Sulfonic acid-modified colloidal silica, method for producing the same, and polishing composition

Abstract

This invention provides a means to further improve stability and detergency under acidic conditions. The present invention is a sulfonic acid modified colloidal silicon oxide, wherein the amount of sulfonic acid groups per 1g of particles is more than 1.5μmol and less than 13.0μmol.

Description

Technical Field

[0001] This invention relates to sulfonic acid-modified colloidal silicon oxide. Modified colloidal silica. Prior Technology

[0002] In recent years, with the increasing use of multilayer wiring on semiconductor substrates, physical polishing of semiconductor substrates is employed during manufacturing processes to achieve planarization, a technique known as Chemical Mechanical Polishing (CMP). CMP uses a polishing composition (slurry) containing abrasive particles such as silicon oxide, aluminum oxide, or cerium oxide, as well as etching inhibitors and surfactants, to planarize the surface of the object being polished, such as a semiconductor substrate. Specifically, it is used in steps such as shallow trench isolation (STI), planarization of interlayer insulating films (ILD films), tungsten plug formation, and the formation of multilayer wiring composed of copper and low-dielectric films. The abrasive compositions (slurries) used in CMP have undergone various reviews depending on the type of material being abraded, and the abrasive grains contained in the abrasive compositions are also the same. For example, Japanese Patent Application Publication No. 2012-40671 (which should be disclosed in US Patent Application Publication No. 2013 / 0146804) has proposed an abrasive composition that can abrade silicon nitride films at high speeds, which contains colloidal silicon oxide immobilized with organic acids such as sulfonic acid, and has a pH within a specific range. Summary of the Invention

[0003] However, in the abrasive composition described in Japanese Patent Application Publication No. 2012-40671 (US Patent Application Publication No. 2013 / 0146804), the stability of the organic acid-immobilized colloidal silica under acidic conditions could still be improved. Furthermore, when using the abrasive composition described in Japanese Patent Application Publication No. 2012-40671 (US Patent Application Publication No. 2013 / 0146804), even after cleaning following abrasive grinding, there is a tendency for more abrasive residue to remain on the surface of the object being ground. Therefore, there is still room for improvement in further enhancing the cleanability of the residue and reducing the amount of residue on the surface of the object being ground. Therefore, the object of the present invention is to provide means that can further improve stability and detergency under acidic conditions. The inventors carefully examined the aforementioned issues. They discovered that by using sulfonic acid-modified colloidal silicon oxide with a sulfonic acid group content of 1.5 μmol to 13.0 μmol per 1g of particles, the aforementioned issues were resolved, thus completing the present invention. Implementation

[0004] The present invention will now be described. However, the present invention is not limited to the following embodiments. According to one embodiment of the present invention, a sulfonic acid-modified colloidal silicon oxide is provided in which the sulfonic acid group content (sulfonic acid group content) per 1g of particles is 1.5μmol to 13.0μmol or less. The sulfonic acid-modified colloidal silicon oxide of the present invention exhibits improved stability under acidic conditions, and when used as an abrasive grain for grinding, it further reduces residue on the surface of the ground object after grinding. The following describes in detail the embodiments of the present invention. However, the present invention is not limited to the embodiments described below, and various modifications can be made within the scope of the patent application. The embodiments described in this specification can be arbitrarily combined to form other embodiments. In this specification, unless otherwise specified, the operation and physical property measurements are performed under the conditions of room temperature (between 20°C and 25°C) and relative humidity (between 40%RH and 50%RH). [Sulfonic acid modified colloidal silicon oxide] The sulfonic acid-modified colloidal silicon oxide particles of this invention have a sulfonic acid group content of 1.5 μmol / g to 13.0 μmol / g per 1g. With this range of sulfonic acid group content, the sulfonic acid-modified colloidal silicon oxide of this invention exhibits improved stability under acidic conditions, further enhanced detergency after grinding, and reduced residue on the surface of the object being ground. When the amount of sulfonic acid groups per 1g of particles is less than 1.5 μmol / g, the sulfonic acid-modified colloidal silica becomes prone to gelation under acidic conditions, resulting in reduced stability. On the other hand, when the amount of sulfonic acid groups per 1g of particles exceeds 13.0 μmol / g, the sulfonic acid-modified colloidal silica becomes prone to adhering to the surface of the workpiece being ground, reducing its cleanability after grinding and making it difficult to reduce residue on the surface of the workpiece. The amount of sulfonic acid groups per 1g of particles in the sulfonic acid-modified colloidal silica of the present invention is preferably 3.0 μmol / g to 10.5 μmol / g, and more preferably 3.0 μmol / g to 8.5 μmol / g. In this specification, the amount of sulfonic acid group per 1g of sulfonic acid modified colloidal silicon oxide particles is a value measured by the following method. <Measurement of Sulfonic Acid Content> In silica particles (sulfonic acid modified colloidal silica) with sulfonic acid groups (-SO3H) immobilized on their surface, the amount of sulfonic acid groups on the surface can be calculated using the following formula, taking into account that 1 mol of monovalent potassium ions (K+) will react with 1 mol of monovalent organic acid. The amount of sulfonic acid groups per 1g of silica particles (as a solid component) (unit: μmol / g) can be calculated based on the following formula: In the above formula, nS represents the amount of sulfonic acid groups per 1g of surface-treated silicon oxide particles (as a solid component) [unit: μmol / g]; K represents the analytical value of potassium in solids [unit: ppm by mass]; Aw represents the atomic weight of potassium [unit: g / mol]: Specifically, firstly, 21.0 g of a 0.01 mol / L hydrochloric acid-0.01 mol / L potassium chloride mixture was added to 21.0 g of a 19.5% by mass aqueous solution of silicon oxide. After thorough mixing, the resulting mixture was centrifuged according to the following procedure: Procedure: A special resin tube was placed in the above mixture (silica sol) and centrifuged at 26,000 rpm (26,000 min⁻¹) for 2 hours. The precipitate was washed with ultrapure water and ion-exchanged water. The precipitate was then evaporated, dried, and