JP6678076B2 - Polishing liquid composition for silicon wafer - Google Patents

Description

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

  2. Description of the Related Art In recent years, design rules for semiconductor devices have been miniaturized due to increasing demands for higher recording capacities of semiconductor memories. For this reason, the depth of focus becomes smaller in photolithography performed in the manufacturing process of semiconductor devices, and the demand for defect reduction and smoothness of silicon wafers (bare wafers) is becoming increasingly severe.

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

  The polishing liquid composition used for the finish polishing includes a polishing liquid composition containing silica particles, ammonia and the like for the purpose of achieving both a reduction in surface roughness (Haze) and a reduction in surface defects (LPD). Nitrogen basic compounds, a polishing liquid composition for silicon wafers containing polyglycene or the like as a water-soluble polymer having a ratio of the number of oxygen atoms derived from hydroxyl groups to the number of oxygen atoms derived from polyoxyalkylene of 0.8 to 10 is known. (See Patent Document 1).

  On the other hand, a polishing composition containing a specific polyglycerin derivative, an abrasive, and water is preferably used for polishing a device wafer during wiring formation, and is used as a polishing slurry composition for CMP for the purpose of reducing the number of scratches. A liquid composition is disclosed (see Patent Document 2). A polishing composition for CMP for polishing a low-k dielectric material, comprising a fine particle abrasive, and at least one silicone-free nonionic surfactant containing a hydrophilic portion and a lipophilic portion. Patent Document 3 discloses a composition for CMP, which comprises a non-ionic surfactant containing at least one silicone containing a hydrophilic portion and a lipophilic portion, and an aqueous carrier.

JP 2015-109423 A JP 2009-99819 A JP 2014-27297 A

  However, when a silicon wafer is polished using the polishing composition described in Patent Literature 1, the surface roughness (Haze) may not be sufficiently reduced in some cases.

  Therefore, in the present invention, a polishing liquid composition for a silicon wafer and a semiconductor substrate using the polishing liquid composition for a silicon wafer, which can achieve both a reduction in surface defects (LPD) and a reduction in surface roughness (Haze), can be obtained. A manufacturing method and a polishing method are provided.

The polishing composition for a silicon wafer of the present invention contains the following components A to D.
(Component A) Abrasive grains (Component B) Polyglycerin derivative represented by the following formula 1 (Component C) Nitrogen-containing basic compound (Component D) Aqueous medium R ¹ O (C ₃ H ₆ O ₂ ) _n H (1 )
However, in Formula 1, R ¹ is at least one selected from a hydrocarbon group having 3 to 22 carbon atoms and an acyl group having 3 to 22 carbon atoms, and n represents an average degree of polymerization of glycerin units and 13 or more. 100 or less.

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

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

  ADVANTAGE OF THE INVENTION According to this invention, the polishing liquid composition for silicon wafers and the semiconductor using the polishing liquid composition for silicon wafers, which make it possible to achieve both a reduction in surface defects (LPD) and a reduction in surface roughness (Haze). A method for manufacturing a substrate and a method for polishing can be provided.

  In the present invention, the polishing liquid composition for silicon wafers (hereinafter, may be abbreviated as “polishing liquid composition”) contains a specific polyglycerin derivative, whereby the silicon wafer polished with the polishing liquid composition can be used. It is based on the knowledge that both surface defects (LPD) and surface roughness (Haze) can be reduced at the surface.

  When a silicon wafer is polished using the polishing composition of the present invention, the details of the mechanism of the effect of the present invention that both the reduction of surface defects (LPD) and the reduction of surface roughness (Haze) can be achieved are clear. However, it is estimated as follows.

