JP7349309B2 - Polishing composition for silicon wafers - Google Patents

Description

The present invention relates to a polishing composition for silicon wafers.

In order to achieve higher integration and higher speed of integrated circuits such as ULSI used in computers, design rules for semiconductor devices are becoming increasingly finer year by year. As a result, the number of cases in which finer surface defects adversely affect the performance of semiconductor devices is increasing, and the importance of managing nano-order defects, which have not been considered a problem in the past, is increasing.

Surface defect inspection equipment is used to manage surface defects on silicon wafers. Defects detected by the surface defect inspection device include foreign matter and residue on the silicon wafer that could not be removed in the polishing, rinsing, and cleaning steps. A typical surface defect inspection device detects the presence and size of defects by irradiating the surface of a silicon wafer with light such as a laser beam, and receiving and analyzing the reflected light as a signal.

When strong light is irradiated onto the mirror-finished surface of a silicon wafer after polishing or after polishing and rinsing, cloudiness may appear due to diffused reflection caused by very fine roughness on the silicon wafer surface. This cloudiness is called haze, and haze can be used as a measure of the roughness of the silicon wafer surface. When there is haze on the surface of a silicon wafer, diffusely reflected light generated by the haze becomes noise, which may interfere with defect detection by a surface defect inspection device. Therefore, as the size of defects to be detected, that is, the size of defects to be managed, decreases, the need to reduce haze increases.

Conventionally, polishing compositions containing a polishing aid made of a block polyether (hereinafter referred to as PEP) represented by the following general formula (1), an abrasive such as colloidal silica, and water have been proposed. (See Patent Document 1). The polishing composition aims to reduce haze by polishing the silicon wafer surface by mechanical polishing with an abrasive and adjusting the surface tension of the polishing composition to be suitable for polishing the silicon wafer surface with a polishing aid. It is something to do.

HO-(PO) _d- (EO) _e- (PO) _f -H...(1)
(In the formula, PO represents an oxypropylene group, EO represents an oxyethylene group, and d, e, and f represent an integer of 1 or more.)

However, it is difficult to polish the surface of a silicon wafer using the polishing composition, and the polishing composition has a weak haze reducing effect. Therefore, a polishing composition that attempts to further enhance the haze reducing effect has also been provided (Patent Document 2).

Japanese Patent Application Publication No. 2001-110760 Japanese Patent Application Publication No. 2005-85858

Although the polishing composition disclosed in Patent Document 2 can also reduce haze, an object of the present invention is to reduce the haze of silicon wafers by another means.

In order to solve the above problems, the present invention includes one or more water-soluble polymers and two or more surfactants, and one or more of the two or more surfactants is a polypropylene glycol compound. A polishing composition for silicon wafers is provided.

The polishing composition of the present invention can reduce haze of silicon wafers.

The present invention will be explained below. Note that the present invention is not limited only to the following embodiments. Further, unless otherwise specified, operations and measurements of physical properties, etc. are performed under conditions of room temperature (20 to 25°C)/relative humidity of 40 to 50% RH.

The present invention provides silicone silicone containing one or more water-soluble polymers and two or more surfactants, one or more of the two or more surfactants being a polypropylene glycol compound. It is a polishing composition for wafers (hereinafter, the "polishing composition for silicon wafers" may also be simply referred to as "polishing composition"). According to this configuration, haze of the silicon wafer can be reduced.

According to one embodiment of the present invention, the polishing composition is stored and transported in the form of a concentrated solution in which each component is mixed at a relatively high concentration, and the polishing composition can be obtained as it is or by diluting the concentrated solution. Silicon wafers can be polished by using the polishing composition.

<Water-soluble polymer>
The polishing composition of the present invention contains one or more water-soluble polymers. The water-soluble polymer adheres to the surface of the object to be polished and protects the surface of the object to be polished from uneven or excessive etching that may occur due to the action of the optionally contained basic compound. This can improve the surface quality after polishing.

In this specification, "water-soluble" means that the solubility in water (25°C) is 1 g/100 mL or more, and "polymer" means that the weight average molecular weight is 1,000 or more (common ) refers to polymers. The weight average molecular weight can be measured by gel permeation chromatography (GPC), and specifically, the value measured by the method described in the Examples is used. Further, only in cases where measurement cannot be performed by GPC, the molecular weight calculated from the molecular formula is employed as the weight average molecular weight.

In one embodiment of the present invention, a water-soluble polymer having at least one functional group selected from a cationic group, an anionic group, and a nonionic group in its molecule can be used.

In one embodiment of the present invention, the water-soluble polymer contains a hydroxyl group, a carboxyl group, an acyloxy group, a sulfo group, an amide structure, an imide structure, a quaternary ammonium structure, a heterocyclic structure, a vinyl structure, etc. in the molecule. Things can be mentioned.

In one embodiment of the present invention, the water-soluble polymer includes a polymer having a structural unit derived from vinyl alcohol (hereinafter also referred to as "polyvinyl alcohol polymer"), a cellulose derivative, a starch derivative, and a water-soluble polymer having a nitrogen atom. Polymers and the like can be mentioned. Among these, it is preferable to contain at least one of a polyvinyl alcohol polymer and a cellulose derivative. A polishing composition containing these polymers tends to reduce the haze of the object to be polished.

(Polyvinyl alcohol polymer)
The polyvinyl alcohol polymer may contain only vinyl alcohol units (hereinafter also referred to as "VA units") as repeating units, or may contain repeating units other than VA units (hereinafter also referred to as "non-VA units") in addition to VA units. .) may be included. The vinyl alcohol unit is a structural moiety represented by the following chemical formula: -CH ₂ -CH(OH)-; The polyvinyl alcohol-based polymer may be a random copolymer containing VA units and non-VA units, or may be a block copolymer or a graft copolymer. The polyvinyl alcohol-based polymer may contain only one type of non-VA unit, or may contain two or more types of non-VA units.

The polyvinyl alcohol polymer used in the polishing composition disclosed herein may be unmodified polyvinyl alcohol (unmodified PVA) or modified polyvinyl alcohol (modified PVA). Here, unmodified PVA is produced by hydrolyzing (saponifying) polyvinyl acetate, and contains repeating units (-CH ₂ -CH(OCOCH ₃ )-) of vinyl polymerized structure of vinyl acetate and non-VA units. A polyvinyl alcohol polymer that does not substantially contain repeating units. The degree of saponification of the unmodified PVA may be, for example, 60% or more, and from the viewpoint of water solubility, it may be 70% or more, 80% or more, or 90% or more. In some embodiments, unmodified PVA having a saponification degree of 95% or more or 98% or more can be preferably employed as the water-soluble polymer compound.

Examples of non-VA units that can be included in modified PVA include repeating units derived from N-vinyl type monomers and N-(meth)acryloyl type monomers, repeating units derived from ethylene, and repeating units derived from alkyl vinyl ethers, which will be described later. units, repeating units derived from vinyl esters of monocarboxylic acids having 3 or more carbon atoms, and the like, but are not limited thereto. A preferred example of the N-vinyl type monomer is N-vinylpyrrolidone. A suitable example of the N-(meth)acryloyl type monomer is N-(meth)acryloylmorpholine. The alkyl vinyl ether may be a vinyl ether having an alkyl group having 1 to 10 carbon atoms, such as propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, and the like. The vinyl ester of a monocarboxylic acid having 3 or more carbon atoms is a vinyl ester of a monocarboxylic acid having 3 or more carbon atoms and 7 or less carbon atoms, such as vinyl propanoate, vinyl butanoate, vinyl pentanoate, vinyl hexanoate, etc. obtain.

The polyvinyl alcohol polymer has VA units and at least one selected from oxyalkylene groups, carboxy groups, sulfo groups, amino groups, hydroxyl groups, amide groups, imide groups, nitrile groups, ether groups, ester groups, and salts thereof. It may also be a modified PVA containing a non-VA unit having a structure.

The polyvinyl alcohol polymer may be modified PVA in which a portion of the VA units contained in the polyvinyl alcohol polymer are acetalized with an aldehyde compound or a ketone compound. In a preferred embodiment of the technology disclosed herein, the acetalized modified PVA is a water-soluble polymer obtained by an acetalization reaction between the above-mentioned unmodified PVA and an aldehyde compound.

In one embodiment of the present invention, the aldehyde compound used to produce the acetalized modified PVA is not particularly limited. In one preferred embodiment, the aldehyde compound has 1 to 7 carbon atoms, more preferably 2 to 7 carbon atoms.

