Sulfonic acid modified colloidal silica and method for producing sulfonic acid modified colloidal silica

Abstract

Provided is a sulfonic acid-modified colloidal silica capable of forming a polished surface with significantly reduced surface roughness. The sulfonic acid modified colloidal silica is characterized in that the sulfur content of the silica particles is from 3000 ppm by mass to 9000 ppm by mass per 1 g of the silica particles, the sulfur content in the solvent is 750 ppm by mass or less per 1 g of the solvent, and the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles is 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass.

Description

[Technical field]

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

[0002] In the semiconductor manufacturing process, semiconductor wafers are held on a component called a carrier, and the wafer is brought into contact with and rotated on a polishing pad while a slurry containing chemicals and abrasive grains is poured over it, polishing the semiconductor wafer until it is flat and smooth.

[0003] In the above-mentioned polishing method, chemical mechanical polishing (CMP) is also used, which utilizes the chemical polishing action of chemicals and the mechanical polishing action of abrasive grains.

[0004] In chemical mechanical polishing (CMP), there is a demand for polishing abrasive grains that can provide a polished surface with reduced surface roughness on the semiconductor wafer to be polished.

[0005] Under these circumstances, sulfonic acid-modified colloidal silica, which is colloidal silica (silica sol) modified with sulfonic acid groups (sulfo groups (-SO3H)), has been proposed as an abrasive for polishing semiconductor wafers (see Patent Document 1 (JP 2010-269985 A)). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2010-269985 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0007] However, as a result of studies by the present inventors, it was found that the sulfonic acid-modified colloidal silica proposed in the past has the following problems. (1) The modification level of the sulfo group on the silica particles constituting the sulfonic acid-modified colloidal silica is insufficient, so that the dispersion stability of the silica particles is poor. When the above-mentioned sulfonic acid-modified colloidal silica is used as an abrasive for polishing semiconductor wafers, the silica particles tend to aggregate during storage or polishing, making it difficult to obtain a polished surface with a highly reduced surface roughness. (2) When unreacted silane coupling agent components used in modifying the sulfo groups remain in the solvent of the sulfonic acid-modified colloidal silica and the above-mentioned sulfonic acid-modified colloidal silica is used as an abrasive for polishing semiconductor wafers, the silane coupling agent components remaining in the above-mentioned solvent tend to crosslink and aggregate the silica particles during storage or polishing, making it difficult to obtain a polished surface with significantly reduced surface roughness. This is thought to be because silane coupling agents such as 3-mercaptopropyltrimethoxysilane, which are used to modify silica particles with sulfo groups, are less reactive with silica particles than other silane coupling agents such as 3-aminopropyltrimethoxysilane, and are therefore more likely to remain in the solvent as unreacted silane coupling agents.

[0008] Furthermore, as a result of the studies conducted by the present inventors, it was found that the sulfonic acid-modified colloidal silica that has been proposed in the past has the following problems. (3) When an attempt is made to remove the unreacted silane coupling agent components remaining in the solvent of the sulfonic acid-modified colloidal silica by ultrafiltration, the unreacted silane coupling agent components can be removed, but the content of coarse particles having a particle size of 0.2 μm or more increases due to the progression of aggregation of silica particles constituting the sulfonic acid-modified colloidal silica during ultrafiltration, and when the sulfonic acid-modified colloidal silica obtained by the ultrafiltration is used as abrasive grains for polishing, the roughness of the polished surface increases due to the coarse particles.

[0009] Under these circumstances, an object of the present invention is to provide a sulfonic acid-modified colloidal silica capable of forming a polished surface with highly reduced surface roughness, and a method for producing the sulfonic acid-modified colloidal silica. [Means for solving the problem]

[0010] The present inventors have conducted intensive research in order to solve the above technical problems, and have found that the above problems can be solved by a sulfonic acid-modified colloidal silica, in which the sulfur content of the silica particles is from 3000 ppm by mass to 9000 ppm by mass per 1 g of silica particles, the sulfur content in the solvent is 750 ppm by mass or less per 1 g of solvent, and the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles is 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass, and that the above sulfonic acid-modified colloidal silica can be produced by a specific production method, and have completed the present invention based on these findings.

[0011] That is, the present invention provides (1) A sulfonic acid-modified colloidal silica, The sulfur content of the silica particles is 3000 ppm by mass or more and 9000 ppm by mass or less per 1 g of the silica particles, The sulfur content in the solvent is 750 ppm by mass or less per 1 g of the solvent, The content of coarse particles with a diameter of 0.2 μm or more contained in the silica particles is 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass. A sulfonic acid-modified colloidal silica, (2) A method for producing the sulfonic acid-modified colloidal silica described in (1) above, comprising the steps of: (i) BET specific surface area is 70 to 500 m 2 / g and silanol group density is 7.0 to 20.0 / nm 2the step of contacting a raw material colloidal silica containing silica particles represented by the formula (I) with a silane coupling agent containing a mercapto group to carry out a modification treatment, and then contacting the raw material colloidal silica with hydrogen peroxide to oxidize the mercapto group introduced on the surface of the silica particles to convert it into a sulfo group, (ii) the contact amount of the silane coupling agent containing a mercapto group is 100.00 μmol or more and 400.00 μmol or less per 1 g of the raw material colloidal silica, calculated as a solid content; (iii) when the silane coupling agent containing a mercapto group is brought into contact with the raw colloidal silica, the silane coupling agent is diluted with methanol to a dilution ratio of 3 to 50 times by mass; (iv) the contact amount of the hydrogen peroxide is 3.50 to 10.00 mol per 1 mol of the contact amount of the silane coupling agent containing a mercapto group, (v) after contacting the hydrogen peroxide, heating the resulting mixture at a temperature of 80.0°C or greater for 15 hours or more; A method for producing sulfonic acid-modified colloidal silica, comprising the steps of: This provides: Effect of the Invention

[0012] According to the present invention, it is possible to provide a sulfonic acid modified colloidal silica capable of forming a polished surface with highly reduced surface roughness, and a method for producing the sulfonic acid modified colloidal silica. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] First, the sulfonic acid modified colloidal silica according to the present invention will be described. The sulfonic acid modified colloidal silica according to the present invention is The sulfur content of the silica particles is 3000 ppm by mass or more and 9000 ppm by mass or less per 1 g of the silica particles, The sulfur content in the solvent is 750 ppm by mass or less per 1 g of the solvent, The content of coarse particles with a diameter of 0.2 μm or more contained in the silica particles is 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass. It is characterized in that:

[0014] The sulfonic acid modified colloidal silica according to the present invention is obtained by fixing a sulfo group (-SO3H) to silica particles constituting the colloidal silica.

[0015] The sulfur content of the silica particles in the sulfonic acid modified colloidal silica according to the present invention is from 3000 ppm by mass to 9000 ppm by mass, preferably from 3050 ppm by mass to 8900 ppm by mass, more preferably from 3100 ppm by mass to 8700 ppm by mass, still more preferably from 3150 ppm by mass to 8600 ppm by mass, and particularly preferably from 3200 ppm by mass to 8500 ppm by mass, per 1 g of the silica particles.

[0016] In the present invention, the sulfur content of the silica particles constituting the sulfonic acid modified colloidal silica is an indicator of the amount of sulfo groups (-SO3H) in the silica particles constituting the colloidal silica (the amount of sulfo groups modified on the silica particles). The sulfonic acid modified colloidal silica according to the present invention has a high absolute value of the zeta potential and high dispersion stability of the silica particles due to the sulfonic acid modified colloidal silica having a sulfur content within the above range, and therefore the particles are less likely to aggregate during storage or polishing of the sulfonic acid modified colloidal silica, making it possible to obtain a polished surface with high flatness when the sulfonic acid modified colloidal silica is used as an abrasive grain for polishing.

