Amino-modified colloidal silica and method for producing amino-modified colloidal silica

Abstract

Provided is an amino group-modified colloidal silica that suppresses the formation of aggregated particles, exhibits stable dispersibility for a long period of time, and is capable of forming a highly flat polished surface at a high speed even when used to polish semiconductor wafers. The amino-modified colloidal silica has a pH of 8.50 to 9.50, a Si concentration in a solvent of 150 mass ppm or less, and contains amino-modified silica particles in which the content of coarse particles having a particle size of 0.2 μm or more is 10,000,000 particles / mL or less when the silica particle concentration is 1 mass %.

Description

[Technical Field]

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

[0002] In the semiconductor manufacturing process, semiconductor wafers are held by 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 methods, 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 produce a polished surface with reduced surface roughness on the semiconductor wafer to be polished.

[0005] Under these circumstances, colloidal silica particles, that is, colloidal silica (silica sol), have come to be used as abrasive grains for polishing semiconductor wafers.

[0006] However, colloidal silica particles tend to aggregate to form aggregated particles, particularly when stored for a long period of time. Therefore, when used as an abrasive for polishing semiconductor wafers, the polished surface becomes rough, making it difficult to obtain a flat polished surface. For this reason, in order to suppress aggregation of silica particles and achieve stable dispersibility over a long period of time, amino group-modified colloidal silica has been proposed, in which colloidal silica is modified with an aminosilane coupling agent (a silane coupling agent having an amino group) (see Patent Document 1 (International Publication No. 2018 / 061656 pamphlet)). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 061656 Brochure DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0008] According to Patent Document 1, amino group-modified colloidal silica in which the formation of aggregated particles is suppressed can be obtained by producing the colloidal silica while maintaining a pH higher than the isoelectric point.

[0009] However, after extensive investigations, the present inventors have found that the amino group-modified colloidal silica obtained by the method described in Patent Document 1 contains a large amount of unreacted aminosilane coupling agent (used to modify the amino groups) remaining in the solvent. Further investigation by the present inventors revealed that when chemical mechanical polishing is performed using the amino group-modified colloidal silica obtained by the method described in Patent Document 1 as abrasive grains, it becomes difficult to obtain a sufficient polishing rate, possibly because the unreacted aminosilane coupling agent binds to the surface of the object to be polished and inhibits polishing.

[0010] Under these circumstances, an object of the present invention is to provide an amino group-modified colloidal silica that suppresses the formation of agglomerated particles, exhibits stable dispersibility over a long period of time, and is capable of forming a highly flat polished surface at a high speed even when used to polish semiconductor wafers, as well as a method for producing the same. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to solve the above technical problems, and have found that the above problems can be solved by amino-group-modified colloidal silica containing amino-group-modified silica particles having a pH of 8.50 to 9.50, a Si concentration in a solvent of 150 mass ppm or less, and a content of coarse particles having a particle size of 0.2 μm or more of 10,000,000 particles / mL or less when the silica particle concentration is 1 mass %, and that the amino-group-modified colloidal silica can be produced by a specific production method. Based on these findings, the present invention has been completed.

[0012] That is, the present invention is (1) pH is 8.50 to 9.50, The Si concentration in the solvent is 150 ppm by mass or less, Contains amino-modified silica particles in which the content of coarse particles with a particle size of 0.2 μm or more is 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass. an amino group-modified colloidal silica characterized by: (2) The amino group-modified colloidal silica according to (1) above, wherein the average secondary particle diameter of the amino group-modified silica particles is 10 to 150 nm. (3) A method for producing the amino group-modified colloidal silica described in (1) above, comprising the steps of: A contact liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion is (i) a first pH control step of adjusting the pH to 8.00 or less while maintaining the zeta potential at -20.0 mV or less; (ii) a second pH control step in which a base is added to the adjusted solution obtained in the first pH control step to adjust the pH to 8.50 to 9.50; Method for producing amino group-modified colloidal silica, characterized by carrying out the steps of This provides: [Effects of the Invention]

[0013] The present invention can provide an amino group-modified colloidal silica that suppresses the formation of aggregated particles and exhibits stable dispersibility over a long period of time, and that can form a highly flat polished surface at a high speed even when used to polish semiconductor wafers, as well as a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0014] First, the amino group-modified colloidal silica according to the present invention will be described. The amino group-modified colloidal silica according to the present invention is pH is 8.50 to 9.50, The Si concentration in the solvent is 150 ppm by mass or less, Contains amino-modified silica particles in which the content of coarse particles with a particle size of 0.2 μm or more is 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass. It is characterized by the following.

[0015] The amino group-modified colloidal silica according to the present invention is a colloidal silica in which amino groups are fixed to silica particles constituting the colloidal silica. It contains amino group-modified silica particles. The amino group-modified colloidal silica according to the present invention is suitably one containing amino group-modified silica particles in which an aminosilane compound (a silane compound having an amino group) is fixed to silica particles constituting colloidal silica by chemical bonding.

[0016] Examples of the aminosilane compound include various aminosilane coupling agents.

[0017] Examples of the aminosilane coupling agent include one or more selected from 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 4-amino-3,3-dimethylbutyltriethoxysilane, N-methylaminopropyltrimethoxysilane, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, 2-(4-pyridylethyl)triethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and the like, and one or more selected from 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane are suitable.

[0018] In the amino group-modified colloidal silica according to the present invention, by using the aminosilane coupling agent as the aminosilane compound, Si-O-Si bonds are formed with the colloidal silica through a hydrolysis reaction and a dehydration condensation reaction, and the surfaces of the silica particles constituting the colloidal silica can be modified with amino groups (amino groups can be fixed).

[0019] As described above, the amino group-modified colloidal silica constituting the amino group-modified colloidal silica according to the present invention is obtained by dispersing amino group-modified silica particles, which have amino groups (—NH) fixed to silica particles constituting colloidal silica, in a solvent, and therefore the amino group-modified silica particles have a basic structure derived from the silica particles constituting the colloidal silica.

[0020] In the present application, it has been confirmed by X-ray photoelectron spectroscopy (XPS) shown below that the amino group-modified colloidal silica contains amino group-modified silica particles modified with amino groups. The measurement sample is centrifuged at 77,000 G and 5°C for 90 minutes. The resulting precipitate is dried at 60°C for 12 hours, and then the resulting solid is crushed in a mortar with a pestle and dried at 60°C under reduced pressure of -0.1 MPa or less for 2 hours to prepare a dry powder. Using this dry powder, the presence or absence of amino 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

[0021] 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 then polymerizes (oligomerizes) 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 contains not only primary silica particles but also secondary silica particles formed by association of the primary silica particles, and these secondary silica particles are dispersed in the solvent together with the primary silica particles. The amino group-modified colloidal silica according to the present invention corresponds to the above colloidal silica containing amino group-modified silica particles in which amino groups are fixed to silica particles dispersed in the colloidal silica.

