JP2016119418A - Polishing liquid composition for silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid composition for a silicon wafer that reduces surface defects (LPD).SOLUTION: The polishing liquid composition for a silicon wafer includes: silicon particles, a nitride-containing basic compound, and a water-soluble polymer containing (1)(2).SELECTED DRAWING: None

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 finish polishing, a polishing liquid composition for chemical mechanical polishing containing colloidal silica and an alkali compound is known. Further, as a polishing composition for the purpose of improving the haze level, a polishing composition for chemical mechanical polishing containing colloidal silica, hydroxyethyl cellulose (HEC) and polyethylene oxide (PEO) is known (patent). Reference 1).

  Further, although the object to be polished is not a silicon wafer, Patent Documents 2 to 4 disclose the following compositions. Patent Document 2 discloses a metal film polishing liquid composition containing a methacrylic acid polymer such as polymethacrylic acid or a copolymer of methacrylic acid and acrylic acid for the purpose of enhancing the flatness of the surface to be polished. ing. In Patent Document 3, the problem to be solved is to increase the polishing selectivity of a single crystal silicon film or a polysilicon film and a silicon oxide film, and a ceria abrasive, polyacrylic acid or polymethacrylic acid as a dispersant, and ionicity A polymer additive, polyacrylic acid or polypropylene oxide methacrylic acid-polyacrylic acid copolymer, and a non-ionic polymer additive, a polyethylene backbone, with two or three polyethylene glycol branched chains attached. A CMP slurry composition comprising a polymer is disclosed. In Patent Document 4, the polishing selectivity of the silicon oxide film with respect to the silicon nitride film is increased, and the problem to be solved is to make the particle size uniform in the CMP slurry and to stabilize the viscosity change, such as polyacrylic acid and polymethacrylic acid. A CMP slurry containing a linear polymer electrolyte containing a carboxyl group and / or a graft type polymer electrolyte such as acrylic acid-methoxypolyethylene glycol monomethacrylate is disclosed (see Patent Document 4).

JP 2004-128089 A JP 2014-160827 A Special table 2013-507786 gazette Special table 2009-518852 gazette

  However, since the polishing liquid composition using HEC uses cellulose, which is a natural product of HEC, a water-insoluble material derived from cellulose is included, and the water-insoluble material serves as a nucleus and the silica particles tend to aggregate. The presence of silica particle aggregates and the water-insoluble matter itself may cause an increase in surface defects (LPD).

  Further, there is a demand for further reduction of surface defects (LPD) in polishing of a silicon wafer to be polished.

  Therefore, in the present invention, a polishing composition for silicon wafer, a method for producing a semiconductor substrate using the polishing composition for silicon wafer, and a silicon wafer that can reduce surface defects (LPD) of the silicon wafer, and silicon wafer A polishing method is provided.

The polishing composition for silicon wafers of the present invention contains the following components A to C.
Component A: Silica particle component B: Nitrogen-containing basic compound Component C: A water-soluble polymer comprising a structural unit I represented by the following general formula (1) and a structural unit II represented by the following general formula (2) .
However, in the general formula (1), R ₁ is hydrogen or a methyl group, M is H, Na, K, or a NH _4, in the general formula (2), n is a average addition molar number 3 or more and 150 or less, R ₂ is hydrogen or a methyl group, and R ₃ is hydrogen or a methyl group.

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

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

  According to the present invention, a silicon wafer polishing liquid composition, a method for manufacturing a semiconductor substrate using the silicon wafer polishing liquid composition, and a silicon wafer that can reduce surface defects (LPD) of the silicon wafer are provided. Can be provided.

  The present invention relates to a structural unit I represented by the following general formula (1) as a polishing aid in a polishing composition for a silicon wafer (hereinafter sometimes abbreviated as “polishing composition”) and the following general formula (1). This is based on the knowledge that when a water-soluble polymer containing the structural unit II represented by the formula (2) is contained, surface defects (LPD) of the silicon wafer can be reduced.

  Although details of the mechanism of the effect of the present invention that can reduce the surface defects (LPD) of the silicon wafer are not clear, the present inventor presumes as follows.

