JP2018107263A - Polishing liquid composition for silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid composition for a silicon wafer, which enables the stable development of a high polishing speed.SOLUTION: A polishing liquid composition for a silicon wafer comprises: silica particles; a quaternary ammonium compound; and a water-soluble polymer. The number of carbon atoms of a quaternary ammonium group of the quaternary ammonium compound is 10 or more and 22 or less. The ratio of a total mole number of Nions of the quaternary ammonium compound to a total mole number of silanol groups of the silica particles is 0.005 or more and 2.00 or less. The quaternary ammonium compound is a compound represented by the formula (1), where R, R, Rand Rrepresent hydrocarbon groups with C1-18, which may be the same or not; Xrepresents a counter ion; and the total number of carbon atoms of R, R, Rand Ris 10 or more and 22 or less.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.

  Along with the advanced information society, the performance of information materials has become excellent year by year. Various substrates are used for these information materials, and a polishing process is indispensable in order to achieve their surface quality efficiently. In the polishing process, since removal of scratches on the substrate surface and high productivity are required, many inventions aimed at improving the polishing rate have been made. For example, for polishing the surface of a silicon wafer, a polishing liquid composition containing hydroxyethyl cellulose (HEC) and tetrabutylammonium hydroxide (TBAH) (Patent Document 1) or an alkali as an additive for the purpose of improving the polishing rate. Polishing composition containing a metal hydroxide (Patent Document 2), containing 1,2,4-triazole and a basic compound, for a semiconductor substrate having a basic compound content of 0.1% by mass or more A polishing liquid (Patent Document 3) is disclosed. For the purpose of reducing haze, a semiconductor polishing composition containing a quaternary ammonium compound, preferably tetramethylammonium hydroxide (TMAH), and having a quaternary ammonium compound content of 0.5 ppm to 100 ppm. (Patent Document 4).

WO2015 / 005433 JP 2001-3036 A WO 2010/122985 JP 2006-352043 A

  In the polishing composition disclosed in Patent Document 1 or 3, from the viewpoint of improving the polishing rate, even if TBAH or a basic compound is contained, a sufficient polishing rate may not be obtained.

  The polishing composition disclosed in Patent Document 2 contains a large amount of alkali metal, and is insufficiently adapted for polishing silicon wafers.

  In the polishing composition disclosed in Patent Document 4, although the haze can be reduced by including TMAH, the polishing rate is lowered.

  The present invention provides a polishing composition for a silicon wafer that exhibits a high polishing rate, a method for producing a semiconductor substrate using the same, and a method for polishing a silicon wafer.

The polishing composition for a silicon wafer of the present invention includes silica particles, a quaternary ammonium compound, and a water-soluble polymer.
The quaternary ammonium group of the quaternary ammonium compound has 10 to 22 carbon atoms,
In the polishing composition, the ratio [b / a] of the total number of moles of N ⁺ of the quaternary ammonium compound (b) and the number of moles of silanol groups of the silica particles (a) is 0.00. 005 or more and 2.00 or less.

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

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

  ADVANTAGE OF THE INVENTION According to this invention, the polishing composition for silicon wafers which expresses a high polishing rate, the manufacturing method of a semiconductor substrate using the same, and the polishing method of a silicon wafer can be provided.

Hereinafter, the present invention will be described more specifically. The present invention provides a specific polishing liquid composition for silicon wafers (hereinafter sometimes simply referred to as “polishing liquid composition”) containing silica particles, a quaternary ammonium compound, and a water-soluble polymer. A total number of moles (b) of N ⁺ of the quaternary ammonium compound in the polishing composition comprising a quaternary ammonium compound, and a total number of moles (a) of silanol groups (SiOH groups) of the silica particles; This is based on the knowledge that a high polishing rate can be expressed by defining the ratio [b / a].

<Silica particles>
The polishing composition of the present invention contains silica particles as abrasive grains. The silica particles are not particularly limited as long as they are particles generally used for polishing, and preferably include colloidal silica and fumed silica. Among these, colloidal silica is more preferable from the viewpoint of improving the surface smoothness of the substrate.