  The specific polyglycerin derivative (component B) contained in the polishing composition is selected from a hydrocarbon group having 3 to 22 carbon atoms and an acyl group having 3 to 22 carbon atoms, which have a hydrophobic interaction with the silicon wafer. Or more. Therefore, the polyglycerin derivative (component B) is adsorbed on the silicon wafer surface and suppresses corrosion of the silicon wafer surface by the nitrogen-containing basic compound, that is, an increase in surface roughness (Haze). Further, the polyglycerin derivative (component B) contains a glycerin unit containing a hydroxyl group that renders the surface of the silicon wafer hydrophilic by interaction with the silicon wafer, and the average degree of polymerization of the glycerin unit is 13 or more and 100 or less. Therefore, even if the polyglycerin derivative (component B) contains at least one selected from a hydrocarbon group and an acyl group, which are hydrophobic groups, high wettability can be ensured on the silicon wafer surface. Can be performed uniformly.

  As described above, when the polishing composition of the present invention is used for polishing the surface of a silicon wafer, corrosion inhibition by at least one selected from a hydrocarbon group having 3 to 22 carbon atoms and an acyl group having 3 to 22 carbon atoms is provided. Since it is possible to achieve both the effect and the high wettability by the polyglycerin group having an average degree of polymerization of the glycerin unit of 13 or more and 100 or less, it is estimated that the reduction of the surface roughness (Haze) is realized.

  Since the specific polyglycerin derivative (component B) is adsorbed on the surface of the silicon wafer to improve the wettability of the surface of the silicon wafer, adhesion of particles to the surface of the silicon wafer caused by drying of the surface of the silicon wafer is suppressed. It can be considered. Therefore, if the surface of a silicon wafer is polished using the polishing composition of the present invention, the surface roughness (hereinafter, also simply referred to as “Haze”) and the surface defect (hereinafter, also simply referred to as “LPD”) are reduced. It is presumed that both of the above can be performed well.

[Abrasives (component A)]
As the abrasive grains in the present invention, known abrasive grains that can be used in the polishing liquid composition for silicon wafers can be used, but silica particles are preferred from the viewpoint of reducing Haze and LPD. Specific examples of the silica particles include colloidal silica and fumed silica, and colloidal silica is more preferable from the viewpoint of improving the surface smoothness of the silicon wafer.

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

  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, even more preferably 30 nm or more, from the viewpoint of securing the polishing rate, and the reduction of Haze and LPD From the viewpoint of both reduction and securing of the polishing rate, the thickness is preferably 50 nm or less, more preferably 45 nm or less, and still more preferably 40 nm or less.

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. The specific surface area can be measured, for example, by the method described in Examples.

  The degree of association of the silica particles is preferably 3.0 or less, more preferably 1.1 to 3.0, and more preferably 1.8 to 2.0, from the viewpoint of achieving a reduction in Haze and a reduction in LPD, and securing a polishing rate. 5 is still more preferred, and 2.0 to 2.3 is even more preferred. The shape of the silica particles is preferably a so-called spherical shape and a so-called mayu type.

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

  The average secondary particle diameter of the silica particles is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 35 nm or more, still more preferably 45 nm or more, from the viewpoint of securing the polishing rate, and the reduction of Haze and LPD From the viewpoint of achieving a balance between reduction of the polishing rate and securing the polishing rate, the thickness is preferably 150 nm or less, more preferably 100 nm or less, and still more preferably 80 nm or less.

  As a method for adjusting the degree of association of silica particles, for example, JP-A-6-254383, JP-A-11-214338, JP-A-11-60232, JP-A-2005-060217, JP-A-2005-060219 The method described in Japanese Unexamined Patent Publication (Kokai) No. H10-208 can be adopted.

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 0.07% by mass or more in terms of SiO ₂ , from the viewpoint of securing the polishing rate of the silicon wafer. Preferably, it is more preferably 0.10% by mass or more, and from the viewpoint of reducing the haze and the LPD, preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and 0.2% by mass. % Is more preferable.

[Polyglycerin derivative (component B)]
The polishing composition of the present invention contains a polyglycerin derivative represented by the following formula 1 from the viewpoint of reducing the haze.
R ¹ O (C ₃ H ₆ O ₂ ) _n H (1)
The polyglycerin derivative (component B) contained in the polishing composition of the present invention is a mixture of two or more polyglycerin derivatives selected from the polyglycerin derivatives represented by the above formula 1 at an arbitrary ratio. Is also good.

