Sulfonic acid-modified colloidal silica and method for producing same

Abstract

The present invention provides a sulfonic acid-modified colloidal silica which has excellent long-term stability of metal adsorption amount and is capable of suppressing the amount of residual abrasive grains on a polished metal surface after polishing and cleaning.　This sulfonic acid-modified colloidal silica contains silica particles, and is characterized in that: (1) the surfaces of the silica particles are modified with a sulfonic acid group; (2) the Cu ion adsorption amount of the silica particles is 5.00-110.00 µmol / g; (3) the ratio (Cu ion adsorption amount (µmol / g) / S content (µmol / g)) of the Cu ion adsorption amount to the S content of the silica particles is 0.50 or more; and (4) the rate of change over time of the Cu ion adsorption amount of the silica particles is 1.30 or less as measured by the measurement method described below. [Measurement method of the rate of change over time of the Cu ion adsorption amount of the silica particles] The sulfonic acid-modified colloidal silica is left to stand at 25°C for 3 months. The Cu ion adsorption amount (µmol / g) of the silica particles before standing and the Cu ion adsorption amount (µmol / g) of the silica particles after standing are measured and the rate of change over time of the Cu ion adsorption amount of the silica particles is calculated by the following formula. (Rate of change over time of Cu ion adsorption amount of silica particles) = (Cu ion adsorption amount (µmol / g) of silica particles after standing) / (Cu ion adsorption amount (µmol / g) of silica particles before standing)

Description

Sulfonic acid-modified colloidal silica and its manufacturing method

[0001] The present invention relates to sulfonic acid-modified colloidal silica and a method for producing the same.

[0002] Colloidal silica is silica particles dispersed in a medium such as water, and is used as a property improver in the fields of paper, textiles, steel, etc., as well as an abrasive used in the polishing (CMP) of semiconductor devices such as semiconductor wafers.

[0003] In the manufacturing process of semiconductor devices, a polishing process is performed to polish metal materials such as wiring materials and barrier metal materials to form wiring structures. In this polishing process, it is required to polish and remove the metal materials at a high speed in order to improve the productivity of semiconductor devices.

[0004] In order to polish and remove metal materials at high speeds, sulfonic acid-modified colloidal silica, which has sulfo groups on its surface that chemically react with and adsorb metals, is used as a polishing abrasive.

[0005] Against this background, various inventions relating to sulfonic acid-modified colloidal silica have been filed for patent application. For example, Patent Document 1 discloses sulfonic acid-modified colloidal silica, and that the sulfonic acid-modified colloidal silica can be suitably used for polishing semiconductors.

[0006] Furthermore, Patent Document 2 discloses that a high metal film polishing rate can be achieved while suppressing corrosion of the metal film by using a polishing slurry that contains, as abrasive grains, silica particles having functional groups (sulfo groups) on the surface that are reactive to metal films and that does not substantially contain an etching agent.

[0007] JP 2023-146033 A JP 2020-115501 A

[0008] As a result of extensive research, the present inventors have found that conventional sulfonic acid-modified colloidal silica has the following problem: when sulfonic acid-modified colloidal silica is stored for a long period of time, the amount of metal adsorbed changes over time, and as a result, when used as abrasive grains for polishing metal materials, the polishing removal rate of the metal changes over time.

[0009] Furthermore, when sulfonic acid-modified colloidal silica is used as abrasive grains for polishing metal materials, there is a problem in that a large amount of silica abrasive grains remain on the polished metal surface after polishing and cleaning because the sulfonic acid-modified colloidal silica has an excessively high adsorption ability to metals.

[0010] For example, Patent Documents 1 and 2 do not discuss the stability of the metal adsorption amount over time for sulfonic acid-modified colloidal silica. Furthermore, the inventors have confirmed that the metal adsorption amount of sulfonic acid-modified colloidal silica produced by the method described in these documents changes over time, which causes a problem that when used as an abrasive for metal polishing, the metal polishing removal rate changes over time.

[0011] In view of the above circumstances, an object of the present invention is to provide a sulfonic acid-modified colloidal silica that has excellent stability over time in the amount of metal adsorption and can suppress the amount of abrasive grains remaining on the polished metal surface after polishing and cleaning.

[0012] As a result of extensive research into achieving the above-mentioned object, the present inventors have found that the above-mentioned object can be achieved by a sulfonic acid-modified colloidal silica containing silica particles whose surfaces are modified with sulfonic acid groups, in which the Cu ion adsorption amount of the silica particles and the ratio of the Cu ion adsorption amount of the silica particles to the S content are within specific ranges, and in which the rate of change over time in the Cu ion adsorption amount of the silica particles, as measured by a specific measurement method, is within a specific range, thereby completing the present invention.