In the polishing liquid composition supplied between the surface of the silicon wafer to be polished and the polishing pad, a larger polishing load is applied to the agglomerated silica particles than to the agglomerated silica particles. For this reason, the aggregates of silica particles are more strongly adsorbed on the surface of the silicon wafer, which is one of the causes of an increase in surface defects (LPD) of the silicon wafer. In the polishing liquid composition of the present invention, a water-soluble polymer (polishing aid) containing an oxyethylene group having an EO addition mole number of 3 to 150 and containing the structural unit II represented by the following general formula (2) is moderate. It exhibits excellent hydrophobicity, is easily adsorbed on a silicon wafer, and forms a protective film on the silicon wafer. On the other hand, since the structural unit I represented by the following general formula (1) has a carboxylic acid group that is anionic and has a negative charge, silica particles having a negative charge on the surface under alkali are formed on a silicon wafer. Is suppressed by charge repulsion. Moreover, aggregation of silica particles is suppressed by the negative charge of the water-soluble polymer. Therefore, it is possible to suppress the silica particles from aggregating on the silicon wafer surface during the polishing and the silica particle agglomerates from adsorbing to the silicon wafer surface. Therefore, if the polishing composition of the present invention is used, the presence of a water-soluble polymer containing the structural unit I represented by the following general formula (1) and the structural unit II represented by the following general formula (2). Since the protective film is formed on the silicon wafer and the adsorption of the silica particle aggregates to the silicon wafer is suppressed, the surface defect (LPD) of the silicon wafer can be reduced at a high level. However, the present invention is not limited to these estimations.

  In one embodiment, the present invention is represented by silica particles (component A), a nitrogen-containing basic compound (component B), a structural unit I represented by the following general formula (1), and the following general formula (2). It is related with the polishing liquid composition for silicon wafers containing the water-soluble polymer (component C) containing the structural unit II. If the polishing liquid composition of the present invention is used, the polishing liquid composition is supplied to the surface to be polished of the substrate to be polished, the polishing pad is brought into contact with the surface to be polished, and at least one of the polishing pad and the substrate to be polished is attached. In the polishing process of the silicon wafer to be polished, which moves and polishes the substrate to be polished, generation of surface defects (LPD) of the silicon wafer can be reduced.

[Silica-containing particles: Component A]
The polishing liquid composition of the present disclosure includes 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. . The average primary particle diameter of the silica particles is preferably 50 nm or less, preferably 45 nm or less, from the viewpoint of ensuring the polishing rate, reducing the surface roughness (haze) of the silicon wafer, and reducing surface defects (LPD). More preferred is 40 nm or less.

  In particular, when colloidal silica is used as the silica particles, the average primary particle diameter of the silica particles is preferably 5 nm or more, more preferably 10 nm or more, further preferably 15 nm or more, and more preferably 30 nm or more from the viewpoint of ensuring the polishing rate. Is even more preferred. Further, from the viewpoint of ensuring the polishing rate, reducing the surface roughness (haze) of the silicon wafer, and reducing the surface defects (LPD), 50 nm or less is preferable, 45 nm or less is more preferable, and 40 nm or less is even more preferable. Further, the average secondary particle diameter of the silica particles is preferably 10 nm or more and 100 nm or less, more preferably 20 nm or more and 90 nm or less, and further preferably 30 nm or more and 80 nm or less from the same viewpoint as described above.

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, and preferably 1.1 or more and 3 from the viewpoint of ensuring the polishing rate and reducing the surface roughness (haze) of the silicon wafer and reducing the surface defects (LPD). Is preferably 0.0 or less, more preferably 1.8 or more and 2.5 or less, and even more preferably 2.0 or more and 2.3 or less. 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 3.0 or less from the viewpoint of ensuring the polishing rate and reducing both the surface roughness (haze) of the silicon wafer and the reduction of surface defects (LPD). Preferably, 1.1 or more and 3.0 or less are more preferable, 1.8 or more and 2.5 or less are more preferable, and 2.0 or more and 2.3 or less 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 composition of the present invention is preferably 0.01% by mass or more, more preferably 0.03 in terms of SiO ₂ from the viewpoint of securing the polishing rate of the silicon wafer. It is at least mass%, more preferably at least 0.05 mass%. Further, from the viewpoint of both reduction of the surface roughness (haze) of the silicon wafer and reduction of surface defects (LPD), it is preferably 0.50% by mass or less, more preferably 0.30% by mass or less in terms of SiO _2. More preferably, it is 0.20 mass% or less.

[Nitrogen-containing basic compound (component B)]
The polishing composition of the present invention is from the viewpoint of improving the storage stability of the polishing composition, ensuring the polishing rate, and reducing the surface roughness (haze) of the silicon wafer and reducing surface defects (LPD). Contains a water-soluble basic compound. 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, and “water-soluble basic compound” means a compound that shows basicity when dissolved in water. .

  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, hexamethylenedia Down, 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. As the nitrogen-containing basic compound that can be contained in the polishing liquid composition of the present invention, both the reduction of the surface roughness (haze) of the silicon wafer and the reduction of surface defects (LPD), the storage stability of the polishing liquid composition Ammonia is more preferable from the viewpoint of improving the property and ensuring the polishing rate.