[0022] The average primary particle size of the amino group-modified silica particles contained in the amino group-modified colloidal silica according to the present invention (average diameter of the amino group-modified silica primary particles) is not particularly limited, but is preferably 5 nm or more and 120 nm or less.

[0023] The average primary particle size of the amino group-modified silica particles contained in the amino group-modified colloidal silica according to the present invention is preferably 120 nm or less, more preferably 110 nm or less, and even more preferably 100 nm or less.

[0024] When the average primary particle size of the amino group-modified silica particles contained in the amino group-modified colloidal silica according to the present invention is the above-mentioned value (upper limit value) or less, a polished surface with superior flatness can be formed when polishing is performed using the amino group-modified colloidal silica according to the present invention.

[0025] The average primary particle size of the amino group-modified silica particles contained in the amino group-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.

[0026] When the average primary particle size of the amino group-modified silica particles contained in the amino group-modified colloidal silica according to the present invention is equal to or greater than the above value (lower limit), particle aggregation is less likely to occur when polishing is performed using the amino group-modified colloidal silica according to the present invention, making it easier to form a polished surface with superior flatness.

[0027] In the present application, the average primary particle size of the amino group-modified silica particles contained in the amino group-modified colloidal silica refers to a value measured by the BET method described below. That is, first, the amino group-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. 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 diameter (nm) of amino group-modified silica particles is calculated using the following formula: Average primary particle diameter of amino group-modified silica particles (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 Based on this, the average primary particle size (nm) of the amino group-modified silica particles is calculated by the following formula: Average primary particle diameter of amino group-modified silica particles (nm) = 2727 / specific surface area (m 2 / g) It can be calculated by:

[0028] As described above, the amino group-modified colloidal silica contains amino group-modified silica particles in which amino groups are fixed to silica particles constituting the colloidal silica. Therefore, in the present application, the average primary particle diameter of the amino group-modified silica particles contained in the amino group-modified colloidal silica (average diameter of the amino group-modified silica primary particles) is defined as the value calculated by the above method based on the true density of the silica particles, as described above.

[0029] The amino group-modified colloidal silica according to the present invention contains amino group-modified silica secondary particles formed by association of amino group-modified silica primary particles. The amino group-modified silica secondary particles contained in the amino group-modified colloidal silica according to the present invention, together with the amino group-modified silica primary particles contained in the amino group-modified colloidal silica according to the present invention, constitute the main particles of the amino group-modified silica particles, and are distinguished from the amino group-modified silica secondary particles and coarse particles (described below) formed by aggregation of the aminosilane coupling agent.

[0030] The average secondary particle diameter of the amino group-modified silica particles contained in the amino group-modified colloidal silica according to the present invention (average diameter of the amino group-modified silica secondary particles) is preferably 10 to 150 nm, more preferably 15 to 140 nm, and even more preferably 20 to 130 nm.

[0031] When the average secondary particle size of the amino group-modified silica particles contained in the amino group-modified colloidal silica according to the present invention is within the above-mentioned range, a polished surface with superior flatness can be formed when polishing is performed using the amino group-modified colloidal silica according to the present invention.

[0032] In the present application, the average secondary particle size of the amino group-modified silica particles contained in the amino group-modified colloidal silica refers to a value measured by the dynamic light scattering method described below. That is, first, a 0.3 mass % citric acid aqueous solution is added to the amino group-modified colloidal silica to be used as a measurement sample, and the mixture is uniformly diluted to a silica particle concentration of 0.8 mass %, and the resulting diluted solution is used as the measurement sample. The average particle size measured by dynamic light scattering using the above measurement sample and the zeta potential, particle size, and molecular weight measurement system "ELSZ-2000S" manufactured by Otsuka Electronics Co., Ltd. is taken as the average secondary particle size of the amino group-modified silica particles.

[0033] In the amino group-modified colloidal silica according to the present invention, the rate of increase in the average secondary particle size of the amino group-modified silica particles constituting the amino group-modified colloidal silica is preferably 5.0% or less, more preferably 4.5% or less, and even more preferably 4.0% or less.

[0034] <Method for calculating the increase rate of average secondary particle size> The concentration of silica particles in the amino group-modified colloidal silica is adjusted to 10% by mass. The sample with the adjusted silica particle concentration is placed in a fluororesin container, sealed, and stored at 25°C for 48 hours. The average secondary particle size of the amino group-modified silica particles in the amino group-modified colloidal silica before and after storage of the sample is measured by the method described above, and the increase rate of the average secondary particle size is calculated by the following formula. Increase rate of average secondary particle size (%) = {(average secondary particle size of amino-modified silica particles after 48 hours of storage - average secondary particle size of amino-modified silica particles before storage) / average secondary particle size of amino-modified silica particles before storage} × 100

[0035] In the present application, the rate of increase in the average secondary particle size of the amino group-modified silica particles constituting the amino group-modified colloidal silica is an index of the tendency of the amino group-modified silica particles constituting the amino group-modified colloidal silica to aggregate. The amino group-modified colloidal silica according to the present invention has an increase rate of the average secondary particle diameter of the amino group-modified silica particles constituting the amino group-modified colloidal silica of not more than a predetermined value, and therefore can suppress aggregation of the amino group-modified silica particles constituting the amino group-modified colloidal silica and easily exhibit stable dispersibility over a long period of time.

[0036] In the amino group-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 amino group-modified 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 amino group-modified colloidal silica) is 1% by mass.

[0037] In the amino group-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 amino group-modified silica particles is equal to or less than the above value (upper limit) when the silica particle concentration in the amino group-modified colloidal silica is 1 mass %, so that when chemical mechanical polishing (CMP) is performed using the amino group-modified colloidal silica according to the present invention, roughness of the polished surface due to the presence of coarse particles can be suppressed, and a polished surface with high flatness can be easily formed.

[0038] In the amino group-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 amino group-modified silica particles is not particularly limited, but in the amino group-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 amino group-modified silica particles can be 1,000 particles / mL or more, and preferably 0 particles / mL or more, when the silica particle concentration is 1% by mass.

[0039] The amino group-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 chemical mechanical polishing (CMP) is performed using the amino group-modified colloidal silica according to the present invention, a highly flat polished surface can be easily formed at a high polishing rate.

