JP2013138153A - Polishing liquid composition for silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid composition for a silicon wafer, allowing reduction in the number of particles remaining on the surface of a silicon wafer.SOLUTION: A polishing liquid composition for a silicon wafer contains a silica particle (component A); a water-soluble alkali compound (component B); at least one kind of compound (component C) selected from the group consisting of alkyl sulfonates having a carbon number of 1 to 4 and alkyl sulfates having a carbon number of 1 to 4; a cationized polyvinyl alcohol (component D); and an aqueous medium (component E), where the component D comprises a constitutional unit (d1) represented by -CH-CH(OH)-, a constitutional unit (d2) represented by -CH-CH(OCOR)- and a constitutional unit (d3) represented by -X-, the mol concentration of the constitutional unit (d3) is 0.001 to 1.5 mol% in all constitutional units of the component D, the content of the component C is 0.0300 wt.% or less, and the pH at 25°C is 8 to 12.

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.

  As a polishing composition used for polishing a silicon wafer (bare wafer) used for manufacturing a semiconductor substrate, a polishing composition containing silica particles is known. In this type of polishing composition, storage stability of the concentrate, wettability of the surface of the silicon wafer, filter clogging when the polishing composition is filtered to remove aggregates, polishing speed, etc. are problems. (See, for example, Patent Document 1).

  On the other hand, as a polishing liquid for a silicon wafer containing an anionic surfactant, a polishing liquid composition is disclosed which has a problem of reducing the surface roughness of the silicon wafer (see, for example, Patent Document 2). Moreover, as a polishing liquid for precision parts containing an alkylsulfonic acid having 1 to 4 carbon atoms or a salt thereof, a polishing liquid composition is disclosed in which reduction of the surface roughness of the object to be polished is a solution (for example, (See Patent Document 3).

JP 2011-171689 A JP 2005-268665 A JP 2000-109818 A

  In recent years, the miniaturization of design rules for semiconductor devices has progressed, and the surface quality required for silicon wafers, such as reducing the number of particles, has been increasing. The particles are foreign matters such as abrasives, polishing pad scraps, silicon chips, and the like attached to the wafer surface. The smaller the number of particles, the higher the surface cleanliness.

  The present invention provides a polishing composition for a silicon wafer capable of obtaining a silicon wafer with a small number of particles remaining on the surface, a method for producing a semiconductor substrate using the polishing composition, and a method for polishing a silicon wafer. To do.

ただし、式（２）中、Ｒ¹は炭素数１〜３のアルキル基であり、式（３）中、Ｘは分子中にカチオン基を有し且つビニルアルコール低級脂肪酸エステルと共重合可能な不飽和化合物に由来する構成単位である。 The polishing composition for a silicon wafer of the present invention is
Silica particles (component A);
A water-soluble alkali compound (component B);
At least one compound (component C) selected from the group consisting of alkyl sulfonates having 1 to 4 carbon atoms and alkyl sulfates having 1 to 4 carbon atoms;
Cationized polyvinyl alcohol (component D);
An aqueous medium (component E),
The component D includes a structural unit (d1) represented by the following general formula (1), a structural unit (d2) represented by the following general formula (2), and a structural unit represented by the following general formula (3). (D3), the molar concentration of the structural unit (d3) is 0.001 to 1.5 mol% in all the structural units of the component D,
The content of component C is 0.0300% by weight or less,
The pH at 25 ° C. is 8-12.

In the formula (2), R ¹ is an alkyl group having 1 to 3 carbon atoms, and in the formula (3), X has a cationic group in the molecule and can be copolymerized with a vinyl alcohol lower fatty acid ester. A structural unit derived from a saturated compound.

  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.

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

  According to the present invention, it is possible to provide a polishing composition for a silicon wafer that can reduce the number of particles remaining on the surface of the silicon wafer, a method for manufacturing a semiconductor substrate using the polishing composition, and a polishing method for a silicon wafer.

  The present invention is selected from the group consisting of silica particles (component A), a water-soluble alkali compound (component B), an alkyl sulfonate having 1 to 4 carbon atoms, and an alkyl sulfate having 1 to 4 carbon atoms. A structural unit (d1) comprising at least one compound (component C), cationized polyvinyl alcohol (component D), and an aqueous medium (component E), wherein component D is represented by the following general formula (1) ), The structural unit (d2) represented by the following general formula (2), and the structural unit (d3) represented by the following general formula (3), and the molar concentration of the structural unit (d3) is all of the component D Polishing of an object to be polished using a polishing composition that is 0.001 to 1.5 mol% in a structural unit, the content of component C is 0.0300 wt% or less, and a pH of 8 to 12 at 25 ° C. By doing this, the number of particles remaining on the surface is small. Based on the finding that it is possible to obtain a Fine.

