JP2022179329A - Method of producing polishing composition - Google Patents

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 The present invention relates to a method for producing a polishing composition.

2. Description of the Related Art In a semiconductor device manufacturing process, as the performance of semiconductor devices improves, a technique for manufacturing wiring with higher density and higher integration is required. CMP (Chemical Mechanical Polishing) is an essential process in the manufacturing process of such semiconductor devices. As the miniaturization of semiconductor circuits progresses, the flatness required for the unevenness of pattern wafers is high, and it is also required to achieve nano-order high smoothness by CMP. In order to achieve high smoothness by CMP, it is preferable to polish the convex portions of the pattern wafer at a high polishing rate while not polishing the concave portions so much.

Here, in CMP, it is common to use a composition (polishing composition) containing various additives such as a polishing accelerator and a pH adjuster in addition to a polishing agent called abrasive grains. Here, abrasive grains (abrasives) are particles that have the function of adhering to the surface of an object to be polished and scraping off the surface by physical action. And, as a raw material for abrasive grains (abrasive) when producing a polishing composition, colloidal silica, etc., in which silica (silicon oxide; SiO ₂ ) particles that can be used as abrasive grains (abrasive) are used as dispersoids. of silica dispersion is used.

This silica dispersion is known to be poor in stability due to aggregation of silica particles under acidic conditions, and there has been a demand for a silica dispersion excellent in stability over a wide pH range.

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 aqueous colloidal silica treated with an aqueous solution of basic aluminum salt, followed by addition of water-soluble organic aliphatic Colloidal silica stabilized with polycarboxylic acid has been known.

However, according to these colloidal silica, although the stability was improved, the content of metal impurities was large and, for example, like abrasive grains (abrasives) for polishing semiconductor wafers, etc., it was found to be of high purity. There was a problem that it could not be used for the required purpose.

As a technique for reducing the amount of such metal impurities mixed in, in Patent Document 1, colloidal silica produced by hydrolyzing a hydrolyzable silicon compound is modified using a modifier such as a silane coupling agent. Techniques for processing to produce modified colloidal silica have been disclosed. According to Patent Document 1, by such a method, colloidal silica does not aggregate or gel, can be stably dispersed for a long period of time, has an extremely low content of metal impurities, and has a high purity. Silica is said to be obtained.

JP-A-2005-162533

However, when the present inventors proceeded with the study of the technique described in the above patent document, it was found that coarse particles may be generated after the addition of the silane coupling agent. When such coarse particles are produced, there arises a problem that the productivity of the modified colloidal silica is lowered.

Therefore, the present invention provides a method for producing a polishing composition comprising modifying silica with a silane coupling agent having a cationic group, in which coarse particles are generated after addition of a silane coupling agent having a cationic group. It is an object of the present invention to provide means for suppressing

In order to solve the above problems, the present inventors have made extensive research. As a result, a dispersion containing silica and a solution containing a silane coupling agent having a cationic group at a concentration of 0.03% by mass or more and less than 1% by mass are mixed to obtain a dispersion containing cation-modified silica. The present inventors have found that the above problems can be solved by a method for producing a polishing composition, including obtaining a polishing composition, and have completed the present invention.

According to the present invention, in a method for producing a polishing composition comprising modifying silica with a silane coupling agent having a cationic group, coarse particles after addition of the silane coupling agent having a cationic group. Means are provided that can suppress the occurrence.

A method for producing a polishing composition according to one embodiment of the present invention includes a dispersion containing silica, and a solution containing a silane coupling agent having a cationic group at a concentration of 0.03% by mass or more and less than 1% by mass. to obtain a dispersion comprising cationically modified silica. According to the production method according to one embodiment of the present invention having such a configuration, generation of coarse particles after addition of the silane coupling agent having a cationic group can be suppressed. In addition, according to the production method according to one embodiment of the present invention, it is possible to use a cation-modified aqueous silica dispersion with excellent filterability, and when filtering the polishing composition, a fine filter is used. It is possible to use it, and it is advantageous for reducing the number of coarse particles in the polishing composition.

Embodiments of the present invention will be described below. In addition, the present invention is not limited only to the following embodiments.

In this specification, unless otherwise specified, operations and measurements of physical properties are performed under the conditions of room temperature (20° C. or higher and 25° C. or lower)/relative humidity of 40% RH or higher and 50% RH or lower.

