Polishing composition and method for polishing silicon wafers

Abstract

A polishing composition is provided that can further reduce microdefects and haze on a semiconductor wafer after polishing, and also has good ability to hydrophilize the semiconductor wafer. The polishing composition comprises abrasive particles, a basic compound, and a water-soluble polymer which is a copolymer of vinylpyrrolidone polymerized in a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (A). However, R1, R2, and R3 each independently represent a hydrogen atom or an organic group, X represents a single bond or a bonded chain, and R4, R5, and R6 each independently represent a hydrogen atom or an organic group.

Description

Technology Field

[0001] The present invention relates to a polishing composition and a method for polishing a silicon wafer. Background Technology

[0002] The polishing of semiconductor wafers by CMP achieves high-precision smoothing and planarization by performing multi-stage polishing in three or four stages. The finishing polishing process performed in the final stage is primarily intended to reduce micro-defects or haze (surface blurring).

[0003] Polishing compositions used in the final polishing process of semiconductor wafers generally contain water-soluble polymers such as hydroxyethylcellulose (HEC). Water-soluble polymers play a role in hydrophilizing the surface of semiconductor wafers and suppress damage to the semiconductor wafers caused by the adhesion of abrasive particles to the surface, excessive chemical etching, and aggregation of abrasive particles. It is known that this can reduce micro-defects and haze.

[0004] Since HEC is derived from natural cellulose, it may contain water-insoluble impurities of cellulose origin. Consequently, micro-defects may occur in polishing compositions containing HEC due to the influence of these impurities. Furthermore, HEC with molecular weights ranging from hundreds of thousands to millions is frequently used; however, as the molecular weight increases, filter clogging becomes more likely, and liquid passage becomes difficult in filters with small pore diameters. Therefore, when using water-soluble polymers with high molecular weights, it becomes difficult to remove coarse particles. Additionally, aggregation of abrasive particles becomes more likely, raising concerns regarding the long-term stability of the polishing composition.

[0005] Japanese Patent Publication No. 2012-216723 discloses a polishing composition comprising at least one water-soluble polymer selected from vinyl alcohol-based resins having 1,2-diol structural units.

[0006] Japanese Patent Publication No. 2009-147267 discloses a chemical mechanical polishing abrasive containing a polymer in which vinylpyrrolidone is graft-polymerized onto polyvinyl alcohol.

[0007] International Publication No. 2013 / 137212 discloses a polishing composition comprising abrasive particles and a water-soluble polymer, wherein the water-soluble polymer is a copolymer composed of a first monomer unit having excellent wettability properties for a silicon substrate and a second monomer unit having excellent adsorption properties for the abrasive particles.

[0008] International Publication No. 2018 / 043504 discloses a polishing composition comprising abrasive particles, a water-soluble polymer, and a basic compound, wherein the water-soluble polymer comprises a copolymer having a vinyl alcohol unit and an N-vinyl type monomer unit in one molecule. Prior art literature

[0009] Japanese Patent Publication No. 2012-216723, Japanese Patent Publication No. 2009-147267, International Publication No. 2013 / 137212, International Publication No. 2018 / 043504 The problem to be solved

[0010] Recently, as the miniaturization of design rules for semiconductor devices progresses, stricter management is required for micro-defects or haze on the surface of semiconductor wafers.

[0011] A polishing composition using a copolymer of polyvinyl alcohol and vinylpyrrolidone (hereinafter referred to as "PVA-PVP") as a water-soluble polymer is known. On the other hand, PVA-PVP has a problem in that its ability to hydrophilize semiconductor wafers is inferior compared to, for example, polyvinyl alcohol.

[0012] The objective of the present invention is to provide a polishing composition that can further reduce micro-defects and haze of a semiconductor wafer after polishing, and also has good ability to hydrophilize the semiconductor wafer. means of solving the problem

[0013] A polishing composition according to one embodiment of the present invention comprises abrasive particles, a basic compound, and a water-soluble polymer which is a copolymer of vinylpyrrolidone polymerized in a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (A).

