930 g of the concentrate were collected and heated to 80°C under atmospheric pressure. 1.116 g of 3-mercaptopropyltrimethoxysilane and 5.154 g of a 30% aqueous hydrogen peroxide solution were added to the heated concentrate. Subsequently, methanol was displaced by water while pure water was added to maintain a constant volume, thus producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 10% by mass. Example 5

[0065] The reaction solution obtained in the step for the preparation of colloidal silicon dioxide in Example 1 was heated and concentrated, yielding a concentrate with a solids concentration of 17% by mass. 980 g of the concentrate were collected and heated to 80°C under atmospheric pressure. 1.999 g of 3-mercaptopropyltrimethoxysilane and 9.232 g of a 30% aqueous hydrogen peroxide solution were added to the heated concentrate. Methanol was then displaced by water while pure water was added to maintain a constant volume, thus producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 17% by mass. Example 6

[0066] 7500 g of pure water were placed in a flask as a solvent, and 11.640 g of 3-ethoxypropylamine were added as an alkaline catalyst to prepare a mother liquor. The mother liquor was heated to an internal temperature of 85°C, and then 2740 g of tetramethyl orthosilicate were added to the mother liquor at a constant rate over 120 minutes while the temperature was adjusted to maintain the internal temperature. This was followed by 15 minutes of stirring and the subsequent addition of 7.00 g of 3-ethoxypropylamine, yielding a reaction solution with a solids concentration of approximately 11% by mass. The reaction solution was then heated and concentrated under atmospheric pressure, resulting in a concentrate with a silicon dioxide concentration of 20% by mass.

[0067] 1000 g of the concentrate were collected and heated to 65°C under normal pressure. 2.400 g of 3-mercaptopropyltrimethoxysilane and 11.083 g of a 30% aqueous hydrogen peroxide solution were added to the heated concentrate. Methanol was then displaced by water while pure water was added to maintain a constant volume, thus producing colloidal silicon dioxide. The resulting colloidal silicon dioxide had a silicon dioxide particle content of 20% by mass. Comparative example 1

[0068] 900 g of the reaction solution obtained in the step for the preparation of colloidal silicon dioxide in Example 1 were collected, and methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 6% by mass. Comparative example 2

[0069] 6588 g of methanol, 323 g of pure water, and 89 g of 28% ammonia solution were mixed in a flask to prepare a mother liquor. The mother liquor was heated to an internal temperature of 60°C, and then 782 g of tetramethoxysilane were added to the mother liquor at a constant rate over a period of 87 minutes while the temperature was adjusted to maintain the internal temperature. This was followed by 60 minutes of stirring, resulting in a reaction solution with a solids concentration of approximately 4% by mass.

[0070] 740 g of the reaction solution obtained in the preceding step were collected, and methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 4% by mass. Comparative example 3

[0071] 5000 g of methanol, 2050 g of pure water, and 300 g of 28% ammonia solution were mixed in a flask to prepare a mother liquor. The temperature of the mother liquor was maintained at 35°C, and a mixture of 1400 g of tetramethoxysilane and 750 g of methanol was added to the mother liquor at a constant rate over a period of 300 minutes, while the temperature was adjusted to maintain a constant internal temperature. The mixture was then stirred for 60 minutes, resulting in a reaction solution with a solids concentration of approximately 6% by mass.

[0072] 740 g of the reaction solution obtained in the preceding step were collected, and methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 6% by mass. Comparative example 4

[0073] 2945 g of methanol, 1459 g of pure water, and 381 g of 28% ammonia solution were mixed in a flask to prepare a mother liquor. The mother liquor was heated to an internal temperature of 45°C, and then 3497 g of tetramethoxysilane were added to the mother liquor at a constant rate over a period of 377 minutes while the temperature was adjusted to maintain the internal temperature. This was followed by 60 minutes of stirring, resulting in a reaction solution with a solids concentration of approximately 17% by mass.

[0074] 740 g of the reaction solution obtained in the preceding step were collected, and 1.232 g of 3-mercaptopropyltrimethoxysilane and 5.691 g of a 30% aqueous hydrogen peroxide solution were added at 25°C under atmospheric pressure. Methanol was then displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 17% by mass. Comparative example 5

[0075] 5925 g of methanol, 304 g of pure water, and 59 g of 28% ammonia solution were mixed in a flask to prepare a mother liquor. The mother liquor was heated to an internal temperature of 60°C, and then 726 g of tetramethoxysilane and 344 g of methanol were added to the mother liquor at a constant rate over a period of 127 minutes while the temperature was adjusted to maintain the internal temperature. This was followed by 60 minutes of stirring, resulting in a reaction solution with a solids concentration of approximately 4% by mass.

