Polishing composition, its use and method for producing a substrate

Abstract

Polishing composition comprising water, abrasive grains consisting of silicon dioxide, and a water-soluble polymer having a weight-average molecular weight of 1,000,000 or less and a molecular weight distribution, represented by the weight-average molecular weight (Mw) / number-average molecular weight (Mn), of less than 5.0, wherein the water-soluble polymer comprises at least one selected from a cellulose derivative, a starch derivative, polyvinyl alcohol, a polymer having a polyvinyl alcohol structure, a polymer having a polyoxyalkylene structure, and a polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof; wherein the polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof is selected from: (i) a nonionic polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof; or (ii) the group consisting of: a polymer containing monomer units of the N-(meth)acryloyl type, a polymer containing monomer units of the N-vinyl type, a homopolymer of a vinyl monomer with an amino group, and a copolymer of a vinyl monomer with an amino group, wherein the polymer, containing monomer units of the N-(meth)acryloyl type, is a homopolymer of a monomer of the N-(meth)acryloyl type or a copolymer of a monomer of the N-(meth)acryloyl type, wherein the monomer of the N-(meth)acryloyl type is a chain amide with an N-(meth)acryloyl group or a cyclic amide with an N-(meth)acryloyl group, wherein the chain amide with the N-(meth)acryloyl group is an N-alkyl(meth)acrylamide or an N,N-dialkyl(meth)acrylamide, wherein the polymer, containing monomer units of the N-vinyl type, is a homopolymer of an N-vinyllactam type monomer, a copolymer of an N-vinyllactam type monomer, a homopolymer of an N-vinyl chain amide or a copolymer of an N-vinyl chain amide, where the N-vinyl chain amide is N-vinylacetamide, N-vinylpropionamide or N-vinylbutyramide, and where the vinyl monomer with the amino group is aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate or N,N-dimethylaminopropyl(meth)acrylate.

Description

[0001] The present invention relates to a polishing composition, its use and a method for producing a substrate using the polishing composition. State of the art

[0002] A polishing composition containing a water-soluble polymer is used for polishing a substrate, such as a silicon substrate. The water-soluble polymer serves to improve the wettability of the substrate surface, thereby reducing the amount of foreign matter remaining on the substrate surface. Patent document 1 discloses a polishing composition containing a water-soluble polymer or the like, which increases the polishing speed and reduces the degree of turbidity. Patent document 2 discloses a CMP abrasive comprising a cerium oxide slurry containing cerium oxide particles, a dispersant, and water, as well as a liquid additive containing a dispersant and water; and a liquid additive for the CMP abrasive. A method for polishing a substrate is also disclosed.Patent document 3 discloses a water-based dispersing element for chemical-mechanical polishing, consisting of a water-soluble anionic functional group including a polymer and fine particles. The anionic functional group, which contains a polymer, is composed of a structural unit derived from a monocarboxylic acid-monoethylene unsaturated monomer with 3 to 6 carbon atoms. Patent document 4 discloses a polishing slurry containing a dispersing agent for abrasive grains, consisting of a non-alkylphenol polyether compound and an inorganic rust inhibitor.Patent document 5 discloses a colloidal dispersion for chemical-mechanical polishing, comprising: (a) an abrasive component; and (b) in an amount of about 0.05% to about 10% by weight of the abrasive component, a water-soluble amphoteric polymer comprising at least one macromolecular chain B and a part A attached to a single end of the at least one macromolecular chain B, wherein the macromolecular chain B is derived from one or more ethylene unsaturated monomers, and wherein the part A is a polymeric or non-polymeric group comprising at least one anionic group. State-of-the-art documents, patent documents

[0003] Patent document 1: WO 2003 / 072669 A2 Patent document 2: US 2004 / 0 147 206 A1 Patent document 3: JP 2003- 303 791 A Patent document 4: JP 2001- 240 850 A Patent document 5: US 2010 / 0 081 281 A1 Summary of the invention: Problems solved by the invention

[0004] Surface defects, known as light-point defects (LPDs), can occur on the substrate surface polished with a polishing composition. The present invention is based on the observation that the weight-mean molecular weight and molecular weight distribution, represented by the weight-mean molecular weight (Mw) / number-mean molecular weight (Mn) of the water-soluble polymer contained in the polishing composition, correlate with the degree of LPD reduction. Patent document 1 does not relate to such a correlation.

[0005] It is an object of the present invention to provide a polishing composition and a method for producing a substrate which reduce the LPD on a polished surface. The expression "reduce LPD" means that the number and size of the LPD are reduced. Means to solve the problem

[0006] To achieve the above objective, the polishing composition of the present invention comprises water, abrasive grains consisting of silicon dioxide, and a water-soluble polymer having a weight-average molecular weight of 1,000,000 and a molecular weight distribution represented by the weight-average molecular weight (Mw) / number-average molecular weight (Mn) of less than 5.0, wherein the water-soluble polymer comprises at least one selected from a cellulose derivative, a starch derivative, polyvinyl alcohol, a polymer having a polyvinyl alcohol structure, a polymer having a polyoxyalkylene structure, and a polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof; wherein the polymer with a nitrogen atom in a main chain or in a functional group of a side chain is selected from: (i) a nonionic polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof; or (ii) the group consisting of: a polymer containing monomer units of the N-(meth)acryloyl type, a polymer containing monomer units of the N-vinyl type, a homopolymer of a vinyl monomer with an amino group, and a copolymer of a vinyl monomer with an amino group, wherein the polymer, containing monomer units of the N-(meth)acryloyl type, is a homopolymer of a monomer of the N-(meth)acryloyl type or a copolymer of a monomer of the N-(meth)acryloyl type, wherein the monomer of the N-(Meth)acryloyl type is a chain amide with an N-(Meth)acryloyl group or a cyclic amide with an N-(Meth)acryloyl group, wherein the chain amide with the N-(meth)acryloyl group is an N-alkyl(meth)acrylamide or an N,N-dialkyl(meth)acrylamide, wherein the polymer, containing monomer units of the N-vinyl type, is a homopolymer of an N-vinyllactam type monomer, a copolymer of an N-vinyllactam type monomer, a homopolymer of an N-vinyl chain amide or a copolymer of an N-vinyl chain amide, where the N-vinyl chain amide is N-vinylacetamide, N-vinylpropionamide or N-vinylbutyramide, and where the vinyl monomer with the amino group is aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate or N,N-dimethylaminopropyl(meth)acrylate.

[0007] The polishing composition is preferably used in an application for polishing a substrate.