[0040] In the present application, the content of coarse particles having a particle size of 0.2 μm or more contained in the amino group-modified silica particles constituting the amino group-modified colloidal silica refers to the 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 amino group-modified silica particles> Ultrapure water is added to the amino group-modified colloidal silica to be measured to dilute it so that the silica particle concentration becomes 1.0 mass %. The obtained 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

[0041] The pH of the amino group-modified colloidal silica according to the present invention is 8.50 to 9.50.

[0042] The pH of the amino group-modified colloidal silica according to the present invention is preferably 8.50 or higher, more preferably 8.52 or higher, and even more preferably 8.54 or higher. When the pH of the amino group-modified colloidal silica according to the present invention is at least the above value (lower limit), the dispersion stability of the amino group-modified silica particles constituting the amino group-modified colloidal silica according to the present invention is likely to be improved, and the amino group-modified silica particles are less likely to aggregate during storage of the amino group-modified colloidal silica according to the present invention or during polishing, making it possible to easily form a polished surface with high flatness when the amino group-modified colloidal silica according to the present invention is used as abrasive grains for polishing.

[0043] The pH of the amino group-modified colloidal silica according to the present invention is preferably 9.50 or less, more preferably 9.48 or less, and even more preferably 9.46 or less. When the pH of the amino group-modified colloidal silica according to the present invention is equal to or less than the above value (upper limit), the long-term dispersion stability of the amino group-modified silica particles is improved while suppressing their solubility, making it easier for the particles to exhibit excellent polishing properties when used as polishing abrasive grains, and making it possible to easily form a polished surface with high flatness.

[0044] 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.).

[0045] The content of the amino group-modified silica particles in the amino group-modified colloidal silica according to the present invention is not particularly limited, but is preferably from 1% by mass to 50% by mass.

[0046] The content of amino group-modified silica particles in the amino group-modified colloidal silica according to the present invention is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more.

[0047] When the content of amino group-modified silica particles in the amino group-modified colloidal silica according to the present invention is equal to or greater than the above value (lower limit), the polishing performance is further improved when the amino group-modified colloidal silica dispersion according to the present invention is used as abrasive grains for polishing.

[0048] The content of amino group-modified silica particles in the amino group-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 the amino group-modified silica particles in the amino group-modified colloidal silica according to the present invention is the above value (upper limit) or less, the dispersion stability of the amino group-modified silica particles can be further improved.

[0049] In the present application, the content of amino group-modified silica particles in the amino group-modified colloidal silica according to the present invention means a value measured by the following measurement method. That is, 10.0 g of amino group-modified colloidal silica was dried to solid on a hot plate at 150°C, and then heat-treated at 800°C for 1 hour to remove moisture. The amount of the resulting solid content was designated as Wg, and the value was calculated using the following formula: Content of amino group-modified silica particles in amino group-modified colloidal silica (mass%) = (W / 10.0) x 100 The content of the silica particles corresponds to the total content of amino group-modified silica primary particles, amino group-modified silica secondary particles, and coarse particles in the amino group-modified colloidal silica.

[0050] The amino group-modified colloidal silica according to the present invention has a Si concentration in the solvent of 150 mass ppm or less.

[0051] The amino group-modified colloidal silica according to the present invention has a Si concentration in the solvent of 150 ppm by mass or less, preferably 145 ppm by mass or less, more preferably 140 ppm by mass or less, and even more preferably 135 ppm by mass or less.

[0052] In the amino group-modified colloidal silica according to the present invention, the Si concentration in the solvent serves as an index of the amount of unreacted aminosilane coupling agent remaining in the solvent. In the amino group-modified colloidal silica according to the present invention, the Si concentration in the solvent is the above-mentioned value (upper limit value) or less, so that the amount of unreacted aminosilane coupling agent remaining in the solvent is limited, and the bonding reaction between the unreacted aminosilane coupling agent and the surface of the object to be polished can be suppressed. Therefore, when the amino group-modified colloidal silica according to the present invention is used as abrasive grains for polishing, a polished surface with high flatness can be formed at high speed while inhibiting polishing inhibition caused by unreacted aminosilane coupling agent.

[0053] In the amino group-modified colloidal silica according to the present invention, the lower limit of the Si concentration in the solvent is not particularly limited, and the lower the concentration the better; however, the content of the amino group-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.

[0054] As described above, the inventors have conducted research and found that when semiconductor wafers are polished using amino group-modified colloidal silica, unreacted aminosilane coupling agent used to modify the amino groups (-NH2) remains in the solvent, and this aminosilane coupling agent reacts with the semiconductor wafer surface, inhibiting the polishing process, making it difficult to obtain a sufficient polishing rate. In contrast, in the amino group-modified colloidal silica of the present invention, the Si concentration in the solvent is limited to a predetermined value or less, so that even when polishing semiconductor wafers, polishing can be performed at high speed to form a polished surface with high flatness.

[0055] In the present application, the Si concentration in the solvent of the amino group-modified colloidal silica means the silicon atom concentration calculated by the following method.

[0056] The amino group-modified colloidal silica to be measured is centrifuged at 77,000 G, 5°C, and for 90 minutes. The Si concentration (silicon atom concentration) in the resulting supernatant is measured using an inductively coupled plasma atomic emission spectrometry (ICP-AES) device (IRIS intrepid II manufactured by Thermo Fisher Scientific) using the absolute calibration curve method.

[0057] The presence of the aminosilane coupling agent remaining in the solvent of the amino group-modified colloidal silica according to the present invention can be confirmed by liquid chromatography mass spectrometry (LC-MS).

[0058] The amino group-modified colloidal silica according to the present invention may contain metal impurities.

[0059] In the amino group-modified colloidal silica according to the present invention, the metal impurities can be one or more selected from sodium, potassium, iron, aluminum, calcium, magnesium, titanium, nickel, chromium, copper, zinc, lead, silver, manganese, cobalt, and the like.

[0060] In the amino group-modified colloidal silica according to the present invention, the total content of metal impurities is preferably 1 ppm by mass or less. By keeping the total content of metal impurities at 1 mass ppm or less, the amino group-modified colloidal silica according to the present invention can be suitably used as abrasive grains for polishing electronic materials such as semiconductor wafers.

[0061] In the present application, the content of metal impurities means a value measured using an atomic absorption spectrometer.

[0062] The amino group-modified colloidal silica according to the present invention can be suitably prepared by the production method according to the present application described below.