[0014]

[0015] However, R 1 , R 2 , and R 3 Each independently represents a hydrogen atom or an organic group, X represents a single bond or bond chain, and R 4 , R 5 , and R 6 Each represents a hydrogen atom or an organic group independently. Effects of the invention

[0016] According to the present invention, a polishing composition is obtained that can further reduce micro-defects and haze of a semiconductor wafer after polishing, and also has good ability to hydrophilize the semiconductor wafer. Specific details for implementing the invention

[0017] The inventors conducted various studies to solve the above problems. As a result, it was found that by using a copolymer in which vinylpyrrolidone is polymerized into a vinyl alcohol-based resin having 1,2-diol structural units as a water-soluble polymer, the wettability characteristics, which are a problem when using conventional PVA-PVP, are improved, and a polishing composition with excellent overall balance is obtained.

[0018] The present invention was completed based on this finding. Below, a polishing composition according to one embodiment of the present invention will be described in detail.

[0019] A polishing composition according to one embodiment of the present invention comprises abrasive particles, a basic compound, and a water-soluble polymer which is a copolymer of vinylpyrrolidone polymerized in a vinyl alcohol-based resin having 1,2-diol structural units.

[0020] The abrasive particles may be those commercially available in this field, such as colloidal silica, fumed silica, colloidal alumina, fumed alumina, and ceria, and colloidal silica or fumed silica are particularly preferred. The particle size of the abrasive particles is not particularly limited, but, for example, a secondary average particle size of 30 to 100 nm may be used. The lower limit of the secondary average particle size of the abrasive particles is preferably 50 nm, and more preferably 80 nm. The upper limit of the secondary average particle size of the abrasive particles is preferably 90 nm.

[0021] The content of abrasive particles is not particularly limited, but is, for example, 0.10 to 20 mass% of the total polishing composition. The polishing composition is used by diluting it 10 to 40 times, for example, during polishing. It is preferable to use the polishing composition according to the present embodiment by diluting it so that the concentration of abrasive particles is 100 to 5000 ppm (mass ppm; hereinafter the same). The lower limit of the concentration of abrasive particles after dilution is preferably 1000 ppm, and more preferably 1500 ppm. The upper limit of the concentration of abrasive particles after dilution is preferably 4000 ppm, and more preferably 3500 ppm.

[0022] Basic compounds react efficiently with the wafer surface and contribute to the polishing characteristics of chemical mechanical polishing (CMP). Basic compounds include, for example, amine compounds and inorganic alkali compounds.

[0023] Amine compounds are, for example, primary amines, secondary amines, tertiary amines, quaternary ammoniums and their hydroxides, heterocyclic amines, etc. Specifically, examples include ammonia, tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, hexylamine, cyclohexylamine, ethylenediamine, hexamethylenediamine, diethylenetriamine (DETA), triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, monoethanolamine, diethanolamine, triethanolamine, N-(β-aminoethyl)ethanolamine, piperazine anhydrous, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, piperazine hydrochloride, guanidine carbonate, etc.

[0024] Examples of inorganic alkali compounds include alkali metal hydroxides, alkali metal salts, alkaline earth metal hydroxides, and alkaline earth metal salts. Specifically, inorganic alkali compounds include potassium hydroxide, sodium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate.

[0025] The above-described basic compounds may be used alone or in a mixture of two or more. Among the above-described basic compounds, alkali metal hydroxides, alkali metal salts, ammonia, amines, ammonium salts, and quaternary ammonium hydroxides are particularly preferred.

[0026] The content of the basic compound (the total amount if two or more types are contained) is not particularly limited, but for example, in terms of mass ratio with the abrasive particles, the abrasive particle:basic compound = 1:0.01 to 1:0.10. It is preferable to use the polishing composition according to the present embodiment by diluting it so that the concentration of the basic compound is 15 to 300 ppm.

[0027] The water-soluble polymer included in the polishing composition according to the present embodiment is a copolymer in which vinylpyrrolidone is polymerized to a vinyl alcohol-based resin having 1,2-diol structural units. Hereinafter, the vinyl alcohol-based resin having 1,2-diol structural units is referred to as "diol-modified PVA." In addition, the copolymer in which vinylpyrrolidone is polymerized to diol-modified PVA is referred to as "modified PVA-PVP."

[0028] The diol modified PVA in modified PVA-PVP is a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (1).

[0029]

[0030] However, R 1 , R 2 , and R 3 Each independently represents a hydrogen atom or an organic group, X represents a single bond or bond chain, and R 4 , R 5 , and R 6 Each represents a hydrogen atom or an organic group independently.