[0017] In the present application, the sulfur content of the silica particles constituting the sulfonic acid-modified colloidal silica means a value calculated by the following method.

[0018] (Step 1) The sulfonic acid-modified colloidal silica (solution) is centrifuged at 260,000 G, 5°C, and 150 minutes using a centrifuge tube (model number: S303922A) manufactured by Eppendorf Himac Technologies Co., Ltd. The resulting precipitate is dried at 60°C for 12 hours, after which the silica is crushed and dried at 60°C under reduced pressure for 2 hours. (Step 2) Hydrofluoric acid is added to 1 g of the silica solid obtained in Step 1 to dissolve the silica, and ultrapure water is added to the solution to dilute it to 100 mL to obtain a diluted solution. (Step 3) Using the diluted solution obtained in Step 2, the sulfur content (mass ppm) per 1 g of silica particles is measured using an inductively coupled plasma atomic emission spectrometry (ICP-AES) device (Shimadzu Corporation, ICPS-8100) using the absolute calibration curve method.

[0019] Furthermore, whether the sulfonic acid modified colloidal silica according to the present invention contains sulfonic acid modified silica particles can be confirmed by X-ray photoelectron spectroscopy (XPS).

[0020] As described above, the sulfonic acid modified colloidal silica according to the present invention is obtained by fixing sulfo groups (-SO3H) to silica particles constituting colloidal silica, and therefore the sulfonic acid modified colloidal silica according to the present invention has a basic structure derived from colloidal silica.

[0021] In the present application, it is confirmed by the following method that the sulfonic acid modified colloidal silica contains silica particles modified with sulfonic acid. The 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, after which the silica was crushed and dried at 60°C under reduced pressure of -0.1 MPa or less for 2 hours to prepare a measurement sample. Using the measurement sample, the presence or absence of sulfo groups on the silica particle surface is confirmed by X-ray photoelectron spectroscopy under the following conditions. Measuring equipment: AXIS-NOVA manufactured by Shimadzu Corporation Irradiation X-ray: Al-Kα (15kV, 10mA) Analytical X-ray spot diameter: 300 x 700 μm

[0022] As will be described later, one method for preparing colloidal silica is to stir, for example, tetramethoxysilane (Si(OCH3)4) in an organic solvent containing water, thereby forming a dimer through hydrolysis and dehydration condensation, and this dimer is polymerized (oligomerized) to form spherical primary silica particles in the solvent. These spherical primary silica particles dispersed in the solvent correspond to colloidal silica. The colloidal silica may be one in which, together with the above-mentioned primary silica particles, secondary silica particles formed by association of the primary silica particles are dispersed in a solvent. Therefore, the sulfonic acid modified colloidal silica according to the present invention corresponds to the above colloidal silica having sulfo groups (—SO3H) fixed to silica particles dispersed therein.

[0023] The average primary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is not particularly limited, but is preferably 5 nm or more and 39 nm or less.

[0024] The average primary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is preferably 39 nm or less, more preferably 35 nm or less, and even more preferably 31 nm or less.

[0025] When the average primary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is the above value (upper limit value) or less, a polished surface with superior flatness can be formed when polishing is performed using the sulfonic acid modified colloidal silica according to the present invention.

[0026] The average primary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is preferably 5 nm or more, more preferably 6 nm or more, and even more preferably 7 nm or more.

[0027] When the average primary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is equal to or greater than the above value (lower limit value), particle aggregation is less likely to occur when a polishing treatment is performed using the sulfonic acid modified colloidal silica according to the present invention, and therefore a polished surface with superior flatness can be formed.

[0028] In the present application, the average primary particle size of the silica particles contained in the sulfonic acid-modified colloidal silica refers to a value measured by the BET method described below. That is, first, the sulfonic acid-modified colloidal silica is pre-dried on a hot plate at 150°C, and then heat-treated at 800°C for 1 hour to prepare a measurement sample, and the specific surface area S of the obtained measurement sample is measured by the BET method (BET specific surface area). For nearly spherical particles, the average primary particle size (nm) is calculated using the following formula: Average primary particle diameter (nm)=6000 / (BET specific surface area S(m 2 / g) x true density (g / cm 3 )) where the true density of the silica particles is 2.2 g / cm 3 Therefore, the average primary particle size (nm) of silica particles is calculated by the following formula: Average primary particle size of silica particles (nm) = 2727 / specific surface area (m 2 / g) It can be calculated by:

[0029] The sulfonic acid modified colloidal silica according to the present invention may contain secondary particles (secondary silica particles) formed by association of primary silica particles. The secondary silica particles contained in the sulfonic acid-modified colloidal silica according to the present invention, together with the primary silica particles contained in the sulfonic acid-modified colloidal silica according to the present invention, form the main particles of the silica particles, and are distinguished from coarse particles (described later) formed by aggregation of the above-mentioned secondary silica particles.

[0030] The average secondary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is not particularly limited, but is preferably 5 nm or more and 200 nm or less.

[0031] The average secondary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is preferably 200 nm or less, more preferably 180 nm or less, more preferably 160 nm or less, even more preferably 140 nm or less, and particularly preferably 120 nm or less.

[0032] When the average secondary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is the above value (upper limit value) or less, a polished surface with superior flatness can be formed when polishing is performed using the sulfonic acid modified colloidal silica according to the present invention.

[0033] The average secondary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is preferably 5 nm or more, more preferably 10 nm or more, further preferably 15 nm or more, and particularly preferably 20 nm or more.

[0034] When the average secondary particle size of the silica particles contained in the sulfonic acid modified colloidal silica according to the present invention is equal to or greater than the above value (lower limit value), aggregation of the silica particles is less likely to occur when a polishing treatment is performed using the sulfonic acid modified colloidal silica according to the present invention, so that a polished surface with superior flatness can be formed.

[0035] In the present application, the average secondary particle size of the silica particles contained in the sulfonic acid-modified colloidal silica refers to a value measured by the dynamic light scattering method described below. That is, first, a 0.3% by mass aqueous solution of citric acid is added to colloidal silica to dilute it to a silica concentration of 0.8% by mass, and the resulting diluted solution is used as a measurement sample. The average particle size measured by dynamic light scattering using the above measurement sample and a Zeta potential / particle size / molecular weight measurement system "ELSZ-2000S" manufactured by Otsuka Electronics Co., Ltd. is regarded as the average secondary particle size of the silica particles.

[0036] The sulfonic acid modified colloidal silica according to the present invention has a sulfur content in a solvent of 750 ppm by mass or less per 1 g of the solvent.

[0037] The sulfur content in the solvent of the sulfonic acid modified colloidal silica according to the present invention is 750 ppm by mass or less, preferably 740 ppm by mass or less, more preferably 730 ppm by mass or less, and even more preferably 720 ppm by mass or less, per 1 g of the solvent.

[0038] In the sulfonic acid-modified colloidal silica according to the present invention, the sulfur content in the solvent is an index of the amount of unreacted silane coupling agent components remaining in the solvent. The sulfonic acid modified colloidal silica according to the present invention has a sulfur content in a solvent of the above-mentioned value (upper limit value) or less, and therefore when the sulfonic acid modified colloidal silica is used as an abrasive for polishing, a polished surface with high flatness can be obtained.

[0039] In the sulfonic acid-modified colloidal silica according to the present invention, the lower limit of the sulfur content in the solvent is not particularly limited, and the lower the better; however, the sulfur content in the solvent of the sulfonic acid-modified colloidal silica according to the present invention may be, for example, 1 ppm by mass or more, 5 ppm by mass or more, or 10 ppm by mass or more.