  The content of the nitrogen-containing basic compound contained in the polishing composition of the present invention can be added so as to have a desired pH, and is preferably added so that the pH is 8.0 or more and 12.0 or less. When pH adjustment is required separately, a pH adjuster described later can be used. Specifically, from the viewpoint of coexistence of reduction of the surface roughness (haze) and surface defect (LPD) of the silicon wafer, improvement of the storage stability of the polishing composition, and securing of the polishing rate, 0. 001% by mass or more is preferable, 0.003% by mass or more is more preferable, 0.005% by mass or more is further preferable, and 0.07% by mass or more is even more preferable. Further, the content of the nitrogen-containing basic compound is preferably 0.1% by mass or less from the viewpoint of coexistence of reduction of the surface roughness (haze) of the silicon wafer and reduction of surface defects (LPD), and 0.05% by mass. % Or less is more preferable, 0.025 mass% or less is further preferable, 0.018 mass% or less is further more preferable, and 0.014 mass% or less is still more preferable.

[Water-soluble polymer (component C)]
The polishing composition of the present disclosure includes a water solution containing a structural unit I represented by the following general formula (1) and a structural unit II represented by the following general formula (2) from the viewpoint of reducing surface defects (LPD). Functional polymer (component C). “Water-soluble” means having a solubility of 2 g / 100 ml or more in water (20 ° C.).

In general formula (1), R ₁ is hydrogen or a methyl group, preferably a methyl group, from the viewpoint of reducing surface defects (LPD). From the viewpoint of reducing surface defects (LPD), M is H, Na, K, or NH ₄ , preferably NH ₄ .

The structural unit II represented by the general formula (2) is a structural unit derived from at least one selected from monomethoxy polyethylene glycol monomethacrylate and monomethoxy polyethylene glycol monoacrylate. In general formula (2), n is the average number of added moles of ethyleneoxy group (EO), and 3 or more, preferably 17 or more, more preferably from the viewpoint of improving the adsorptivity of the water-soluble polymer to the silicon wafer. Is 19 or more, more preferably 20 or more, and from the viewpoint of securing the polishing rate, it is 150 or less, preferably 140 or less, more preferably 135 or less, and still more preferably 130 or less. R ₂ is hydrogen or a methyl group, preferably a methyl group, from the viewpoint of reducing surface defects (LPD), and R ₃ is hydrogen or a methyl group, preferably a methyl group, from the viewpoint of reducing surface defects (LPD). is there.

  From the viewpoint of reducing surface defects (LPD), the mol% of the structural unit I in the total structural units of the water-soluble polymer is preferably 40 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol%. From the viewpoint of reducing surface defects (LPD), it is preferably 99 mol% or less, more preferably 90 mol% or less, and still more preferably 80 mol% or less. The mol% is the average mol% of the structural unit I contained in the copolymer.

  Specific examples of the water-soluble polymer include a copolymer of methacrylic acid and monomethoxypolyethylene glycol monomethacrylate, and a copolymer of methacrylic acid and monomethoxypolyethylene glycol monoacrylate from the viewpoint of reducing surface defects (LPD). Selected from the group consisting of a polymer, a copolymer of acrylic acid and monomethoxypolyethylene glycol monomethacrylate, a copolymer of acrylic acid and monomethoxypolyethylene glycol monoacrylate, their alkali metal salts, and their ammonium salts At least one is preferable, and at least one selected from the group consisting of a copolymer of methacrylic acid and monomethoxypolyethylene glycol monomethacrylate, an alkali metal salt thereof, and an ammonium salt thereof is more preferable. Ammonium salt of copolymer of monomethoxy polyethylene glycol monomethacrylate is more preferable.

  The weight average molecular weight (Mw) of the water-soluble polymer (component C) is preferably 5000 or more, more preferably 10,000 or more, still more preferably 20,000 or more, even more, from the viewpoint of reducing surface defects (LPD). Preferably, it is 40,000 or more, and from the viewpoint of reducing surface defects (LPD), it is preferably 100,000 or less, more preferably 80,000 or less, and still more preferably 65,000 or less. In addition, the weight average molecular weight (Mw) of water-soluble polymer (component B) is the value measured using the gel permeation chromatography (GPC) as described in the below-mentioned Example.

  The content of the water-soluble polymer (component C) in the polishing liquid composition of the present invention is preferably 0.0001% by mass or more, more preferably 0.001% by mass, from the viewpoint of reducing surface defects (LPD). As mentioned above, More preferably, it is 0.003 mass% or more. From the viewpoint of improving the polishing rate, 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 still more preferably 0.04% by mass or less.

  The mass ratio of the water-soluble polymer (component C) and the silica particles (component A) in the polishing liquid composition of the present invention (water-soluble polymer mass / silica particle mass) is a reduction in surface defects (LPD). In view of the above, it is preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.04 or more, and from the viewpoint of ensuring the polishing rate, preferably 0.5 or less, more preferably 0.45. Hereinafter, it is more preferably 0.40 or less.

[Aqueous medium: Component D]
Examples of the aqueous medium 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. The solvent is a solvent that can be mixed with water. (For example, 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 the aqueous medium contained in the polishing composition of the present invention is a mixed medium of water and a solvent, the ratio of water to the entire mixed medium is not particularly limited, but from the viewpoint of economy, Preferably it is 95 mass% or more, More preferably, it is 98 mass% or more, More preferably, it is substantially 100 mass%.