In the above formula 1, R ¹ is at least one selected from a hydrocarbon group having 3 to 22 carbon atoms and an acyl group having 3 to 22 carbon atoms from the viewpoint of improving the corrosion inhibitory effect. From the viewpoint of storage stability of the composition, a hydrocarbon group is preferred. Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a phenyl group, and an alkylphenyl group. The hydrocarbon group is preferably an alkyl group, preferably a straight-chain alkyl group or a branched-chain alkyl group, and more preferably a straight-chain alkyl group, from the viewpoint of improving the corrosion inhibiting effect. Examples of the acyl group include an alkanoyl group, an alkenoyl group, and an (alkyl) benzoyl group. From the viewpoint of improving the corrosion inhibiting effect, an alkanoyl group is preferable, and a carbonyl group is more preferably bonded to a linear alkyl group. Is a linear alkanoyl group having

The carbon number of R ¹ is 3 or more, more preferably 5 or more, still more preferably 7 or more, still more preferably 10 or more, still more preferably 12 or more, from the viewpoint of improving the corrosion inhibiting effect, and foaming suppression. In light of the above, it is 22 or less, preferably 20 or less, more preferably 18 or less, still more preferably 16 or less, even more preferably 14 or less, and even more preferably 12.

In the general formula 1, the glycerin unit (C ₃ H ₆ O ₂ ) may be any of the structures represented by the following formulas (2) and (3), and the polyglycerin derivative (component B) A mixture of a polyglycerin derivative containing a glycerin unit represented by the following formula (2) and a polyglycerin derivative containing a glycerin unit represented by the following formula (3) may be used.
—CH ₂ —CHOH—CH ₂ O— (2)
—CH (CH ₂ OH) CH ₂ O— (3)

  In the general formula 1, n represents an average degree of polymerization of glycerin units. n is 13 or more, preferably 15 or more, more preferably 17 or more, and still more preferably 18 or more, from the viewpoint of improving wettability, and is 100 or less, and 60 or less from the viewpoint of improving the corrosion inhibition effect. Is preferably 45 or less, more preferably 25 or less.

For the polyglycerin derivative (component B), the value obtained by dividing the average degree of polymerization n of glycerin units by the number of carbon atoms of R ¹ ([average degree of polymerization n] / [number of carbon atoms of R ¹ ]) is from the viewpoint of improving wettability. From the viewpoint of 1.0 or more, more preferably 1.2 or more, more preferably 1.5 or more, and from the viewpoint of improving the corrosion inhibition effect, it is preferably 4.0 or less, more preferably 2.0 or less, 1.8 or less is more preferable.

  The polyglycerin derivative (component B) contained in the polishing composition of the present invention is preferably polyglycerin alkyl ether, polyglycerin alkenyl ether, polyglycerin phenyl ether, polyglycerin alkylphenyl ether, and polyglycerin from the viewpoint of reducing the haze. At least one selected from the group consisting of alkyl esters, polyglycerin alkenyl esters, polyglycerin phenyl esters, and polyglycerin alkylphenyl esters is preferable, and polyglycerin alkyl ethers, polyglycerin alkenyl ethers, polyglycerin phenyl ethers, and polyglycerin alkylphenyl ethers are preferred. At least one selected from the group consisting of is more preferred, and polyglycerin alkyl ether is even more preferred.

  The polyglycerin derivative (component B) contained in the polishing composition of the present invention can be produced, for example, by the production methods (1) and (2) described in JP-A-2009-99819.

(1) A method of adding 2,3-epoxy-1-propanol to an aliphatic alcohol corresponding to R ¹ under an alkali catalyst such as sodium hydroxide. (2) Starting from polyglycerin, a carboxylic acid halide, an acid Examples include a method of condensing a halide, a reactive derivative of a carboxylic acid such as an acid anhydride, and an alkyl halide.

  The content of the polyglycerin derivative (component B) contained in the polishing composition of the present invention is preferably 40 mass ppm or more, more preferably 80 mass ppm or more, further preferably 200 mass ppm or more, from the viewpoint of reducing Haze. Preferably, 300 mass ppm or more is still more preferable, and from the same viewpoint, 5000 mass ppm or less is preferable, 4000 mass ppm or less is more preferable, 3000 mass ppm or less is still more preferable, and 2500 mass ppm or less is even more preferable.