[0040] As described above, the inventors have found through their investigations that, when a semiconductor wafer is polished using a conventionally known sulfonic acid modified colloidal silica, the unreacted silane coupling agent component used for modifying the sulfo group (-SO3H) remains in the solvent of the sulfonic acid modified colloidal silica, and during storage or polishing, the silane coupling agent component remaining in the solvent crosslinks the silica particles together and tends to cause agglomeration, making it difficult to obtain a polished surface with significantly reduced surface roughness. In contrast, the sulfonic acid-modified colloidal silica of the present invention is obtained by limiting the sulfur content in the solvent to a predetermined amount or less, and the silica particles are unlikely to crosslink with each other and aggregate, so that when used as abrasive grains for polishing semiconductor wafers, a polished surface with high flatness can be easily obtained.

[0041] In the present application, the sulfur content in the solvent of the sulfonic acid-modified colloidal silica means a value calculated by the following method. (Step 1) The sulfonic acid-modified colloidal silica in solution is subjected to centrifugal filtration processing at 12,000 rpm for 10 minutes using a centrifugal ultrafiltration unit manufactured by Sartorius AG (model number: VN01H92, molecular weight cutoff 2,000), and the filtrate that passes through the ultrafiltration membrane is collected. (Step 2) The sulfur concentration (ppm by mass) in the filtrate obtained in step 1 is measured using an inductively coupled plasma atomic emission spectrometry (ICP-AES) device (Shimadzu Corporation, ICPS-8100) using the absolute calibration curve method.

[0042] The presence of the silane coupling agent remaining in the solvent of the sulfonic acid-modified colloidal silica according to the present invention can be confirmed by determining the sulfur content of the silica particles by liquid chromatography mass spectrometry (LC-MS) or by the above-mentioned method, and comparing it with the amount of the silane coupling agent subjected to the reaction (contacted with the raw colloidal silica).

[0043] In the sulfonic acid modified colloidal silica according to the present invention, the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles is 10,000,000 particles / mL or less, preferably 9,800,000 particles / mL or less, and more preferably 9,600,000 particles / mL or less, when the silica particle concentration (in the sulfonic acid modified colloidal silica) is 1% by mass.

[0044] In the sulfonic acid modified colloidal silica according to the present invention, the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles is equal to or less than the above value (upper limit) when the silica particle concentration in the sulfonic acid modified colloidal silica is 1 mass %, so that when the sulfonic acid modified colloidal silica according to the present invention is used for chemical mechanical polishing (CMP), roughness of the polished surface caused by the presence of coarse particles can be suppressed and a polished surface with high flatness can be easily formed.

[0045] In the sulfonic acid-modified colloidal silica according to the present invention, the lower limit of the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles is not particularly limited, but in the sulfonic acid-modified colloidal silica according to the present invention, the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles can be 1,000 particles / mL or more when the silica particle concentration is 1 mass%, and it is preferable that no coarse particles are contained (0 particles / mL).

[0046] As described above, according to the studies of the present inventors, it was found that unreacted silane coupling agent components remain in conventionally known sulfonic acid modified colloidal silica, and when this unreacted silane coupling agent is removed by ultrafiltration, the primary silica particles constituting the sulfonic acid modified colloidal silica tend to aggregate and generate a large amount of coarse particles having a particle size of 0.2 μm or more, and when the obtained sulfonic acid modified colloidal silica is used as abrasive grains for polishing, the roughness of the polished surface increases. The sulfonic acid modified colloidal silica according to the present invention has a reduced content of coarse particles having a particle size of 0.2 μm or more. Therefore, when the sulfonic acid modified colloidal silica according to the present invention is used for chemical mechanical polishing (CMP), a polished surface with high flatness can be easily formed.

[0047] In this application, the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles constituting the sulfonic acid-modified colloidal silica means a value measured by the particle size distribution measurement method using a number counting method described below. <Method for measuring the content of coarse particles with a particle size of 0.2 μm or more contained in silica particles> Ultrapure water is added to the sulfonic acid-modified colloidal silica to be measured, so that the silica particle concentration becomes 1.0 mass %. The resulting diluted solution is used as a measurement sample, and the number of coarse particles with a particle size of 0.2 μm or more is measured using an Accusizer FX-nano manufactured by Particle Sizing Systems Inc. under the following measurement conditions. <System Setup> ·Stirred Vessel Volume: 13.22 mL ·Sample Loop Volume: 0.52 mL ·Autodilution delay time : 3 sec. ·Normal Speed ​​Flow Rate: 15 mL / min <Sensor Setup Menu> ·FX-Nano HG Minimum Size: 0.15μm ·FX-Nano HG Maximum Size: 0.27μm ·FX-Nano HG Collection Time: 60sec. ·HG Starting Concentration : 8000♯ / mL

[0048] The pH of the sulfonic acid-modified colloidal silica according to the present invention may be appropriately set depending on the application, and is not particularly limited, but is preferably 2.0 or more and 11.0 or less.

[0049] The pH of the sulfonic acid modified colloidal silica according to the present invention is preferably 2.0 or more, more preferably 2.5 or more, and even more preferably 3.0 or more. When the pH of the sulfonic acid modified colloidal silica according to the present invention is the above value (lower limit value) or more, the dispersion stability of the silica particles in the sulfonic acid modified colloidal silica according to the present invention is easily improved, and the sulfonic acid modified colloidal silica according to the present invention is less likely to cause particle aggregation during storage or polishing, making it possible to easily form a polished surface with high flatness when used as abrasive grains for polishing.

[0050] The pH of the sulfonic acid modified colloidal silica according to the present invention is preferably 11.0 or less, more preferably 10.8 or less, even more preferably 10.6 or less, and particularly preferably 10.4 or less. When the pH of the sulfonic acid modified colloidal silica according to the present invention is the above value (upper limit value) or less, the long-term dispersion stability of the sulfonic acid modified colloidal silica can be further improved, and when used as abrasive grains for polishing, a polished surface with high flatness can be easily formed.

[0051] In the present application, pH refers to a value measured using a pH meter F-2000PI (manufactured by Horiba, Ltd.) equipped with a pH electrode 9615S-10D (manufactured by Horiba, Ltd.).

[0052] The content of silica particles in the sulfonic acid-modified colloidal silica according to the present invention is not particularly limited, but is preferably 1% by mass or more and 50% by mass or less, assuming that the content of the sulfonic acid-modified colloidal silica is 100% by mass.

[0053] The content of silica particles in the sulfonic acid-modified colloidal silica according to the present invention is preferably 1 mass % or more, more preferably 3 mass % or more, and even more preferably 5 mass % or more, based on the content of the sulfonic acid-modified colloidal silica being 100 mass %.

[0054] When the content of silica particles in the sulfonic acid modified colloidal silica according to the present invention is the above value (lower limit value) or more, the polishing performance is further improved when the sulfonic acid modified colloidal silica according to the present invention is used as abrasive grains for polishing.

[0055] The content of silica particles in the sulfonic acid modified colloidal silica according to the present invention is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. When the content of silica particles in the sulfonic acid-modified colloidal silica according to the present invention is the above value (upper limit value) or less, the dispersion stability of the silica particles can be further improved.

[0056] In the present application, the content of silica particles in the sulfonic acid-modified colloidal silica according to the present invention means a value measured by the following measurement method. That is, 10.0 g of sulfonic acid-modified colloidal silica is dried on a hot plate at 150°C, and then heat-treated at 800°C for 1 hour to remove moisture, and the amount of the obtained solid content is defined as Wg, and the value is calculated from the following formula. Content of silica particles in sulfonic acid modified colloidal silica (mass%) = (W / 10.0) x 100 The content of the silica particles corresponds to the total content of primary silica particles, secondary silica particles and coarse particles in the sulfonic acid-modified colloidal silica.

[0057] The sulfonic acid modified colloidal silica according to the present invention may contain metal impurities.

[0058] In the sulfonic acid modified colloidal silica according to the present invention, the metal impurities can be one or more selected from the group consisting of sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, cobalt, and the like.