[0031] "Vinyl alcohol-based resin" refers to a water-soluble polymer comprising structural units represented by the following formulas (2) and (3).

[0032]

[0033] Diol-modified PVA has a 1,2-diol structural unit represented by Formula (1) in addition to the structural units represented by Formulas (2) and (3). By using a copolymer in which vinylpyrrolidone is polymerized into diol-modified PVA, the wettability characteristics, which are a problem when using conventional PVA-PVP, are improved. Since diol-modified PVA has a higher hydrogen bonding strength compared to ordinary PVA, the polymer itself is easily adsorbed onto the wafer, or the bonding strength with water molecules is strengthened (i.e., the water molecule capture ability is improved), so when the polymer protects the wafer, the hydrophilicity retention is increased, and consequently, the wettability characteristics for the wafer are improved. The modification amount of the 1,2-diol structural unit in the polymer is not particularly limited, but is, for example, 1 to 20 mol%.

[0034] Diol-modified PVA is R in the 1,2-diol structural unit represented by general formula (1). 1 ~R 6 It is particularly desirable that all of these are hydrogen atoms and that X is a single bond. That is, it is particularly desirable to include the structural unit of the following formula (4).

[0035]

[0036] Modified PVA-PVP may be any of random copolymers, alternating copolymers, block copolymers, and graft copolymers.

[0037] The weight-average molecular weight of the modified PVA in the modified PVA-PVP is not particularly limited, but for example, 0.5 × 10⁻⁶ 4 ~50×10 4 The lower limit of the weight-average molecular weight of modified PVA is preferably 0.75 × 10⁻⁶. 4 and, more preferably 1.0×10 4 is, and more preferably 1.5×10 4 The upper limit of the weight-average molecular weight of modified PVA is preferably 35×10 4 and, more preferably 25×104 is, and more preferably 15×10 4 am.

[0038] The weight-average molecular weight of vinylpyrrolidone in modified PVA-PVP is not particularly limited, but is, for example, 0.2 × 10⁻⁶ 4 ~100×10 4 The lower limit of the weight-average molecular weight of vinylpyrrolidone is preferably 0.4 × 10⁻⁶. 4 and, more preferably 0.6×10 4 is, and more preferably 0.8×10 4 The upper limit of the weight-average molecular weight of vinylpyrrolidone is preferably 50×10 4 and, more preferably 25×10 4 is, and more preferably 10×10 4 am.

[0039] Among these, a graft copolymer in which vinylpyrrolidone is graft-polymerized onto the main chain of diol-modified PVA is particularly suitable. This is because, by making it a graft copolymer, the volume increases compared to the straight-chain case, and the molecular structure becomes spatially wider, which is thought to make it easier to capture water molecules or improve adsorption to abrasives or wafers.

[0040] A graft copolymer of diol-modified PVA and vinylpyrrolidone can be prepared, for example, by incorporating N-vinyl-2-pyrrolidone into a solution of diol-modified PVA and polymerizing N-vinyl-2-pyrrolidone into the diol-modified PVA using a suitable polymerization initiator. Examples of polymerization initiators may include hydrogen peroxide, organic peroxides, azo-based initiators, etc.

[0041] In this case, it is preferable that the average degree of polymerization of the diol-modified PVA forming the main chain be 200 to 3000. More preferably, the average degree of polymerization of the diol-modified PVA is 200 to 2000, even more preferably 200 to 800, and even more preferably 300 to 600.

[0042] In addition, the diol-modified PVA that forms the main chain can be prepared, for example, by saponifying a copolymer of a vinyl ester monomer and a compound represented by the following general formula (5).

[0043]

[0044] However, R 1 , R 2 , and R 3 Each independently represents a hydrogen atom or an organic group, X represents a single bond or bond chain, and R 4 , R 5 , and R 6 Each independently represents a hydrogen atom or an organic group, and R 7 , and R 8 Each independently consists of a hydrogen atom or R 9 -CO-(R 9 represents an alkyl group having 1 to 4 carbon atoms.

[0045] In the graft copolymer, the amount of vinylpyrrolidone relative to the diol-modified PVA is preferably 5 to 500 parts by weight of vinylpyrrolidone per 100 parts by weight of the diol-modified PVA.

[0046] It is preferable that the modified PVA-PVP has a degree of polymerization of the modified PVA main chain of 200 to 800, and the concentration of a 4% aqueous solution measured at 25°C is 11 mPa·s or less.