  Generally, in polishing a silicon wafer (hereinafter sometimes abbreviated as “wafer”), it is known that the silicon wafer and the surface of the silica particles have a strong interaction and are easily adsorbed to each other. In general, the surface of a silicon wafer and the surface of an abrasive such as silica particles are negatively (negatively) charged under alkali. Cationized polyvinyl alcohol adsorbs moderately on the surface of silicon wafers and exhibits good wettability, and at the same time adsorbs on the surface of silica particles to cause appropriate aggregation of silica particles and contributes to improving polishing efficiency. It is done. However, when the interaction between the silicon wafer and the surface of the silica particles cannot be sufficiently eliminated by the addition of cationized polyvinyl alcohol, the number of particles may not be sufficiently reduced. In polishing using the polishing composition for a silicon wafer of the present invention (hereinafter sometimes abbreviated as “polishing composition”), a specific cationized polyvinyl alcohol, a specific sulfonate, and a specific sulfuric acid are used. By coexisting with at least one of the salts, both the specific cationized polyvinyl alcohol and the specific sulfonate and at least one of the specific sulfate are adsorbed on the silicon wafer and the silica particles. As a result, moderate wettability and agglomeration of the silica particles can be obtained, and the surface of the silica particles and the wafer surface are modified so as not to interact easily. This makes it possible to perform efficient polishing, reduce the number of silica particles remaining on the wafer surface, and reduce the number of particles remaining on the wafer surface. The action mechanism of the polishing composition of the present invention is not limited to the above-described estimated action mechanism.

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

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

  From the viewpoint of improving the polishing rate, the average primary particle size of the silica particles contained in the polishing liquid 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 20 nm. It is above, More preferably, it is 30 nm or more. From the viewpoint of reducing the number of particles, it is preferably 50 nm or less, more preferably 45 nm or less, and still more preferably 40 nm or less. Therefore, the average primary particle diameter of the silica particles is preferably 5 to 50 nm, more preferably 10 to 45 nm, still more preferably 15 to 40 nm, and even more preferably 20 to 40 nm, from the viewpoint of reducing the number of particles and improving the polishing rate. Even more preferably, it is 30 to 40 nm.

  In particular, when colloidal silica is used as the abrasive, the average primary particle diameter is preferably 5 to 50 nm, more preferably 10 to 45 nm, and still more preferably 15 to 40 nm, from the viewpoint of reducing the number of particles and improving the polishing rate. Even more preferably, it is 20 to 40 nm, and even more preferably 30 to 40 nm.

  The content of the silica particles in the polishing liquid composition of the present invention is preferably 0.0500 wt% (500 wtppm) or more, more preferably 0.1000 wt% (1000 wtppm) or more from the viewpoint of improving the polishing rate. 0.2000% by weight (2000 ppm by weight) or more is more preferable. Further, from the viewpoint of cost reduction of the polishing composition, it is preferably 0.5000 wt% (5000 wtppm) or less, more preferably 0.4000 wt% (4000 wtppm) or less, and 0.3000 wt% (3000 wt%). ppm) or less is more preferable. Therefore, the content of silica particles is preferably 0.0500 to 0.5000 wt% (500 to 5000 ppm by weight), from the viewpoint of improving the polishing rate and reducing the cost of the polishing composition, and is 0.1000 to 0.00. 4000 weight% (1000-4000 weight ppm) is more preferable, 0.2000-0.3,000 weight% (2000-3000 weightppm) is still more preferable.

  The silica particles that are the abrasive contained in the polishing composition of the present invention are preferably associated to form secondary particles from the viewpoint of reducing the number of particles and improving the polishing rate. The degree of association of the silica particles is preferably 1.1 to 3.0, more preferably 1.3 to 2.8, still more preferably 1.5 to 2.5, from the viewpoint of reducing the number of particles and improving the polishing rate. 1.8 to 2.5 is even more preferred, 1.8 to 2.2 is even more preferred, and 1.8 to 2.0 is even more preferred. The shape of the silica particles is preferably a so-called spherical type and a so-called mayu type, but a so-called mayu type is more preferred. When the silica particles are colloidal silica, the degree of association of the colloidal silica is preferably 1.1 to 3.0, more preferably 1.3 to 2.8, from the viewpoint of reducing the number of particles and improving the polishing rate. 5-2.5 are more preferable, 1.8-2.5 are still more preferable, 1.8-2.2 are still more preferable, and 1.8-2.0 are still more preferable.

The association degree of the silica particles is a coefficient representing the shape of the abrasive and is calculated by the following formula.
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, methods described in JP-A-6-254383 and JP-A-2005-060219 can be employed.

  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.

[Water-soluble alkali compound (component B)]
The polishing liquid composition of the present invention contains a water-soluble alkali compound (component B) from the viewpoint of improving the polishing rate. In the present invention, “water-soluble” of a water-soluble alkali compound means having a solubility of 2 g / 100 ml or more in water, and “water-soluble alkali compound” is alkaline when dissolved in water. The compound which shows this.

  Examples of the water-soluble alkali compound include water-soluble amine compounds, alkali metal or alkaline earth metal hydroxides, carbonates, and hydrogen carbonates. Specifically, the water-soluble amine compound includes ammonia, ammonium hydroxide, ammonium carbonate, ammonium hydrogen carbonate, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, N Monomethylethanolamine, N-methyl-N, N-diethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N, N-dibutylethanolamine, N- (β-aminoethyl) ethanol -Luamine, monoisopropanolamine, diisopropanolamine, and triisopropanolamine, ethylenediamine, hexamethylenediamine, piperazine hexahydrate, anhydrous piperazine, 1- (2-amino Chill) piperazine, N-methylpiperazine, diethylenetriamine, tetramethylammonium hydroxide, and the like. Alkali metal or alkaline earth metal hydroxide, carbonate, and bicarbonate include potassium hydroxide, water, and the like. Examples thereof include sodium oxide, potassium carbonate, potassium hydrogen carbonate, sodium carbonate and sodium hydrogen carbonate. These water-soluble alkali compounds may be used in combination of two or more. The water-soluble alkali compound that can be contained in the polishing composition of the present invention is preferably a water-soluble amine compound, more preferably ammonia or methylamine, and even more preferably ammonia, from the viewpoint of improving the polishing rate.