[0063] According to the present invention, it is possible to provide an amino group-modified colloidal silica that suppresses the formation of aggregated particles, exhibits stable dispersibility for a long period of time, and is capable of forming a highly flat polished surface at a high speed even when used to polish semiconductor wafers.

[0064] Next, a method for producing the amino group-modified colloidal silica according to the present invention will be described. The method for producing amino group-modified colloidal silica according to the present invention comprises the steps of: The method for producing amino group-modified colloidal silica according to the present invention comprises the steps of: A contact liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion is (i) a first pH control step of adjusting the pH to 8.00 or less while maintaining the zeta potential at -20.0 mV or less; (ii) a second pH control step in which a base is added to the adjusted solution obtained in the first pH control step to adjust the pH to 8.50 to 9.50.

[0065] <Contact liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion> In the method for producing amino group-modified colloidal silica according to the present invention, the colloidal silica used as the raw material (raw colloidal silica) can be appropriately selected from colloidal silica having desired properties produced by a known production method, and examples thereof include colloidal silica having desired properties produced by a sol-gel method.

[0066] In the method for producing amino group-modified colloidal silica according to the present invention, colloidal silica used as a raw material is preferably produced by a sol-gel method, since it contains a small amount of metal impurities that can diffuse into semiconductors and corrosive ions such as chloride ions.

[0067] In the method for producing amino group-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-condensation reaction using one or more hydrolyzable silicon compounds (e.g., alkoxysilanes or derivatives thereof) as raw materials.

[0068] 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 tetraalkoxysilanes represented by the following formula:

[0069] In the silicon compound represented by general formula (1) or a derivative thereof, the R group is an alkyl group having 1 to 8 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms.

[0070] In the silicon compound represented by general formula (1) or a derivative thereof, 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.

[0071] The silicon compound represented by the general formula (1) is preferably 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. Furthermore, examples of the derivatives of the silicon compound represented by general formula (1) include low condensates obtained by partially hydrolyzing the silicon compound represented by general formula (1) (tetraalkoxysilane). As the silicon compound represented by general formula (1) or its derivative, tetramethoxysilane is preferred because the hydrolysis rate can be easily controlled, fine silica particles can be easily obtained, and there is little residual unreacted material.

[0072] The silicon compound represented by the general formula (1) or its derivative undergoes hydrolysis and condensation in a reaction solvent to form colloidal silica.

[0073] Examples of the dispersion solvent (reaction solvent) used when the silicon compound represented by 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).

[0074] 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 general formula (1) or its derivative. If 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), and if it exceeds 50 moles per mole of the silicon compound represented by general formula (1) or its derivative, the production efficiency may decrease.

[0075] The amount of water to be added to the silicon compound represented by general formula (1) or its derivative is not particularly limited as long as it is the amount required for hydrolysis of the silicon compound represented by general formula (1), and is preferably about 2 to 200 moles per mole of the silicon compound represented by general formula (1) or its derivative. When an organic solvent containing water is added to the silicon compound represented by 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 that is 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.

[0076] The reaction solvent for the hydrolysis and condensation reaction of silicon compounds to obtain colloidal silica is preferably adjusted to alkaline in the presence of a basic catalyst. By the above adjustment, the pH of the reaction solvent is controlled to preferably more than 8.00 and not more than 11.00, more preferably not less than 8.50 and not more than 10.50, and colloidal silica can be rapidly formed.

[0077] From the viewpoint of preventing the incorporation 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, 3-ethoxypropylamine, ammonia, urea, ethanolamine, tetramethylammonium hydroxide, and the like.

[0078] To hydrolyze and condense a silicon compound in a reaction solvent, the silicon compound represented by general formula (1) or its derivative is added to a solvent containing water and stirred at a temperature generally between 0°C and 100°C, preferably between 0°C and 50°C.

[0079] 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 derivatives proceed. First, the silicon compound represented by general formula (1) or its derivatives undergoes dehydration condensation to form a dimer. This dimer then polymerizes (oligomerizes) to form spherical primary silica particles in the solvent, thereby obtaining colloidal silica in which the primary silica particles are dispersed in the solvent. The colloidal silica also contains secondary particles (secondary silica particles) formed by association of primary silica particles. Colloidal silica with a uniform silica particle size can be obtained by hydrolyzing and condensing silicon compounds while stirring them in a solvent containing water.

[0080] The colloidal silica obtained by the above hydrolysis-condensation reaction (sol-gel method) can be used as the raw material colloidal silica in the production method according to the present invention by adjusting the concentration appropriately.

[0081] In the method for producing amino group-modified colloidal silica according to the present invention, the colloidal silica as a raw material contains an aqueous medium as a solvent. The aqueous medium may be the dispersion solvent used in preparing the colloidal silica, or may be a medium added separately after preparing the colloidal silica as a raw material. The aqueous medium may be the same as the dispersion solvent used in preparing the colloidal silica.

[0082] In the method for producing amino group-modified colloidal silica according to the present invention, the colloidal silica used as a raw material preferably has a pH of more than 8.00 and not more than 11.00, more preferably not less than 8.50 and not more than 10.50.

[0083] In the method for producing amino group-modified colloidal silica according to the present invention, the colloidal silica used as the raw material preferably has an average secondary particle diameter of silica particles of 150 nm or less, more preferably 145 nm or less, and even more preferably 140 nm or less.

[0084] In the method for producing amino group-modified colloidal silica according to the present invention, since the average secondary particle diameter of the silica particles constituting the raw material colloidal silica is the above-mentioned value (upper limit value) or less, when polishing is performed using the amino group-modified colloidal silica obtained by the production method according to the present invention, a polished surface with superior flatness can be formed.

[0085] In the method for producing amino group-modified colloidal silica according to the present invention, the average secondary particle diameter of the silica particles constituting the raw material colloidal silica is preferably 10 nm or more, more preferably 12 nm or more, even more preferably 15 nm or more, and still more preferably 20 nm or more.

[0086] When the average secondary particle diameter of the silica particles constituting the colloidal silica is equal to or greater than the above value (lower limit), aggregation of the silica particles is less likely to occur when polishing is performed using the amino group-modified colloidal silica obtained by the production method according to the present invention, and therefore a polished surface with superior flatness can be formed.

[0087] In the present application, the average secondary particle size of the silica particles constituting the colloidal silica can be measured by the same method as the method for measuring the average secondary particle size of the silica particles in the amino group-modified colloidal silica described above.

[0088] In the method for producing amino group-modified colloidal silica according to the present invention, the colloidal silica used as a raw material preferably has a content of coarse particles having a particle size of 0.2 μm or more contained in silica particles of 1,000,000 particles / mL or less, more preferably 9,800,000 particles / mL or less, and even more preferably 9,600,000 particles / mL or less, when the silica particle concentration is 1% by mass.