[0047] In modified PVA-PVP, the degree of polymerization of PVP cannot be measured using the same method as with conventional PVA-PVP (a copolymer in which vinylpyrrolidone is polymerized onto a vinyl alcohol-based resin that does not possess 1,2-diol structural units). Specifically, in conventional PVA-PVP, the degree of polymerization of PVP can be measured by separating the homopolymer (free PVP) using a solvent that dissolves only the homopolymer from the PVA-PVP. However, in the case of modified PVA-PVP, a method for selecting an appropriate solvent to separate only the homopolymer has not been established. Therefore, it is difficult to measure the exact amount of PVP polymerized in diol-modified PVA.

[0048] In this embodiment, the viscosity of the aqueous solution of modified PVA-PVP is used as an indicator of the amount of PVP polymerized in the diol-modified PVA. The lower the amount of PVP polymerized in the diol-modified PVA, the lower the viscosity of the aqueous solution of modified PVA-PVP. The concentration of the 4% aqueous solution of modified PVA-PVP measured at 25°C is more preferably 10 mPa·s or less, more preferably 9 mPa·s or less, and even more preferably 8 mPa·s or less.

[0049] The content of modified PVA-PVP (the total amount if two or more types are contained) is not particularly limited, but, for example, in terms of mass ratio with abrasives, abrasives:modified PVA-PVP = 1:0.001 to 1:0.30. The lower limit of the mass ratio of modified PVA-PVP to abrasives is preferably 0.004 and more preferably 0.008. The upper limit of the mass ratio of modified PVA-PVP to abrasives is preferably 0.20 and more preferably 0.10.

[0050] The polishing composition according to the present embodiment is preferably used by diluting the modified PVA-PVP to a concentration of 20 to 200 ppm. The lower limit of the concentration of the modified PVA-PVP after dilution is preferably 35 ppm, and more preferably 50 ppm. The upper limit of the concentration of the modified PVA-PVP after dilution is preferably 150 ppm, and more preferably 120 ppm.

[0051] The polishing composition according to the present embodiment may further include a nonionic surfactant. By including a nonionic surfactant, micro-defects or haze can be further reduced.

[0052] Examples of nonionic surfactants suitable for the polishing composition according to the present embodiment include ethylenediaminetetrapolyoxyethylenepolyoxypropylene (poloxamine), poloxamer, polyoxyalkylene alkyl ether, polyoxyalkylene fatty acid ester, polyoxyalkylene alkylamine, polyoxyalkylene methylglucoside, alcohol ethoxylate, oxo-alcohol ethoxylate, etc.

[0053] Examples of polyoxyalkylene alkyl ethers include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, and polyoxyethylene stearyl ether. Examples of polyoxyalkylene fatty acid esters include polyoxyethylene monolaurate and polyoxyethylene monostearate. Examples of polyoxyalkylene alkylamines include polyoxyethylene laurylamine and polyoxyethylene oleylamine. Examples of polyoxyalkylene methyl glucosides include polyoxyethylene methyl glucoside and polyoxypropylene methyl glucoside.

[0054] The content of nonionic surfactants (the total amount if two or more types are contained) is not particularly limited, but for example, in terms of mass ratio with abrasives, abrasives:nonionic surfactant = 1:0.00001 to 1:0.015. It is preferable to use the polishing composition according to the present embodiment by diluting it so that the concentration of the nonionic surfactant is 0.1 to 30 ppm.

[0055] The polishing composition according to the present embodiment may further include a pH adjusting agent. The pH of the polishing composition according to the present embodiment is preferably 8.0 to 12.0.

[0056] In addition to the above, the polishing composition according to the present embodiment may optionally incorporate a compounding agent generally known in the field of polishing compositions.

[0057] The polishing composition according to the present embodiment is prepared by appropriately mixing abrasive particles, a basic compound, modified PVA-PVP, and other compounding materials, and adding water. Alternatively, the polishing composition according to the present embodiment is prepared by sequentially mixing abrasive particles, a basic compound, modified PVA-PVP, and other compounding materials with water. As a means for mixing these components, means commonly used in the technical field of polishing compositions, such as a homogenizer or ultrasound, are used.

[0058] The polishing composition described above is diluted with water to a suitable concentration and then used for polishing semiconductor wafers.