Examples of the aldehyde compounds include formaldehyde; linear or branched alkyl aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, t-butyraldehyde, hexylaldehyde, and n-pentylaldehyde; cyclohexane carbaldehyde, benzaldehyde; Alicyclic or aromatic aldehydes such as; These may be used alone or in combination of two or more. Further, except for formaldehyde, one or more hydrogen atoms may be substituted with halogen or the like. Among these, linear or branched alkyl aldehydes are preferred because they have high solubility in water and facilitate the acetalization reaction, and among these, acetaldehyde, n-propyl aldehyde, n-butyraldehyde, and n-pentyl aldehyde are preferable. It is more preferable that

As the aldehyde compound, in addition to the above, aldehyde compounds having 8 or more carbon atoms such as 2-ethylhexylaldehyde, nonylaldehyde, and decylaldehyde may be used. Furthermore, as the polyvinyl alcohol polymer, cationically modified polyvinyl alcohol into which a cationic group such as a quaternary ammonium structure has been introduced may be used. The above-mentioned cation-modified polyvinyl alcohol is introduced with a cationic group derived from a monomer having a cationic group such as diallyldialkylammonium salt, N-(meth)acryloylaminoalkyl-N,N,N-trialkylammonium salt, etc. The following are examples of what has been done.

The ratio of the number of moles of VA units to the number of moles of all repeating units constituting the polyvinyl alcohol polymer may be, for example, 5% or more, 10% or more, 20% or more, or 30% or more. . Although not particularly limited, in some embodiments, the molar ratio of the VA units may be 50% or more, 65% or more, 75% or more, 80% or more, It may be 90% or more (for example, 95% or more, or 98% or more). Substantially 100% of the repeating units constituting the polyvinyl alcohol polymer may be VA units. Here, "substantially 100%" means that the polyvinyl alcohol polymer does not contain non-VA units, at least intentionally, and typically the number of moles of non-VA units relative to the number of moles of all repeating units. The ratio is less than 2% (for example, less than 1%), including the case where it is 0%. In some other embodiments, the ratio of the number of moles of VA units to the number of moles of all repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 95% or less, may be 90% or less, and may be 80% or less. It may be 70% or less.

The content of VA units (content on a weight basis) in the polyvinyl alcohol-based polymer may be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, or 30% by weight or more. Although not particularly limited, in some embodiments, the content of the VA unit may be 50% by weight or more (for example, more than 50% by weight), 70% by weight or more, and 80% by weight or more (for example, more than 50% by weight). For example, it may be 90% by weight or more, 95% by weight or more, or 98% by weight or more). Substantially 100% by weight of the repeating units constituting the polyvinyl alcohol polymer may be VA units. Here, "substantially 100% by weight" means that at least intentionally no non-VA units are contained as repeating units constituting the polyvinyl alcohol-based polymer, typically non-VA units in the polyvinyl alcohol-based polymer. This means that the content of is less than 2% by weight (for example, less than 1% by weight). In some other embodiments, the content of VA units in the polyvinyl alcohol-based polymer may be, for example, 95% by weight or less, 90% by weight or less, 80% by weight or less, or 70% by weight or less. .

The polyvinyl alcohol-based polymer may contain a plurality of polymer chains having different contents of VA units in the same molecule. Here, the polymer chain refers to a portion (segment) that constitutes a part of one molecule of polymer. For example, polyvinyl alcohol-based polymers have a polymer chain A with a content of VA units greater than 50% by weight and a content of VA units less than 50% by weight (i.e. a content of non-VA units greater than 50% by weight). ) may be included in the same molecule.

Polymer chain A may contain only VA units as repeating units, or may contain non-VA units in addition to VA units. The content of VA units in the polymer chain A may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In some embodiments, the content of VA units in polymer chain A may be 95% by weight or more, or 98% by weight or more. Substantially 100% by weight of the repeating units constituting the polymer chain A may be VA units.

Polymer chain B may contain only non-VA units as repeating units, or may contain VA units in addition to non-VA units. The content of non-VA units in polymer chain B may be 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In some embodiments, the content of non-VA units in polymer chain B may be 95% by weight or more, and may be 98% by weight or more. Substantially 100% by weight of the repeating units constituting polymer chain B may be non-VA units.

Examples of polyvinyl alcohol polymers containing polymer chain A and polymer chain B in the same molecule include block copolymers and graft copolymers containing these polymer chains. The above-mentioned graft copolymer may be a graft copolymer having a structure in which a polymer chain B (side chain) is grafted onto a polymer chain A (main chain), and a polymer chain A (side chain) is grafted onto a polymer chain B (main chain). It may also be a graft copolymer having a structure in which a chain) is grafted. In one embodiment, a polyvinyl alcohol polymer having a structure in which polymer chain B is grafted onto polymer chain A can be used.

Examples of polymer chain B include a polymer chain whose main repeating unit is a repeating unit derived from an N-vinyl type monomer, and a polymer chain whose main repeating unit is a repeating unit derived from an N-(meth)acryloyl type monomer. , a polymer chain having an oxyalkylene unit as a main repeating unit, and the like. In addition, in this specification, the main repeating unit refers to a repeating unit contained in an amount exceeding 50% by weight, unless otherwise specified.

A preferred example of the polymer chain B is a polymer chain having an N-vinyl type monomer as a main repeating unit, that is, an N-vinyl type polymer chain. The content of repeating units derived from N-vinyl monomers in the N-vinyl polymer chain is typically more than 50% by weight, may be 70% by weight or more, and may be 85% by weight or more. The content may be 95% by weight or more. Substantially all of the polymer chain B may be repeating units derived from N-vinyl type monomers.

In this specification, examples of N-vinyl type monomers include monomers having nitrogen-containing heterocycles (eg, lactam rings) and N-vinyl linear amides. Specific examples of N-vinyllactam type monomers include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl- Examples include 3,5-morpholinedione. Specific examples of the N-vinyl chain amide include N-vinylacetamide, N-vinylpropionamide, N-vinylbutyric acid amide, and the like. Polymer chain B is, for example, an N-vinyl polymer chain in which more than 50% by weight (for example, 70% or more, or 85% or more, or 95% or more) of its repeating units are N-vinylpyrrolidone units. obtain. Substantially all of the repeating units constituting polymer chain B may be N-vinylpyrrolidone units.

Another example of the polymer chain B is a polymer chain whose main repeating unit is a repeating unit derived from an N-(meth)acryloyl type monomer, that is, an N-(meth)acryloyl-based polymer chain. The content of repeating units derived from N-(meth)acryloyl type monomers in the N-(meth)acryloyl-based polymer chain is typically more than 50% by weight, and may be 70% by weight or more, and 85% by weight or more. It may be at least 95% by weight, or at least 95% by weight. Substantially all of the polymer chain B may be repeating units derived from N-(meth)acryloyl type monomers.

In this specification, examples of N-(meth)acryloyl type monomers include linear amides having an N-(meth)acryloyl group and cyclic amides having an N-(meth)acryloyl group. Examples of linear amides having an N-(meth)acryloyl group include (meth)acrylamide; N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl( N-alkyl (meth)acrylamide such as meth)acrylamide, Nn-butyl(meth)acrylamide; N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide ) acrylamide, N,N-dialkyl (meth)acrylamide such as N,N-diisopropyl (meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide; and the like. Examples of the cyclic amide having an N-(meth)acryloyl group include N-(meth)acryloylmorpholine, N-(meth)acryloylpyrrolidine, and the like.

Other examples of the polymer chain B include a polymer chain containing an oxyalkylene unit as a main repeating unit, that is, an oxyalkylene-based polymer chain. The content of oxyalkylene units in the oxyalkylene polymer chain is typically more than 50% by weight, may be 70% by weight or more, may be 85% by weight or more, and may be 95% by weight or more. There may be. Substantially all of the repeating units contained in polymer chain B may be oxyalkylene units.

Examples of oxyalkylene units include oxyethylene units, oxypropylene units, oxybutylene units, and the like. Each such oxyalkylene unit can be a repeating unit derived from the corresponding alkylene oxide. The number of oxyalkylene units contained in the oxyalkylene polymer chain may be one type, or two or more types. For example, it may be an oxyalkylene polymer chain containing a combination of oxyethylene units and oxypropylene units. In an oxyalkylene polymer chain containing two or more types of oxyalkylene units, those oxyalkylene units may be random copolymers of corresponding alkylene oxides, block copolymers, or graft copolymers. Good too.

Still other examples of polymer chain B include polymer chains containing repeating units derived from alkyl vinyl ethers (e.g. vinyl ethers having an alkyl group having 1 to 10 carbon atoms), monocarboxylic acid vinyl esters (e.g. vinyl ethers having an alkyl group having 1 to 10 carbon atoms); Polymer chains containing repeating units derived from (vinyl esters of monocarboxylic acids of 3 or more), in which some of the VA units are acetalized with aldehydes (e.g., alkyl aldehydes having an alkyl group having 1 to 7 carbon atoms) Examples thereof include a polymer chain, a polymer chain into which a cationic group (for example, a cationic group having a quaternary ammonium structure) is introduced, and the like.