[0059] In the sulfonic acid modified colloidal silica according to the present invention, the total content of metal impurities is preferably 1 ppm by mass or less. Since the total content of metal impurities is 1 ppm by mass or less, the sulfonic acid modified colloidal silica according to the present invention can be suitably used as abrasive grains for polishing electronic materials such as semiconductor wafers.

[0060] In the present application, the content of metal impurities means a value measured using an atomic absorption spectrometer.

[0061] The sulfonic acid-modified colloidal silica according to the present invention can be suitably prepared by the production method according to the present application described below.

[0062] According to the present invention, it is possible to provide a sulfonic acid-modified colloidal silica capable of forming a polished surface with highly reduced surface roughness.

[0063] Next, a method for producing the sulfonic acid-modified colloidal silica according to the present invention will be described. The method for producing sulfonic acid-modified colloidal silica according to the present invention comprises the steps of: (i) BET specific surface area is 70 to 500 m 2 / g and silanol group density is 7.0 to 20.0 / nm 2 the step of contacting a raw material colloidal silica containing silica particles represented by the formula (I) with a silane coupling agent containing a mercapto group to carry out a modification treatment, and then contacting the raw material colloidal silica with hydrogen peroxide to oxidize the mercapto group introduced on the surface of the silica particles to convert it into a sulfo group, (ii) the contact amount of the silane coupling agent containing a mercapto group is 100.00 μmol or more and 400.00 μmol or less per 1 g of the raw material colloidal silica, calculated as a solid content; (iii) when the silane coupling agent containing a mercapto group is brought into contact with the raw colloidal silica, the silane coupling agent is diluted with methanol to a dilution ratio of 3 to 50 times by mass; (iv) the contact amount of the hydrogen peroxide is 3.50 to 10.00 mol per 1 mol of the contact amount of the silane coupling agent containing a mercapto group, (v) after contacting the hydrogen peroxide, heating the resulting mixture at a temperature of 80.0°C or greater for 15 hours or more; It is characterized by the above.

[0064] (Raw material colloidal silica) In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the BET specific surface area is 70 to 500 m 2 / g and silanol group density is 7.0 to 20.0 / nm 2 The raw material colloidal silica is used, which contains silica particles having the following formula:

[0065] In the method for producing a sulfonic acid-modified colloidal silica according to the present invention, the raw material colloidal silica can be appropriately selected from colloidal silica having desired properties produced by a known production method, and examples of such colloidal silica having desired properties produced by a sol-gel method can include colloidal silica. In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the raw material colloidal silica produced by a sol-gel method can be preferably used because it contains a small amount of metal impurities capable of diffusing into a semiconductor and corrosive ions such as chloride ions.

[0066] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, when colloidal silica produced by a sol-gel method is used as the raw material colloidal silica, the method for producing the colloidal silica can be a conventionally known method. Specifically, the colloidal silica can be produced by carrying out a hydrolysis and condensation reaction using one or more hydrolyzable silicon compounds (e.g., alkoxysilanes or derivatives thereof) as raw materials.

[0067] The silicon compound is represented by the following general formula (1): Si(OR)4(1) (In the above general formula (1), the R group is an alkyl group having 1 to 8 carbon atoms.) Examples of the tetraalkoxysilane include those represented by the following formula:

[0068] In the silicon compound represented by the general formula (1) or a derivative thereof, the R group is an alkyl group having 1 to 8 carbon atoms, and preferably an alkyl group having 1 to 4 carbon atoms.

[0069] In the silicon compound or derivative thereof represented by general formula (1), examples of the R group include one or more groups selected from a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group, and preferably one or more groups selected from a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group.

[0070] As the silicon compound represented by the general formula (1), tetramethoxysilane in which the R group is a methyl group, tetraethoxysilane in which the R group is an ethyl group, or tetraisopropoxysilane in which the R group is an isopropyl group are preferred. Moreover, examples of the derivatives of the silicon compound represented by the general formula (1) include low condensates obtained by partially hydrolyzing the silicon compound represented by the general formula (1) (tetraalkoxysilane). As the silicon compound represented by the general formula (1) or a derivative thereof, tetramethoxysilane is preferred, since the hydrolysis rate can be easily controlled, fine silica particles can be easily obtained, and little unreacted material remains.

[0071] The silicon compound represented by the general formula (1) or its derivative undergoes hydrolysis and condensation in the reaction solvent to become colloidal silica.

[0072] Examples of the dispersion solvent (reaction solvent) used when the silicon compound represented by the general formula (1) or its derivative is hydrolyzed and condensed include water and organic solvents containing water. The organic solvent may be at least one selected from 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. Among these organic solvents, it is particularly preferable to use alcohols such as methanol, ethanol, and isopropanol. From the viewpoint of post-treatment of the reaction solvent, it is more preferable to use alcohols having the same alkyl group as the alkyl group (R group) of the starting silicon compound (e.g., methanol for tetramethoxysilane).

[0073] The amount of the organic solvent used is not particularly limited, but is preferably 5 to 50 moles per mole of the silicon compound represented by the general formula (1) or its derivative. When the amount of the organic solvent used is less than 5 moles per mole of the silicon compound represented by general formula (1) or its derivative, it may be difficult to exhibit compatibility with the silicon compound represented by general formula (1). When the amount of the organic solvent used is more than 50 moles per mole of the silicon compound represented by general formula (1) or its derivative, the production efficiency may decrease.

[0074] The amount of water to be added to the silicon compound represented by the general formula (1) or its derivative is not particularly limited as long as it is an amount required for hydrolysis of the silicon compound represented by the general formula (1), and is preferably about 2 to 200 moles per mole of the silicon compound represented by the general formula (1). When an organic solvent containing water is added to the silicon compound represented by the general formula (1) or a derivative thereof, the amount of water mixed with the organic solvent significantly affects the particle size of the colloidal silica formed. By increasing the amount of water added relative to the amount of organic solvent added, the particle size of the resulting colloidal silica can be relatively increased, and by decreasing the amount of water added relative to the amount of organic solvent added, the particle size of the resulting colloidal silica can be relatively decreased. In this way, by changing the mixing ratio of water and organic solvent, the particle size of the resulting colloidal silica can be adjusted as desired.

[0075] The reaction solvent for the hydrolysis and condensation reaction of the silicon compound to obtain colloidal silica is preferably adjusted to be alkaline in the presence of a basic catalyst. By the above adjustment, the pH of the reaction solvent is controlled to preferably 8.0 to 11.0, more preferably 8.5 to 10.5, and colloidal silica can be rapidly formed.

[0076] From the viewpoint of preventing the inclusion of impurities, the basic catalyst is preferably one or more selected from organic amines and ammonia, and more preferably one or more selected from ethylenediamine, diethylenetriamine, triethylenetetraamine, ammonia, urea, ethanolamine, tetramethylammonium hydroxide, and the like.

[0077] To hydrolyze and condense a silicon compound in a reaction solvent, the silicon compound represented by the general formula (1) or its derivative is added to a solvent containing water, and the mixture is stirred at a temperature generally in the range of 0°C to 100°C, preferably 0°C to 50°C.

[0078] By stirring a silicon compound in a solvent containing water, hydrolysis and dehydration condensation reactions of the silicon compound represented by general formula (1) or its derivative proceed. First, the silicon compound represented by general formula (1) or its derivative undergoes dehydration condensation to form a dimer, and this dimer undergoes polymerization (oligomerization) to form spherical primary silica particles in the solvent, thereby obtaining colloidal silica in which the primary silica particles are dispersed in the solvent. Colloidal silica with a uniform silica particle size can be obtained by hydrolyzing and condensing a silicon compound while stirring it in a solvent containing water.

[0079] The colloidal silica obtained by the above hydrolysis and condensation reaction (sol-gel method) can be used as the raw colloidal silica in the production method of the present invention by appropriately adjusting the concentration.

