Method for manufacturing an abrasive composition

Abstract

To provide means capable of suppressing generation of coarse particles after adding a silane coupling agent comprising a cationic group, in a method of producing a polishing composition, including modifying silica using the silane coupling agent comprising the cationic group.SOLUTION: The method of producing a polishing composition includes mixing a liquid dispersion including silica with a solution including a silane coupling agent comprising a cationic group at a concentration of 0.03 mass% or more and less than 1 mass% to obtain a liquid dispersion including cation modified silica.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for producing an abrasive composition. [Background technology]

[0002] In semiconductor device manufacturing processes, as semiconductor device performance improves, technologies are needed to manufacture wiring at higher density and with greater integration. Chemical mechanical polishing (CMP) has become an essential process in such semiconductor device manufacturing processes. As semiconductor circuits become smaller, the required flatness of the pattern wafer surface increases, and it is necessary to achieve nano-order smoothness using CMP. To achieve high smoothness with CMP, it is preferable to polish the raised areas of the pattern wafer at a high polishing speed while minimizing polishing of the recessed areas.

[0003] In CMP (Chemical Polishing), it is common to use a composition (polishing composition) that contains various additives such as polishing accelerators and pH adjusters in addition to abrasive particles. Here, abrasive particles are particles that adhere to the surface of the object to be polished and have the function of removing that surface by physical action. When manufacturing polishing compositions, silica dispersions such as colloidal silica, which contain silica (silicon oxide; SiO2) particles that can become abrasive particles as a dispersed phase, are usually used as raw materials for the abrasive particles.

[0004] This silica dispersion is known to have poor stability under acidic conditions, as the silica particles aggregate together. Therefore, there has been a need for a silica dispersion that exhibits excellent stability across a wide pH range.

[0005] Examples of colloidal silica with improved stability include colloidal silica obtained by treating aqueous colloidal silica with an aqueous solution of basic aluminum chloride, and colloidal silica obtained by treating aqueous colloidal silica with an aqueous solution of basic aluminum salt and then stabilizing it with a water-soluble organoaliphatic polycarboxylic acid.

[0006] However, while these colloidal silica materials offered improved stability, they contained high levels of metal impurities, making them unsuitable for applications requiring high purity, such as abrasives used to polish semiconductor wafers.

[0007] As a technique to reduce the amount of such metal impurities, Patent Document 1 discloses a technique for producing modified colloidal silica by hydrolyzing colloidal silica produced by hydrolysis of a hydrolyzable silicon compound and then modifying it with a modifying agent such as a silane coupling agent. According to Patent Document 1, this method makes it possible to obtain modified colloidal silica that does not cause aggregation or gelation of colloidal silica, can be stably dispersed for a long period of time, and has an extremely low content of metal impurities and high purity. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2005-162533 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, when the inventors investigated the technology described in the above-mentioned patent document, they found that coarse particles may be generated after the addition of the silane coupling agent. When such coarse particles are generated, a problem arises in which the productivity of modified colloidal silica decreases.

[0010] Therefore, the present invention aims to provide a means for suppressing the generation of coarse particles after the addition of a silane coupling agent having a cationic group, in a method for producing an abrasive composition which includes modifying silica using a silane coupling agent having a cationic group. [Means for solving the problem]

[0011] To solve the above problems, the inventors diligently conducted research. As a result, they discovered that the above problems can be solved by a method for producing an abrasive composition, which involves mixing a dispersion containing silica with a solution containing a silane coupling agent having cationic groups at a concentration of 0.03% by mass or more and less than 1% by mass, to obtain a dispersion containing cationic-modified silica, and thus completed the present invention. [Effects of the Invention]

[0012] According to the present invention, a method for producing an abrasive composition, which includes modifying silica using a silane coupling agent having a cationic group, is provided, which can suppress the generation of coarse particles after the addition of the silane coupling agent having a cationic group. [Modes for carrying out the invention]

[0013] A method for producing an abrasive composition according to one embodiment of the present invention includes mixing a dispersion containing silica with a solution containing a silane coupling agent having cationic groups at a concentration of 0.03% by mass or more and less than 1% by mass to obtain a dispersion containing cationic-modified silica. According to the production method according to one embodiment of the present invention having such a configuration, the generation of coarse particles after the addition of the silane coupling agent having cationic groups can be suppressed. Furthermore, according to the production method according to one embodiment of the present invention, a cationic-modified silica aqueous dispersion with excellent filterability can be used, making it possible to use a fine-mesh filter when filtering the abrasive composition, which is advantageous in reducing the number of coarse particles in the abrasive composition.

[0014] The embodiments of the present invention will be described below. However, the present invention is not limited to the embodiments described below.

[0015] In this specification, unless otherwise specified, operations and measurements of physical properties shall be performed under conditions of room temperature (20°C to 25°C) and relative humidity of 40% RH to 50% RH.

[0016] Furthermore, in this specification, cationic-modified silica refers to a compound in which a cationic group (e.g., an amino group or a quaternary ammonium group) is bonded to the surface of silica (preferably colloidal silica). According to a preferred embodiment of the present invention, the cationic-modified silica is amino-group-modified silica, and more preferably amino-group-modified colloidal silica.

[0017] [Dispersion containing silica] In a manufacturing method according to one embodiment of the present invention, a dispersion containing silica (hereinafter also simply referred to as "silica dispersion") is used as a raw material. The silica contained in the silica dispersion is the raw material before it is cationically modified (modified) using a silane coupling agent having cationic groups, as described later.

