Polishing composition

Abstract

Provided is a polishing composition capable of improving the surface quality of a silicon wafer following polishing. Provided is a polishing composition used for polishing a silicon wafer. The polishing composition includes abrasive grains, a water-soluble polymer PA, a basic compound, and water. The water-soluble polymer PA is a polymer containing a structural unit A derived from 2-acrylamido-2-methylpropanesulfonic acid.

Description

polishing composition

[0001] The present invention relates to a polishing composition. This application claims priority to Japanese Patent Application No. 2024-57665, filed on March 29, 2024, the entire contents of which are incorporated herein by reference.

[0002] Precision polishing using a polishing composition is performed on the surfaces of materials such as metals, semi-metals, non-metals, and their oxides. For example, the surface of a silicon wafer used as a component of a semiconductor device is generally finished to a high-quality mirror surface through a lapping step (rough polishing step) and a polishing step (precise polishing step). The polishing step typically includes a pre-polishing step (preliminary polishing step) and a finish polishing step (final polishing step). Patent documents 1 to 3 are cited as technical documents related to polishing compositions primarily used for polishing semiconductor substrates such as silicon wafers.

[0003] Japanese Patent No. 6185432 Japanese Patent No. 6348927 Japanese Patent No. 6232243

[0004] Polishing compositions used in polishing silicon wafers (particularly in the finish polishing step) are required to have the ability to achieve a high-quality surface after polishing. Many polishing compositions for such applications contain, in addition to abrasive grains and water, a water-soluble polymer for purposes such as protecting the wafer surface and improving wettability. For example, Patent Documents 1 to 3 disclose polishing compositions containing silica particles, a basic compound, and a water-soluble polymer. However, conventional techniques still have room for improvement in terms of reducing post-polishing haze and defects (e.g., LPD-N (Light Point Defect Non-cleanable)) and improving surface quality.

[0005] Therefore, an object of the present invention is to provide a polishing composition that can improve the surface quality of polished silicon wafers.

[0006] According to the present specification, there is provided a polishing composition for use in polishing silicon wafers. The polishing composition comprises abrasive grains and a water-soluble polymer P.Ａ The water-soluble polymer P contains a basic compound and water. Ａ is a polymer containing a structural unit A derived from 2-acrylamido-2-methylpropanesulfonic acid (AMPS). Ａ This action adjusts the frequency of contact between the abrasive grains and the silicon wafer, thereby improving the surface quality of the polished silicon wafer. For example, it is possible to reduce defects (LPD-N) while suppressing an increase in haze.

[0007] In some embodiments, the polishing composition disclosed herein contains silica particles as abrasives. By using silica particles as abrasives, the effects of the technology disclosed herein can be preferably realized.

[0008] In some embodiments, the polishing composition disclosed herein comprises the water-soluble polymer P Ａ The water-soluble polymer P further contains a water-soluble polymer different from Ａ In addition, a polishing composition containing the water-soluble polymer P is likely to produce a polished surface of higher quality. Ａ The present invention can be preferably carried out in an embodiment in which a silicon wafer is polished using a polishing composition containing in combination at least one other water-soluble polymer.

[0009] In some preferred embodiments, the polishing composition disclosed herein comprises the water-soluble polymer P Ａ The polishing agent further contains two or more types of water-soluble polymers different from the above. By further containing two or more types of water-soluble polymers, a polished surface of higher quality is likely to be obtained.

[0010] In some preferred embodiments of the polishing composition disclosed herein, the water-soluble polymer P Ａ is a copolymer containing the structural unit A and a structural unit B that is substantially not anionic (hereinafter, sometimes abbreviated as "non-anionic structural unit B"). Ａ By using the above, the effects of the technology disclosed herein can be preferably realized.

[0011] In some embodiments, the water-soluble polymer P Ａ is a block copolymer. Ａ By using a block copolymer as the polymer, the effects of the technology disclosed herein can be preferably realized.

[0012] In some embodiments, the water-soluble polymer P Ａ The present invention relates to a water-soluble polymer P having a non-anionic structural unit B derived from at least one monomer selected from the group consisting of a nitrogen atom-containing monomer, a vinyl alcohol-based monomer, an allyl alcohol-based monomer, a butylene-based monomer, an aromatic vinyl-based monomer, an acrylic acid ester-based monomer, and an ethylene glycol-based monomer, as the structural unit B. Ａ This can be preferably carried out in an embodiment using the following.

