Surface-modified colloidal silica and polishing composition containing the same

Abstract

To provide means that can improve the wettability of surface-modified colloidal silicas on a polishing object and also improve the temporal stability.SOLUTION: A surface-modified colloidal silica contains a colloidal silica, and a surface modification group that surface-modifies the colloidal silica and contains a polyoxyalkylene chain with a weight average molecular weight of 20,000 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to surface-modified colloidal silica and a polishing composition containing the same.

Background Art

[0002] In recent years, with the multilayer wiring of the semiconductor substrate surface, when manufacturing devices, a so-called Chemical Mechanical Polishing (CMP) technique of physically polishing and planarizing the semiconductor substrate is utilized. CMP is a method of planarizing the surface of an object to be polished (workpiece) such as a semiconductor substrate using a polishing composition (slurry) containing abrasive grains such as silica, alumina, and ceria, a corrosion inhibitor, a surfactant, etc. Specifically, it is used in processes such as shallow trench isolation (STI), planarization of an interlayer insulating film (ILD film), tungsten plug formation, and formation of a multilayer wiring composed of copper and a low dielectric constant film.

[0003] For example, Patent Document 1 discloses colloidal silica surface-modified with polyethylene oxide having a molecular weight of 15,000 or less and a polishing composition for CMP containing the same.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technique described in Patent Document 1, the wettability of the polishing composition with respect to the object to be polished is low, and there is a problem that the polishing performance improvement effects such as maintaining the surface state of the object to be polished and / or obtaining an appropriate polishing rate cannot be sufficiently obtained. Further, in the technique described in Patent Document 1, there is a problem that the storage stability is insufficient, such as the dispersibility of the surface-modified (surface-treated) colloidal silica decreasing over time.

[0006] Therefore, an object of the present invention is to provide a means capable of improving the wettability of the surface-modified colloidal silica with respect to the object to be polished and improving the storage stability.

Means for Solving the Problems

[0007] In order to solve the above problems, the present inventors have conducted intensive research. As a result, it has been found that the above problems can be solved by a surface-modified colloidal silica containing colloidal silica and a surface-modifying group having a polyoxyalkylene chain with a weight average molecular weight of 20,000 or more for surface-modifying the colloidal silica, and the present invention has been completed.

Effects of the Invention

[0008] According to the present invention, there is provided a means capable of improving the wettability of the surface-modified colloidal silica with respect to the object to be polished and improving the storage stability.

Embodiments for Carrying Out the Invention

[0009] The present invention is a surface-modified colloidal silica containing colloidal silica and a surface-modifying group having a polyoxyalkylene chain with a weight average molecular weight of 20,000 or more for surface-modifying the colloidal silica. According to the surface-modified colloidal silica according to one embodiment of the present invention having such a configuration, the wettability with respect to the object to be polished can be improved, and the storage stability can be improved.

[0010] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited only to the following embodiments.

[0011] In this specification, unless otherwise specified, measurements of operations, physical properties, etc. are carried out 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.

[0012] [Surface-modified colloidal silica] (Colloidal silica) Examples of the method for producing the colloidal silica contained in the surface-modified colloidal silica according to the present invention include the sodium silicate method and the sol-gel method. Any colloidal silica produced by any production method can be preferably used in the present invention. However, from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferred. Colloidal silica produced by the sol-gel method is preferred because it contains less diffusible metal impurities and corrosive ions such as chloride ions in the semiconductor. The production of colloidal silica by the sol-gel method can be carried out using a conventionally known method. Specifically, a hydrolyzable silicon compound (for example, alkoxysilane or its derivative) is used as a raw material, and a hydrolysis / condensation reaction is carried out to obtain colloidal silica.

[0013] The lower limit of the average primary particle diameter of the colloidal silica is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 7 nm or more. Further, in the polishing composition of the present invention, the upper limit of the average primary particle diameter of the colloidal silica is preferably 100 nm or less, more preferably 75 nm or less, and even more preferably 50 nm or less. Within such a range, defects such as scratches that may occur on the surface of the object to be polished after polishing using the polishing composition can be suppressed. The average primary particle diameter of the colloidal silica is calculated, for example, based on the specific surface area of the colloidal silica measured by the BET method.

[0014] The lower limit of the average secondary particle diameter of the colloidal silica is preferably 2 nm or more, more preferably 10 nm or more, and even more preferably 15 nm or more. Further, in the polishing composition of the present invention, the upper limit of the average primary particle diameter of the colloidal silica is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less. The average secondary particle diameter of the colloidal silica can be measured, for example, by a dynamic light scattering method typified by the laser diffraction scattering method.

[0015] The average aggregation degree of the colloidal silica is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. Defects can be further reduced. The average aggregation degree of the colloidal silica is also preferably 1.0 or more, more preferably 1.2 or more, and even more preferably 1.5 or more. The average aggregation degree is obtained by dividing the value of the average secondary particle diameter of the colloidal silica by the value of the average primary particle diameter.

[0016] The shape of the colloidal silica is not particularly limited and may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal columnar shapes such as triangular columns and square columns, cylindrical shapes, barrel shapes in which the central part of the cylinder bulges more than the end part, donut shapes in which the central part of the disk penetrates, plate shapes, so-called cocoon-shaped with a constriction in the central part, so-called aggregated spherical shapes in which a plurality of particles are integrated, so-called sugar ball shapes with a plurality of protrusions on the surface, rugby ball shapes, and various other shapes, and are not particularly limited.