  The content of the water-soluble alkali compound contained in the polishing composition of the present invention is preferably 0.0010% by weight (10 ppm by weight) or more from the viewpoint of reducing the number of particles and improving the polishing rate, and 0.0030% by weight ( 30 wt ppm) or more, more preferably 0.0050 wt% (50 wt ppm) or more, even more preferably 0.0080 wt% (80 wt ppm) or more, 0.0100 wt% (100 wt ppm) The above is even more preferable. Further, from the viewpoint of preventing corrosion of the silicon wafer, it is preferably 5.000 wt% (50000 wt ppm) or less, more preferably 1.0000 wt% (10000 wt ppm) or less, and 0.1000 wt% (1000 wt ppm). The following is more preferable, 0.0500 wt% (500 wtppm) or less is even more preferable, and 0.0300 wt% (300 wtppm) or less is even more preferable. Therefore, from the viewpoint of reducing the number of particles, improving the polishing rate, and preventing the corrosion of the silicon wafer, the content of the water-soluble alkali compound is preferably 0.0010 to 5.0000% by weight (10 to 50000 ppm by weight). .0030 to 1.000 wt% (30 to 10000 wtppm) is more preferable, 0.0050 to 0.1000 wt% (50 to 1000 wtppm) is more preferable, and 0.0080 to 0.0500 wt% (80 ˜500 wt ppm) is even more preferred, and 0.0100 to 0.0300 wt% (100 to 300 wt ppm) is even more preferred.

[At least one compound selected from the group consisting of an alkyl sulfonate having 1 to 4 carbon atoms and an alkyl sulfate having 1 to 4 carbon atoms (component C)]
The polishing composition of the present invention has an alkyl sulfonate having 1 to 4 carbon atoms (hereinafter sometimes abbreviated as “alkyl sulfonate”) and 1 to 4 carbon atoms from the viewpoint of reducing the number of particles. And at least one compound (component C) selected from the group consisting of alkyl sulfates (hereinafter sometimes abbreviated as “alkyl sulfates”). “Alkyl sulfonate having 1 to 4 carbon atoms” means an alkyl monosulfonate and / or alkyl polysulfonate in which the alkyl group covalently bonded to the sulfur atom has 1 to 4 carbon atoms. The “alkyl sulfate having 1 to 4 carbon atoms” means an alkyl sulfate having 1 to 4 carbon atoms in the alkyl group.

(C1-C4 alkyl sulfonate)
The alkyl sulfonate having 1 to 4 carbon atoms is at least one selected from the group consisting of alkyl monosulfonates and alkyl polysulfonates, but from the viewpoint of reducing the number of particles, Component C contains alkyl polysulfonic acid. It is preferable that a salt is contained, and it is more preferable that the component C consists only of an alkyl polysulfonate. Moreover, although the number of the sulfonic acid groups which a C1-C4 alkyl sulfonate has may be one, two or two or more are preferable from a viewpoint of particle number reduction.

  Specific examples of the alkyl sulfonate having 1 to 4 carbon atoms in the acid state include methanesulfonic acid, hydroxymethanesulfonic acid, isethionic acid, ethanesulfonic acid, ethanedisulfonic acid, propanesulfonic acid, and 1.3-propanedisulfone. Examples include acid, 2-hydroxy-2-propanesulfonic acid, 3-chloro-2-hydroxypropanesulfonic acid, and 1-butanesulfonic acid. Among these, from the viewpoint of reducing the number of particles, at least one selected from the group consisting of methanesulfonic acid, hydroxymethanesulfonic acid, isethionic acid, ethanedisulfonic acid, and 1.3-propanedisulfonic acid is preferable. More preferred is at least one selected from the group consisting of acid, isethionic acid, ethanedisulfonic acid, and 1.3-propanedisulfonic acid, and at least one selected from the group consisting of hydroxymethanesulfonic acid and 1.3-propanedisulfonic acid. Species are more preferred.

  Examples of the salts of these alkyl sulfonic acids include salts of alkyl sulfonic acids and metals, ammonium, alkyl ammonium having 1 to 20 carbon atoms, or alkanolamine having 2 to 12 carbon atoms. The metal, alkylammonium and alkanolamine are not particularly limited as long as they can form a salt with alkylsulfonic acid.

  Specific examples of the metal include metals belonging to groups 1A, 1B, 2A, 2B, 3A, 3B, 7A, and 8 of the periodic table (long period type).

  Specific examples of the alkylammonium include dimethylammonium, trimethylammonium, tetramethylammonium, tetraethylammonium, tetrabutylammonium and the like. Specific examples of the alkanolamine include monoethanolamine, diethanolamine, triethanolamine and the like.

  Among the alkyl sulfonates, sodium salt, aluminum salt, nickel salt, iron salt, cobalt salt, magnesium salt, cerium salt, or ammonium salt are preferable, and sodium salt is more preferable from the viewpoint of reducing the number of particles. On the other hand, ammonium salt is more preferable from the viewpoint of preventing contamination of the silicon wafer with metal.