  The ratio of the content of the abrasive grains (component A) to the content of the polyglycerin derivative (component B) (% by mass of component A /% by mass of component B) contained in the polishing composition of the present invention improves the polishing rate. In view of the above, 0.5 or more is preferable, 1 or more is more preferable, 2 or more is more preferable, and 38 or less is preferable, 30 or less is more preferable, and 25 or less is preferable from the viewpoint of reducing the haze and the LPD. The following is further preferable, and 20 or less is still more preferable.

[Nitrogen-containing basic compound (component C)]
The polishing composition of the present invention contains a nitrogen-containing basic compound from the viewpoint of improving the storage stability of the polishing composition, securing the polishing rate, and reducing both Haze and LPD. From the viewpoint, it preferably contains at least one or more nitrogen-containing basic compounds selected from ammonia, amine compounds and ammonium compounds.

  Examples of the nitrogen-containing basic compound include ammonia, ammonium hydroxide, ammonium carbonate, ammonium hydrogen carbonate, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, and N-methyl. Ethanolamine, N-methyl-N, N-diethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N, N-dibutylethanolamine, N- (β-aminoethyl) ethanolamine , Monoisopropanolamine, diisopropanolamine, triisopropanolamine, ethylenediamine, hexamethylenediamine, piperazine hexahydrate, anhydrous piperazine, 1- (2-aminoethyl) Perazine, N- methylpiperazine, diethylenetriamine, and tetramethylammonium and the like hydroxide. These nitrogen-containing basic compounds may be used as a mixture of two or more kinds. As the nitrogen-containing basic compound, ammonia is more preferable from the viewpoint of reducing the haze and the LPD, improving the storage stability of the polishing composition, and securing the polishing rate.

  The content of the nitrogen-containing basic compound contained in the polishing composition of the present invention is adjusted to reduce the haze and the LPD, to improve the storage stability of the polishing composition, and to ensure the polishing rate. In light of the above, 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, 0.007% by mass or more is further preferable, and 0.009% by mass or more is used. Is still more preferable, and from the viewpoint of achieving a reduction in Haze and a reduction in LPD, the amount is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, still more preferably 0.025% by mass or less. 0.018% by mass or less is even more preferred, and 0.014% by mass or less is even more preferred.

[Aqueous medium (component D)]
Examples of the aqueous medium (component D) contained in the polishing composition of the present invention include water such as ion-exchanged water and ultrapure water, or a mixed medium of water and a solvent. Possible solvents (eg, alcohols such as ethanol) are preferred. As the aqueous medium, ion exchange water or ultrapure water is more preferable, and ultrapure water is more preferable. When the aqueous medium (component D) is a mixed medium of water and a solvent, the proportion of water to the whole mixed medium as component D is preferably 95% by mass or more, and more preferably 98% by mass or more from the viewpoint of economy. Preferably, substantially 100% by mass is more preferred.

  The content of the aqueous medium in the polishing composition of the present invention is preferably the balance of components A to C and optional components described below.

[Optional components (auxiliaries)]
The polishing liquid composition of the present invention further includes a water-soluble polymer compound (component E) other than the polyglycerin derivative (component B), a pH adjuster, a preservative, and an alcohol as long as the effects of the present invention are not impaired. , A chelating agent, an anionic surfactant, and at least one optional component selected from nonionic surfactants other than the component B.

[Water-soluble polymer compound (component E)]
The polishing composition of the present invention may contain a water-soluble polymer compound (component E) other than the polyglycerin derivative (component B) from the viewpoint of achieving both a reduction in Haze and a reduction in LPD. 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 10% from the viewpoint of securing a polishing rate and reducing LPD. It is preferably at least 5,000, more preferably at least 50,000.

