JP6169938B2 - Polishing liquid composition for silicon wafer - Google Patents

Description

  The present invention relates to a polishing composition for a silicon wafer, a method for producing a semiconductor substrate using the same, and a method for polishing a silicon wafer.

  In recent years, design rules for semiconductor devices have been increasingly miniaturized due to increasing demand for higher recording capacity of semiconductor memories. For this reason, the depth of focus becomes shallower in photolithography performed in the manufacturing process of a semiconductor device, and the demands for defect reduction and smoothness of silicon wafers (bare wafers) are becoming stricter.

  In order to improve the quality of silicon wafers, polishing of silicon wafers is performed in multiple stages. In particular, the final polishing performed in the final stage of polishing is a surface defect (LPD: Light point) such as particles, scratches and pits due to suppression of surface roughness (haze) and improvement of wettability (hydrophilization) of the silicon wafer surface after polishing. This is done to reduce defects).

  As a polishing liquid composition used for final polishing, a polishing liquid composition for chemical mechanical polishing using colloidal silica and an alkali compound is known. Further, as a polishing liquid composition for the purpose of improving the haze level, a polishing liquid composition in which a water-soluble polymer compound is further added to the above polishing liquid composition has been reported (Patent Document 1).

  On the other hand, as a polishing composition for reducing the number of surface defects (LPD), a polishing composition containing a water-soluble polymer compound having a nitrogen-containing group is known (Patent Document 2). . Also, a polishing liquid composition capable of sufficiently increasing the polishing rate ratio between silicon oxide and polysilicon and applying polysilicon as a stopper, comprising a water-soluble polymer compound such as an acrylamide derivative, A polishing liquid composition that can suppress polishing of a film is disclosed (Patent Document 3). In addition, N-alkyl substitution of silica sol and acrylamide is possible as a metal polishing liquid composition that enables rapid polishing, improves flatness, hardly forms a groove between the wiring and the insulating layer, and has high storage stability. A polishing composition containing a body has been proposed (Patent Document 4).

JP 2004-128089 A JP 2008-53415 A WO2007 / 055278 JP 2008-91524 A

  The polishing composition described in Patent Document 1 contains hydroxyethyl cellulose (HEC) and polyethylene oxide (PEO) for the purpose of reducing the surface roughness (haze), but HEC is a natural raw material. Since some natural cellulose is used as a raw material, water-insoluble matter derived from cellulose is contained, and the quality is not stable. And since the said water insoluble matter becomes a nucleus and a silica particle aggregates, the storage stability of polishing liquid composition falls, and the aggregate of a silica particle increases a surface defect number (LPD). In addition, the presence of the water-insoluble matter itself may cause an increase in the number of surface defects (LPD). Therefore, it is common to filter the polishing composition immediately before use for the purpose of removing aggregates of silica particles and water-insoluble matter, but due to the dissolution of HEC, the viscosity of the polishing composition is high, Furthermore, since the filter is clogged due to the presence of water-insoluble matter, etc., the filtration accuracy must be lowered. As a result, the removal of silica particle aggregates and water-insoluble matter becomes insufficient, and silicon This causes a decrease in wafer productivity.

  Further, the polishing composition described in Patent Document 2 contains at least one water-soluble polymer selected from polyvinyl pyrrolidone and poly N-vinylformamide for the purpose of reducing surface defects (LPD). However, the polishing using this polishing composition cannot sufficiently reduce the surface roughness (haze) of the polished silicon wafer.

  Moreover, also about the polishing liquid composition of patent document 3 or patent document 4, the grinding | polishing using these polishing liquid compositions cannot fully reduce the surface roughness (haze) of the polished silicon wafer.

  Accordingly, in the present invention, a polishing composition for a silicon wafer that can reduce the surface roughness (haze) of a polished silicon wafer while ensuring a polishing rate that ensures good productivity, and for the silicon wafer. A method for producing a semiconductor substrate using a polishing composition and a method for polishing a silicon wafer are provided.

ただし、上記一般式(１)において、Ｒ¹及びＲ²はそれぞれ独立して、水素又は炭素数が１〜２のモノヒドロキシアルキル基を示し、Ｒ³は炭素数が１〜４のアルキル基、炭素数が１〜４のモノヒドロキシアルキル基、又は炭素数が１〜４のジヒドロキシアルキル基を示し、Ｒ⁴は、水素又は炭素数が１〜４のアルキル基を示し、Ｒ⁵は、水素又はメチル基を示す。ただし、上記一般式(１)で表される構成単位は、２個以上の水酸基を含む。 The polishing composition for a silicon wafer of the present invention contains the following component A and component B.
(Component A): Silica particles (Component B): a water-soluble polymer compound containing a structural unit represented by the following general formula (1) and having a weight average molecular weight of 20,000 to 1,000,000

However, in the general formula (1), R ¹ and R ² each independently represent hydrogen or a monohydroxyalkyl group having 1 to 2 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms, A monohydroxyalkyl group having 1 to 4 carbon atoms or a dihydroxyalkyl group having 1 to 4 carbon atoms, R ⁴ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ⁵ represents hydrogen or Indicates a methyl group. However, the structural unit represented by the general formula (1) contains two or more hydroxyl groups.

  The manufacturing method of the semiconductor substrate of this invention includes the grinding | polishing process of grind | polishing a silicon wafer using the polishing liquid composition for silicon wafers of this invention.

  The polishing method for a silicon wafer of the present invention includes a polishing step of polishing the silicon wafer using the polishing composition for a silicon wafer of the present invention.

ただし、上記一般式(１)において、Ｒ¹及びＲ²はそれぞれ独立して、水素又は炭素数が１〜２のモノヒドロキシアルキル基を示し、Ｒ³は炭素数が１〜４のアルキル基、炭素数が１〜４のモノヒドロキシアルキル基、又は炭素数が１〜４のジヒドロキシアルキル基を示し、Ｒ⁴は、水素又は炭素数が１〜４のアルキル基を示し、Ｒ⁵は、水素又はメチル基を示す。ただし、上記一般式(１)で表される構成単位は、２個以上の水酸基を含む。 The silicon wafer polishing additive composition of the present invention is a silicon wafer polishing additive composition used for preparing the silicon wafer polishing liquid composition of the present invention, and is represented by the following general formula (1). A water-soluble polymer compound having a weight average molecular weight of 20,000 to 1,000,000 and an aqueous medium.

However, in the general formula (1), R ¹ and R ² each independently represent hydrogen or a monohydroxyalkyl group having 1 to 2 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms, A monohydroxyalkyl group having 1 to 4 carbon atoms or a dihydroxyalkyl group having 1 to 4 carbon atoms, R ⁴ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ⁵ represents hydrogen or Indicates a methyl group. However, the structural unit represented by the general formula (1) contains two or more hydroxyl groups.

  According to the present invention, a polishing composition for a silicon wafer that can reduce the surface roughness (haze) of a polished silicon wafer while ensuring a polishing rate that ensures good productivity, and the silicon The manufacturing method of the semiconductor substrate using the polishing liquid composition for wafers, and the polishing method of a silicon wafer can be provided. Moreover, the additive composition for silicon wafer polishing used for preparation of the said polishing liquid composition for silicon wafers can be provided.

  The present invention includes a constitutional unit represented by the above general formula (1), and a water-soluble polymer compound (component B) having a weight average molecular weight of 20,000 or more and 1,000,000 or less is a polishing composition for a silicon wafer (hereinafter, In some cases, the surface roughness (haze) of the silicon wafer can be remarkably reduced while ensuring a polishing rate that ensures good productivity. Based on knowledge.

  The details of the effect expression mechanism of the present invention are not clear, but are estimated as follows. The surface roughness (haze) of a silicon wafer polished with the polishing composition is affected by cutting force proportional to the size (particle diameter) of the abrasive particles. Specifically, when the interaction between the water-soluble polymer compound used in the preparation of the polishing liquid composition and the silica particles is too strong, aggregation of the silica particles cannot be suppressed, and the storage stability of the polishing liquid composition is reduced. The particle size (dispersed particle size) of the aggregate (secondary particles) of silica particles decreases. As a result, the cutting force becomes too large, and the surface roughness of the silicon wafer is deteriorated.

  However, the water-soluble polymer compound (component B) has a predetermined weight average molecular weight, and in its constituent unit, an amide group that is a hydrophilic portion that interacts with silica particles, a silicon wafer, It includes both an alkyl group, a monohydroxyalkyl group, and a dihydroxyalkyl group, which are hydrophobic sites that interact with each other. Therefore, the water-soluble polymer compound (component B) is moderately adsorbed on both the silica particles and the silicon wafer surface. By appropriately adsorbing the water-soluble polymer compound (component B) on the silica particles, the deterioration of the surface roughness (haze) of the silicon wafer due to the aggregation of the silica particles is suppressed.