  Therefore, the alkyl sulfonate having 1 to 4 carbon atoms contained in the polishing liquid composition of the present invention includes sodium methanesulfonate, sodium hydroxymethanesulfonate, sodium isethionate, and ethanedisulfonic acid from the viewpoint of reducing the number of particles. Preferably, at least one selected from the group consisting of sodium, ammonium ethanedisulfonate, and sodium 1.3-propanedisulfonate, sodium hydroxymethanesulfonate, sodium isethionate, sodium ethanedisulfonate, and 1.3-propanedisulfone At least one selected from the group consisting of sodium acid is more preferable, at least one selected from the group consisting of sodium hydroxymethanesulfonate and sodium 1.3-propanedisulfonate is more preferable, .3- propane disulfonic acid sodium is more preferred. These alkyl sulfonates may be used alone or in admixture of two or more.

(C1-C4 alkyl sulfate)
Specific examples of the alkyl sulfate having 1 to 4 carbon atoms in the acid state include methyl sulfate and ethyl sulfate.

  Examples of these salts of alkyl sulfuric acid include salts of alkyl sulfuric acid with metals, ammonium, alkyl ammonium having 1 to 20 carbon atoms, and alkanolamine having 2 to 12 carbon atoms. The metal, alkylammonium, and alkanolamine are not particularly limited as long as they can form a salt with alkylsulfuric acid. Specific examples of the metal, the alkylammonium, and the alkanolamine may be the same as the specific examples capable of forming a salt with the alkylsulfonic acid, respectively.

  The alkyl sulfate having 1 to 4 carbon atoms contained in the polishing composition of the present invention is preferably sodium methyl sulfate or sodium ethyl sulfate from the viewpoint of reducing the number of particles. These alkyl sulfates may be used alone or in admixture of two or more.

  The carbon number of the alkyl group in the alkyl sulfonate and the alkyl sulfate is 1 or more, preferably 2 or more, and more preferably 3 or more from the viewpoint of reducing the number of particles. Moreover, from a viewpoint of foaming suppression of polishing liquid composition, it is 4 or less, and 3 or less is preferable. Therefore, carbon number of the alkyl group is 1 to 4, preferably 2 to 3, and more preferably 3.

  The content of Component C in the polishing composition of the present invention is 0.0300 wt% (300 wt ppm) or less from the viewpoint of preventing foaming, but is preferably 0.0100 (100 wt ppm) or less. 0050 wt% (50 wtppm) or less is more preferred, 0.0020 wt% (20 wtppm) or less is more preferred, and 0.0010 wt% (10 wtppm) or less is even more preferred. On the other hand, the content of Component C is preferably 0.0001 wt% (1 wt ppm) or more, more preferably 0.0003 (3 wt ppm) or more, and 0.0005 wt% (5 wt%) from the viewpoint of reducing the number of particles. Weight ppm) or more, more preferably 0.0006 wt% (6 wt ppm) or more. Therefore, the content of Component C is preferably 0.0001 to 0.0300 wt% (1 to 300 wt ppm), and 0.0003 to 0.0100 wt% (3 to 3 wt%) from the viewpoint of reducing the number of particles and preventing foaming. 100 wt ppm) is more preferable, 0.0005 to 0.0050 wt% (5 to 50 wt ppm) is further preferable, 0.0005 to 0.0020 wt% (5 to 20 wt ppm) is still more preferable, and 0 Even more preferred is .0006 to 0.0010 wt% (6 to 10 wtppm).

  The ratio by weight% (weight ppm) of component C and silica particles (component A) in the polishing composition of the present invention [weight% (weight ppm) of component C / weight% (weight ppm) of component A] is the number of particles. From the viewpoint of reduction, 0.0004 or more is preferable, 0.0010 or more is more preferable, 0.0020 or more is more preferable, 0.0024 or more is even more preferable, 0.1 or less is preferable, 0.05 The following is more preferable, 0.02 or less is further preferable, 0.01 or less is further more preferable, and 0.005 or less is even more preferable. Therefore, from the viewpoint of reducing the number of particles, the weight% (weight ppm) ratio is preferably 0.0004 to 0.1, more preferably 0.0010 to 0.05, and still more preferably 0.0020 to 0.02. 0.0020 to 0.01 is even more preferable, and 0.0024 to 0.005 is even more preferable.

[Cationized polyvinyl alcohol (component D)]
The cationized polyvinyl alcohol (component D) contained in the polishing liquid composition of the present invention has structural units (d1) to (d3) represented by the following general formulas (1) to (3).

In the above formula (2), R ¹ is an alkyl group having 1 to 3 carbon atoms, and in formula (3), X has a cationic group in the molecule and is unsaturated which can be copolymerized with a vinyl alcohol lower fatty acid ester. A structural unit derived from a compound.

The cationized polyvinyl alcohol containing the structural unit (d1), the structural unit (d2), and the structural unit (d3) is a monomer compound that is a supply source of the structural unit (d2) and a supply source of the structural unit (d3). It is obtained by copolymerizing with a certain monomer compound and partially saponifying the obtained copolymer. For example, when R ¹ in the general formula (2) is a methyl group, a copolymer of a polymerizable cationic monomer (a compound that is a supply source of the structural unit (d3)) and vinyl acetate is partially saponified. Thus obtained cationized polyvinyl alcohol can be used as the cationized polyvinyl alcohol.