[0018] The silica used as a raw material in this invention may be any of the following: natural crystalline silica, natural amorphous silica, synthetic crystalline silica, or synthetic amorphous silica. However, amorphous silica is preferred, and synthetic amorphous silica is more preferred. Silica may be used alone or in combination of two or more types. Furthermore, commercially available silica or synthetic silica may be used.

[0019] As a method for producing amorphous silica, for example, wet methods such as a method of neutralizing sodium silicate with a mineral acid (sodium silicate method), a method of hydrolyzing alkoxysilane (sol-gel method), etc.; a method of vaporizing silicon chloride and synthesizing silica particles by a gas-phase reaction in a high-temperature hydrogen flame (gas-phase method, gas combustion method), a dry method such as a method of heat-treating a mixed raw material composed of finely pulverized silica silica, a reducing agent such as metal silicon powder or carbon powder, and water for making a slurry at a high temperature in a reducing atmosphere to generate SiO gas, and cooling the SiO gas in an atmosphere containing oxygen (melting method), etc. are mentioned, and it is not particularly limited. However, from the viewpoint of reducing metal impurities, colloidal silica is preferable for amorphous silica, and colloidal silica produced by the sol-gel method is more preferable. Colloidal silica produced by the sol-gel method is preferable because the content of corrosive ions such as metal impurities diffusible in a semiconductor and chloride ions is small. The production of colloidal silica by the sol-gel method can be carried out using a conventionally known technique. Specifically, a hydrolyzable silicon compound (for example, alkoxysilane or its derivative) is used as a raw material, and a colloidal silica can be obtained by performing a hydrolysis / condensation reaction in water or a mixed solvent of water and an organic solvent. The obtained colloidal silica may be used as it is for mixing with a solution containing a cationic silane coupling agent, or may be diluted using a dispersion medium.

[0020] As the dispersion medium used for the silica dispersion liquid, water or a mixed solvent of water and an organic solvent is used. Examples of the organic solvent include hydrophilic organic solvents such as alcohols such as methanol, ethanol, isopropanol, n-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, 1,4-butanediol, and ketones such as acetone and methyl ethyl ketone. These organic solvents may be used alone or in combination of two or more. The mixing ratio of water and the organic solvent is not particularly limited and can be arbitrarily adjusted.

[0021] The silica contained in the silica dispersion usually exists in the form of secondary particles, which are aggregates of primary particles. The lower limit of the average particle diameter (average secondary particle diameter) of the secondary particles of silica is not particularly limited, but it is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. Further, the upper limit of the average secondary particle diameter is preferably 300 nm or less, more preferably 100 nm or less, and even more preferably 60 nm or less. That is, the average secondary particle diameter of silica is preferably 10 nm or more and 300 nm or less, more preferably 15 nm or more and 100 nm or less, and even more preferably 20 nm or more and 60 nm or less. If the average secondary particle diameter is 10 nm or more, sufficient dispersibility can be ensured even at a high concentration of silica. On the other hand, if the average secondary particle diameter is 300 nm or less, the generation of coarse particles is prevented. Note that as the value of the average secondary particle diameter, a value measured as the volume average particle diameter by the dynamic light scattering method can be adopted.

[0022] The lower limit of the average primary particle diameter of the silica contained in the silica dispersion is preferably 5 nm or more, more preferably 7 nm or more, and even more preferably 10 nm or more. Further, the upper limit of the average primary particle diameter of silica is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. That is, the average primary particle diameter of silica is preferably 5 nm or more and 100 nm or less, more preferably 7 nm or more and 50 nm or less, and even more preferably 10 nm or more and 30 nm or less. The average primary particle diameter of silica can be calculated using the formula SA = 4πR 2 (where R is the radius), assuming that the particle shape of silica is a perfect sphere, based on the specific surface area (SA) of silica. Note that there is no particular limitation on the value of the aggregation degree (average secondary particle diameter / average primary particle diameter) calculated from these values, and it is preferably about 1.0 or more and 5.0 or less.

[0023] The specific surface area of ​​silica contained in the silica dispersion is not particularly limited and can be appropriately selected according to the application of the cation-modified silica. The specific surface area is 10 m². 2 / g or more 600m 2 It is preferable that the amount be less than or equal to 15m 2 / g or more 300m 2 It is more preferable that it be less than or equal to / g, 20m 2 / g or more 200m 2 It is even more preferable that the specific surface area is less than or equal to / g. The value of the specific surface area can be the value calculated by the nitrogen adsorption method (BET method).

[0024] The lower limit of the silica concentration (content) in the silica dispersion is not particularly limited, but from the viewpoint of productivity, it is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more. Furthermore, the upper limit of the silica concentration (content) in the silica dispersion is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. In other words, the silica concentration (content) in the silica dispersion is preferably 5% by mass or more and 40% by mass or less, more preferably 8% by mass or more and 35% by mass or less, and even more preferably 10% by mass or more and 30% by mass or less.

[0025] The pH of the silica dispersion is not particularly limited, but is preferably 5.0 to 11.0, more preferably 6.0 to 10.5, and even more preferably 7.0 to 10.0.

[0026] Furthermore, if necessary, various treatment processes may be applied to the silica dispersion prepared above. Examples of such treatment processes include reducing the viscosity of the silica dispersion. For example, a process to reduce the viscosity of the silica dispersion may involve adding an alkaline solution (an aqueous solution of various bases such as ammonia water) or an organic solvent to the silica dispersion. In this case, there are no particular restrictions on the amount of alkaline solution or organic solvent added, and it should be set appropriately considering the viscosity of the silica dispersion obtained after the addition. By performing a process to reduce the viscosity of the silica dispersion in this way, there are advantages such as improving the initial dispersibility of the cationic silane coupling agent in the silica dispersion and suppressing the aggregation of silica particles.