  In general, the surface charges of the silica particles and the silicon wafer are both negatively charged under alkaline conditions, and the silica particles cannot approach the wafer due to the repulsion of the charge, and the polishing rate cannot be fully expressed. However, in the present invention, the presence of the water-soluble polymer compound (component B) causes the water-soluble polymer compound (component B) to be adsorbed on the surfaces of both the silica particles and the wafer. (Component B) functions as a binder between the silica particles and the wafer. As a result, the interaction between the silica particles and the wafer is strengthened, and the polishing with the silica particles proceeds efficiently. Therefore, the water-soluble polymer compound (component B) contributes to securing a good polishing rate of the silicon wafer. It is thought that there is.

  As described above, in the present invention, the water-soluble polymer compound (component B) containing the structural unit represented by the general formula (1) suppresses aggregation of silica particles, so that a good surface of the silicon wafer is obtained. While achieving roughness (haze) and functioning as a binder of a silica particle and a silicon wafer, it contributes to ensuring a favorable polishing rate. However, the present invention is not limited to these estimations.

[Silica particles (component A)]
The polishing composition of the present invention contains silica particles as an abrasive. Specific examples of the silica particles include colloidal silica and fumed silica. Colloidal silica is more preferable from the viewpoint of improving the surface smoothness of the silicon wafer.

  The use form of the silica particles is preferably a slurry from the viewpoint of operability. When the abrasive contained in the polishing composition of the present invention is colloidal silica, colloidal silica is obtained from a hydrolyzate of alkoxysilane from the viewpoint of preventing contamination of the silicon wafer by alkali metal or alkaline earth metal. It is preferable that Silica particles obtained from the hydrolyzate of alkoxysilane can be produced by a conventionally known method.

  The average primary particle size of the silica particles contained in the polishing composition of the present invention is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 15 nm or more, and even more preferably 30 nm or more from the viewpoint of ensuring the polishing rate. . Further, the average primary particle diameter of the silica particles is preferably 50 nm or less, more preferably 45 nm or less, and still more preferably 40 nm or less, from the viewpoints of ensuring the polishing rate and reducing the surface roughness of the silicon wafer.

  In particular, when colloidal silica is used as the silica particles, the average primary particle diameter is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 15 nm or more, and even more preferably 30 nm or more, from the viewpoint of ensuring the polishing rate. preferable. Further, the average primary particle diameter of colloidal silica is preferably 50 nm or less, more preferably 45 nm or less, and still more preferably 40 nm or less, from the viewpoint of ensuring both the polishing rate and reducing the surface roughness of the silicon wafer.

The average primary particle diameter of the silica particles is calculated using a specific surface area S (m ² / g) calculated by a BET (nitrogen adsorption) method. A specific surface area can be measured by the method as described in an Example, for example.

  The degree of association of the silica particles is preferably 3.0 or less, more preferably 1.1 to 3.0, and more preferably 1.8 to 2.5, from the viewpoint of securing the polishing rate and reducing the surface roughness of the silicon wafer. Is more preferable, and 2.0 to 2.3 is even more preferable. The shape of the silica particles is preferably a so-called spherical type and a so-called mayu type. When the silica particles are colloidal silica, the degree of association is preferably 3.0 or less, more preferably 1.1 to 3.0, from the viewpoint of securing the polishing rate and reducing the surface roughness of the silicon wafer. 1.8-2.5 are still more preferable, and 2.0-2.3 are still more preferable.

The association degree of silica particles is a coefficient representing the shape of silica particles, and is calculated by the following formula. The average secondary particle diameter is a value measured by a dynamic light scattering method, and can be measured using, for example, the apparatus described in the examples.
Degree of association = average secondary particle size / average primary particle size

  The method for adjusting the degree of association of the silica particles is not particularly limited. For example, JP-A-6-254383, JP-A-11-214338, JP-A-11-60232, JP-A-2005-060217, A method described in JP-A-2005-060219 or the like can be employed.

  The content of the silica particles contained in the polishing liquid composition of the present invention is preferably 0.005% by mass or more, more preferably 0.05% by mass or more, and 0.10% by mass or more from the viewpoint of ensuring the polishing rate. Is more preferable, and 0.15% by mass or more is more preferable. Moreover, 1.0 mass% or less is preferable from a viewpoint of the economical improvement and the storage stability improvement of polishing liquid composition, 0.5 mass% or less is more preferable, 0.4 mass% or less is further more preferable, 0.3 The mass% or less is still more preferable, and 0.2 mass% or less is still more preferable.

[Water-soluble polymer compound (component B)]
The polishing composition of the present invention may be referred to as a structural unit represented by the following general formula (1) (hereinafter referred to as “structural unit I”) from the viewpoint of ensuring the polishing rate and reducing the surface roughness of the silicon wafer. And a water-soluble polymer compound (component B) having a weight average molecular weight of 20,000 to 1,000,000. In the present invention, “water-soluble” of a water-soluble polymer compound means having a solubility of 2 g / 100 ml or more in water.

ただし、上記一般式(１)において、Ｒ¹及びＲ²はそれぞれ独立して、水素又は炭素数が１〜２のモノヒドロキシアルキル基を示し、Ｒ³は炭素数が１〜４のアルキル基、炭素数が１〜４のモノヒドロキシアルキル基、又は炭素数が１〜４のジヒドロキシアルキル基を示し、Ｒ⁴は、水素又は炭素数が１〜４のアルキル基を示し、Ｒ⁵は、水素又はメチル基を示す。ただし、上記一般式(１)で表される構成単位は、２個以上の水酸基を含む。

However, in the general formula (1), R ¹ and R ² each independently represent hydrogen or a monohydroxyalkyl group having 1 to 2 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms, A monohydroxyalkyl group having 1 to 4 carbon atoms or a dihydroxyalkyl group having 1 to 4 carbon atoms, R ⁴ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ⁵ represents hydrogen or Indicates a methyl group. However, the structural unit represented by the general formula (1) contains two or more hydroxyl groups.

R ¹ and R ² are secured in the polishing rate, and from the viewpoint of reducing the surface roughness of the silicon wafer, each independently, hydrogen, a hydroxyethyl group, or a hydroxymethyl group, R ¹ and R ² At least one of them is preferably a hydroxymethyl group, more preferably both R ¹ and R ² are hydroxymethyl groups. R ³ is an alkyl group having 1 to 4 carbon atoms, a monohydroxyalkyl group having 1 to 4 carbon atoms, or a dihydroxyalkyl group having 1 to 4 carbon atoms from the viewpoint of reducing the surface roughness of the silicon wafer. However, a hydroxyethyl group or a hydroxymethyl group is more preferable, and a hydroxymethyl group is still more preferable.

  As a monomer which is a supply source of the structural unit I represented by the general formula (1), N- [tris (hydroxymethyl) methyl] acrylamide (THMMAA), N- [tris (hydroxymethyl) methyl] methacrylamide (THMMMAA), N- (2,3dihydroxy) propylacrylamide (PDAA), N- (2,3dihydroxy) propylmethacrylamide (PDMAA) and the like can be exemplified. These can be used alone or in combination of two or more. Among these monomers, N- [tris (hydroxymethyl) methyl] acrylamide (THMMAA) and N- [tris (hydroxymethyl) methyl are preferred from the viewpoint of reducing the surface roughness of the silicon wafer and ensuring the polishing rate. Methacrylamide (THMMMAA) is preferred, and N- [tris (hydroxymethyl) methyl] acrylamide (THMMAA) is more preferred.

  The proportion of the structural unit I in all the structural units of the water-soluble polymer compound (component B) is preferably 10% by mass or more, more preferably 20% by mass or more, from the viewpoint of reducing the surface roughness of the silicon wafer. More preferably 40% by weight or more, still more preferably 60% by weight or more, still more preferably 80% by weight or more, still more preferably 90% by weight or more, still more preferably 95% by weight or more, substantially 100% by weight. Is more preferable, and 100% by mass is even more preferable.

但し、下記一般式（２）において、Ｒ⁶及びＲ⁷は、それぞれ独立して、水素、炭素数が１〜４のアルキル基、又は炭素数が１〜２モノヒドロキシアルキル基を示す。ただし、上記一般式(２)で表される構成単位IIは、水酸基を２個以上含まない。 When the water-soluble polymer compound (component B) includes a structural unit other than the structural unit I, the structural unit other than the structural unit I is used in terms of ensuring a polishing rate and reducing the surface roughness of the silicon wafer. The structural unit II represented by the following general formula (2) is preferable.

However, in the following general formula (2), R ⁶ and R ⁷ each independently represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or a monohydroxyalkyl group having 1 to 2 carbon atoms. However, the structural unit II represented by the general formula (2) does not contain two or more hydroxyl groups.

  As a monomer which is a supply source of the structural unit II represented by the general formula (2), acrylamide (AA), N-methylacrylamide (MAA), N-ethylacrylamide, N-propylacrylamide, N-isopropylacrylamide (NIPAM), N-butylacrylamide, N-isobutylacrylamide, N-tertiarybutylacrylamide, N-heptylacrylamide, N-octylacrylamide, N-tertiaryoctylacrylamide, N-methylolacrylamide, N-hydroxyethylacrylamide (HEAA) ), N, N-dimethylacrylamide (DMAA), N, N-diethylacrylamide (DEAA), N, N-dipropylacrylamide, N, N-diisopropylacrylamide, N, N-dibutylactyl Ruamido, N, N-diisobutyl acrylamide, N, N-di-heptyl acrylamide, N, N-dioctyl acrylamide, N, N-dimethylol acrylamide, N, N-dihydroxyethyl acrylamide and the like. These can be used alone or in combination of two or more. Among these monomers, acrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, N, N-dimethylacrylamide, N, N- from the viewpoint of reducing the surface roughness of the silicon wafer and ensuring the polishing rate. Diethylacrylamide is preferred, and N-hydroxyethylacrylamide and N, N-diethylacrylamide are more preferred.