  Here, the structural unit (d3) contains a cationic group, and the monomer compound that is a supply source of the structural unit (d3) is a vinyl alcohol lower (C 1-3) fatty acid ester (the structural unit (d1), ( It is a compound copolymerizable with the monomer compound) which is the source of d2). Examples of the monomer compound that is a supply source of the structural unit (d3) include compounds selected from compounds represented by the following general formula (4-1) and compounds represented by the following general formula (4-2). It is done. The structural unit (d3) is at least one compound selected from a compound represented by the following general formula (4-1) and a compound represented by the following general formula (4-2) from the viewpoint of reducing the number of particles. It is preferable that it is derived.

In the formula, R ² , R ³ , R ⁴ , R ⁸ , R ⁹ and R ¹⁰ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Y ¹ and Y ² are each independently a group selected from an alkylene group having 1 to 12 carbon atoms, —COOR ¹³ —, —CONHR ¹³ —, —OCOR ¹³ —, and —R ¹⁴ —OCO—R ¹³ —. It is. Here, R <^13> , R <^14> is respectively independently a C1-C5 alkylene group. R ⁵ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a hydroxyalkyl group having 1 to 3 carbon atoms, or R ² R ³ C═C (R ⁴ ) —Y ¹ —. R ⁶ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a hydroxyalkyl group having 1 to 3 carbon atoms, and R ⁷ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a hydroxy group having 1 to 3 carbon atoms. An alkyl group or a benzyl group, Z- represents an anion; R ¹¹ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a hydroxyalkyl group having 1 to 3 carbon atoms, or R ⁸ R ⁹ C═C (R ¹⁰ ) —Y ² —. R ¹² is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a hydroxyalkyl group having 1 to 3 carbon atoms. Z ^- is, for example, a halogen ion.

  Examples of the monomer compound that is a supply source of the structural unit (d3) include diallyldialkyl (the alkyl group has 1 to 3 carbon atoms) ammonium salt, N- (meth) acryloylaminoalkyl (carbon of the alkyl group). The number is 1-5) -N, N-dialkyl (the alkyl group has 1 to 3 carbon atoms) amine, N- (meth) acryloylaminoalkyl (the alkyl group has 1 to 5 carbon atoms) -N, N , N-trialkyl (the alkyl group has 1 to 3 carbon atoms) ammonium salt, N- (meth) acryloyloxyalkyl (the alkyl group has 1 to 5 carbon atoms) -N, N, N-trialkyl ( The alkyl group has 1 to 3 carbon atoms, an ammonium salt, and N- (ω-alkenyl (the alkenyl group has 2 to 10 carbon atoms))-N, N-dialkyl (the alkyl group has 1 to 3 carbon atoms). ) From amine Compounds barrel like.

  The cationized polyvinyl alcohol contained in the polishing liquid composition of the present invention may contain other structural units in addition to the structural units (d1) to (d3) as long as the effects of the present invention are not impaired. It is preferable not to contain, and it is more preferable not to contain.

  The total molar concentration of the structural unit (d1), the structural unit (d2), and the structural unit (d3) among all the structural units of the cationized polyvinyl alcohol is preferably 50 to 100 mol% from the viewpoint of reducing the number of particles. Preferably it is 80-100 mol%, More preferably, it is 90-100 mol%, More preferably, it is substantially 100 mol%, More preferably, it is 100 mol%.

  Further, the molar concentration of the structural unit (d3) containing a cationic group in all the structural units of the cationized polyvinyl alcohol is 0.001 mol% or more, preferably 0.01 mol% from the viewpoint of improving the polishing rate. Above, more preferably 0.05 mol% or more, still more preferably 0.10 mol% or more, and even more preferably 0.20 mol% or more. The molar concentration of the structural unit (d3) containing a cationic group is 1.5 mol% or less, preferably 1 mol% or less, more preferably 0.35 mol% or less, from the viewpoint of reducing the number of particles. More preferably, it is 0.25 mol% or less. Therefore, the molar concentration of the structural unit (d3) containing a cationic group in all the structural units of the cationized polyvinyl alcohol is 0.001 to 1.5 mol% from the viewpoint of reducing the number of particles and improving the polishing rate. Preferably 0.01 to 1 mol%, more preferably 0.05 to 1 mol%, still more preferably 0.10 to 0.35 mol%, even more preferably 0.20 to 0.35 mol%, even more Preferably it is 0.20-0.25 mol%. Here, the molar concentration of the structural unit (d3) containing the cationic group can be measured by the [Method for measuring cationization modification rate] described in Examples.

  In the cationized polyvinyl alcohol, the molar ratio (d1) / (d2) of the structural unit (d1) and the structural unit (d2) is preferably 1 to 300, more preferably 2 from the viewpoint of improving solubility and reducing the number of particles. -50, more preferably 2.5-20, even more preferably 3.0-15, even more preferably 5.0-10, even more preferably 5.0-8.0. is there.

  The degree of polymerization of the cationized polyvinyl alcohol is preferably 220 or more, more preferably 300 or more, still more preferably 500 or more, and even more preferably 1000 or more, from the viewpoint of reducing the number of particles. The degree of polymerization of the cationized polyvinyl alcohol is preferably 3500 or less, more preferably 3000 or less, further preferably 2500 or less, and still more preferably 2000 or less, from the viewpoint of improving the storage stability of the polishing composition. Therefore, the degree of polymerization of the cationized polyvinyl alcohol is preferably 220 to 3500, more preferably 300 to 3000, and even more preferably 500 to 2500, from the viewpoint of reducing the number of particles and improving the storage stability of the polishing composition. More preferably, it is 1000-2000. Here, the degree of polymerization of the polymer compound is generally the number of repeating units constituting the polymer molecule, but the degree of polymerization of the cationized polyvinyl alcohol in the present invention is the repeating unit of (d1). It means the sum of the number and the number of repeating units of (d2).