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

From the viewpoint of maintaining a constant polishing rate and surface roughness, 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, and even more preferably 15 nm or more, 20 nm or more is still more preferable, and from the viewpoint of suppressing the occurrence of scratches, 100 nm or less is preferable, 90 nm or less is more preferable, 80 nm or less is further preferable, and 70 nm or less is even more preferable. The average primary particle diameter of the silica particles is calculated using a specific surface area S (m ² / g) calculated by the BET (nitrogen adsorption) method.

  From the viewpoint of improving the polishing rate, the content of silica particles in the polishing composition of the present invention is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and further 0.25% by mass or more. From the viewpoint of improving the storage stability of the polishing composition, it is preferably 2.5% by mass or less, more preferably 1.5% by weight or less, and further preferably 1.0% by weight or less.

  From the viewpoint of improving the storage stability of the polishing composition, the number of silanol groups per gram of silica particles is preferably 0.01 mmol / g or more, more preferably 0.03 mmol / g or more, and further 0.05 mmol / g or more. From the viewpoint of improving the polishing rate, 4.0 mmol / g or less is preferable, 3.0 mmol / g or less is more preferable, and 2.5 mmol / g or less is even more preferable. The number of silanol groups in the silica particles is a value measured by thermogravimetry / differential thermal analysis (TG-DTA), and can be measured, for example, using the apparatus described in the examples.

  The association degree of the silica particles is preferably 1.1 or more, more preferably 1.5 or more, still more preferably 1.8 or more from the viewpoint of improving the polishing rate, and 3.0 from the viewpoint of reducing the surface roughness. The following is preferable, 2.7 or less is more preferable, and 2.5 or less is more preferable. When the silica particles are colloidal silica, the degree of association is preferably 1.1 to 3.0, more preferably 1.5 to 2.7, and more preferably 1.8 to 2.1, from the viewpoint of further improving the polishing rate. 5 is more preferable.

The association degree of the silica particles is a coefficient representing the shape of the abrasive grains and is calculated by the following formula.
The degree of association = average secondary particle diameter / average primary particle diameter 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.

<Quaternary ammonium compound>
The polishing composition of the present invention contains a quaternary ammonium compound from the viewpoint of improving the polishing rate. The quaternary ammonium group of the quaternary ammonium compound has 10 to 22 carbon atoms. The quaternary ammonium group becomes a quaternary ammonium compound when accompanied by a counter ion. The quaternary ammonium compound is preferably a compound represented by the following formula (1), preferably a hydroxide or a quaternary ammonium salt.

In the above formula (1), R ¹ , R ² , R ³ and R ⁴ are the same or different and preferably represent a hydrocarbon group having 1 to 18 carbon atoms from the viewpoint of improving the polishing rate. The number of carbon atoms of the hydrocarbon group is preferably 1 or more from the same viewpoint, more preferably 2 or more, still more preferably 3 or more, and from the same viewpoint, 7 or less is preferable, 6 or less is more preferable, 5 The following is more preferable. From the viewpoint of improving the polishing rate, the hydrocarbon group is preferably an alkyl group, and the number of carbon atoms of the alkyl group is preferably 1 or more, more preferably 2 or more, still more preferably 3 or more, and From the same viewpoint, 7 or less is preferable, 6 or less is more preferable, and 5 or less is more preferable. The total carbon number of R ¹ , R ² , R ³ and R ⁴ is 10 or more and 22 or less, and all of R ¹ , R ² , R ³ and R ⁴ are not simultaneously hydrocarbon groups having 1 to 2 carbon atoms. .

X ⁻ represents a counter ion, and from the viewpoint of easy availability, a hydroxide ion, a halide ion, a sulfate ion, a nitrate ion, a phosphate ion, an organic acid ion, and the like are preferable. From the viewpoint of improving the polishing rate, At least one of hydroxide ions and halide ions is more preferable, and hydroxide ions are still more preferable. Examples of the halide ion include Cl ⁻ , Br ⁻ , ClO ₄ ⁻ , BH ₄ ^{− and the} like.