  When the water-soluble polymer compound (component B) is a copolymer containing the structural unit I and the structural unit II, the proportion of the structural unit I in all the structural units is the surface roughness of the silicon wafer. From the viewpoint of reduction, the content is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, still more preferably 60% by mass or more, still more preferably 80% by mass or more, and 90% by mass. The above is even more preferable.

  When the water-soluble polymer compound (component B) is a copolymer containing the structural unit I and the structural unit II, the proportion of the structural unit II in all the structural units is a reduction in the surface roughness of the silicon wafer. In view of the above, 90% by mass or less is preferable, 80% by mass or less is more preferable, 60% by mass or less is further preferable, 40% by mass or less is further more preferable, 20% by mass or less is further more preferable, and 10% by mass or less is more preferable. Even more preferred.

  The water-soluble polymer compound (component B) may contain a structural unit III as a structural unit other than the structural unit I and the structural unit II. Examples of the monomer component forming the structural unit III include acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, styrene, vinyl pyrrolidone, and oxazoline.

  When the water-soluble polymer compound (component B) is a copolymer containing the structural unit III, the arrangement of the structural units in the copolymer may be block or random.

  The weight average molecular weight of the water-soluble polymer compound (component B) is 20,000 or more, preferably 60,000 or more, more preferably 90,000 or more, and still more preferably 120,000 or more, from the viewpoint of improving the polishing rate. Further, the weight average molecular weight of the water-soluble polymer compound (component B) is 1,000,000 or less, preferably 900,000 or less, more preferably 800,000 or less, and 600,000 or less, from the viewpoint of reducing the surface roughness of the silicon wafer. Is more preferable, 400,000 or less is still more preferable, and 300,000 or less is still more preferable. In addition, the weight average molecular weight of a water-soluble polymer compound (component B) is measured by the method as described in a later Example.

  From the viewpoint of reducing the surface roughness of the silicon wafer, the content of the water-soluble polymer compound (component B) contained in the polishing composition of the present invention is preferably 0.0005% by mass or more, and 0.001% by mass. The above is more preferable, 0.002% by mass or more is further preferable, 0.003% by mass or more is further more preferable, 0.005% by mass or more is further more preferable, 0.007% by mass or more is further more preferable, and 01 mass% or more is still more preferable, 0.014 mass% or more is further more preferable, and 0.018 mass% or more is still more preferable. Further, the content of the water-soluble polymer compound (component B) is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, and further preferably 0.5% by mass or less from the viewpoint of ensuring the polishing rate. Preferably, 0.1% by mass or less is even more preferable, 0.05% by mass or less is further more preferable, 0.04% by mass or less is further more preferable, 0.03% by mass or less is further more preferable, and 0.025% by mass. % Or less is even more preferable.

  The mass ratio of the silica particles and the water-soluble polymer compound (component B) contained in the polishing composition of the present invention (the mass of silica particles / the mass of the water-soluble polymer compound (component B)) is the surface of the silicon wafer. From the viewpoint of reducing roughness, it is preferably 50 or less, more preferably 40 or less, still more preferably 30 or less, and still more preferably 24 or less. The mass ratio (mass of silica particles / mass of the water-soluble polymer compound) is preferably 1 or more, more preferably 4 or more, still more preferably 5 or more, and more preferably 7 or more from the viewpoint of ensuring the polishing rate. Is more preferable.

[Aqueous medium (component C)]
Examples of the aqueous medium (component C) contained in the polishing liquid composition of the present invention include water such as ion-exchanged water and ultrapure water, or a mixed medium of water and a solvent. Examples of the solvent include water and A miscible solvent (for example, an alcohol such as ethanol) is preferred. As the aqueous medium, ion-exchanged water or ultrapure water is more preferable, and ultrapure water is more preferable. When Component C of the present invention is a mixed medium of water and a solvent, the ratio of water to the entire mixed medium as Component C is not particularly limited, but is 95% by mass or more from the viewpoint of economy. Is preferable, 98 mass% or more is more preferable, and substantially 100 mass% is still more preferable.

  The content of the aqueous medium in the polishing liquid composition of the present invention is not particularly limited, and may be the remainder of Component A, Component B, and optional components described below.

  The pH at 25 ° C. of the polishing composition of the present invention is preferably 8.0 or more, more preferably 9.0 or more, still more preferably 9.5 or more, and 12.0 from the viewpoint of ensuring the polishing rate. The following is preferable, 11.5 or less is more preferable, and 11.0 or less is still more preferable. Adjustment of pH can be performed by adding a nitrogen-containing basic compound (component D) and / or a pH adjuster as described later as needed. Here, the pH at 25 ° C. can be measured using a pH meter (Toa Denpa Kogyo Co., Ltd., HM-30G), and is a value one minute after immersion of the electrode in the polishing composition.

[Optional ingredients (auxiliaries)]
In the polishing liquid composition of the present invention, a water-soluble polymer compound other than the nitrogen-containing basic compound (component D) and the water-soluble polymer compound (component B), as long as the effects of the present invention are not hindered, At least one optional component selected from pH adjusters, preservatives, alcohols, chelating agents, anionic surfactants, and nonionic surfactants may be included.

[Nitrogen-containing basic compound (component D)]
The polishing liquid composition of the present invention contains a water-soluble basic compound from the viewpoint of improving the storage stability of the polishing liquid composition, ensuring the polishing rate, and reducing the surface roughness of the silicon wafer. The water-soluble basic compound is at least one nitrogen-containing basic compound selected from amine compounds and ammonium compounds. Here, “water-soluble” means having a solubility of 2 g / 100 ml or more in water at 20 ° C., and “water-soluble basic compound” indicates basicity when dissolved in water. Refers to a compound.

  Examples of the at least one nitrogen-containing basic compound selected from amine compounds and ammonium compounds include ammonia, ammonium hydroxide, ammonium carbonate, ammonium hydrogen carbonate, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, Monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-methyl-N, N-diethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N, N-dibutylethanol Amine, N- (β-aminoethyl) ethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, ethylenediamine, hexamethylenediamine , Piperazine hexahydrate, anhydrous piperazine, 1- (2-aminoethyl) piperazine, N- methylpiperazine, diethylenetriamine, and tetramethylammonium and the like hydroxide. These nitrogen-containing basic compounds may be used as a mixture of two or more. The nitrogen-containing basic compound that can be contained in the polishing liquid composition of the present invention is more preferably ammonia from the viewpoint of reducing the surface roughness of the silicon wafer and improving the storage stability of the polishing liquid composition.

  The content of the nitrogen-containing basic compound contained in the polishing liquid composition of the present invention is preferably 0.001% by mass or more from the viewpoint of improving the storage stability of the polishing liquid composition and ensuring the polishing rate. 0.004 mass% or more is more preferable, 0.006 mass% or more is further preferable, 0.008 mass% or more is still more preferable, and 0.010 mass% or more is still more preferable. Further, from the viewpoint of reducing the surface roughness of the silicon wafer, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less. Preferably, 0.025 mass% or less is still more preferable, 0.018 mass% or less is further more preferable, and 0.014 mass% or less is still more preferable.

[Water-soluble polymer compound (component E)]
The polishing composition of the present invention may further contain a water-soluble polymer compound (component E) other than the water-soluble polymer compound (component B) from the viewpoint of reducing surface defects of the silicon wafer. This water-soluble polymer compound (component E) is a polymer compound having a hydrophilic group, and the weight average molecular weight of the water-soluble polymer compound (component E) is to ensure the polishing rate and reduce the surface defects of the silicon wafer. From the viewpoint, 10,000 or more is preferable, 100,000 or more is more preferable, 1,000,000 or less is preferable, and 500,000 or less is more preferable. Examples of the monomer that is a supply source constituting the component E include, for example, an amide group other than the amide group derived from the structural unit I of the component B, a hydroxyl group, a carboxyl group, a carboxylic acid ester group, a sulfonic acid group, and the like. And a monomer having a water-soluble group. Examples of such a water-soluble polymer compound (component E) include polyamide, poly (N-acylalkylenimine), cellulose derivatives, polyvinyl alcohol, polyethylene oxide and the like. Examples of the polyamide include polyvinyl pyrrolidone, polyacrylamide, and polyoxazoline. As poly (N-acylalkylenimine), poly (N-acetylethyleneimine), poly (N-propionylethyleneimine), poly (N-caproylethyleneimine), poly (N-benzoylethyleneimine), poly ( N-nonadezoylethyleneimine), poly (N-acetylpropyleneimine), poly (N-butionylethyleneimine) and the like. Examples of the cellulose derivative include carboxymethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl ethyl cellulose, and carboxymethyl ethyl cellulose. These water-soluble polymer compounds may be used in a mixture of two or more at any ratio.