[0027] [Silane coupling agent having a cationic group] As described above, to cationize silica (colloidal silica), a dispersion containing silica is mixed with a solution containing a silane coupling agent having a cationic group (e.g., an amino group or a quaternary ammonium group), and the mixture is reacted at a predetermined temperature for a predetermined time. In the following, the silane coupling agent having a cationic group will also be simply referred to as the "silane coupling agent," and the solution containing the silane coupling agent having a cationic group will also be simply referred to as the "silane coupling agent solution."

[0028] Examples of silane coupling agents used include, for example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltris(2-propoxy)silane, 3-aminopropyldimethoxymethylsilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropylethyldimethoxysilane, 3-aminopropyldimethylethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, and 3-(2-aminoethylamino)prop Triethoxysilane, 3-(2-aminoethylamino)propyldimethoxymethylsilane, 3-aminopropyldimethoxyethylsilane, trimethoxy[3-(methylamino)propyl]silane, trimethoxy[3-(phenylamino)propyl]silane, [3-(N,N-dimethylamino)propyl]trimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-( 2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltriisopropoxysilane, N-(2-aminoethyl)-3-aminoisobutyldimethylmethoxysilane, N-(2-aminoethyl)-3-aminoisobutylmethyldimethoxysilane, N-(2-aminoethyl)-11-aminoundecyltrimethoxysilane, N-2-(2-aminoethyl)aminoethyl-3-aminopropyltrimethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, N- Methyl-3-(triethoxysilyl)propan-1-amine, N-[3-(trimethoxysilyl)propyl]butane-1-amine, (aminoethylaminoethyl)phenyltriethoxysilane, methylbenzylaminoethylaminopropyltrimethoxysilane, benzylaminoethylaminopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, (aminoethylaminoethyl)phenethyltrimethoxysilane, (aminoethylaminomethyl)phenethyltrimethoxysilane,N-[2-[3-(trimethoxysilyl)propylamino]ethyl]ethylenediamine, trimethoxy[2-(2-aminoethyl)-3-aminopropyl]silane, diaminomethylmethyldiethoxysilane, methylaminomethylmethyldiethoxysilane, p-aminophenyltrimethoxysilane, N-methylaminopropyltriethoxysilane, N-methylaminopropylmethyldiethoxysilane, N-phenylaminomethyltrimethoxysilane, N-phenylaminomethyldimethoxymethylsilane, (phenylaminomethyl)trimethoxysilane, (phenylaminomethyl)methyldiethoxysilane, acetamidopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyl Examples include amino group-containing silanes such as trimethoxysilane, N-vinylbenzyl-3-aminopropyltriethoxysilane, N-cyclohexylaminomethyltriethoxysilane, N-cyclohexylaminomethyldiethoxymethylsilane, (2-aminoethyl)aminomethyltrimethoxysilane, (aminomethyl)dimethoxymethylsilane, (aminomethyl)trimethoxysilane, bis(3-trimethoxysilylpropyl)amine, and N,N'-bis[3-(trimethoxysilyl)propyl]ethylenediamine; and quaternary ammonium group-containing silanes such as octadecyldimethyl-(γ-trimethoxysilylpropyl)-ammonium chloride and N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride.

[0029] These silane coupling agents may be used individually or in combination of two or more. Furthermore, commercially available or synthetic silane coupling agents may be used.

[0030] Among the silane coupling agents listed above, at least one selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethoxymethylsilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3-(2-aminoethylamino)propyldimethoxymethylsilane, 3-aminopropyldimethoxyethylsilane, trimethoxy[3-(methylamino)propyl]silane, trimethoxy[3-(phenylamino)propyl]silane, [3-(N,N-dimethylamino)propyl]trimethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, N-methyl-3-(triethoxysilyl)propan-1-amine, N-[3-(trimethoxysilyl)propyl]butane-1-amine, and bis[(3-trimethoxysilyl)propyl]amine is preferred because it has high water solubility and allows for uniform modification treatment on the surface. The silane coupling agent is more preferably at least one selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethylamino)propyldimethoxymethylsilane, 3-aminopropyldimethoxyethylsilane, trimethoxy[3-(methylamino)propyl]silane, trimethoxy[3-(phenylamino)propyl]silane, [3-(N,N-dimethylamino)propyl]trimethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, N-methyl-3-(triethoxysilyl)propan-1-amine, N-[3-(trimethoxysilyl)propyl]butane-1-amine, and bis[(3-trimethoxysilyl)propyl]amine.

[0031] A silane coupling agent solution can be obtained by mixing and stirring a solvent with the silane coupling agent. The solvent used in the silane coupling agent solution is not particularly limited, as long as it can dissolve the silane coupling agent. Examples of solvents include water and organic solvents, as exemplified as dispersion media in the section on [dispersions containing silica] above.