solidified to form a sample. A Beckman Coulter Avanti HP-30I high-performance, high-speed cooled centrifuge was used as the centrifugal separation device. Next, the potassium content in the obtained sample was measured using an inductively coupled plasma (ICP) luminescence analyzer according to the following procedure: Procedure: Add 6 mL of nitric acid and 15 mL of hydrofluoric acid to 4 g of the sample obtained by centrifugation as described above, and allow it to evaporate and solidify. After drying and solidification, add 0.5 mL of nitric acid and approximately 20 mL of ultrapure water, and heat until steam is generated. The total amount of the recovered mixture is divided into 50 g with ultrapure water, and then 3.0 g of this mixture is taken and diluted with ultrapure water to make 30 g. The mixture is then measured using an ICP luminescence analyzer (manufactured by Shimadzu Corporation, model: ICPS-8100). The amount of sulfonic acid groups in the sulfonic acid-modified colloidal silicon oxide of the present invention can be controlled by the amount of silane coupling agent used during the sulfonic acid modification treatment of the raw material colloidal silicon oxide, the oxidation treatment conditions, etc. Hereinafter, a method for manufacturing the sulfonic acid-modified colloidal silicon oxide according to a preferred embodiment of the present invention will be described. [Manufacturing method of sulfonic acid modified colloidal silicon oxide] The method for manufacturing sulfonic acid-modified colloidal silicon oxide according to the present invention is not particularly limited, but a method that includes applying sulfonic acid modification treatment to the raw material colloidal silicon oxide is preferred. The following describes this manufacturing method. <Raw material: colloidal silicon oxide> The raw material colloidal silicon oxide can be manufactured, for example, by the sol-gel method. The raw material colloidal silicon oxide manufactured by the sol-gel method is preferred because it has a low content of corrosive ions such as diffusible metal impurities or chloride ions in semiconductors. The manufacture of raw material colloidal silicon oxide using the sol-gel method is carried out using conventionally known methods. Specifically, it involves a hydrolysis-condensation reaction of a hydrolyzable silicon compound (e.g., alkoxysilanes or their derivatives) to obtain the raw material colloidal silicon oxide. One type of silicon compound can be used alone, or two or more can be used in combination. Furthermore, the raw material colloidal silicon oxide can also be manufactured by methods other than the sol-gel method. In one embodiment of the present invention, the silicon compound is preferably an alkoxysilane or a derivative thereof as shown in the following general formula (1). In the above general formula (1), R is an alkyl group, preferably a lower alkyl group having 1 to 8 carbon atoms, and more preferably a lower alkyl group having 1 to 4 carbon atoms. Examples of R include methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl, etc. Among these, tetramethoxysilane with R being methyl, tetraethoxysilane with R being ethyl, or tetraisopropoxysilane with R being isopropyl are preferred. Furthermore, examples of alkoxysilane derivatives include low condensate products obtained by partially hydrolyzing alkoxysilane. In this invention, tetramethoxysilane is preferred because it is easy to control the hydrolysis rate, easy to obtain small silicon oxide particles, and has minimal unreacted residue. The aforementioned silicon compound undergoes hydrolysis and condensation in the reaction solvent to form colloidal silicon oxide. Water or an organic solvent containing water can be used as the reaction solvent. Examples of hydrophilic 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. Among these organic solvents, alcohols such as methanol, ethanol, and isopropanol are particularly preferred. From the viewpoint of post-reaction solvent treatment, it is preferable to use alcohols having the same alkyl group (R) as the silicon compound in the reactants (e.g., methanol for tetramethoxysilane). One of these organic solvents can be used alone, or two or more can be used in combination. There is no particular limitation on the amount of organic solvent used, but it is preferable to use between 5 and 50 mol per mol of silicon compound. A level of 5 mol or more ensures sufficient compatibility with the silicon compound, while a level of less than 50 mol will inhibit a decrease in manufacturing efficiency. There is no particular limitation on the amount of water added to the organic solvent, as long as it is sufficient for the hydrolysis of the silicon compound; a level of between 2 and 15 mol per mol of silicon compound is preferable. Furthermore, the amount of water mixed in the organic solvent significantly affects the particle size of the resulting colloidal silicon oxide. Increasing the amount of water increases the particle size of the colloidal silicon oxide, while decreasing the amount of water decreases its particle size. Therefore, by changing the mixing ratio of water and organic solvent, the particle size of the manufactured colloidal silicon oxide can be arbitrarily adjusted. It is preferable to adjust the reaction solvent to alkaline by adding an alkaline catalyst to the reaction solvent of the hydrolysis-condensation reaction of silicon compounds used to obtain colloidal silicon oxide (Stober process). This allows the reaction solvent to be preferably adjusted to a pH between 8 and 11, and more preferably between 8.5 and 10.5, thus enabling rapid formation of colloidal silicon oxide. From the viewpoint of preventing impurity contamination, organic amines or ammonia are preferred as alkaline catalysts, especially ethylenediamine, diethylenetriamine, triethylenetetramine, ammonia, urea, ethanolamine, and tetramethylammonium hydroxide. To hydrolyze and condense silicon compounds in a reaction solvent, the silicon compound is added to an organic solvent, typically at a temperature between 0°C and 100°C, preferably between 0°C and 50°C, and then stirred. By stirring the silicon compound in an organic solvent containing water to perform hydrolysis and condensation, colloidal silicon oxide with uniform particle size can be obtained. This form of sulfonic acid-modified colloidal silicon oxide system is related to the Japanese patent. Similarly, the technology described in Japanese Patent Application Publication No. 2010-269985 can be obtained by modifying the raw material colloidal silica produced by the sol-gel method through the above-described operation. However, the point regarding the use of a reduced amount of microparticles as the raw material colloidal silica is related to the Japanese Patent Application Publication No. 2010-269985. The technology described in Publication No. 2010-269985 has been improved. Specifically, the sulfonic acid modified colloidal silicon oxide of this form is characterized by modifying the raw material colloidal silicon oxide, wherein the raw material colloidal silicon