  Examples of the monomer that is a source constituting the component E include a monomer having a water-soluble group such as an amide group, a hydroxyl group, a carboxyl group, a carboxylic acid ester group, and a sulfonic acid group. Examples of such a water-soluble polymer compound (component E) include polyamide, poly (N-acylalkylenimine), a cellulose derivative, polyvinyl alcohol, and polyethylene oxide. Examples of the polyamide include polyvinylpyrrolidone, polyacrylamide, polyoxazoline, polydimethylacrylamide, polydiethylacrylamide, polyisopropylacrylamide, polyhydroxyethylacrylamide, and the like. Examples of poly (N-acylalkylenimine) include poly (N-acetylethyleneimine), poly (N-propionylethyleneimine), poly (N-caproylethyleneimine), poly (N-benzoylethyleneimine), and poly (N-benzoylethyleneimine). N-nonadezoylethyleneimine), poly (N-acetylpropyleneimine), poly (N-butionylethyleneimine) and the like. Examples of the cellulose derivative include carboxymethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, hydroxyethylethylcellulose, and carboxymethylethylcellulose. These water-soluble polymer compounds may be used as a mixture of two or more at any ratio.

[pH adjuster]
Examples of the pH adjuster include an acidic compound. 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, and hypochlorite. Acid salts and the like.

[Alcohols]
Examples of alcohols include methanol, ethanol, propanol, butanol, isopropyl alcohol, 2-methyl-2-propanool, ethylene glycol, propylene glycol, polyethylene glycol, glycerin and the like. The content of alcohols in the polishing composition of the present invention is preferably 0.1% by mass to 5% by mass.

[Chelating agent]
Examples of chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, triethylenetetraminehexaacetic acid, and triethylenetetramine. And sodium hexaacetate. The content of the chelating agent in the polishing composition of the present invention is preferably 0.01 to 1% by mass.

[Anionic surfactant]
Examples of the anionic surfactant include fatty acid soap, carboxylate such as alkyl ether carboxylate, sulfonate such as alkyl benzene sulfonate and alkyl naphthalene sulfonate, higher alcohol sulfate, alkyl ether sulfate And phosphate salts such as alkyl phosphate esters.

[Nonionic surfactant]
Examples of the nonionic surfactant other than the component B include polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbite fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkyl ether, and polyoxyethylene alkylphenyl. Examples include polyethylene glycol type such as ether and polyoxyalkylene (hardened) castor oil, and polyhydric alcohol type such as sucrose fatty acid ester and alkyl glycoside, and fatty acid alkanolamide.

  The pH at 25 ° C. of the polishing composition of the present invention 0 is preferably 8.0 or more, more preferably 9.0 or more, still more preferably 9.5 or more, from the viewpoint of securing the polishing rate. In light of the above, 12.0 or less is preferable, 11.5 or less is more preferable, and 11.0 or less is further preferable. Adjustment of pH can be performed by adding a nitrogen-containing basic compound (component C) and / or a pH adjuster as needed. Here, the pH at 25 ° C. can be measured using a pH meter (Toa Denpa Kogyo KK, HM-30G), and is a numerical value one minute after immersion of the electrode in the polishing composition.

  Although the content of each component described above is the content at the time of use, the polishing composition of the present invention may be stored and supplied in a concentrated state as long as its storage stability is not impaired. Good. This case is preferable in that the production and transportation costs can be further reduced. The concentrate may be appropriately diluted and used with the above-described aqueous medium as needed. The concentration ratio is not particularly limited as long as the concentration at the time of polishing after dilution can be secured, but is preferably 2 or more, more preferably 10 or more, from the viewpoint of further reducing the production and transportation costs. It is more preferably at least 30 times, even more preferably at least 30 times.

When the polishing composition of the present invention is the above-mentioned concentrated solution, the content of the abrasive grains (component A) in the concentrated solution is preferably 1% by mass or more in terms of SiO ₂ , from the viewpoint of reducing the production and transportation costs. , Preferably at least 2% by mass, more preferably at least 4% by mass, and from the viewpoint of improving storage stability, preferably at most 40% by mass, more preferably at most 35% by mass, still more preferably at most 30% by mass. , 25% by mass or less, even more preferably 20% by mass or less.