In this specification, cation-modified silica refers to a compound in which a cationic group (for example, an amino group or a quaternary ammonium group) is bound to the surface of silica (preferably colloidal silica). According to a preferred embodiment of the present invention, the cation-modified silica is amino group-modified silica, more preferably amino group-modified colloidal silica.

[Dispersion containing silica]
In the production 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. Silica contained in the silica dispersion is a raw material before being cationically modified (modified) using a silane coupling agent having a cationic group, which will be described later.

Silica as a raw material used in the present invention may be any of natural crystalline silica, natural amorphous silica, synthetic crystalline silica and synthetic amorphous silica. However, silica is preferably amorphous silica, more preferably synthetic amorphous silica. In addition, silica may be used individually by 1 type, or may be used in combination of 2 or more types. In addition, as silica, a commercially available product or a synthetic product may be used.

Examples of methods for producing amorphous silica include wet methods such as a method of neutralizing sodium silicate with a mineral acid (sodium silicate method) and a method of hydrolyzing alkoxysilane (sol-gel method); A method of synthesizing silica particles by vaporization and a gas phase reaction in a high-temperature hydrogen flame (gas phase method, gas combustion method), pulverized silica silica, a reducing agent such as metal silicon powder or carbon powder, and a slurry A dry method such as a method (melting method) in which a mixed raw material consisting of water for forming a shape is heat-treated at a high temperature in a reducing atmosphere to generate SiO gas, and the SiO gas is cooled in an atmosphere containing oxygen. and is not particularly limited. However, from the viewpoint of reducing metal impurities, colloidal silica is preferable as amorphous silica, and colloidal silica produced by a sol-gel method is more preferable. Colloidal silica produced by the sol-gel method is preferable because it contains a small amount of corrosive ions such as metal impurities and chloride ions that are diffusible in semiconductors. The production of colloidal silica by the sol-gel method can be carried out using a conventionally known method. Colloidal silica can be obtained by performing a hydrolysis/condensation reaction in a mixed solvent with 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 with a dispersion medium.

Water or a mixed solvent of water and an organic solvent is used as a dispersion medium for the silica dispersion. Examples of organic solvents include hydrophilic 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. Organic solvents are mentioned. These organic solvents may be used singly 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.

Silica contained in the silica dispersion usually exists in the form of secondary particles, which are aggregates of primary particles. Although the lower limit of the average particle size (average secondary particle size) of secondary particles of silica is not particularly limited, it is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. The upper limit of the average secondary particle size 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 size 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 size is 10 nm or more, the dispersibility is sufficiently ensured even if the silica concentration is high. On the other hand, if the average secondary particle size is 300 nm or less, generation of coarse particles is prevented. . In addition, as the value of the average secondary particle size, a value measured as a volume average particle size by a dynamic light scattering method can be adopted.

The lower limit of the average primary particle size of 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. The upper limit of the average primary particle size 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 size 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 size of silica is based on the specific surface area (SA) of silica, assuming that the particle shape of silica is a true sphere, and is calculated using the formula SA = 4πR ² (R is the radius). can be done. The degree of association (average secondary particle size/average primary particle size) calculated from these values is not particularly limited, and is preferably about 1.0 or more and 5.0 or less.

The specific surface area of silica contained in the silica dispersion is not particularly limited, and can be appropriately selected according to the form of use of the cation-modified silica. The specific surface area is preferably 10 m ² /g or more and 600 m ² /g or less, more preferably 15 m ² /g or more and 300 m ² /g or less, and 20 m ² /g or more and 200 m ² /g or less. is more preferred. As the value of the specific surface area, a value calculated by the nitrogen adsorption method (BET method) can be adopted.

The lower limit of the concentration (content) of silica 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 further preferably 10% by mass or more. The upper limit of the concentration (content) of silica 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. That is, the concentration (content) of silica 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.

The pH of the silica dispersion is not particularly limited, but is preferably 5.0 or more and 11.0 or less, more preferably 6.0 or more and 10.5 or less, and still more preferably 7.0 or more and 10.0 or less. is.