[0013] That is, the present invention relates to the following sulfonic acid-modified colloidal silica and a method for producing the same: 1. Sulfonic acid-modified colloidal silica containing silica particles, characterized in that: (1) the surfaces of the silica particles are modified with sulfonic acid groups, (2) the Cu ion adsorption amount of the silica particles is 5.00 to 110.00 μmol / g, (3) the ratio of the Cu ion adsorption amount to the S content of the silica particles (Cu ion adsorption amount (μmol / g) / S content (μmol / g)) is 0.50 or more, and (4) the rate of change with time in the Cu ion adsorption amount of the silica particles, as measured by the following measurement method, is 1.30 or less. [Method for measuring the rate of change with time in the Cu ion adsorption amount of silica particles] The sulfonic acid-modified colloidal silica is allowed to stand at 25°C for 3 months. The Cu ion adsorption amount (μmol / g) of the silica particles before and after standing is measured, and the rate of change over time of the Cu ion adsorption amount of the silica particles is calculated using the following formula: (rate of change over time of Cu ion adsorption amount of silica particles) = Cu ion adsorption amount after standing (μmol / g) / Cu ion adsorption amount before standing (μmol / g) 2. The sulfonic acid-modified colloidal silica according to item 1, wherein the Cu ion adsorption amount of the silica particles is 8.00 to 105.00 μmol / g. 3. The sulfonic acid-modified colloidal silica according to item 1 or 2, wherein the S content of the silica particles is 10.00 to 200.00 μmol / g. 4. The sulfonic acid-modified colloidal silica according to any one of items 1 to 3, wherein the ratio of the Cu ion adsorption amount to the S content is 0.55 or more. 5. Item 5. The sulfonic acid-modified colloidal silica according to any one of Items 1 to 4, wherein the hydrogen peroxide concentration is 1000 ppm or less.6. A method for producing sulfonic acid-modified colloidal silica, comprising: (I) step I of adding a silane coupling agent having a mercapto group to colloidal silica to perform a modification treatment; (II) step II of adding hydrogen peroxide to the modified colloidal silica to oxidize the mercapto groups on the silica particle surface and convert them to sulfo groups; and (III) step III of heating the colloidal silica to which the hydrogen peroxide has been added at a temperature of 80°C or higher for 15 hours or longer, wherein the amount of the silane coupling agent having a mercapto group added is 25.00 to 400.00 μmol / g per 1 g of silica particles, and the amount of the hydrogen peroxide added is 3.30 mol / mol or more per 1 mol of the silane coupling agent having a mercapto group added. Item 7. The method according to Item 6, wherein the silane coupling agent having a mercapto group is at least one selected from the group consisting of 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane.

[0014] The sulfonic acid-modified colloidal silica of the present invention has excellent stability over time in the amount of metal adsorption, and the change over time in the metal polishing removal rate is suppressed. Furthermore, the sulfonic acid-modified colloidal silica of the present invention exhibits a high metal polishing removal rate, and the amount of abrasive grains remaining on the polished metal surface after polishing and cleaning is suppressed. Furthermore, the production method of the present invention can produce the sulfonic acid-modified colloidal silica of the present invention.

[0015] The present invention will be described in detail below. Note that the following description of the components may be based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

[0016] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example. Furthermore, in this specification, a numerical value connected with "to" means a numerical range that includes the numbers before and after "to" as the upper and lower limits.

[0017] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "include," "consist essentially of," and "consist only of."

[0018] The sulfonic acid-modified colloidal silica of the present invention is a sulfonic acid-modified colloidal silica containing silica particles, characterized in that: (1) the surfaces of the silica particles are modified with sulfonic acid groups; (2) the Cu ion adsorption amount of the silica particles is 5.00 to 110.00 μmol / g; (3) the ratio of the Cu ion adsorption amount to the S content of the silica particles (Cu ion adsorption amount (μmol / g) / S content (μmol / g)) is 0.50 or more; and (4) the rate of change with time in the Cu ion adsorption amount of the silica particles, as measured by a specific measurement method, is 1.30 or less.

[0019] The sulfonic acid-modified colloidal silica of the present invention has (1) silica particles whose surfaces are modified with sulfonic acid groups and has the following configurations (2) to (4), and therefore its metal adsorption capacity is controlled within an appropriate range for abrasive grains for metal polishing, and the metal adsorption amount is highly stable over time.The sulfonic acid-modified colloidal silica of the present invention has suppressed changes over time in the metal polishing removal rate, and the amount of abrasive grains remaining on the polished metal surface after polishing and cleaning is extremely small, making it extremely suitable for use as abrasive grains for metal polishing.

[0020] The production method of the present invention includes the steps of (I) adding a silane coupling agent having a mercapto group to colloidal silica to modify it, (II) adding hydrogen peroxide to the modified colloidal silica to oxidize the mercapto groups on the silica particle surface and convert them to sulfo groups, and (III) heating the colloidal silica to which hydrogen peroxide has been added at a temperature of 80° C. or higher for 15 hours or longer, wherein the amounts of the silane coupling agent having a mercapto group and the hydrogen peroxide added are within specific ranges. According to this production method of the present invention, the amount of the modifier used to sulfonate the surface of the starting colloidal silica is optimized, and by heat-treating the colloidal silica under appropriate conditions after adding the modifier, it is possible to produce sulfonic acid-modified colloidal silica whose metal adsorption capacity is controlled within an appropriate range for metal polishing abrasive grains and whose metal adsorption capacity is highly stable over time.

[0021] The colloidal silica of the present invention and its production method will be described in detail below.

[0022] 1. Sulfonic Acid-Modified Colloidal Silica The sulfonic acid-modified colloidal silica of the present invention (hereinafter also simply referred to as "colloidal silica") is a sulfonic acid-modified colloidal silica containing silica particles, in which (1) the surfaces of the silica particles are modified with sulfonic acid groups, (2) the Cu ion adsorption amount of the silica particles is 5.00 to 110.00 μmol / g, (3) the ratio of the Cu ion adsorption amount to the S content of the silica particles (Cu ion adsorption amount (μmol / g) / S content (μmol / g)) is 0.50 or more, and (4) the rate of change with time in the Cu ion adsorption amount of the silica particles, as measured by a specific measurement method, is 1.30 or less.

[0023] The colloidal silica of the present invention contains silica particles whose surfaces are modified with sulfonic acid groups. In this specification, "surfaces of silica particles modified with sulfonic acid groups" means that sulfonic acid groups have been introduced onto the surfaces of the silica particles by sulfonic acid modification.

[0024] The fact that the surface of colloidal silica is modified with sulfonic acid groups can be confirmed by the method for confirming the presence or absence of sulfo groups on the particle surface by X-ray photoelectron spectroscopy (XPS) in the examples described below.