[0089] In the amino group-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 constituting the raw material colloidal silica is equal to or less than the above value (upper limit) when the silica particle concentration is 1 mass %, so that when chemical mechanical polishing (CMP) is performed using the amino group-modified colloidal silica obtained by the production method according to the present invention, roughness of the polished surface due to the presence of coarse particles can be suppressed, and a polished surface with high flatness can be easily formed.

[0090] In the method for producing amino group-modified colloidal silica according to the present invention, there is no particular lower limit for the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles constituting the raw material colloidal silica. However, the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles constituting the colloidal silica can be 1,000 particles / mL or more, and preferably 0 particles / mL or more, when the silica particle concentration is 1% by mass.

[0091] In the present application, the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles constituting the raw material colloidal silica can be measured by a method similar to the method for measuring the content of coarse particles having a particle size of 0.2 μm or more contained in the amino group-modified silica particles constituting the amino group-modified colloidal silica described above.

[0092] In the method for producing amino group-modified colloidal silica according to the present invention, a contact liquid obtained by contacting the above-mentioned colloidal silica as a raw material with a dispersion of an aminosilane coupling agent is used.

[0093] In the method for producing the amino group-modified colloidal silica according to the present invention, the details of the amino silane coupling agent are as described in the description of the amino group-modified colloidal silica according to the present invention.

[0094] In the method for producing amino group-modified colloidal silica according to the present invention, the content of the aminosilane coupling agent in the aminosilane coupling agent dispersion is preferably 0.5 to 30.0 mass%, more preferably 1.0 to 28.0 mass%, and even more preferably 1.5 to 26.0 mass%.

[0095] In the method for producing amino group-modified colloidal silica according to the present invention, by ensuring that the content of the aminosilane coupling agent in the aminosilane coupling agent dispersion is within the above range, uneven distribution of the aminosilane coupling agent in the dispersion can be suppressed, and when the aminosilane coupling agent is brought into contact with colloidal silica, the aminosilane coupling agent can be highly miscible and: It can be brought into sufficient contact with the silica particles.

[0096] In the method for producing amino group-modified colloidal silica according to the present invention, the dispersion solvent (reaction solvent) used in the aminosilane coupling agent dispersion liquid may be water or an organic solvent 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.

[0097] The contact amount of the aminosilane coupling agent is preferably 5 μmol or more and 150 μmol or less, more preferably 10 μmol or more and 145 μmol or less, and even more preferably 15 μmol or more and 140 μmol or less, per 1 g of colloidal silica (per 1 g of silica particles contained in colloidal silica) converted into solid content.

[0098] In the method for producing amino group-modified colloidal silica according to the present invention, by ensuring that the contact amount of the aminosilane coupling agent is within the above range, the surfaces of the silica particles can be sufficiently cationized with amino groups, and amino group-modified colloidal silica that exhibits excellent performance when used as abrasive grains for polishing can be easily prepared.

[0099] In the method for producing amino group-modified colloidal silica according to the present invention, when the raw material colloidal silica is brought into contact with the aminosilane coupling agent dispersion, the contact is carried out at a temperature of 5°C to 60°C, preferably 6°C to 59°C, and more preferably 7°C to 58°C.

[0100] In the method for producing amino group-modified colloidal silica according to the present invention, by contacting the colloidal silica dispersion with the aminosilane coupling agent under the above-mentioned temperature conditions, it is possible to suppress the rapid progress of hydrolysis and condensation polymerization of the aminosilane coupling agent, and to easily suppress the generation of aggregated particles.

[0101] The contact time (reaction time) during the contact treatment is not particularly limited, but is preferably from 5 minutes to 3 hours, more preferably from 7 minutes to 2 hours, and even more preferably from 9 minutes to 1 hour. The pH at which the contact treatment is carried out is not particularly limited, but a pH of 7.00 or higher and 11.00 or lower is preferred.

[0102] In the method for producing amino group-modified colloidal silica according to the present invention, the method for bringing colloidal silica into contact with the aminosilane coupling agent dispersion is not particularly limited, and examples thereof include a method in which the aminosilane coupling agent dispersion is added dropwise to the colloidal silica.

[0103] In the method for producing amino group-modified colloidal silica according to the present invention, the colloidal silica and the aminosilane coupling agent dispersion are The contact liquid obtained by contacting the above has a pH of usually 8.10 to 11.00, suitably 8.30 to 10.50, and more suitably 8.50 to 10.00.

[0104] <First pH control step> In the method for producing amino group-modified colloidal silica according to the present invention, the contact liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion is subjected to (i) a first pH control step of adjusting the pH to 8.00 or less while maintaining the zeta potential at −20.0 mV or less.

[0105] In the method for producing amino group-modified colloidal silica according to the present invention, in the first pH control step, the pH of the contact liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion is adjusted to 8.00 or less, preferably 7.96 or less, and more preferably 7.92 or less.

[0106] In the method for producing amino group-modified colloidal silica according to the present invention, in the first pH control step, the pH of the contact liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion is adjusted to the above-mentioned value (upper limit) or less. In the method for producing amino group-modified colloidal silica according to the present invention, the colloidal silica and the aminosilane coupling agent dispersion are The contact liquid obtained by contacting the above usually has a pH of more than 8.00, and therefore the first pH control step corresponds to a step of lowering the pH of the contact liquid to a predetermined range. In the method for producing amino group-modified colloidal silica according to the present invention, by adjusting the pH of the contact liquid as described above in the first pH control step, the solubility of the aminosilane coupling agent in the contact liquid can be suppressed (the solubility of the aminosilane coupling agent in the solvent can be reduced), and the reactivity of the aminosilane coupling agent with the silica particles that constitute the colloidal silica can be improved. As a result, the amount of aminosilane coupling agent remaining in the solvent can be reduced, and even when the resulting amino group-modified colloidal silica is used as a polishing abrasive, polishing inhibition caused by bonding between unreacted aminosilane coupling agent remaining in the solvent and the surface of the object to be polished can be effectively suppressed.

[0107] In the method for producing amino group-modified colloidal silica according to the present invention, the pH of the contact liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion in the first pH control step is adjusted while maintaining the zeta potential at −20.0 mV or less, preferably −20.2 mV or less, and more preferably −20.4 mV or less.