oxide has a particle size distribution ratio of less than 10% of the volume average particle size based on the Heywood diameter (equivalent circular diameter) obtained by image analysis using a scanning electron microscope. When the concentration of organic solvent in the colloidal silica produced by the above-described hydrolysis-condensation reaction (sol-gel method) is 1% by mass or more, the organic solvent coexisting with the colloidal silica can be removed by reducing the concentration of residual organic solvent in the colloidal silica to less than 1% by mass, thereby reducing the proportion of microparticles contained in the raw material colloidal silica to less than 10%. Here, "whether the concentration of residual organic solvent in the colloidal silica is less than 1% by mass" is synonymous with "whether organic solvent is detected in the colloidal silica" in the measurement method of organic solvent concentration (methanol concentration in the example) using gas chromatography described in the following examples. That is, the above-described "method of reducing the concentration of residual organic solvent in the colloidal silica to less than 1% by mass" can also be referred to as "the method of reducing the concentration of organic solvent in the colloidal silica measured by the gas chromatography measurement method described in the examples to below the detection limit". Therefore, by reducing the concentration of organic solvents contained in colloidal silica, the amount of fine particles contained in the raw colloidal silica can be reduced. Furthermore, the more the amount of organic solvents contained in the colloidal silica is reduced, the more the amount of fine particles contained in the raw colloidal silica can be reduced. Moreover, the concentration of organic solvents in the colloidal silica obtained by the aforementioned Stuber process is typically 1% by mass or more. Therefore, according to another aspect of the present invention, a method for manufacturing sulfonic acid-modified colloidal silica is provided, which involves removing organic solvents coexisting with colloidal silica by reducing the concentration of residual organic solvents in colloidal silica, which, like colloidal silica obtained by the Stuber process, is at least 1% by mass, to less than 1% by mass. After obtaining raw colloidal silica, the raw colloidal silica is then subjected to sulfonic acid modification to obtain sulfonic acid-modified colloidal silica. One method for removing organic solvents coexisting with colloidal silica is to heat the dispersion of colloidal silica (silica sol) and distill off the organic solvents. In this case, by replacing the organic solvents to be removed with water, the volume of the colloidal silica dispersion can be maintained. Furthermore, regarding the pH of the colloidal silica dispersion during the distillation of organic solvents, it is preferable to maintain a pH of 7 or higher. In this way, along with the distillation of organic solvents, Oswald curing can also be used to introduce fine particles onto the surface of the main particles of colloidal silica, thereby further reducing the amount of fine particles. Furthermore, the method for removing organic solvents coexisting with colloidal silica, as cited above, is used to illustrate in detail a method for reducing the number distribution ratio of microparticles contained in the raw material colloidal silica to less than 10%. However, different methods can also be used to reduce the number distribution ratio of microparticles contained in the raw material colloidal silica to less than 10%. Examples of such methods include using oligomers as raw materials, optimizing the composition during synthesis, subjecting the synthesis to high temperature and pressure treatment, and centrifuging after synthesis. Of course, other methods can also be used. <Sulfonic Acid Modification Treatment (Modification Steps)> As described above, the sulfonic acid-modified colloidal silicon oxide of the present invention can be obtained, for example, by applying sulfonic acid modification treatment to raw colloidal silicon oxide manufactured by the sol-gel method. This modification step includes: a first reaction step of heating the raw colloidal silicon oxide in the presence of a silane coupling agent having functional groups that can be chemically converted to sulfonic acid groups to obtain a reactant; and a second reaction step of processing the reactant obtained in the first reaction step to convert the functional groups to sulfonic acid groups. (Reaction Step 1) The first reaction step involves heating the raw material, colloidal silica, in the presence of a silane coupling agent with a functional group that can be chemically converted into a sulfonic acid group. This yields a reactant (a silane coupling agent with a functional group that can be chemically converted into a sulfonic acid group bonded to the surface of silica particles). Here, as necessary, various treatment steps can be applied to the obtained raw material colloidal silica before the first reaction step. For example, one such treatment step is to reduce the viscosity of the raw material colloidal silica. This reduction in viscosity can be achieved, for example, by adding an alkaline solution (an aqueous solution of various alkalis such as ammonia) or an organic solvent to the raw material colloidal silica. There are no particular limitations on the amount of alkaline solution or organic solvent added; it can be appropriately set considering the viscosity of the obtained raw material colloidal silica after addition. In this way, by implementing the step of reducing the viscosity of the raw material colloidal silica, the initial dispersibility of the coupling agent on the colloidal silica is improved, or the aggregation of silica particles is inhibited. The first reaction step involves heating a low-content raw material, colloidal silica, in the presence of a silane coupling agent with a functional group capable of chemically converting to a sulfonic acid group, as described above. This yields the reactant. The reason for employing this method—reacting the raw material, colloidal silica, with a silane coupling agent having a functional group different from the sulfonic acid group, followed by converting the aforementioned functional group to a sulfonic acid group (the second reaction step described later)—is that it is generally difficult to reliably obtain a silane coupling agent in a sulfonic acid-substituted form. Examples of silane coupling agents that can chemically transform into sulfonic acid groups include: 1) silane coupling agents that can be converted into sulfonate groups via hydrolysis, and 2) silane coupling agents that can be converted into mercapto and / or thioether groups via oxidation. Furthermore, since sulfonic acid modification of colloidal silica surfaces is carried out in solution, it is preferable to use the latter type of coupling agent with mercapto and / or thioether groups to improve modification efficiency. Such silane coupling agents can be used alone or in