[0025] The Cu ion adsorption amount of the silica particles contained in the colloidal silica of the present invention is 5.00 to 110.00 μmol / g. If the Cu ion adsorption amount is less than 5.00 μmol / g, the metal polishing removal rate will be low. On the other hand, if the Cu ion adsorption amount exceeds 110.00 μmol / g, the adsorption ability to the metal to be polished will be excessively high, and the amount of abrasive grains remaining on the polished metal surface after polishing and cleaning will increase. The Cu ion adsorption amount is preferably 8.00 to 105.00 μmol / g, and more preferably 8.20 to 103.00 μmol / g.

[0026] In this specification, the amount of Cu ions adsorbed on the silica particles is measured by the measurement method described in the examples below.

[0027] The silica particles contained in the colloidal silica of the present invention preferably have an S content of 10.00 to 200.00 μmol / g, more preferably 12.00 to 190.00 μmol / g, even more preferably 13.00 to 185.00 μmol / g, and particularly preferably 14.00 to 180.00 μmol / g. By having the lower limit of the S content within the above range, the polishing removal rate of metal is further improved. Furthermore, by having the upper limit of the S content within the above range, adsorption to the metal to be polished is appropriately suppressed, and the amount of abrasive grains remaining on the polished metal surface after polishing and cleaning is reduced.

[0028] In this specification, the S content of the silica particles is measured by the measurement method described in the examples below.

[0029] The colloidal silica of the present invention has a ratio of Cu ion adsorption amount to S content (Cu ion adsorption amount (μmol / g) / S content (μmol / g)) of 0.50 or more in silica particles. If the ratio of Cu ion adsorption amount to S content is less than 0.50, the change over time of the metal adsorption amount becomes large, and the change over time of the metal polishing removal rate during storage of the slurry becomes large. The ratio of Cu ion adsorption amount to S content is preferably 0.53 or more, more preferably 0.55 or more. There is no particular upper limit for the ratio of Cu ion adsorption amount to S content, and it is preferably 1.30 or less, more preferably 1.10 or less.

[0030] In this specification, the ratio of the Cu ion adsorption amount to the S content (Cu ion adsorption amount / S content) is measured by the measurement method described in the examples below.

[0031] The colloidal silica of the present invention has a rate of change over time of the Cu ion adsorption amount of the silica particles of 1.30 or less. If the rate of change over time is less than 1.30, the rate of change over time of the metal polishing removal rate will change significantly. The rate of change over time is preferably 1.20 or less, more preferably 1.15 or less. The lower limit of the rate of change over time is not particularly limited, and may be 0.90, 0.95, 1.00, or 1.02.

[0032] In this specification, the rate of change over time in the amount of Cu ions adsorbed on the silica particles is measured by the measurement method described in the examples below.

[0033] The colloidal silica of the present invention may contain hydrogen peroxide.

[0034] The hydrogen peroxide concentration of the colloidal silica of the present invention is preferably 1000 ppm or less, more preferably 900 ppm or less, even more preferably 800 ppm or less, and particularly preferably 700 ppm or less. The hydrogen peroxide concentration is preferably 10 ppm or more, more preferably 20 ppm or more, and even more preferably 30 ppm or more. By setting the lower limit of the hydrogen peroxide concentration within the above range, the polishing removal rate of metal is further improved. By setting the upper limit of the hydrogen peroxide concentration within the above range, corrosion and excessive etching of the metal to be polished are suppressed, and the risk of expansion and rupture of the filling container due to gas generated by self-decomposition of hydrogen peroxide is reduced.

[0035] In this specification, the hydrogen peroxide concentration of the colloidal silica is measured by the measurement method described in the Examples section below.

[0036] The colloidal silica of the present invention contains silica particles. The content of silica particles in the colloidal silica is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, based on 100% by mass of the colloidal silica. The content of silica in the colloidal silica is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on 100% by mass of the colloidal silica. When the lower limit of the content of silica particles in the colloidal silica is within the above range, the polishing performance when the colloidal silica is used as an abrasive is further improved. When the upper limit of the content of silica particles in the colloidal silica is within the above range, the dispersion stability of the silica particles is further improved.

[0037] In this specification, the content of silica particles in colloidal silica can be calculated by the following formula, where 10.0 g of colloidal silica is dried on a hot plate at 150°C, and then heated at 800°C for 1 hour to remove moisture, and the amount of solids obtained is defined as Wg: Content of silica particles in colloidal silica [%] = (W ÷ 10.0) × 100

[0038] The average primary particle diameter of the silica particles contained in the colloidal silica of the present invention is preferably 100 nm or less, more preferably 80 nm or less, and even more preferably 50 nm or less. When the upper limit of the average primary particle diameter is within the above range, the flatness when polished using the colloidal silica of the present invention is further improved. Furthermore, the average primary particle diameter of the silica particles is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. When the lower limit of the average primary particle diameter of the silica particles is within the above range, the storage stability of the colloidal silica is further improved. The average primary particle diameter of the silica particles is measured by the following measurement method.

[0039] (Method for measuring average primary particle diameter) Colloidal silica is pre-dried on a hot plate and then heat-treated at 800°C for 1 hour to prepare a measurement sample. The BET specific surface area is measured using the prepared measurement sample. Assuming that the true specific gravity of silica is 2.2, the BET specific surface area is calculated as 2727 / BET specific surface area (m ２ / g) is converted to the average primary particle diameter (nm) of silica particles in the colloidal silica.

[0040] The average secondary particle diameter of the silica particles contained in the colloidal silica of the present invention is preferably 200 nm or less, more preferably 150 nm or less, even more preferably 110 nm or less, and particularly preferably 80 nm or less. When the upper limit of the average secondary particle diameter is within the above range, flatness is further improved when polishing is performed using the colloidal silica of the present invention. The lower limit of the average secondary particle diameter is not particularly limited, and is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, and particularly preferably 20 nm or more. When the lower limit of the average secondary particle diameter is within the above range, polishing performance is further improved when the colloidal silica is used as an abrasive. The average secondary particle diameter of the silica particles is measured by the following measurement method.