[0108] Zeta potential is the potential difference that occurs at the interface between a solid and a liquid when they are in contact with each other and undergo relative movement.As the absolute value of the zeta potential increases, the repulsion between particles becomes stronger and the stability of the particles increases.The closer the absolute value of the zeta potential is to zero, the more likely the particles are to aggregate. In the method for producing amino group-modified colloidal silica according to the present invention, by controlling the zeta potential as described above in the first pH control step, it is possible to improve the dispersion stability of the amino group-modified silica particles constituting the amino group-modified colloidal silica and effectively suppress their aggregation.

[0109] In the method for producing amino group-modified colloidal silica according to the present invention, If the pH of the contact liquid is adjusted too low in the first pH control step, the dispersion stability of the amino group-modified silica particles constituting the amino group-modified colloidal silica will decrease, making it difficult to suppress their aggregation. In the method for producing amino group-modified colloidal silica according to the present invention, instead of specifying the lower limit of the pH of the adjusted solution obtained in the first pH control step, the zeta potential in the first pH control step is specified as described above, thereby The dispersion stability of the amino group-modified silica particles in the contact liquid can be easily maintained.

[0110] In this application, the zeta potential refers to the value measured by diluting a measurement sample with a 10 mM aqueous sodium chloride solution so that the silica particle concentration in the measurement sample becomes 1% by mass, and measuring the resulting diluted solution using a zeta potential / particle size / molecular weight measurement system (ELS-Z manufactured by Otsuka Electronics Co., Ltd.).

[0111] In the method for producing amino group-modified colloidal silica according to the present invention, the method for controlling the pH in the first pH control step is not particularly limited. As described above, in the method for producing amino group-modified colloidal silica according to the present invention, the contact liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion usually has a pH of more than 8.0, and often contains a dispersant such as alcohol in addition to water. Therefore, one method for adjusting the pH is to replace the dispersant such as alcohol in the obtained reaction liquid with water.

[0112] The method for replacing the dispersion medium with water is not particularly limited, and examples thereof include a method in which a reaction liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion is heated, and water is added dropwise in a fixed amount while distilling off the dispersion medium such as alcohol.

[0113] <Second pH control step> In the method for producing amino group-modified colloidal silica according to the present invention, (ii) a second pH control step is carried out in which a base is added to the adjusted solution obtained in the first pH control step to adjust the pH to 8.50 to 9.50.

[0114] In the method for producing amino group-modified colloidal silica according to the present invention, in the second pH control step, a base is added to the adjusted solution obtained in the first pH control step to adjust the pH to 8.50 to 9.50, preferably 8.52 to 9.48, and more preferably 8.54 to 9.46.

[0115] In the method for producing amino group-modified colloidal silica according to the present invention, the base used in the second pH control step is preferably at least one selected from organic amines and ammonia, from the viewpoint of preventing the incorporation of impurities, and more preferably at least one selected from ethylenediamine, diethylenetriamine, triethylenetetraamine, ammonia, urea, ethanolamine, tetramethylammonium hydroxide, and the like.

[0116] In the method for producing amino group-modified colloidal silica according to the present invention, in the second pH control step, a base is added to the adjusted solution obtained in the first pH control step to raise the pH to 8.50 to 9.50, thereby improving the dispersion stability of the amino group-modified silica particles constituting the amino group-modified colloidal silica, and making it possible to easily improve the long-term storage stability while suppressing their aggregation.

[0117] Details of the amino group-modified colloidal silica obtained by the production method according to the present invention are as described above in the description of the amino group-modified colloidal silica according to the present invention.

[0118] The present invention can provide a method for producing amino group-modified colloidal silica that suppresses the formation of aggregated particles, exhibits stable dispersibility over a long period of time, and is capable of forming a highly flat polished surface at a high speed even when used to polish semiconductor wafers. [Example]

[0119] Next, the present invention will be explained in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples in any way.