[0017] [Surface modification group having a polyoxyalkylene chain] The surface-modified colloidal silica of the present invention has a surface modification group. The surface modification group according to the present invention is a group having a polyoxyalkylene chain with a weight average molecular weight of 20,000 or more.

[0018] Examples of the polyoxyalkylene chain include, for example, a polyethylene glycol chain, a polypropylene glycol chain, a polytrimethylene glycol chain, a polytetramethylene glycol chain, a polyisobutylene glycol chain, and the like. In the surface modifying group according to the present invention, the polyoxyalkylene chain may be composed of only one kind of oxyalkylene or may be composed of two or more kinds of oxyalkylenes. Examples of the polyoxyalkylene chain composed of two or more kinds of oxyalkylenes include, for example, a polyoxyethylene-polyoxypropylene chain, a polyoxyethylene-polyoxytetramethylene chain, a polyoxyethylene-polyoxypropylene-polyoxyethylene chain, and the like. When the surface modifying group according to the present invention is composed of two or more kinds of oxyalkylenes, the bonding form of the two or more kinds of oxyalkylenes may be any of random, alternating, block, and periodic. Among them, at least one selected from the group consisting of a polyoxyethylene chain, a polyoxypropylene chain, a polyoxyethylene-polyoxypropylene chain, and a polyoxyethylene-polyoxypropylene-polyoxyethylene chain is preferable, and a polyoxyethylene chain is more preferable.

[0019] The surface modifying group of the present invention may have a structure in which the terminal of the polyoxyalkylene chain is blocked with an aliphatic hydrocarbon group. That is, the hydrogen atom in the hydroxyl group at one terminal of the polyoxyalkylene chain may be substituted with an aliphatic hydrocarbon group.

[0020] Examples of the aliphatic hydrocarbon group that caps the terminal of the polyoxyalkylene chain include aliphatic hydrocarbon groups having 1 to 10 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include, for example, linear or branched alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group, decyl group, etc.; linear or branched alkenyl groups such as vinyl group, allyl group, etc.; alkynyl groups such as ethynyl group, propynyl group, etc. Among them, linear or branched alkyl groups are preferred.

[0021] The polyoxyalkylene chain in the surface-modifying group of the present invention has a weight average molecular weight (Mw) as polyoxyalkylene of 20,000 or more. When the weight average molecular weight of the polyoxyalkylene chain is less than 20,000, the wettability decreases. Also, in order to obtain the desired performance, it is necessary to add a large amount of the surface modifier during synthesis, and as a result, the stability over time of the surface-modified colloidal silica decreases. The upper limit of the weight average molecular weight of the polyoxyalkylene chain is not particularly limited, but is preferably 100,000 or less, and more preferably 50,000 or less. The weight average molecular weight of polyoxyalkylene can be measured by gel permeation chromatography (GPC) using polyethylene glycol as a standard substance.

[0022] Furthermore, the surface-modifying group according to the present invention preferably contains a silicon atom and a linking group, and is more preferably at least one group selected from the group consisting of the group represented by the following formula (1), the group represented by the following formula (2), and the group represented by the following formula (3). The wavy bond in the following formulas (1) to (3) binds to the surface of the colloidal silica.

[0023]

Chemical formula

[0024] In the above formulas (1) to (3), R1 each independently represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, R 2 each independently represents an alkylene group, n is each independently the average degree of polymerization (number average degree of polymerization) of the oxyalkylene chain [-(O-R 2 )-], and is a number of 280 or more, X each independently represents a single bond or a linking group (a divalent group having 1 or more atoms), R 3 and R 4 each independently represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 3 carbon atoms, or a group represented by the following formula (a),

[0025]

Chemical formula

[0026] In the above formula (a), R A represents [-X-(O-R 2 ) n -OR 1 , and at this time, X, R A in R 1 , R 2 , and n are each the X, R 1 , R 2 , and n defined by the above formulas (1) to (3), and R 5 and R 6 each independently represents a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms, and l and m each independently represent a number of 0 or more. In the formula (a), the bond extending from the silicon atom to the left is bonded to an oxygen atom. The wavy bond in the formula (a) is bonded to the surface of the colloidal silica.

[0027] In the above formulas (1) to (3), R 1Examples of the hydrocarbon group having 1 to 30 carbon atoms used in [description] include, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, isobutyl group, amyl group, isoamyl group, tert-amyl group, n-hexyl group, cyclohexyl group, cyclohexylmethyl group, 2-cyclohexylethyl group, n-heptyl group, isoheptyl group, tert-heptyl group, n-octyl group, isooctyl group, tert-octyl group, 2-ethylhexyl group, n-nonyl group, isononyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group and other alkyl groups; vinyl group, 1-methylethenyl group, 2-methylethenyl group, propenyl group, butenyl group, isobutenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, decenyl group, pentadecenyl group, 1-phenylprop-3-yl and other alkenyl groups; phenyl group, naphthyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-vinylphenyl group, 3-isopropylphenyl group, 4-isopropylphenyl group, 4-butylphenyl group, 4-isobutylphenyl group, 4-tert-butylphenyl group, 4-hexylphenyl group, 4-cyclohexylphenyl group, 4-octylphenyl group, 4-(2-ethylhexyl)phenyl group, 4-stearylphenyl group, 2,3-dimethylphenyl group, 2,4-dimethylphenyl group, 2,5-dimethylphenyl group, 2,6-dimethylphenyl group, 3,4-dimethylphenyl group, 3,5-dimethylphenyl group, 2,4-di-tert-butylphenyl group and other alkylaryl groups; benzyl group, phenethyl group, 2-phenylprop-2-yl group, diphenylmethyl group, triphenylmethyl group and other arylalkyl groups; styryl group, cinnamyl group and other arylalkenyl groups and the like.