[0032] In the manufacturing method according to the present invention, the concentration (content) of the silane coupling agent in the silane coupling agent solution is 0.03% by mass or more and less than 1% by mass. If the concentration (content) is less than 0.03% by mass, the surface modification effect cannot be sufficiently obtained. If the concentration (content) is 1% by mass or more, the amount of coarse particles increases, and the productivity of cation-modified silica decreases. The lower limit of the concentration (content) of the silane coupling agent in the silane coupling agent solution is preferably 0.04% by mass or more, and more preferably 0.05% by mass or more. The upper limit of the concentration (content) of the silane coupling agent in the silane coupling agent solution is preferably 0.8% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.3% by mass or less, and most preferably 0.15% by mass or less. In other words, the concentration (content) of the silane coupling agent in the silane coupling agent solution is preferably 0.04% by mass or more and 0.8% by mass or less, more preferably 0.05% by mass or more and 0.5% by mass or less, even more preferably 0.05% by mass or more and 0.3% by mass or less, and most preferably 0.05% by mass or more and 0.15% by mass or less.

[0033] [Mixing of silica-containing dispersion and silane coupling agent solution] The cation-modified silica according to this embodiment is obtained by mixing a dispersion containing the above-mentioned silica with a silane coupling agent solution having cationic groups. Specifically, through this mixing, the silica and the silane coupling agent having cationic groups react, introducing cationic groups as modifying groups onto the surface of the silica particles, thereby generating cation-modified silica, and obtaining a dispersion containing the cation-modified silica.

[0034] In the manufacturing method according to the present invention, the method of mixing the silica dispersion and the silane coupling agent solution is not particularly limited. For example, the silane coupling agent solution may be added to the silica dispersion, or the silica dispersion may be added to the silane coupling agent solution. Alternatively, the silica dispersion and the silane coupling agent solution may be added simultaneously. From the viewpoint of further suppressing the generation of coarse particles, the method of adding the solution containing the silane coupling agent to the silica dispersion is preferred. In this case, the silane coupling agent solution may be added all at once, in installments, or continuously. When adding continuously, the addition rate is appropriately adjusted according to the concentration of the silica dispersion, the concentration of the silane coupling agent solvent, etc. For example, if the total amount added is about 10 mL, the rate is 1 mL / min or more and 10 mL / min or less.

[0035] The mixing mass ratio of silica to the silane coupling agent having cationic groups (silica / silane coupling agent having cationic groups) is appropriately selected depending on the amount of cationic groups introduced, but is preferably 100 / 0.01 to 100 / 1, and more preferably 100 / 0.05 to 100 / 0.8. If the mixing mass ratio is within this range, the generation of coarse particles can be further suppressed.

[0036] The temperature of the silica dispersion and silane coupling agent solution during mixing is not particularly limited, but it is preferably in the range from room temperature to the boiling point of the solvent (dispersion medium). In this embodiment, since the reaction between silica and the silane coupling agent can proceed even at room temperature, it is preferable to carry out the reaction at a temperature near room temperature (for example, 20°C to 35°C). Even under conditions of a temperature near room temperature (for example, 20°C to 35°C), there is also the advantage that almost the entire amount of added silane coupling agent reacts with silica by the extremely simple operation of stirring the reaction system for several hours, leaving almost no unreacted silane coupling agent. In other words, in this embodiment, it is preferable not to include a step of heating the reaction system of the silica dispersion and the silane coupling agent solution.

[0037] The reaction time between silica and the silane coupling agent (the mixing time of the silica dispersion and the silane coupling agent solution) is not particularly limited, but is preferably 10 minutes or more and 10 hours or less, and more preferably 30 minutes or more and 5 hours or less. From the viewpoint of efficiently promoting the reaction, it is preferable to carry out the reaction while stirring the reaction system. There are no particular restrictions on the stirring means and stirring conditions used at this time, and conventionally known knowledge can be appropriately referred to. For example, from the viewpoint of uniformly dispersing the components, the stirring speed is usually 20 rpm (0.33 s -1 ) or more and 800 rpm (13.3 s -1 ) or less, and preferably 50 rpm (0.83 s -1 ) or more and 700 rpm (11.7 s -1 ) or less.

[0038] Regarding the pressure of the reaction system, it may be any of normal pressure (atmospheric pressure), increased pressure, or reduced pressure, and is not particularly limited. Since the reaction according to the present invention can proceed under normal pressure (atmospheric pressure), it is preferable to carry out the reaction under normal pressure (atmospheric pressure).

[0039] When the cation-modified silica obtained according to the above method contains a dispersion medium other than water, in order to enhance the long-term storage stability of the cation-modified silica, the dispersion medium other than water may be replaced with water as necessary. The method of replacing the dispersion medium other than water with water is not particularly limited, and examples include a method of dripping water in a certain amount while heating the cation-modified silica. Also, a method of separating the cation-modified silica from the dispersion medium other than water by precipitation / separation, centrifugation, etc. and then redispersing it in water can be mentioned.

[0040] The lower limit of the zeta potential of the obtained cation-modified silica is preferably 6 mV or higher, more preferably 8 mV, and even more preferably 10 mV or higher. The upper limit of the zeta potential of the obtained cation-modified silica is preferably 70 mV or lower, more preferably 60 mV or lower, and even more preferably 50 mV or lower. In other words, the zeta potential of the obtained cation-modified silica is preferably 6 mV to 70 mV, more preferably 8 mV to 60 mV, and even more preferably 10 mV to 50 mV. In this specification, the zeta potential of the cation-modified silica is the value measured by the method described in the examples. The zeta potential of the cation-modified silica can be adjusted by the amount of cationic groups present in the cation-modified silica, etc.