[0013] The polishing composition disclosed herein can further contain a surfactant. Such a polishing composition is likely to produce a polished surface of higher quality. In some embodiments, a nonionic surfactant can be preferably used as the surfactant, from the viewpoint of suitably achieving the effects of the technology disclosed herein.

[0014] Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.

[0015] In this specification, "weight" may be read as "mass." For example, "wt%" may be read as "mass%," and "parts by weight" may be read as "parts by mass." In this specification, the concept of a polymer includes both homopolymers and copolymers.

[0016] <Abrasive Grains> The polishing composition disclosed herein contains abrasive grains. The abrasive grains function to mechanically polish the surface of the silicon wafer. The material and properties of the abrasive grains are not particularly limited and can be appropriately selected depending on the purpose and usage of the polishing composition. 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, and red iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; and the like. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles (here, (meth)acrylic acid refers collectively to acrylic acid and methacrylic acid), polyacrylonitrile particles, and the like. Such abrasive grains may be used alone or in combination of two or more kinds.

[0017] The abrasive grains are preferably inorganic particles, particularly particles made of metal or semi-metal oxides, with silica particles being particularly preferred. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which the abrasive grains are essentially made of silica particles. Here, "substantially" means that 95% by weight or more (preferably 98% by weight or more, more preferably 99% by weight or more, and even 100% by weight) of the particles constituting the abrasive grains are silica particles.

[0018] Specific examples of silica particles include colloidal silica, fumed silica, precipitated silica, etc. Silica particles can be used alone or in combination of two or more types. Colloidal silica is particularly preferred because it is easy to obtain a polished surface with excellent surface quality after polishing. As colloidal silica, for example, colloidal silica produced by ion exchange using water glass (sodium silicate) as a raw material, or alkoxide-method colloidal silica (colloidal silica produced by the hydrolysis and condensation reaction of alkoxysilane) can be preferably used. Colloidal silica can be used alone or in combination of two or more types.

[0019] The true specific gravity of the abrasive grain constituent material (e.g., silica constituting silica particles) is preferably 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. There is no particular upper limit to the true specific gravity of silica, but it is typically 2.3 or less, preferably 2.2 or less, more preferably 2.0 or less, for example, 1.9 or less. The true specific gravity of the abrasive grain (e.g., silica particles) can be measured by a liquid displacement method using ethanol as the displacement liquid.

[0020] The average primary particle size of the abrasive grains (typically silica particles) is not particularly limited, but from the viewpoint of polishing efficiency, etc., it is, for example, appropriate to be 5 nm or more, advantageously 10 nm or more, preferably 15 nm or more, and more preferably 20 nm or more (for example, more than 20 nm).In addition, from the viewpoint of realizing a higher quality polished surface, the average primary particle size of the abrasive grains is, for example, appropriate to be 100 nm or less, preferably 50 nm or less, more preferably 45 nm or less.In the viewpoint of easily obtaining a lower haze surface, in some embodiments, the average primary particle size of the abrasive grains may be 43 nm or less, may be less than 40 nm, may be less than 38 nm, may be less than 35 nm, may be less than 32 nm, or may be less than 30 nm.

[0021] In this specification, the average primary particle diameter is calculated from the specific surface area (BET value) measured by the BET method by the following formula: average primary particle diameter (nm) = 6000 / (true density (g / cm ３ ) × BET value (m ２The specific surface area is the particle size (BET particle size) calculated by the formula: (1 / g / 2) / (2 / g). The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300."

[0022] The average secondary particle diameter of the abrasive grains (e.g., silica particles) is not particularly limited and can be appropriately selected, for example, from a range of about 15 nm to 300 nm. In some embodiments, from the viewpoint of polishing efficiency and the like, the average secondary particle diameter is preferably 30 nm or more, more preferably 35 nm or more, and may be 40 nm or more, 42 nm or more, or even 44 nm or more. Furthermore, the average secondary particle diameter is usually advantageously 250 nm or less, preferably 200 nm or less, and more preferably 150 nm or less. In some preferred embodiments, the average secondary particle diameter is, for example, 120 nm or less, more preferably 100 nm or less, even more preferably 70 nm or less, and may be 60 nm or less, or may be 50 nm or less.

[0023] In this specification, the average secondary particle size refers to the particle size (volume average particle size) measured by dynamic light scattering. The average secondary particle size of the abrasive grains can be measured by dynamic light scattering using, for example, "Nanotrac (registered trademark) UPA-UT151" manufactured by Nikkiso Co., Ltd.