[0028] In the above formulas (1) to (3), R 2represents an alkylene group, preferably an alkylene group having 1 to 4 carbon atoms. Examples of the alkylene group having 1 to 4 carbon atoms include a methylene group, an ethylene group, a propylene group (methylethylene group), a trimethylene group, a butylene group (tetramethylene group), and an isobutylene group. Among them, an ethylene group and a propylene group are preferred. A plurality of R 2 may be the same or different from each other. A plurality of R 2 When they are different, the bonding form of the above oxyalkylene chain [-(O-R 2 )-] may be any of random, alternating, block, and periodic.

[0029] In the above formulas (1) to (3), n represents the average degree of polymerization (number average degree of polymerization) of the oxyalkylene chain [-(O-R 2 )-] and represents a number of 280 or more. n is preferably a number of 345 or more and 1725 or less, more preferably a number of 455 or more and 1390 or less. When n is 280 or more, the steric hindrance between the surface modifying groups according to the present invention becomes sufficient, making it easy to disperse in the dispersion medium, and also showing good wettability to the object to be polished.

[0030] In the above formulas (1) to (3), X represents a single bond or a linking group (a divalent group having 1 or more atoms). Examples of the linking group include a divalent hydrocarbon group, a urethane bond, a carbonyl group, an ether bond, an ester bond, a carbonate group, an amide group, and a group in which one or more of these are linked in plurality.

[0031] Examples of the divalent hydrocarbon group include linear, branched, or cyclic alkylene groups having 1 to 18 carbon atoms. Examples of the linear, branched, or cyclic alkylene groups having 1 to 18 carbon atoms include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group (methylethylene group), a trimethylene group, a butylene group (tetramethylene group), a 1-methylpropylene group, a 2-methylpropylene group, a 1,2-dimethylpropylene group, a 1,3-dimethylpropylene group, a 1-methylbutylene group, a 2-methylbutylene group, a 3-methylbutylene group, a 2,4-dimethylbutylene group, a 1,3-dimethylbutylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, an n-octylene group, an ethane-1,1-diyl group, a propane-2,2-diyl group, a decane-1,10-diyl group, an undecane-1,11-diyl group, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, a tetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, a hexadecane-1,16-diyl group, a heptadecane-1,17-diyl group, an octadecane-1,18-diyl group, a cyclopentane-1,2-diyl group, a cyclopentane-1,3-diyl group, a cyclohexane-1,1-diyl group, a cyclohexane-1,2-diyl group, a cyclohexane-1,3-diyl group, a cyclohexane-1,4-diyl group, a methylcyclohexane-1,4-diyl group, a cyclohexane-1,4-dimethylene group, and the like.

[0032] As the linking group in X, from the viewpoint of ease of synthesis, it preferably contains a urethane bond, and more preferably is a group containing a divalent hydrocarbon group (particularly a linear or branched alkylene group) and a urethane bond. Further, it is preferable that the silicon atom in the above formulas (1) to (3) and the divalent hydrocarbon group (particularly a linear or branched alkylene group) in X are directly bonded. Specifically, X is preferably -(CH2) k -NH-C(=O)- (the left-end C is bonded to the silicon atom, and the right-end C is bonded to the O in the polyoxyalkylene chain, respectively). In the above formula, k represents a number of 1 or more and 18 or less, preferably a number of 1 or more and 6 or less, and more preferably a number of 1 or more and 3 or less.

[0033] In the above formula (1), R 3 and R 4 each independently represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 3 carbon atoms include alkyl groups such as methyl group, ethyl group, propyl group, and isopropyl group; alkenyl groups such as vinyl group and allyl group; and alkynyl groups such as ethynyl group and propynyl group. Among them, an alkyl group is preferred. Note that R 3 in formula (2) is the same as R 3 in formula (1).

[0034] In the above formula (a), R A represents [-X-(O-R 2 )n-OR 1 . X, R A in R 1 , R 2 , and n are the same as those exemplified and described for the above formulas (1) to (3), and the preferred embodiments are also the same. Also, the bonding form in the case of having two or more oxyalkylene chains [-(O-R 2 )-] is as described above. Note that the bond extending from the silicon atom to the left is bonded to an oxygen atom. The wavy bond in the formula is bonded to the surface of colloidal silica.

[0035] In the above formula (a), R 5 and R 6 each independently represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 3 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 3 carbon atoms include linear or branched alkyl groups such as methyl group, ethyl group, n-propyl group, and isopropyl group; linear or branched alkenyl groups such as vinyl group, allyl group, and propenyl group; and alkynyl groups such as ethynyl group and propynyl group. Among them, a linear or branched alkyl group is preferred.