[0076] 740 g of the reaction solution obtained in the preceding step were collected, and 0.288 g of 3-mercaptopropyltrimethoxysilane and 1.330 g of a 30% aqueous hydrogen peroxide solution were added at 25°C under atmospheric pressure. Subsequently, methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 4% by mass. Comparative example 6

[0077] 900 g of the reaction solution obtained in the step for the preparation of colloidal silicon dioxide in Example 1 were collected, and 2.530 g of 3-mercaptopropyltrimethoxysilane and 11.684 g of a 30% aqueous hydrogen peroxide solution were added at 25°C under atmospheric pressure. Subsequently, methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 6% by mass. Comparative example 7

[0078] 900 g of the reaction solution obtained in the step for the preparation of colloidal silicon dioxide in Example 1 were collected and heated to 40°C under normal pressure. 2.530 g of 3-mercaptopropyltrimethoxysilane and 11.684 g of a 30% aqueous hydrogen peroxide solution were added to the heated reaction solution. Methanol was then displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 6% by mass. Comparative example 8

[0079] 740 g of the reaction solution obtained in the step for preparing the reaction solution in Comparative Example 2 were collected, and 0.352 g of 3-mercaptopropyltrimethoxysilane and 1.626 g of a 30% aqueous hydrogen peroxide solution were added at 25°C under atmospheric pressure. Subsequently, methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 4% by mass. Comparative example 9

[0080] 740 g of the reaction solution obtained in the step for preparing the reaction solution in Comparative Example 3 were collected, and 0.517 g of 3-mercaptopropyltrimethoxysilane and 2.385 g of a 30% aqueous hydrogen peroxide solution were added at 25°C under atmospheric pressure. Subsequently, methanol was displaced by water while pure water was added to maintain a constant volume, thereby producing colloidal silicon dioxide. The colloidal silicon dioxide produced had a silicon dioxide particle content of 6% by mass.

[0081] The colloidal silicon dioxide obtained in the examples and comparative examples as described above was evaluated according to the following procedure. Average primary particle size

[0082] The colloidal silicon dioxide was pre-dried on a hot plate and then heated at 800°C for 1 hour to prepare a sample. The BET-specific surface area of ​​the prepared sample was measured. The average primary particle size (nm) of the silicon dioxide particles in the colloidal silicon dioxide was calculated using the value 2727 / BET-specific surface area (m²). 2 / g) calculated, assuming a particle density of silicon dioxide of 2.2. Average secondary particle size

[0083] Colloidal silicon dioxide was added to a 0.3 wt% aqueous citric acid solution and homogenized to a silicon dioxide concentration of 0.8 wt% to prepare a sample for dynamic light scattering. The average secondary particle size (nm) of the sample was measured using dynamic light scattering (ELSZ-2000S, available from Otsuka Electronics Co., Ltd.). Aggregation ratio

[0084] The aggregation ratio was calculated using the following formula: average secondary particle size / average primary particle size. Zeta potential

[0085] Hydrochloric acid was added to the colloidal silicon dioxide to adjust the pH to 3.0. The zeta potential was measured by electrophoretic light scattering using ELS-Z, available from Otsuka Electronics Co., Ltd. Sulfonic acid group content

[0086] Colloidal silicon dioxide was subjected to ultracentrifugation (5°C, 50,000 rpm) for 1 hour to obtain silicon dioxide solids. The silicon dioxide solids were suspended in ultrapure water and ultrasonically purified. The purification water was removed to obtain a silicon dioxide powder. The silicon dioxide powder was analyzed using an X-ray photoelectron spectrometer (product name: AXIS NOVA, available from Shimadzu Corporation). The analysis was performed in the O 1s, C 1s, S 2s, and Si 2p regions using Al Kα (15 kV, 10 mA) as the X-ray source. The peak of S atoms originating from sulfonic acid groups was identified in the region S 2s (bond energy: 230 eV) and the sulfonic acid group content (atomic percent) was calculated from the ratio of the number of S atoms originating from the sulfonic acid groups to the total number of atoms detected. particle density