[0059] The polishing composition according to the present embodiment can be suitably used for polishing silicon wafers (bare wafers), particularly for finishing polishing. A method for polishing a silicon wafer according to one embodiment of the present invention comprises polishing a silicon wafer using the polishing composition above.

[0060] [Example]

[0061] The present invention will be explained more specifically below by way of examples. The present invention is not limited to these examples.

[0062] Polishing compositions of Examples 1 to 23 and Comparative Examples 1 to 6 shown in Table 1 were prepared.

[0063]

[0064] The contents in Table 1 are the contents after full dilution. Colloidal silica with average secondary particle diameters of 70 nm and 87 nm was used for the abrasives. "NH4OH" represents an aqueous ammonia solution.

[0065] Modified PVA-PVP (1) to (4) in the “Type” column of water-soluble polymers are graft copolymers in which N-vinyl-2-pyrrolidone is graft polymerized onto a butanediol vinyl alcohol polymer with a degree of polymerization: 450 and a degree of saponification: 98 mol% or more (complete saponification). In modified PVA-PVP (1) to (4), the molecular weight of N-vinyl-2-pyrrolidone polymerized onto the main chain butanediol vinyl alcohol polymer is different, and the molecular weight decreases in the order of (1), (2), (3), and (4). When the viscosity of 4% aqueous solutions of modified PVA-PVP (1) to (4) was measured at 25°C, the viscosity was 11 mPa·s, 10 mPa·s, 9 mPa·s, and 8 mPa·s, respectively.

[0066] As water-soluble polymers other than modified PVA-PVP, a copolymer (PVA-PVP) in which vinylpyrrolidone is polymerized into ordinary polyvinyl alcohol (vinyl alcohol-based resin that does not have 1,2-diol structural units), butanediol vinyl alcohol polymer (modified PVA), and polyvinylpyrrolidone (PVP (1) and (2)) were used.

[0067] PVA-PVP is a copolymer formed by graft polymerization of vinylpyrrolidone (N-vinyl-2-pyrrolidone) onto a vinyl alcohol polymer with a degree of saponification of 98 mol% or higher (fully saponified). The weight-average molecular weight of this PVA-PVP branch PVP is approximately 8.0 × 10⁻⁶. 4 (K value: approximately 40)

[0068] Modified PVA is a butanediol polymer with a degree of polymerization: 450 and a degree of saponification: 98 mol% or more (complete saponification). PVP (1) is polyvinylpyrrolidone with a K value of 17. PVP (2) is polyvinylpyrrolidone with a K value of 30.

[0069] Nonionic surfactant S1 is an alcohol ethoxylate (RO-(CH2CH2O)nH, where R is a hydrocarbon group with 6 carbon atoms and n is around 5) with a weight average molecular weight of 300. Nonionic surfactant S2 is an oxo-alcohol ethoxylate (RO-(CH2CH2O)nH, where R is a hydrocarbon group with 13 carbon atoms and n is 8) with a weight average molecular weight of 550. Nonionic surfactant S3 is a polyoxypropylene methylglucoside with a weight average molecular weight of 775.

[0070] Polishing of a 12-inch silicon wafer was performed using the polishing compositions of these examples and comparative examples. The silicon wafer used was of the P-type conductivity type with a resistivity of 0.1 Ωcm or higher and less than 100 Ωcm. The polishing surface was set to the <100> surface. The polishing device used was an SPP800S single-sided polishing device manufactured by Okamoto Machine Tool Works, Ltd. A suede pad was used as the polishing pad. The polishing composition was diluted 31 times and supplied at a feed rate of 1 L / min. The rotation speed of the platen was 40 rpm, the rotation speed of the carrier was 39 rpm, and the polishing load was 100 gf / cm². 2 Polishing was performed for 3 minutes. In addition, prior to polishing with the polishing compositions of the examples and comparative examples, preliminary polishing was performed for 2 minutes using the polishing slurry Nanopure (registered trademark) NP7050S (manufactured by Nitta Haas Incorporated).

[0071] Microdefects and haze of the silicon wafer after polishing were measured. Microdefects were measured using the wafer surface inspection device MAGICS M5640 (manufactured by Lasertec Corporation). Haze was measured using the wafer surface inspection device Surfscan SP2 (manufactured by KLA-Tencor Corporation). In addition, haze was measured in DWO mode. The results are shown in the "Defect" and "Haze" columns of Table 1 described above. The values ​​in the columns are relative values ​​when Comparative Example 1 is set to 100.