Further, if necessary, the silica dispersion prepared above may be further subjected to various treatment steps. As such a treatment step, for example, a step of reducing the viscosity of the silica dispersion is exemplified. The step of reducing the viscosity of the silica dispersion includes, for example, a step of adding an alkaline solution (an aqueous solution of various bases such as ammonia water) or an organic solvent to the silica dispersion. At this time, the amount of the alkaline solution or organic solvent to be added is not particularly limited, and may be appropriately set in consideration of the viscosity of the silica dispersion obtained after the addition. By carrying out the step of reducing the viscosity of the silica dispersion in this way, there is an advantage that the initial dispersibility of the cationic silane coupling agent in the silica dispersion can be improved and the aggregation of silica particles can be suppressed. .

[Silane coupling agent having a cationic group]
As described above, in order to cation-modify silica (colloidal silica), a dispersion containing silica and a solution containing a silane coupling agent having a cationic group (for example, an amino group or a quaternary ammonium group) are combined. They may be mixed and allowed to react at a predetermined temperature for a predetermined time. In the following, the silane coupling agent having a cationic group is simply referred to as "silane coupling agent", and the solution containing the silane coupling agent having a cationic group is simply referred to as "silane coupling agent solution". .

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, 3-(2 -aminoethylamino)propyltriethoxysilane, 3-(2-aminoethylamino)propyldimethoxymethylsilane, 3-aminopropyldimethoxyethylsilane, trimethoxy[3-(methylamino)propyl]silane, trimethoxy[3-(phenyl amino)propyl]silane, [3-(N,N-dimethylamino)propyl]trimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldisilane, Ethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyl Triisopropoxysilane, 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]butan-1-amine, (aminoethylaminoethyl)phenyltriethoxysilane, methylbenzylaminoethylaminopropyltrimethoxysilane, benzylaminoethylaminopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, (aminoethylaminoethyl)phenethyltrimethoxysilane, (aminoethylaminomethyl)phenethyltrimethoxysilane, N-[ 2-[3-(Trimethoxysilyl)propylamino]ethyl]ethyl diamine, trimethoxy[2-(2-aminoethyl)-3-aminopropyl]silane, diaminomethylmethyldiethoxysilane, methylaminomethylmethyldiethoxysilane, p-aminophenyltrimethoxysilane, N-methylaminopropyltrisilane ethoxysilane, N-methylaminopropylmethyldiethoxysilane, N-phenylaminomethyltrimethoxysilane, N-phenylaminomethyldimethoxymethylsilane, (phenylaminomethyl)trimethoxysilane, (phenylaminomethyl)methyldiethoxysilane, Acetamidopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltrimethoxysilane, N-vinylbenzyl-3-aminopropyltriethoxysilane, N-cyclohexylaminomethyltriethoxysilane Silane, N-cyclohexylaminomethyldiethoxymethylsilane, (2-aminoethyl)aminomethyltrimethoxysilane, (aminomethyl)dimethoxymethylsilane, (aminomethyl)trimethoxysilane, bis(3-trimethoxysilylpropyl)amine , N,N′-bis[3-(trimethoxysilyl)propyl]ethylenediamine, amino group-containing silanes; octadecyldimethyl-(γ-trimethoxysilylpropyl)-ammonium chloride, N-trimethoxysilylpropyl-N, silanes containing quaternary ammonium groups such as N,N-trimethylammonium chloride;

These silane coupling agents may be used singly or in combination of two or more. Moreover, a commercially available product or a synthetic product may be used as the silane coupling agent.

Among the above silane coupling agents, 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]butan-1-amine, and bis[(3-trimethoxysilyl) At least one selected from the group consisting of propyl]amine is preferred. The silane coupling agent is more preferably 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]butan-1-amine, and bis[(3-trimethoxysilyl) ) is at least one selected from the group consisting of propyl]amine;

A silane coupling agent solution can be obtained by mixing and stirring a solvent and a silane coupling agent. At this time, the solvent used for the silane coupling agent solution is not particularly limited as long as it can dissolve the silane coupling agent. Examples of the solvent include water and organic solvents exemplified as the dispersion medium in the section [Dispersion liquid containing silica].

In the production 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, a sufficient surface modification effect cannot be obtained. On the other hand, when the concentration (content) is 1% by mass or more, the number 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, more preferably 0.05% by mass or more. Further, 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, and even more preferably 0.3% by mass or less. Preferably, 0.15% by mass or less is most preferable. That is, 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. , more preferably 0.05 mass % or more and 0.3 mass % or less, and most preferably 0.05 mass % or more and 0.15 mass % or less.