[0041] (Method for measuring average secondary particle diameter) A sample for measuring the average secondary particle diameter is prepared by adding colloidal silica to a 0.3% by mass aqueous citric acid solution and homogenizing it to a silica concentration of 0.8% by mass. Using this measurement sample, the average secondary particle diameter (nm) is measured by dynamic light scattering ("ELSZ-2000S" manufactured by Otsuka Electronics Co., Ltd.).

[0042] The pH of the colloidal silica of the present invention may be appropriately set depending on the application of the colloidal silica, and is not particularly limited, but is preferably 2.0 or higher, more preferably 3.0 or higher. The pH is preferably 11.0 or lower, more preferably 10.0 or lower. When the lower limit of the pH is within the above range, the long-term dispersion stability of the silica particles in the colloidal silica is further improved. When the upper limit of the pH is within the above range, the long-term dispersion stability of the colloidal silica is further improved.

[0043] The colloidal silica of the present invention preferably has a content of metal impurities such as sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt of 1 ppm or less. By having a content of metal impurities of 1 ppm or less, the colloidal silica can be suitably used for polishing electronic materials and the like.

[0044] The colloidal silica of the present invention can be used as an abrasive (CMP) for semiconductor devices such as semiconductor wafers. It can also be used as a property improver in the fields of paper, textiles, steel, etc., and can also be used as a filler additive, a toner external additive, etc. by drying it into a powder.

[0045] 2. Method for Producing Colloidal Silica The method for producing colloidal silica of the present invention comprises: (I) Step I of adding a silane coupling agent having a mercapto group to colloidal silica to modify it; (II) Step II of adding hydrogen peroxide to the modified colloidal silica to oxidize the mercapto groups on the silica particle surface and convert them to sulfo groups; and (III) Step III of heating the colloidal silica to which hydrogen peroxide has been added at a temperature of 80°C or higher for 15 hours or longer, wherein the amount of the silane coupling agent having a mercapto group added is 25.00 to 400.00 μmol / g per 1 g of silica particles, and the amount of the hydrogen peroxide added is 3.30 mol / mol or more per 1 mol of the silane coupling agent having a mercapto group added. The production method of the present invention, as described above, can suitably produce the sulfonic acid-modified colloidal silica of the present invention.

[0046] Each step of the production method of the present invention will be described in detail below.

[0047] (Step I) Step I is a step of adding a silane coupling agent having a mercapto group to colloidal silica to modify it.

[0048] In the above step I, the temperature of the colloidal silica is not particularly limited, but is preferably 5 to 100°C, and more preferably 20 to 80°C. When the lower limit of the temperature of the colloidal silica is within the above range, aggregation of silica particles during modification with sulfonic acid groups is further suppressed. When the upper limit of the temperature of the colloidal silica is within the above range, evaporation of the solvent is further suppressed.

[0049] In the production method of the present invention, colloidal silica is modified by adding a silane coupling agent having a mercapto group. That is, the modification treatment in step I is a modification treatment that converts the functional groups of the silica particles into sulfonic acid groups.

[0050] The colloidal silica raw material is not limited as long as it has silanol groups on its surface, but considering that it does not contain metal impurities that are diffusible in semiconductors or corrosive ions such as chlorine, colloidal silica obtained by hydrolysis and condensation of a hydrolyzable silicon compound (e.g., alkoxysilane or its derivative) is preferred. This silicon compound can be used alone or in combination of two or more.

[0051] In the present invention, the silicon compound is preferably an alkoxysilane represented by the following general formula (1) or a derivative thereof: Si(OR) ４ (1) (wherein R is an alkyl group, preferably a lower alkyl group having 1 to 8 carbon atoms, more preferably a lower alkyl group having 1 to 4 carbon atoms.)

[0052] Examples of the R include methyl, ethyl, propyl, isopropyl, butyl, pentyl, and hexyl groups, and preferred are tetramethoxysilane where R is a methyl group, tetraethoxysilane where R is an ethyl group, and tetraisopropoxysilane where R is an isopropyl group.Also, examples of the alkoxysilane derivative include low condensates obtained by partially hydrolyzing alkoxysilane.In the present invention, it is preferable to use tetramethoxysilane because it is easy to control the hydrolysis rate, it is easy to obtain single-nm fine silica particles, and there is little residual unreacted material.

[0053] The silicon compound is hydrolyzed and condensed in a reaction solvent to form colloidal silica, which is water or an organic solvent containing water.

[0054] Examples of the organic solvent include hydrophilic organic solvents such as alcohols such as methanol, ethanol, isopropanol, n-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, and 1,4-butanediol, and ketones such as acetone and methyl ethyl ketone.

[0055] The amount of water added to the organic solvent is not particularly limited as long as it is an amount required for the hydrolysis of the silicon compound, and is preferably about 2 to 200 moles per mole of the silicon compound.

[0056] It is preferable to add a basic catalyst to the reaction solvent to adjust the reaction solvent to alkaline. This adjusts the reaction solvent to a pH of preferably 8 to 11, more preferably 8.5 to 10.5, allowing for rapid formation of colloidal silica. The type of basic catalyst is not particularly limited. As the basic catalyst, organic basic catalysts that do not contain metal components are preferred in order to avoid the inclusion of metal impurities, and nitrogen-containing organic basic catalysts are particularly preferred. Examples of such organic basic catalysts include ethylenediamine, diethylenetriamine, triethylenetetraamine, ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, tetramethylammonium hydroxide (TMAH), tetramethylguanidine, 3-ethoxypropylamine, dipropylamine, and triethylamine. These can be used alone or in combination of two or more. Ammonia is preferred because of its excellent catalytic activity and high volatility, allowing for easy removal in a subsequent process. From the viewpoint of increasing the true specific gravity of the silica particles, it is preferable to select an organic base catalyst having a boiling point of 90°C or higher so that the catalyst is less likely to volatilize even at high reaction temperatures, and at least one selected from tetramethylammonium hydroxide and 3-ethoxypropylamine is more preferable.