[pH adjuster]
An acidic compound is mentioned as a pH adjuster. Examples of the acidic compound include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, and organic acids such as acetic acid, oxalic acid, succinic acid, glycolic acid, malic acid, citric acid and benzoic acid.

[Preservative]
Preservatives include benzalkonium chloride, benzethonium chloride, 1,2-benzisothiazolin-3-one, (5-chloro-) 2-methyl-4-isothiazolin-3-one, hydrogen peroxide, or hypochlorite Examples include acid salts.

[Alcohols]
Examples of alcohols include methanol, ethanol, propanol, butanol, isopropyl alcohol, 2-methyl-2-propanool, ethylene glycol, propylene glycol, polyethylene glycol, and glycerin. The content of alcohol in the polishing composition of the present invention is preferably 0.1% by mass to 5% by mass. However, the content is an amount added in addition to the alcohol contained as a part of the aqueous medium (component C) when the aqueous medium (component C) contains an alcohol.

[Chelating agent]
Chelating agents include: ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, triethylenetetraminehexaacetic acid, triethylenetetramine Examples include sodium hexaacetate. As for content of the chelating agent in the polishing liquid composition of this invention, 0.01-1 mass% is preferable.

[Anionic surfactant]
Examples of the anionic surfactant include fatty acid soaps, carboxylates such as alkyl ether carboxylates, sulfonates such as alkylbenzene sulfonates and alkylnaphthalene sulfonates, higher alcohol sulfates, alkyl ether sulfates. And sulfate ester salts such as alkyl phosphate esters and the like.

[Nonionic surfactant]
Nonionic surfactants include polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbit fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl phenyl ether, Examples include polyethylene glycol types such as oxyalkylene (cured) castor oil, polyhydric alcohol types such as sucrose fatty acid ester, polyglycerin alkyl ether, polyglycerin fatty acid ester, alkylglycoside, and fatty acid alkanolamide.

  In addition, although content of each component demonstrated above is content at the time of use, the polishing liquid composition of this invention is preserve | saved and supplied in the state concentrated in the range by which the storage stability is not impaired. May be. In this case, it is preferable in that the manufacturing and transportation costs can be further reduced. The concentrate may be used after appropriately diluted with the above-mentioned aqueous medium as necessary. The concentration factor is not particularly limited as long as the concentration at the time of polishing after dilution can be secured, but it is preferably 2 times or more, more preferably 10 times or more, from the viewpoint of further reducing the production and transportation costs. The ratio is more preferably double or more, still more preferably 30 or more, more preferably 100 or less, more preferably 80 or less, still more preferably 60 or less, and even more preferably 50 or less.

  When the polishing liquid composition of the present invention is the above concentrated liquid, the content of silica particles (component A) in the concentrated liquid is preferably 2% by mass or more, from the viewpoint of reducing production and transportation costs, and is 4% by mass or more. Is more preferable, and 6 mass% or more is still more preferable. In addition, the content of silica particles in the concentrate is preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 20% by mass or less, and further preferably 15% by mass or less from the viewpoint of improving storage stability. Even more preferred is 9% by weight or less.

  When the polishing liquid composition of the present invention is the concentrated liquid, the content of the water-soluble polymer compound (component B) in the concentrated liquid is preferably 0.005% by mass or more from the viewpoint of reducing production and transportation costs. 0.01 mass% or more is more preferable, 0.02 mass% or more is further preferable, 0.05 mass% or more is still more preferable, and 0.1 mass% or more is still more preferable. Further, the content of the water-soluble polymer compound (component B) in the concentrate is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2% by mass or less from the viewpoint of improving storage stability. Preferably, 1 mass% or less is still more preferable.

  When the polishing liquid composition of the present invention is the concentrated liquid, the content of the nitrogen-containing basic compound (component D) in the concentrated liquid is preferably 0.02% by mass or more from the viewpoint of reducing production and transportation costs. 0.05 mass% or more is more preferable, and 0.1 mass% or more is still more preferable. Further, the content of the nitrogen-containing basic compound (component D) in the concentrate is preferably 5% by mass or less, more preferably 2% by mass or less, and further preferably 1% by mass or less from the viewpoint of improving storage stability. .

  When the polishing composition of the present invention is the concentrated liquid, the pH of the concentrated liquid at 25 ° C. is preferably 8.0 or higher, more preferably 9.0 or higher, and even more preferably 9.5 or higher. 12.0 or less is preferable, 11.5 or less is more preferable, and 11.0 or less is still more preferable.

  Next, an example of the manufacturing method of the polishing composition of the present invention will be described.

  An example of the manufacturing method of the polishing composition of the present invention is not limited at all. For example, silica particles (component A), a water-soluble polymer compound (component B), an aqueous medium (component C), and the like are necessary. Accordingly, it can be prepared by mixing arbitrary components.

  Dispersion of silica particles in an aqueous medium can be performed using a stirrer such as a homomixer, a homogenizer, an ultrasonic disperser, a wet ball mill, or a bead mill, for example. When coarse particles generated by aggregation of silica particles or the like are contained in an aqueous medium, it is preferable to remove the coarse particles by centrifugation or filtration using a filter. The dispersion of the silica particles in the aqueous medium is preferably performed in the presence of a water-soluble polymer compound (component B). Specifically, after preparing a silicon wafer polishing additive composition containing a water-soluble polymer compound (component B) and an aqueous medium (component C), the silicon wafer polishing additive composition and silica particles, And then, if necessary, the mixture of the silicon wafer polishing additive composition and silica particles is preferably diluted with an aqueous medium (component C).

  The polishing composition of the present invention is used in, for example, a polishing method for polishing a silicon wafer and a polishing method for a silicon wafer including a polishing step for polishing a silicon wafer in the process of manufacturing a semiconductor substrate.

  In the polishing process for polishing the silicon wafer, a lapping (rough polishing) process for planarizing a silicon wafer obtained by slicing a silicon single crystal ingot into a thin disk shape, and etching the lapped silicon wafer Thereafter, there is a finish polishing step for mirror-finishing the silicon wafer surface. The polishing composition of the present invention is more preferably used in the above-described finish polishing step.

  The semiconductor substrate manufacturing method and the silicon wafer polishing method may include a dilution step of diluting the polishing composition (concentrate) of the present invention before the polishing step of polishing the silicon wafer. An aqueous medium (component C) may be used as the diluent.

  The concentrate diluted in the dilution step contains, for example, 2 to 40% by mass of component A and 0.005 to 5% by mass of component B from the viewpoints of manufacturing and transportation cost reduction and improvement of storage stability. And preferred.

  The present invention further discloses the following <1> to <16>.