[0041] [Number of coarse particles] According to the manufacturing method of the present invention, the generation of coarse particles after the addition of a silane coupling agent having a cationic group can be suppressed. Specifically, the number of coarse particles with a particle diameter exceeding 0.7 μm per unit volume (1 mL) present in the cation-modified silica aqueous dispersion, as measured by the measurement method described below, is preferably 2,000,000 particles / mL or less, more preferably 1,000,000 particles / mL or less, even more preferably 500,000 particles / mL or less, even more preferably 100,000 particles / mL or less, particularly preferably 50,000 particles / mL or less, particularly more preferably 10,000 particles / mL or less, particularly more preferably 8,000 particles / mL or less, and most preferably 5,000 particles / mL or less.

[0042] (Method for measuring the number of coarse particles) A water dispersion was prepared by dispersing cation-modified silica at a concentration of 0.27% by mass in water and adjusting the pH to 4.0. The number of coarse particles with a particle size exceeding 0.7 μm per unit volume in the obtained cation-modified silica water dispersion was measured using a liquid particle counter. The details of the method for measuring the number of coarse particles are as described in the examples.

[0043] [Other processes] The method for producing the polishing composition according to the present invention may further include other steps, as long as they do not impede the effects of the present invention. Examples of such other steps include filtering a dispersion containing cation-modified silica, mixing a dispersion containing cation-modified silica with other additives (preferably pH adjusters), and further filtering a dispersion containing cation-modified silica after mixing with other additives. These steps will be described below.

[0044] <Process of filtering a dispersion containing cation-modified silica (first stage of filtration)> In this step, the dispersion containing the cation-modified silica obtained above is filtered. By performing this step, the number of coarse particles in the dispersion can be further reduced.

[0045] In the manufacturing method according to the present invention, the filtration process may consist of only one stage or may consist of two or more stages. The technical details described in this section apply to filtration when the filtration process consists of only one stage, and to the first stage of filtration when the filtration process consists of multiple stages. The technical details of the second and subsequent stages of filtration when the filtration process consists of multiple stages will be described later.

[0046] The media shape of the filter used in this process is not particularly limited, and filters with various structures, shapes, and functions can be used as appropriate. Specifically, it is preferable to use pleated, depth, depth-pleated, membrane, or adsorption type filters that have excellent filtration properties. The structure of the filter is not particularly limited and may be a bag-type or a hollow cylindrical cartridge type. Cartridge type filters may be gasket type or O-ring type. The filtration conditions (e.g., filtration differential pressure, filtration rate) should be set appropriately based on common technical knowledge in this field, taking into consideration the target quality and production efficiency.

[0047] From the viewpoint of improving yield, the mesh size (pore diameter) of the filter used in this process is preferably 0.05 μm or larger, more preferably 0.1 μm or larger, and even more preferably 0.2 μm or larger. Furthermore, from the viewpoint of enhancing the removal effect of foreign matter and aggregates, the mesh size (pore diameter) of the filter used in this process is preferably 100 μm or smaller, more preferably 30 μm or smaller, and even more preferably 20 μm or smaller.

[0048] In other words, the mesh opening (pore size) of the filter used in this process is preferably 0.05 μm to 100 μm, more preferably 0.1 μm to 30 μm, and even more preferably 0.2 μm to 20 μm.

[0049] The material of the filter used in this process is not particularly limited and includes, for example, cellulose, nylon, polysulfone, polyethersulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, glass, etc.

[0050] The filtration method is not particularly limited; for example, in addition to natural filtration at atmospheric pressure, known filtration methods such as suction filtration, pressure filtration, and centrifugal filtration can be appropriately employed.

[0051] The filters used in this process may be commercially available. Examples of commercially available filters include, for example, the Nuclipore membrane filter (manufactured by Whatman Corporation) and the HC series, BO series, SLF series, SRL series, and MPX series manufactured by Rokitechno Co., Ltd., which use polypropylene nonwoven fabric as a filter medium.

[0052] <Step of mixing in other additives> In this step, the dispersion containing the cation-modified silica obtained above is mixed with other additives. This step may be performed before or after the step of filtering the dispersion containing the cation-modified silica, but from the viewpoint of minimizing the introduction of foreign matter into subsequent steps, it is preferable to perform this step after filtering the dispersion containing the cation-modified silica.

[0053] Other examples of additives include pH adjusters, dispersion media, preservatives, rust inhibitors, antioxidants, stabilizers, and pH buffers, which can be components of polishing compositions. Here, we will explain pH adjusters.

[0054] (pH adjuster) The pH adjuster plays a role in adjusting the pH of the polishing composition according to the present invention to a desired value.