combination of two or more. Moreover, commercially available or synthetic silane coupling agents can be used. Examples of silane coupling agents containing a mercapto group include 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane. Examples of coupling agents containing a thioether group include bis(3-triethoxysilylpropyl)disulfide. Alternatively, acid can be used to pre-hydrolyze the silane coupling agent before condensation reaction to form raw material colloidal silicon oxide. As described above, in order to reduce the proportion of microparticles in the raw material colloidal silica to less than 10%, when using a method to remove organic solvents coexisting with the colloidal silica, the raw material colloidal silica essentially does not contain organic solvents, and the dispersion medium of the raw material colloidal silica is essentially composed of water. On the other hand, since silane coupling agents are not easily soluble in water, it is preferable to use a certain amount or more of an organic solvent (hydrophilic solvent) to dissolve the silane coupling agent. Examples of such organic solvents (hydrophilic solvents) include methanol, ethanol, and isopropanol. Among these, it is preferable to use an alcohol of the same type as the alcohols generated by the hydrolysis of silica compounds. This is because using an alcohol of the same type as the alcohols generated by the hydrolysis of silica compounds facilitates the recovery and reuse of the solvent. Furthermore, this organic solvent (hydrophilic solvent) can be added to the raw material colloidal silica, or a mixture can be prepared by first mixing the silane coupling agent with the organic solvent (hydrophilic solvent) to obtain a mixture, and then adding the mixture to the raw material colloidal silica. The latter method is preferred. Moreover, Japanese Patent Application Publication No. 2010-269985 states, "Considering the solubility of the coupling agent, it is preferable to include a hydrophilic organic solvent in the colloidal silica. Regarding this point, in the case of obtaining colloidal silica by the Stuber process of hydrolyzing and condensing alkoxysilanes in an alcohol-water solvent using an alkaline catalyst, since the reaction solution contains alcohol, there is no need to add a further hydrophilic organic solvent." However, in a preferred embodiment of the present invention, a seemingly roundabout configuration is employed, in which the amount of organic solvent contained in the raw material colloidal silica obtained by the Stuber process is reduced to below the detection limit, and then a silane coupling agent is added. According to a preferred embodiment of the present invention, it has been clarified that even with such a roundabout configuration, the problem of the present invention can still be solved. Therefore, as described above, the present invention, which achieves effects that are not expected by those skilled in the art despite employing a configuration contrary to conventional technical knowledge, can be considered an invention that even those skilled in the art, especially those who refer to the description in Japanese Patent Application Publication No. 2010-269985, could not easily accomplish. Furthermore, there is no particular limitation on the amount of silane coupling agent used in the first reaction step, but it is preferable to be 0.1% by mass or more and less than 1.25% by mass relative to 100% by mass of the silica particles contained in the raw material colloidal silica. If the amount of silane coupling agent added is 0.1% by mass or more, the surface of the silica particles can be sufficiently anionized, resulting in excellent performance when used as an abrasive (abrasive grains in a grinding composition). On the other hand, if the amount of silane coupling agent added is less than 1.25% by mass, it can prevent the time-related gelation of the obtained reactant (sulfonic acid modified colloidal silica). In particular, from the viewpoint of further improving the stability of sulfonic acid-modified colloidal silica under acidic conditions, the amount of silane coupling agent added relative to 100% by mass of silica particles contained in the raw colloidal silica is preferably 0.25% by mass to 1.0% by mass, and more preferably 0.25% by mass to 0.8% by mass. As a preferred embodiment of the present invention, a method for manufacturing sulfonic acid-modified colloidal silicon oxide is provided, comprising: a method for removing organic solvents coexisting with colloidal silicon oxide by distillation under conditions of pH 7 or higher, wherein the residual organic solvent concentration in the colloidal silicon oxide is less than 1% by mass, thereby obtaining raw material colloidal silicon oxide; and a method for modifying the aforementioned raw material colloidal silicon oxide by sulfonic acid modification to obtain sulfonic acid-modified colloidal silicon oxide. The aforementioned modification step includes: a first reaction step of heating the aforementioned raw material colloidal silica in the presence of a silane coupling agent having a functional group that can be chemically converted into a sulfonic acid group to obtain a reactant; and a second reaction step of processing the aforementioned reactant to convert the aforementioned functional group into a sulfonic acid group; in the aforementioned first reaction step, the amount of the aforementioned silane coupling agent added is 0.1% by mass or more and less than 1.25% by mass relative to 100% by mass of silica particles contained in the aforementioned raw material colloidal silica. The amount of organic solvent (hydrophilic solvent) used to dissolve the silane coupling agent is preferably between 500% and 10,000% by mass relative to 100% by mass of the silane coupling agent, and more preferably between 1,000% and 5,000% by mass. There is no limitation on the temperature when adding the silane coupling agent, but a range from room temperature (approximately 20°C) to the boiling point of the reaction solvent is preferred. There is also no limitation on the reaction time, but 10 minutes to 10 hours is preferred, and 30 minutes to 5 hours is even better. However, from the viewpoint of completing the hydrolysis of the coupling agent, the first reaction step is preferably carried out at a temperature above 90°C for at least 30 minutes. There is also no limitation on the pH at the time of addition, but a pH between 7 and 11 is preferred. (Second reaction step) The second reaction step involves processing the reactants obtained in the first reaction step (a silica coupling agent with a functional group that can be chemically converted into a sulfonic acid group, bonded to the surface of silica particles). This process converts the "functional group that can be chemically converted into a sulfonic acid group" in the silica coupling agent into a sulfonic acid group. The specific form of the "treatment" performed to convert the "functional group that can be chemically converted into a sulfonic acid group" of the aforementioned silane coupling agent into a sulfonic acid group