ただし、上記一般式(１)において、Ｒ¹及びＲ²はそれぞれ独立して、水素又は炭素数が１〜２のモノヒドロキシアルキル基を示し、Ｒ³は炭素数が１〜４のアルキル基、炭素数が１〜４のモノヒドロキシアルキル基、又は炭素数が１〜４のジヒドロキシアルキル基を示し、Ｒ⁴は、水素又は炭素数が１〜４のアルキル基を示し、Ｒ⁵は、水素又はメチル基を示す。ただし、上記一般式(１)で表される構成単位は、２個以上の水酸基を含む。
＜２＞ 好ましくは前記Ｒ¹及びＲ²のうちの少なくとも一方がヒドロキシメチル基であり、より好ましくはＲ¹及びＲ²の双方がヒドロキシメチル基である、＜１＞に記載のシリコンウェーハ用研磨液組成物。
＜３＞ 前記Ｒ³が、好ましくはヒドロキシエチル基又はヒドロキシメチル基、より好ましくはヒドロキシメチル基である、＜１＞又は＜２＞に記載のシリコンウェーハ用研磨液組成物。
＜４＞ 前記一般式（１）で表される構成単位Ｉの供給源である単量体が、好ましくはＮ−［トリス（ヒドロキシメチル）メチル］アクリルアミド（ＴＨＭＭＡＡ）、Ｎ−［トリス（ヒドロキシメチル）メチル］メタクリルアミド（ＴＨＭＭＭＡＡ）、Ｎ−（２，３ジヒドロキシ）プロピルアクリルアミド（ＰＤＡＡ）、又はＮ−（２，３ジヒドロキシ）プロピルメタクリルアミド（ＰＤＭＡＡ）、より好ましくはＮ−［トリス（ヒドロキシメチル）メチル］アクリルアミド（ＴＨＭＭＡＡ）、又はＮ−［トリス（ヒドロキシメチル）メチル］メタクリルアミド（ＴＨＭＭＭＡＡ）、更に好ましくはＮ−［トリス（ヒドロキシメチル）メチル］アクリルアミド（ＴＨＭＭＡＡ）である、＜１＞に記載のシリコンウェーハ用研磨液組成物。
＜５＞ 前記水溶性高分子化合物の全構成単位中における前記構成単位Ｉの割合が、好ましくは１０質量％以上、より好ましくは２０質量％以上、更に好ましくは４０質量％以上、更により好ましくは６０質量％以上、更により好ましくは８０質量％以上、更により好ましくは９０質量％以上、更により好ましくは９５質量％以上、更により好ましくは実質的に１００質量％、更により好ましくは１００質量％である、＜１＞〜＜４＞のいずれかに記載のシリコンウェーハ用研磨液組成物。
＜６＞ 前記水溶性高分子化合物が前記構成単位Ｉ以外の構成単位IIを含み、前記構成単位IIの供給源である単量体は、好ましくはアクリルアミド、Ｎ−イソプロピルアクリルアミド、Ｎ−ヒドロキシエチルアクリルアミド、Ｎ，Ｎ−ジメチルアクリルアミド、及びＮ，Ｎ−ジエチルアクリルアミドからなる群から選ばれる少なくとも１種であり、より好ましくはＮ−ヒドロキシエチルアクリルアミド及びＮ，Ｎ−ジエチルアクリルアミドからなる群から選ばれる少なくとも１種である、＜１＞〜＜４＞のいずれかに記載のシリコンウェーハ用研磨液組成物。
＜７＞ 前記水溶性高分子化合物の全構成単位中における前記構成単位Ｉの割合が、好ましくは１０質量％以上、より好ましくは２０質量％以上、更に好ましくは４０質量％以上、更により好ましくは６０質量％以上、更により好ましくは８０質量％以上、更により好ましくは９０質量％以上である、＜６＞に記載のシリコンウェーハ用研磨液組成物。
＜８＞ 前記水溶性高分子化合物の全構成単位中における前記構成単位IIの割合が、好ましくは９０質量％以下、より好ましくは８０質量％以下、更に好ましくは６０質量％以下、更により好ましくは４０質量％以下、更により好ましくは２０質量％以下、更により好ましくは１０質量％以下である、＜６＞又は＜７＞に記載のシリコンウェーハ用研磨液組成物。
＜９＞前記水溶性高分子化合物の重量平均分子量が、好ましくは６万以上、より好ましくは９万以上、更に好ましくは１２万以上であり、好ましくは１００万以下、より好ましくは９０万以下、更に好ましくは８０万以下、更により好ましくは６０万以下、更により好ましくは４０万以下、更により好ましくは３０万以下である、＜１＞〜＜８＞のいずれかに記載のシリコンウェーハ用研磨液組成物。
＜１０＞ 前記シリカ粒子と前記水溶性高分子化合物との質量比（シリカ粒子の質量/水溶性高分子化合物の質量）が、好ましくは５０以下、より好ましくは４０以下、更に好ましくは３０以下、更により好ましくは２４以下であり、好ましくは１以上、より好ましくは４以上、更に好ましくは５以上、更により好ましいくは７以上である、＜１＞〜＜９＞のいずれかに記載のシリコンウェーハ用研磨液組成物。
＜１１＞ 前記水溶性高分子化合物の含有量が、好ましくは０．０００５質量％以上、より好ましくは０．００１質量％以上、更に好ましくは０．００２質量％以上、更により好ましくは０．００３質量％以上、更により好ましくは０．００５質量％以上、更により好ましくは０．００７質量％以上、更により好ましくは０．０１質量％以上、更により好ましくは０．０１４質量％以上、更により好ましくは０．０１８質量％以上であり、好ましくは１．０質量％以下、より好ましくは０．８質量％以下、更に好ましくは０．５質量％以下、更に好ましくは０．１質量％以下、更により好ましくは０．０５質量％以下、更により好ましくは０．０４質量％以下、更により好ましくは０．０３質量％以下、更により好ましくは０．０２５質量％以下である、＜１＞〜＜１０＞のいずれかに記載のシリコンウェーハ用研磨液組成物。
＜１２＞ 前記シリカ粒子の含有量が、好ましくは０．００５質量％以上、より好ましくは０．０５質量％以上、更に好ましくは０．１０質量％以上、更により好ましくは０．１５質量％以上であり、好ましくは１．０質量％以下、より好ましくは０．５質量％以下、更に好ましくは０．４質量％以下、更により好ましくは０．３質量％以下、更により好ましくは０．２質量％以下である、＜１＞〜＜１１＞のいずれかに記載のシリコンウェーハ用研磨液組成物。
＜１３＞ 前記シリカ粒子の平均一次粒子径が、好ましくは５ｎｍ以上、より好ましくは１０ｎｍ以上、更に好ましくは１５ｎｍ以上、更により好ましくは３０ｎｍ以上であり、好ましくは５０ｎｍ以下、より好ましくは４５ｎｍ以下、更に好ましくは４０ｎｍ以下である、前記＜１＞〜＜１２＞のいずれかに記載のシリコンウェーハ用研磨液組成物。
＜１４＞ 前記＜１＞〜＜１３＞のいずれかに記載のシリコンウェーハ用研磨液組成物を用いてシリコンウェーハを研磨する研磨工程を含む研磨方法。
＜１５＞ 前記＜１＞〜＜１３＞のいずれかに記載のシリコンウェーハ用研磨液組成物を用いてシリコンウェーハを研磨する研磨工程を含む、半導体基板の製造方法。
＜１６＞ 前記＜１＞〜＜１３＞のいずれかに記載のシリコンウェーハ用研磨液組成物の調製に使用される、シリコンウェーハ研磨用添加剤組成物であって、下記一般式（１）で表される構成単位を含み、重量平均分子量が２万以上１００万以下の水溶性高分子化合物と、水系媒体とを含むシリコンウェーハ研磨用添加剤組成物。

ただし、上記一般式(１)において、Ｒ¹及びＲ²はそれぞれ独立して、水素又は炭素数が１〜２のモノヒドロキシアルキル基を示し、Ｒ³は炭素数が１〜４のアルキル基、炭素数が１〜４のモノヒドロキシアルキル基、又は炭素数が１〜４のジヒドロキシアルキル基を示し、Ｒ⁴は、水素又は炭素数が１〜４のアルキル基を示し、Ｒ⁵は、水素又はメチル基を示す。ただし、上記一般式(１)で表される構成単位は、２個以上の水酸基を含む。 <1> A polishing composition for a silicon wafer comprising silica particles and a water-soluble polymer compound having a structural unit represented by the following general formula (1) and having a weight average molecular weight of 20,000 to 1,000,000.

However, in the general formula (1), R ¹ and R ² each independently represent hydrogen or a monohydroxyalkyl group having 1 to 2 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms, A monohydroxyalkyl group having 1 to 4 carbon atoms or a dihydroxyalkyl group having 1 to 4 carbon atoms, R ⁴ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ⁵ represents hydrogen or Indicates a methyl group. However, the structural unit represented by the general formula (1) contains two or more hydroxyl groups.
<2> preferably at least one hydroxymethyl group of said R ¹ and R ^2, more preferably both hydroxymethyl group of R ¹ and R ^2, polished silicon wafer according to <1> Liquid composition.
<3> The polishing composition for a silicon wafer according to <1> or <2>, wherein R ³ is preferably a hydroxyethyl group or a hydroxymethyl group, more preferably a hydroxymethyl group.
<4> The monomer which is a supply source of the structural unit I represented by the general formula (1) is preferably N- [tris (hydroxymethyl) methyl] acrylamide (THMMAA), N- [tris (hydroxymethyl). ) Methyl] methacrylamide (THMMMAA), N- (2,3dihydroxy) propylacrylamide (PDAA), or N- (2,3dihydroxy) propylmethacrylamide (PDMAA), more preferably N- [tris (hydroxymethyl) Methyl] acrylamide (THMMAA), or N- [tris (hydroxymethyl) methyl] methacrylamide (THMMMAA), more preferably N- [tris (hydroxymethyl) methyl] acrylamide (THMMAA), according to <1> Polishing liquid composition for silicon wafers.
<5> The proportion of the structural unit I in all the structural units of the water-soluble polymer compound is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, and still more preferably. 60% by weight or more, still more preferably 80% by weight or more, still more preferably 90% by weight or more, still more preferably 95% by weight or more, still more preferably substantially 100% by weight, and even more preferably 100% by weight. The polishing composition for silicon wafers according to any one of <1> to <4>.
<6> The monomer that includes the structural unit II other than the structural unit I and is a supply source of the structural unit II is preferably acrylamide, N-isopropylacrylamide, or N-hydroxyethylacrylamide. , N, N-dimethylacrylamide and at least one selected from the group consisting of N, N-diethylacrylamide, more preferably at least one selected from the group consisting of N-hydroxyethylacrylamide and N, N-diethylacrylamide. The polishing composition for a silicon wafer according to any one of <1> to <4>, which is a seed.
<7> The proportion of the structural unit I in all the structural units of the water-soluble polymer compound is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, and still more preferably. The polishing composition for silicon wafers according to <6>, which is 60% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more.
<8> The proportion of the structural unit II in all the structural units of the water-soluble polymer compound is preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 60% by mass or less, and still more preferably. The polishing composition for a silicon wafer according to <6> or <7>, which is 40% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less.
<9> The weight average molecular weight of the water-soluble polymer compound is preferably 60,000 or more, more preferably 90,000 or more, still more preferably 120,000 or more, preferably 1,000,000 or less, more preferably 900,000 or less, More preferably 800,000 or less, still more preferably 600,000 or less, still more preferably 400,000 or less, and even more preferably 300,000 or less, polishing for silicon wafers according to any one of <1> to <8> Liquid composition.
<10> The mass ratio of the silica particles to the water-soluble polymer compound (silica particle mass / water-soluble polymer compound mass) is preferably 50 or less, more preferably 40 or less, and even more preferably 30 or less. The silicon according to any one of <1> to <9>, which is more preferably 24 or less, preferably 1 or more, more preferably 4 or more, still more preferably 5 or more, and even more preferably 7 or more. Polishing liquid composition for wafers.
<11> The content of the water-soluble polymer compound is preferably 0.0005% by mass or more, more preferably 0.001% by mass or more, still more preferably 0.002% by mass or more, and still more preferably 0.003. % By mass, still more preferably 0.005% by mass or more, still more preferably 0.007% by mass or more, still more preferably 0.01% by mass or more, still more preferably 0.014% by mass or more, and even more. Preferably it is 0.018 mass% or more, preferably 1.0 mass% or less, more preferably 0.8 mass% or less, still more preferably 0.5 mass% or less, still more preferably 0.1 mass% or less, Even more preferably 0.05% by weight or less, still more preferably 0.04% by weight or less, even more preferably 0.03% by weight or less, and even more preferably 0.025% by weight or less. The polishing composition for a silicon wafer according to any one of <1> to <10>, which is below.
<12> The content of the silica particles is preferably 0.005% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.10% by mass or more, and even more preferably 0.15% by mass or more. Preferably 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.4% by mass or less, still more preferably 0.3% by mass or less, and even more preferably 0.2% by mass. The polishing composition for silicon wafers according to any one of <1> to <11>, which is not more than mass%.
<13> The average primary particle diameter of the silica particles is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 15 nm or more, still more preferably 30 nm or more, preferably 50 nm or less, more preferably 45 nm or less, More preferably, it is 40 nm or less, The polishing liquid composition for silicon wafers in any one of said <1>-<12>.
<14> A polishing method including a polishing step of polishing a silicon wafer using the silicon wafer polishing composition according to any one of <1> to <13>.
<15> A method for producing a semiconductor substrate, comprising a polishing step of polishing a silicon wafer using the polishing composition for a silicon wafer according to any one of <1> to <13>.
<16> An additive composition for polishing a silicon wafer, which is used for preparing the polishing composition for a silicon wafer according to any one of <1> to <13>, wherein the following general formula (1): An additive composition for polishing a silicon wafer comprising a water-soluble polymer compound having a structural unit represented and having a weight average molecular weight of 20,000 to 1,000,000 and an aqueous medium.