[0055] The pH adjusting agent is not particularly limited, and known pH adjusting agents used in the field of polishing compositions can be used. Among these, it is preferable to use known acids, bases, salts, amines, chelating agents, etc. Examples of pH adjusting agents include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, docosahexaenoic acid, eicosapentaenoic acid, lactic acid, malic acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, melitic acid, cinnamic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, aconitic acid, amino acids, anthracite Carboxylic acids such as nitrocarboxylic acids; sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, 10-camphorsulfonic acid, isethionic acid, and taurine; inorganic acids such as carbonic acid, hydrochloric acid, nitric acid, phosphoric acid, hypophosphorous acid, phosphorous acid, phosphonic acid, sulfuric acid, boric acid, hydrofluoric acid, orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, metaphosphoric acid, and hexametaphosphoric acid; alkali metal hydroxides such as potassium hydroxide (KOH); hydroxides of group 2 elements; ammonia; organic bases such as quaternary ammonium hydroxide; amines such as aliphatic amines and aromatic amines;N-methyl-D-glucamine, D-glucamine, N-ethyl-D-glucamine, N-propyl-D-glucamine, N-octyl-D-glucamine, N-acetyl-D-glucosamine, tris(hydroxymethyl)aminomethane, bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane, iminodiacetic acid, N-(2-acetamide)iminodiacetic acid, hydroxyethyliminodiacetic acid, N,N-di(2-hydroxyethyl)glycine, N-[tris(hydroxymethyl)methyl]glycine, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, N,N,N-trimethylenephosphonic acid, ethylenediamine-N,N,N',N'-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-dia Examples include minopropanetetraacetic acid, glycol etherdiaminetetraacetic acid, ethylenediamine orthohydroxyphenylacetic acid, ethylenediamine disuclic acid (SS form), N-(2-carboxylate ethyl)-L-aspartic acid, β-alanine diacetic acid, phosphonobutanetricarboxylic acid (2-phosphonobutane-1,2,4-tricarboxylic acid), hydroxyethylidenediphosphonic acid (HEDP) (1-hydroxyethylidene-1,1-diphosphonic acid), nitrilotrismethylenephosphonic acid, N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 1,2-dihydroxybenzene-4,6-disulfonic acid, polyamines, polyphosphonic acids, polyaminocarboxylic acids, polyaminophosphonic acids, chelating agents, or salts thereof. These pH adjusting agents may be used individually or in combination of two or more. Among these pH adjusting agents, strong acids with a relatively bulky structure, such as 10-camphor sulfonic acid, p-toluenesulfonic acid, and isethionic acid, are preferred from the viewpoint of suppressing the removal rate of silicon nitride and / or TEOS-type silicon oxide films.

[0056] The amount of pH adjuster added should be appropriately selected to achieve the desired pH value of the polishing composition.

[0057] Furthermore, the above-mentioned pH adjusting agent may be used not only to adjust the pH of the polishing composition, but also to adjust the pH of the dispersion containing cation-modified silica to a level suitable for storage. In other words, in addition to this step, a step of adding a pH adjusting agent to the dispersion containing cation-modified silica and storing it may be included. In this storage step, from the viewpoint of maintaining the dispersibility of the cation-modified silica after filtration, it is preferable to add the pH adjusting agent so that the pH of the dispersion becomes acidic during storage.

[0058] <Further filtering of the dispersion containing cation-modified silica (second and subsequent filtration stages)> In this step, the dispersion containing the cation-modified silica obtained above is further filtered. The technical details described in this section apply to the second and subsequent stages of filtration when the filtration process consists of multiple stages (two or more stages).

[0059] The media shape, structure, and material of the filter used in this process, as well as the filtration conditions and filtration method, can be the same as those described in the section above, "<Process for filtering a dispersion containing cation-modified silica (first stage filtration)>".

[0060] However, from an industrial standpoint, pleated, depth, and depth-pleated filter media shapes are preferred in terms of production efficiency. Furthermore, from the viewpoint of combining improved yield with improved removal of foreign matter and aggregates, it is preferable to use the above-mentioned pleated, depth, and depth-pleated filters in a multi-stage filtration process.

[0061] In this case, it is preferable that the mesh size (pore diameter) of the filter remains the same or gradually decreases from the earlier to the later stages in the multi-stage filtration process.

[0062] From the viewpoint of improving yield, the mesh size (pore diameter) of the filter used in this process is preferably 0.05 μm or larger, more preferably 0.1 μm or larger, and even more preferably 0.15 μm or larger. Furthermore, from the viewpoint of enhancing the removal effect of foreign matter and aggregates, the mesh size (pore diameter) of the filter used in this process is preferably 10 μm or smaller, more preferably 5 μm or smaller, even more preferably 1 μm or smaller, even more preferably 0.7 μm or smaller, and particularly preferably 0.4 μm or smaller. In other words, the mesh size (pore diameter) of the filter used in this process is preferably 0.05 μm or larger and 10 μm or smaller, more preferably 0.1 μm or larger and 5 μm or smaller, even more preferably 0.15 μm or larger and 1 μm or smaller, even more preferably 0.15 μm or larger and 0.7 μm or smaller, and particularly preferably 0.15 μm or larger and 0.4 μm or smaller.

[0063] Commercially available filters can also be used in this process. Examples of commercially available filters used in this process include, for example, UltiPleats® P-Nylon 66 and Ultipore® N66 manufactured by Nippon Pole Co., Ltd.

[0064] [Polishing composition] The polishing composition obtained by the above manufacturing method has a reduced number of coarse particles. That is, according to a preferred embodiment of the present invention, a polishing composition is provided which comprises cationic modified silica having a cationic group and a dispersion medium, wherein the cationic modified silica has a number of coarse particles with a particle diameter exceeding 0.7 μm, as measured by the following measurement method, of 500,000 particles / mL or less. The number of coarse particles in the polishing composition is preferably 100,000 particles / mL or less, more preferably 10,000 particles / mL or less, and even more preferably 5,000 particles / mL or less.

[0065] (Method for measuring the number of coarse particles) A water dispersion was prepared by dispersing cation-modified silica at a concentration of 0.27% by mass in water and adjusting the pH to 4.0. The number of coarse particles with a particle size exceeding 0.7 μm per unit volume in the obtained cation-modified silica water dispersion was measured using a liquid particle counter.

[0066] The dispersion media included in the polishing composition are similar to those listed in the section on [dispersions containing silica].