  When the polishing composition of the present invention is the above-mentioned concentrated liquid, the content of the polyglycerin derivative (component B) in the concentrated liquid is preferably 0.1% by mass or more from the viewpoint of reducing production and transportation costs, 0.3% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.7% by mass or more, even more preferably 1.0% by mass or more, and a viewpoint of improving storage stability. Therefore, it is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 7% by mass or less, and still more preferably 5% by mass or less.

  When the polishing composition of the present invention is the above-mentioned concentrated solution, the content of the nitrogen-containing basic compound (component C) in the concentrated solution is preferably 0.02% by mass or more from the viewpoint of reducing production and transportation costs. , 0.05% by mass or more, more preferably 0.1% by mass or more, and from the viewpoint of improving storage stability, 5% by mass or less, preferably 3% by mass or less, more preferably 2% by mass. The following are more preferred.

  When the polishing composition of the present invention is the above-mentioned concentrated solution, the pH at 25 ° C. of the concentrated solution is preferably 8.0 or more, more preferably 9.0 or more, and even more preferably 9.5 or more, and , Preferably 12.0 or less, more preferably 11.5 or less, still more preferably 11.0 or less.

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

  The polishing composition of the present invention comprises, for example, an abrasive (component A), a polyglycerin derivative (component B), a nitrogen-containing basic compound (component C), an aqueous medium (component D), and And by mixing with an optional component.

  As a usage form of the abrasive grains, a dispersion using an aqueous medium such as water as a dispersion medium is preferable. The dispersion of the abrasive grains in the aqueous medium can be performed using, for example, a stirrer such as a homomixer, a homogenizer, an ultrasonic disperser, a wet ball mill, or a bead mill. When coarse particles generated by agglomeration of abrasive grains or the like are contained in the aqueous medium, it is preferable to remove the coarse particles by centrifugation, filtration using a filter, or the like. The mixing of the abrasive particles, preferably a dispersion of the abrasive particles, and the aqueous medium is preferably performed in the presence of a polyglycerin derivative (component B). Specifically, a solution containing a polyglycerin derivative (component B) and an aqueous medium (component D) is mixed with abrasive grains, preferably a dispersion of abrasive grains, and if necessary, the mixed liquid is mixed with an aqueous medium. It is preferable to dilute with a medium (component D).

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

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

  In the method of manufacturing a semiconductor substrate and the method of polishing a silicon wafer, a diluting step of diluting the polishing composition (concentrated liquid) of the present invention may be included before the polishing step of polishing the silicon wafer. An aqueous medium (component D) may be used as the diluting medium.

  The concentrated solution diluted in the dilution step may be, for example, 1 to 40% by mass of the component A, 0.1 to 20% by mass of the component B, and 0.1 to 20% by mass of the component C from the viewpoints of reducing production and transportation costs and improving storage stability. Is preferably contained in an amount of 0.02 to 5% by mass.

<Average primary particle diameter of abrasive grains (silica particles)>
The average primary particle diameter (nm) of the abrasive grains 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

  After performing the following [pretreatment], the specific surface area of the abrasive grains is measured in a measuring cell to about 0.1 g to four decimal places, and immediately before the measurement of the specific surface area, in an atmosphere of 110 ° C. for 30 minutes. After drying, it was measured by a nitrogen adsorption method (BET method) using a specific surface area measuring device (Micromeritics automatic specific surface area measuring device Flowsorb III2305, 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) The slurry-like abrasive grains adjusted to pH 2.5 ± 0.1 are 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 crushed sample is suspended in ion-exchanged water at 40 ° C. and filtered with a membrane filter having a pore size of 1 μm.
(E) Wash the filtrate on the filter 5 times with 20 g of ion-exchanged water (40 ° C.).
(F) The filter to which the filtrate has adhered is placed in a petri dish and dried in an atmosphere at 110 ° C. for 4 hours.
(G) The dried filtrate (abrasive grains) was taken so as not to be mixed with filter debris, and finely ground in a mortar to obtain a measurement sample.