is not particularly limited, and can be appropriately selected according to the structure of the silane coupling agent used. For example, in the case where the aforementioned silane coupling agent 1) having a sulfonate group that can be converted into a sulfonic acid group by hydrolysis is used in the first reaction step, the functional group (sulfonate group) of the silane coupling agent can be hydrolyzed by applying a hydrolysis treatment to the aforementioned reactants. Thereby, the sulfonate group is converted into a sulfonic acid group. Furthermore, in the case where the above-mentioned silane coupling agent 2) is used in the first reaction step and has a mercapto group and / or a thioether group that can be converted into a sulfonic acid group by oxidation, the functional groups (mercapto group and / or thioether group) of the silane coupling agent can be oxidized by applying an oxidation treatment to the above reactants. In this way, the mercapto group or thioether group is converted into a sulfonic acid group. When applying oxidation treatment to the above reactants, for example, the reactants can be reacted with an oxidizing agent. 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 acid) are relatively easy to handle and have good oxidation yields, and are therefore preferred. Furthermore, considering the byproducts generated during the reaction, hydrogen peroxide is the best choice. From the viewpoint of ensuring the amount necessary for the reaction and reducing residual oxidizing agent, the amount of oxidizing agent added is preferably 3 to 5 moles of the silane coupling agent. By setting the amount of oxidizing agent added within this range, the residual oxidizing agent concentration in the obtained sulfonic acid-modified colloidal silica can be minimized. There is no particular limitation on the specific value of the residual oxidant concentration in the obtained sulfonic acid modified colloidal silicon oxide, but it is preferable to be below 1000 ppm by mass, more preferably below 700 ppm by mass, and especially preferably below 500 ppm by mass. However, if the residual oxidant concentration in the obtained sulfonic acid modified colloidal silicon oxide exceeds 1000 ppm by mass, there is a possibility that when the sulfonic acid modified colloidal silicon oxide itself or the abrasive composition made by adding sulfonic acid modified colloidal silicon oxide as an abrasive is stored or transported in a sealed container, oxidants such as hydrogen peroxide may decompose to produce gases such as oxygen, thereby increasing the internal pressure of the container. On the other hand, by reducing the residual oxidant concentration in the obtained sulfonic acid modified colloidal silicon oxide as described above, this concern about the increase in internal pressure is reduced. Furthermore, when used as a abrasive composition, it also has the advantage of suppressing the problem of wafer denting that may occur when containing a large amount of oxidant. Furthermore, regarding colloidal oxidized silica and silane coupling agents, those that are oxidized (converted) to functional groups other than sulfonic acid groups have a stable structure in the oxidation reaction and therefore do not produce byproducts. In cases where the sulfonic acid-modified colloidal silica obtained by the above method contains solvents other than water, water may be used to replace the dispersion medium, primarily the reaction solvent, to improve the long-term storage stability of the sulfonic acid-modified colloidal silica, if necessary. Furthermore, this water substitution can be performed after the addition of the silane coupling agent and before the addition of the oxidant. There are no particular limitations on the method of using water to replace solvents other than water; examples include heating the sulfonic acid-modified colloidal silica while simultaneously adding water dropwise in fixed amounts. Alternatively, methods such as separating the solvents other than water by precipitation, separation, or centrifugation of the sulfonic acid-modified colloidal silica before re-dispersing it in water may also be used. The sulfonic acid-modified colloidal silicon oxide of this invention has a low content of tiny particles composed of silicon oxide particles whose surface has been modified with sulfonic acid. Furthermore, the sulfonic acid-modified colloidal silicon oxide obtained by the manufacturing method of this invention is also superior in terms of reducing the content of metal impurities. Examples of metal impurities include, for instance, alkali metals such as sodium and potassium, alkaline earth metals such as calcium and magnesium, heavy metals and light metals such as aluminum, iron, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt. In the preferred embodiment of the sulfonic acid-modified colloidal silicon oxide of this invention, the total content of metal impurities is 1 ppm by mass or less. This total content is preferably 0.5 ppm by mass or less. Moreover, the method for measuring the total content of metal impurities is performed according to the examples described later. Furthermore, the sulfonic acid-modified colloidal silicon oxide described above is preferable because it does not contain corrosive halogen elements such as chlorine and bromine. The particle size of the sulfonic acid-modified colloidal silicon oxide of this invention is not particularly limited, for example, below 1000 nm, preferably between 5 nm and 500 nm, and more preferably between 10 nm and 300 nm. Furthermore, the particle size of the sulfonic acid-modified colloidal silicon oxide refers to the volume average particle size based on the Heywood diameter (equivalent circle diameter). The sulfonic acid-modified colloidal silica of this invention exhibits excellent stability over a wide pH range. In particular, the sulfonic acid-modified colloidal silica of this invention exhibits high stability in acidic regions. When obtaining modified colloidal silica with anionic groups, since anionic groups are used as coupling agents in the modifier, the zeta potential is negative when the dispersion medium is acidic (pH 2 or higher), thus maintaining high dispersion stability even in acidic media. The sulfonic acid-modified colloidal silica of this invention also exhibits high dispersion stability, and consequently, its kinematic viscosity is also relatively low. [use] The sulfonic acid-modified colloidal silica of this invention can be used in various applications such as abrasives (grind particles) in grinding compositions and paper coatings. It disperses stably over a wide pH range, especially under acidic conditions. Furthermore, the sulfonic acid-modified colloidal silica becomes less likely to adhere to the surface of the object being ground, improving its cleanliness after grinding and further reducing residue on the surface of the object. Furthermore, as described above, the sulfonic acid-modified colloidal silicon oxide of the present invention, which has reduced the proportion of tiny particles adhering to the wafer, is particularly suitable for use