[0024] The shape (external shape) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical particles include peanut-shaped (i.e., peanut shell-shaped), cocoon-shaped, confetti-shaped, and rugby ball-shaped. For example, abrasive grains in which most of the particles are peanut-shaped or cocoon-shaped can be preferably used.

[0025] Although not particularly limited, the average value of the ratio of the major axis to the minor axis of the abrasive grains (average aspect ratio) is, in principle, 1.0 or more, preferably 1.05 or more, and more preferably 1.1 or more. By increasing the average aspect ratio, higher polishing efficiency can be achieved. Furthermore, from the viewpoint of improving surface quality, the average aspect ratio of the abrasive grains is preferably 3.0 or less, more preferably 2.0 or less, and even more preferably 1.5 or less.

[0026] The shape (outline) and average aspect ratio of abrasive grains can be determined, for example, by electron microscope observation. A specific procedure for determining the average aspect ratio involves, for example, using a scanning electron microscope (SEM), drawing the smallest rectangle circumscribing each particle image for a predetermined number (e.g., 200) of abrasive grains whose individual particle shapes can be recognized. Then, for each rectangle drawn for each particle image, the long side length (long diameter value) is divided by the short side length (short diameter value) to calculate the long diameter / short diameter ratio (aspect ratio). The average aspect ratio can be determined by arithmetically averaging the aspect ratios of the predetermined number of particles.

[0027] <Water-soluble polymer P Ａ The polishing composition disclosed herein comprises a water-soluble polymer P containing a structural unit A derived from 2-acrylamido-2-methylpropanesulfonic acid (AMPS). Ａ The water-soluble polymer P Ａ A polishing composition containing the water-soluble polymer P can prevent excessive contact between abrasive grains and a silicon wafer during polishing, thereby improving the surface quality of the polished silicon wafer. For example, defects (LPD-N) can be reduced while suppressing an increase in haze. In some preferred embodiments, the water-soluble polymer P Ａ may be a water-soluble copolymer containing a structural unit A derived from AMPS and a structural unit derived from a monomer other than AMPS. The structural unit derived from the monomer other than AMPS may be an ionic (cationic, anionic, or amphoteric) structural unit or a nonionic structural unit.

[0028] In some preferred embodiments, the water-soluble polymer P Ａ The water-soluble polymer P may be a copolymer having a structural unit A derived from AMPS and a non-anionic structural unit B in the same molecule. Ａ When a polishing composition containing the copolymer as above is used, an increase in haze can be further suppressed and LPD-N can be further reduced.

[0029] In this specification, the non-anionic structural unit B "has substantially no anionicity" means that the structural unit B does not exhibit anionicity at pH 12, specifically, is cationic or nonionic. The structural unit B is typically a structural unit derived from a monomer that does not substantially exhibit anionicity, i.e., a monomer that does not exhibit anionicity at pH 12.

[0030] In some embodiments, the water-soluble polymer P Ａ The water-soluble polymer P may contain, as the non-anionic structural unit B, at least a structural unit derived from any one monomer selected from the group consisting of a nitrogen atom-containing monomer, a vinyl alcohol-based monomer, an allyl alcohol-based monomer, a butylene-based monomer, an aromatic vinyl-based monomer, an acrylic acid ester-based monomer, and an ethylene glycol-based monomer. Ａ By using the above, the effects of the polishing composition disclosed herein can be suitably exhibited.

[0031] Examples of nitrogen atom-containing monomers include various N-vinyl monomers and N-(meth)acryloyl monomers exemplified in the description of the water-soluble polymer described below. As in the description of the water-soluble polymer described below, examples of N-vinyl monomers include monomers having a nitrogen-containing heterocycle (e.g., N-vinyl lactam monomers) and N-vinyl linear amides, and examples of N-(meth)acryloyl monomers include linear amides having an N-(meth)acryloyl group and cyclic amides having an N-(meth)acryloyl group. In this specification, the term "(meth)acryloyl group" refers collectively to acryloyl groups and methacryloyl groups. In some embodiments, examples of nitrogen atom-containing monomers include N-acryloylmorpholine (ACMO), N-vinylpyrrolidone (NVP), N-isopropylacrylamide (NIPAM), N,N-diethylacrylamide (DEAM), acrylonitrile, vinylacetamide, and the like. In some preferred embodiments, the nitrogen atom-containing monomer may be ACMO or NIPAM.