[0036] In the above formula (a), l and m each independently represent a number of 0 or more. The bonding order of the structural unit with l and the structural unit with m is not particularly limited. That is, the silicon atom in formula (a) that binds to the oxygen atom in formula (1) or (2) may be the silicon atom in the structural unit with l or the silicon atom in the structural unit with m. Similarly, the oxygen atom in formula (a) that binds to R 6 in formula (a) may be the oxygen atom in the structural unit with l or the oxygen atom in the structural unit with m. Further, when one of l and m is a number of 1 or more and the other is a number of 2 or more, the bonding form of the structural unit with l and the structural unit with m may be any of random, alternating, block, and periodic.

[0037] When the surface-modified colloidal silica of the present invention has a plurality of R 1 ~R 6 , X, l, m, or n, the plurality of R 1 ~R 6 , X, l, m, and n may be the same or different from each other.

[0038] In the above formulas (1) and (2), the structure in which R 3 , R 4 is a hydrogen atom represents a structure in which an unreacted alkoxysilyl group in the surface-modifying group according to the present invention bonded to colloidal silica has been hydrolyzed. Further, the structure in which R 3 , R 4 is an aliphatic hydrocarbon group having 1 to 3 carbon atoms represents a structure in which an unreacted alkoxysilyl group in the surface-modifying group according to the present invention bonded to colloidal silica remains. Further, the structure in which R 3 , R 4 is a group represented by the above formula (a) represents a structure in which an unreacted alkoxysilyl group in the surface-modifying group according to the present invention bonded to colloidal silica has reacted with an alkoxysilyl group in an unreacted polyoxyalkylene chain-containing silane coupling agent and / or another surface-modifying group according to the present invention bonded to colloidal silica by dehydration condensation.

[0039] [Method for producing surface-modified colloidal silica] The method for producing surface-modified colloidal silica of the present invention is not particularly limited. For example, (a) A method in which a silane coupling agent having a group capable of reacting with a terminal hydroxy group of polyoxyalkylene having a weight average molecular weight of 20,000 or more and polyoxyalkylene are used to pre-synthesize a silane coupling agent containing a polyoxyalkylene chain, and this is reacted with colloidal silica: (b) A method in which a silane coupling agent having a group capable of reacting with a terminal hydroxy group of polyoxyalkylene having a weight average molecular weight of 20,000 or more is reacted with colloidal silica, and then polyoxyalkylene having a weight average molecular weight of 20,000 or more is further reacted: and the like. Among them, from the viewpoints such as easy control of the reaction and further reduction of the production cost, it is preferable to use the method (a). Hereinafter, the method (a) will be described in detail.

[0040] <Step of synthesizing a silane coupling agent containing a polyoxyalkylene chain> In this step, a silane coupling agent having a group capable of reacting with a terminal hydroxy group of polyoxyalkylene and polyoxyalkylene having a weight average molecular weight of 20,000 or more are reacted to synthesize a silane coupling agent containing a polyoxyalkylene chain (hereinafter, also simply referred to as "surface modifier").

[0041] The silane coupling agent having a group capable of reacting with the terminal hydroxy group of polyoxyalkylene is not particularly limited, but an isocyanate group-containing silane coupling agent is preferred. Examples of the isocyanate group-containing silane coupling agent include, for example, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyldimethoxymethylsilane, 3-isocyanatopropyltriethoxysilane, isocyanatomethyltrimethoxysilane, isocyanatomethyltriethoxysilane, isocyanatomethyldimethoxymethylsilane and the like. These silane coupling agents can be used alone or in combination of two or more. Further, these silane coupling agents may be commercially available products or synthetic products.

[0042] The polyoxyalkylene having a weight average molecular weight of 20,000 or more is not particularly limited, and examples thereof include polyoxyethylene, polyoxypropylene, polyoxybutylene, polyoxytetramethylene, polyoxyethylene-polyoxypropylene diblock copolymer, polyoxypropylene-polyoxytetramethylene diblock copolymer, polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer and the like. The bonding form of the copolymer may be any of random, alternating, block, and periodic.

[0043] These polyoxyalkylenes can be used alone or in combination of two or more. Further, the polyoxyalkylene may be a commercially available product or a synthetic product. Among these polyoxyalkylenes, polyoxyethylene is preferred from the viewpoint that the effects of the present invention can be easily obtained.

[0044] The reaction between the above silane coupling agent and polyoxyalkylene is not particularly limited and can be carried out, for example, without a solvent or in an organic solvent. Examples of organic solvents that can be used include, for example, aliphatic hydrocarbons such as hexane, heptane, octane, etc.; aromatic hydrocarbons such as benzene, toluene, xylene, etc.; alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, etc.; aprotic polar solvents such as dimethylformamide (DMF), dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, etc.; halogenated hydrocarbons such as chloroform, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, trifluoromethylbenzene, etc.; chain or cyclic ethers such as diethyl ether, diisopropyl ether, dimethoxyethane, tetrahydrofuran (THF), dioxane, etc.; esters such as ethyl acetate, butyl acetate, etc.; chain ketones such as methyl ethyl ketone (MEK), methyl isobutyl ketone, etc.; nitriles such as acetonitrile, etc.