[0057] In the present invention, colloidal silica is modified with sulfonic acid by adding a silane coupling agent having a mercapto group that can be chemically converted to a sulfonic acid group to colloidal silica, and then converting the mercapto group to a sulfonic acid group. This is because it is difficult to obtain a silane coupling agent having a sulfonic acid group because the sulfonic acid group has high acidity and is prone to hydrolysis.

[0058] Examples of silane coupling agents having a mercapto group include 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane.

[0059] The silane coupling agents having a mercapto group can be used alone or in combination of two or more.

[0060] When adding a coupling agent to colloidal silica, it is preferable for the colloidal silica to contain a hydrophilic organic solvent, taking into consideration the solubility of the coupling agent. In this regard, when colloidal silica is obtained by the Stöber method, in which an alkoxysilane is hydrolyzed and condensed in an alcohol-water solvent using a basic catalyst, the alcohol is contained in the reaction solution, so there is no need to add a hydrophilic organic solvent. In this case, the amount of the hydrophilic organic solvent relative to the water in the colloidal silica is more preferably 5% by mass or more, and this can be adjusted by concentrating the reaction solution as necessary.

[0061] On the other hand, when adding silane coupling agent to water-dispersed colloidal silica, add hydrophilic solvent to the extent that silane coupling agent dissolves.As hydrophilic organic solvent, for example, alcohol such as isopropyl alcohol, ethanol and methanol can be listed.Among these, it is preferable to use the same alcohol as that produced by hydrolysis of silicon compound.This is because by using the same alcohol as that produced by hydrolysis of silicon compound, solvent recovery and reuse can be facilitated.

[0062] The amount of the mercapto group-containing silane coupling agent added is 25.00 to 400.00 μmol / g per 1 g of silica particles. If the amount of silane coupling agent added is less than 25.00 μmol / g, the polishing removal rate of metal using the produced colloidal silica decreases. If the amount of silane coupling agent added is more than 400.00 μmol / g, the amount of abrasive grains remaining on the polished metal surface after polishing and cleaning using the produced colloidal silica increases. The lower limit of the amount of silane coupling agent added is preferably 30.00 μmol / g or more, more preferably 35.00 μmol / g or more. Furthermore, the upper limit of the amount of silane coupling agent added is preferably 380.00 μmol / g or less, more preferably 360.00 μmol / g or less.

[0063] The reaction time when adding the silane coupling agent is not limited, but is preferably 5 minutes to 10 hours, more preferably 10 minutes to 2 hours, and even more preferably 15 minutes to 1 hour.

[0064] The pH of the colloidal silica when the silane coupling agent is added is not limited either, but is preferably from 7 to 11. By setting the upper limit of the pH within the above range, the silane coupling agent becomes more likely to react with the silica surface, and self-condensation of the silane coupling agents themselves is further suppressed.

[0065] In step I described above, a silane coupling agent having a mercapto group is added to colloidal silica, and the colloidal silica is subjected to a modification treatment.

[0066] (Step II) Step II is a step in which hydrogen peroxide is added to the modified colloidal silica to oxidize the mercapto groups on the surface of the silica particles and convert them to sulfo groups.

[0067] In step II, hydrogen peroxide is added to a silane coupling agent having a mercapto group, and the hydrogen peroxide acts as an oxidizing agent, thereby oxidizing the mercapto group that has modified the colloidal silica.

[0068] The amount of hydrogen peroxide added is 3.30 mol / mol or more per mol of the amount of silane coupling agent having a mercapto group. If the amount of hydrogen peroxide added is less than 3.30 mol / mol, the polishing removal rate of metals using the produced colloidal silica changes significantly over time. The amount of hydrogen peroxide added is preferably 3.40 mol / mol or more, more preferably 3.50 mol / mol or more. Furthermore, the amount of hydrogen peroxide added is preferably 6.00 mol / mol or less, more preferably 5.70 mol / mol or less. By setting the upper limit of the amount of hydrogen peroxide added within the above range, corrosion and excessive etching of the metal to be polished are suppressed when polishing metals using the produced colloidal silica, and the risk of expansion and rupture of the filling container due to gas generated by self-decomposition of hydrogen peroxide is reduced.

[0069] By the above-described step II, the mercapto groups on the surface of the silica particles of the modified colloidal silica can be oxidized and converted to sulfo groups.

[0070] (Step III) Step III is a step of heating the colloidal silica to which the hydrogen peroxide has been added at a temperature of 80° C. or higher for 15 hours or longer.

[0071] In the above step III, the temperature at which the colloidal silica is heated is 80°C or higher. If the temperature is lower than 80°C, the polishing removal rate of metals using the produced colloidal silica will change significantly over time. The temperature is preferably 85°C or higher, more preferably 90°C or higher, and even more preferably 95°C or higher. The upper limit of the temperature is not particularly limited, and may be 100°C or lower.

[0072] In the above step III, the heating time for heating the colloidal silica is 15 hours or more. If the heating time is less than 15 hours, the polishing removal rate of metals using the produced colloidal silica will change significantly over time. The heating time is preferably 16 hours or more, more preferably 18 hours or more, and even more preferably 19 hours or more. The upper limit of the heating time is not particularly limited, and may be 50 hours or less, 40 hours or less, or 30 hours or less.

[0073] The sulfonic acid-modified colloidal silica of the present invention can be produced by the above-described step III.

[0074] Since the sulfonic acid-modified colloidal silica obtained according to the above production method may contain solvents other than water, the dispersion medium mainly consisting of the reaction solvent may be replaced with water, if necessary, in order to further improve the long-term storage stability of the colloidal silica. This water replacement may be carried out after the addition of the silane coupling agent in Step I and before the addition of hydrogen peroxide in Step II.