The carbon number of the quaternary ammonium group of the quaternary ammonium compound is 10 or more from the viewpoint of improving the polishing rate, preferably 12 or more, more preferably 14 or more, and 22 from the viewpoint of ensuring hydrophilicity. Or less, preferably 20 or less, and more preferably 18 or less. The same applies to the total carbon number of R ¹ , R ² , R ³ and R ^{4 in} the formula (1).

  Specific examples of the quaternary ammonium compound include tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tetrapentylammonium, tetrahexylammonium, tetraheptylammonium, capryltrimethylammonium, lauryltrimethylammonium, myristyltrimethylammonium, Examples thereof include hydroxides and salts thereof such as cetyltrimethylammonium and stearyltrimethylammonium. These quaternary ammonium compounds may be used alone or in combination of two or more. The quaternary ammonium compound contained in the polishing liquid composition of the present invention includes tetrapropylammonium, tetrabutylammonium, tetrapentylammonium, and lauryl from the viewpoint of improving the polishing rate and improving the storage stability of the polishing liquid composition. More preferred are hydroxides or salts of trimethylammonium, more preferred are hydroxides or halides of tetrapropylammonium, tetrabutylammonium, tetrapentylammonium, and lauryltrimethylammonium, tetrapropylammonium, tetrabutylammonium, Tetrapentylammonium and lauryltrimethylammonium hydroxides are even more preferred, and tetrabutylammonium hydroxide is even more preferred.

  The content of the quaternary ammonium compound in the polishing liquid composition of the present invention is preferably 1 ppm by mass or more, more preferably 10 ppm by mass or more, still more preferably 50 ppm by mass or more, from the viewpoint of improving the polishing rate. From the viewpoint of reducing the surface roughness and improving the storage stability of the polishing composition, it is preferably 1,000 ppm by mass or less, more preferably 500 ppm by mass or less, and still more preferably 400 ppm by mass or less.

<Water-soluble polymer>
The polishing liquid composition of the present invention contains a water-soluble polymer. The type of the water-soluble polymer is not particularly limited, and can be appropriately selected from known water-soluble polymers included in the polishing composition. Here, “water-soluble” means having a solubility of 2 g / 100 mL or more in water (20 ° C.). The water-soluble polymer can be used alone or in combination of two or more.

  The water-soluble polymer contained in the polishing liquid composition of the present invention is preferably a polymer having an amide group, a cellulose derivative, a polyvinyl alcohol polymer, etc., from the viewpoint of improving the polishing rate, and a polymer having an amide group, A cellulose derivative is more preferred, a cellulose derivative is still more preferred, and hydroxyethyl cellulose is even more preferred.

The polymer having an amide group preferably contains a structural unit represented by the following general formula (2).

R ⁵ and R ⁶ in the above formula (2) each independently represent hydrogen, a hydrocarbon group having 1 to 8 carbon atoms, or a hydroxyalkyl group having 1 to 2 carbon atoms. Preferably R ⁵ and R ⁶ do not simultaneously become hydrogen.

  The monomer that is a source of the structural unit represented by the formula (2) is preferably N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, N-isopropylacrylamide, N-butylacrylamide, for example. N-isobutylacrylamide, N-tertiarybutylacrylamide, N-heptylacrylamide, N-octylacrylamide, N-tertiaryoctylacrylamide, N-methylolacrylamide, N-hydroxyethylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dipropylacrylamide, N, N-diisopropylacrylamide, N, N-dibutylacrylamide, N, N-diisobutylacrylamide, N, N-ditersharib Ruacrylamide, N, N-diheptylacrylamide, N, N-dioctylacrylamide, N, N-ditertioctylacrylamide, N, N-dioctadecylacrylamide, N, N-dimethylolacrylamide, and N, N-dihydroxyethyl One or more selected from acrylamide. Among these monomers, N-hydroxyethylacrylamide is more preferable from the viewpoint of improving the polishing rate and reducing surface defects.