[0080] Method for producing sulfonic acid-modified colloidal silica according to the present invention The BET specific surface area of ​​the silica particles constituting the raw colloidal silica is 70 to 500 m 2 / g, 75 to 450m2 / g, and 80 to 400m 2 It is more preferable that the molecular weight is / g.

[0081] In the present application, the BET specific surface area of ​​the silica particles constituting the raw material colloidal silica means the specific surface area measured by the BET method using a BET specific surface area measuring device (AUTOSORB 6B manufactured by QUANTACHROME INSTRUMENTS).

[0082] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the silanol group density of the silica particles constituting the raw colloidal silica is 7.0 to 20.0 particles / nm 2 and 7.1 to 19.0 particles / nm 2 is preferably 7.2 to 18.0 particles / nm 2 It is more preferable that:

[0083] In the present application, the silanol group density of the silica particles constituting the raw material colloidal silica means a value calculated by the following method. That is, based on the Sears method described in GW Sears, Jr., “Determination of Specific Surface Area of ​​Colloidal Silica by Titration with Sodium Hydroxide”, Analytical Chemistry, 28(12), 1981(1956), the silica particle concentration of the raw colloidal silica to be measured is adjusted to 1 mass%, and then titrated with a 0.1 mol / L aqueous sodium hydroxide solution to obtain the silanol group density “ρ” (number / nm 2 ) ρ = (a×f×6022)÷(c×S) ρ: Silanol group density (pieces / nm 2 ) a: Amount of 0.1 mol / L sodium hydroxide solution with pH 4 to pH 9 added (mL) f: Factor of 0.1 mol / L sodium hydroxide solution c: mass of silica particles (g) S:BET specific surface area (m 2 / g)

[0084] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, since the BET specific surface area and silanol group density of the silica particles constituting the raw material colloidal silica are within the above-mentioned ranges, the reaction points with a silane coupling agent containing a mercapto group (described later) formed on the silica particle surface can be easily controlled within a suitable range.

[0085] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the raw material colloidal silica is brought into contact with a silane coupling agent containing a mercapto group to carry out a modification treatment.

[0086] As the silane coupling agent having a mercapto group, mercaptoalkylalkoxysilane is preferred, and mercaptoalkyltrialkoxysilane is more preferred. Specific examples of such silane coupling agents having a mercapto group include 3-mercaptopropyltrimethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane.

[0087] The contact amount of the silane coupling agent containing the mercapto group is, in terms of solid content, 100.00 μmol or more and 400.00 μmol or less, preferably 110.00 μmol or more and 390.00 μmol or less, and more preferably 120.00 μmol or more and 380.00 μmol per 1 g of the raw colloidal silica (per 1 g of silica particles contained in the raw colloidal silica).

[0088] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, by ensuring that the contact amount of the mercapto group-containing silane coupling agent is within the above-mentioned range, the surfaces of the silica particles can be sufficiently anionized while easily controlling the amount of silane coupling agent remaining in the solvent of the resulting sulfonic acid-modified colloidal silica (sulfur content in the solvent), and a sulfonic acid-modified colloidal silica that exhibits excellent performance when used as abrasive grains for polishing can be easily prepared.

[0089] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the dispersion medium for the raw material colloidal silica may be an organic solvent containing water, as described above. In the method for producing sulfonic acid-modified colloidal silica according to the present invention, when the raw colloidal silica is brought into contact with a silane coupling agent containing a mercapto group, it is preferable to use raw colloidal silica containing a certain amount or more of an organic solvent (hydrophilic solvent) as a dispersion medium for the purpose of dissolving the silane coupling agent, since the silane coupling agent is difficult to dissolve in water.

[0090] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, when the silane coupling agent containing a mercapto group is brought into contact with the raw colloidal silica, the silane coupling agent is preferably brought into contact with the raw colloidal silica while being diluted with methanol to a dilution ratio of 3 to 50 times by mass, or is preferably brought into contact with the raw colloidal silica while being diluted with methanol to a dilution ratio of 4 to 45 times by mass, and is more preferably brought into contact with the raw colloidal silica while being diluted with methanol to a dilution ratio of 5 to 40 times by mass.

[0091] In the method for producing a sulfonic acid-modified colloidal silica according to the present invention, the dilution ratio of the mercapto group-containing silane coupling agent with methanol means a calculated value based on a mass ratio, and specifically means a value calculated by "amount of methanol used for dilution (g) / amount of mercapto group-containing silane coupling agent (g)".

[0092] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, when the mercapto group-containing silane coupling agent is brought into contact with the raw colloidal silica, the silane coupling agent is brought into contact with the raw colloidal silica while being diluted with methanol to a predetermined dilution ratio, whereby the silane coupling agent is suitably mixed, and a desired amount of the silane coupling agent can be effectively fixed to the silica particles constituting the raw colloidal silica while suppressing local reactions when the coupling agent is added. As a result, the amount of the silane coupling agent remaining in the solvent constituting the finally obtained sulfonic acid-modified colloidal silica can be significantly reduced.

[0093] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, when the raw material colloidal silica is brought into contact with a silane coupling agent containing a mercapto group to carry out the modification treatment, the contact treatment is preferably carried out while appropriately carrying out a heat treatment in a temperature range from room temperature (about 20°C) to the boiling point of the reaction solvent, although there are no particular limitations thereon. The contact time (reaction time) during the contact treatment is not particularly limited, but is preferably from 10 minutes to 10 hours, more preferably from 30 minutes to 5 hours, and even more preferably from 30 minutes to 2 hours. The pH at which the contact treatment is carried out is not limited, but a pH of 7 or more and 11 or less is preferred. By carrying out the contact treatment while carrying out the heat treatment, the hydrolysis and condensation reactions are promoted, and the silane coupling agent containing a mercapto group can be suitably fixed (chemically bonded) to the surface of the silica particles constituting the raw material colloidal silica.

[0094] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the raw colloidal silica is brought into contact with a silane coupling agent containing a mercapto group (-SH) to carry out a modification treatment, and then the raw colloidal silica is brought into contact with hydrogen peroxide to oxidize the mercapto group introduced on the silica particle surface and convert it to a sulfo group (-SO3H).

[0095] The contact amount of hydrogen peroxide with respect to the contact reaction product of the raw material colloidal silica and the silane coupling agent containing a mercapto group (-SH) is 3.50 to 10.00 mol, preferably 3.55 to 8.00 mol, and more preferably 3.60 to 6.00 mol per 1 mol of the contact amount of the silane coupling agent having a mercapto group used in preparing the contact reaction product.

[0096] By controlling the amount of hydrogen peroxide contacted with the contact reaction product of the raw colloidal silica and the silane coupling agent containing a mercapto group (-SH) within the above range, it is possible to favorably proceed with the conversion of the mercapto group (-SH) to a sulfo group (-SO3H) while minimizing the concentration of the residual oxidizing agent in the obtained sulfonic acid-modified colloidal silica.

[0097] The residual oxidizing agent concentration in the sulfonic acid modified colloidal silica obtained by the production method according to the present invention is not particularly limited, but is preferably 3000 ppm by mass or less, more preferably 2500 ppm by mass or less, and even more preferably 2000 ppm by mass or less.

[0098] When the residual oxidizing agent concentration in the sulfonic acid-modified colloidal silica obtained by the production method of the present invention is the above-mentioned value (upper limit value) or less, wafer dishing can be effectively suppressed when the sulfonic acid-modified colloidal silica obtained by the production method of the present invention is used as abrasive grains for polishing semiconductor wafers.

[0099] As described above, by contacting hydrogen peroxide with the contact reaction product of raw colloidal silica and a silane coupling agent containing a mercapto group (-SH), the mercapto group (-SH) of the silane coupling agent can be converted to a sulfo group (-SO3H). However, the parts of the silane coupling agent other than the mercapto group and the raw colloidal silica have a structure that is stable against hydrogen peroxide, so by-products are unlikely to be produced.