as an abrasive (grinding particle) for CMP polishing of semiconductor wafers. Since it minimizes the time-dependent variation of polishing rate (excellent time-dependent stability), it can also fully meet the high performance requirements associated with miniaturization. Therefore, according to one aspect of the present invention, a grinding composition is provided, which comprises the sulfonic acid modified colloidal silicon oxide of the present invention. In addition to the sulfonic acid-modified colloidal silica of this invention, the grinding composition of this invention may also contain a dispersion medium, a pH adjuster, an ammonium salt as a grinding speed enhancer, abrasive particles other than the sulfonic acid-modified colloidal silica of this invention, a chelating agent, a thickener, an oxidizing agent, a dispersant, a surface protectant, a wetting agent, a surfactant, a corrosion inhibitor (rust inhibitor), a mildew inhibitor (preservative), a water-soluble polymer, and other known components. The content of these other components can be appropriately set according to their intended purpose. The concentration (content) of sulfonic acid-modified colloidal silica, which serves as abrasive grains, in the grinding composition of the present invention is not particularly limited. When the grinding composition (typically a slurry-like grinding fluid, also referred to as a working slurry or grinding paste) is used directly as a grinding fluid for grinding the workpiece, the concentration (content) of sulfonic acid-modified colloidal silica relative to the total mass of the grinding composition is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably exceeding 1% by mass, particularly preferably 2% by mass or more, and most preferably 3% by mass or more. As the concentration of sulfonic acid-modified colloidal silica increases, the grinding speed of the workpiece is further improved. Furthermore, relative to the total mass of the grinding components, the concentration (content) of sulfonic acid-modified colloidal silicon dioxide is preferably 20% by mass or less, preferably 15% by mass or less, even better 10% by mass or less, and particularly preferably 5% by mass or less. Within the above ranges, the generation of defects such as residues originating from sulfonic acid-modified colloidal silicon dioxide will be further reduced. According to a preferred embodiment, relative to the total mass of the grinding components, the concentration (content) of sulfonic acid-modified colloidal silicon dioxide is preferably 0.5% by mass to 20% by mass, more preferably 1% by mass to 15% by mass, even more preferably more than 1% by mass and less than 10% by mass, particularly preferably 2% by mass to 10% by mass, and best preferably 3% by mass to 5% by mass. When the concentration (content) of sulfonic acid-modified colloidal silicon dioxide is within the above range, not only can the grinding speed of the object being ground be further improved, but also the residue on the surface of the object being ground can be reduced. Furthermore, when the grinding composition (i.e., concentrated solution) is used after dilution, the content of sulfonic acid-modified colloidal silica is generally appropriate to be 25% by mass or less, and preferably 20% by mass or less, relative to the total mass of the grinding composition, from the viewpoint of storage stability and filterability. Moreover, from the viewpoint of maximizing the advantages of using it to form a concentrated solution, the content of sulfonic acid-modified colloidal silica is preferably 3% by mass or more, and more preferably 5% by mass or more, relative to the total mass of the grinding composition. The embodiments of the present invention have been described in detail, but this is merely illustrative and exemplary and not intended to be limiting. The scope of the present invention should obviously be interpreted by the appended claims. The present invention includes the following forms and shapes. 1. A sulfonic acid-modified colloidal silicon oxide, wherein the amount of sulfonic acid groups per 1g of particles is more than 1.5μmol / g and less than 13.0μmol / g. 2. The sulfonic acid modified colloidal silicon oxide as described in 1 above, wherein the amount of the aforementioned sulfonic acid group is 3.0 μmol / g or more and 10.5 μmol / g or less. 3. A method for manufacturing sulfonic acid-modified colloidal silicon oxide, comprising: An organic solvent removal step is performed by distilling off the organic solvent coexisting with the colloidal silica, where the residual organic solvent concentration in the colloidal silica is less than 1% by mass, under conditions of pH 7 or higher, to obtain the raw material colloidal silica. The modification step involves subjecting the aforementioned raw material, colloidal silicon oxide, to sulfonic acid modification to obtain sulfonic acid-modified colloidal silicon oxide; wherein... The aforementioned modification steps include: a first reaction step of heating the aforementioned raw material colloidal silica in the presence of a silane coupling agent having a functional group that can be chemically converted into a sulfonic acid group to obtain a reactant; and a second reaction step of treating the aforementioned reactant to convert the aforementioned functional group into a sulfonic acid group. In the first reaction step mentioned above, relative to 100% by mass of the silica particles contained in the aforementioned raw material colloidal silica, the amount of the aforementioned silane coupling agent added is 0.1% by mass or more but less than 1.25% by mass. 4. The manufacturing method described in 3. above, wherein the amount of the aforementioned silane coupling agent added is more than 0.25% by mass and less than 1.0% by mass. 5. A grinding composition comprising sulfonic acid-modified colloidal silicon oxide as described in 1. or 2. above. [Example] The present invention will be further described in detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. Furthermore, unless otherwise specified, "%" and "parts" refer to "mass %" and "parts by mass," respectively. Also, in the following examples, unless otherwise specified, the operation is carried out at room temperature (20~25°C) / relative humidity 40~50%RH. (Example 1) Synthesis of silica sol In a flask, 4842 g of methanol (manufactured by Kanto Chemical Co., Ltd.), 750 g of water, and 178 g of 29% ammonia solution (manufactured by Kanto Chemical Co., Ltd.) were mixed. The liquid temperature was maintained at 20°C. A mixture of 135 g of methanol (manufactured by Kanto Chemical Co., Ltd.) and 508 g of tetramethoxysilane (manufactured by Tama Chemical Industry Co., Ltd.) was added dropwise over a time of 36 minutes. Subsequently, the mixture was thermally concentrated and water was replaced to obtain 1000 g of silica sol with a silica particle concentration of 19.5% by mass. When the methanol concentration in this silica sol was measured using gas chromatography, it was confirmed to be less than 1% by mass (below the detection limit). Measurement of methanol