[0008] Preferably, the polishing composition is used in an application for fine or final polishing of a substrate.

[0009] Preferably, a method for producing a substrate of the present invention comprises a polishing step for polishing a substrate with the above polishing composition. Effects of the invention

[0010] The present invention slightly reduces LPD on a polished surface. Embodiments of the invention

[0011] The following describes embodiments of the present invention.

[0012] The polishing composition according to the invention comprises water, abrasive grains consisting of silicon dioxide, and a water-soluble polymer having a weight-average molecular weight of 1,000,000 or less and a molecular weight distribution represented by the weight-average molecular weight (Mw) / number-average molecular weight (Mn) of less than 5.0, wherein the water-soluble polymer comprises at least one selected from a cellulose derivative, a starch derivative, polyvinyl alcohol, a polymer having a polyvinyl alcohol structure, a polymer having a polyoxyalkylene structure, and a polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof; wherein the polymer with a nitrogen atom in a main chain or in a functional group of a side chain is selected from: (i) a nonionic polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof; or (ii) the group consisting of: a polymer containing monomer units of the N-(meth)acryloyl type, a polymer containing monomer units of the N-vinyl type, a homopolymer of a vinyl monomer with an amino group, and a copolymer of a vinyl monomer with an amino group, wherein the polymer, containing monomer units of the N-(meth)acryloyl type, is a homopolymer of a monomer of the N-(meth)acryloyl type or a copolymer of a monomer of the N-(meth)acryloyl type, wherein the monomer of the N-(meth)acryloyl type is a chain amide with an N-(meth)acryloyl group or a cyclic amide with an N-(meth)acryloyl group, wherein the chain amide with the N-(meth)acryloyl group is an N-alkyl(meth)acrylamide or an N,N-dialkyl(meth)acrylamide, wherein the polymer, containing monomer units of the N-vinyl type, is a homopolymer of an N-vinyllactam type monomer, a copolymer of an N-vinyllactam type monomer, a homopolymer of an N-vinyl chain amide or a copolymer of an N-vinyl chain amide, where the N-vinyl chain amide is N-vinylacetamide, N-vinylpropionamide or N-vinylbutyramide, and wherein the vinyl monomer with the amino group is aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, or N,N-dimethylaminopropyl(meth)acrylate. The polishing composition of the present invention is used in an application for polishing a substrate, such as a silicon substrate or a compound semiconductor substrate. A method for polishing a substrate comprises, for example, pre-polishing (e.g., primary polishing or secondary polishing), whereby the surface of a disk-shaped substrate cut from a single-crystal cast block is flattened, and fine or finish polishing, whereby fine irregularities are removed from the surface of the substrate after the pre-polishing step to give the surface a mirror finish. The polishing composition is suitable for both pre-polishing and finish polishing the substrate.The polishing compound is also suitable for use in finishing the substrate.

[0013] The polishing composition contains abrasive grains consisting of silicon dioxide and water as other components besides the water-soluble polymer and may also contain a basic compound. <Wasserlösliches Polymer>

[0014] The water-soluble polymer serves to increase the wettability of the polished surface. A water-soluble polymer with a low molecular weight distribution (MDP) simply reduces the MDP. As described above, the MDP of the water-soluble polymer used in the polishing composition is less than 5.0, preferably 4.9 or less, more preferably 4.8 or less, more preferably 4.7 or less, and most preferably 4.6 or less. Theoretically, the MDP of the water-soluble polymer is 1.0 or more. As the MDP of the water-soluble polymer increases, the wettability of the polished surface also increases.

[0015] The molecular weight distribution of the water-soluble polymer is also referred to as a polydispersity index (PDI). The weight-mean molecular weight (Mw) is expressed in polyethylene oxide equivalents. The values ​​of the weight-mean molecular weight, number-mean molecular weight, and molecular weight distribution are obtained by gel permeation chromatography (GPC).

[0016] For the purposes of claim 1, the water-soluble polymer may be one that has at least one functional group in the molecule, selected from cationic groups, anionic groups, and nonionic groups. The water-soluble polymer may, for example, have a hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, an amide structure, a quaternary nitrogen structure, a heterocyclic structure, a vinyl structure, or a polyoxyalkylene structure in the molecule.

[0017] Examples of water-soluble polymers include, for example, a cellulose derivative such as hydroxyethylcellulose, a starch derivative such as pullulan or cyclodextrin, an imine derivative such as poly(N-acylalkylenemine), polyvinyl alcohol, a copolymer containing polyvinyl alcohol as part of its structure, polyvinylpyrrolidone, a copolymer containing polyvinylpyrrolidone as part of its structure, polyvinylcaprolactam, a copolymer containing polyvinylcaprolactam as part of its structure, polyalkylacrylamide, polyacryloylmorpholine, a copolymer containing polyacryloylmorpholine as part of its structure, polyoxyethylene, a polymer with a polyoxyalkylene structure, and a polymer with a variety of these structures in the form of the di-block, tri-block, random, or alternating type.

[0018] Methods for obtaining water-soluble polymers with a small molecular weight distribution (Mw / Mn) include living anionic polymerization, living cationic polymerization, and living radical polymerization. The living radical polymerization method is suitable because it allows the polymerization of various types of monomers and imposes fewer restrictions on industrial processes.

[0019] Examples of living radical polymerization processes include polymerization using a nitroxide compound, radical atom transfer polymerization, and polymerization using a chain transfer agent (RAFT agent), such as a dithioester compound.

[0020] Monomers that can be used for living radical polymerization include, for example, (meth)acrylates, styrene derivatives, acrylamide derivatives comprising cyclic amides, vinyl acetate, olefins, and various functional monomers containing a hydroxyl group, an alkoxysilyl group, an amino group, an epoxide group, and the like. Any of the water-soluble (hydrophilic) polymers obtained using one or more of these monomers can be an object of the present invention.

[0021] The water-soluble polymers can be used alone or in a combination of two or more.

[0022] If at least one water-soluble polymer selected from cellulose derivatives and starch derivatives (hereinafter referred to as "water-soluble polymer A") is used as the water-soluble polymer, the molecular weight distribution of the water-soluble polymer A is preferably 4.7 or less and more preferably 4.5 or less. For the sake of improving wettability, the molecular weight distribution of the water-soluble polymer A is preferably 2.0 or more, more preferably 3.0 or more, and more preferably 4.0 or more.

[0023] When a polymer with a polyoxyalkylene structure (hereinafter referred to as "water-soluble polymer B") is used as the water-soluble polymer, the molecular weight distribution of the water-soluble polymer B is preferably 2.0 or less and more preferably 1.5 or less. The molecular weight distribution of the water-soluble polymer B is preferably 1.05 or more.