However, in the general formula (1), R ¹ and R ² each independently represent hydrogen or a monohydroxyalkyl group having 1 to 2 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms, A monohydroxyalkyl group having 1 to 4 carbon atoms or a dihydroxyalkyl group having 1 to 4 carbon atoms, R ⁴ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ⁵ represents hydrogen or Indicates a methyl group. However, the structural unit represented by the general formula (1) contains two or more hydroxyl groups.

<Synthesis of water-soluble polymer compounds>
The water-soluble polymer compounds used in the following Examples 1 to 25 and Comparative Example 1 were synthesized as follows.

(Water-soluble polymer compound No. 1)
[THMMAA polymer, weight average molecular weight 100,000]
Tris (hydroxymethyl) methylacrylamide (Aldrich) 24.5g, 2,2'-Azobis (2-methyl propionamidine) dihydrochloride "V-50" (Wako Pure Chemical Industries, Ltd.) 0.035g, and pure water 180.5g 300ml They were placed in a glass beaker and stirred to dissolve. Thereafter, the obtained solution was filtered through a 0.45 μm cellulose acetate membrane filter (DISMIC (registered trademark) -25CS manufactured by Advantech Toyo Co., Ltd.). The obtained filtrate was put into a 300 ml separable flask equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a stirrer, and then nitrogen gas was added to the separable flask at room temperature at 100 ml / min for 30 minutes. Under a nitrogen atmosphere, 22.8 g of isopropyl alcohol (special grade manufactured by Wako Pure Chemical Industries, Ltd.) was added to the filtrate. Thereafter, the filtrate to which isopropyl alcohol was added was heated to 60 ° C., and then stirred at 60 ° C. for 6 hours. After the obtained reaction product (solution state) was cooled to room temperature, the reaction product was added to 3 L of acetone (grade 1 manufactured by Wako Pure Chemical Industries, Ltd.) to precipitate a solid, and the solid was collected. This solid was dried under reduced pressure at 70 ° C. for 12 hours to obtain 17.8 g (yield 78%) of a white solid (water-soluble polymer compound No. 1).

(Water-soluble polymer compound No. 2)
[THMMAA polymer, weight average molecular weight 650,000]
Tris (hydroxymethyl) methylacrylamide (Aldrich) 2.0g, 2,2'-Azobis (2-methylpropionamidine) dihydrochloride "V-50" (Wako Pure Chemical Industries, Ltd.) 0.014g, and pure water 72.4g 100ml These were placed in a glass beaker and dissolved by stirring. Thereafter, the obtained solution was filtered through a 5 μm cellulose acetate membrane filter (Sartorius Minisart). The obtained filtrate was put into a 110 ml screw tube (No. 8 manufactured by Maruem), and then nitrogen gas was blown into the screw tube at room temperature for 30 minutes at 100 ml / min. The filtrate was allowed to stand at 80 ° C. for 12 hours to obtain an aqueous solution of a colorless and transparent polymer (water-soluble polymer compound No. 2).

(Water-soluble polymer compound No. 3)
[THMMAA polymer, weight average molecular weight 64,000]
After putting 51.9 g of pure water in a 300 ml separable flask equipped with a reflux condenser, thermometer, nitrogen inlet tube, and stirrer, the separable flask is evacuated to 10 KPa and then brought to atmospheric pressure with nitrogen gas. The return operation was performed three times and a nitrogen atmosphere was established. Thereafter, the temperature in the separable flask was heated to 75 ° C. Separately, Tris (hydroxymethyl) methylacrylamide (AlfaAcer) 15.0g, 2,2'-Azobis (2-methyl propionamidine) dihydrochloride "V-50" (Wako Pure Chemical Industries, Ltd.) 0.116g, and pure water 83.0g After mixing and dissolving, the obtained solution was filtered through a 0.45 μm cellulose acetate membrane filter (DISMIC (registered trademark) -25CS manufactured by Advantech Toyo Co., Ltd.). The obtained filtrate was dropped into a 300 ml separable flask heated to 75 ° C. for 3 hours. Thereafter, the filtrate in the separable flask was stirred at 75 ° C. for 4 hours to obtain an aqueous solution of a colorless and transparent polymer (water-soluble polymer compound No. 3).

(Water-soluble polymer compound No. 4)
[THMMAA polymer, weight average molecular weight 92,000]
Tris (hydroxymethyl) methylacrylamide (Aldrich) 12g, 2,2'-Azobis (2-methylpropionamidine) dihydrochloride "V-50" (Wako Pure Chemical Industries, Ltd.) 0.017g, and pure water 88.4g in 300ml glass They were placed in a beaker and dissolved by stirring. Thereafter, the obtained solution was filtered through a 0.45 μm cellulose acetate membrane filter (DISMIC (registered trademark) -25CS manufactured by Advantech Toyo Co., Ltd.). The obtained filtrate was put into a 200 ml separable flask equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a stirrer, and then nitrogen gas was introduced into the separable flask at room temperature at 100 ml / min for 30 minutes. Under a nitrogen atmosphere, 11.6 g of isopropyl alcohol (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) was added to the filtrate. Thereafter, the filtrate to which isopropyl alcohol was added was heated to 60 ° C., and then stirred at 60 ° C. for 6 hours. After the obtained reaction product (solution state) was cooled to room temperature, the reaction product was added to 3 L of acetone (grade 1 manufactured by Wako Pure Chemical Industries, Ltd.) to precipitate a solid, and the solid was collected. This solid was dried under reduced pressure at 70 ° C. for 12 hours to obtain 9.8 g (yield 88%) of a white solid (water-soluble polymer compound No. 4).

(Water-soluble polymer compound No. 5)
[THMMAA polymer, weight average molecular weight 160,000]
After putting 43.3 g of pure water in a 300 ml separable flask equipped with a reflux condenser, thermometer, nitrogen inlet tube, and stirring device, the separable flask was depressurized to 10 KPa and then brought to atmospheric pressure with nitrogen gas. The return operation was performed three times and a nitrogen atmosphere was established. Thereafter, the temperature in the separable flask was heated to 75 ° C. Separately, Tris (hydroxymethyl) methylacrylamide (AlfaAcer) 15.0g, 2,2'-Azobis (2-methyl propionamidine) dihydrochloride "V-50" (Wako Pure Chemical Industries, Ltd.) 0.093g, and pure water 91.3g After mixing and dissolving, the obtained solution was filtered through a 0.45 μm cellulose acetate membrane filter (DISMIC (registered trademark) -25CS manufactured by Advantech Toyo Co., Ltd.). The obtained filtrate was dropped into a 300 ml separable flask heated to 75 ° C. for 3 hours. Thereafter, the filtrate in the separable flask was stirred at 75 ° C. for 4 hours to obtain an aqueous solution of a colorless and transparent polymer (water-soluble polymer compound No. 5).