[Mixing of dispersion liquid containing silica and silane coupling agent solution]
The cation-modified silica according to the present embodiment is obtained by mixing the silica-containing dispersion described above and a silane coupling agent solution having a cationic group. Specifically, due to the mixing, the silica and a silane coupling agent having a cationic group react, a cationic group is introduced as a modifying group on the surface of the silica particles, cation-modified silica is generated, and the cation A dispersion containing modified silica is obtained.

In the production 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 at the same time. From the viewpoint of further suppressing the generation of coarse particles, the mixing method is preferably a method of adding a solution containing a silane coupling agent to the silica dispersion. In this case, the silane coupling agent solution may be added all at once, dividedly, or continuously added. The rate of addition in the case of continuous addition is appropriately adjusted according to the concentration of the silica dispersion, the concentration of the silane coupling agent solvent, and the like. min or less.

The mixing mass ratio of silica and a silane coupling agent having a cationic group (silica/silane coupling agent having a cationic group) is appropriately selected depending on the introduction amount of the cationic group, etc., but is 100/0.01. 100/1 is preferable, and 100/0.05 to 100/0.8 is more preferable. If the mixing mass ratio is within such a range, the generation of coarse particles can be further suppressed.

The temperature of the silica dispersion and the silane coupling agent solution during mixing is not particularly limited, but is preferably in the range from room temperature to the boiling point of the solvent (dispersion medium). In the present embodiment, the reaction between silica and the silane coupling agent can proceed even at room temperature, so it is preferable to proceed the reaction at a temperature around room temperature (for example, 20° C. or higher and 35° C. or lower). Almost the entire amount of the added silane coupling agent reacts with silica by a very simple operation of stirring the reaction system for several hours even under conditions of a temperature near normal temperature (for example, 20° C. or higher and 35° C. or lower). However, there is also the advantage that almost no unreacted silane coupling agent remains. In other words, the present embodiment preferably does not include the step of heating the reaction system between the silica dispersion and the silane coupling agent solution.

The reaction time between the silica and the silane coupling agent (time for mixing the silica dispersion with the silane coupling agent solution) is not particularly limited, but is preferably 10 minutes or more and 10 hours or less, more preferably 30 minutes or more and 5 hours or less. From the viewpoint of allowing the reaction to proceed efficiently, 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, the stirring speed is usually 20 rpm (0.33 s ^-1 ) or more and 800 rpm (13.3 s ^-1 ) or less, preferably 50 rpm (0.83 s -1 ), from the viewpoint of uniformly dispersing the components ^{. 1} ) above 700 rpm (11.7 s ^-1 ) or below.

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

When the cation-modified silica obtained according to the above method contains a dispersion medium other than water, a dispersion medium other than water may be added as necessary in order to increase the long-term storage stability of the cation-modified silica. Water may be substituted. The method of replacing the dispersion medium other than water with water is not particularly limited, and an example thereof includes a method of dropping a constant amount of water while heating the cation-modified silica. Further, a method of separating the cation-modified silica from a dispersion medium other than water by precipitation/separation, centrifugation, or the like, and then re-dispersing it in water may also be used.

The lower limit of the zeta potential of the resulting cation-modified silica is preferably 6 mV or higher, more preferably 8 mV, and even more preferably 10 mV or higher. Moreover, the upper limit of the zeta potential of the resulting cation-modified silica is preferably 70 mV or less, more preferably 60 mV or less, and even more preferably 50 mV or less. That is, the zeta potential of the resulting cation-modified silica is preferably 6 mV or more and 70 mV or less, more preferably 8 mV or more and 60 mV or less, and even more preferably 10 mV or more and 50 mV or less. In addition, in this specification, the zeta potential of cation-modified silica adopts the value measured by the method described in the Examples. The zeta potential of cation-modified silica can be adjusted by the amount of cationic groups possessed by cation-modified silica.

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

(Method for measuring the number of coarse particles)
An aqueous dispersion was prepared by dispersing cation-modified silica in water at a concentration of 0.27% by mass and adjusting the pH to 4.0, and the particle size present in the resulting cation-modified silica aqueous dispersion was 0. Measure the number of coarse particles greater than 7 μm per unit volume using a liquid particle counter. The details of the method for measuring the number of coarse particles are as described in Examples.

[Other processes]
The method for producing a polishing composition according to the present invention may further include other steps as long as the effects of the present invention are not impaired. Examples of such other steps include a step of filtering a dispersion containing cation-modified silica, a step of mixing a dispersion containing cation-modified silica and another additive (preferably a pH adjuster), and a step of further filtering the dispersion containing the cation-modified silica after mixing the additive. These steps are described below.