[0024] When using at least one water-soluble polymer selected from polyvinyl alcohol and a polymer with a polyvinyl alcohol structure (hereinafter referred to as "water-soluble polymer C") as the water-soluble polymer, the molecular weight distribution of the water-soluble polymer C is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.3 or less. The molecular weight distribution of the water-soluble polymer C is preferably 1.05 or more, and more preferably 1.3 or more, from the perspective of improving wettability and enabling simple synthesis.

[0025] When the polymer with a nitrogen atom in the main chain or in a functional group of the side chain (hereinafter referred to as "water-soluble polymer D") is used as the water-soluble polymer, the molecular weight distribution of the water-soluble polymer D is preferably 4.0 or less, more preferably 3.5 or less, and even more preferably 3.0 or less. The molecular weight distribution of the water-soluble polymer D is preferably 1.05 or more, and more preferably 1.3 or more, from the perspective of improving wettability and enabling simple synthesis.

[0026] The weight-average molecular weight of the water-soluble polymer is 1,000,000 or less. This slightly reduces the LPD (liquid per unit mass). A decrease in the weight-average molecular weight of the water-soluble polymer increases the stability of the polishing compound. An increase in the weight-average molecular weight of the water-soluble polymer increases the wettability of the polished surface.

[0027] The weight-average molecular weight of the water-soluble polymer A is preferably 750,000 or less, more preferably 700,000 or less, even more preferably 500,000 or less, and particularly preferably 300,000 or less. The weight-average molecular weight of the water-soluble polymer A is preferably 50,000 or more, more preferably 80,000 or more, and even more preferably 100,000 or more.

[0028] The weight-average molecular weight of the water-soluble polymer B is preferably 500,000 or less, more preferably 300,000 or less, and even more preferably 250,000 or less (e.g., 100,000 or less). The weight-average molecular weight of the water-soluble polymer B is preferably 1,000 or more, more preferably 2,000 or more, and even more preferably 5,000 or more (e.g., 10,000 or more).

[0029] The weight-average molecular weight of the water-soluble polymer C is preferably 300,000 or less, more preferably 250,000 or less, even more preferably 200,000 or less, and particularly preferably 100,000 or less (for example, 50,000 or less, and furthermore 20,000 or less). The weight-average molecular weight of the water-soluble polymer C is preferably 1,000 or more, more preferably 2,000 or more, and more preferably 5,000 or more (for example, 7,000 or more).

[0030] The weight-average molecular weight of the water-soluble polymer D is preferably 300,000 or less, more preferably 250,000 or less, and even more preferably 200,000 or less (for example, 100,000 or less, and furthermore 70,000 or less). The weight-average molecular weight of the water-soluble polymer D is preferably 1,000 or more, more preferably 3,000 or more, even more preferably 5,000 or more, and particularly preferably 10,000 or more (for example, 20,000 or more, and furthermore 30,000 or more).

[0031] From the point of view of reducing LPD, the polishing composition preferably comprises at least one selected from the water-soluble polymers A and C and further preferably comprises at least one selected from the water-soluble polymers A and C and at least one from the water-soluble polymers B and D.

[0032] Examples of water-soluble polymer A include, for example, a cellulose derivative such as hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, or carboxymethylcellulose, and a starch derivative such as pullulan or cyclodextrin. Among the cellulose and starch derivatives, hydroxycellulose is particularly preferred due to its high ability to provide wettability to the polished surface and its ease of removal during the washing step after polishing (i.e., good washing power).

[0033] The water-soluble polymer B is preferably a polymer with a block structure comprising an oxyethylene block and an oxypropylene block, further preferably a polymer with a triblock structure comprising an oxyethylene block and an oxypropylene block, and an oxyethylene block, and even more preferably a polymer represented by the following general formula (1): HO-(EO) a -(PO) b -(EO) c -H (1)

[0034] In the general formula (1) EO represents an oxyethylene group, PO represents an oxypropylene group and a, b and c each represent an integer of 1 or more.

[0035] In general formula (1), a and c represent the degree of polymerization of EO, and the sum of a and c is preferably in the range of 2 to 1,000, more preferably in the range of 5 to 500, and even more preferably in the range of 10 to 200. In general formula (1), b represents the degree of polymerization of PO and is preferably in the range of 2 to 200, more preferably in the range of 5 to 100, and even more preferably in the range of 10 to 50.

[0036] Examples of water-soluble polymer C include polyvinyl alcohol and a polymer containing at least one vinyl alcohol unit. A polymer containing at least one vinyl alcohol unit and one vinyl acetate unit can, for example, be used as the polymer containing at least one vinyl alcohol unit. An example of a water-soluble polymer C includes a water-soluble polymer formed by the partial saponification of a homopolymer or copolymer of vinyl acetate. The partially saponified polyvinyl alcohol formed by the saponification of a vinyl acetate homopolymer is preferably used.The partially saponified polyvinyl alcohol is a water-soluble polymer consisting of a vinyl alcohol unit and a vinyl acetate unit, and the degree of saponification is preferably at least 50 mol% or more, more preferably 60 mol% or more, for example 65 mol% or more, even more preferably 70 mol% or more, and particularly preferably 80 mol% or more. The degree of saponification of the polyvinyl alcohol is theoretically 100 mol% or less. If, in addition, a copolymer with a polyvinyl alcohol structure is used as the water-soluble polymer C, the percentage of the component (molar ratio) of the vinyl alcohol units forming the copolymer is preferably 65 mol% or more and more preferably 75 mol%. As used here, the term “Copolymer” is a generic term encompassing various copolymers, such as a random copolymer, alternating copolymer, block copolymer and graft copolymers, unless otherwise stated.

[0037] The water-soluble polymer D can be a polymer containing a nitrogen atom in the main chain and a polymer containing a nitrogen atom in a functional group of the side chain (side group).

[0038] Examples of the polymer with a nitrogen atom in the main chain include a homopolymer and a copolymer of the N-acylalkylenimine monomer. Specific examples of the N-acylalkylenimine monomer include N-acetylethyleneimine, N-propionylethyleneimine, N-caproylethyleneimine, N-benzoylethyleneimine, N-acetylpropylenimine, N-butyrylethyleneimine, and the like. The homopolymer of the N-acylalkylenimine monomer includes poly(N-acetylethyleneimine), poly(N-propionylethyleneimine), poly(N-caproylethyleneimine), poly(N-benzoylethyleneimine), poly(N-acetylpropylenimine), and poly(N-butyrylethyleneimine). The copolymer of the monomer of the N-acylalkylenimine type comprises copolymers of two or more monomers of the N-acylalkylenimine type and copolymers of monomers of the N-acylalkylenimine type and another monomer.