[0067] The cation-modified silica contained in the polishing composition according to this embodiment functions as an abrasive particle. The lower limit of the content of the cation-modified silica in the polishing composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.5% by mass or more, based on the total mass of the polishing composition. The upper limit of the content of the cation-modified silica in the polishing composition is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total mass of the polishing composition. In other words, the content of the cation-modified silica is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.2% by mass or more and 10% by mass or less, and even more preferably 0.5% by mass or more and 5% by mass or less, based on the total mass of the polishing composition.

[0068] The polishing composition according to this embodiment may further contain, as necessary, known additives that can be used in polishing compositions, such as pH adjusters, complexing agents, preservatives, and fungicides, to the extent that the effects of the present invention are not inhibited.

[0069] The polishing composition according to this embodiment is suitably used for polishing materials such as polysilicon, silicon nitride, silicon carbonitride (SiCN), silicon oxide, metals, and SiGe.

[0070] Examples of the object to be polished containing silicon oxide include, for example, a TEOS type silicon oxide surface (hereinafter, also simply referred to as "TEOS") generated using tetraethyl orthosilicate as a precursor, an HDP (High Density Plasma) film, an USG (Undoped Silicate Glass) film, a PSG (Phosphorus Silicate Glass) film, a BPSG (Boron-Phospho Silicate Glass) film, an RTO (Rapid Thermal Oxidation) film, and the like.

[0071] Examples of the above metal include tungsten, copper, aluminum, cobalt, hafnium, nickel, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, osmium, and the like.

Example

[0072] The present invention will be described in more detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. Unless otherwise specified, "%" and "parts" mean "mass%" and "parts by mass", respectively.

[0073] [Measurement methods for various physical properties] In this example, various physical properties were measured by the following methods.

[0074] [Measurement of particle size] The value of the average primary particle size of the silica used as a raw material was calculated using the formula SA = 4πR (where R is the radius) on the assumption that the shape of the silica is a true sphere, based on the specific surface area (SA) of the silica calculated by the BET method. 2 (R is the radius)

[0075] [Measurement of pH] The pH of various aqueous dispersions and aqueous solutions was confirmed using a pH meter (manufactured by Horiba, Ltd., model number: F-71).

[0076] [Production of cation-modified silica] (Example 1) In a 2L plastic jug, deionized water and synthetic amorphous silica (colloidal silica, average primary particle diameter of silica: 24 nm, average secondary particle diameter of silica: 47 nm, zeta potential: 5.5 mV) were mixed to obtain an aqueous dispersion (pH 7.5) with a final concentration of synthetic amorphous silica of 19.88% by mass.

[0077] Separately, 0.771 g of 3-aminopropyltriethoxysilane (APTES) and 231 g of deionized water were mixed to prepare an aqueous APTES solution (pH 7.0) with a concentration of 0.33% by mass.

[0078] While stirring 1000 g of an aqueous silica dispersion at 230 rpm, the entire amount of the APTES aqueous solution prepared above was added dropwise at a dropping rate of 12 mL / min. The mixture was then stirred at room temperature (25°C) for 50 minutes to obtain an aqueous dispersion of cation-modified (amino-modified) silica in which amino groups were introduced to the silica surface.

[0079] (Examples 2-3, 5-20, Comparative Examples 1-3) An aqueous dispersion of cation-modified silica was prepared in the same manner as in Example 1, except that the average primary particle size of the synthetic amorphous silica, the concentration of silica in the silica aqueous dispersion, the type and amount of silane coupling agent used, and the amount of water used when preparing the aqueous solution of the silane coupling agent were changed as shown in Table 1 below.

[0080] (Example 4) In a 2L plastic jug, 0.771g of 3-aminopropyltriethoxysilane (APTES) and 771g of deionized water were mixed to prepare a 0.10% by mass aqueous solution of APTES.

[0081] Separately, deionized water and synthetic amorphous silica (average primary particle diameter: 24 nm, average secondary particle diameter: 47 nm) were mixed to prepare an aqueous silica dispersion (pH 7.46) with a final synthetic amorphous silica concentration of 19.88% by mass.

[0082] While stirring the entire volume of the APTES aqueous solution prepared above at 230 rpm, 1000 g of the silica aqueous dispersion prepared above was added dropwise at a rate of 16 mL / min. The mixture was then stirred at room temperature (25°C) for 50 minutes to obtain an aqueous dispersion of cation-modified (amino-modified) silica in which amino groups were introduced to the silica surface.

[0083] The compositions of the silica aqueous dispersion and silane coupling agent aqueous solution used in each example and comparative example are shown in Table 1 below.

[0084] [Table 1]

[0085] [evaluation] <Measurement of Coarse Particle Number> As a sample, a water dispersion was used, prepared by dispersing cation-modified silica in deionized water to a concentration of 0.27% by mass, and then adjusting the pH to 4.0 using sulfuric acid.

[0086] The number of coarse particles larger than 0.7 μm per unit volume (1 mL) in the obtained cation-modified silica aqueous dispersion was measured using a liquid particle counter (LPC, Liquid Particle Counter, AccuSizer® FX (manufactured by Nippon Integris LLC)). The average value for n=3 was calculated and rounded to the nearest whole number.

[0087] <Measuring Zeta Potential> The zeta potential of the obtained cation-modified silica was measured using a zeta potential measuring device (product name "ELS-Z") manufactured by Otsuka Electronics Co., Ltd. As a sample, a water dispersion was used, in which cation-modified silica was dispersed in deionized water to a concentration of 1.8% by mass, and then the pH was adjusted to 3.0 using sulfuric acid.