<Step of Filtration of Dispersion Liquid Containing Cation-Modified Silica (First 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.

In the production method according to the present invention, the filtration step may be performed in only one stage or in multiple stages of two or more stages. The technical contents described in this section are applied to the filtration in the case of only one stage of the filtration process and to the first stage of the filtration in the case of multiple stages of the filtration process. The technical content of the second and subsequent stages of filtration when the filtration process is multi-stage will be described later.

The media shape of the filter used in this step is not particularly limited, and filters having various structures, shapes, and functions can be appropriately employed. As a specific example, it is preferable to employ a pleated type, depth type, depth pleat type, membrane type, or adsorption type filter that has excellent filterability. The structure of the filter is not particularly limited, and may be a bag-like bag type or a hollow cylindrical cartridge type. The cartridge type filter may be of gasket type or O-ring type. Filtration conditions (for example, filtration differential pressure, filtration rate) may be appropriately set based on common technical knowledge in this field, taking into account the target quality, production efficiency, and the like.

The mesh size (pore diameter) of the filter used in this step is preferably 0.05 µm or more, more preferably 0.1 µm or more, and still more preferably 0.2 µm or more, from the viewpoint of improving the yield. Moreover, from the viewpoint of enhancing the effect of removing foreign matters and aggregates, the mesh size (pore size) of the filter used in this step is preferably 100 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

That is, the mesh size (pore size) of the filter used in this step is preferably 0.05 μm or more and 100 μm or less, more preferably 0.1 μm or more and 30 μm or less, and still more preferably 0.2 μm or more and 20 μm or less.

The material of the filter used in this step is not particularly limited, and examples thereof include cellulose, nylon, polysulfone, polyethersulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, and glass.

The filtration method is also not particularly limited, and for example, in addition to natural filtration performed at normal pressure, known filtration methods such as suction filtration, pressure filtration, and centrifugal filtration can be appropriately employed.

A commercially available filter may be used in this step. Examples of commercially available filters include Nuclipore membrane filters (manufactured by Whatman) and HC series, BO series, SLF series, SRL series and MPX series manufactured by Rokitechno Co., Ltd., which are equipped with polypropylene nonwoven fabric as a filter medium. be done.

<Step of mixing other additives>
In this step, the dispersion containing the cation-modified silica obtained above and other additives are mixed. 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 the post-process, the dispersion containing the cation-modified silica is filtered. After the step of filtering is preferred.

Examples of other additives include additives that can be components of the polishing composition, such as pH adjusters, dispersion media, preservatives, rust inhibitors, antioxidants, stabilizers, and pH buffers. Here, the pH adjuster will be explained.

(pH adjuster)
The pH adjuster has a role of adjusting the pH of the polishing composition according to the present invention to a desired value.

The pH adjuster is not particularly limited, and known pH adjusters used in the field of polishing compositions can be used. Among these, it is preferable to use known acids, bases, salts, amines, chelating agents, and the like. Examples of pH adjusters 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, mellitic acid, cinnamic acid , oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, aconitic acid, amino acids, anthranilic acid, carboxylic acids such as nitrocarboxylic acid; methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, Sulfonic acids such as p-toluenesulfonic acid, 10-camphorsulfonic acid, isethionic acid, taurine; carbonic acid, hydrochloric acid, nitric acid, phosphoric acid, hypophosphorous acid, phosphorous acid, phosphonic acid, sulfuric acid, boric acid, hydrogen fluoride Inorganic acids such as acids, orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, metaphosphoric acid, and hexametaphosphoric acid; hydroxides of alkali metals such as potassium hydroxide (KOH); hydroxides of group 2 elements; ammonia; organic bases such as tetraammonium; 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-acetamido)iminodiacetic acid, Hydroxyethyliminodiacetic acid, N,N-di(2-hydroxyethyl)glycine, N-[tris(hydroxymethyl)methyl]glycine, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, N,N,N-tri methylenephosphonic acid, ethylenediamine-N,N,N',N'-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-diaminopropanetetraacetic acid, glycol etherdiaminetetraacetic acid, ethylenediamineorthohydroxyphenylacetic acid, ethylenediaminedi Succinic acid (SS form), N-(2-carboxylateethyl)-L-aspartic acid, β-alanine diacetic acid, phosphonobutanetricarboxylic acid (2-phosphonobutane-1,2,4-tricarboxylic acid), hydroxyethyl dendiphosphonic acid (HEDP) (1-hydroxyethylidene-1,1-diphosphonic acid), nitrilotrismethylene phosphonic acid, N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, 1, Chelating agents such as 2-dihydroxybenzene-4,6-disulfonic acid, polyamine, polyphosphonic acid, polyaminocarboxylic acid and polyaminophosphonic acid, or salts thereof, and the like can be mentioned. These pH adjusters may be used singly or in combination of two or more. Among these pH adjusters, 10-camphorsulfonic acid, p-toluenesulfonic acid, isethionic acid, and the like have relatively bulky skeletons from the viewpoint of suppressing the removal rate of silicon nitride and/or TEOS type silicon oxide films. Strong acids are preferred.