[0045] By mixing the silane coupling agent and polyoxyalkylene, a surface modifier can be obtained. As a mixing method, a method of adding and mixing the silane coupling agent to polyoxyalkylene is preferable. In this case, regarding the addition form of the silane coupling agent, it may be added all at once, added in portions, or added continuously. The addition rate in the case of continuous addition can be adjusted as appropriate. When polyoxyalkylene is in a solid state, polyoxyalkylene may be heated before this mixing to make it liquid and then the mixing may be carried out.

[0046] The stirring speed during mixing is not particularly limited and can be set as appropriate. The mixing time is preferably 15 minutes or more and 2 hours or less.

[0047] The reaction temperature after mixing is preferably 20°C or higher and 200°C or lower, more preferably 50°C or higher and 150°C or lower. Also, the reaction time after mixing is preferably 1 hour or longer and 50 hours or shorter, more preferably 2 hours or longer and 30 hours or shorter. The reaction atmosphere may be any of, for example, an air atmosphere, a nitrogen atmosphere, an argon atmosphere, or other inert gas atmospheres. The pressure during the reaction may also 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).

[0048] The mixing molar ratio of the silane coupling agent to polyoxyalkylene (silane coupling agent / polyoxyalkylene) is preferably 0.5 or more and 1.5 or less.

[0049] In this way, the surface modifier according to the present invention can be obtained. The structure of the obtained surface modifier can be confirmed by measuring the infrared absorption spectrum by, for example, the total reflection method (ATR method) using a Fourier transform infrared spectrophotometer (FT-IR). The details of this method are described in the examples.

[0050] After performing this step, isolation and purification of the surface modifier may be carried out, or the next step (reacting colloidal silica with the surface modifier) may be carried out without isolation and purification.

[0051] <Step of reacting colloidal silica with the surface modifier> This step is a step of reacting the surface modifier obtained above with colloidal silica to obtain the surface-modified colloidal silica according to the present invention. The above colloidal silica has silanol groups on its surface, and these silanol groups serve as reaction sites to form siloxane bonds with the surface modifier.

[0052] The surface modifier (silane coupling agent containing a polyoxyalkylene chain) is preferably a compound represented by the following formula (1’). The surface modifier may be used alone or in combination of two or more.

[0053] [Chemical formula]

[0054] In the above formula (1’), R 1 , R 2 , X, and n are the same as those exemplified and described in the above formulas (1) to (3), respectively, and the preferred embodiments are also the same. When using two or more compounds represented by the above formula (1’), the plurality of R 1 , R 2 , X, and n may be the same or different from each other.

[0055] In the above formula (1’), R 7 each independently represents an aliphatic hydrocarbon group having 1 to 3 carbon atoms. Examples of the aliphatic hydrocarbon group having 1 to 3 carbon atoms include linear or branched alkyl groups such as methyl group, ethyl group, propyl group, and isopropyl group; linear or branched alkenyl groups such as vinyl group, allyl group, and propenyl group; and alkynyl groups such as ethynyl group and propynyl group. Among them, a linear or branched alkyl group is preferred.

[0056] This step is preferably carried out in a solvent. Examples of the solvent include water and / or the organic solvents exemplified in the above (step of synthesizing the polyoxyalkylene chain-containing silane coupling agent). The solvent may be used alone or in combination of two or more.

[0057] A mixed solution containing colloidal silica, a surface modifier, and a solvent is reacted while stirring in a reaction vessel. The ratio of the colloidal silica to the surface modifier to be subjected to the reaction is appropriately selected according to the desired degree of surface modification. As an example of the ratio of the colloidal silica to the surface modifier, the amount of the surface modifier used is preferably 0.1 part by mass or more and 10 parts by mass or less, more preferably 0.5 part by mass or more and 5 parts by mass or less, based on 100 parts by mass of the colloidal silica.

[0058] The method of mixing colloidal silica and the surface modifier is not particularly limited, but a method of adding and mixing the surface modifier to the colloidal silica is preferred. In this case, regarding the addition form of the colloidal silica, it may be added all at once, added in portions, or added continuously. The stirring speed during mixing is not particularly limited and can be set as appropriate.

[0059] The reaction temperature is preferably 20°C or higher and 200°C or lower, more preferably 30°C or higher and 150°C or lower. Also, the reaction time is preferably 1 hour or longer and 50 hours or shorter, more preferably 2 hours or longer and 30 hours or shorter. The reaction atmosphere may be any of, for example, an air atmosphere, a nitrogen atmosphere, an argon atmosphere, or other inert gas atmospheres. The pressure during the reaction may be any of normal pressure (under 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 (under atmospheric pressure), it is preferable to carry out the reaction under normal pressure (under atmospheric pressure).

[0060] In the above manner, the surface-modified colloidal silica of the present invention is obtained.

[0061] When the obtained surface-modified colloidal silica contains a dispersion medium other than water, the dispersion medium other than water may be replaced with water if necessary. The method of replacing the dispersion medium other than water with water is not particularly limited, and examples include a method of dropping water little by little while heating the surface-modified colloidal silica. Also, a method of separating the surface-modified colloidal silica from the dispersion medium other than water by precipitation / separation, centrifugation, etc., and then redispersing it in water is also included.

[0062] The method for producing the surface-modified colloidal silica according to the present invention may further include other steps. Examples of such other steps include a step of filtering a dispersion liquid containing the surface-modified colloidal silica, a step of mixing a dispersion liquid containing the surface-modified colloidal silica with other additives (preferably a pH adjuster), a step of further filtering after mixing other additives, and the like.