  Specific examples of the cellulose derivative include carboxymethyl cellulose, hydroxyethyl cellulose (HEC), hydroxyethyl methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl ethyl cellulose, and carboxymethyl ethyl cellulose.

  Specific examples of the polyvinyl alcohol polymer include polyvinyl alcohol (PVA), alkylene oxide-modified PVA, cation-modified PVA, anion-modified PVA, and alkyl-modified PVA.

  The weight average molecular weight of the polymer having an amide group is preferably 10,000 to 2,000,000, more preferably 100,000 to 900,000, more preferably 200,000 to 200,000, from the viewpoint of improving the polishing rate and improving the storage stability of the polishing composition. 800,000 is more preferable.

  The weight average molecular weight of hydroxyethyl cellulose is preferably 100,000 to 1,500,000, more preferably 200,000 to 1,000,000, and further preferably 240,000 to 900,000 from the viewpoint of improving the polishing rate and improving the storage stability of the polishing composition. preferable.

  The weight average molecular weight of the polyvinyl alcohol is preferably 10,000 to 150,000, more preferably 15,000 to 100,000, and more preferably 20,000 to 80,000 from the viewpoint of improving the polishing rate and improving the storage stability of the polishing composition. Is more preferable.

  Here, the weight average molecular weight of the water-soluble polymer is a value measured by gel permeation chromatography, and can be measured using, for example, the apparatus described in Examples.

  The content of the water-soluble polymer in the polishing composition of the present invention is preferably 1 ppm by mass or more, more preferably 5 ppm by mass or more, and more preferably 10 ppm by mass or more from the viewpoint of reducing the surface roughness and improving the wettability. Is more preferable, and from the viewpoint of improving the polishing rate and the storage stability of the polishing composition, it is preferably 1000 ppm by mass or less, more preferably 800 ppm by mass or less, and even more preferably 600 ppm by mass or less.

<Aqueous medium>
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 includes a solvent that can be mixed with water ( For example, alcohol such as ethanol is preferable. As the aqueous medium, ion-exchanged water or ultrapure water is more preferable, and ultrapure water is more preferable. When the aqueous medium is a mixed medium of water and a solvent, the ratio of water to the entire mixed medium is preferably 95% by mass or more, more preferably 98% by mass or more, and substantially 100% by mass from the viewpoint of economy. Is more preferable.

  The content of the aqueous medium in the polishing liquid composition of the present invention is preferably the remainder of silica particles, a water-soluble polymer, a quaternary ammonium compound and optional components described below.

<Optional component>
The polishing liquid composition of the present embodiment further contains at least one optional component selected from pH adjusters, preservatives, alcohols, chelating agents, and oxidizing agents as long as the effects of the present invention are not hindered. May be.

(PH adjuster)
Examples of the pH adjuster include acidic compounds and salts thereof. 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. The salt of the acidic compound is preferably at least one selected from alkali metal salts, ammonium salts, and amine salts, and more preferably ammonium salts.

(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.

(Alcohol)
Examples of alcohols include methanol, ethanol, propanol, butanol, isopropyl alcohol, 2-methyl-2-propanool, ethylene glycol, propylene glycol, polyethylene glycol, glycerin and the like. As for content of alcohol in the polishing liquid composition of this invention, 0.1-5 mass% 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. As for content of the chelating agent in the polishing liquid composition of this invention, 0.01-1 mass% is preferable.

(Oxidant)
Examples of the oxidizing agent include peroxides such as permanganic acid and peroxo acid, chromic acid, nitric acid, and salts thereof.

<Polishing liquid composition>
The ratio [b / a] of the total number of moles of N ⁺ of the quaternary ammonium compound (b) and the total number of moles of silanol groups of the silica particles (a) in the polishing composition is a high polishing rate. From the viewpoint of expression, it is 0.005 or more, preferably 0.200 or more, more preferably 0.500 or more, and from the same viewpoint, it is 2.00 or less, preferably 1.70 or less, and 1. 30 or less is more preferable.