[0039] The polymer with a nitrogen atom in the side chain includes polymers containing monomer units of the N-(meth)acryloyl type and polymers containing a monomer unit of the N-vinyl type. Here, "(meth)acryloyl" is a general term for acrylic and methacryl.

[0040] The polymer containing an N-(meth)acryloyl-type monomer unit comprises homopolymers and copolymers of the N-(meth)acryloyl-type monomer (typically copolymers with more than 50 wt% of the N-(meth)acryloyl-type monomer). The N-(meth)acryloyl-type monomer includes chain amides with an N-(meth)acryloyl group and cyclic amides with an N-(meth)acryloyl group.

[0041] The chain amide with an N-(meth)acryloyl group comprises N-alkyl(meth)acrylamides, such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and Nn-butyl(meth)acrylamide; and Nn-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di(n-butyl)(meth)acrylamide. The polymer containing a chain amide with an N-(meth)acryloyl group as a monomer unit comprises a homopolymer of N-isopropylacrylamide (e.g., copolymers with more than 50 wt% N-isopropylacrylamide).

[0042] The cyclic amide with an N-(meth)acryloyl group comprises N-(meth)acryloylmorpholine and N-(meth)acryloylpyrrolidine. The polymer containing a cyclic amide with an N-(meth)acryloyl group as a monomer unit comprises a homopolymer of N-acryloylmorpholine and copolymers of N-acryloylmorpholine (e.g., copolymers with more than 50 wt% N-acryloylmorpholine).

[0043] The polymer containing an N-vinyl-type monomer unit includes homopolymers and copolymers of the N-vinyllactam-type monomer (e.g., copolymers with more than 50 wt% of the N-vinyllactam-type monomer) and homopolymers and copolymers of N-vinyl chain amides (e.g., copolymers with more than 50 wt% N-vinyl chain amide).

[0044] The N-vinyllactam-type monomer comprises N-vinylpyrrolidone (VP), N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam (VC), N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholindione. The polymer containing an N-vinyllactam-type monomer unit comprises polyvinylpyrrolidone (PVP), polyvinylcaprolactam, a random copolymer of VP and VC, random copolymers of one or both of VP and VC and another vinyl monomer (e.g., an acrylic monomer or a vinyl ester monomer), block copolymers, and graft polymers containing a polymer segment containing one or both of VP and VC (e.g., a graft copolymer of polyvinyl alcohol grafted with polyvinylpyrrolidone).

[0045] The N-vinyl chain amides include N-vinylacetamide, N-vinylpropionamide, and N-vinylbutyramide.

[0046] The polymer with a nitrogen atom in the side group also includes a homopolymer and a copolymer of a vinyl monomer (e.g. a monomer with a (meth)acryloyl group) with an amino group, such as aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate and N,N-dimethylaminopropyl(meth)acrylate.

[0047] If the polishing composition comprises the water-soluble polymer A and at least one selected from the water-soluble polymers B and D, from the point of view of reducing LPD, the polishing composition particularly preferably comprises hydroxyethylcellulose and at least one selected from the polymers represented by the general expression (1) described above.

[0048] If the polishing composition comprises the water-soluble polymer C and at least one selected from the water-soluble polymers B and D, from the point of view of reducing LPD, the polishing composition particularly preferably comprises polyvinyl alcohol or partially saponified polyvinyl alcohol and at least one selected from the polymers represented by the above-described general expression (1), polyvinylpyrrolidone, polyalkylacrylamides and polyacryloylmorpholine.

[0049] The content of the water-soluble polymer in the polishing composition is 0.002 wt% or more, preferably 0.004 wt% or more, even more preferably 0.006 wt% or more, and particularly preferably 0.01 wt% or more. Increasing the content of the water-soluble polymer in the polishing composition improves the wettability of the polished surface. Preferably, the content of the water-soluble polymer in the polishing composition is not more than 0.5 wt% or less, more preferably 0.2 wt% or less, even more preferably 0.1 wt% or less, and particularly preferably 0.05 wt% or less. Decreasing the content of the water-soluble polymer in the polishing composition improves the stability of the polishing composition. <Schleifkörner>

[0050] The polishing compound contains abrasive grains. These abrasive grains serve to physically polish the surface.

[0051] According to the invention, the abrasive grains consist of silicon dioxide.

[0052] Preferably, the mean primary grain size or diameter of the abrasive grains is 5 nm or more, more preferably 15 nm or more, and particularly preferably 25 nm or more. Increasing the mean primary grain size of the abrasive grains results in a higher polishing rate. Preferably, the mean primary grain size of the abrasive grains is 100 nm or less, more preferably 50 nm or less, and particularly preferably 40 nm or less. Reducing the mean primary grain size of the abrasive grains improves the stability of the polishing compound.

[0053] The mean primary grain size of the abrasive grains is calculated, for example, from the specific surface area using the BET method. Measurements of the specific surface area of ​​the abrasive grains can be performed, for example, using a Flow Sorb II 2300 (Micromeritics Instrument Corp.).

[0054] Preferably, the mean secondary grain size of the abrasive grains is 10 nm or more, more preferably 30 nm or more, and particularly preferably 40 nm or more. Increasing the mean secondary grain size of the abrasive grains can lead to a higher polishing rate. A reduction in the mean secondary grain size of the abrasive grains improves the stability of the polishing compound. The mean secondary grain size of the abrasive grains is measured using FPAR-1000 (Otsuka Electronics Co., Ltd.).

[0055] The average major / minor axis ratio of the abrasive grains is theoretically 1.0 or more, preferably 1.05 or more, and particularly preferably 1.1 or more. Increasing the average major / minor axis ratio results in a higher polishing rate. Preferably, the average major / minor axis ratio of the abrasive grains is 3.0 or less, more preferably 2.0 or less, and particularly preferably 1.5 or less. Decreasing the average major / minor axis ratio reduces the number of scratches formed on the polished surface.

[0056] Preferably, the number of abrasive grains with the major / minor axis ratios described above is 1.5 or 10% or more of the total number of abrasive grains contained in the polishing compound, and more preferably 20% or more. Increasing the percentage of grains with major / minor axis ratios of 1.5 or more simply reduces the LPD (low polishing rate). Additionally, increasing the percentage of grains with major / minor axis ratios of 1.5 or more results in a higher polishing rate. Preferably, the percentage of grains with major / minor axis ratios of 1.5 or more is 90% or less, and even more preferably 80% or less. Reducing the percentage of grains with major / minor axis ratios of 1.5 or more reduces the haze level of the polished surface.