(Water-soluble polymer compound No. 6)
[THMMAA polymer, weight average molecular weight 370,000]
Tris (hydroxymethyl) methylacrylamide (AlfaAcer) 2.0g, 2,2'-Azobis (2-methylpropionamidine) dihydrochloride "V-50" (Wako Pure Chemical Industries, Ltd.) 0.016g, and pure water 78.0g 100ml They were placed in a glass beaker and stirred to dissolve. Thereafter, the obtained solution was filtered through a 5 μm cellulose acetate membrane filter (Sartorius Minisart). The obtained filtrate was put into a 110 ml screw tube (No. 8 manufactured by Maruem), and then nitrogen gas was blown into the screw tube at room temperature for 30 minutes at 100 ml / min. The filtrate was allowed to stand at 80 ° C. for 12 hours to obtain an aqueous solution of a colorless and transparent polymer (water-soluble polymer compound No. 6).

(Water-soluble polymer compound No. 7)
[THMMAA polymer, weight average molecular weight 520,000]
Tris (hydroxymethyl) methylacrylamide (Aldrich) 12g, 2,2'-Azobis (2-methylpropionamidine) dihydrochloride "V-50" (Wako Pure Chemical Industries, Ltd.) 0.017g, and pure water 434.38g in 500ml glass The solution was stirred and dissolved in a beaker. Thereafter, the obtained solution was added to a 500 ml separable flask equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a stirring device, and then nitrogen gas was added to the separable flask at room temperature at 100 ml / min. After blowing for 30 minutes and putting the inside of the separable flask under a nitrogen atmosphere, the solution was heated to 80 ° C. and then stirred at 80 ° C. for 6 hours. After the obtained reaction product (solution state) was cooled to room temperature, the reaction product was added to 3 L of acetone (grade 1 manufactured by Wako Pure Chemical Industries, Ltd.) to precipitate a solid, and the solid was collected. This solid was dried under reduced pressure at 70 ° C. for 12 hours to obtain 9.8 g (yield 88%) of a white solid (water-soluble polymer compound No. 7).

(Water-soluble polymer compound No. 8)
[THMMAA polymer, weight average molecular weight 820,000]
After putting 26.8 g of pure water into a 300 ml separable flask equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a stirrer, the inside of the separable flask was depressurized to 10 KPa and then brought to normal pressure with nitrogen gas. The return operation was performed three times and a nitrogen atmosphere was established. Thereafter, the temperature in the separable flask was heated to 68 ° C. Separately, 15.0 g of Tris (hydroxymethyl) methylacrylamide (AlfaAcer), 0.046 g of 2,2'-Azobis (2-methyl propionamidine) dihydrochloride “V-50” (manufactured by Wako Pure Chemical Industries, Ltd.), and 108.17 g of pure water After mixing and dissolving, the obtained solution was filtered through a 0.45 μm cellulose acetate membrane filter (DISMIC (registered trademark) -25CS manufactured by Advantech Toyo Co., Ltd.). The obtained filtrate was added dropwise to a 300 ml separable flask heated to an internal temperature of 68 ° C. over 3 hours. Thereafter, the filtrate in the separable flask was stirred at 75 ° C. for 4 hours to obtain an aqueous solution of a colorless and transparent polymer (water-soluble polymer compound No. 8).

(Water-soluble polymer compound No. 9)
[THMMAA polymer, 1.28 million weight average molecular weight]
110ml of Tris (hydroxymethyl) methylacrylamide (Aldrich) 3.0g, 2,2'-Azobis (2-methylpropionamidine) dihydrochloride "V-50" (Wako Pure Chemical Industries, Ltd.) 0.004g, and pure water 52.8g Were put into a screw tube (No. 8 manufactured by Marum Co., Ltd.), and these were stirred and dissolved to obtain a solution. Next, nitrogen gas was blown into the screw tube at room temperature for 30 minutes at 100 ml / min., And the screw tube was sealed, and then the solution was allowed to stand at 80 ° C. for 12 hours to obtain a colorless transparent polymer (water-soluble polymer compound No. 1). 9) was obtained.

(Water-soluble polymer compound No. 10)
[THMMAA / DMAA copolymer, THMMAA / DMAA mass ratio 95: 5, weight average molecular weight 410,000]
Tris (hydroxymethyl) methylacrylamide (AlfaAcer) 1.8g, N, N-Dimethylacrylamide 0.2g (Wako Pure Chemical Industries, Ltd.), 2,2'-Azobis (2-methyl propionamidine) dihydrochloride "V-50" (Japanese) After adding 0.017 g (manufactured by Kosei Pharmaceutical Co., Ltd.) and 78.0 g of pure water to a 100 ml glass beaker and stirring and dissolving them, the obtained solution was added to a 5 μm cellulose acetate membrane filter (Sartorius) (Minisart). Next, the obtained filtrate was put into a 110 ml screw tube (No. 8 manufactured by Marum), and nitrogen gas was blown into the screw tube at room temperature for 30 minutes at 100 ml / min. After sealing the screw tube, The filtrate was allowed to stand at 80 ° C. for 12 hours to obtain an aqueous solution of a colorless and transparent polymer (water-soluble polymer compound No. 10).

The details of the water-soluble polymer compounds No. 11 to 15 and PEG 6000 in Table 1 are as follows.
(Water-soluble polymer compound No. 11)
Polyacrylamide (PAM, weight average molecular weight: 800,000 (catalog value), manufactured by Wako Pure Chemical Industries, Ltd.)
(Water-soluble polymer compound No. 12)
HEC (trade name CF-V, weight average molecular weight: 820,000, manufactured by Sumitomo Seika Co., Ltd.)
(Water-soluble polymer compound No. 13)
HEC (trade name SE400, weight average molecular weight: 250,000, manufactured by Daicel)
(Water-soluble polymer compound No. 14)
Polyvinylpyrrolidone (trade name K-90, weight average molecular weight: 360,000 (catalog value): manufactured by Wako Pure Chemical Industries, Ltd.)
(Water-soluble polymer compound No. 15)
Poly N-vinylformamide (weight average molecular weight: 500,000 (catalog value), manufactured by Kao Corporation)
(PEG6000)
Polyethylene glycol (weight average molecular weight 6000 (catalog value): Wako Pure Chemical Industries, Ltd.)

<Solubility of water-soluble polymer compound>
The solubility of the water-soluble polymer compounds No. 1 to 15 in water at 20 ° C. was 2 g / 100 ml or more.

<Measurement of polymerization average molecular weight>
Water-soluble polymer compound No. The weight average molecular weights of 1 to 10, 12, and 13 were calculated based on the peaks in the chromatogram obtained by applying the gel permeation chromatography (GPC) method under the following conditions.
Equipment: HLC-8320 GPC (Tosoh Corporation, detector integrated type)
Column: TSKgel α-M + TSKgel α-M (cation, manufactured by Tosoh Corporation)
Eluent: LiBr (50 mmol / L (0.43 mass%)) and CH3COOH (166.7 mmol / L (1.0 mass%)) are added to ethanol / water (= 3/7) Flow rate: 0.6 mL / min
Column temperature: 40 ° C
Detector: RI Detector Reference material: Polyethylene glycol

<Average primary particle diameter of abrasive (silica particles)>
The average primary particle diameter (nm) of the abrasive was calculated by the following formula using the specific surface area S (m ² / g) calculated by the BET (nitrogen adsorption) method.
Average primary particle diameter (nm) = 2727 / S

  The specific surface area of the abrasive is subjected to the following [pretreatment], and then approximately 0.1 g of a measurement sample is accurately weighed to 4 digits after the decimal point in a measurement cell, and immediately under the measurement at a specific temperature of 110 ° C. for 30 minutes. After drying, the surface area was measured by a nitrogen adsorption method (BET method) using a specific surface area measuring device (Micromeritic automatic specific surface area measuring device Flowsorb III 2305, manufactured by Shimadzu Corporation).

[Preprocessing]
(A) The slurry-like abrasive is adjusted to pH 2.5 ± 0.1 with an aqueous nitric acid solution.
(B) A slurry-like abrasive adjusted to pH 2.5 ± 0.1 is placed in a petri dish and dried in a hot air dryer at 150 ° C. for 1 hour.
(C) After drying, the obtained sample is finely ground in an agate mortar.
(D) The pulverized sample is suspended in ion exchange water at 40 ° C. and filtered through a membrane filter having a pore size of 1 μm.
(E) The filtrate on the filter is washed 5 times with 20 g of ion exchange water (40 ° C.).
(F) The filter with the filtrate attached is taken in a petri dish and dried in an atmosphere of 110 ° C. for 4 hours.
(G) The dried filtrate (abrasive grains) was taken so as not to be mixed with filter waste, and finely pulverized with a mortar to obtain a measurement sample.