<Average secondary particle diameter of abrasive grains (silica particles)>
The average secondary particle diameter (nm) of the abrasive grains is determined by adding the abrasive grains to ion-exchanged water such that the concentration of the abrasive grains becomes 0.25% by mass, and then dissolving the resulting aqueous solution in a Disposable Sizing Cuvette (polystyrene 10 mm). The cell was placed up to a height of 10 mm from the lower bottom and measured using a dynamic light scattering method (apparatus name: Zetasizer Nano ZS, manufactured by Sysmex Corporation).

(1) Preparation of Polishing Composition Silica particles (colloidal silica, average primary particle diameter 35 nm, average secondary particle diameter 70 nm, degree of association 2.0), polyglycerin derivatives described in Table 1, 28% by mass aqueous ammonia ( Kishida Chemical Co., Ltd. reagent special grade) and ion-exchanged water were stirred and mixed, and the polishing composition of Examples 1 to 9 and Comparative Examples 1 to 3 (all concentrated solutions, pH 10.6 ± 0.1) (25 ° C.)). The content of silica particles was 0.17% by mass in terms of SiO ₂ , the content of polyglycerin derivative was as shown in Table 1, and the concentration of ammonia was 0.01% by mass. . However, these concentrations are all values for the polishing composition obtained by diluting the concentrated solution 40-fold. The balance excluding silica particles, polyglycerin derivative, and ammonia is ion-exchanged water.

(2) Polishing method A polishing liquid composition (pH 10.6 ± 0.1 (25 ° C.)) obtained by diluting the polishing liquid composition (concentrated liquid) 40 times with ion-exchanged water was subjected to a filter (compact) immediately before polishing. Filtration was performed using a cartridge filter (MCP-LX-C10S Advantech Co., Ltd.), and the following silicon wafer (silicon single-sided mirror wafer with a diameter of 200 mm (conduction type: P, crystal orientation: 100, resistivity 0.1 Ω) under the following polishing conditions: · Cm or more and less than 100Ω · cm)). Prior to the final polishing, the silicon wafer was preliminarily subjected to rough polishing using a commercially available polishing composition. The surface roughness (Haze) of the silicon wafer that had been subjected to the rough polishing and subjected to the final polishing was 2.680 ppm (DWO) and 6.330 ppm (DNN). The measured value of the haze is obtained by the same method as the later-described evaluation of the surface roughness (haze) of the silicon wafer surface after cleaning.

<Finish polishing conditions>
Polishing machine: Single-sided 8-inch polishing machine GRIND-X SPP600s (manufactured by Okamoto Corporation)
Polishing pad: Suede pad (Toray Cortex Co., Ltd. Asker hardness 64 Thickness 1.37mm Nap length 450um Opening diameter 60um)
Silicon wafer polishing pressure: 100 g / cm ²
Platen rotation speed: 60 rpm
Polishing time: 5 minutes Supply rate of polishing composition: 150 g / cm ²
Temperature of polishing composition: 23 ° C
Carrier rotation speed: 60 rpm

  After the final polishing, the silicon wafer was subjected to ozone cleaning and dilute hydrofluoric acid cleaning as follows. In the ozone cleaning, an aqueous solution containing 20 ppm of ozone was sprayed from a nozzle at a flow rate of 1 L / min toward the center of a silicon wafer rotating at 600 rpm for 3 minutes. At this time, the temperature of the ozone water was normal temperature. Next, dilute hydrofluoric acid cleaning was performed. In dilute hydrofluoric acid cleaning, an aqueous solution containing 0.5% by mass of ammonium hydrogen fluoride (special grade: Nacalai Tex Corporation) is sprayed from a nozzle at a flow rate of 1 L / min toward the center of a silicon wafer rotating at 600 rpm for 6 seconds. did. The ozone cleaning and the diluted hydrofluoric acid cleaning were performed as one set, and a total of two sets were performed. In the spin drying, the silicon wafer was rotated at 1500 rpm.