[0057] The major axis / minor axis ratio described above is a value related to the shape of the abrasive grain and can be determined, for example, using an electron microscope image of the grain. Specifically, a minimum bounding rectangle for each abrasive grain is plotted in a scanning electron microscope image of a given number of grains (e.g., 200). Then, for each minimum bounding rectangle, the length of the longer side (major axis value) is divided by the length of the shorter side (minor axis value) to obtain the major axis / minor axis ratio. Finally, an average of the major axis / minor axis ratios is calculated to obtain the mean value of the major axis / minor axis ratios.The calculation of the principal / secondary axis ratios described above can be performed on the basis of the image obtained using a scanning electron microscope “S-4700” (Hitachi Ltd.).

[0058] Preferably, the abrasive grain content in the polishing composition is 0.05 wt% or more, more preferably 0.1 wt% or more, and even more preferably 0.2 wt% or more. Increasing the abrasive grain content results in a higher polishing rate. Preferably, the abrasive grain content in the polishing composition is 10 wt% or less, more preferably 3 wt% or less, and even more preferably 1 wt% or more. Reducing the abrasive grain content improves the stability of the polishing composition.

[0059] Silicon dioxide, which acts as the abrasive grain, is used in a suitable manner for polishing, for example, a silicon substrate. Specific examples of silicon dioxide include colloidal silicon dioxide, highly dispersed silicon dioxide, and sol-gel silicon dioxide. Among these silicon dioxides, colloidal silicon dioxide and highly dispersed silicon dioxide are particularly preferred for reducing scratches on the polished surface. The silicon dioxides can be used alone or in combination with one or more.

[0060] Preferably, the true specific gravity of silicon dioxide is 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. An increase in the true specific gravity of silicon dioxide leads to a higher polishing rate. Preferably, the true specific gravity of silicon dioxide is 2.2 or less, more preferably 2.0 or less, and even more preferably 1.9 or less. A decrease in the true specific gravity of silicon dioxide reduces the scratches that form on the polished surface. The true specific gravity of the silicon dioxide is calculated from the weight of the dried silicon dioxide grains and the total weight of the silicon dioxide grains immersed in ethanol of a known volume. <Basische Verbindung>

[0061] The polishing compound may contain a basic compound. This basic compound serves to chemically polish the surface to be polished (chemical etching). In this way, the polishing rate can be easily increased.

[0062] The basic compound includes, for example, hydroxides of an alkali metal, a quaternary ammonium compound, ammonia, and an amine. Alkali metal hydroxides include, for example, potassium hydroxide and sodium hydroxide. Quaternary ammonium hydroxide or its salts include, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. The amine includes, for example, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, and guanidine.

[0063] The basic compounds can be used alone or in combination with two or more.

[0064] Among the basic compounds, at least one selected from ammonia, an alkali metal hydroxide and a quaternary ammonium hydroxide is preferred.

[0065] Among the basic compounds, at least one selected from ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide is further preferred, at least one from ammonia and tetramethylammonium hydroxide is even more preferred and ammonia is the most preferred.

[0066] The content of the basic compound in the polishing composition is preferably 0.001 wt% or more, more preferably 0.002 wt% or more, even more preferably 0.003 wt% or more, and particularly preferably 0.005 wt% or more. Increasing the content of the basic compound in the polishing composition results in a higher polishing rate. The content of the basic compound in the polishing composition is preferably 1.0 wt% or less, more preferably 0.5 wt% or less, even more preferably 0.1 wt% or less, and particularly preferably 0.05 wt% or less. Decreasing the content of the basic compound in the polishing composition reduces the roughness of the polished surface and simply maintains the shape of the substrate. <wasser>

[0067] The water in the polishing compound serves to dissolve or disperse the other components. It is preferred that the water does not inhibit the action of the other components contained in the polishing compound. Examples of such water include, for instance, water with a total transition metal ion content of no more than 100 ppb. The purity of the water can be improved, for example, by removing the impurity ions with an ion exchange resin, by filtering, by distillation, or similar processes. In particular, the use of, for example, deionized water, pure water, ultrapure water, or distilled water is preferred. <ph-wert>

[0068] Preferably, the pH of the polishing composition is 8.0 or higher, more preferably 8.5 or higher, and particularly preferably 9.0 or higher. A higher polishing rate can be achieved with an increasing pH of the polishing composition. Preferably, the pH of the polishing composition is 12.5 or lower, even more preferably 11.5 or lower, and particularly preferably 11 or lower. Reducing the pH of the polishing composition reduces the roughness of the polished surface and allows it to easily retain the shape of the substrate. <komplexbildner>

[0069] The polishing compound may contain a complexing agent. The complexing agent traps metallic impurities in the polishing system to form complexes. This reduces the residual concentration of metallic impurities on the substrate. Examples of metallic impurities in the polishing system include impurities from the starting materials of the polishing compound, impurities generated during polishing from the polishing surface or the polishing device, and impurities from the environment. Particularly when the substrate is a semiconductor substrate, reducing the residual concentration of metallic impurities prevents metal contamination of the semiconductor substrate and limits the degradation of its quality.

[0070] The complexing agent includes, for example, a complexing agent based on aminocarboxylic acids and a complexing agent based on organic phosphonic acid. Examples of aminocarboxylic acid-based complexing agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetic acid, ammonium nitrilotriacetic acid, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate.Examples of complexing agents based on organic phosphonic acid include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, amino-tri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid and α-methylphosphonosuccinic acid. <Oberflächenaktives Mittel>

[0071] The polishing compound may contain a surfactant. The surfactant reduces the roughness of the polished surface. This facilitates the reduction of the turbidity of the polished surface. In particular, if the polishing compound contains a basic compound, the polished surface tends to become rough due to chemical etching with a basic compound. Therefore, the use of the basic compound together with the surfactant is especially effective.

[0072] The surfactant preferably has a weight-average molecular weight of less than 1000 and comprises anionic and nonionic surfactants. Nonionic surfactants are preferred. Due to its low foaming properties, the nonionic surfactant is easy to handle when preparing or using the polishing compound. Additionally, the pH of the polishing compound can be easily adjusted when using the nonionic surfactant.

[0073] The non-ionic surfactant includes, for example, oxyalkylene polymers such as polyethylene glycol and polypropylene glycol; a polyoxyalkylene adduct such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, polyoxyethylene sorbitan fatty acid esters; and a copolymer of a plurality of types of oxyalkylenes (diblock, triblock, random, alternating type).