<Average secondary particle diameter of abrasive (silica particles)>
The average secondary particle diameter (nm) of the abrasive is such that the abrasive is added to ion-exchanged water so that the concentration of the abrasive is 0.25% by mass, and then the obtained aqueous solution is disposable sizing cuvette (polystyrene 10 mm). The cell was measured up to a height of 10 mm from the bottom and measured using a dynamic light scattering method (device name: Zetasizer Nano ZS, manufactured by Sysmex Corporation).

(1) Preparation of polishing liquid composition As shown in Table 1, silica particles (colloidal silica, average primary particle diameter 38 nm, average secondary particle diameter 78 nm, association degree 2.1), water-soluble polymer compound, 28% ammonia Water (Kishida Chemical Co., Ltd. reagent grade) and ion-exchanged water were mixed with stirring, and the polishing liquid compositions of Examples 1 to 25 and Comparative Examples 1 to 6 (both concentrated solution, pH 10.6 ± 0.1 (25 ° C.) )). In addition, content of the silica particle and water-soluble polymer compound of Table 1 is a value after diluting the said concentrate with ion-exchange water, respectively (dilution magnification: 40 times). The balance is ion exchange water. The pH of the polishing composition obtained by diluting the concentrated solution with ion-exchanged water was pH 10.6 ± 0.1 (25 ° C.).

(2) Polishing method The polishing liquid composition obtained by diluting the polishing liquid composition (concentrated liquid) 40 times with ion-exchanged water is filtered with a filter (compact cartridge filter MCP-LX-C10S Advantech Co., Ltd.) immediately before polishing. Perform filtration and finish polishing for the following silicon wafer (silicon single-sided mirror wafer with a diameter of 200 mm (conduction type: P, crystal orientation: 100, resistivity 0.1 Ω · cm or more and less than 100 Ω · cm) under the following polishing conditions Prior to the final polishing, the silicon wafer was subjected to rough polishing in advance using a commercially available abrasive composition, and the surface roughness (haze) of the silicon wafer subjected to the final polishing after completion of the rough polishing. The surface roughness (haze) is a dark field wide oblique incidence channel (DWO) measured using Surfscan SP1 (trade name) manufactured by KLA Tencor. Is the value.

<Finishing polishing conditions>
Polishing machine: Single-sided 8-inch polishing machine GRIND-X SPP600s (manufactured by Okamoto)
Polishing pad: Suede pad (Toray Cortex, Asker hardness 64, thickness 1.37mm, nap length 450um, opening diameter 60um)
Wafer polishing pressure: 100 g / cm ²
Surface plate rotation speed: 60 rpm
Polishing time: 5 minutes Supply rate of the abrasive composition: 150 ml / min
Abrasive composition temperature: 20 ° C
Carrier rotation speed: 60rpm

  After finish polishing, the silicon wafer was subjected to ozone cleaning and dilute hydrofluoric acid cleaning as follows. In ozone cleaning, pure water containing 20 ppm ozone was sprayed from a nozzle toward the center of a silicon wafer rotating at 600 rpm at a flow rate of 1 L / min for 3 minutes. At this time, the temperature of the ozone water was normal temperature. Next, dilute hydrofluoric acid cleaning was performed. In dilute hydrofluoric acid cleaning, pure water containing 0.5% ammonium hydrogen fluoride (special grade: Nacalai Tex Co., Ltd.) was sprayed from the nozzle toward the center of the silicon wafer rotating at 600 rpm at a flow rate of 1 L / min for 6 seconds. The above ozone cleaning and dilute hydrofluoric acid cleaning were performed as a set, for a total of 2 sets, and finally spin drying was performed. In the spin drying, the silicon wafer was rotated at 1500 rpm.

<Evaluation of dispersed particle size>
Dispersion of silica particles in the polishing composition using a polishing composition (pH 10.6 ± 0.1 (25 ° C)) obtained by diluting the polishing composition (concentrated solution) 40 times with ion-exchanged water The particle size was measured. As a particle size measuring apparatus used for measuring the dispersed particle size, a particle size distribution measuring instrument “Zetasizer Nano ZS” manufactured by Sysmex Corporation based on the principle of the photon correlation method (dynamic light scattering method) was used. 1.2 mL of the polishing liquid composition was sampled into a Disposable Sizing Cuvette (polystyrene 10 mm cell) as a measurement liquid, and placed in a measurement unit, and the volume median particle diameter (D50) was measured as a dispersed particle diameter. The results are shown in Table 1 below. The smaller the value of D50, the better the dispersibility of the silica particles.

<Evaluation of surface roughness (haze) of silicon wafer>
As the surface roughness (haze) of the cleaned silicon wafer surface, a value in a dark field wide oblique incident channel (DWO) measured using Surfscan SP1 (trade name) manufactured by KLA Tencor was used. The results are shown in Table 1. The evaluation result of the surface roughness (haze) indicates that the smaller the numerical value, the better.

<Evaluation of polishing rate>
The polishing rate was evaluated by the following method. The weight of each silicon wafer before and after polishing was measured using a precision balance ("BP-210S" manufactured by Sartorius), and the obtained weight difference was divided by the density, area and polishing time of the silicon wafer, and unit time The single-side polishing rate per hit was determined. In Table 1, the single-side polishing rate when the polishing composition of Comparative Example 4 was used was “1.0”, and the polishing rate when other polishing compositions were used was shown as a relative value. . The larger the value, the faster the polishing rate. In addition, if it is equal to or faster than the polishing rate of Comparative Example 4, the productivity in actual production is at an acceptable level.

  As shown in Table 1, the surface roughness of the polished silicon wafer (haze) was higher when the polishing liquid compositions of Examples 1 to 25 were used than when the polishing liquid compositions of Comparative Examples 1 to 5 were used. ) Was significantly smaller. Moreover, the polishing rate when the polishing liquid compositions of Examples 1 to 25 are used is larger than that when the polishing liquid compositions of Comparative Examples 2 to 5 are used, which is sufficient for ensuring good productivity. It was fast. In addition, in the polishing liquid compositions of Examples 1 to 25, the size of the dispersed particle diameter was the same as or smaller than that of the polishing liquid compositions of Comparative Examples 1 to 6.

  If the polishing liquid composition of the present invention is used, the surface roughness (haze) of the silicon wafer can be reduced while ensuring a polishing rate that ensures good productivity. Therefore, the polishing liquid composition of the present invention is useful as a polishing liquid composition used in various semiconductor substrate manufacturing processes, and is particularly useful as a polishing liquid composition for finish polishing of silicon wafers.

Claims (8)

Silica particles (component A);
A polishing composition for a silicon wafer, comprising a water-soluble polymer compound (component B) having a structural unit represented by the following general formula (1) and having a weight average molecular weight of 20,000 to 1,000,000.

However, in the general formula (1), R ¹ and R ² each independently represent hydrogen or a monohydroxyalkyl group having 1 to 2 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms, A monohydroxyalkyl group having 1 to 4 carbon atoms or a dihydroxyalkyl group having 1 to 4 carbon atoms, R ⁴ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ⁵ represents hydrogen or Indicates a methyl group. However, the structural unit represented by the general formula (1) contains two or more hydroxyl groups.   The mass ratio of the silica particles (component A) and the water-soluble polymer compound (component B) (the mass of silica particles / the mass of the water-soluble polymer compound (component B)) is 1 to 50. The polishing liquid composition for silicon wafers described in 1.   3. The polishing composition for a silicon wafer according to claim 1, wherein the content of the water-soluble polymer compound (component B) is 0.0005% by mass or more and 1.0% by mass or less.   The polishing liquid composition for silicon wafers according to any one of claims 1 to 3, wherein an amount of the silica particles (component A) added is 0.005 mass% or more and 1.0 mass% or less.   The polishing composition for a silicon wafer according to any one of claims 1 to 4, wherein an average primary particle size of the silica particles (component A) is 5 nm or more and 50 nm or less.   A polishing method comprising a polishing step of polishing a silicon wafer using the polishing composition for a silicon wafer according to any one of claims 1 to 5.   The manufacturing method of a semiconductor substrate including the grinding | polishing process of grind | polishing a silicon wafer using the polishing liquid composition for silicon wafers in any one of Claims 1-5. A silicon wafer polishing additive composition used for preparing the silicon wafer polishing liquid composition according to any one of claims 1 to 5, wherein the composition is represented by the following general formula (1): A silicon wafer polishing additive composition comprising a water-soluble polymer compound containing a unit and having a weight average molecular weight of 20,000 to 1,000,000 and an aqueous medium.

However, in the general formula (1), R ¹ and R ² each independently represent hydrogen or a monohydroxyalkyl group having 1 to 2 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms, A monohydroxyalkyl group having 1 to 4 carbon atoms or a dihydroxyalkyl group having 1 to 4 carbon atoms, R ⁴ represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ⁵ represents hydrogen or Indicates a methyl group. However, the structural unit represented by the general formula (1) contains two or more hydroxyl groups.