concentration using gas chromatography Apparatus: Gas Chromatography GC-14B Measurement: Using a 10 μL syringe, draw 4 μL of the sample and inject it into the above apparatus. Calculate the methanol concentration from the measured water and methanol content. Synthesis of Sulfonic Acid-Modified Colloidal Silicon Oxide For the 1000g of silica sol obtained above, 0.25g of 3-mercaptopropyltrimethoxysilane (product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) mixed with 4.75g of methanol was added dropwise at a flow rate of 1mL / min. The mixture was then heated to boiling and then replaced with water for 3 hours. After the reaction solution was cooled to 25°C, 0.44g of 30% hydrogen peroxide water (manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.) was added and the mixture was brought to a boil again. After boiling, the mixture was allowed to undergo water substitution for 2 hours and then cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silicon oxide (anion-modified colloidal silicon oxide). (Example 2) For 1000g of silica sol synthesized using the same method as in Example 1 (Synthesis of Silica Sol), 0.50g of 3-mercaptopropyltrimethoxysilane (product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) mixed with 9.50g of methanol was added dropwise at a flow rate of 1mL / min. The mixture was then heated and boiled for 3 hours before water substitution. Next, the reaction solution was cooled to 25°C, and then 0.88g of 30% hydrogen peroxide water (manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.) was added and brought to a boil again. After boiling, water was replaced for 2 hours, and then the solution was cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silicon dioxide. (Example 3) For 1000g of silica sol synthesized using the same method as in Example 1 (Synthesis of silica sol), 0.80g of 3-mercaptopropyltrimethoxysilane (product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) mixed with 15.2g of methanol was added dropwise at a flow rate of 1mL / min. The mixture was then heated and boiled for 3 hours before water substitution. Next, the reaction solution was cooled to 25°C, and then 1.40g of 30% hydrogen peroxide water (manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.) was added and brought to a boil again. After boiling, the solution was allowed to undergo water replacement for 2 hours, and then cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silicon dioxide. (Example 4) For 1000g of silica sol synthesized using the same method as in Example 1 (Synthesis of silica sol), 1.00g of 3-mercaptopropyltrimethoxysilane (product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) mixed with 19.0g of methanol was added dropwise at a flow rate of 1mL / min. The mixture was then heated and boiled for 3 hours with water substitution. Next, the reaction solution was cooled to 25°C, and then 1.75g ​​of 30% hydrogen peroxide water (manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.) was added and brought to a boil again. After boiling, the solution was allowed to undergo water substitution for 2 hours, and then cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silicon dioxide. (Example 5) For 1000g of silica sol synthesized using the same method as in Example 1 (Synthesis of silica sol), 1.5g of 3-mercaptopropyltrimethoxysilane (product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) mixed with 28.5g of methanol was added dropwise at a flow rate of 1mL / min. The mixture was then heated and boiled for 3 hours with water substitution. Next, the reaction solution was cooled to 25°C, and then 2.63g of 30% hydrogen peroxide water (manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.) was added and brought to a boil again. After boiling, the solution was allowed to undergo water replacement for 2 hours, and then cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silicon dioxide. (Example 6) For 1000g of silica sol synthesized using the same method as in Example 1 (Synthesis of silica sol), 2.0g of 3-mercaptopropyltrimethoxysilane (product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) mixed with 38.0g of methanol was added dropwise at a flow rate of 1mL / min. The mixture was then heated and boiled for 3 hours with water substitution. Next, the reaction solution was cooled to 25°C, and then 3.50g of 30% hydrogen peroxide water (manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.) was added and brought to a boil again. After boiling, water was replaced for 2 hours, and then the solution was cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silicon dioxide. (Comparative Example 1) In a flask, 4080 g of methanol (manufactured by Kanto Chemical Co., Ltd.), 610 g of water, and 168 g of 29% ammonia solution (manufactured by Kanto Chemical Co., Ltd.) were mixed. The liquid temperature was maintained at 20°C. A mixture of 135 g of methanol and 508 g of tetramethoxysilane (TMOS) (manufactured by Tama Chemical Industry Co., Ltd.) was added dropwise over a time of 25 minutes. Subsequently, the mixture was thermally concentrated with water replacement at a pH above 7 to obtain 1000 g of silica sol with a silica particle concentration of 19.5% by mass. When the methanol concentration in this silica sol was measured using the gas chromatography method described above, it was confirmed to be less than 1% by mass (below the detection limit). For 1000g of the obtained silica sol, 22.5g of methanol and 2.5g of 3-mercaptopropyltrimethoxysilane (product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) were added dropwise at a flow rate of 1mL / min. The mixture was then heated and boiled for 3 hours before water replacement. Next, the reaction solution was cooled to 25°C, and then 4.3g of 30% hydrogen peroxide water (manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.) was added and brought to a boil again. After boiling, water was replaced for 2 hours, and then the solution was cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silicon dioxide. (Comparative Example 2) For 1000g of silica sol synthesized using the same method as in Example 1 (Synthesis of Silica Sol), 0.1g of 3-mercaptopropyltrimethoxysilane (product name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd.) mixed with 1.9g of methanol (manufactured by Kanto Chemical Co., Ltd.) was added dropwise at a flow rate of 1mL / min. The mixture was then heated and boiled for 3 hours before water substitution. Next, the reaction solution was cooled to 25°C, and then 0.175g of 30% hydrogen peroxide water (manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.) was added and brought to a boil again. After boiling, water was replaced for 2 hours, and then the solution was cooled to room temperature (25°C) to obtain sulfonic acid-modified colloidal silicon dioxide. <Measurement of Sulfonic Acid Content> In silicon oxide particles with immobilized sulfonic acid groups on their surface, the amount of sulfonic acid groups on the surface, taking into account that 1 mol of monovalent potassium ions (K+) will react with 1 mol of monovalent organic acid (sulfonic acid), can be calculated using the