As the polyvinyl alcohol polymer in the polishing composition disclosed herein, unmodified PVA, modified PVA, or a combination of unmodified PVA and modified PVA may be used. In an embodiment in which unmodified PVA and modified PVA are used in combination, the amount of modified PVA used with respect to the total amount of polyvinyl alcohol-based polymer contained in the polishing composition may be, for example, less than 95% by weight, and may be 90% by weight or less. , 75% by weight or less, 50% by weight or less, 30% by weight or less, 10% by weight or less, 5% by weight or less, or 1% by weight or less. The polishing composition disclosed herein can be preferably implemented, for example, in an embodiment using only one or more types of unmodified PVA as the polyvinyl alcohol polymer.

(cellulose derivative)
In one embodiment of the present invention, the term "cellulose derivative" refers to a cellulose derivative in which some of the hydroxyl groups of cellulose are substituted with other different substituents. Regarding the types of cellulose derivatives, one type may be used alone, or two or more types may be used in combination. Examples of cellulose derivatives include cellulose derivatives such as hydroxyethylcellulose (HEC), hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, carboxymethylcellulose, and pullulan.

(Water-soluble polymer with nitrogen atoms)
According to one embodiment of the present invention, the water-soluble polymer contains nitrogen atoms from the viewpoint of reducing haze. Water-soluble polymers having nitrogen atoms have adsorption properties to abrasive grains, but can buffer the mechanical action of abrasive grains and reduce haze of the object to be polished.

In one embodiment of the present invention, one type of water-soluble polymer having a nitrogen atom may be used alone, or two or more types may be used in combination. Examples of water-soluble polymers having a nitrogen atom include polyN-acryloylmorpholine (PACMO), polyN-vinylpyrrolidone (PVP), polyhydroxylethyl acrylamide (PHEAA), polyN-vinylimidazole (PVI), and polyN -Vinylcarbazole, polyN-vinylcaprolactam, polyN-vinylpiperidine and the like. Among these, it is preferable to include polyN-acryloylmorpholine (PACMO) from the viewpoint of reducing haze of the object to be polished.

According to one embodiment of the present invention, the weight average molecular weight of the water-soluble polymer is preferably 5,000 or more, more preferably 6,000 or more, and preferably 1×10 ⁴ or more. More preferred. According to this embodiment, there is a technical effect that the haze reduction effect is improved. According to one embodiment of the present invention, the weight average molecular weight of the water-soluble polymer is preferably 200 x 10 ⁴ or less, and 100 x 10 ⁴ or less, from the viewpoint of haze reduction, washability, etc. is more preferable, and even more preferably 50×10 ⁴ or less. In addition, in the above, when the polishing composition contains two or more types of water-soluble polymers, the weight average molecular weight of the water-soluble polymer is 5, 000 or more. With such an embodiment, the intended effects of the present invention can be efficiently achieved.

According to one embodiment of the invention, the water-soluble polymer is a polyvinyl alcohol-based polymer. The weight average molecular weight of the polyvinyl alcohol polymer is preferably 5,000 or more, more preferably 6,000 or more, and even more preferably 1×10 ⁴ or more. According to this embodiment, there is a technical effect that the haze reduction effect is improved. According to one embodiment of the present invention, the weight average molecular weight of the polyvinyl alcohol-based polymer is preferably 100×10 ⁴ or less, more preferably 30×10 ⁴ or less, and 10×10 ⁴ or less. It is even more preferable that there be. According to such an embodiment, dispersion stability is improved.

According to one embodiment of the invention, the water-soluble polymer is a cellulose derivative. The weight average molecular weight of the cellulose derivative is preferably 5,000 or more, more preferably 1×10 ⁴ or more, and even more preferably 10×10 ⁴ or more. According to this embodiment, there is a technical effect that the haze reduction effect is improved. According to one embodiment of the present invention, the weight average molecular weight of the cellulose derivative is preferably 200×10 ⁴ or less, more preferably 150×10 ⁴ or less, and 100×10 ⁴ or less. is even more preferable. According to such an embodiment, dispersion stability is improved.

According to one embodiment of the present invention, the water-soluble polymer has a nitrogen atom. The weight average molecular weight of the water-soluble polymer having a nitrogen atom is preferably 5,000 or more, more preferably 7,500 or more, and even more preferably 1×10 ⁴ or more. According to this embodiment, there is a technical effect that the haze reduction effect is improved. According to one embodiment of the present invention, the weight average molecular weight of the water-soluble polymer having a nitrogen atom is preferably 100×10 ⁴ or less, more preferably 75×10 ⁴ or less, and 50× More preferably, it is 10 ⁴ or less. According to such an embodiment, dispersion stability is improved.

In one embodiment of the present invention, when the polishing composition is in the form of a concentrated liquid, the content of the water-soluble polymer in the polishing composition is 0.0001% by mass from the viewpoint of improving stability. It is preferably at least 0.0005% by mass, more preferably at least 0.001% by mass, and particularly preferably at least 0.01% by mass. In one embodiment of the present invention, when the polishing composition is in the form of a concentrate, the content of water-soluble polymer in the polishing composition is 5% by mass from the viewpoint of storage stability, filterability, etc. It is preferably at most 3% by mass, more preferably at most 1% by mass, and even more preferably at most 1% by mass.

In one embodiment of the present invention, when the polishing composition is in a diluted state, the content of the water-soluble polymer may be 0.00005% by mass or more from the viewpoint of improving the haze reduction effect. It is preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more, and particularly preferably 0.001% by mass or more. Further, in one embodiment of the present invention, when the polishing composition is in a diluted state, the content of the water-soluble polymer is preferably 0.1% by mass or less from the viewpoint of maintaining the polishing rate; It is more preferably 0.05% by mass or less, and even more preferably 0.01% by mass or less. In addition, in the above, when the polishing composition contains two or more types of water-soluble polymers, the content of water-soluble polymers refers to the total amount thereof. In one embodiment of the present invention, the water-soluble polymer contains hydroxyl groups from the viewpoint of reducing haze.

In one embodiment of the present invention, the polishing composition can contain two or more types of arbitrary water-soluble polymers. As the water-soluble polymer, a combination of two or more types of water-soluble polymers selected from, for example, polyvinyl alcohol polymers, cellulose derivatives, starch derivatives, and water-soluble polymers having nitrogen atoms can be used. Among these, it is preferable to include two or more types of water-soluble polymers selected from polyvinyl alcohol polymers, cellulose derivatives, and water-soluble polymers having nitrogen atoms. A polishing composition containing these water-soluble polymers tends to reduce haze of the object to be polished.

When the polishing composition is used containing two or more types of water-soluble polymers, for example, one or more types each of a polyvinyl alcohol-based polymer and a water-soluble polymer having a nitrogen atom, and a cellulose derivative and a polyvinyl alcohol-based polymer are used. Water-soluble polymers can be used in combination, such as one or more types of each, one or more types of each of a cellulose derivative and a water-soluble polymer having a nitrogen atom.

When the polishing composition contains one or more water-soluble polymers selected from a polyvinyl alcohol-based polymer and a water-soluble polymer having a nitrogen atom, the polyvinyl alcohol-based polymer and the water-soluble polymer having a nitrogen atom include the present invention. The water-soluble polymer described above can be used as an embodiment of the invention. Among them, one or more each of acetalized modified PVA and polyN-acryloylmorpholine, one or more each of unmodified PVA and polyN-acryloylmorpholine, and one or more each of unmodified PVA and polyN-vinylpyrrolidone. It is preferable to use water-soluble polymers in combination, such as one or more of each of unmodified PVA and polyhydroxylethyl acrylamide.

In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or diluted solution) containing acetalized modified PVA and polyN-acryloylmorpholine, the content ratio of acetalized modified PVA and polyN-acryloylmorpholine (acetalized The lower limit of the weight ratio of modified PVA/poly N-acryloylmorpholine is preferably 0.01 or more, may be 0.05 or more, or may be 0.15 or more (for example, 0.5 or more). . Further, the upper limit of the content ratio is not particularly limited, but is preferably 99 or less, may be 19 or less, or may be 6 or less (for example, 2 or less). The content of acetalized modified PVA and polyN-acryloylmorpholine is preferably 1:99 to 99:1 in weight ratio, may be 5:95 to 95:5, and may be 15:85 to 85:15. (for example, 65:35 to 35:65).