[0075] The method for replacing the dispersion medium mainly composed of the reaction solvent with water is not particularly limited, and examples thereof include a method in which a fixed amount of water is added dropwise to the colloidal silica while heating it.Another example is a method in which the colloidal silica is separated from the dispersion medium mainly composed of the reaction solvent by precipitation, separation, centrifugation, or the like, and then redispersed in water.

[0076] The sulfonic acid-modified colloidal silica of the present invention can be produced by the production method having the steps described above.

[0077] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these.

[0078] Example 1 (Production of Sulfonic Acid-Modified Colloidal Silica) 1935.2 parts by mass of a mixture of 1522.2 parts by mass of tetramethoxysilane and 413.0 parts by mass of methanol was added dropwise to 15,171 parts by mass of a mixture of 2,212.7 parts by mass of pure water, 567.3 parts by mass of 26% by mass aqueous ammonia, and 12,391 parts by mass of methanol over 25 minutes while maintaining the liquid temperature at 20°C, to prepare a silica sol containing water and methanol as a dispersion medium. The silica sol was heated and concentrated under atmospheric pressure to obtain 3,000 parts by mass of a concentrate with a silica particle content of 20% by mass. 3-Mercaptopropyltrimethoxysilane was added to the concentrate as a silane coupling agent, and the mixture was refluxed at the boiling point for thermal aging. Next, the methanol and ammonia were replaced with water while adding pure water to maintain a constant volume, and once the pH reached 8 or less, the liquid temperature of the silica sol was temporarily lowered to room temperature. Next, 35% by mass of hydrogen peroxide water was added, and the mixture was heated again and cooled to room temperature to obtain sulfonic acid-modified colloidal silica. The amount of silane coupling agent added per gram of silica particles, the amount of hydrogen peroxide added per mole of silane coupling agent, the heating temperature after hydrogen peroxide addition, and the heating time after hydrogen peroxide addition were adjusted as shown in Table 1.

[0079] Examples 2 to 9 and Comparative Examples 1 to 5 Sulfonic acid-modified colloidal silica was produced in the same manner as in Example 1, except that the production conditions were as shown in Table 1 and colloidal silica having the properties shown in Table 1 was prepared.

[0080] Example 10 (Production of Sulfonic Acid-Modified Colloidal Silica) 1935.2 parts by mass of a mixture of 1522.2 parts by mass of tetramethoxysilane and 413.0 parts by mass of methanol was added dropwise to 14,498 parts by mass of a mixture of 787.9 parts by mass of pure water, 786.0 parts by mass of 26% by mass aqueous ammonia, and 12,924 parts by mass of methanol over 55 minutes while maintaining the liquid temperature at 35°C, to prepare a silica sol containing water and methanol as a dispersion medium. The silica sol was heated and concentrated under atmospheric pressure to obtain 3,000 parts by mass of a concentrate with a silica particle content of 20% by mass. 3-Mercaptopropyltrimethoxysilane was added to the concentrate as a silane coupling agent, and the mixture was refluxed at the boiling point for thermal aging. Next, the methanol and ammonia were replaced with water while adding pure water to maintain a constant volume. Once the pH reached 8 or less, the liquid temperature of the silica sol was temporarily lowered to room temperature. Next, 35% by mass of hydrogen peroxide water was added, and the mixture was heated again and cooled to room temperature to obtain sulfonic acid-modified colloidal silica. The amount of silane coupling agent added per gram of silica particles, the amount of hydrogen peroxide added per mole of silane coupling agent, the heating temperature after hydrogen peroxide addition, and the heating time after hydrogen peroxide addition were adjusted as shown in Table 1.

[0081] Example 11 (Production of Sulfonic Acid-Modified Colloidal Silica) 1912.6 parts by mass of a mixture of 1522.8 parts by mass of tetramethoxysilane and 389.8 parts by mass of methanol was added dropwise over 30 minutes to 14,449 parts by mass of a mixture of 1,344.8 parts by mass of pure water, 1,111.7 parts by mass of 26% by mass aqueous ammonia, and 11,992 parts by mass of methanol while maintaining the liquid temperature at 20°C, to prepare a silica sol containing water and methanol as a dispersion medium. The silica sol was heated and concentrated under atmospheric pressure to obtain 3,000 parts by mass of a concentrate with a silica particle content of 20% by mass. 3-Mercaptopropyltrimethoxysilane was added to the concentrate as a silane coupling agent, and the mixture was refluxed at the boiling point for thermal aging. Next, the methanol and ammonia were replaced with water while adding pure water to maintain a constant volume, and once the pH reached 8 or less, the liquid temperature of the silica sol was temporarily lowered to room temperature. Next, 35% by mass of hydrogen peroxide water was added, and the mixture was heated again and cooled to room temperature to obtain sulfonic acid-modified colloidal silica. The amount of silane coupling agent added per gram of silica particles, the amount of hydrogen peroxide added per mole of silane coupling agent, the heating temperature after hydrogen peroxide addition, and the heating time after hydrogen peroxide addition were adjusted as shown in Table 1.

[0082] Evaluation Methods The colloidal silica of the Examples and Comparative Examples obtained as described above was evaluated by the following methods.

[0083] (Method for confirming the presence or absence of sulfo groups on particle surfaces by X-ray photoelectron spectroscopy (XPS)) A colloidal silica solution was centrifuged at 77,400 G, 5°C, and 90 minutes. The resulting precipitate was dried at 60°C for 12 hours, and then the silica was pulverized and dried at 60°C under reduced pressure of -0.1 MPa or less gauge pressure for 2 hours to prepare a measurement sample. Using this measurement sample, the presence or absence of sulfo groups on the silica particle surfaces was confirmed by X-ray photoelectron spectroscopy under the following conditions: Measuring instrument: AXIS-NOVA manufactured by Shimadzu Corporation; X-ray irradiation: Al-Kα (15 kV, 10 mA); Analytical X-ray spot diameter: 300 x 700 μm

[0084] Note that a precision analysis was performed near the S2s orbital (binding energy 230 eV) using a value normalized to the Si2p binding energy of 103.60 eV, and the peak at a binding energy of 233 eV was determined to be a peak derived from a sulfo group. The presence or absence of a sulfo group was confirmed based on whether or not the peak derived from the sulfo group was detected.