The amount of the pH adjuster to be added may be appropriately selected so as to obtain the desired pH value of the polishing composition.

In addition to the role of adjusting the pH of the polishing composition, the pH adjuster may also be used to adjust the pH for storage of the dispersion liquid containing the cation-modified silica. That is, in addition to this step, a step of adding a pH adjuster to the dispersion containing cation-modified silica and storing the dispersion 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 a pH adjuster so that the pH of the dispersion during storage becomes acidic.

<Step of further filtering the dispersion liquid containing cation-modified silica (filtration after the second stage)>
In this step, the dispersion containing the cation-modified silica obtained above is further filtered. The technical content described in this section is applied to the second and subsequent stages of filtration when the filtration process is multi-stage (two or more stages).

Regarding the media shape, structure, material, filtration conditions, filtration method, etc. of the filter used in this step, refer to the above <Step of filtering dispersion liquid containing cation-modified silica (first stage filtration)>. can be used.

However, industrially, the pleated type, the depth type, and the depth pleated type are preferred as the media shape of the filter from the viewpoint of production efficiency. Moreover, from the viewpoint of improving the yield and the effect of removing foreign substances and aggregates, it is preferable to use the above-mentioned pleated type, depth type, or depth pleat type filter in a multistage filtration process.

In this case, it is preferable that the mesh size (pore size) of the filter is the same size or gradually decreases from the front stage to the rear stage in the multi-stage filtration process.

The mesh size (pore size) of the filter used in this step is preferably 0.05 μm or more, more preferably 0.1 μm or more, and still more preferably 0.15 μm or more, from the viewpoint of improving the yield. In addition, from the viewpoint of enhancing the effect of removing foreign substances and aggregates, the mesh size (pore size) of the filter used in this step is preferably 10 μm or less, more preferably 5 μm or less, still more preferably 1 μm or less, and even more preferably It is 0.7 μm or less, particularly preferably 0.4 μm or less. That is, the mesh size (pore diameter) of the filter used in this step is preferably 0.05 μm or more and 10 μm or less, more preferably 0.1 μm or more and 5 μm or less, still more preferably 0.15 μm or more and 1 μm or less, still more preferably 0.15 μm or more and 0.7 μm or less, particularly preferably 0.15 μm or more and 0.4 μm or less.

Also in this step, a commercially available filter can be used. Examples of commercially available filters used in this step include Ultipleats (registered trademark) P-nylon 66 and Ultipor (registered trademark) N66 manufactured by Nippon Pall Co., Ltd.

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

(Method for measuring the number of coarse particles)
An aqueous dispersion was prepared by dispersing cation-modified silica in water at a concentration of 0.27% by mass and adjusting the pH to 4.0, and the particle size present in the resulting cation-modified silica aqueous dispersion was 0. Measure the number of coarse particles greater than 7 μm per unit volume using a liquid particle counter.

Examples of the dispersion medium contained in the polishing composition include the dispersion medium mentioned in the section [Dispersion liquid containing silica].

The cation-modified silica contained in the polishing composition according to this embodiment functions as abrasive grains. The lower limit of the content of the cation-modified silica in the polishing composition is preferably 0.1% by mass or more, and preferably 0.2% by mass or more, relative to the total mass of the polishing composition. More preferably, it is 0.5% by mass or more. The upper limit of the content of cation-modified silica in the polishing composition is preferably 20% by mass or less, more preferably 10% by mass or less, relative to the total mass of the polishing composition. It is more preferably 5% by mass or less. That is, the content of 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, relative to the total mass of the polishing composition. 5% by mass or more and 5% by mass or less is more preferable.