In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or diluted solution) containing unmodified PVA and polyN-acryloylmorpholine, the ratio of the content of unmodified PVA to polyN-acryloylmorpholine (unmodified PVA/polyN-acryloylmorpholine) The lower limit of ) is preferably 0.01 or more in weight ratio, may be 0.05 or more, or may be 0.15 or more (for example, 0.5 or more). Further, the upper limit of the content ratio is not particularly limited, but from the viewpoint of suppressing etching, it is preferably 99 or less, may be 19 or less, or may be 6 or less (for example, 2 or less). The content of unmodified PVA and polyN-acryloylmorpholine is preferably 1:99 to 99:1 in weight ratio, may be 5:95 to 95:5, and may be 15:85 to 85:15 (for example, 60 :40 to 40:60).
In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or diluted solution) containing unmodified PVA and polyN-vinylpyrrolidone, the content ratio of unmodified PVA and polyN-vinylpyrrolidone (unmodified PVA/polyN-vinylpyrrolidone) The lower limit of ) is preferably 0.01 or more in weight ratio, may be 0.05 or more, or may be 0.15 or more (for example, 0.5 or more). Further, the upper limit of the content ratio is not particularly limited, but is preferably 99 or less, may be 19 or less, or may be 6 or less (for example, 2 or less). The content of unmodified PVA and polyN-vinylpyrrolidone is preferably 1:99 to 99:1 in weight ratio, may be 5:95 to 95:5, and may be 10:90 to 90:10 (for example, 60:1). :40 to 90:10).

In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrated solution or diluted solution) containing unmodified PVA and polyhydroxylethyl acrylamide, the lower limit of the content ratio of unmodified PVA and polyhydroxylethyl acrylamide (unmodified PVA/polyhydroxylethyl acrylamide) is preferably 0.01 or more in weight ratio, may be 0.05 or more, and may be 0.3 or more (for example, 0.6 or more). Further, the upper limit of the content ratio is not particularly limited, but is preferably 99 or less, may be 75 or less, or may be 50 or less (for example, 20 or less). The content of unmodified PVA and polyhydroxylethyl acrylamide is preferably 1:99 to 99:1 in weight ratio, may be 15:85 to 98:2, and may be 25:75 to 98:2 (for example, 40:2). 60 to 95:5).
When the polishing composition contains one or more water-soluble polymers selected from cellulose derivatives and polyvinyl alcohol-based polymers, the cellulose derivatives and polyvinyl alcohol-based polymers include the water-soluble polymers described above as an embodiment of the present invention. can be used. Among them, one or more types each of hydroxyethyl cellulose and unmodified PVA, one or more types each of hydroxyethyl cellulose and acetalized modified PVA, hydroxyethyl cellulose and PVA-polyoxyalkylene copolymer (containing VA units and oxyalkylene units) A water-soluble polymer is produced by a combination of one or more of each of hydroxyethyl cellulose and one or more of PVA-polyvinylpyrrolidone copolymers (a copolymer containing VA units and N-vinylpyrrolidone units), etc. It is preferable to use

In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or diluted solution) containing hydroxyethylcellulose and unmodified PVA, the lower limit of the content ratio of hydroxyethylcellulose and unmodified PVA (hydroxyethylcellulose/unmodified PVA) is 0 in terms of weight ratio. It is preferably .01 or more, may be 0.05 or more, or may be 0.3 or more (for example, 1.5 or more). Further, the upper limit of the content ratio is not particularly limited, but is preferably 99 or less, may be 75 or less, or may be 50 or less (for example, 20 or less). The content of hydroxyethyl cellulose and unmodified PVA is preferably 1:99 to 99:1 in weight ratio, may be 15:85 to 98:2, and may be 25:75 to 98:2 (for example, 60:40 to 98:2).

In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or diluted solution) containing hydroxyethylcellulose and acetalized modified PVA, the content ratio of hydroxyethylcellulose to acetalized modified PVA (hydroxyethylcellulose/acetalized modified PVA) The lower limit of ) is preferably 0.01 or more in weight ratio, may be 0.05 or more, or may be 0.15 or more (for example, 4 or more). Further, the upper limit of the content ratio is not particularly limited, but is preferably 99 or less, may be 19 or less, or may be 6 or less (for example, 0.25 or less). The content of hydroxyethylcellulose and acetalized modified PVA is preferably 1:99 to 99:1 in weight ratio, may be 5:95 to 95:5, and may be 15:85 to 85:15 (for example, 80 :20 to 20:80).

In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or diluted solution) containing hydroxyethylcellulose and PVA-polyoxyalkylene copolymer, the content ratio of hydroxyethylcellulose and PVA-polyoxyalkylene copolymer (hydroxyethylcellulose/PVA- The lower limit of the polyoxyalkylene copolymer) is preferably 0.01 or more in terms of weight ratio, may be 0.15 or more, or may be 0.3 or more (for example, 2 or more). Further, the upper limit of the content ratio is not particularly limited, but is preferably 99 or less, may be 60 or less, or may be 40 or less (for example, 19 or less). The content of hydroxyethyl cellulose and PVA-polyoxyalkylene copolymer is preferably 1:99 to 99:1 in weight ratio, may be 15:85 to 98:2, and may be 45:55 to 95:5 ( For example, the ratio may be 70:30 to 95:5).

In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or diluted solution) containing hydroxyethylcellulose and PVA-polyvinylpyrrolidone copolymer, the content ratio of hydroxyethylcellulose and PVA-polyvinylpyrrolidone copolymer (hydroxyethylcellulose/PVA-polyvinylpyrrolidone The lower limit of the weight ratio of copolymer) is preferably 0.01 or more, may be 0.05 or more, or may be 0.15 or more (for example, 1.5 or more). Further, the upper limit of the content ratio is not particularly limited, but is preferably 99 or less, may be 75 or less, or may be 50 or less (for example, 20 or less). The content of the copolymer of hydroxyethyl cellulose and PVA-polyvinylpyrrolidone is preferably 1:99 to 99:1 in weight ratio, may be 5:95 to 99:1, and may be 15:85 to 98:2 ( For example, the ratio may be 60:40 to 98:2).

When the polishing composition contains one or more types of water-soluble polymers selected from a cellulose derivative and a water-soluble polymer having a nitrogen atom, the cellulose derivative and the water-soluble polymer having a nitrogen atom may be one of the embodiments of the present invention. The water-soluble polymer mentioned above can be used as the form. Among these, it is preferable to use water-soluble polymers in combination, such as one or more each of hydroxyethyl cellulose and polyN-vinylpyrrolidone, one or more each of hydroxyethyl cellulose and polyN-acryloylmorpholine, and the like.

In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or diluted solution) containing hydroxyethylcellulose and polyN-vinylpyrrolidone, the lower limit of the content ratio of hydroxyethylcellulose and polyN-vinylpyrrolidone (hydroxyethylcellulose/polyN-vinylpyrrolidone) preferably has a weight ratio of 0.01 or more, may be 0.05 or more, or may be 0.15 or more (for example, 1.5 or more). Further, the upper limit of the content ratio is not particularly limited, but is preferably 99 or less, may be 19 or less, or may be 6 or less (for example, 0.7 or less). The content of hydroxyethylcellulose and polyN-vinylpyrrolidone is preferably 1:99 to 99:1 in weight ratio, may be 5:95 to 95:5, and may be 15:85 to 85:15 (for example, 60:1). 40 to 40:60).

In one embodiment of the present invention, when two or more types of water-soluble polymers are used, the content ratio of the water-soluble polymers is not particularly limited. For example, in a polishing composition (concentrate or diluted solution) containing hydroxyethylcellulose and polyN-acryloylmorpholine, the lower limit of the content ratio of hydroxyethylcellulose and polyN-acryloylmorpholine (hydroxyethylcellulose/polyN-acryloylmorpholine) preferably has a weight ratio of 0.01 or more, may be 0.05 or more, or may be 0.15 or more (for example, 0.5 or more). Further, the upper limit of the content ratio is not particularly limited, but is preferably 99 or less, may be 19 or less, or may be 9 or less (for example, 6 or less). The content of hydroxyethylcellulose and polyN-acryloylmorpholine is preferably 1:99 to 99:1 in weight ratio, may be 5:95 to 95:5, and may be 25:75 to 90:10 (for example, 50:1). 50 to 85:15).

<Surfactant>
The polishing composition of the present invention contains two or more types of surfactants. The surfactant adheres to the surface of the object to be polished and protects the surface of the object to be polished from uneven or excessive etching that may occur due to the action of the optionally contained basic compound. This can improve the surface quality after polishing.

According to one embodiment of the present invention, one or more of the two or more surfactants is a polypropylene glycol compound. In the present invention, by adding a (hydrophobic) propylene glycol compound, the newly exposed silicon surface (hydrophobic) due to polishing can be quickly protected, and as a result, the roughness (haze) of the silicon wafer can be further suppressed. I can do it.

In one embodiment of the present invention, one or more of the two or more surfactants is a polyoxyalkylene nonionic surfactant. According to this embodiment, the intended effects of the present invention can be efficiently achieved.

(Polypropylene glycol compound)
In the present invention, a "polypropylene glycol compound" is a molecule with propylene oxide as its main skeleton, has two or more oxypropylene groups (PO) and hydroxyl groups (OH) in the molecule, and has an oxyethylene group in the molecule. Refers to a compound that does not have (EO).