[0100] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the raw colloidal silica is first modified by contacting it with a silane coupling agent containing a mercapto group (-SH), and then the mercapto group (-SH) is converted to a sulfo group (-SO3H), thereby stably modifying the surface of the silica particles with the silane coupling agent having a sulfo group (-SO3H).

[0101] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, after bringing into contact with hydrogen peroxide a contact reaction product of the raw colloidal silica and a silane coupling agent containing a mercapto group (-SH), the resulting mixture is heated at a temperature of 80.0°C or higher, preferably at a temperature of 85.0°C or higher, more preferably at a temperature of 90.0°C or higher, and even more preferably at a temperature of 95.0°C or higher. In the method for producing the sulfonic acid-modified colloidal silica according to the present invention, the upper limit of the temperature to which the mixture obtained after the contact reaction product of the raw material colloidal silica and the silane coupling agent containing a mercapto group (-SH) is contacted with hydrogen peroxide is not particularly limited, and may be 100.0°C or lower. When the heating temperature is 80.0° C. or higher, the amount of unreacted silane coupling agent remaining in the solvent in the obtained sulfonic acid-modified colloidal silica can be effectively suppressed.

[0102] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the heating time for which the contact reaction product of the raw colloidal silica and the silane coupling agent containing a mercapto group (-SH) is contacted with hydrogen peroxide and then the resulting mixture is heated is 15 hours or more, preferably 16 hours or more, more preferably 18 hours or more, and even more preferably 19 hours or more. In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the upper limit of the heating time for heating the mixture obtained after contacting the contact reaction product of the raw material colloidal silica and the silane coupling agent containing a mercapto group (-SH) with hydrogen peroxide is not particularly limited, and may be 50 hours or less, 40 hours or less, or 30 hours or less. By setting the heating time to 15 hours or longer, the amount of unreacted silane coupling agent remaining in the solvent in the obtained sulfonic acid-modified colloidal silica can also be effectively suppressed.

[0103] The reaction liquid obtained by contacting the above hydrogen peroxide and heating the resulting mixture at a temperature of 80.0°C or higher for 15 hours or more contains an organic solvent such as methanol in addition to water. Therefore, in order to improve the long-term storage stability, the dispersion medium of the resulting reaction liquid may be replaced with water, if necessary. The substitution with water may be carried out after the mercapto group-containing silane coupling agent is contacted with the raw material colloidal silica, and before the obtained contact reaction product is contacted with hydrogen peroxide.

[0104] The method for replacing the dispersion medium with water is not particularly limited, and examples thereof include a method in which the hydrogen peroxide is contacted with the mixture, the resulting mixture is heated at a temperature of 80.0°C or higher for 15 hours or more, and water is added dropwise in a fixed amount while heating the resulting reaction liquid.

[0105] In the method for producing sulfonic acid-modified colloidal silica according to the present invention, the amount of silane coupling agent remaining in the solvent of the obtained sulfonic acid-modified colloidal silica is reduced, so that the amount of silane coupling agent remaining in the solvent can be easily controlled to a suitable range without carrying out ultrafiltration. For this reason, in the method for producing the sulfonic acid-modified colloidal silica according to the present invention, it is preferable not to carry out ultrafiltration treatment.

[0106] Details of the sulfonic acid-modified colloidal silica obtained by the production method according to the present invention are as described above in the description of the sulfonic acid-modified colloidal silica according to the present invention.

[0107] According to the present invention, there is provided a method for producing sulfonic acid-modified colloidal silica capable of forming a polished surface with highly reduced surface roughness. EXAMPLES

[0108] EXAMPLES Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples in any way.

[0109] Example 1 The raw colloidal silica is colloidal silica (BET specific surface area 90m 2 / g, silanol group density 7.5 / nm 2 A modification treatment was performed by contacting the colloidal silica (silica particle concentration 20% by mass) with 3-mercaptopropyltrimethoxysilane diluted 10 times by mass with methanol for 1 hour under conditions of pH 9.8 and 60.0°C so that the contact amount of the 3-mercaptopropyltrimethoxysilane was 145.00 μmol / g per 1 g of the colloidal silica (silica particles in the raw colloidal particles) calculated as a solid content. Next, 35 mass% hydrogen peroxide solution was added to the contact and modified product of the colloidal silica and 3-mercaptopropyltrimethoxysilane in an amount equivalent to 4.00 mol of hydrogen peroxide per 1 mol of the contact amount of the 3-mercaptopropyltrimethoxysilane, and then heated at 100.0°C for 20 hours. Thereafter, the mixture was cooled to room temperature to obtain the desired sulfonic acid-modified colloidal silica. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (%) by mass, the average primary particle diameter of the silica particles, the average secondary particle diameter of the silica particles, the content (pieces / mL) of coarse particles having a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1 mass%, the metal impurity content (ppm by mass), and the pH were determined. The metal impurity content was measured and calculated as the sum of the contents of sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, and cobalt in the sulfonic acid-modified colloidal silica. The results are shown in Table 2.

[0110] Example 2 The raw colloidal silica is colloidal silica (BET specific surface area 147m 2 / g, silanol group density 15.2 / nm 2 , silica particle concentration 20% by mass) and 3-mercaptopropyltrimethoxysilane diluted 10 times by mass with methanol were mixed so that the contact amount of the 3-mercaptopropyltrimethoxysilane was 180.00 μmol per 1 g of colloidal silica (silica particles in the raw colloidal particles) calculated as a solid content. The denaturation treatment was carried out by contacting the mixture at pH 9.7 and 60.0° C. for 1 hour. Next, 35% by mass hydrogen peroxide solution in an amount equivalent to 4.00 mol of hydrogen peroxide per 1 mol of the contact amount of the 3-mercaptopropyltrimethoxysilane was added to the contact and modified product of the colloidal silica and 3-mercaptopropyltrimethoxysilane, and the mixture was heated at 100.0°C for 20 hours. Thereafter, the mixture was cooled to room temperature to obtain the desired sulfonic acid-modified colloidal silica. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (% by mass), the average primary particle size of the silica particles, the average secondary particle size of the silica particles, the content (pieces / mL) of coarse particles with a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1% by mass, the metal impurity content (ppm by mass), and the pH were determined in the same manner as in Example 1. The results are shown in Table 2.

[0111] Example 3 The raw colloidal silica is colloidal silica (BET specific surface area 170 m 2 / g, silanol group density 9.6 / nm 2 , silica particle concentration 20% by mass) and 3-mercaptopropyltrimethoxysilane diluted 10 times by mass with methanol were mixed so that the contact amount of the 3-mercaptopropyltrimethoxysilane was 190.00 μmol per 1 g of colloidal silica (silica particles in the raw colloidal particles) calculated as solid content. The denaturation treatment was carried out by contacting the mixture at pH 7.1 and 60.0° C. for 1 hour. Next, 35% by mass hydrogen peroxide solution in an amount equivalent to 4.00 mol of hydrogen peroxide per 1 mol of the contact amount of the 3-mercaptopropyltrimethoxysilane was added to the contact and modified product of the colloidal silica and 3-mercaptopropyltrimethoxysilane, and the mixture was heated at 100.0°C for 20 hours. Thereafter, the mixture was cooled to room temperature to obtain the desired sulfonic acid-modified colloidal silica. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (% by mass), the average primary particle size of the silica particles, the average secondary particle size of the silica particles, the content (pieces / mL) of coarse particles with a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1% by mass, the metal impurity content (ppm by mass), and the pH were determined in the same manner as in Example 1. The results are shown in Table 2.