<Evaluation of surface roughness (Haze) and surface defect (LPD) of silicon wafer>
To evaluate the surface roughness (Haze) of the silicon wafer surface after cleaning, a dark field wide oblique incidence channel (DWO) measured using a surface roughness measuring device “Surfscan SP1-DLS” (manufactured by KLA Tencor) is used. ) And the value in the dark field narrow normal incidence channel (DNN). As the evaluation of the surface roughness, both Haze (DWO) and Haze (DNN) were measured. Haze (DWO) is effective for measuring the surface roughness of a relatively short wavelength, and Haze (DNN) is Suitable for measuring relatively long wavelength surface roughness. Therefore, the surface roughness of the silicon wafer can be evaluated widely by measuring in two modes. The surface defect (LPD) was measured simultaneously with the haze measurement, and evaluated by measuring the number of particles having a particle size of 45 nm or more on the silicon wafer surface. The evaluation result of the surface defect (LPD) indicates that the smaller the numerical value, the smaller the surface defect. Also, the smaller the value of Haze (DWO) and Haze (DNN), the higher the surface smoothness. The measurement of the surface roughness (Haze) and the surface defect (LPD) was performed on each of two silicon wafers, and the respective average values are shown in Table 1.

  The values of “DWO (ppm)”, “DNN (ppm)”, and “LPD (piece)” described in Table 1 were obtained by storing the concentrate in a state of 20 ° C. for 14 days, and then diluting it 40-fold. The value of "DNN (ppm) after storage" is a value in the case of polishing using a polishing liquid composition, and the value of "DNN (ppm) after storage" was obtained by storing at 40 ° C. for 14 days in the form of a concentrated solution, and then diluting 40-fold This is a value when polishing is performed using a polishing liquid composition.

<Evaluation of wettability>
The area of the hydrophilized portion (wet portion) of the mirror surface of the silicon wafer (200 mm in diameter) immediately after the finish polishing was visually observed, and the results are shown in Table 1.

<Evaluation of corrosion amount>
The silicon wafer cut into a square of 40 × 40 mm was immersed in a 1% by mass dilute hydrofluoric acid aqueous solution for 2 minutes to remove an oxide film, then rinsed by immersing it in ion exchanged water for 1 second, and air blow dried. Next, the silicon wafer was placed in a plastic container, and 20 g of the polishing composition was added to the plastic container and the plastic container was capped. The silicon wafer was immersed in the polishing composition at 40 ° C. for 24 hours, then immediately immersed in ion-exchanged water, rinsed, and air blow dried. The amount of weight loss before and after immersion of the air blow dried silicon wafer in the polishing composition was defined as the amount of corrosion.

  As shown in Table 1, the use of the polishing composition of Examples 1 to 9 reduces the surface roughness (Haze) compared to the case of using the polishing composition of Comparative Examples 1 to 3. Surface defects (LPD) were successfully reduced.

  The use of the polishing composition of the present invention makes it possible to reduce both surface defects (LPD) and surface roughness (Haze) in polishing a silicon wafer. Therefore, the polishing composition of the present invention is useful as a polishing composition used in various semiconductor substrate manufacturing processes, and is particularly useful as a polishing composition for final polishing of a silicon wafer.

Claims (6)

A polishing composition for silicon wafers, comprising abrasive grains, a polyglycerin derivative represented by the following formula 1, a nitrogen-containing basic compound, and an aqueous medium.
R ¹ O (C ₃ H ₆ O ₂ ) _n H (1)
Here, in the formula 1, R ¹ is a hydrocarbon group having 3 to 22 carbon atoms , and n represents an average degree of polymerization of glycerin units and is 13 to 100. 2. The silicon wafer according to claim 1, wherein a value obtained by dividing the average degree of polymerization n by the number of carbon atoms of the R ¹ ([average degree of polymerization n] / [number of carbon atoms of R ¹ ]) is 1.0 or more. 3. Polishing liquid composition.   The polishing composition according to claim 1, wherein the abrasive is colloidal silica.   4. The polishing composition for silicon wafers according to claim 1, wherein the content of the abrasive grains is 0.01% by mass or more and 0.5% by mass or less. 5.   A polishing method, comprising: polishing a silicon wafer using the polishing liquid composition for a silicon wafer according to any one of claims 1 to 4.   A method for producing a semiconductor substrate, comprising a step of polishing a silicon wafer using the polishing composition for a silicon wafer according to claim 1.