[0085] (Cu ion adsorption amount of silica particles) The Cu ion adsorption amount of silica particles was measured using the following procedure. 1. 0.1 M HCl was added to 10 g of colloidal silica to adjust the pH to a range of 2.5 to 2.9. 2. A 0.5 M aqueous solution of copper (II) sulfate was added to the colloidal silica so that the amount of Cu (II) ions added per gram of silica was 2,400 μmol, to prepare a solution. The solution was then allowed to stand for 5 minutes. 3. The solution was centrifuged at 77,400 G, 5°C, and 90 minutes. The resulting precipitate was dried at 60°C for 12 hours. 4. The resulting dried powder was crushed in an agate mortar, 20 mL of ultrapure water was added, and the mixture was ultrasonically cleaned for 30 seconds. 5. The solution after ultrasonic cleaning was filtered under reduced pressure using a membrane filter with a pore size of 1 μm, and the silica solids were collected on the membrane filter. 6. The silica solids collected on the membrane filter were dried at 60°C for 12 hours. 7. Steps 4 to 6 were repeated a total of three times to wash off Cu ions not adsorbed on the silica particle surface. 8. The silica solids were further dried at 60°C for 12 hours. 9. 5 mL of 38% hydrofluoric acid was added to 1 g of silica solids, and the mixture was left to stand for 60 minutes to dissolve the silica. Ultrapure water was added to the solution to make a final volume of 100 mL. 10. The Cu ion concentration of the resulting solution was measured using ICP-AES with the absolute calibration curve method. The amount of Cu ions adsorbed per 1 g of silica was calculated from the obtained Cu ion concentration using the following formula: Cu ion adsorption amount (μmol / 1 g of silica) = Cu ion concentration (ppm) / 63.55 (g / mol).

[0086] (Sulfur Content of Silica Particles) The sulfur content of silica particles was measured using the following procedure. 1. Colloidal silica was centrifuged at 77,400 G, 5°C, and 90 minutes. The resulting precipitate was dried at 60°C for 12 hours. 2. The resulting dried powder was crushed in an agate mortar, and 20 mL of ultrapure water was added and ultrasonically cleaned for 30 seconds. 3. The solution after ultrasonic cleaning was filtered under reduced pressure using a membrane filter with a pore size of 1 μm, and the silica solids were recovered on the membrane filter. 4. The silica solids recovered on the membrane filter were dried at 60°C for 24 hours. 5. 5 mL of 38% hydrofluoric acid was added to 1 g of silica solids, and the mixture was left to stand for 60 minutes to dissolve the silica. Ultrapure water was added to the solution to make a final volume of 100 mL. 6. The sulfur concentration of the resulting solution was measured by ICP-AES using the absolute calibration curve method. From the obtained S concentration, the S content per 1 g of silica was calculated using the following formula: S content (μmol / g) = S concentration (ppm) / 32.07 (g / mol)

[0087] (Cu ion adsorption amount / S content) From the values ​​of the Cu ion adsorption amount (μmol / g) and the S content (μmol / g) measured by the above-mentioned measurement method, the Cu ion adsorption amount / S content was calculated by the following formula: [Cu ion adsorption amount / S content]=Cu ion adsorption amount (μmol / g) / S content (μmol / g)

[0088] (Change in Cu ion adsorption amount of silica particles over time) The colloidal silica of each of the examples and comparative examples was allowed to stand at 25° C. for 3 months. The Cu ion adsorption amount (μmol / g) of the silica particles before and after standing was measured, and the change in Cu ion adsorption amount of the silica particles over time was calculated using the following formula: (Change in Cu ion adsorption amount of silica particles over time) = Cu ion adsorption amount after standing (μmol / g) / Cu ion adsorption amount before standing (μmol / g)

[0089] (Measurement of Hydrogen Peroxide Concentration in Colloidal Silica) The hydrogen peroxide concentration in colloidal silica was measured using the following procedure. 1. 48 g of ultrapure water was added to 2.00 g of colloidal silica to prepare a diluted solution. 2. 5 mL of 47% sulfuric acid and 10 mL of a 0.1 g / mL aqueous potassium iodide solution were added to the diluted solution. After the addition, the solution was stirred for 900 seconds using a stirrer in a light-shielded environment. 3. After stirring, potentiometric titration was performed using the following measuring instrument and titration reagent, and the amount of 0.01 mol / L aqueous sodium thiosulfate solution dropped at the endpoint of the titration was determined. Measuring instrument: Automatic Potentiometric Titrator AT-710 manufactured by Kyoto Electronics Manufacturing Co., Ltd. Titration reagent: 0.01 mol / L aqueous sodium thiosulfate solution 4. The amount of 0.01 mol / L sodium thiosulfate solution added at the end of the titration was T mL, and the molecular weight of hydrogen peroxide was 34.02. The hydrogen peroxide concentration of the colloidal silica was calculated using the following formula: Hydrogen peroxide concentration of colloidal silica [ppm] = 0.01 × T × (1 / 1000) × (1 / 2) × 34.02 × (1000000 / 2.00).

[0090] (Silica Particle Content) The silica particle content in colloidal silica was calculated by the following formula: Content [%] of silica particles in colloidal silica = (W ÷ 10.0) × 100, where 10.0 g of colloidal silica was dried on a hot plate at 150°C, and then heated at 800°C for 1 hour to remove moisture, and the amount of solids obtained was defined as W g.