  The weight average molecular weight of the cationized polyvinyl alcohol is preferably 5000 or more, more preferably 20000 or more, still more preferably 50000 or more, and even more preferably 80000 or more from the viewpoint of reducing the number of particles. From the viewpoint of improving the storage stability of the polishing composition, the weight average molecular weight of the cationized polyvinyl alcohol is preferably 500,000 or less, more preferably 300000 or less, still more preferably 200000 or less, and even more preferably 100000 or less. Therefore, the weight average molecular weight of the cationized polyvinyl alcohol is preferably 5000 to 500000, more preferably 20000 to 300000, still more preferably 50000 to 200000, even more from the viewpoint of reducing the number of particles and improving the storage stability of the polishing composition. Preferably it is 80000-100,000. Here, the weight average molecular weight can be determined by gel permeation chromatography using pullulan as a standard under the measurement conditions described in the examples.

  From the viewpoint of reducing the number of particles, the content of the cationized polyvinyl alcohol in the polishing composition of the present invention is preferably 0.0001 wt% (1 wt ppm) or more, and 0.0010 wt% (10 wt ppm) or more. More preferably, 0.0025% by weight (25 ppm by weight) or more is further preferable, and 0.0040% by weight (40 ppm by weight) or more is even more preferable. Further, from the viewpoint of reducing the number of particles, it is 0.0300 wt% (300 wtppm) or less, preferably 0.0200 wt% (200 wtppm) or less, more preferably 0.0150 wt% (150 wtppm) or less. Preferably, 0.0125 weight% (125 weight ppm) or less is further more preferable, and 0.0080 weight% (80 weightppm) or less is further more preferable. Therefore, the content of the cationized polyvinyl alcohol is preferably 0.0001 to 0.0300 wt% (1 to 300 wt ppm), and 0.0010 to 0.0200 wt% (10 to 200 wt%) from the viewpoint of reducing the number of particles. Weight ppm) is more preferred, 0.0025 to 0.0150 wt% (25 to 150 wtppm) is more preferred, 0.0040 to 0.0125 wt% (40 to 125 wtppm) is even more preferred, and 0040-0.0080 wt% (40-80 wtppm) is even more preferred.

[Aqueous medium (component E)]
Examples of the aqueous medium (component E) contained in the polishing liquid composition of the present embodiment include water such as ion-exchanged water and ultrapure water, or a mixed medium of water and a solvent. Solvents that can be mixed with (for example, alcohols such as ethanol) are preferred. Of these, ion-exchanged water or ultrapure water is more preferable, and ultrapure water is more preferable. When the component E of the present invention is a mixed medium of water and a solvent, the ratio of water to the entire mixed medium as the component E is not particularly limited, but is 95% by weight or more from the viewpoint of economy. Is preferable, 98% by weight or more is more preferable, and substantially 100% by weight is further preferable.

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

  The pH at 25 ° C. of the polishing composition of the present invention is 8 or more, preferably 9 or more, more preferably 9.5 or more, and even more preferably 10.0 or more, from the viewpoint of reducing the number of particles. The pH is 12 or less, preferably 11 or less, more preferably 10.8 or less, and even more preferably 10.5 or less, from the viewpoint of reducing the number of particles. Therefore, from the viewpoint of reducing the number of particles, the pH is 8 to 12, preferably 9 to 11, more preferably 9.5 to 10.8, and further preferably 10.0 to 10.5. The pH can be adjusted by appropriately adding a water-soluble alkali compound (component B) and / or a known 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. 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.

  In the polishing liquid composition of the present invention, the pH adjuster, preservative, alcohols, chelating agent, cationic surfactant, anionic surfactant, nonionic, as long as the effects of the present invention are not hindered. May contain at least one optional component selected from a surfactant and an oxidizing agent.

  Examples of the cationic surfactant include aliphatic amine salts and aliphatic ammonium salts.

  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 surfactants include, for example, ether types such as polyoxyethylene alkyl ether, ether ester types such as glycerin ester polyoxyethylene ether, ester types such as polyethylene glycol fatty acid ester, glycerin ester, and sorbitan ester. Can be mentioned.

  When a nonionic surfactant is contained in the polishing composition of the present invention, the content is preferably 0.0001 to 0.0010 wt% (1 to 10 ppm by weight) from the viewpoint of reducing the number of particles, 0.0001-0.0005 weight% (1-5 weight ppm) is more preferable, and 0.0002-0.0005 weight% (2-5 weight ppm) is further more preferable.

  Next, an example of the manufacturing method of the polishing liquid composition of this embodiment is demonstrated.

  An example of the manufacturing method of the polishing liquid composition of this embodiment is not restrict | limited at all, For example, a silica particle (component A), a water-soluble alkali compound (component B), and a C1-C4 alkylsulfonic acid. At least one compound selected from the group consisting of a salt and an alkyl sulfate having 1 to 4 carbon atoms (component C), cationized polyvinyl alcohol (component D), an aqueous medium (component E), and as necessary Can be prepared by mixing optional components.

  The order of mixing these components is not particularly limited, and all components may be mixed at the same time. However, from the viewpoint of sufficiently preventing aggregation of silica particles (component A), cationized polyvinyl alcohol (component D) And silica particles (component A) are preferably dispersed in an aqueous medium (component E) in which a water-soluble alkali compound (component B) is dissolved.