The polishing composition according to the present embodiment contains known additives that can be used in polishing compositions, such as pH adjusters, complexing agents, preservatives, and antifungal agents, as long as the effects of the present invention are not impaired. may be further included as necessary.

The polishing composition according to the present embodiment is suitably used for polishing, for example, polysilicon, silicon nitride, silicon carbonitride (SiCN), silicon oxide, metal, SiGe, and the like.

Examples of polishing objects containing silicon oxide include, for example, a TEOS-type silicon oxide surface (hereinafter also simply referred to as “TEOS”) produced using tetraethyl orthosilicate as a precursor, and a HDP (High Density Plasma) film. , USG (Undoped Silicate Glass) film, PSG (Phosphorus Silicate Glass) film, BPSG (Boron-Phospho Silicate Glass) film, RTO (Rapid Thermal Oxidation) film, and the like.

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

The present invention will be described in more detail with 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 "% by mass" and "parts by mass" respectively.

[Methods for measuring various physical properties]
In the present examples, various physical properties were measured by the following methods.

<Measurement of particle size>
The average primary particle size of silica used as a raw material is SA=4πR ² (R is radius).

<Measurement of pH>
The pH of various water dispersions and aqueous solutions was confirmed with a pH meter (manufactured by Horiba, Ltd., model number: F-71).

[Production of cation-modified silica]
(Example 1)
In a 2 L plastic mug, deionized water and synthetic amorphous silica (colloidal silica, average primary particle size of silica: 24 nm, average secondary particle size of silica: 47 nm, zeta potential: 5.5 mV) are mixed, An aqueous dispersion (pH 7.5) with a final concentration of 19.88% by weight of synthetic amorphous silica was obtained.

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

While stirring 1000 g of silica aqueous 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. Thereafter, the stirring state was maintained at room temperature (25° C.) for 50 minutes to obtain an aqueous dispersion of cation-modified (amino-modified) silica having an amino group introduced on the silica surface.

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

(Example 4)
0.771 g of 3-aminopropyltriethoxysilane (APTES) and 771 g of deionized water were mixed in a 2 L plastic jug to prepare an APTES aqueous solution with a concentration of 0.10 mass %.

Separately, deionized water and synthetic amorphous silica (average primary particle size: 24 nm, average secondary particle size: 47 nm) were mixed to form a water dispersion of silica having a final concentration of synthetic amorphous silica of 19.88% by mass. A liquid (pH 7.46) was prepared.

While stirring the total amount of the APTES aqueous solution prepared above at 230 rpm, 1000 g of the aqueous dispersion of silica prepared above was added dropwise at a dropping rate of 16 mL/min. Thereafter, the stirring state was maintained at room temperature (25° C.) for 50 minutes to obtain an aqueous dispersion of cation-modified (amino-modified) silica having an amino group introduced on the silica surface.

Table 1 below shows the composition of the silica aqueous dispersion and the silane coupling agent aqueous solution used in each of the examples and comparative examples.

[evaluation]
<Measurement of number of coarse particles>
As a sample, an aqueous dispersion prepared by dispersing cation-modified silica in deionized water so that the concentration of cation-modified silica was 0.27% by mass and then adjusting the pH to 4.0 using sulfuric acid was used.

The number of coarse particles exceeding 0.7 μm per unit volume (1 mL) present in the obtained aqueous cation-modified silica dispersion was measured using a liquid particle counter (LPC, Liquid Particle Counter, AccuSizer (registered trademark) FX (Japan (manufactured by Entegris LLC)). At this time, the average value of n=3 was obtained and rounded off to the nearest whole number.

<Measurement of zeta potential>
The zeta potential of the obtained cation-modified silica was measured using a zeta potential measuring device (trade name “ELS-Z”) manufactured by Otsuka Electronics Co., Ltd. As a sample, an aqueous dispersion prepared by dispersing the cation-modified silica in deionized water so that the concentration thereof was 1.8% by mass and then adjusting the pH to 3.0 using sulfuric acid was used.

<Filtration rate>
The aqueous dispersions of cation-modified silica obtained in the above Examples and Comparative Examples were subjected to suction filtration using a Nuclepore membrane filter (manufactured by Whatman) having a pore size of 3.0 μm and a diameter of 47 mm. (Filtration amount per minute)) was measured. In addition, the filtration speed is the average speed when filtration is performed for 5 minutes.