[0074] In particular, the non-ionic surfactant comprises a polyoxyethylene polyoxypropylene copolymer, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, polyoxyethylene 2-ethylhexyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene centetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearary ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene endodecyl phenyl ether, polyoxyethylene styrenized phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene nonyl phenyl ether, polyoxyethylene endodecyl phenyl ether, polyoxyethylene styrenized phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene stearylamide. Polyoxyethylene oleylamide, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate,Polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, tetraoleic acid polyoxyethylene sorbitol, polyoxyethylene sorbitol tetraoleate, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, and the like. Among these surfactants, polyoxyethylene alkyl ethers, in particular polyoxyethylene decyl ethers, are preferably used.

[0075] The surfactant can be used alone or in combination with two or more. <Andere Bestandteile>

[0076] The polishing composition may further include known additives commonly found in polishing compositions, if required, such as an organic acid, a salt of an organic acid, an inorganic acid, salts of inorganic acids, a preservative, or an antifungal agent.

[0077] Organic acids include, for example, fatty acids such as formic acid, acetic acid, and propionic acid; aromatic carboxylic acids such as benzoic acid and phthalic acid; citric acid; oxalic acid; tartaric acid; malic acid; maleic acid; fumaric acid; succinic acid; organic sulfonic acids; and organic phosphonic acids. Salts of organic acids include, for example, alkali metal salts (e.g., sodium and potassium salts) or ammonium salts of organic acids.

[0078] Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of salts of inorganic acids include alkali metal salts (e.g., sodium and potassium salts) or ammonium salts of an inorganic acid.

[0079] Organic acids and their salts, as well as inorganic acids and their salts, can be used alone or in combination with two or more.

[0080] The preservatives and antifungal agents include, for example, an isothiazolin-based compound, p-oxybenzoate, and phenoxyethanol. <Herstellung der Polierzusammensetzung>

[0081] The polishing compound can be prepared using a known mixing device, for example, a propeller stirrer, an ultrasonic dispersion machine, or a homogenizer. The components of the polishing compound can be mixed simultaneously or in any order.

[0082] Preferably, the polishing composition is obtained by a dilution step in which a stock solution of the polishing composition is diluted with water to facilitate transport and storage. That is, it is preferred that a stock solution containing a water-soluble polymer is prepared beforehand and diluted to obtain the polishing composition.

[0083] The polishing composition of the present embodiment can also be obtained from a stock solution containing abrasive grains and the water-soluble polymer with the weight-average molecular weight and molecular weight distribution described above. Even in this case, the LPDs can be easily reduced based on the weight-average molecular weight and molecular weight distribution of the water-soluble polymer.

[0084] If the stock solution contains abrasive grains and a water-soluble polymer with the weight-average molecular weight and molecular weight distribution described above, the grains in the polishing compound produced by the dilution step will exhibit suitable dispersion. The grains comprise individual bodies of abrasive grains and an agglomerate of abrasive grains and the water-soluble polymer. The dispersion of the grains in the polishing compound can be determined based on measuring the volume-averaged grain diameter of the grains contained in the polishing compound. The volume-averaged grain size can be obtained, for example, by a dynamic light scattering method using a particle diameter size distribution measuring device (model "UPA-UT151", Nikkiso Co., Ltd.).It should be noted that the dispersibility of the grains in the polishing compound is important for reducing LPD (low powder diffusion). The water-soluble polymer described above is also advantageous in terms of improving the dispersibility of the grains. Furthermore, the use of the water-soluble polymer described above simply reduces LPD.

[0085] Preferably, the volume-averaged particle diameter of the grains contained in the polishing composition obtained by diluting the stock solution is 10 nm or more, more preferably 30 nm or more, and even more preferably 40 nm or more. Increasing the volume-averaged particle diameter can result in a higher polishing rate. Preferably, the volume-averaged particle diameter of the grains in the polishing composition obtained by diluting the stock solution is 200 nm or less, more preferably 100 nm or less, and even more preferably 80 nm or less. Decreasing the volume-averaged particle diameter simply reduces the LPD (low polishing rate).

[0086] Preferably, the dilution rate D on a volume basis during the dilution step is 2 times or more, more preferably 5 times or more, and even more preferably 10 times or more. By increasing the dilution rate D during the dilution step, it is possible to reduce the transport costs of the stock solution of the polishing composition and also to reduce the space required for storing the stock solution.

[0087] Preferably, the dilution rate D on a volume basis during the dilution step is 100-fold or less, more preferably 50-fold or less, and even more preferably 40-fold or less. Reducing the dilution rate D during the dilution step easily ensures the stability of the stock solution and the polishing composition.

[0088] The stock solution for the polishing compound can be prepared using a known mixing device, for example, a propeller stirrer, an ultrasonic dispersion machine, or a homogenizer. The materials of the stock solution for the polishing compound can be mixed simultaneously or in any order.

[0089] Preferably, the stock solution of the polishing composition is diluted by slowly adding water to the stock solution while stirring it with the mixing device described above. Alternatively, the stock solution of the polishing composition can be diluted by adding water to the stock solution before stirring the mixture with the mixing device described above during the dilution step.

[0090] A process for producing a substrate is described below, along with the effect of the polishing composition.

[0091] A substrate is produced by a process that includes a polishing step using a polishing composition. During this step, a polishing pad is pressed against the substrate surface. The substrate and polishing pad are then rotated while the polishing composition is applied to the substrate surface. During polishing, it is assumed that increased solubility or dispersion of the water-soluble polymer is achieved, as the polishing composition comprises the water-soluble polymer with a weight-average molecular weight of 1,000,000 or less and a molecular weight distribution of less than 5.0. It is therefore assumed that LPDs detected on the surface of the depolished semiconductor substrate are reduced. The substrate, after polishing, is subsequently subjected to a washing step to clean the substrate surface.

[0092] The embodiment described in detail above has the following advantages. (1) The polishing composition enables the easy reduction of LPD on the polished surface, as it contains the water-soluble polymer, having a weight-average molecular weight of 1,000,000 or less and a molecular weight distribution of less than 5.0. (2) If the polishing composition is produced in the form of a stock solution containing the abrasive grains and the water-soluble polymer, it can be easily stored and transported. (3) When the polishing composition is used in applications for polishing a substrate, it can simply provide a substrate with reduced LPD on the polished surface. (4) The polishing composition is used for fine polishing of the substrate. This contributes to improving the quality, as the LPD on the substrate are reduced after fine polishing, which is necessary for high quality. (5) The manufacturing process of a substrate facilitates the production of a substrate with reduced LPD, since the process includes the polishing step for polishing the substrate with the polishing composition which contains the water-soluble polymer with a molecular weight distribution of less than 5.0.