In one embodiment of the present invention, the polypropylene glycol compound may be a monool type, a diol type, a triol type, or a mixture thereof. Among these, diol type is preferred.

In one embodiment of the present invention, the polypropylene glycol compounds include polypropylene glycol, polyoxypropylene trimethylol propane ether, polyoxypropylene sorbitol ether, polyoxypropylene monoglyceryl ether, polyoxypropylene diglyceryl ether, and polyoxypropylene trimethylol propane ether. Examples include glyceryl ether, monoalkyl ether having a polyoxypropylene polyglyceryl ether skeleton, condensates of polypropylene glycol and polyglucoside, and condensates of polypropylene glycol and sucrose. Among these, polypropylene glycol is preferred.

(Polyoxyalkylene nonionic surfactant)
In the present invention, "polyoxyalkylene nonionic surfactant" refers to the following two groups of compounds;
(1) Polyoxyethylene-added nonionic surfactant: a polymer to which polyoxyethylene is added (grafted),
(2) Block type polyether nonionic surfactant: block type polyether represented by the following general formula (2),
HO-(EO)a-(PO)b-(EO)c-H...(2)
(In the formula, EO represents an oxyethylene group, PO represents an oxypropylene group, and a, b and c represent an integer of 1 or more),
It is.

In one embodiment of the present invention, the polyoxyalkylene nonionic surfactant is a polyoxyethylene-added nonionic surfactant. The HLB value of the polyoxyethylene-added nonionic surfactant is preferably 15 or less, more preferably 13 or less. Having such an upper limit value is effective in suppressing roughness on the silicon wafer surface, and reduces haze on the silicon wafer surface. In one embodiment of the present invention, the HLB value of the polyoxyethylene-added nonionic surfactant is preferably 8 or more, more preferably 10 or more, and even more preferably 12 or more. Having such a lower limit value has the effect of reducing haze.

In this specification, the HLB (Hydrophile-Lipophile Balance) value is defined by the Griffin method. In the Griffin method, the HLB value is calculated by 20×(sum of molecular weights of hydrophilic parts)/(sum of molecular weights of hydrophilic parts and hydrophobic parts). Examples of hydrophilic parts include oxyethylene groups, hydroxyl groups, carboxyl groups, and esters, and examples of hydrophobic parts include oxypropylene groups, oxybutylene groups, and alkyl groups.

In one embodiment of the present invention, the average number of moles of oxyethylene added in a polyoxyethylene-added nonionic surfactant is, in principle, the average number of moles of oxyethylene units in 1 mole of polyoxyethylene adduct. It is a value. However, in the case of polyoxyethylene adducts that have multiple polyoxyethylene chains in one molecule, such as polyoxyethylene sorbitan monooleate, the number of oxyethylene units contained in one molecule of the polyoxyethylene adduct is The average value of the total number of moles divided by the number of polyoxyethylene chains contained in one molecule is defined as the average number of added moles of oxyethylene. That is, it can be said that the average number of moles of oxyethylene added in a polyoxyethylene-added nonionic surfactant indicates the length of the polyoxyethylene chain contained in the surfactant.

In one embodiment of the present invention, from the viewpoint of reducing haze on the silicon wafer surface, the average number of moles of oxyethylene added in the polyoxyethylene-added nonionic surfactant is preferably 13 or less, and 10 or less (for example, 6 or less). ). When the average number of moles of oxyethylene added to the polyoxyethylene-added nonionic surfactant is 13 or less, there is a sufficient effect of suppressing roughness on the silicon wafer surface, and haze on the silicon wafer surface is reduced.

In one embodiment of the present invention, in order to further reduce the haze on the silicon wafer surface, the average number of moles of oxyethylene added in the polyoxyethylene-added nonionic surfactant is preferably 2 or more, more preferably It is 4 or more. When the average number of moles of oxyethylene added to the polyoxyethylene-added nonionic surfactant is 2 or more, more specifically, when it is 4 or more, the haze on the surface of the silicon wafer is well reduced.

In one embodiment of the present invention, the polyoxyethylene-added nonionic surfactant includes an alkyl moiety in its structure, and the number of carbon atoms in the alkyl moiety is preferably 3 or more, and preferably 8 or more. It is more preferable that there be. Further, the number of carbon atoms in the alkyl moiety is preferably 80 or less, more preferably 18 or less, even more preferably 16 or less, and may be 11 or less (for example, 10 or less). This embodiment has the technical effect of improving the effect of reducing haze.

In one embodiment of the present invention, the polyoxyethylene-added nonionic surfactant includes polyoxyethylene alkyl ether, polyoxyethylene phenyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkyl Examples include amide, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene castor oil, and polyoxyethylene rosin ester.

The polyoxyethylene-added nonionic surfactants may be used alone or in combination of two or more. Specific examples of polyoxyethylene-added nonionic surfactants include polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, and polyoxyethylene-2. - Ethylhexyl ether, polyoxyethylene nonyl ether, polyoxyethylene decyl ether, polyoxyethylene isodecyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxy Ethylene isostearyl ether, polyoxyethylene oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene lauryl Amine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene stearylamide, polyoxyethylene oleylamide, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene Monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopaltimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene trioleate Sorbitan, polyoxyethylene sorbitol tetraoleate, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, etc. can be used.

In one embodiment of the present invention, the polyoxyalkylene nonionic surfactant is a block polyether nonionic surfactant. The ratio of EO and PO in the block type polyether nonionic surfactant is preferably adjusted to a range suitable for polishing the surface of a silicon wafer. The sum of a and c in the general formula (2) is preferably 5 to 500, more preferably 10 to 200. Furthermore, b in the general formula (2) is preferably from 2 to 200, more preferably from 5 to 100, even more preferably from 10 to 50.

In one embodiment of the present invention, the ratio of EO and PO in the block type polyether nonionic surfactant is preferably EO:PO = 30:70 to 95:5, and EO:PO = 70:30. ˜90:10 is more preferable.

The block type polyether nonionic surfactants may be used alone or in combination of two or more. As the block type polyether nonionic surfactant, polyoxyethylene polyoxypropylene glycol can be used.

In this embodiment, the weight average molecular weight of the two or more surfactants is 4,000 or less. That is, the weight average molecular weight of the largest surfactant among the two or more surfactants is 4,000 or less. Therefore, according to one embodiment of the present invention, the weight average molecular weight of the two or more surfactants is smaller than any of the weight average molecular weights of the one or more water-soluble polymers described above.

In one embodiment of the present invention, the weight average molecular weight of the polypropylene glycol compound is preferably 200 or more, more preferably 250 or more, even more preferably 300 or more, and 350 or more (for example, 400 or more). (above) may be possible. According to this embodiment, the intended effects of the present invention can be efficiently achieved. According to one embodiment of the present invention, the weight average molecular weight of the polypropylene glycol compound is preferably 4,000 or less, more preferably 3,500 or less, and preferably 3,000 or less. More preferably, it may be 2,500 or less (for example, 2,000 or less). According to this embodiment, the solubility of the polypropylene glycol compound is improved, and the desired effects of the present invention can be efficiently achieved.

In one embodiment of the present invention, from the viewpoint of reducing haze on the silicon wafer surface, the weight average molecular weight of the polyoxyalkylene nonionic surfactant is preferably 4,000 or less, more preferably 3,800 or less. , more preferably 1,400 or less (for example, 1,200 or less). When this weight average molecular weight is 1,400 or less, a sufficient effect of suppressing roughness on the silicon wafer surface can be obtained, and haze on the silicon wafer surface can be sufficiently reduced. In order to obtain a better effect of suppressing roughness on the surface of a silicon wafer, the weight average molecular weight of the polyoxyalkylene nonionic surfactant is preferably greater than 200, more preferably 300 or more. When this weight average molecular weight is larger than 200, more specifically, when it is 300 or more, 500 or more, or 800 or more, a sufficient effect of suppressing roughness on the surface of the silicon wafer can be obtained.

In one embodiment of the present invention, when the polishing composition is in the form of a concentrated liquid, the content of the surfactant in the polishing composition is 0.0001% by mass from the viewpoint of improving the haze reduction effect. It is preferably at least 0.0005% by mass, more preferably at least 0.001% by mass, and even more preferably at least 0.001% by mass. In one embodiment of the present invention, when the polishing composition is in the form of a concentrated liquid, the content of the surfactant in the polishing composition is 1.0 from the viewpoint of suppressing foaming of the polishing composition. It is preferably at most 0.5% by mass, more preferably at most 0.2% by mass, and even more preferably at most 0.2% by mass.