[0120] Example 1 (1) Preparation process of colloidal silica (silica sol) A mother liquor (water concentration 17.4 mass %, ammonia concentration 0.97 mass %) was prepared by mixing 2253 g of pure water, 527 g of 28 mass % ammonia water, and 12391 g of methanol. Next, a raw material solution containing 1,522 g of tetramethoxysilane (TMOS) and 413 g of methanol was injected into the mother liquor at a constant rate over 25 minutes while maintaining the liquid temperature in the reaction system at 20°C, to prepare a silica sol reaction liquid with water and methanol as the dispersion medium. A portion of the obtained silica sol reaction liquid was placed in a flask under normal pressure, and the flask was heated to distill off the solvent, while the remainder of the silica sol reaction liquid was added dropwise to the flask, keeping the volume of the reaction liquid in the flask constant, to obtain a silica sol concentrated liquid (average secondary particle diameter of silica particles: 68 nm, pH 9.41) concentrated to a silica particle concentration of 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion A mixture of 14.4 g of methanol and 1.6 g of 3-aminopropyltrimethoxysilane (methanol concentration 90% by mass) was added dropwise to 800 g of the concentrated silica sol obtained in step (1) over 10 minutes while maintaining the liquid temperature at 30°C, thereby obtaining a reaction liquid (zeta potential -51.5 mV). That is, 1 part by mass of aminosilane coupling agent per 100 parts by mass of colloidal silica (per 100 parts by mass of silica particles contained in colloidal silica) converted to solid content was contacted under the above conditions to obtain a reaction liquid (pH 9.61). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 1,300 g of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction solution in the flask constant, to obtain a silica aqueous dispersion (pH 7.42, zeta potential -32.0 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 9.10. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.05, a Si concentration in the solvent of 87 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 68 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 7,754,231 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0121] Example 2 (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion The same treatment as in step (2) of Example 1 was carried out to obtain a reaction liquid (pH 9.61, zeta potential -51.5 mV). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 1,100 g of pure water was added dropwise to the flask, and the solvent was replaced with water while maintaining the volume of the reaction solution in the flask constant, thereby obtaining a silica aqueous dispersion (pH 7.92, zeta potential -41.2 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 9.05. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.03, a Si concentration in the solvent of 90 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 68 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 6,259,124 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0122] Example 3 (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion The same treatment as in step (2) of Example 1 was carried out to obtain a reaction liquid (pH 9.61, zeta potential -51.5 mV). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 1,800 g of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction solution in the flask constant, thereby obtaining a silica aqueous dispersion (pH 6.87, zeta potential -20.5 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 9.19. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.16, a Si concentration in the solvent of 84 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 67 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 8,238,512 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0123] Example 4 (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion The same treatment as in step (2) of Example 1 was carried out to obtain a reaction liquid (pH 9.61, zeta potential -51.5 mV). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 1,300 g of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction solution in the flask constant, thereby obtaining a silica aqueous dispersion (pH 7.54, zeta potential -30.5 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 8.62. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 8.61, a Si concentration in the solvent of 72 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 67 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 8,072,412 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0124] Example 5 (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion The same treatment as in step (2) of Example 1 was carried out to obtain a reaction liquid (pH 9.61, zeta potential -51.5 mV). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 1,300 g of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction solution in the flask constant, thereby obtaining a silica aqueous dispersion (pH 7.48, zeta potential -31.2 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 9.44. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.41, a Si concentration in the solvent of 115 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 69 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 5,489,239 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0125] Example 6 (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion A mixture of 14.4 g of methanol and 1.6 g of 3-aminopropyltriethoxysilane (methanol concentration 90% by mass) was added dropwise to 800 g of the concentrated silica sol obtained in step (1) over 10 minutes while maintaining the liquid temperature at 30°C, thereby obtaining a reaction liquid (zeta potential -53.2 mV). That is, 1 part by mass of aminosilane coupling agent per 100 parts by mass of colloidal silica (per 100 parts by mass of silica particles contained in colloidal silica) converted to solid content was contacted under the above conditions to obtain a reaction liquid (pH 9.53). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 1,300 g of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction solution in the flask constant, thereby obtaining a silica aqueous dispersion (pH 7.31, zeta potential -35.1 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 9.12. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.10, a Si concentration in the solvent of 80 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 68 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 6,817,240 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0126] Example 7 (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion A mixture of 14.4 g of methanol and 1.6 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (methanol concentration 90% by mass) was added dropwise to 800 g of the concentrated silica sol obtained in step (1) over 10 minutes while maintaining the liquid temperature at 30°C, thereby obtaining a reaction liquid (zeta potential -49.2 mV). That is, 1 part by mass of aminosilane coupling agent per 100 parts by mass of colloidal silica (per 100 parts by mass of silica particles contained in colloidal silica) converted to solid content was contacted under the above conditions to obtain a reaction liquid (pH 9.72). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 1,300 g of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction solution in the flask constant, thereby obtaining a silica aqueous dispersion (pH 7.51, zeta potential -28.7 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 9.08. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.04, a Si concentration in the solvent of 85 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 67 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 7,701,856 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0127] (Comparative Example 1) (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution was obtained in which the silica particle concentration was concentrated to 20 mass %. The resulting silica sol concentrate was then heated to remove the solvent, while pure water was added dropwise to the flask while maintaining the volume of the liquid in the flask constant. The addition of pure water was stopped when the temperature of the flask top reached 100°C or higher and the pH reached 8.00 or lower, yielding a silica sol with a silica particle concentration of 20% by mass (silica particles with an average secondary particle diameter of 68 nm and a pH of 7.72). (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion A mixture of 14.4 g of methanol and 1.6 g of 3-aminopropyltrimethoxysilane (methanol concentration 90% by mass) was added dropwise to 800 g of the silica sol obtained in step (1) over 10 minutes while maintaining the liquid temperature at 30°C, to obtain a reaction liquid (zeta potential -34.2 mV). That is, 1 part by mass of aminosilane coupling agent per 100 parts by mass of colloidal silica (per 100 parts by mass of silica particles contained in colloidal silica) converted to solid content was contacted under the above conditions to obtain a reaction liquid (pH 8.21). (3) pH control process The reaction solution obtained in step (2) was heated to 70°C, and then 28% by mass of aqueous ammonia was added to raise the pH to 9.37. The solution was then maintained at 70°C for 24 hours to obtain the desired product solution. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.35, a Si concentration in the solvent of 285 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 67 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 8,659,112 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0128] (Comparative Example 2) (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion The same treatment as in step (2) of Example 1 was carried out to obtain a reaction liquid (pH 9.61, zeta potential -51.5 mV). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 800 g of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction solution in the flask constant, thereby obtaining a silica aqueous dispersion (pH 8.58, zeta potential -44.5 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica aqueous dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 9.35. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.31, a Si concentration in the solvent of 185 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 69 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 7,681,922 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0129] (Comparative Example 3) (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion The same treatment as in step (2) of Example 1 was carried out to obtain a reaction liquid (pH 9.61, zeta potential -51.5 mV). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 2100 g of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction solution in the flask constant, thereby obtaining a silica aqueous dispersion (pH 6.32, zeta potential -7.8 mV). (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 9.29. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.26, a Si concentration in the solvent of 89 ppm by mass, an average secondary particle diameter of the amino group-modified silica particles of 72 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 43,456,912 particles / mL when the silica particle concentration was 1% by mass. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0130] Comparative Example 4 (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion The same treatment as in step (2) of Example 1 was carried out to obtain a reaction liquid (pH 9.61, zeta potential -51.5 mV). (3) First pH control step The reaction liquid obtained in step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 1,300 parts by mass of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction liquid in the flask constant, thereby obtaining a silica aqueous dispersion (pH 7.57, zeta potential -30.4 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 8.21. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 8.20, a Si concentration in the solvent of 65 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 71 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 29,105,261 particles / mL when the silica particle concentration was 1 mass%. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0131] (Comparative Example 5) (1) Preparation process of colloidal silica (silica sol) By carrying out the same treatment as in step (1) of Example 1, a concentrated silica sol solution (average secondary particle diameter of silica particles: 68 nm, pH 9.41) was obtained, in which the silica particle concentration was concentrated to 20 mass %. (2) Contacting colloidal silica (silica sol) with an aminosilane coupling agent dispersion The same treatment as in step (2) of Example 1 was carried out to obtain a reaction liquid (pH 9.61, zeta potential -51.5 mV). (3) First pH control step The reaction solution obtained in the step (2) was placed in a flask under normal pressure, and the flask was heated to distill off the solvent. 1,300 g of pure water was added dropwise to the flask, and the solvent was replaced with water while keeping the volume of the reaction solution in the flask constant, thereby obtaining a silica aqueous dispersion (pH 7.61, zeta potential -33.1 mV). Throughout the entire treatment process of replacing the solvent with water, the zeta potential in the reaction solution was maintained at -20.0 mV or less. (4) Second pH control step The silica water dispersion obtained in step (3) was cooled to 70°C, and then 28% by mass of ammonia water was added to raise the pH to 10.02. The liquid temperature was then maintained at 70°C for 24 hours to obtain the desired product liquid. The resulting product liquid was confirmed to contain silica particles having amino groups fixed to the surface, that is, to be amino group-modified colloidal silica. The amino group-modified colloidal silica had a pH of 9.98, a Si concentration in the solvent of 221 mass ppm, an average secondary particle diameter of the amino group-modified silica particles of 73 nm, and a content of coarse particles having a particle diameter of 0.2 μm or more contained in the amino group-modified silica particles of 38,120,412 particles / mL when the silica particle concentration was 1 mass %. The above production conditions are shown in Table 1, and the physical properties of the obtained amino group-modified colloidal silica are shown in Table 2.