  The mass ratio of the quaternary ammonium compound to the silica particles (quaternary ammonium compound / silica particles) in the polishing composition is preferably 0.02 or more, more preferably 0.04 or more, from the viewpoint of improving the polishing rate. Preferably, 0.05 or more is more preferable, and from the same viewpoint, 0.16 or less is preferable, 0.13 or less is more preferable, and 0.11 or less is more preferable.

  The mass ratio of the water-soluble polymer to the quaternary ammonium compound (water-soluble polymer / quaternary ammonium compound) in the polishing composition is preferably 0.15 or more from the viewpoint of improving the polishing rate. 17 or more is more preferable, 0.19 or more is more preferable, and from the same viewpoint, 50 or less is preferable, 8 or less is more preferable, and 1 or less is more preferable.

  The pH at 25 ° C. of the polishing composition of the present embodiment is preferably 7.0 or more, more preferably 8.0 or more, still more preferably 9.0 or more, and the same viewpoint from the viewpoint of improving the polishing rate. Therefore, 12.0 or less is preferable and 11.5 or less is more preferable. Here, 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.

  In addition, although content of each component demonstrated above is content at the time of use, the polishing liquid composition of this embodiment 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.

  When the polishing liquid composition of the present embodiment is the concentrated liquid, the content of silica particles is preferably 3% by mass or more, more preferably 6% by mass or more, from the viewpoint of reduction in production and transportation costs. % Or more is more preferable, and from the viewpoint of improving storage stability, 20% by mass or less is preferable, 17% by mass or less is more preferable, and 15% by mass or less is more preferable.

  When the polishing composition of the present embodiment is the concentrated liquid, the content of the water-soluble polymer is preferably 500 ppm by mass or more, and 1,000 ppm by mass or more from the viewpoint of manufacturing and transportation cost reduction. More preferably, 1,500 ppm by mass or more is further preferable, and from the viewpoint of improving storage stability, 20,000 ppm by mass or less is preferable, 16,000 ppm by mass or less is more preferable, and 14,000 ppm by mass or less is preferable. Further preferred.

  When the polishing composition of the present embodiment is the concentrated liquid, the content of the quaternary ammonium compound is preferably 60 mass ppm or more, more preferably 600 mass ppm or more from the viewpoint of reduction in production and transportation costs. Preferably, 3,000 mass ppm or more is more preferable, and from the viewpoint of improving storage stability, 60,000 mass ppm or less is preferable, 30,000 mass ppm or less is more preferable, and 20,000 mass ppm or less is more preferable. preferable.

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

  The polishing composition of the present invention can be prepared, for example, by mixing silica particles, a water-soluble polymer, a quaternary ammonium compound, an aqueous medium, and optional components as necessary.

  The use form of the silica particles is preferably a dispersion using an aqueous medium such as water as a dispersion medium. 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 mixing of the silica particles, preferably the dispersion of silica particles, and the aqueous medium is preferably performed in the presence of a water-soluble polymer. Specifically, it is preferable to mix a solution containing a water-soluble polymer and an aqueous medium with an aqueous dispersion of silica particles, and further dilute the mixed liquid with an aqueous medium as necessary.

  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 rough 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 may be used as the diluent.

  The concentrated solution diluted in the dilution step is, for example, 3 to 20% by mass of silica particles, 500 to 20,000 mass ppm of water-soluble polymer, from the viewpoints of production and transportation cost reduction and storage stability improvement. It is preferable to contain 60 to 60,000 mass ppm of the quaternary ammonium compound.

  Hereinafter, the present invention will be described in detail with specific examples, but these are only examples, and the present invention is not limited thereto.