[0087] The colloidal silicon dioxide was dried and solidified on a hot plate at 150°C and then held in an oven at 300°C for 1 hour. The particle density of the silicon dioxide particles was then measured using a liquid immersion method with ethanol. Dispersion stability under acidic conditions (pH value of 3.0)

[0088] To the colloidal silicon dioxide prepared in the examples and comparative examples, ultrapure water and 1 mol / L hydrochloric acid were added to adjust the silicon dioxide concentration to 3 wt% and the pH to 3.0, thus preparing samples. The resulting samples were hermetically sealed in a fluorocarbon resin container and stored at 25°C for 1 month. The mean secondary particle size was measured before and after storage, and the increase in mean secondary particle size was calculated. If the increase in mean secondary particle size exceeded 3.0 nm, the dispersion stability of the silicon dioxide particles was rated as poor, as aggregation had increased. Conversely, if the increase in mean secondary particle size was less than 3.0 nm, the dispersion stability of the silicon dioxide particles was rated as good. Surface roughness RMS of the polished surface

[0089] The colloidal silicon dioxide prepared in the examples and comparative examples was diluted with ultrapure water to a silicon dioxide concentration of 3.0 wt%, thus producing polishing compositions. 3 cm square silicon wafers, each with a silicon dioxide film formed on their surface, were polished with the resulting polishing compositions under the following conditions. Polishing machine: NF-300CMP, available from Nano Factor Co., Ltd. Polishing pad: IC1000TM Pad, available from NITTA DuPont Incorporated Slurry feed rate: 50 ml / min Polishing head speed: 32 rpm Polishing plate speed: 32 rpm Polishing pressure: 4 psi Polishing time: 2 min

[0090] For each of the polished silicon wafers, the surface roughness of the polished surface was evaluated using an atomic force microscope under the following conditions: Atomic force microscope: SPM-9700HT, available from Shimadzu Corporation Cantilever: Micro Cantilever OMCL-AC240TS-R3, available from Olympus Observation mode: Dynamic Scan area: 3.0 µm square Scan speed: 1.00 Hz Number of viewing fields: Five viewing fields were observed per polished wafer. Calculation method for surface roughness: The mean squared roughness (RMS) was calculated from five viewing fields to determine the surface roughness of the polished surface. Content of metallic impurities

[0091] The content of metallic impurities was measured using an atomic absorption spectrometer. The total content of sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt in the colloidal silicon dioxide was determined as the content of metallic impurities.

[0092] The silicon dioxide particle content of the colloidal silicon dioxide was calculated by drying and solidifying 10.0 g of the colloidal silicon dioxide on a hot plate at 150°C, heating the colloidal silicon dioxide for 1 hour at 800°C to remove moisture, and inserting the amount of solids obtained, Wg, into the following formula: Silicon dioxide particle content of the colloidal silicon dioxide [%] = (W / 10,0) × 100.

[0093] Table 1 shows the results. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2004-315300A

[0007] WO 2023-007938

[0007]

Claims

[1] Colloidal silicon dioxide comprising silicon dioxide particles wherein the silicon dioxide particles have an average secondary particle size of 20 nm or less, as measured by dynamic light scattering, and a zeta potential of -20 mV or less, as measured at a pH of 3, and are surface-modified with a sulfonic acid group. [2] Colloidal silicon dioxide according to claim 1, wherein the silicon dioxide particles have a sulfonic acid group content of 0.02 atm% or more. [3] Colloidal silicon dioxide according to claim 1 or 2, wherein the silicon dioxide particles have an average primary particle size of 18 nm or less, calculated from a BET-specific surface area. [4] Method for producing colloidal silicon dioxide, comprising a step of adding a silane adhesion promoter with a mercapto group and an oxidizing agent to colloidal silicon dioxide, wherein the temperature of the colloidal silicon dioxide in this step is 65°C or higher. [5] Manufacturing process according to claim 4, wherein the silane adhesion promoter with a mercapto group is at least one selected from the group consisting of 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane and 2-mercaptoethyltriethoxysilane. [6] Manufacturing process according to claim 4 or 5, wherein the oxidizing agent is at least one selected from the group consisting of nitric acid, hydrogen peroxide, oxygen, ozone, organic peracid, bromine, hypochlorite, potassium permanganate and chromic acid.