  The content of the aqueous medium (component D) in the polishing liquid composition of the present invention is not particularly limited, but silica particles (component A), a nitrogen-containing basic compound (component B), and water-solubility. What is necessary is just the remainder except a polymer (component C) and the arbitrary component mentioned later.

  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, from the viewpoint of ensuring the polishing rate. 0 or less 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 B) and / or a pH adjuster 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 composition of the present invention, a water-soluble polymer compound (component E) other than the water-soluble polymer compound (component C), a pH adjuster, and a preservative are added as long as the effects of the present invention are not hindered. , Alcohols, chelating agents, anionic surfactants, and at least one optional component selected from nonionic surfactants may be included.

[Water-soluble polymer compound (component E)]
In the polishing composition of the present invention, from the viewpoint of coexistence of reduction of surface roughness (haze) of silicon wafer and reduction of surface defects (LPD), water-soluble high-molecular compounds other than the water-soluble polymer compound (component C) are used. A molecular compound (component E) may be contained. 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 a viewpoint, 10,000 or more are preferable and 100,000 or more are more preferable. 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, polyoxazoline, polydimethylacrylamide, polydiethylacrylamide, polyisopropylacrylamide, polyhydroxyethylacrylamide and the like. 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]
The pH adjustment of the polishing composition of the present disclosure is preferably performed using the nitrogen-containing basic compound (component B) described above. However, when adjusting the polishing composition of the present invention, for example, when the pH is excessively higher than desired, the following pH adjuster can be used. Examples of pH adjusters include acidic compounds. 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. 0.1 mass% or more is preferable and, as for content of alcohol in the polishing liquid composition of this invention, 5 mass% or less is preferable.

[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. 0.01 mass% or more is preferable and, as for content of the chelating agent in the polishing liquid composition of this invention, 1 mass% or less 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 (hardened) castor oil, polyhydric alcohol types such as sucrose fatty acid esters and alkylglycosides, and fatty acid alkanolamides.

[0.45 μm filter flow rate]
When a polishing composition containing a large amount of coarse particles or gelled material is passed through a filter, clogging occurs and the amount of liquid passing decreases. Accordingly, the 0.45 μm filter flow rate of the polishing composition (the flow rate through the filter having a pore diameter of 0.45 μm) is a measure of the abundance of coarse particles and gelled products. In addition, even when the average particle diameter of the primary particles of the silica particles is large, clogging is likely to occur, and the 0.45 μm filter flow rate decreases. Therefore, “0.45 μm filter flow rate” is the average of the primary particles of silica particles. It is suitable as a parameter for comparing polishing liquid compositions having the same particle size.

  From the viewpoint of reducing surface defects (LPD), the 0.45 μm filter flow rate of the polishing composition according to the present disclosure is preferably 100 mL or more, more preferably 120 mL or more, still more preferably 140 mL or more, and 150 ml. The above is even more preferable, and 180 ml or more is even more preferable. Here, the 0.45 μm filter flow rate of the polishing composition can be measured by the method described in Examples.

  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. Is more preferably at least twice, more preferably at least 30 times, more preferably at most 100 times, more preferably at most 80 times, and even more preferably at most 60 times.

When the polishing liquid composition of the present invention is the 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 in terms of SiO _2. 4 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, and still more preferably 20% by mass or less from the viewpoint of improving storage stability in terms of SiO ₂ . 15 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 B) 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 B) in the concentrate is preferably 5% by mass or less, more preferably 2% by mass or less, and still more preferably 1% by mass or less from the viewpoint of improving storage stability. .

  When the polishing liquid composition of the present invention is the concentrated liquid, the content of the water-soluble polymer compound (component C) 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 C) 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. preferable.

  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 liquid composition of the present invention is not limited at all. For example, silica particles (component A), nitrogen-containing basic compound (component B), water-soluble polymer compound (component C), It can be prepared by mixing an aqueous medium (component D) and optional components as required.

  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 the 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 C). Specifically, after preparing a silicon wafer polishing additive composition containing a water-soluble polymer compound (component C) and an aqueous medium (component D), the silicon wafer polishing additive composition, silica particles, And then, if necessary, a mixture of the silicon wafer polishing additive composition and silica particles is preferably diluted with an aqueous medium (component D).

  The polishing liquid composition of the present invention is used, for example, in a method for polishing a silicon wafer including a polishing step for polishing a silicon wafer to be polished and a polishing step for polishing a silicon wafer to be polished 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 to be polished. . An aqueous medium (component D) may be used as the diluent.

  The concentrated solution diluted in the dilution step is, for example, from 2 to 40% by mass of component A, 0.02 to 5% by mass of component B, and component C from the viewpoint of reducing production and transportation costs and improving storage stability. Is preferably contained in an amount of 0.005 to 5 mass%.