  Dispersion of the silica particles (component A) in the aqueous medium (component E) 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 formed by aggregation of silica particles are contained in the aqueous medium, it is preferable to remove the coarse particles by centrifugation, filtration using a filter, or the like.

  The polishing composition of the present invention may be obtained by preparing a high concentration precursor composition and diluting it with an aqueous medium (component E). Specifically, the concentration of the total amount of components other than the aqueous medium in the precursor composition is 5 to 20% by weight in the precursor composition from the viewpoint of productivity, ease of distribution, and storage stability of the precursor composition. (50000-200000 wtppm) is preferable, 8-20 wt% (80000-200000 wtppm) is more preferable, and 8-15 wt% (80000-150,000 wtppm) is more preferable.

  The polishing liquid composition of the present invention is used, for example, in a polishing process of a silicon wafer (wafer to be polished) in the process of manufacturing a semiconductor substrate.

  The silicon wafer polishing process includes a lapping 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, and then mirroring the silicon wafer surface. There are rough polishing and finish polishing processes. The polishing composition of the present invention is more preferably used in the above-described finish polishing step.

<Measuring method of average primary particle size of abrasive>
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 was taken so that filter waste was not mixed and finely pulverized with a mortar to obtain a measurement sample.

<Measuring method of average secondary particle size of abrasive>
The average secondary particle diameter (nm) of the abrasive was such that the abrasive was added to ion-exchanged water so that the concentration of the abrasive was 0.5% by weight, and then the resulting aqueous solution was 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).

<Method for measuring weight average molecular weight of cationized polyvinyl alcohol>
The weight average molecular weight of the cationized polyvinyl alcohol was calculated based on the peak in the chromatogram obtained by applying the gel permeation chromatography (GPC) method under the following conditions.
Measuring device: HLC-8320GPC (manufactured by Tosoh Corporation)
Column: α-M + α-M (manufactured by Tosoh Corporation)
Eluent: 0.15 mol / L Na ₂ SO ₄ , 1% CH ₃ COOH / water Flow rate: 1.0 mL / min
Sample size: 1 mg / mL
Injection volume: 100 μL
Column temperature: 40 ° C
Detector: RI detector Standard substance: Pullulan (Molecular weight: 788,000, 194,000, 473,000, 5900, all manufactured by Shodex)

(1) Preparation of polishing liquid composition Silica particles (colloidal silica), ion-exchanged water, 29% ammonia water (for Kanto Chemical Co., Ltd., electronic industry), silica particle adsorbent, cationized polyvinyl alcohol (PVA), and poly Oxyethylene alkyl ether (Emulgen 409PV, polyoxyethylene oleyl ether, HLB12, manufactured by Kao Corporation) was stirred and mixed to obtain polishing liquid compositions of Examples 1 to 14 and Comparative Examples 1 to 14. The silica particles (colloidal silica) used for preparing the polishing composition have an average primary particle size of 35 nm, an average secondary particle size of 65 nm, and an association degree of 1.86. In each polishing composition, the ammonia content is 0.0100 wt% (100 wt ppm), and the polyoxyethylene alkyl ether content is 0.0002 wt% (2 wt ppm). The content of silica particles, the content of silica particle adsorbent, and the content of cationized polyvinyl alcohol are as shown in Table 3, respectively. The pH (25 ° C.) of the polishing composition was in the range of 10.1 to 10.3. The pH was adjusted by adding ammonia as needed. The balance is ion exchange water. Table 3 also shows the weight ppm ratio of silica particle adsorbent to silica particles (weight ppm of silica particle adsorbent / ppm of silica particles). Details of the cationized polyvinyl alcohol and silica particle adsorbent are shown in Tables 1 and 2, respectively.

  In addition, cationized PVA-1 and 2 in Table 1 copolymerize a monomer compound that is a supply source of the structural unit (d2) and a monomer compound that is a supply source of the structural unit (d3), The obtained copolymer was obtained by partially saponifying.

  In the cationized PVA-1 and 2 in Table 1, the total molar concentration of the structural unit (d1), the structural unit (d2), and the structural unit (d3) in all the structural units of each polymer compound is 100 mol%. It is. The structure of cationized PVA-1 and 2 is shown below.

R ¹ is CH ₃ , and the monomer compound that is a supply source of the structural unit (d2) is vinyl acetate. The structural unit (d3) is derived from the compound represented by the general formula (4-1), Z— is Cl—, Y ¹ is —CH ₂ —, R ² is —H, and R ³ is —H and R ⁴ are —H. R ⁵ is R ² R ³ C═C (R ⁴ ) —Y ¹ —, R ⁶ is —CH ₃ , and R ⁷ is —CH ₃ .

  C number “10-16” in Table 3 indicates that the mixed alkylalkyl sulfate Na is alkylalkyl sulfate Na containing an alkyl group having 10 carbon atoms, alkylalkyl sulfate Na containing an alkyl group having 12 carbon atoms, It means a mixture of alkylalkyl sulfate Na containing an alkyl group having 14 carbon atoms and alkylalkyl sulfate Na containing an alkyl group having 16 carbon atoms.

  The molar concentration of (d3) described in Table 1 was calculated using the nitrogen amount and chlorine concentration measured by the following cationization modification rate measurement method.