[0088] <Filtration speed> The aqueous dispersions of cation-modified silica obtained in the above examples and comparative examples were subjected to suction filtration using a 47 mm diameter nuclepore membrane filter (manufactured by Whatman Corporation) with a pore size of 3.0 μm, and the filtration rate (amount filtered per unit time (1 minute)) was measured. The filtration rate is the average rate over a 5-minute filtration period.

[0089] The evaluation results are shown in Table 2 below. Note that blank spaces in Table 2 indicate that an evaluation has not yet been conducted.

[0090] [Table 2]

[0091] As is clear from Table 2 above, the zeta potential of the cation-modified silica in the aqueous dispersion obtained in the examples was higher than that of the synthetic amorphous silica used as the raw material. From this, it was found that the manufacturing method in the examples yields cation-modified silica in which cationic groups are bonded to the surface of synthetic amorphous silica.

[0092] The cation-modified silica aqueous dispersions of Comparative Examples 1 and 2 resulted in filter blockage during 5 minutes of filtration and also exhibited a low filtration rate. On the other hand, the cation-modified silica aqueous dispersion obtained in the Examples was found to have fewer coarse particles and superior filtration properties compared to the comparative examples. Therefore, using the cation-modified silica aqueous dispersion from the Examples, which has excellent filtration properties, in the production of polishing compositions allows for the use of finer filters, which is advantageous in reducing the number of coarse particles in the polishing compositions.

[0093] (Example 21, Comparative Example 4) The cation-modified silica aqueous dispersion obtained in Example 7 above was filtered using a 10 μm pore size filter (SLF type (depth type), manufactured by Rokitechno Co., Ltd.). After filtration, the cation-modified silica aqueous dispersion was dispersed in deionized water to a concentration of 5.4% by mass of cation-modified silica, and then the pH was adjusted to 4.0 using 10-camphor sulfonic acid. Furthermore, this cation-modified silica aqueous dispersion was filtered using a 0.2 μm pore size filter (Ultipore® N66 (pleated type), manufactured by Nippon Pall Co., Ltd.) to prepare the polishing composition (slurry) of Example 21.

[0094] Furthermore, the cation-modified silica aqueous dispersion obtained in Comparative Example 1 was filtered using a 10 μm pore size filter (SLF type (depth type), manufactured by Rokitechno Co., Ltd.). The filtered cation-modified silica aqueous dispersion was dispersed in deionized water so that the concentration of cation-modified silica was 5.4% by mass, and then the pH was adjusted to 4.0 using 10-camphor sulfonic acid. In addition, this cation-modified silica aqueous dispersion was filtered using a 3.0 μm pore size filter (SLF type (depth type), manufactured by Rokitechno Co., Ltd.) to prepare the polishing composition (slurry) of Comparative Example 4.

[0095] The number of coarse particles present in the polishing compositions of Example 21 and Comparative Example 4 was measured by LPC in the same manner as the measurement of the number of coarse particles described above.

[0096] [Table 3]

[0097] As is clear from Table 3 above, the polishing composition of Example 21, prepared using the cation-modified silica aqueous dispersion in the aqueous dispersion obtained in the Examples, had fewer coarse particles compared to Comparative Example 4. By performing polishing with a polishing composition that has fewer coarse particles, the occurrence of defects during polishing can be suppressed.

Claims

1. A method for producing an abrasive composition, comprising mixing a dispersion containing silica with a solution containing a solvent and a silane coupling agent having cationic groups at a concentration of 0.05% by mass or more and 0.5% by mass or less, to obtain a dispersion containing cationic-modified silica, The solvent is water, or a mixed solvent of water and an organic solvent. The silane coupling agent having a cationic group is at least one selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethoxymethylsilane, and 3-aminopropyldiethoxymethylsilane. The silica concentration in the silica dispersion is 10% by mass or more and 30% by mass or less. A method for producing an abrasive composition, wherein the mixed mass ratio of silica to the silane coupling agent having a cationic group (silica / silane coupling agent having a cationic group) is 100 / 0.05 to 100 / 0.

8.

2. The manufacturing method according to claim 1, wherein the concentration of the silane coupling agent having a cationic group in the solution is 0.05% by mass or more and 0.33% by mass or less.

3. The manufacturing method according to claim 1 or 2, wherein the concentration of the silane coupling agent having a cationic group in the solution is 0.05% by mass or more and 0.3% by mass or less.

4. The manufacturing method according to any one of claims 1 to 3, wherein the concentration of the silane coupling agent having a cationic group in the solution is 0.05% by mass or more and 0.15% by mass or less.

5. The manufacturing method according to any one of claims 1 to 4, wherein the mixing comprises adding a solution containing the silane coupling agent having a cationic group to the silica dispersion.

6. The manufacturing method according to any one of claims 1 to 5, wherein the silica is colloidal silica.

7. The manufacturing method according to any one of claims 1 to 6, further comprising filtering the dispersion containing the cation-modified silica.

8. The manufacturing method according to any one of claims 1 to 7, further comprising mixing the dispersion containing the cation-modified silica with a pH adjusting agent.

9. The manufacturing method according to any one of claims 1 to 8, wherein the number of coarse particles with a particle diameter exceeding 0.7 μm in the dispersion containing the cation-modified silica, as measured by the following measurement method, is 500,000 particles / mL or less: (Measurement method) After preparing an aqueous dispersion in which the cation-modified silica is dispersed in water at a concentration of 0.27% by mass and the pH is adjusted to 4.0, the number of coarse particles with a particle diameter exceeding 0.7 μm per unit volume (1 mL) in the obtained aqueous dispersion containing the cation-modified silica is measured using a liquid particle counter.

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