  The present invention further discloses the following <1> to <18>.

<1> A silica particle, a nitrogen-containing basic compound, and a water-soluble polymer containing a structural unit I represented by the following general formula (1) and a structural unit II represented by the following general formula (2) A polishing composition for silicon wafers.
However, in the general formula (1), R ₁ is hydrogen or a methyl group, M is H, Na, K, or a NH _4, in the general formula (2), n is a average addition molar number R ₂ is hydrogen or a methyl group, and R ₃ is hydrogen or a methyl group.
<2> The polishing composition for a silicon wafer according to <1>, wherein R ₁ in the general formula (1) is preferably a methyl group.
<3> The polishing composition for a silicon wafer according to <1> or <2>, wherein M in the general formula (1) is preferably NH ₄ .
<4> In the general formula (2), n is preferably 17 or more, more preferably 19 or more, still more preferably 20 or more, preferably 140 or less, more preferably 135 or less, and still more preferably 130 or less. The polishing composition for a silicon wafer according to any one of <1> to <3>.
<5> The polishing composition for a silicon wafer according to any one of <1> to <4>, wherein R ₂ in the general formula (2) is preferably a methyl group.
<6> The silicon wafer polishing composition according to any one of <1> to <5>, wherein R ₃ in the general formula (2) is preferably a methyl group.
<7> The water-soluble polymer is preferably a copolymer of methacrylic acid and monomethoxypolyethylene glycol monomethacrylate, a copolymer of methacrylic acid and monomethoxypolyethylene glycol monoacrylate, acrylic acid and monomethoxypolyethylene glycol. It is at least one selected from the group consisting of a copolymer of monomethacrylate, a copolymer of acrylic acid and monomethoxypolyethylene glycol monoacrylate, an alkali metal salt thereof, and an ammonium salt thereof, and more preferably It is at least one selected from the group consisting of a copolymer of methacrylic acid and monomethoxypolyethylene glycol monomethacrylate, its alkali metal salt, and its ammonium salt, more preferably methacrylic acid and monomethoxypolyethylene. A copolymer of an ammonium salt of a recall monomethacrylate, the silicon wafer for the polishing liquid composition according to <1>.
<8> The mol% of the structural unit I in all the structural units in the water-soluble polymer is preferably 40 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more, preferably 99 The polishing composition for a silicon wafer according to any one of <1> to <7>, wherein the polishing composition is at most mol%, more preferably at most 90 mol%, still more preferably at most 80 mol%.
<9> The weight average molecular weight (Mw) of the water-soluble polymer is preferably 5000 or more, more preferably 10,000 or more, still more preferably 20,000 or more, still more preferably 40,000 or more, and preferably 100,000. Hereinafter, the polishing composition for a silicon wafer according to any one of <1> to <8>, more preferably 80,000 or less, and further preferably 65,000 or less.
<10> The mass ratio between the water-soluble polymer and the silica particles (the mass of the water-soluble polymer / the mass of the silica particles) is preferably 0.01 or more, more preferably 0.02 or more, and still more preferably 0. 0.04 or more, preferably 0.5 or less, more preferably 0.45 or less, and even more preferably 0.40 or less, the polishing liquid for silicon wafers according to any one of <1> to <9> above Composition.
<11> The content of the water-soluble polymer contained in the silicon wafer polishing composition is preferably 0.001% by mass or more, more preferably 0.003% by mass or more, and further preferably 0.005% by mass. From the above <1>, preferably 1% by mass or less, more preferably 0.8% by mass or less, further preferably 0.5% by mass or less, and still more preferably 0.2% by mass or less. The polishing composition for silicon wafers according to any one of 10>.
<12> The content of the silica particles contained in the silicon wafer polishing composition is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and still more preferably 0.02% by mass in terms of SiO 2. Any one of the above <1> to <11>, which is 05% by mass or more, preferably 0.50% by mass or less, more preferably 0.30% by mass or less, and still more preferably 0.20% by mass or less. The polishing composition for silicon wafers as described.
<13> The content of the nitrogen-containing basic compound contained in the silicon wafer polishing composition is preferably 0.001% by mass or more, more preferably 0.003% by mass or more, and further preferably 0.005% by mass. % Or more, still more preferably 0.07% by mass or more, preferably 0.1% by mass or less, more preferably 0.05% by mass or less, still more preferably 0.025% by mass or less, and still more preferably 0%. The polishing composition for a silicon wafer according to any one of <1> to <12>, which is 0.018% by mass or less, and still more preferably 0.014% by mass or less.
<14> 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, The polishing composition for a silicon wafer according to any one of <1> to <13>, which is preferably 40 nm or less.
<15> The pH of the polishing composition for a silicon wafer at 25 ° C. is preferably 8.0 or more, more preferably 9.0 or more, still more preferably 9.5 or more, preferably 12.0 or less. More preferably, it is 11.5 or less, More preferably, it is 11.0 or less, The polishing liquid composition for silicon wafers in any one of said <1> to <14>.
<16> The 0.45 μm filter flow rate of the polishing composition for silicon wafer is preferably 100 mL or more, more preferably 120 mL or more, still more preferably 140 mL or more, still more preferably 150 ml or more, and even more preferably 180 ml. The polishing composition for a silicon wafer according to any one of <1> to <15>, which is as described above.
<17> A method for polishing a silicon wafer, comprising a polishing step of polishing a coated polished silicon wafer using the polishing composition for a silicon wafer according to any one of <1> to <16>.
<18> A method for producing a semiconductor substrate, comprising a polishing step of polishing a coated polished silicon wafer using the polishing composition for a silicon wafer according to any one of <1> to <16>.