[0063] The structure of the surface-modified colloidal silica according to the present invention can be confirmed, for example, 29 by detecting the T2 component (the form of the above formula (2)) and the T3 component (the form of the above formula (3)) using Si-NMR. In this specification, T means an Si atom having three bonding hands bonded to O atoms and one bonding hand bonded to a polyoxyalkylene chain, and the numbers 2 and 3 mean the number of Si—O—Si bonds in which the Si atom is involved. For example, the T2 component means a component having an Si atom involved in two Si—O—Si bonds among the Si atoms having three bonding hands bonded to O atoms. In the unmodified colloidal silica, the T2 component and the T3 component bonded to the polyoxyalkylene chain are not detected, but in the surface-modified colloidal silica of the present invention, the T2 component and the T3 component are detected. Details of this detection method are described in the examples.

[0064] The surface-modified colloidal silica of the present invention modifies the surface of the colloidal silica in which the surface-modifying group according to the present invention is hydrophilic, whereby it shows affinity for both water and organic solvents and can have high dispersibility. Further, the wettability with respect to various polishing objects is improved. Therefore, it can be suitably used in various fields such as polishing abrasive grains for CMP, inorganic fillers, inorganic binders, polymer material modifiers, polymer flocculants, adsorbents, paint additives, hard coat agents, anti-slip agents, anti-reflection agents for optical films, metal surface treatment agents, heat-resistant agents, antistatic agents, catalyst carriers, and organosols. Hereinafter, a polishing composition containing the surface-modified colloidal silica of the present invention will be described.

[0065] [Polishing composition] The surface-modified colloidal silica obtained by the above production method is suitably used as a polishing abrasive grain. That is, according to a preferred embodiment of the present invention, there is provided a polishing composition containing the surface-modified colloidal silica of the present invention and a dispersion medium.

[0066] Examples of the dispersion medium contained in the polishing composition include water and / or the organic solvents exemplified in the above (step of synthesizing the polyoxyalkylene chain-containing silane coupling agent). The dispersion medium may be used alone or in combination of two or more.

[0067] The surface-modified colloidal silica contained in the polishing composition according to the present embodiment exhibits a function as an abrasive grain. The content of the surface-modified colloidal silica 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 with respect to the total mass of the polishing composition. Also, the content of the surface-modified colloidal silica is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less with respect to the total mass of the polishing composition. That is, the content of the surface-modified colloidal 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 with respect to the total mass of the polishing composition.

[0068] The polishing composition according to the present embodiment may further contain known additives that can be used in a polishing composition, such as a water-soluble polymer, a pH adjuster, a complexing agent, a preservative, and a fungicide, as long as the effects of the present invention are not inhibited.

[0069] The polishing composition according to the present embodiment is suitably used for polishing objects to be polished, such as single-crystalline silicon, polycrystalline silicon (polysilicon), silicon nitride, silicon carbonitride (SiCN), silicon oxide, metal, SiGe, and resin. The object to be polished may be composed of only one kind of material or a combination of two or more kinds of materials.

[0070] Examples of the object to be polished containing silicon oxide include, for example, TEOS type silicon oxide surface (hereinafter, also simply referred to as "TEOS") generated using tetraethyl orthosilicate as a precursor, 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.

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

Examples

[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] (Example) 150 g of polyoxyethylene (PEO20,000, manufactured by Fujifilm Wako Pure Chemical Corporation, solid) having a weight average molecular weight (Mw) of 20,000 was placed in a 1000 mL airtight heat-resistant container and heated and dissolved in an 80 ° C atmosphere air bath for 20 hours. After 20 hours had elapsed, the container was placed on an 80 ° C hot plate, the lid was removed, and stirring was performed at 300 rpm using a stirring bar. During stirring, 1.5 g of 3-isocyanatopropyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was introduced at a rate of 0.2 g / sec. After the introduction, stirring was continued at 300 rpm for another 1 hour. It was sealed again and returned to an air bath at 80 ° C, and heated for 20 hours to obtain the target surface modifier 1.

[0074] Separately, 800 g of an aqueous solution of high-purity colloidal silica (average secondary particle diameter: 70 nm, synthesized by the sol-gel method) with a concentration of 10% by mass was collected in a 1000 mL flask and heated to a liquid temperature of 60 °C using a mantle heater. After reaching 60 °C, while stirring the aqueous solution at 100 rpm, 1.5 g of the surface modifier 1 obtained above was added. Further, while maintaining the liquid temperature at 60 °C using a mantle heater, stirring was carried out at 100 rpm for 2 hours to obtain the target surface-modified colloidal silica 1.

[0075] When the modification amount (content) of PEO20,000 with respect to the total mass of the obtained surface-modified colloidal silica 1 was calculated, it was 0.19% by mass.

[0076] (Comparative Example 1) 150 g of polyoxyethylene (PEO10,000, manufactured by Merck KGaA, solid) with a weight-average molecular weight (Mw) of 10,000 was separately placed in a 1000 mL airtight heat-resistant container and heated and dissolved in an 80 °C atmosphere air bath for 20 hours. After 20 hours, the container was placed on an 80 °C hot plate as a whole, the lid was removed, and stirring was carried out at 300 rpm using a stirring bar. During stirring, 3.0 g of 3-isocyanatopropyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was added at a rate of 0.2 g / sec. After the addition, stirring was continued at 300 rpm for another 1 hour. It was sealed again and returned to an 80 °C atmosphere air bath and heated for 20 hours to obtain the target surface modifier 2.