In one embodiment of the present invention, when the polishing composition is in a diluted state, the content of the surfactant is preferably 0.00001% by mass or more from the viewpoint of improving the haze reduction effect. , more preferably 0.00005% by mass or more, and even more preferably 0.0001% by mass or more. Further, in one embodiment of the present invention, when the polishing composition is in a diluted state, the content of surfactant in the polishing composition is 0.02% by mass or less from the viewpoint of maintaining the polishing rate. It is preferably 0.01% by mass or less, more preferably 0.005% by mass or less, and even more preferably 0.005% by mass or less. In addition, in the above, the content of surfactant refers to the total amount of two or more types of surfactants.

In one embodiment of the present invention, when the polishing composition is in the form of a concentrated solution, the content of the polypropylene glycol compound in the polishing composition is 0.00001 mass from the viewpoint of improving the haze reduction effect. % or more, more preferably 0.0001% by mass or more, even more preferably 0.0002% by mass or more, and particularly preferably 0.001% by mass or more. In one embodiment of the present invention, when the polishing composition is in the form of a concentrate, the content of the polypropylene glycol compound in the polishing composition is 0.03% by mass or less from the viewpoint of dispersion stability. It is preferably present, more preferably 0.02% by mass or less, and even more preferably 0.015% by mass or less.

In one embodiment of the present invention, when the polishing composition is in a diluted state, the content of the polypropylene glycol compound is preferably 0.000001% by mass or more from the viewpoint of improving the haze reduction effect. It is preferably 0.00001% by mass or more, more preferably 0.00005% by mass or more, and particularly preferably 0.0001% by mass or more. Further, in one embodiment of the present invention, when the polishing composition is in a diluted state, the content of the polypropylene glycol compound in the polishing composition is 0.01% from the viewpoint of preventing a decrease in the polishing rate. It is preferably at most 0.002% by mass, even more preferably at most 0.001% by mass, and particularly preferably at most 0.0006% by mass. In addition, in the above, when the polishing composition contains two or more kinds of polypropylene glycol compounds, the content of the polypropylene glycol compound refers to the total amount thereof.

In one embodiment of the present invention, when the polishing composition is in a concentrated liquid state, the content of the polyoxyalkylene nonionic surfactant in the polishing composition is determined from the viewpoint of improving the haze reduction effect. , preferably 0.0001% by mass or more, more preferably 0.0005% by mass or more, and even more preferably 0.001% by mass or more. In one embodiment of the present invention, when the polishing composition is in the form of a concentrate, the content of the polyoxyalkylene nonionic surfactant in the polishing composition suppresses foaming of the polishing composition. From this viewpoint, the content is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less.

In one embodiment of the present invention, when the polishing composition is in a diluted state, the content of the polyoxyalkylene nonionic surfactant is 0.00001 mass from the viewpoint of improving the haze reduction effect. % or more, more preferably 0.00005% by mass or more, and still more preferably 0.0001% by mass or more. In one embodiment of the present invention, when the polishing composition is in a diluted state, the content of the polyoxyalkylene nonionic surfactant in the polishing composition is determined from the viewpoint of maintaining the polishing rate. It is preferably 0.02% by mass or less, more preferably 0.01% by mass or less, and even more preferably 0.005% by mass or less.

In one embodiment of the present invention, the content of the polypropylene glycol compound relative to the content of the polyoxyalkylene nonionic surfactant is typically 4.0 or less. When the content of the polypropylene glycol compound relative to the content of the polyoxyalkylene nonionic surfactant exceeds 4.0, the intended effects of the present invention tend not to be achieved. In one embodiment of the present invention, the content of the polypropylene glycol compound relative to the content of the polyoxyalkylene nonionic surfactant is preferably 3.5 or less, and preferably 3.0 or less. is more preferable, more preferably 2.5 or less, and may be 2.1 or less (for example, 1.8 or less). In such embodiments, the intended effects of the present invention become significant.

In one embodiment of the present invention, the content of the polypropylene glycol compound relative to the content of the polyoxyalkylene nonionic surfactant is preferably 0.01 or more, and preferably 0.05 or more. is more preferable, and may be 0.1 or more (for example, 0.3 or more). According to this embodiment, there is a technical effect of reducing haze.

(abrasive grain)
The polishing composition disclosed herein may or may not contain abrasive grains. In one embodiment of the present invention, the polishing composition includes abrasive grains. Abrasive grains have the function of mechanically polishing the surface of the object to be polished.

The material and properties of the abrasive grains are not particularly limited, and can be appropriately selected depending on the purpose and manner of use of the polishing composition. Moreover, one kind of abrasive grains may be used alone, or two or more kinds of abrasive grains may be used in combination. Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of inorganic particles include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, red iron particles; Examples include nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. Specific examples of the organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles, polyacrylonitrile particles, and the like. Here, (meth)acrylic acid refers comprehensively to acrylic acid and methacrylic acid.

As the abrasive grains, inorganic particles are preferable, and particles made of metal or metalloid oxides are particularly preferable. Particularly preferred abrasive grains include silica particles. Examples of the silica particles include colloidal silica, fumed silica, and precipitated silica.

Among silica particles, colloidal silica and fumed silica are preferred, and colloidal silica is particularly preferred from the viewpoint of reducing scratches. That is, it is preferable that the abrasive grains contain colloidal silica.

The average primary particle diameter of the abrasive grains in the polishing composition used in the final polishing step is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 15 nm or more, and particularly preferably It is 20 nm or more. Further, the average primary particle diameter of the abrasive grains used in the final polishing step is preferably 60 nm or less, more preferably 50 nm or less, and still more preferably 40 nm or less.
The average secondary particle diameter of the abrasive grains in the polishing composition used in the final polishing step is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 25 nm or more, and even more preferably 40 nm or more. It is particularly preferable that Further, the average secondary particle diameter of the abrasive grains used in the final polishing step is preferably 150 nm or less, more preferably 120 nm or less, even more preferably 100 nm or less, and particularly preferably 60 nm or less.

Note that the value of the average primary particle diameter of the abrasive grains can be measured by the method described in Examples. Further, the average secondary particle diameter of the abrasive grains is measured, for example, by a dynamic light scattering method, and can be measured using, for example, "Nanotrack (registered trademark) UPA-UT151" manufactured by Nikkiso Co., Ltd.

At this time, the polishing rate for the surface of the object to be polished tends to improve as the content of abrasive grains increases. On the other hand, a decrease in the content of abrasive grains tends to improve the dispersion stability of the polishing composition and reduce the amount of abrasive grain residue on the polished surface.

In one embodiment of the present invention, when the polishing composition disclosed herein contains abrasive grains, when the polishing composition is in the form of a concentrate, the content of the abrasive grains in the polishing composition (2 The total amount (if more than one species is used) is not particularly limited, but is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and 0.1% by mass or more. is more preferable, and particularly preferably 1% by mass or more. Further, the content of abrasive grains in the polishing composition is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less. The content of abrasive grains when the polishing liquid is in a diluted state is not particularly limited, but is typically 0.001% by weight or more, preferably 0.005% by weight or more, and more preferably It is 0.01% by weight or more, for example 0.15% by weight or more. Higher polishing rates can be achieved by increasing the abrasive content. From the viewpoint of realizing a surface with lower haze, the above content is usually suitably 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, still more preferably 2% by weight or less, For example, it is 1% by weight or less, may be 0.7% by weight or less, and may be 0.4% by weight or less.

In addition, the preferable adjustment of the content of abrasive grains when used as the above-mentioned polishing liquid is to mix the concentrated liquid of the polishing composition described above with a dispersion medium such as water, or a solution or dispersion containing an arbitrary polishing aid therein. It is preferable to perform this by diluting with a liquid or the like.

When the polishing composition disclosed herein contains abrasive grains, in one embodiment of the present invention, the above-mentioned water-soluble polymer and the above-mentioned surfactant are added to 100 g of abrasive grains in the polishing composition of the present invention. The total mass of the agent is preferably 2 g or more, more preferably 3 g or more, and even more preferably 4 g or more. This embodiment has the technical effect of improving the effect of reducing haze. In one embodiment of the present invention, in the polishing composition of the present invention, the total mass of the above-mentioned water-soluble polymer and the above-mentioned surfactant per 100 g of abrasive grains is preferably 10 g or less, and 8 g or less. It is more preferable that the amount is 7 g or less (for example, 6 g or less). Such an embodiment has the technical effect of maintaining the polishing rate.

(basic compound)
In one embodiment of the present invention, the polishing composition contains a basic compound. Here, the basic compound refers to a compound having the function of increasing the pH of the polishing composition by being added to the polishing composition. The basic compound has the function of chemically polishing the surface of the object to be polished by etching, and the function of improving the dispersion stability of the abrasive grains. Moreover, a basic compound can be used as a pH adjuster.

A preferred basic compound can be selected depending on its expected function. Moreover, one type of basic compound may be used alone, or two or more types may be used in combination.

Specific examples of the basic compound include hydroxides or salts of Group 2 elements or alkali metals, quaternary ammonium compounds, ammonia or salts thereof, amines, and the like.