1. Example of Synthesis of Monomethoxy Polyethylene Glycol Monomethacrylate PEGMA (EO average addition mole number 120) was synthesized by esterification reaction according to the method described in Japanese Patent No. 387494917, and residual methacrylic acid as an unreacted product was retained. Lastly, less than 1% by weight was used. In addition, about PEGMA of EO average addition mole number 9 and 23, the commercial item (made by Kyoeisha Chemical) was used.

2. Method for synthesizing water-soluble polymer or its details
[Method of synthesizing water-soluble polymer (1)]
A reactor equipped with a thermometer, stirrer, dripping device, nitrogen introduction tank, and cooling tank was charged with 281.4 g of distilled water, the inside of the reactor was purged with nitrogen while stirring the distilled water, and distilled water was added in a nitrogen atmosphere. The temperature was raised to 80 ° C. Subsequently, 336.5 g of PEGMA (EO average addition mole number 120), 22.2 g of methacrylic acid and 1.89 g of 2-mercaptoethanol were dissolved in 238.2 g of water, and two were dissolved in 3.68 g of ammonium persulfate in 45 g of water. Each was dropped into the reactor over 1.5 hours. Subsequently, 1.47 g of ammonium persulfate dissolved in 15 g of water was dropped into the reactor over 30 minutes, and then aged at the same temperature (80 ° C.) for 1 hour. After completion of aging, neutralization was performed with 18.7 g of 48% by mass sodium hydroxide to obtain a copolymer of methacrylic acid (MAA) / monomethoxypolyethylene glycol monomethacrylate (PEGMA) (molar ratio: 95/5, weight average molecular weight 65611). It was. Thereafter, the solid content was adjusted with water to obtain an aqueous solution of the water-soluble polymer (1) having a solid content concentration of 10%.

[Method of synthesizing water-soluble polymers (2) to (4)]
The MAA / PEGMA copolymer was prepared in the same manner as in [Synthesis of water-soluble polymer (1)] except that the amounts of monomers PEGMA (EO average addition mole number 120) and methacrylic acid were changed. Similarly, the solid content was adjusted with water to obtain aqueous solutions of water-soluble polymers (2) to (4) having a solid content concentration of 10%.

[Method of synthesizing water-soluble polymer (5)]
A reactor equipped with a thermometer, a stirrer, a dripping device, a nitrogen introduction tank, and a cooling tank was charged with 281.4 g of distilled water, and the inside of the reactor was purged with nitrogen while stirring the distilled water, and distilled water in a nitrogen atmosphere. The temperature was raised to 80 ° C. Subsequently, 336.5 g of PEGMA (EO average addition mole number 23), 22.2 g of methacrylic acid and 1.89 g of 2-mercaptoethanol were dissolved in 238.2 g of water, and 2.68 g of ammonium persulfate dissolved in 45 g of water. Each was dropped into the reactor over 1.5 hours. Subsequently, 1.47 g of ammonium persulfate dissolved in 15 g of water was dropped into the reactor over 30 minutes, and then aged at the same temperature (80 ° C.) for 1 hour. After completion of aging, neutralization was performed with 18.7 g of 48% by mass sodium hydroxide to obtain a copolymer of methacrylic acid (MAA) / monomethoxypolyethylene glycol monomethacrylate (PEGMA) (molar ratio: 73/27, weight average molecular weight 40147). It was. Thereafter, the solid content was adjusted with water to obtain an aqueous solution of the water-soluble polymer (5) having a solid content concentration of 10%.

[Method of synthesizing water-soluble polymer (6)]
A reactor equipped with a thermometer, a stirrer, a dripping device, a nitrogen introduction tank, and a cooling tank was charged with 281.4 g of distilled water, and the inside of the reactor was purged with nitrogen while stirring the distilled water, and distilled water in a nitrogen atmosphere. The temperature was raised to 80 ° C. Subsequently, 336.5 g of PEGMA (EO average addition mole number 9), 22.2 g of methacrylic acid and 1.89 g of 2-mercaptoethanol were dissolved in 238.2 g of water, and 2.68 g of ammonium persulfate dissolved in 45 g of water. Each was dropped into the reactor over 1.5 hours. Subsequently, 1.47 g of ammonium persulfate dissolved in 15 g of water was dropped into the reactor over 30 minutes, and then aged at the same temperature (80 ° C.) for 1 hour. After completion of aging, neutralization was performed with 18.7 g of 48% by mass sodium hydroxide to obtain a methacrylic acid (MAA) / monomethoxypolyethylene glycol monomethacrylate (PEGMA) (molar ratio: 47/53, weight average molecular weight 51347) copolymer. It was. Thereafter, the solid content was adjusted with water to obtain an aqueous solution of the water-soluble polymer (6) having a solid content concentration of 10%.