1. Measuring method of various parameters <Average primary particle diameter of silica particles>
The average primary particle diameter (nm) of the silica particles 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 silica particles is subjected to the following [pretreatment], and then about 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 containing silica particles is adjusted to pH 2.5 ± 0.1 with an aqueous nitric acid solution.
(B) The slurry is taken 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 (silica particles) 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 silica particles>
The average secondary particle diameter (nm) of the silica particles is such that the silica particles are added to ion-exchanged water so that the concentration of the silica particles is 0.3% by mass, and then the obtained aqueous solution is disposable sizing cuvette (polystyrene 10 mm). The cell was measured from the bottom to a height of 10 mm and measured using a dynamic light scattering method (device name: Zetasizer Nano ZS, manufactured by Sysmex Corporation).

<Number of silanol groups>
The number of silanol groups in the silica particles was measured by measuring TG-DTA (device name: Thermo plus TG8120 (manufactured by Rigaku Denki Kogyo Co., Ltd.)) by weighing 15 mg of the powder obtained by freeze-drying the slurry-like silica particles. At this time, the temperature was increased from room temperature to 700 ° C. at a rate of 10 ° C./min, and the weight reduction amount from 200 to 700 ° C. was regarded as the weight reduction amount derived from silanol groups. (Mmol / g) was calculated.

<Weight average molecular weight of water-soluble polymer>
The weight average molecular weight of the water-soluble polymer is a value calculated based on a peak in a chromatogram obtained by applying a gel permeation chromatography (GPC) method under the following conditions.
Equipment: HLC-8320 GPC (Tosoh Corporation, integrated inspection device)
Column: GMPWXL + GMPWXL (anion)
Eluent: 200 mmol / L phosphate buffer / CH ₃ CN = 9/1
Flow rate: 0.5mL / min
Column temperature: 40 ° C
Detector: RI Detector Reference material: Monodispersed polyethylene glycol with known molecular weight

2. Details of polishing liquid composition (1) Preparation of polishing liquid composition Silica particles (colloidal silica, average primary particle diameter 60 nm, association degree 1.8, silanol group number 0.336 mmol / g), water-soluble polymer, quaternary An ammonium compound and ion-exchanged water were mixed with stirring to obtain a concentrated liquid (pH 10.0 to 11.0 (25 ° C.)) of the polishing liquid composition. The said concentrate was diluted 60 times with ion-exchange water, and the polishing liquid composition of Examples 1-6 and Comparative Examples 1-6 was obtained. In Comparative Examples 3 and 4, ammonia water was used in place of the quaternary ammonium compound. In the polishing liquid compositions of Examples 1 to 6 and Comparative Examples 1 to 6, the content of silica particles is 0.25% by mass, the content of water-soluble polymer is 50 ppm by mass, The content of the quaternary ammonium compound and the pH at 25 ° C. are as shown in Table 1. In addition, about the concentrated liquid of the polishing liquid composition of Example 5, 6 and the comparative example 6, ammonia water was added and prepared so that pH of 25 degreeC might be 10.0-11.0.

(2) Details of water-soluble polymer Details of the water-soluble polymer shown in Table 1 are as follows.
(A) pHEAA (HEAA homopolymer)
119 g of ion exchange of 102 g of hydroxyethylacrylamide (0.89 mol KJ Chemicals Kojin Co., Ltd., pure content 99.25% by mass, moisture 0.35% by mass, polymerization inhibitor methylhydroquinone 0.10% by mass, APHA hue 30) It melt | dissolved in water and prepared monomer aqueous solution. Separately, 0.32 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride (polymerization initiator, V-50, 1.30 mmol, manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 36 g of ion-exchanged water, and polymerization was started. An aqueous agent solution was prepared. After putting 760 g of ion-exchanged water into a 2 L separable flask equipped with a Dimroth condenser, thermometer, and crescent PTFE stirring blade, the inside of the separable flask was purged with nitrogen. Subsequently, after raising the temperature in a separable flask to 68 degreeC using the oil bath, the monomer aqueous solution and polymerization initiator aqueous solution which were prepared previously were dripped over 3.5 hours, respectively, and superposition | polymerization was performed. After completion of the dropwise addition, the temperature and stirring were maintained for 4 hours to obtain 1000 g of a colorless and transparent 10% by mass polyhydroxyethylacrylamide aqueous solution.