following formula. The amount of sulfonic acid groups per 1g of silicon oxide particles (as a solid component) (unit: μmol / g) can be calculated based on the following formula: In the above formula, nS represents the amount of sulfonic acid groups per 1g of surface-treated silicon oxide particles (as a solid component) [unit: μmol / g]; K represents the analytical value of potassium in solids [unit: ppm by mass]; Aw represents the atomic weight of potassium [unit: g / mol]: Specifically, firstly, 21.0 g of a 0.01 mol / L hydrochloric acid-0.01 mol / L potassium chloride mixture was added to 21.0 g of a 19.5% by mass aqueous solution of silicon oxide. After thorough mixing, the resulting mixture was centrifuged according to the following procedure: Procedure: A special resin tube was placed in the above mixture (silica sol) and centrifuged at 26,000 rpm (26,000 min⁻¹) for 2 hours. The precipitate was washed with ultrapure water and ion-exchanged water. The precipitate was then evaporated, dried, and solidified to form a sample. A Beckman Coulter Avanti HP-30I high-performance, high-speed cooled centrifuge was used as the centrifugal separation device. Next, the potassium content (K in the above formula) in the obtained sample was measured using an inductively coupled plasma (ICP) luminescence analyzer according to the following procedure: Procedure: Add 6 mL of nitric acid and 15 mL of hydrofluoric acid to 4 g of the sample obtained by centrifugation as described above, and allow it to evaporate and solidify. After drying and solidification, add 0.5 mL of nitric acid and approximately 20 mL of ultrapure water, and heat until steam is generated. The total amount of the recovered mixture is divided into 50 g with ultrapure water, and then 3.0 g of this mixture is taken and diluted with ultrapure water to make 30 g. The mixture is then measured using an ICP luminescence analyzer (manufactured by Shimadzu Corporation, model: ICPS-8100). [evaluate] (Cleanliness evaluation) The adhesion of the sulfonic acid-modified colloidal silicon oxide obtained in the above examples and comparative examples to silicon nitride (SiN) wafers was observed: Apparatus: SU8000 scanning electron microscope (manufactured by Hitachi High Technology Co., Ltd.) SiN wafers: manufactured by Advantech Inc. Procedure: The obtained sulfonic acid-modified colloidal silicon oxide was diluted with pure water to a silicon oxide concentration of 14% by mass. A pH 3 dispersion was prepared using a pH adjuster. SiN wafers were immersed in this dispersion for 30 seconds, followed by a shake in pure water for 10 seconds. Afterward, the wafers were completely dried with N₂ gas and observed in 10 fields of view at 50,000x magnification using a scanning electron microscope (SU8000). Evaluation: Using SEM to observe the dried SiN wafer, the proportion of the area with attached particles was determined by setting the full area of ​​10 fields of view (50,000x magnification) to 100%. The evaluation was based on the following criteria. A to C indicates a practically usable wafer. A: Below 10% (excellent cleaning power) B: More than 10% but less than 30% (good cleaning power) C: More than 30% but less than 50% (no major issues with cleanliness) D: More than 50% (poor cleaning performance). (Stability test) Take 100g each of the sulfonic acid-modified colloidal silicon oxide prepared in the above examples and comparative examples, and adjust the pH to 2 and 3 respectively using 0.1mol / L HCl aqueous solution and 0.1mol / L NaOH aqueous solution as pH adjusters. After sealing, store in an air bath at 80°C for 24 hours. After 24 hours, remove the liquid from the air bath and confirm that the liquid temperature has reached room temperature (25°C). Visually inspect for any sedimentation or gelation. Regarding individual samples, samples that show no change before storage at 80°C are judged as good (A), samples that show some sedimentation are judged as slightly poor (B), and samples that show violent sedimentation or change into gel are judged as poor (C). The sulfonic acid content and evaluation results of the sulfonic acid modified colloidal silicon oxide in the examples and comparative examples are shown in Table 1 below. The results in Table 1 clearly show that the sulfonic acid-modified colloidal silicon dioxide of Examples 1-6 of the present invention exhibits excellent stability and detergency under acidic conditions. On the other hand, it was found that the detergency of the sulfonic acid-modified colloidal silicon dioxide of Comparative Example 1, with a sulfonic acid group content exceeding 13.0 μmol / g, decreased. Furthermore, the stability of the sulfonic acid-modified colloidal silicon dioxide of Comparative Example 2, with a sulfonic acid group content less than 1.5 μmol / g, decreased under acidic conditions. This application is incorporated herein by reference in its entirety from Japanese Patent Application No. 2022-053011, filed on March 29, 2022.

Claims

1. A sulfonic acid-modified colloidal silicon oxide, wherein the sulfonic acid content per 1g of particles is 1.5μmol / g or more and 13.0μmol / g or less, the number distribution ratio of microparticles is less than 10%, and the microparticles have a particle size of less than 40% of the volume average particle size based on the Heywood diameter (equivalent circular diameter).

2. The sulfonic acid modified colloidal silicon oxide as claimed in claim 1, wherein the amount of the aforementioned sulfonic acid group is more than 3.0 μmol / g and less than 10.5 μmol / g.

3. A method for manufacturing sulfonic acid-modified colloidal silicon oxide, comprising: an organic solvent removal step of distilling off the organic solvent coexisting with the colloidal silicon oxide under conditions of pH 7 or above, wherein the residual organic solvent concentration in the colloidal silicon oxide with an organic solvent concentration of 1% by mass or more is less than 1% by mass; and a modification step of subjecting the aforementioned raw material colloidal silicon oxide to sulfonic acid modification to obtain sulfonic acid-modified colloidal silicon oxide; wherein the aforementioned modification step comprises: a first reaction step of heating the aforementioned raw material colloidal silicon oxide in the presence of a silane coupling agent having a functional group capable of chemically converting to a sulfonic acid group to obtain a reactant; and a second reaction step of processing the aforementioned reactant to convert the aforementioned functional group to a sulfonic acid group. In the first reaction step mentioned above, relative to 100% by mass of the silica particles contained in the aforementioned raw material colloidal silica, the amount of the aforementioned silane coupling agent added is 0.1% by mass or more but less than 1.25% by mass.

4. The manufacturing method of claim 3, wherein the amount of the aforementioned silane coupling agent added is more than 0.25% by mass and less than 1.0% by mass.

5. A grinding composition comprising sulfonic acid modified colloidal silicon oxide as claimed in claim 1.