The following commercially available products were used for the water-soluble polymers (7) and (8), respectively.
Water-soluble polymer (7): HEC (hydroxyethyl cellulose, manufactured by Sumitomo Seika Co., Ltd., CF-V, weight average molecular weight 1129157)
Water-soluble polymer (8): PEG6000 (polyethylene glycol, weight average molecular weight 6000, manufactured by Wako Pure Chemical Industries, Ltd.)

[Method of synthesizing water-soluble polymer (9)]
A homopolymer of water-soluble polymer (9) monomethoxypolyethylene glycol monomethacrylate was synthesized with reference to the description in JP-A-2012-167053. The weight average molecular weight was adjusted by adjusting the concentration of the polymerization initiator.

[Method of synthesizing water-soluble polymer (10)]
Polymethacrylic acid (weight average molecular weight 42215) was obtained in the same manner as in [Method for synthesizing water-soluble polymer (1)] except that the monomer type was only methacrylic acid, and the solid content was similarly adjusted with water. An aqueous solution of a water-soluble polymer (10) having a solid content concentration of 10% was obtained.

3. Various measurement methods <Solubility of water-soluble polymers (1) to (10)>
The solubility of water-soluble polymers (1) to (10) in water at 20 ° C. was 2 g / 100 ml or more.

<Method for measuring weight average molecular weight of water-soluble polymer>
The measuring method of the weight average molecular weight of the water-soluble polymer used for the preparation of the polishing liquid composition is as follows. The weight average molecular weight of the water-soluble polymer was measured under the following conditions by gel permeation chromatography (GPC) using liquid chromatography (manufactured by Hitachi, Ltd., L-6000 type high performance liquid chromatography).
Detector: Shodex RI SE-61 differential refractive index detector Column: G4000PWXL and G2500PWXL manufactured by Tosoh Corporation were connected in series.
Eluent: 0.2 M phosphate buffer / acetonitrile = 90/10 (volume ratio) was adjusted to a concentration of 0.5 g / 100 mL, and 20 μL was used.
Column temperature: 40 ° C
Flow rate: 1.0 mL / min
Standard polymer: Monodispersed polyethylene glycol with known molecular weight

<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 that filter waste was not mixed 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 Silica particles (colloidal silica, average primary particle size 35 nm, average secondary particle size 70 nm, association degree 2), water-soluble polymer, 28% by mass ammonia water (Kishida Chemical Co., Ltd. reagent) Special grade) and ion-exchanged water were stirred and mixed to obtain the polishing composition of Examples 1 to 12 and Comparative Examples 1 to 3 (both concentrated solutions, pH 10.6 ± 0.1 (25 ° C.)). The remainder excluding silica particles, water-soluble polymer, and ammonia is ion-exchanged water. The amount of ammonia added was such that the pH (25 ° C.) of the concentrate was 10.6 ± 0.1. In addition, content of each component in Table 1 is a value about the polishing liquid composition obtained by diluting the concentrated liquid 40 times, and content of the silica particles is a SiO ₂ equivalent concentration.

(2) Polishing method A polishing composition (pH 10.6 ± 0.1 (25 ° C)) obtained by diluting the polishing composition (concentrated solution) 40 times with ion-exchanged water is filtered (compact cartridge filter) immediately before polishing. Filtered with MCP-LX-C10S Advantech Co., Ltd. and under the following polishing conditions, the following silicon wafer (silicon single-sided mirror wafer with a diameter of 200 mm (conductivity type: P, crystal orientation: 100, resistivity 0.1 Ω · cm) More than 100Ω · cm)) was finished. Prior to the final polishing, rough polishing was performed on the silicon wafer in advance using a commercially available abrasive composition. The surface roughness (haze) of the silicon wafer subjected to the final polishing after the completion of the rough polishing was 2.680 ppm. The surface roughness (haze) is a value in a dark field wide oblique incidence channel (DWO) measured using Surfscan SP1-DLS (trade name) manufactured by KLA Tencor.