In the hydroxide or salt of a Group 2 element or an alkali metal, the Group 2 element is not particularly limited, but alkaline earth metals can be preferably used, such as calcium. Further, examples of the alkali metal include potassium and sodium. Examples of salts include carbonates, hydrogen carbonates, sulfates, acetates, and the like. Examples of hydroxides or salts of Group 2 elements or alkali metals include calcium hydroxide, potassium hydroxide, potassium carbonate, potassium hydrogen carbonate, potassium sulfate, potassium acetate, potassium chloride, sodium hydroxide, sodium hydrogen carbonate, and sodium carbonate.

Examples of the quaternary ammonium compound include hydroxides such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium, and salts such as chlorides, carbonates, bicarbonates, sulfates, and phosphates. Specific examples include tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; tetraalkylammonium carbonates such as tetramethylammonium carbonate, tetraethylammonium carbonate, and tetrabutylammonium carbonate; chloride; Examples include tetraalkylammonium chlorides such as tetramethylammonium, tetraethylammonium chloride, and tetrabutylammonium chloride. Other ammonium salts include ammonium carbonate, ammonium hydrogen carbonate, and the like.

Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine. , piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, guanidine, and the like.

In one embodiment of the present invention, when the polishing composition of the present invention is in the form of a concentrated liquid, the content of basic compounds in the polishing composition (if two or more types are used, the total amount) is 0. It is preferably .002% by mass or more, and more preferably 0.02% by mass or more. By increasing the content of the basic compound, it becomes easier to obtain a high polishing rate. Further, in this case, the content of the basic compound in the polishing composition (the total amount when two or more types are used) is preferably 10% by mass or less from the viewpoint of storage stability, filterability, etc. It is more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less.

In one embodiment of the present invention, when the polishing composition of the present invention is in the form of a diluted solution, the content of the basic compound in the polishing composition (or the total amount when two or more types are used) is particularly Although not limited, it is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, and even more preferably 0.002% by mass or more. Further, the content of the basic compound (the total amount when two or more types are used) in the polishing composition of the present invention is preferably 5% by mass or less from the viewpoint of storage stability, filterability, etc. It is more preferably 2% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less.

(Dispersion medium)
In one embodiment of the invention, the polishing composition includes a dispersion medium (particularly water). Water functions as a solvent for dissolving other components or a dispersion medium for dispersing them.

From the viewpoint of preventing contamination of the silicon wafer and inhibiting the effects of other components, it is preferable that the water contains as few impurities as possible. As such water, for example, water in which the total content of transition metal ions is 100 ppb or less is preferable. Here, the purity of water can be increased by, for example, removing impurity ions using an ion exchange resin, removing foreign substances using a filter, distilling, or the like. Specifically, as water, it is preferable to use, for example, deionized water (ion-exchanged water), pure water, ultrapure water, distilled water, or the like.

The dispersion medium may be a mixed solvent of water and an organic solvent for dispersing or dissolving each component. In this case, examples of the organic solvent used include acetone, acetonitrile, ethanol, methanol, isopropanol, glycerin, ethylene glycol, propylene glycol, etc., which are organic solvents that are miscible with water. Alternatively, these organic solvents may be used without being mixed with water, and each component may be dispersed or dissolved and then mixed with water. These organic solvents can be used alone or in combination of two or more. Here, it is preferable that the dispersion medium is only water.

[Form of polishing composition, etc.]
In one embodiment of the present invention, the polishing composition may be a one-component type or a multi-component type such as a two-component type. The multi-liquid type is a combination of liquids in which part or all of the polishing composition is mixed at an arbitrary mixing ratio.

In one embodiment of the present invention, the polishing composition may be used for polishing as it is, or may be used after diluting the polishing composition in the form of a concentrated solution. The dilution ratio at this time is not particularly limited, but for example, it is preferably 2 times or more and 140 times or less on a volume basis, more preferably 5 times or more and 50 times or less, and 10 times or more and 40 times or less. More preferred. The dilution method is not particularly limited, and examples include a method of diluting by adding a dispersion medium such as water. In the case of a multi-component polishing composition, a method of diluting it with water and an aqueous solution containing some of the constituent components may be used. For example, after storing and/or transporting a concentrated solution of the polishing composition, the polishing composition can be prepared by diluting it at the time of use. That is, the concept of the polishing composition in the technology disclosed herein includes a polishing liquid (working slurry) that is supplied to an object to be polished and used for polishing the object, and a polishing liquid that is diluted and used as a polishing liquid. This includes both concentrated liquid (undiluted solution of polishing liquid) and concentrated liquid (undiluted solution of polishing liquid).

In one embodiment of the present invention, the polishing composition (diluted solution or concentrated solution) is preferably alkaline, and its pH is preferably 8 or higher, more preferably 8.5 or higher. , more preferably 9.0 or more, particularly preferably 9.2 or more. As the pH of the polishing composition increases, the polishing rate tends to improve. On the other hand, from the viewpoint of preventing dissolution of abrasive grains (for example, silica particles) and suppressing a decrease in mechanical polishing action, the pH of the polishing composition (diluted solution or concentrated solution) is preferably 12 or less, and 11 It is more preferably .5 or less, even more preferably 11.0 or less, and particularly preferably 10.5 or less. To adjust the pH of the polishing composition, a known pH adjuster or the above basic compound may be used.

Note that the pH of the polishing composition (diluted solution or concentrated solution) can be measured using a pH meter. After three-point calibration of the pH meter using standard buffers, the glass electrode is placed in the polishing composition. The pH of the polishing composition can be determined by measuring the value after it has stabilized for 2 minutes or more. For example, as the pH meter, a pH glass electrode type hydrogen ion concentration indicator (model number F-23) manufactured by Horiba, Ltd. can be used. The standard buffers are (1) Phthalate pH buffer pH: 4.01, (2) Neutral phosphate pH buffer pH: 6.86, (3) Carbonate pH buffer pH: 10.01. can be used. Here, pH is a value at 25°C.

<Method for producing polishing composition>
In one embodiment of the present invention, the polishing composition can be produced by, for example, stirring and mixing each component in water. However, the method is not particularly limited to this method. Further, the mixing temperature and mixing time are not particularly limited.

<Object to be polished>
In one embodiment of the present invention, the object to be polished using the polishing composition is preferably a silicon material. That is, it is preferable that the polishing composition according to one embodiment of the present invention be used for polishing a silicon material. Further, the silicon material preferably includes at least one material selected from the group consisting of silicon single crystal, amorphous silicon, and polysilicon. As the silicon material, silicon single crystal or polysilicon is more preferable, and silicon single crystal is even more preferable, from the viewpoint that the effects of the present invention can be obtained more markedly. That is, the object to be polished is preferably a single crystal silicon substrate.

Furthermore, the shape of the object to be polished is not particularly limited. In one embodiment of the present invention, the polishing composition can be preferably applied to polishing a flat object to be polished, such as a plate or a polyhedron.

<Polishing method>
Another aspect of the present invention provides a polishing method that includes polishing a silicon single crystal surface of a silicon wafer using the polishing composition described above. In one embodiment of the present invention, the polishing composition described above is preferably used in a final polishing step of a silicon single crystal surface of a silicon wafer.

The polishing device is a general-purpose polishing device that is equipped with a holder that holds a substrate, etc. that has the object to be polished, a motor that can change the rotation speed, and a polishing surface plate to which a polishing pad (polishing cloth) can be attached. A polishing device can be used. As the polishing pad, general non-woven fabric type, polyurethane type, suede type, etc. can be used without particular limitation. The polishing pad is preferably grooved so that the polishing composition accumulates therein.
The polishing conditions are appropriately set depending on the stage of the polishing process in which the polishing composition is used.

In the final polishing step, a single-sided polishing device can be suitably used. In the final polishing step, the rotation speed of the surface plate is preferably about 10 rpm or more and 100 rpm or less, more preferably about 20 rpm or more and 50 rpm or less, and even more preferably about 25 rpm or more and 50 rpm or less. With this, haze on the surface of the object to be polished can be significantly reduced.

The object to be polished is usually pressurized by a surface plate. The pressure at this time can be appropriately selected, but in the case of the final polishing step, it is preferably about 5 kPa or more and about 30 kPa or less, and more preferably about 10 kPa or more and about 20 kPa or less. With such a pressure, haze on the surface of the object to be polished can be significantly reduced.

The supply rate of the polishing composition can be appropriately selected depending on the size of the surface plate. Considering economic efficiency, in the case of the final polishing step, the flow rate is preferably about 0.1 L/min or more and 5 L/min or less, more preferably about 0.2 L/min or more and 2 L/min or less. With such a supply rate, the surface of the object to be polished can be efficiently polished and the haze on the surface of the object to be polished can be significantly reduced.