[0093] The embodiment described above can be modified as follows.

[0094] The molecular weight distribution (Mw / Mn) of the water-soluble polymer in the polishing compound can be adjusted, for example, by mixing a variety of water-soluble polymers with different weight-average molecular weights. That is, if the water-soluble polymer in the polishing compound consists of a variety of water-soluble polymers, the molecular weight distribution (Mw / Mn) of the water-soluble polymers as a whole only needs to be less than 5.0.

[0095] The polishing compound can be a single pack or it can be of the multi-pack type with two or more packs.

[0096] Each component contained in the polishing compound or stock solution can be filtered immediately before preparation. Furthermore, the polishing compound itself can be filtered immediately before use. Filtering the polishing compound removes coarse foreign particles and improves its quality. The polishing compound contains a water-soluble polymer with a molecular weight distribution of less than 5.0. This reduces clogging of the filter used during filtration and ensures adequate filtration.

[0097] The material and structure of the filter used in filtration are not particularly limited. Filter materials include, for example, cellulose, nylon, polysulfone, polyethersulfone, polypropylene, polytetrafluoroethylene (PTFE), polycarbonate, and glass. Filter designs include, for example, depth filters, pleated filters, and membrane filters.

[0098] The polishing pad used in the polishing process with the polishing compound is not particularly limited. For example, non-woven fabric pads, velour pads, pads containing abrasive grains, and pads without abrasive grains can all be used.

[0099] When polishing a substrate with a polishing compound, the compound used for polishing can be recovered and reused. One method for reusing the polishing compound involves, for example, recirculating the polishing compound collected in the container by the polishing device and reusing it from the tank. By reusing the polishing compound and reducing emissions, it is possible to reduce the amount of polishing compound required. This reduces the environmental impact and is beneficial because it lowers the cost of polishing a substrate.

[0100] When polishing compounds are reused, components such as the abrasive grains are lost or consumed. Therefore, the polishing compound is preferably replenished with an amount corresponding to the reduced quantity of these components. The replenished components can be added individually to the polishing compound, or alternatively, as a mixture containing two or more of the components in any concentration, depending on the container size, polishing conditions, or similar factors. By replenishing each component with an amount corresponding to the reduction in the reused polishing compound, the composition of the polishing compound is maintained, thus preserving its effectiveness.

[0101] The material of a compound semiconductor substrate subjected to polishing with the polishing composition includes silicon carbide, gallium nitride, gallium arsenide, and the like. The use of the polishing composition is not limited to semiconductor substrates. The polishing composition can also be used to polish substrates made of metals such as stainless steel, plastics, glass, or the like, and in processes for manufacturing such substrates. In this case, it is possible to easily reduce the LPD (low particle size distribution) on the polished surface. Furthermore, the polishing composition can also be used to obtain polished products made of various materials, not just substrates.

[0102] Technical concepts that can be identified from the above embodiments are described below. (a) A stock solution for dilution, used to obtain a polishing composition, wherein the stock solution contains abrasive grains and a water-soluble polymer having a weight-mean molecular weight of 1,000,000 or less, and a molecular weight distribution represented by the weight-mean molecular weight (Mw) / number-mean molecular weight (Mn) of less than 5.0. (b) A method for producing a polishing composition, wherein the method comprises producing the polishing solution by a dilution step to dilute the stock solution described above with water. (c) A polishing process comprises polishing a substrate using the polishing composition. Examples

[0103] The embodiment described above will be explained in more detail below using examples and comparative examples. (Examples 1-10 and comparison examples 1-6)

[0104] A stock solution of each polishing compound was prepared by mixing colloidal silicon dioxide, serving as the abrasive, one or more types of a water-soluble polymer, and a basic compound in deionized water. Each stock solution was then filtered to remove coarse impurities. Colloidal silicon dioxide with an average primary particle diameter of 35 nm and ammonia were used as the abrasive and the basic compound, respectively. The stock solution was subsequently diluted 20-fold with pure water to obtain a polishing compound containing a water-soluble polymer listed in Table 1. A homogenizer was used in the dilution step to perform stirring and dispersion. The polishing compound was then filtered to remove coarse impurities.

[0105] The proportion of abrasive grains in the polishing composition of the examples and the comparison examples was 0.5 wt.% and the proportion of the basic compound was 0.01 mass-%.

[0106] In the column “water-soluble polymer” in Table 1, “Mw” indicates the weight-mean molecular weight, “Mn” indicates the number-mean molecular weight, “Mw / Mn” denotes the molecular weight distribution, and the conditions for gel permeation chromatography (GPC) were as follows: <GPC Bedingungen> Column: TSKgel (trade name) GMPW XL × 2 + G2500PW XL (7.8mΦ × 300mm × 3) (Tosoh Corporation), Column temperature: 40°C, Eluent: aqueous solution of 200 mM sodium nitrate, Sample concentration: 0.05% by mass Flow rate: 1.0 ml / min, Injection volume: 200 µl Detector: RI (differential refractometer), Standard reference material: Polyethylene oxide

[0107] In the "water-soluble polymer" column of the table, "HEC" in the "Type" column indicates hydroxyethylcellulose, "PVP" indicates polyvinylpyrrolidone, and "PEO-PPO-PEO" indicates polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer. Here, "PEO-PPO-PEO" is a water-soluble polymer represented by the general formula (1), in which the sum of a and c is 164 and b is 31. Furthermore, "PVA1" indicates polyvinyl alcohol with a degree of saponification of 80 mol%, and "PVA2" indicates polyvinyl alcohol with a degree of saponification of 98 mol% or more. <polierschritt>

[0108] The final polishing was performed on a silicon substrate using the obtained polishing compound under the conditions shown in Table 2. The silicon substrate subjected to fine polishing was pre-polished using a commercially available abrasive (Glanzox-1103 (trade name), Fujimi Co. Inc.). The silicon substrate had a diameter of 300 mm, a p-type conductor, and a <100> Crystal orientation and a resistance of 0.1 Ω·cm or more and less than 100 Ω·cm. <waschschritt>