<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)
Silicon wafer polishing pressure: 100 g / cm ²
Surface plate rotation speed: 60 rpm
Polishing time: 5 minutes Supply rate of the abrasive composition: 150 g / cm ²
Abrasive composition temperature: 23 ° 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, an aqueous solution containing 20 ppm of ozone was sprayed from a nozzle at a flow rate of 1 L / min for 3 minutes toward the center of a silicon wafer rotating at 600 rpm. At this time, the temperature of the ozone water was normal temperature. Next, dilute hydrofluoric acid cleaning was performed. In dilute hydrofluoric acid cleaning, an aqueous solution containing 0.5 mass% ammonium hydrogen fluoride (special grade: Nacalai Tex Co., Ltd.) was sprayed from the nozzle at a flow rate of 1 L / min for 6 seconds toward the center of a silicon wafer rotating at 600 rpm. . 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.

[PH measurement of polishing liquid composition]
The pH value of the polishing composition at 25 ° C. is a value measured using a pH meter (Toa Denpa Kogyo Co., Ltd., HM-30G), and is a value one minute after the electrode is immersed in the polishing composition. is there.

[Evaluation of silicon wafer surface defects (LPD)]
The surface defect (LPD) on the silicon wafer surface after cleaning is measured by measuring the number of particles with a particle diameter of 45 nm or more on the surface of the silicon wafer using Surfscan SP1-DLS (trade name) manufactured by KLA Tencor. evaluated. It shows that there are few surface defects, so that the numerical value (number of particles) of LPD is small. The results of surface defects (LPD) are shown in Table 1. The surface defect (LPD) was measured on each of two silicon wafers, and the average values are shown in Table 1.

[Measurement method of 0.45 μm filter flow rate]
A polishing liquid composition obtained by diluting the polishing liquid composition (concentrated liquid) 40 times with ion-exchanged water was subjected to a predetermined filter (hydrophilic PTFE0. Manufactured by Advantech Co., Ltd.) under a constant pressure of 0.25 MPa. The solution was passed through a 45 (pore diameter) μm filter, model: 25HP045AN, and the amount of liquid per minute (ml) was determined as the MF value. In addition, the 0.45 micrometer filter flow volume by this condition can be used as an parameter | index of being able to reduce a surface defect (LPD), when used for preparation of polishing liquid composition. That is, it can be evaluated that the higher the MF value is, the polishing composition that can reduce surface defects (LPD).

[Evaluation of dispersed particle size of silica particles in polishing composition]
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 composition was sampled into a Disposable Sizing Cuvette (polystyrene 10 mm cell) as a measurement solution, and placed in a measurement unit, and the Z average particle size was measured as a dispersed particle size. The results are shown in Table 1 below. The smaller the value of the Z average particle diameter, the better the dispersibility of the silica particles.

[Amount of water-soluble polymer adsorbed on the silicon wafer surface]
5 g of a silicon wafer pulverized product (pulverized to a size of about 1 mm ³ ) is immersed in 20 ml of a water-soluble polymer aqueous solution adjusted to 0.02% by mass. After immersion for 30 minutes, the solution is passed through a predetermined filter (hydrophilic PTFE 0.45 (pore diameter) μm filter, model: 25HP045AN, manufactured by Advantech), and the total carbon content (TOC) of the filtrate is all organic carbon manufactured by Shimadzu Corporation. Measured with a meter (TOC-5050A). The smaller the value, the greater the amount of water-soluble polymer adsorbed on the silicon wafer, and it can be evaluated as a water-soluble polymer capable of reducing surface defects (LPD).

  As shown in Table 1, by using the polishing liquid compositions of Examples 1 to 12, surface defects (LPD) can be reduced as compared with the case of using the polishing liquid compositions of Comparative Examples 1 to 3. Became.

  If the polishing composition of the present invention is used, the surface defects (LPD) of the silicon wafer can be reduced. 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 (5)

A silicon wafer comprising silica particles, a nitrogen-containing basic compound, and a water-soluble polymer containing a structural unit I represented by the following general formula (1) and a structural unit II represented by the following general formula (2) Polishing liquid composition.
However, in the general formula (1), R ₁ is hydrogen or a methyl group, M is H, Na, K, or a NH _4, in the general formula (2), n is a average addition molar number R ₂ is hydrogen or a methyl group, and R ₃ is hydrogen or a methyl group.   2. The silicon according to claim 1, wherein the water-soluble polymer is at least one selected from the group consisting of a copolymer of methacrylic acid and monomethoxypolyethylene glycol monomethacrylate, an alkali metal salt thereof, and an ammonium salt thereof. Polishing liquid composition for wafers.   The polishing composition for silicon wafers according to claim 1 or 2, wherein the mol% of the structural unit I in all the structural units in the water-soluble polymer is 40 mol% or more and 99 mol% or less.   A method for polishing a silicon wafer, comprising a polishing step of polishing a coated polished silicon wafer using the polishing composition for a silicon wafer according to any one of claims 1 to 3.   The manufacturing method of a semiconductor substrate including the grinding | polishing process of grind | polishing a covering grinding | polishing silicon wafer using the polishing liquid composition for silicon wafers in any one of Claims 1-3.