There is no particular limit to the holding temperature of the polishing composition in the polishing device, but from the viewpoint of polishing rate stability and haze reduction, it is preferably about 15°C or more and about 40°C or less, and about 18°C or more and about 25°C or less. is more preferable.

Regarding the above-mentioned polishing conditions (settings of the polishing apparatus), only one example has been described, and the conditions may be outside the above-mentioned range, and the settings may be changed as appropriate. Those skilled in the art can appropriately set such conditions.

According to one embodiment of the present invention, cleaning and drying are preferably performed after polishing. The methods and conditions for these operations are not particularly limited, and known methods may be employed as appropriate. For example, it is preferable to perform SC-1 cleaning as the step of cleaning the object to be polished. "SC-1 cleaning" is a cleaning method performed using, for example, a mixed solution of ammonia and hydrogen peroxide (for example, at a temperature of 40° C. or higher and 80° C. or lower). Particles on the surface of the silicon wafer can be removed by performing SC-1 cleaning and, for example, etching the surface of the silicon wafer thinly.

The present invention will be explained in further detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. In addition, unless otherwise specified, "%" and "parts" mean "mass %" and "mass parts", respectively. In addition, in the following examples, unless otherwise specified, operations were performed under conditions of room temperature (25° C.)/relative humidity 40 to 50% RH.

<Preliminary polishing>
As a wafer seed, a p-type COP (Crystal Organized Particle)-free silicon wafer with a crystal orientation of <100> and a size of 200 mm was prepared. Here, COP refers to a concave defect formed on the surface of a silicon wafer, and is a crystal defect of the single crystal silicon forming the silicon wafer or a scratch exceeding a certain width and depth caused by an abrasive (abrasive grain). (Scratch).

The silicon wafer described above was polished under the following preliminary polishing conditions.

(Preliminary polishing conditions)
Polishing equipment: Single-fed polishing machine manufactured by Okamoto Machine Tool Co., Ltd., model "PNX-322"
Polishing load: 15kPa
Surface plate rotation speed: 30 rpm
Carrier rotation speed: 30rpm
Polishing pad: Manufactured by Fujibo Ehime, product name “FP55”
Polishing composition supply rate: 0.6L/min
Temperature of polishing composition: 20°C
Surface plate cooling water temperature: 20℃
Polishing time: 3 minutes Polishing composition for preliminary polishing: 0.9% by mass of colloidal silica (average primary particle size 35 nm), 0.06% by mass of KOH, dispersion medium: water.

<Final polishing>
The silicon wafer polished in the preliminary polishing described above was polished under the following final polishing conditions.

(Conditions for final polishing)
Polishing equipment: Single-fed polishing machine manufactured by Okamoto Machine Tool Co., Ltd., model "PNX-322"
Polishing load: 15kPa
Surface plate rotation speed: 30 rpm
Carrier rotation speed: 30rpm
Polishing pad: Manufactured by Fujibo Ehime Co., Ltd. Product name: “POLYPAS27NX”
Polishing composition supply rate: 0.4L/min
Temperature of polishing composition: 20°C
Surface plate cooling water temperature: 20℃
Polishing time: 4 minutes Polishing composition for final polishing: Each polishing composition described in the following Examples and Comparative Examples.

<One type of water-soluble polymer>
(Polishing compositions of Examples 1 to 5 and Comparative Examples 1 to 7)
Polishing compositions of Examples 1 to 5 and Comparative Examples 1 to 7 were prepared by mixing the following components to have the following compositions.

Abrasive grains: 0.18% by mass of colloidal silica with an average primary particle diameter of 25 nm,
Basic compound: NH3 0.005% by mass,
Dispersion medium: water,
Details of the water-soluble polymer and surfactants (1) and (2) are as shown in Table 1 below.

The silicon wafer polished by the above final polishing was cleaned under the following cleaning conditions.

<Cleaning conditions>
Cleaning was performed using a cleaning solution of NH ₄ OH (29%): H ₂ O ₂ (31%): deionized water (DIW) = 1:1:12 (volume ratio) (SC-1 cleaning). Two cleaning tanks were prepared, the first and second cleaning tanks contained the above cleaning liquid and were maintained at 60°C, the polished silicon wafer was immersed in the first cleaning tank for 5 minutes, and then After passing through a rinsing tank using ultrapure water and ultrasonic waves, it was immersed in a second cleaning tank for 5 minutes and then dried using a spin dryer.

After drying, the following haze measurement was performed.

<Haze measurement>
Haze (ppm) was measured in DWO mode using KLA-Tencor's "SURFSCAN SP2 Evaluation was made using a relative value with the product without PPG set as 100.
<Method for measuring average primary particle diameter>
The average primary particle diameter of the abrasive grains was calculated from the specific surface area of colloidal silica measured by the BET method using "Flow SorbII 2300" manufactured by Micromeritex and the density of the abrasive grains.

<Measurement of weight average molecular weight>
The weight average molecular weights of the water-soluble polymer and surfactant were measured using the GPC method under the following conditions.

≪GPC measurement conditions≫
Measuring device: HLC-8320GPC (Tosoh)
Sample concentration: 0.1% by weight
Column: TSKgel GMPWXL
Detector: Differential refractometer Eluent: 100mM sodium nitrate aqueous solution/acetonitrile = 10-8/0-2
Flow rate: 1 mL/min Measurement temperature: 40°C
Molecular weight conversion: Polyethylene glycol conversion Sample injection volume: 200 μL.

<Two types of water-soluble polymer>
(Polishing compositions of Examples 6 to 9 and Comparative Example 8)
Polishing compositions of Examples 6 to 9 and Comparative Example 8 were prepared by mixing the following components to have the following compositions.

Abrasive grains: 0.17% by mass of colloidal silica with an average primary particle diameter of 25 nm,
Basic compound: NH3 0.011% by mass,
Water-soluble polymers: 0.005% by mass of acetalized modified PVA (weight average molecular weight = 13,000) and 0.0038% by mass of polyN-acryloylmorpholine (PACMO) (weight average molecular weight = 350,000). a mixture of
Details of surfactants (1) and (2) are as shown in Table 2 below.

As shown in Table 1, Examples 1 to 5 containing both surfactant (1) and surfactant (2) are comparative examples containing neither surfactant (1) nor surfactant (2). Haze was reduced compared to 1 to 7. It can be seen that this effect can be similarly obtained even if the molecular weight of surfactant (1) is changed. It is believed that in these Examples, two or more types of surfactants worked dominantly to protect the wafer and contributed to the reduction of haze.

As shown in Table 2, even in Examples 6 to 9 in which the content of surfactant (1) was varied, the haze was reduced compared to Comparative Example 8, which did not contain surfactant (1). Also, when the content of surfactant (1) was changed as shown in Table 2, a significant haze reduction effect was observed compared to Comparative Example 8. It has been confirmed that if the content of surfactant (1) is too high, it is difficult to obtain the effects of the present application.

Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The techniques described in the claims include various modifications and changes to the specific examples illustrated above.

Claims (11)

one or more water-soluble polymers,
two or more surfactants;
including;
A polishing composition for silicon wafers, wherein one or more of the two or more surfactants is a polypropylene glycol compound (excluding polyoxypropylene methyl glucoside) . The polishing composition for silicon wafers according to claim 1, wherein each of the weight average molecular weights of the one or more water-soluble polymers is larger than any of the weight average molecular weights of the two or more surfactants. The polishing composition for silicon wafers according to claim 2, wherein each of the one or more water-soluble polymers has a weight average molecular weight of 5,000 or more. The polishing composition for silicon wafers according to any one of claims 1 to 3, wherein the polypropylene glycol compound has a weight average molecular weight of 4,000 or less. The polishing composition for silicon wafers according to any one of claims 1 to 4, wherein the water-soluble polymer contains a hydroxyl group or a nitrogen atom. The polishing for silicon wafers according to claim 5, wherein the water-soluble polymer is one or more selected from the group consisting of a polymer having a structural unit derived from vinyl alcohol, a cellulose derivative, and polyN-acryloylmorpholine. Composition for use. The polishing composition for silicon wafers according to any one of claims 1 to 6, wherein one or more of the two or more surfactants is a polyoxyalkylene nonionic surfactant. The polishing composition for silicon wafers according to claim 7, wherein the polyoxyalkylene nonionic surfactant has a weight average molecular weight of 4,000 or less. The polishing composition for silicon wafers according to claim 7 or 8, wherein the polyoxyalkylene nonionic surfactant has an average added mole number of oxyethylene of 13 or less. For polishing silicon wafers according to any one of claims 7 to 9, wherein the content of the polypropylene glycol compound relative to the content of the polyoxyalkylene nonionic surfactant is 4.0 or less. Composition. A method for polishing a silicon single crystal surface of a silicon wafer, the polishing method comprising polishing using the polishing composition according to any one of claims 1 to 10.