[Method for measuring cationization modification rate]
(A) 1-5 mg of a sample was precisely weighed with an ultramicro balance, and the sample was decomposed in an argon-oxygen stream and converted to NO in the presence of a catalyst. The amount of nitrogen was determined by measuring the intensity of chemiluminescence emitted when NO reacts with ozone. The sample was burned and decomposed manually while checking the sample status. At this time, it was confirmed from the visual level and the detected intensity that incomplete combustion did not occur.
Measuring device: TN-10 manufactured by Mitsubishi Chemical Analytech Co., Ltd.
Electric furnace setting conditions: INLET 800 ℃
: OUTLET 900 ℃
Gas flow rate: O2 MAIN 300ml / min
: Ar 1L / min
: O2 0.5L / min
Calibration curve adjustment method: A solution obtained by dissolving aniline in toluene was used as a calibration curve sample.
(B) On the other hand, 100 mg of the sample was burned in an oxygen stream, and the generated gas was absorbed in 3% hydrogen peroxide solution. Chlorine concentration was determined by measuring chloride ions in the absorbing solution by ion chromatography.
Combustion device: QS-AB2 manufactured by Yoshida Scientific Instruments
Combustion temperature: PREH 400 ℃
: HIH 1000 ℃
Combustion gas flow rate: 2.5L / min (Ar)
Measuring device: Dionex ICS-2000
Separation column: IonPack AS418
Guard column: IonPack AG18
Eluent: 30 mM KOH
Detector: Electrical conductivity detector (c) The cationized PVA-1 and 2 contain N and Cl at a molar ratio of 1: 1, and the source of (d3) includes N Since one atom and one Cl atom are contained, the content (mol%) of the cation group is calculated from the nitrogen amount and the chlorine concentration, respectively, and the average value is calculated as the constituent unit amount (mol%) of (d3). ).

(2) Polishing Method Using the obtained polishing composition, rough polishing and final polishing were performed on the following silicon wafer under the following polishing conditions.

<Silicon wafer>
A silicon single-sided mirror wafer having a diameter of 200 mm (conductivity type: P, crystal orientation: 100, resistivity of 1Ω or more and less than 100Ω) was used as a wafer to be polished.

<Polishing conditions>
[Rough polishing]
Polishing machine: TRCP541 (manufactured by Technorise)
Polishing load: 250 g / cm ²
Polishing fluid flow rate: 200 ml / min
Plate rotation speed: 60rpm
Head rotation speed: 60rpm
Polishing time: 7 min
Polishing pad surface temperature: 23 degrees Polishing pad: SUBA400 (Nitta Haas Co., Ltd.)

[Finishing]
Polishing machine: SPP600S (Okamoto Machine Tool Manufacturing Co., Ltd.)
Polishing load: 100 g / cm ²
Polishing fluid flow rate: 200 ml / min
Plate rotation speed: 60rpm
Head rotation speed: 100 rpm
Polishing time: 5 min
Polishing pad surface temperature: 23 degrees Polishing pad: CIEGAL 7355

(3) Evaluation method <Measurement of the number of particles>
After the silicon wafer (wafer to be polished) was roughly polished, finished polished, cleaned and dried according to the polishing method described above, it remained on the silicon wafer using a wafer defect device (SP-1 DLS, manufactured by KLA-Tencor). The number of particles was measured. In addition, the foreign material whose maximum length is 50 nm or more was counted as a particle.

  As shown in Table 3, when the polishing liquid compositions of Examples 1 to 14 were used, the number of particles remaining on the silicon wafer surface was smaller than when the polishing liquid compositions of Comparative Examples 1 to 14 were used. .

  By using the polishing composition of the present invention, the number of particles remaining on the surface 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 (7)

Silica particles (component A);
A water-soluble alkali compound (component B);
At least one compound (component C) selected from the group consisting of alkyl sulfonates having 1 to 4 carbon atoms and alkyl sulfates having 1 to 4 carbon atoms;
Cationized polyvinyl alcohol (component D);
An aqueous medium (component E),
The component D includes a structural unit (d1) represented by the following general formula (1), a structural unit (d2) represented by the following general formula (2), and a structural unit represented by the following general formula (3). (D3), the molar concentration of the structural unit (d3) is 0.001 to 1.5 mol% in all the structural units of the component D,
The content of component C is 0.0300% by weight or less,
A polishing composition for a silicon wafer having a pH of 8 to 12 at 25 ° C.

In the formula (2), R ¹ is an alkyl group having 1 to 3 carbon atoms, and in the formula (3), X has a cationic group in the molecule and can be copolymerized with a vinyl alcohol lower fatty acid ester. A structural unit derived from a saturated compound.   The polishing composition for silicon wafers according to claim 1, wherein the content of silica particles (component A) is 0.0500 to 0.5000% by weight.   The polishing composition for a silicon wafer according to claim 1 or 2, wherein the content of the cationized polyvinyl alcohol (component D) is 0.0001 to 0.0300 wt%.   The polishing composition for a silicon wafer according to any one of claims 1 to 3, wherein the water-soluble alkali compound (component B) is a water-soluble amine compound.   The polishing composition for a silicon wafer according to any one of claims 1 to 4, wherein the component C comprises an alkyl sulfonate having 1 to 4 carbon atoms.   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 5.   The manufacturing method of a semiconductor substrate including the process of grind | polishing a silicon wafer using the polishing liquid composition for silicon wafers in any one of Claims 1-5.