[0091] (Average primary particle diameter) Colloidal silica was pre-dried on a hot plate and then heat-treated at 800°C for 1 hour to prepare a measurement sample. The BET specific surface area was measured using the prepared measurement sample. The true specific gravity of silica was 2.2, and the BET specific surface area (m ２ / g) was converted to the average primary particle diameter (nm) of silica particles in the colloidal silica.

[0092] (Average secondary particle diameter) Colloidal silica was added to a 0.3 mass% aqueous citric acid solution and homogenized to a silica concentration of 0.8 mass%. Using this measurement sample, the average secondary particle diameter (nm) was measured by dynamic light scattering (ELSZ-2000S, manufactured by Otsuka Electronics Co., Ltd.).

[0093] (Metal Impurity Content) The metal impurity content was measured using an atomic absorption spectrometer. The sum of the contents of sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt in the colloidal silica was defined as the metal impurity content.

[0094] (Cu Polishing Rate) After adjusting the colloidal silica of the Examples and Comparative Examples to a silica particle concentration of 3 wt%, the oxidizer concentration and pH were adjusted as follows, and the polishing test was performed. Oxidizer concentration: Hydrogen peroxide concentration 0.25 wt% (based on polishing slurry weight) pH adjustment: pH 2 (using 60% perchloric acid) Polishing test conditions Polishing machine: NF-300CMP manufactured by Nanofactor Co., Ltd. Polishing object: 3 cm x 3 cm square wafer with PVD-Cu film (Cu film thickness 1 μm) Polishing pad: IC1000TM Pad manufactured by Nitta Haas Slurry supply rate: 50 mL / min Head rotation speed: 32 rpm Platen rotation speed: 32 rpm Polishing pressure: Cu film, 1.5 psi Polishing time: Cu film, 1 min Film thickness measuring device: Cu film, electrical resistance type film thickness measuring device

[0095] (Change in Cu polishing rate over time when slurry is left standing) The colloidal silica of each of the examples and comparative examples was left standing at 25°C for 3 months. The Cu polishing rate before and after standing was measured, and the change in Cu polishing rate over time during slurry storage was calculated using the following formula: Change in Cu polishing rate over time when slurry is left standing (%) = (Cu polishing rate after standing (Å / min) - Cu polishing rate before standing (Å / min)) × 100 ÷ Cu polishing rate before standing (Å / min)

[0096] (Amount of particles remaining on the polished surface after polishing and cleaning) The polished PVD-Cu film-coated wafers were cleaned by scrubbing with a PVA roll brush in the scrubbing unit built into a MAT ZAB-8S1M cleaning and drying system under the following conditions: To hold the wafer, a jig was used with a frame made of glass epoxy resin and a wafer fixing part made of polyurethane. Brush: AION SCL BRUSH ROLLER 48 (40 / 26) x 224 mm, manufactured by AION Corporation Scrub cleaning time: 1 min Brush rotation speed: 200 rpm Spin rotation speed of wafer fixing part: 50 rpm After scrubbing, ultrapure water was poured over the polished substrate at 750 mL / min for 1 minute, and then the substrate was further treated in the spin dryer built into the system at 1800 rpm for 20 seconds. After drying, the number of particles remaining on the polished surface of the wafer was measured using an SPM-9700HT manufactured by Shimadzu Corporation.

[0097] The results are shown in Table 1.

[0098]

Claims

1. A sulfonic acid-modified colloidal silica containing silica particles, characterized in that: (1) the surfaces of the silica particles are modified with sulfonic acid groups; (2) the Cu ion adsorption amount of the silica particles is 5.00 to 110.00 μmol / g; (3) the ratio of the Cu ion adsorption amount to the S content of the silica particles (Cu ion adsorption amount (μmol / g) / S content (μmol / g)) is 0.50 or more; and (4) the rate of change with time in the Cu ion adsorption amount of the silica particles, as measured by the following measurement method, is 1.30 or less. [Method for measuring the rate of change with time in the Cu ion adsorption amount of silica particles] The sulfonic acid-modified colloidal silica is allowed to stand at 25°C for 3 months. The Cu ion adsorption amount (μmol / g) of the silica particles before and after standing is measured, and the rate of change over time of the Cu ion adsorption amount (μmol / g) of the silica particles is calculated using the following formula: (rate of change over time of Cu ion adsorption amount of silica particles) = Cu ion adsorption amount after standing (μmol / g) / Cu ion adsorption amount before standing (μmol / g).

2. The sulfonic acid-modified colloidal silica according to claim 1, wherein the amount of Cu ions adsorbed by the silica particles is 8.00 to 105.00 μmol / g.

3. The sulfonic acid-modified colloidal silica according to claim 1, wherein the S content of the silica particles is 10.00 to 200.00 μmol / g.

4. The sulfonic acid-modified colloidal silica according to claim 1, wherein the ratio of the Cu ion adsorption amount to the S content is 0.55 or more.

5. The sulfonic acid-modified colloidal silica according to claim 1, wherein the hydrogen peroxide concentration is 1000 ppm or less.

6. A method for producing sulfonic acid-modified colloidal silica, comprising: (I) Step I of adding a silane coupling agent having a mercapto group to colloidal silica to modify it; (II) Step II of adding hydrogen peroxide to the modified colloidal silica to oxidize the mercapto groups on the silica particle surface and convert them to sulfo groups; and (III) Step III of heating the colloidal silica to which the hydrogen peroxide has been added at a temperature of 80°C or higher for 15 hours or longer; wherein the amount of the silane coupling agent having a mercapto group added is 25.00 to 400.00 μmol / g per 1 g of silica particles; and the amount of the hydrogen peroxide added is 3.30 mol / mol or more per 1 mol of the silane coupling agent having a mercapto group added.

7. The manufacturing method according to claim 6, wherein the silane coupling agent having a mercapto group is at least one selected from the group consisting of 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane.

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