The above evaluation results are shown in Table 2 below. Note that the blanks in Table 2 below indicate that they have not been evaluated.

As is clear from Table 2 above, the zeta potential of the cation-modified silica in the aqueous dispersions obtained in the examples was higher than that of the raw synthetic amorphous silica. From this, it was found that cation-modified silica in which cationic groups are bonded to the surface of synthetic amorphous silica can be obtained by the production methods of Examples.

The aqueous cation-modified silica dispersions of Comparative Examples 1 and 2 clogged the filter during filtration for 5 minutes, and the filtration rate was low. On the other hand, it was found that the aqueous dispersions of cation-modified silica obtained in Examples had less coarse particles and had superior filterability compared to the aqueous dispersions of Comparative Examples. From this, when the polishing composition is produced, if the cation-modified silica aqueous dispersion of the example having excellent filterability is used, it is possible to use a fine filter, and the polishing composition It is advantageous for reducing the number of coarse particles.

(Example 21, Comparative Example 4)
The aqueous cation-modified silica dispersion obtained in Example 7 above was filtered using a filter with a pore size of 10 μm (SLF type (depth type), manufactured by Rokitechno Co., Ltd.). This filtered aqueous cation-modified silica dispersion was dispersed in deionized water so that the concentration of cation-modified silica was 5.4% by mass, and then adjusted to pH 4.0 using 10-camphorsulfonic acid. It was adjusted. Furthermore, this cation-modified silica aqueous dispersion is filtered using a filter with a pore size of 0.2 μm (Ultipor (registered trademark) N66 (pleated type), manufactured by Nippon Pall Co., Ltd.), and the polishing composition of Example 21 is obtained. (slurry) was prepared.

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

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 in the measurement of the number of coarse particles.

As is clear from Table 3 above, the polishing composition of Example 21, which was prepared using the cation-modified silica water dispersion in the water dispersion obtained in Example, had a larger number of coarse particles than Comparative Example 4. number was small. By performing polishing using a polishing composition containing few coarse particles, it is possible to suppress the occurrence of defects during polishing.

Claims (9)

A dispersion containing silica and a solution containing a silane coupling agent having a cationic group at a concentration of 0.03% by mass or more and less than 1% by mass are mixed to obtain a dispersion containing cation-modified silica. A method for producing a polishing composition, comprising: Claim 1, wherein the mixing mass ratio of the silica and the silane coupling agent having a cationic group (silica/silane coupling agent having a cationic group) is 100/0.05 to 100/0.8. The manufacturing method described in . The production 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 0.6% by mass or less. The production method according to any one of claims 1 to 3, wherein the mixing includes adding a solution containing a silane coupling agent having a cationic group to the dispersion containing silica. The production method according to any one of claims 1 to 4, wherein the silica is colloidal silica. The silane coupling agent having a cationic group includes 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethoxymethylsilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3-(2-aminoethylamino)propyldimethoxymethylsilane, 3-aminopropyldimethoxymethylsilane, trimethoxy[3-(methylamino)propyl]silane, trimethoxy[ 3-(phenylamino)propyl]silane, [3-(N,N-dimethylamino)propyl]trimethoxysilane, [3-(6-aminohexylamino)propyl]trimethoxysilane, N-methyl-3-( at least one selected from the group consisting of triethoxysilyl)propan-1-amine, N-[3-(trimethoxysilyl)propyl]butan-1-amine, and bis[(3-trimethoxysilyl)propyl]amine The production method according to any one of claims 1 to 5, which is a seed. The production method according to any one of claims 1 to 6, further comprising filtering the dispersion containing the cation-modified silica. The production method according to any one of claims 1 to 7, further comprising mixing the dispersion containing the cation-modified silica with a pH adjuster. a cation-modified silica having a cationic group;
a dispersion medium,
The polishing composition, wherein the cation-modified silica contains 500,000 particles/mL or less of coarse particles having a particle diameter of more than 0.7 μm as measured by the following measuring method:
(Measuring method)
After dispersing cation-modified silica in water at a concentration of 0.27% by mass and preparing an aqueous dispersion with a pH adjusted to 4.0, the particle size present in the resulting cation-modified silica aqueous dispersion is The number of coarse particles exceeding 0.7 μm per unit volume (1 mL) is measured using a liquid particle counter.