[0077] Separately, 800 g of an aqueous dispersion of high-purity colloidal silica (average secondary particle diameter: 70 nm, synthesized by the sol-gel method) with a concentration of 10% by mass was collected in a 1000 mL flask and heated to a liquid temperature of 60 °C using a mantle heater. After reaching 60 °C, while stirring the aqueous solution at 100 rpm, 0.75 g of the surface modifier 2 obtained above was added. Further, while maintaining the liquid temperature at 60 °C using a mantle heater, stirring was carried out at 100 rpm for 2 hours to obtain the target surface-modified colloidal silica 2.

[0078] When the modification amount (content) of PEO10,000 with respect to the total mass of the obtained surface-modified colloidal silica 2 was calculated, it was 0.09% by mass.

[0079] (Comparative Example 2) 21 g of polyethylene glycol with a weight average molecular weight of 200 (PEG200, manufactured by Fujifilm Wako Pure Chemical Corporation, liquid) was separately placed in a 1000 mL airtight heat-resistant container, and the container was placed on an 80°C hot plate as a whole. The lid was removed, and stirring was carried out at 300 rpm using a stirring paddle. During stirring, 20 g of 3-isocyanatopropyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was added at a rate of 0.2 g / sec. After the addition, stirring was continued at 300 rpm for another 1 hour. It was sealed again and placed in an air bath at 80°C and heated for 20 hours to obtain the target surface modifier 3.

[0080] Separately, 800 g of an aqueous solution of high-purity colloidal silica (average secondary particle diameter: 70 nm, synthesized by the sol-gel method) with a concentration of 10% by mass was prepared by collecting it in a 1000 mL flask and heating the liquid temperature to 60°C with a mantle heater. After reaching 60°C, 0.03 g of the surface modifier 3 obtained above was added while stirring the aqueous solution at 100 rpm. Further, while maintaining the liquid temperature at 60°C using a mantle heater, stirring was carried out at 100 rpm for 2 hours to obtain the target surface-modified colloidal silica 3.

[0081] When the modification amount (content) of PEG200 with respect to the total mass of the obtained surface-modified colloidal silica 3 was calculated, it was 0.002% by mass.

[0082] (Comparative Example 3) Surface-modified colloidal silica 4 was obtained in the same manner as in Comparative Example 1, except that the input amount of the surface modifier 2 was changed to 1.5 g.

[0083] When the modification amount (content) of PEO10,000 with respect to the total mass of the obtained surface-modified colloidal silica 2 was calculated, it was 0.19% by mass.

[0084] (Comparative Example 4) Except that the amount of the surface modifier 3 was changed to 3.1 g, surface-modified colloidal silica 4 was obtained in the same manner as in Comparative Example 2.

[0085] When the modification amount (content) of PEG200 with respect to the total mass of the obtained surface-modified colloidal silica 4 was calculated, it was 0.19% by mass.

[0086] (Comparative Example 5) 150 g of polyoxyethylene having a weight average molecular weight of 20,000 (PEO20,000, manufactured by Fujifilm Wako Pure Chemical Corporation, solid) was separately placed in a 250 mL airtight heat-resistant container and heated and dissolved in an 80 °C atmosphere air bath for 20 hours.

[0087] Separately, 800 g of an aqueous solution of high-purity colloidal silica (average secondary particle diameter: 70 nm, synthesized by the sol-gel method) with a concentration of 10% by mass was prepared by collecting it in a 1000 mL flask and heating it to a liquid temperature of 60 °C with a mantle heater. After reaching 60 °C, 1.485 g of the PEG20,000 heated and dissolved above was added while stirring the aqueous solution at 100 rpm. Thereby, a mixture of polyethylene glycol and colloidal silica as the target was obtained.

[0088] [Evaluation] [Structural confirmation of the surface modifier] Regarding the surface modifier 1 obtained above, structural confirmation was performed using the following FT-IR apparatus: Apparatus used: Fourier transform infrared spectrometer (Spectrum100, manufactured by PerkinElmer) Detection method: ATR (Attenuated Total Reflection) method.

[0089] Specifically, 1 g was sampled from the reaction system 10 minutes after the addition of 3-isocyanatopropyltrimethoxysilane in the above Example. The obtained sample was placed on the ATR measurement crystal of Spectrum100, and the FT-IR spectrum was measured. As a result, 2260 cm -1It was confirmed that there was a peak of isocyanate groups derived from the silane coupling agent in the vicinity.

[0090] Furthermore, when the reaction was completed, 1 g was sampled from the reaction system. The obtained sample was placed on the ATR crystal of Spectrum100, and the FT-IR spectrum was measured. As a result, at around 2260 cm -1 It was confirmed that the peak of the isocyanate group derived from the silane coupling agent disappeared in the vicinity. From this, it was confirmed that the surface modifier 1 in which polyoxyethylene and the silane coupling agent were combined was generated.