[0112] Example 4 The raw colloidal silica is colloidal silica (BET specific surface area 280m 2 / g, silanol group density 8.1 / nm 2 , silica particle concentration 20% by mass) and 3-mercaptopropyltrimethoxysilane diluted 10 times by mass with methanol were mixed so that the contact amount of the 3-mercaptopropyltrimethoxysilane was 250.00 μmol per 1 g of colloidal silica (silica particles in the raw colloidal particles) calculated as a solid content. The denaturation treatment was carried out by contacting the mixture at pH 10.7 and 60.0° C. for 1 hour. Next, 35% by mass hydrogen peroxide solution in an amount equivalent to 4.00 mol of hydrogen peroxide per 1 mol of the contact amount of the 3-mercaptopropyltrimethoxysilane was added to the contact and modified product of the colloidal silica and 3-mercaptopropyltrimethoxysilane, and the mixture was heated at 100.0°C for 20 hours. Thereafter, the mixture was cooled to room temperature to obtain the desired sulfonic acid-modified colloidal silica. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (% by mass), the average primary particle size of the silica particles, the average secondary particle size of the silica particles, the content (pieces / mL) of coarse particles with a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1% by mass, the metal impurity content (ppm by mass), and the pH were determined in the same manner as in Example 1. The results are shown in Table 2.

[0113] Example 5 The raw colloidal silica is colloidal silica (BET specific surface area 330m 2 / g, silanol group density 10.3 / nm 2 A modification treatment was performed by contacting the silica particle concentration (20 mass%) with 3-mercaptopropyltrimethoxysilane diluted 10 times by mass with methanol for 1 hour under conditions of pH 8.8 and 60.0°C so that the contact amount of 3-mercaptopropyltrimethoxysilane was 340.00 μmol per 1 g of colloidal silica (silica particles in the raw colloidal particles) calculated as solid content. Next, 35% by mass hydrogen peroxide solution in an amount equivalent to 4.00 mol of hydrogen peroxide per 1 mol of the contact amount of the 3-mercaptopropyltrimethoxysilane was added to the contact and modified product of the colloidal silica and 3-mercaptopropyltrimethoxysilane, and the mixture was heated at 100.0°C for 20 hours. Thereafter, the mixture was cooled to room temperature to obtain the desired sulfonic acid-modified colloidal silica. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (% by mass), the average primary particle size of the silica particles, the average secondary particle size of the silica particles, the content (pieces / mL) of coarse particles with a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1% by mass, the metal impurity content (ppm by mass), and the pH were determined in the same manner as in Example 1. The results are shown in Table 2.

[0114] Example 6 The raw colloidal silica is colloidal silica (BET specific surface area 384 m 2 / g, silanol group density 13.5 / nm 2 A modification treatment was performed by contacting the silica particle concentration (20 mass%) with 3-mercaptopropyltrimethoxysilane diluted 10 times by mass with methanol for 1 hour under conditions of pH 9.5 and 60.0°C so that the contact amount of 3-mercaptopropyltrimethoxysilane was 370.00 μmol per 1 g of colloidal silica (silica particles in the raw colloidal particles) calculated as solid content. Next, 35% by mass hydrogen peroxide solution in an amount equivalent to 4.00 mol of hydrogen peroxide per 1 mol of the contact amount of the 3-mercaptopropyltrimethoxysilane was added to the contact and modified product of the colloidal silica and 3-mercaptopropyltrimethoxysilane, and the mixture was heated at 100.0°C for 20 hours. Thereafter, the mixture was cooled to room temperature to obtain the desired sulfonic acid-modified colloidal silica. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (% by mass), the average primary particle size of the silica particles, the average secondary particle size of the silica particles, the content (pieces / mL) of coarse particles with a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1% by mass, the metal impurity content (ppm by mass), and the pH were determined in the same manner as in Example 1. The results are shown in Table 2.

[0115] Comparative Example 1 The raw colloidal silica is colloidal silica (BET specific surface area 172 m 2 / g, silanol group density 5.5 / nm 2 A modification treatment was performed by contacting the silica particle concentration (20 mass%) with 3-mercaptopropyltrimethoxysilane diluted 10 times by mass with methanol for 1 hour under conditions of pH 9.7 and 60.0°C so that the contact amount of 3-mercaptopropyltrimethoxysilane was 250.00 μmol per 1 g of colloidal silica (silica particles in the raw colloidal particles) calculated as solid content. Next, 35% by mass hydrogen peroxide solution in an amount equivalent to 4.00 mol of hydrogen peroxide per 1 mol of the contact amount of the 3-mercaptopropyltrimethoxysilane was added to the contact and modified product of the colloidal silica and 3-mercaptopropyltrimethoxysilane, and the mixture was heated at 100.0°C for 20 hours. Thereafter, the mixture was cooled to room temperature to obtain the desired sulfonic acid-modified colloidal silica. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (% by mass), the average primary particle size of the silica particles, the average secondary particle size of the silica particles, the content (pieces / mL) of coarse particles with a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1% by mass, the metal impurity content (ppm by mass), and the pH were determined in the same manner as in Example 1. The results are shown in Table 2.

[0116] Comparative Example 2 The raw colloidal silica is colloidal silica (BET specific surface area 47m 2 / g, silanol group density 7.0 / nm 2 A modification treatment was performed by contacting the silica particle concentration (20 mass%) with 3-mercaptopropyltrimethoxysilane diluted 10 times by mass with methanol for 1 hour under conditions of pH 8.5 and 60.0°C so that the contact amount of 3-mercaptopropyltrimethoxysilane was 250.00 μmol per 1 g of colloidal silica (silica particles in the raw colloidal particles) calculated as solid content. Next, 35% by mass hydrogen peroxide solution in an amount equivalent to 4.00 mol of hydrogen peroxide per 1 mol of the contact amount of the 3-mercaptopropyltrimethoxysilane was added to the contact and modified product of the colloidal silica and 3-mercaptopropyltrimethoxysilane, and the mixture was heated at 100.0°C for 20 hours. Thereafter, the mixture was cooled to room temperature to obtain the desired sulfonic acid-modified colloidal silica. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (% by mass), the average primary particle size of the silica particles, the average secondary particle size of the silica particles, the content (pieces / mL) of coarse particles with a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1% by mass, the metal impurity content (ppm by mass), and the pH were determined in the same manner as in Example 1. The results are shown in Table 2.

[0117] Comparative Example 3 The raw colloidal silica is colloidal silica (BET specific surface area 170 m 2 / g, silanol group density 8.1 / nm 2 , silica particle concentration 20% by mass) and 3-mercaptopropyltrimethoxysilane diluted 10 times by mass with methanol were mixed so that the contact amount of the 3-mercaptopropyltrimethoxysilane was 95.00 μmol per 1 g of colloidal silica (silica particles in the raw colloidal particles) calculated as a solid content. The denaturation treatment was carried out by contacting the mixture at pH 10.8 and 60.0° C. for 1 hour. Next, 35% by mass hydrogen peroxide solution in an amount equivalent to 4.00 mol of hydrogen peroxide per 1 mol of the contact amount of the 3-mercaptopropyltrimethoxysilane was added to the contact and modified product of the colloidal silica and 3-mercaptopropyltrimethoxysilane, and the mixture was heated at 100.0°C for 20 hours. Thereafter, the mixture was cooled to room temperature to obtain the desired sulfonic acid-modified colloidal silica. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (% by mass), the average primary particle size of the silica particles, the average secondary particle size of the silica particles, the content (pieces / mL) of coarse particles with a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1% by mass, the metal impurity content (ppm by mass), and the pH were determined in the same manner as in Example 1. The results are shown in Table 2.