[0109] Each silicon substrate was washed after polishing using a cleaning solution consisting of NH4OH (29%) : H2O2 (31%) : deionized water (DIW) = 1:3:30 (volume ratio) (SC-1 cleaning). Specifically, a first cleaning tank, a second cleaning tank, and a rinsing tank were prepared, each equipped with an ultrasonic oscillator operating at a frequency of 300 kHz. The first and second cleaning tanks were filled with the cleaning solution described above and maintained at 60°C. The rinsing tank was filled with ultrapure water. After polishing, each silicon substrate was immersed in the cleaning solution of the first cleaning tank, and the ultrasound was activated for 6 minutes. The silicon substrate was then immersed in the ultrapure water in the rinsing tank and rinsed using ultrasonic waves.The silicon substrate was then immersed in the cleaning solution of the second cleaning tank and subjected to ultrasound for 6 minutes. <Bestimmung der LPD>

[0110] The LPDs were determined by counting the number of particles 0.037 µm or larger on the surface of each silicon substrate after polishing, using a wafer inspection device (Surfscan SP2 (trade name), KLA-Tencor Corporation). In the "LPD" column of Table 1, "A", "B", "C", "D", and "E" indicate the number of particles: less than 100, 100 or more and less than 150, 150 or more and less than 200, 200 or more and less than 300, and 300 or more. <Bestimmung des Trübungsgrades>

[0111] The turbidity level of each silicon wafer was determined based on measurements of the polished surface after the polishing process, using a wafer inspection instrument (Surfscan SP2 (trade name), manufactured by KLA-Tencor Corporation) in the instrument's DWO mode. Cases where the measured values ​​were less than 0.110 ppm, 0.110 ppm or more, less than 0.120 ppm, 0.120 ppm or more, less than 0.130 ppm, 0.130 ppm or more, less than 0.140 ppm, and 0.140 ppm or more were rated as "A", "B", "C", "D", and "E", respectively. The rating results are shown in Table 1 in the "Turbidity" column. Table 1 Water-soluble polymer LPD Turbidity Mw Mn Mw / Mn Art Salary (mass-%) Example 1 250000 60000 4,2 HEC 0,01 B A Example 2 500000 120000 4,2 HEC 0,01 B A Example 3 75000 200000 3,8 HEC 0,01 B B Example 4 250000 60000 4,2 HEC 0,01 A A 22000 8000 2,8 PvP 0,004 Example 5 250000 60000 4,2 HEC 0,01 A A 10000 9000 1,1 PEO-PPO-PEOPVP 0,003 Example 6 100000 67000 1,5 EOPO Random Copolymer 0,005 B A Example 7 60000 22000 2,7 PVA1 0,017 A A Example 8 75000 22000 3,4 Polyisopropylacrylamide 0,008 A B Example 9 78000 28000 2,8 Polyacrylolylmorpholine 0,008 A B Example 10 160000 470000 3,4 Polyacrylolylmorpholine 0,007 A A 60000 200000 3,0 PVA2 0,007 Comparative example 1 670000 900000 7,5 HEC 0,01 E B Comparative example 2 1050000 190000 5,5 HEC 0,01 D B Comparative example 3 1200000 200000 6,0 HEC 0,01 D D Comparative example 4 1100000 230000 4,8 HEC 0,01 C D Comparative example 5 1200000 260000 4,6 HEC 0,01 C D Comparative example 6 800000 90000 8,9 EOPO Random Copolymer 0,005 E B Polishing conditions Polishing device: Plate polishing machine (PNX-332B (product name), Okamoto Machine Tool Works, Ltd.) Polishing load: 15 kPa Roller rotation speed: 30 RPM Head rotation speed: 30 RPM Polishing pad: POLYAS (trade names) 27NX (Fujibo Holdings, Inc.) Polishing time: 4 minutes Temperature of the polishing compound: 20°C Feed rate of the polishing compound: 500ml / min (pouring onto the substrate)

[0112] As shown in Table 1, the measurement result in each example was A or B. In comparison examples 1 and 6, the LPD measurement results were worse than the results of each example because the molecular weight distribution of the water-soluble polymers used was 5.0 or higher. In comparison examples 2 and 3, the LPD measurement results were worse than the results of each example because the weight-mean molecular weight of the water-soluble polymer used exceeded 1,000,000 and the molecular weight distribution was 5.0 or higher. In comparison examples 4 and 5, the LPD measurement results were worse than the results of each example because the weight-mean molecular weight of the water-soluble polymers used exceeded 1,000,000, even though their molecular weight distribution was less than 5.0.< / waschschritt> < / polierschritt> < / komplexbildner> < / wasser>

Claims

[1] A polishing composition comprising water, abrasive grains consisting of silica, and a water-soluble polymer having a weight-average molecular weight of 1,000,000 or less and a molecular weight distribution represented by the weight-average molecular weight (Mw) / number-average molecular weight (Mn) of less than 5.0, wherein the water-soluble polymer comprises at least one selected from a cellulose derivative, a starch derivative, polyvinyl alcohol, a polymer having a polyvinyl alcohol structure, a polymer having a polyoxyalkylene structure, and a polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof; wherein the polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof is selected from: (i) a non-ionic polymer having a nitrogen atom in a main chain or in a functional group of a side chain thereof; or (ii) the group consisting of: a polymer containing monomer units of the N-(meth)acryloyl type, a polymer containing monomer units of the N-vinyl type, a homopolymer of a vinyl monomer having an amino group, and a copolymer of a vinyl monomer with an amino group, wherein the polymer containing N-(meth)acryloyl-type monomer units is a homopolymer of an N-(meth)acryloyl-type monomer or a copolymer of an N-(meth)acryloyl-type monomer, wherein the N-(meth)acryloyl type monomer is a chain amide having an N-(meth)acryloyl group or a cyclic amide having an N-(meth)acryloyl group, wherein the chain amide with the N-(meth)acryloyl group is an N-alkyl(meth)acrylamide or an N,N-dialkyl(meth)acrylamide, wherein the polymer containing N-vinyl-type monomer units is a homopolymer of an N-vinyllactam-type monomer, a copolymer of an N-vinyllactam-type monomer, a homopolymer of an N-vinyl chain amide, or a copolymer of an N-vinyl chain amide, wherein the N-vinyl chain amide is N-vinylacetamide, N-vinylpropionamide or N-vinylbutyramide, and wherein the vinyl monomer having the amino group is aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate or N,N-dimethylaminopropyl (meth)acrylate. [2] Use of the polishing composition according to claim 1 in polishing a substrate. [3] Use of the polishing composition according to claim 2 in carrying out fine polishing of a substrate. [4] A method for producing a substrate comprising a polishing step of polishing a substrate using the polishing composition according to claim 1.