[0132] The dispersion stability of the amino-modified silica particles constituting the amino-modified colloidal silica obtained in each of the above Examples and Comparative Examples was evaluated by the following method. The results are shown in Table 2. <Dispersion stability evaluation method> The rate of increase in the average secondary particle size of the amino group-modified silica particles in the amino group-modified colloidal silica obtained in each of the above Examples and Comparative Examples was calculated by the method described above. Furthermore, with regard to dispersion stability, if the increase rate of the average secondary particle diameter exceeds 5.0%, aggregation of the amino group-modified silica particles progresses and the dispersion stability is evaluated as poor, and if the increase rate of the secondary particle diameter is 5.0% or less, the dispersion stability of the amino group-modified silica particles is evaluated as good.

[0133] The amino group-modified colloidal silica obtained in each of the above Examples and Comparative Examples was used as abrasive grains for polishing, and the polished surface roughness was evaluated by the following method. The results are shown in Table 2.

[0134] <Method for evaluating polishing speed and polished surface roughness> The amino group-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 resulting 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: Nanofactor Co., Ltd., NF-300CMP Polishing pad: Nitta DuPont, IC1000TMPad Slurry supply rate: 50 mL / min Head rotation speed: 32 rpm Platen rotation speed: 32 rpm Grinding pressure: 4psi Polishing time: 2 min

[0135] (Method for measuring polishing rate) The film thickness of the silicon wafer before and after polishing under the above polishing conditions was measured using an optical interference film thickness measuring instrument (Ava Spec-2048 manufactured by Avantes), and the polishing rate was calculated from the difference between the measured values ​​and the polishing time. When the polishing rate is calculated using the above method, if the polishing rate is 70 Å / min or more, the polishing property is judged to be good. Abrasiveness was judged to be poor when it was less than 70 Å / min.

[0136] (Method of measuring surface roughness) After polishing under the above polishing conditions, the surface roughness of the polished surface of the silicon 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: 3.0 μm 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 i (nm) and calculate the root mean square roughness x in five fields of view using the following formula: i The arithmetic mean value of (nm) was taken as the polished surface roughness Rms (nm). JPEG0007761821000001.jpg25147When the polished surface roughness Rms was measured using the above method, the polishing properties were judged to be good if the polished surface roughness Rms was 10.0 nm or less, and poor if the polished surface roughness was more than 10.0 nm.

[0137] [Table 1]

[0138] [Table 2]

[0139] As shown in Table 1, in Examples 1 to 7, colloidal silica is contacted with an aminosilane coupling agent dispersion to obtain a contact liquid, which is then subjected to the following steps: (i) a first pH control step in which the pH is adjusted to 8.00 or less while maintaining the zeta potential at -20.0 mV or less; and (ii) a second pH control step in which a base is added to the adjusted liquid obtained in the first pH control step to adjust the pH to 8.50 to 9.50, thereby preparing amino group-modified colloidal silica.

[0140] Therefore, as shown in Table 2, the amino group-modified colloidal silica obtained in Examples 1 to 7 had a pH of 8.50 to 9.50, a Si concentration in the solvent of 150 mass ppm or less, and the content of coarse particles having a particle size of 0.2 μm or more contained in the amino group-modified silica particles was 10,000,000 particles / mL or less when the silica particle concentration was 1 mass %. In this case, as shown in Table 2, the amino group-modified colloidal silica obtained in Examples 1 to 7 exhibited a low rate of increase in the average secondary particle size of the amino group-modified silica particles, inhibited the formation of agglomerated particles, and exhibited stable dispersibility over a long period of time, and was also capable of forming a highly flat polished surface at high speed even when used to polish semiconductor wafers.

[0141] On the other hand, as can be seen from Table 1, in Comparative Examples 1 to 5, when preparing the amino group-modified colloidal silica, the first pH control step was not performed (Comparative Example 1), the pH and zeta potential in the first pH control step were outside the predetermined ranges (Comparative Examples 2 and 3), or the pH in the second pH control step was outside the predetermined ranges (Comparative Examples 4 and 5). Therefore, as shown in Table 2, the amino group-modified colloidal silica obtained in Comparative Examples 1 to 5 had a pH outside the predetermined range (Comparative Example 4 and Comparative Example 5), a Si concentration in the solvent exceeding a predetermined value (Comparative Example 1, Comparative Example 2, and Comparative Example 5), or the content of coarse particles with a particle size of 0.2 μm or more contained in the amino group-modified silica particles exceeded a predetermined value (Comparative Example 3 to Comparative Example 5). In this case, as shown in Table 2, the amino group-modified colloidal silica obtained in Comparative Examples 1 to 5 exhibited a high rate of increase in the average secondary particle size of the amino group-modified silica particles and were unable to exhibit stable dispersibility over a long period of time (Comparative Examples 4 and 5), and when used to polish semiconductor wafers, were unable to form a polished surface at high speed (Comparative Examples 1, 2, and 5), or were unable to form a polished surface with high flatness (Comparative Examples 3 to 5). [Industrial Applicability]

[0142] The present invention can provide an amino group-modified colloidal silica that suppresses the formation of aggregated particles and exhibits stable dispersibility over a long period of time, and that can form a highly flat polished surface at a high speed even when used to polish semiconductor wafers, as well as a method for producing the same.

Claims

1. pH is 8.50 to 9.50, The Si concentration in the solvent is 150 ppm by mass or less, The content of coarse particles having a particle size of 0.2 μm or more is 10,000,000 particles / mL or less when the silica particle concentration is 1% by mass.

1. An amino group-modified colloidal silica characterized by:

2. 2. The amino-modified colloidal silica according to claim 1, wherein the average secondary particle size of the amino-modified silica particles is 10 to 150 nm.

3. A method for producing the amino group-modified colloidal silica according to claim 1, comprising: A contact liquid obtained by contacting colloidal silica with an aminosilane coupling agent dispersion is (i) a first pH control step of adjusting the pH to 8.00 or less while maintaining the zeta potential at −20.0 mV or less; (ii) a second pH control step of adding a base to the adjusted solution obtained in the first pH control step to adjust the pH to 8.50 to 9.50.

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