[0118] Comparative Example 4 The sulfonic acid-modified colloidal silica (40 g) obtained in Comparative Example 1 was further subjected to ultrafiltration using an ultrafiltration treatment device having the following configuration, thereby obtaining the desired sulfonic acid-modified colloidal silica. <Configuration of ultrafiltration treatment device> Filtration processing equipment: Asahi Kasei Corporation pencil-type module tabletop filtration unit (PX-02001) Ultrafiltration membrane: Ultrafiltration membrane with molecular weight cutoff of 80,000 (Asahi Kasei Corp. pencil-type module (AOP-0013)) Pumps: Masterflex L / S Easy-Load Pump Heads for Precision Tubing, Avantor (MFLX07514-10) and Masterflex L / S Analog Modular Drive Replacement Controllers, Avantor (MFLX07559―04) Tube: Masterflex silicone hydrolysis tube (99400-25) During the ultrafiltration process, ultrapure water was added to the sulfonic acid-modified colloidal silica to keep the amount of the sulfonic acid-modified colloidal silica constant. The amount of the liquid that passed through the ultrafiltration membrane was 220 g, and the time required for ultrafiltration was 150 minutes. The above production conditions are shown in Table 1. It was confirmed that the obtained sulfonic acid modified colloidal silica contained silica particles having sulfo groups fixed thereto, and that unreacted 3-mercaptopropyltrimethoxysilane remained in the solvent. Furthermore, for the obtained sulfonic acid-modified colloidal silica, the sulfur content (ppm by mass) per 1 g of silica particles, the sulfur content (ppm by mass) in the solvent per 1 g of solvent, the silica particle content (% by mass), the average primary particle size of the silica particles, the average secondary particle size of the silica particles, the content (pieces / mL) of coarse particles with a particle size of 0.2 μm or more contained in the silica particles when the silica particle concentration is 1% by mass, the metal impurity content (ppm by mass), and the pH were determined in the same manner as in Example 1. The results are shown in Table 2.

[0119] The sulfonic acid-modified colloidal silica obtained in each of the above Examples and Comparative Examples was used as an abrasive for polishing, and the polished surface roughness was evaluated by the following method. The results are shown in Table 2.

[0120] <Method for evaluating polished surface roughness> The sulfonic acid-modified colloidal silica obtained in each of the Examples and Comparative Examples was diluted with ultrapure water to a silica particle concentration of 3.0 mass % to prepare a polishing composition. Using the obtained polishing composition, a 3 cm square silicon wafer having a silicon oxide film formed on its surface was polished under the following conditions. (polishing conditions) Polishing machine: NF-300CMP, manufactured by Nanofactor Co., Ltd. Polishing pad: Nitta DuPont, IC1000TMPad Slurry supply rate: 50mL / min Head rotation speed: 32 rpm Platen rotation speed: 32 rpm Grinding pressure: 4psi Polishing time: 2 min (Surface roughness measurement conditions) After polishing, the surface roughness of the polished surface of the wafer was measured using an atomic force microscope under the following conditions. Atomic force microscope: Shimadzu Corporation SPM-9700HT Cantilever: OLYMPUS MICRO CANTILEVER OMCL-AC240TS-R3 Observation mode: Dynamic Scanning range: 3.0μm square Scanning speed: 1.00Hz Number of observation fields: Five arbitrary fields were observed per polished wafer (observation area per field: 3 μm × 3 μm). The root mean square roughness x of each of the five observation fields (five fields) on the polished surface of the wafer was i (nm) was measured and the root mean square roughness x i The arithmetic mean value of (nm) was taken as the polished surface roughness Rms (nm). JPEG0007678242000001.jpg26140When the polished surface roughness is measured using the above method, if the polished surface roughness is 1.0 nm or less, the polishability is judged to be good, and if the polished surface roughness exceeds 1.0 nm, the polishability is judged to be poor.

[0121] [Table 1]

[0122] [Table 2]

[0123] As shown in Table 1, in Examples 1 to 6, the method for producing sulfonic acid-modified colloidal silica was as follows: (i) a colloidal silica having a BET specific surface area of ​​70 to 500 m 2 / g and silanol group density is 7.0 to 20.0 / nm 2and then contacting hydrogen peroxide to oxidize the mercapto groups introduced on the surface of the silica particles to convert them to sulfo groups; (ii) the amount of the mercapto group-containing silane coupling agent contacted is 100.00 μmol or more and 400.00 μmol or less per 1 g of the raw colloidal silica calculated as a solid content; (iii) when the mercapto group-containing silane coupling agent is contacted with the raw colloidal silica, the silane coupling agent is diluted with methanol to a dilution ratio of 3 to 50; (iv) the amount of the hydrogen peroxide added is 3.50 to 10.00 mol per 1 mol of the mercapto group-containing silane coupling agent contacted; and (v) after contacting the hydrogen peroxide, the mixture obtained is heated at a temperature of 80.0° C. or more for 15 hours or more.

[0124] Therefore, from Table 2, it can be seen that the sulfonic acid modified colloidal silica obtained in Examples 1 to 6 has a sulfur content in the silica particles of 3000 ppm by mass or more and 9000 ppm by mass or less per 1 g of silica particles, a sulfur content in the solvent of 750 ppm by mass or less per 1 g of solvent, and a content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles of 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass, and is capable of forming a polished surface with highly reduced surface roughness even when used to polish semiconductor wafers.

[0125] On the other hand, from Table 1, it can be seen that in Comparative Examples 1 to 4, in the method for producing sulfonic acid-modified colloidal silica, (i) the raw material colloidal silica used was one having a BET specific surface area outside the specified range (Comparative Example 2) or one having a silanol group density outside the specified range (Comparative Example 1 and Comparative Example 4), or the contact amount of the mercapto group-containing silane coupling agent per 1 g of the raw material colloidal silica converted into solid content was outside the specified range (Comparative Example 3).

[0126] For this reason, it can be seen from Table 2 that the sulfonic acid-modified colloidal silica obtained in Comparative Examples 1 to 4 has a sulfur content of silica particles per 1 g of silica particles outside the specified range (Comparative Example 3), a sulfur content in solvent per 1 g of solvent exceeding a specified value (Comparative Examples 1 and 2), or a content of coarse particles having a particle size of 0.2 μm or more contained in silica particles exceeding a specified value (Comparative Example 4), and when used as abrasive grains for polishing semiconductor wafers, a polished surface with significantly reduced surface roughness cannot be obtained (Comparative Examples 1 to 4). [Industrial Applicability]

[0127] According to the present invention, it is possible to provide a sulfonic acid modified colloidal silica capable of forming a polished surface with highly reduced surface roughness, and a method for producing the sulfonic acid modified colloidal silica.

Claims

1. A sulfonic acid modified colloidal silica, The sulfur content of the silica particles is 3000 ppm by mass or more and 9000 ppm by mass or less per 1 g of the silica particles, The sulfur content in the solvent is 750 ppm by mass or less per 1 g of the solvent; The content of coarse particles having a particle diameter of 0.2 μm or more contained in the silica particles is 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass.

1. A sulfonic acid-modified colloidal silica comprising:

2. A method for producing the sulfonic acid modified colloidal silica according to claim 1, comprising the steps of: (i) BET specific surface area is 70 to 500 m ２ / g and the silanol group density is 7.0 to 20.0 / nm ２ the step of contacting a raw material colloidal silica containing silica particles represented by the formula (I) with a silane coupling agent containing a mercapto group to carry out a modification treatment, and then contacting the raw material colloidal silica with hydrogen peroxide to oxidize the mercapto group introduced on the surface of the silica particles to convert it into a sulfo group, (ii) the contact amount of the silane coupling agent containing a mercapto group is 100.00 μmol or more and 400.00 μmol or less per 1 g of the raw material colloidal silica, calculated as a solid content, (iii) when the silane coupling agent containing a mercapto group is brought into contact with the raw material colloidal silica, the silane coupling agent is diluted with methanol to a dilution ratio of 3 to 50 times; (iv) the contact amount of the hydrogen peroxide is 3.50 to 10.00 mol per 1 mol of the contact amount of the silane coupling agent containing a mercapto group, (v) after contacting the hydrogen peroxide, heating the resulting mixture at a temperature of 80.0° C. or greater for 15 hours or more; 1. A method for producing sulfonic acid-modified colloidal silica, comprising the steps of:

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