[0072] In addition, the wettability of the silicon wafer after polishing was evaluated. Specifically, the surface of the silicon wafer after polishing was rinsed with flowing water (DIW) for 15 seconds, and then the silicon wafer was placed upright and set in a stationary position. The wettability of each silicon wafer was evaluated 5 seconds after setting. It was evaluated as “○” if the distance of the water-repellent portion from the outer periphery on the polished surface was less than 5 mm, and as “×” if it was 5 mm or more. The results are shown in the “Wafer Wetness” column of Table 1 described above.

[0073] From the comparison of Examples 1 to 3 with Comparative Example 1, the comparison of Example 15 with Comparative Example 5, and the comparison of Example 16 with Comparative Example 6, it can be seen that by using modified PVA-PVP, the micro-defects, haze, and wettability characteristics are all improved compared to the case where conventional PVA-PVP is used.

[0074] From the comparison of Examples 1 to 3, the comparison of Examples 10 and 13, and the comparison of Examples 12 and 14, it can be seen that the haze of the modified PVA-PVP tends to decrease as the viscosity decreases to 4%.

[0075] From the comparison of Example 3 and Example 4, the comparison of Examples 16 with 18–21 and 23, and the comparison of Example 17 with Example 22, it can be seen that micro-defects and haze can be further reduced by including a nonionic surfactant. Also, from the comparison of Examples 20, 21 and 23, it can be seen that haze tends to be reduced by increasing the amount of the nonionic surfactant.

[0076] From a comparison of Examples 3 and 5, it can be seen that when the amount of modified PVA-PVP is reduced, microdefects and haze tend to be reduced.

[0077] From the comparison of Examples 5 and 6, Examples 8 to 10, Examples 11 and 12, and Examples 21 and 22, it can be seen that when the amount of basic compound is reduced, the haze decreases, while the number of microdefects tends to increase.

[0078] From the comparison of Examples 5, 7, and 8, it can be seen that when the amount of abrasive particles is reduced, micro-defects decrease, while haze tends to increase.

[0079] From the comparison of Examples 8 and 11, Examples 10 and 12, Examples 13 and 14, and Examples 15 and 16, it can be seen that increasing the particle size of the abrasives significantly reduces haze.

[0080] The embodiments of the present invention have been described above. The above-described embodiments are merely examples for carrying out the present invention. Accordingly, the present invention is not limited to the above-described embodiments, and it is possible to carry out the invention by appropriately modifying the above-described embodiments within the scope without departing from the spirit thereof.

Claims

Claim 1 A polishing composition comprising abrasive particles, a basic compound, and a water-soluble polymer which is a copolymer of vinylpyrrolidone polymerized into a vinyl alcohol-based resin having a 1,2-diol structural unit represented by the following general formula (A). However, R 1 , R 2 , and R 3 Each independently represents a hydrogen atom or an organic group, X represents a single bond or bond chain, and R 4 , R 5 , and R 6 Each represents a hydrogen atom or an organic group independently. Claim 2 A polishing composition according to claim 1, wherein the water-soluble polymer is a graft copolymer in which vinylpyrrolidone is graft polymerized to a vinyl alcohol-based resin having 1,2-diol structural units, the degree of polymerization of the vinyl alcohol-based resin having 1,2-diol structural units is 200 to 800, and the viscosity of a 4% aqueous solution of the water-soluble polymer measured at 25°C is 11 mPa·s or less. Claim 3 A polishing composition according to claim 2, wherein the viscosity is 9 mPa·s or less. Claim 4 A polishing composition according to any one of claims 1 to 3, wherein the basic compound is one or more selected from the group consisting of alkali metal hydroxides, alkali metal salts, ammonia, amines, ammonium salts, and quaternary ammonium hydroxides. Claim 5 A polishing composition according to any one of claims 1 to 3, further comprising a nonionic surfactant. Claim 6 In any one of claims 1 to 3, the polishing composition is a polishing composition used for polishing a silicon wafer. Claim 7 A method for polishing a silicon wafer, comprising polishing the silicon wafer using a polishing composition described in any one of claims 1 to 3.

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