  The prepared pHEAA had a weight average molecular weight (Mw) of 720,000, a number average molecular weight (Mn) of 18,0000, a molecular weight distribution (Mw / Mn) of 4.0, and a residual monomer concentration of 0.1% by mass. It was.

(B) HEC
As hydroxyethyl cellulose (HEC, weight average molecular weight 250,000), SE-400 manufactured by Daicel Finechem Co., Ltd. was used.

3. Polishing Method The following silicon wafer was polished under the following polishing conditions using the obtained polishing composition.
<Silicon wafer>
200mm diameter single crystal silicon wafer <Polishing conditions>
Polishing machine: Single-sided 8-inch polishing machine GRIND-X SPP600s (manufactured by Okamoto)
Polishing load: 100 g / cm ²
Tokiwa rotation speed: 60rpm
Head rotation speed: 100 rpm
Polishing time: 10 min
Polishing liquid composition temperature: 23 ° C.
Polishing liquid composition supply rate 150 mL / min
The silicon wafer polished under the above polishing conditions was washed and dried.

4). Performance evaluation method
<Polishing speed>
The polishing rate was determined from the following formula by measuring the mass before and after polishing.
Polishing rate [nm / min]
= (Mass before polishing [g] -mass after polishing [g]) / polishing time [min] × 13.4 [nm / g]

As shown in Table 1, a quaternary ammonium compound having 10 to 22 carbon atoms in the quaternary ammonium group was used for the preparation of the polishing composition, and the total number of moles of N ⁺ of the quaternary ammonium compound. And a ratio of the total number of moles of silanol groups in the silica particles (NR ⁴⁺ / SiOH) within the range of 0.005 to 2.00 revealed that a high polishing rate was expressed. .

  The polishing composition of the present invention is useful in the production of a semiconductor substrate because it can exhibit a high polishing rate regardless of the particle size and addition amount of silica particles and the type of water-soluble polymer.

Claims (8)

Including silica particles, a quaternary ammonium compound, and a water-soluble polymer,
The quaternary ammonium group of the quaternary ammonium compound has 10 to 22 carbon atoms,
The ratio [b / a] of the total number of moles of N ⁺ of the quaternary ammonium compound (b) and the number of moles of silanol groups of the silica particles (a) in the polishing composition is 0. A polishing composition for a silicon wafer, which is 005 or more and 2.00 or less. The polishing composition for a silicon wafer according to claim 1, wherein the quaternary ammonium compound is a compound represented by the formula (1).

However, the formula (1), R ^1, R ^2, R ³ and R ⁴ are the same or different and each represents a 1 to 18 hydrocarbon group having a carbon number, X ^- represents a counter ion, R ¹ , R ² , R ³ and R ^{4 have} a total carbon number of 10 or more and 22 or less.   The polishing composition for a silicon wafer according to claim 2, wherein the hydrocarbon group is an alkyl group.   The polishing composition for a silicon wafer according to any one of claims 1 to 3, wherein the water-soluble polymer is hydroxyethyl cellulose.   5. The polishing composition for a silicon wafer according to claim 1, wherein the number of silanol groups per 1 g of the silica particles is 0.01 mmol or more and 4.0 mmol or less.   The mass ratio (water-soluble polymer / quaternary ammonium compound) of the quaternary ammonium compound to the water-soluble polymer in the polishing liquid composition is 0.15 or more and 50 or less. The polishing liquid composition for silicon wafers as described in any one of these.   A method for polishing a silicon wafer, comprising a step of polishing the silicon wafer using the polishing composition for a silicon wafer according to any one of claims 1 to 6.   The manufacturing method of a semiconductor substrate including the process of grind | polishing a silicon wafer using the polishing liquid composition for silicon wafers as described in any one of Claim 1 to 6.