[0091] Also, for the surface modifiers 2 and 3 obtained in Comparative Examples 1 and 2 above, sampling was performed both after 10 minutes and after the reaction was completed in the same manner as the sampling for the surface modifier 1 above, and FT-IR measurement was performed in the same manner as above. As a result, it was confirmed that the peak of the isocyanate group derived from the silane coupling agent at around 2260 cm -1 disappeared after the reaction was completed, and it was confirmed that the target surface modifiers 2 and 3 were generated.

[0092] <Confirmation of the Structure of Surface-Modified Colloidal Silica> The structure of the surface-modified colloidal silica was confirmed using the following 29 Si-NMR apparatus. Specifically, in the synthesis of the surface-modified colloidal silica 1 of the example, two measurement model samples were prepared in the same manner except that the amounts of the silane coupling agent and polyoxyalkylene were increased, and Si-NMR was measured using these model samples. 29 Model sample B is a sample with a larger amount of silane coupling agent and polyoxyalkylene than model sample A. Also, for comparison, unmodified colloidal silica was prepared.

[0093] ≪ 29 Si-NMR Apparatus ≫ Spectrometer: AVANCE300 (manufactured by Bruker) Observed nucleus: 29 Si (resonance frequency 59.6 MHz) Measurement method: CP / MAS method (manufactured by Bruker, standard pulse sequence cp.av used) ·MAS condition: 3.5 kHz Waiting time: 4 seconds Contact time: 8 milliseconds Number of integrations: Model sample A: 80,000 times Model sample B: 65,536 times Surface-untreated colloidal silica: 4,096 times Measurement temperature: Room temperature (actual measured value 24 °C).

[0094] 29 As a result of performing Si-NMR measurement, the presence of T2 component and T3 component was confirmed in both model sample A and model sample B. On the other hand, in the surface-untreated colloidal silica, the presence of T2 component and T3 component could not be confirmed. From this, it was confirmed that the target surface-modified colloidal silica was obtained by the synthesis method of the example.

[0095] <Wettability> The surface-modified colloidal silica aqueous dispersions prepared in the above examples and comparative examples 1 to 3, and the mixed silica aqueous solution prepared in comparative example 5 were respectively dispensed into beakers, and silicon wafers cut into 2 cm × 5 cm squares were each immersed for 30 seconds. After pulling up the silicon wafers, they were rubbed for 30 seconds using a wiping cloth. Then, the silicon wafers were immersed in a beaker filled with pure water and washed for 30 seconds while gently shaking. After washing, the silicon wafers were pulled up, and the wet state of the surface was visually observed, and the wettability was evaluated according to the following criteria. If the evaluation is ○, it is practical: ○ (Good): More than 70% of the entire surface of the silicon wafer maintains a wet state △ (Partially defective): More than 50% and less than 70% of the silicon wafer maintains a wet state × (Defective): Less than 50% of the silicon wafer maintains a wet state.

[0096] Note that since the sample of Comparative Example 4 was partially gelled, its wettability could not be evaluated.

[0097] (Stability over time) 100 g each of the surface-modified colloidal silica aqueous dispersions prepared in the Examples and Comparative Examples 1 to 4, and the mixture prepared in Comparative Example 5 were separately placed in different sealed containers (volume: 100 mL) and allowed to stand at room temperature (25°C) for 24 hours. After 24 hours, the sedimentation state and whether the silica sol had changed to a gel were visually observed, and the stability over time of the surface-modified colloidal silica was evaluated according to the following criteria. If the evaluation is ○, it is practical: ○ (Good): No change compared to the start of standing △ (Slightly poor): Some sedimentation was confirmed × (Poor): Severe sedimentation

[0098] The evaluation results of wettability and stability over time are shown in Table 1 below.

[0099]

Table 1

[0100] As is clear from Table 1 above, it was found that the surface-modified colloidal silica of the Examples was excellent in both wettability and stability over time. On the other hand, it was found that the surface-modified colloidal silica of Comparative Examples 1 to 5 was inferior in at least one of the performances of wettability and stability over time.

Claims

1. Colloidal silica, a surface modification group having a polyoxyalkylene chain with a weight average molecular weight of 20,000 or more, which surface-modifies the colloidal silica, A surface-modified colloidal silica comprising: The surface modification group contains a urethane bond, and the surface-modified colloidal silica.

2. The polyoxyalkylene chain is at least one selected from the group consisting of a polyoxyethylene chain, a polyoxypropylene chain, a polyoxyethylene-polyoxypropylene chain, and a polyoxyethylene-polyoxypropylene-polyoxyethylene chain. The surface-modified colloidal silica according to Claim 1.

3. The polyoxyalkylene chain is a polyoxyethylene chain. The surface-modified colloidal silica according to Claim 1 or 2.

4. Colloidal silica, a surface modification group having a polyoxyalkylene chain with a weight average molecular weight of 20,000 or more, which surface-modifies the colloidal silica, A surface-modified colloidal silica comprising: a dispersion medium, A polishing composition comprising:

5. The polyoxyalkylene chain is at least one selected from the group consisting of a polyoxyethylene chain, a polyoxypropylene chain, a polyoxyethylene-polyoxypropylene chain, and a polyoxyethylene-polyoxypropylene-polyoxyethylene chain. The polishing composition according to Claim 4.

6. The polyoxyalkylene chain is a polyoxyethylene chain. The polishing composition according to Claim 4 or 5.

7. The surface modification group contains a urethane bond. The polishing composition according to any one of Claims 4 to 6.

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