[0032] Examples of vinyl alcohol-based monomers include vinyl alcohol, 2-hydroxyethyl vinyl ether, and 4-hydroxybutyl vinyl ether. Examples of allyl alcohol-based monomers include allyl alcohol and methallyl alcohol. Examples of butylene-based monomers include butylene and isobutylene. Examples of aromatic vinyl-based monomers include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, tert-butoxystyrene, vinyltoluene, vinylnaphthalene, and halogenated styrenes. Furthermore, for example, a monomer containing an aromatic vinyl structure and an oxyalkylene structure in one molecule is classified as an aromatic vinyl-based monomer, with the presence of the aromatic vinyl structure being given priority. The number of oxyalkylene repeating units in the oxyalkylene structure (e.g., oxyethylene structure) can be, for example, about 2 to 100. An example of a monomer containing an oxyalkylene structure is vinylbenzyl methoxypolyoxyethylene ether, i.e., an ether of vinylbenzyl alcohol and one-terminated methoxypolyoxyethylene. In the vinylbenzyl methoxypolyoxyethylene ether, the vinyl group can be in the ortho-, meta-, or para-position.Examples of acrylic acid ester monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, ethylhexyl (meth)acrylate, and (meth)acrylate. alkyl (meth)acrylates such as n-decyl (meth)acrylate; alicyclic esters of (meth)acrylic acid such as cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; phenyl (meth)acrylate, (meth) Examples of the ethylene glycol monomer include aromatic (meth)acrylates such as benzyl acrylate, phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and 3-phenoxypropyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 2-ethoxyethyl (meth)acrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; epoxy group-containing (meth)acrylic acid esters such as glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate; and polyoxyalkylene (meth)acrylates such as polyoxyethylene (meth)acrylate and polyoxypropylene (meth)acrylate. Examples of the ethylene glycol monomer include diethylene glycol monovinyl ether.

[0033] The water-soluble polymer P Ａmay be a random copolymer containing the structural unit A and the structural unit B, may be a block copolymer, may be an alternating copolymer, or may be a graft copolymer. Ａ is preferably a random copolymer or a block copolymer, more preferably a block copolymer.

[0034] Water-soluble polymer P Ａ The content ratio of the structural unit A and the structural unit B in the water-soluble polymer P is not particularly limited. Ａ The content ratio (e.g., molar ratio) of the structural unit A and the structural unit B contained in the water-soluble polymer P may be such that the structural unit A is more than the structural unit B, or may be such that the structural unit A is less than the structural unit B, or the content ratio of the structural unit A and the structural unit B may be approximately the same. Ａ According to this embodiment, the structural unit A having a relatively large number of moles contributes to the formation of the water-soluble polymer P Ａ The electrostatic repulsion force due to the water-soluble polymer P contained in the polishing composition acts effectively, and excessive contact between the abrasive grains (typically, silica particles) and the silicon wafer can be efficiently suppressed. Ａ In some other embodiments, the water-soluble polymer P in which the number of moles of structural unit B is greater than the number of moles of structural unit A is more likely to have an effect of improving surface quality. Ａ When the number of moles of the structural unit B is large, the surface protection effect of the structural unit B can advantageously contribute to reducing defects and haze. Ａ The molar ratio (B:A) of the structural unit B to the structural unit A in the water-soluble polymer P may be, for example, 99:1 or less, and from the viewpoint of better exerting the effect of suppressing excessive contact between the abrasive grains and the silicon wafer, it is preferably 95:5 or less, and may be 90:10 or less, 80:20 or less, or 70:30 or less (for example, 60:40 or less or 50:50 or less). ＡIn the above, the lower limit of the molar ratio (B:A) of the structural unit B to the structural unit A is not particularly limited, but in some embodiments, it is suitably 1:99 or more, and may be 10:90 or more. From the viewpoint of adsorptivity to abrasive grains and silicon wafers, in some preferred embodiments, the molar ratio (B:A) is preferably 20:80 or more, may be 30:70 or more, may be 40:60 or more, or may be 50:50 or more.

[0035] In the technology disclosed herein, the water-soluble polymer P Ａ The weight average molecular weight (Mw) of the water-soluble polymer P is not particularly limited. Ａ The Mw of the compound is, for example, approximately 200×10 ４ or less, and may be approximately 150×10 ４ The following is suitable, preferably about 100 x 10 ４ is approximately 50×10 ４ In addition, from the viewpoint of suitably exerting the effects of the technology disclosed herein, the water-soluble polymer P Ａ The Mw of the ４ or more, and may be 0.5 × 10 ４ In some embodiments, the Mw is 1.0×10 or more. ４ The above is appropriate, and 2 x 10 ４ or more, for example, 5×10 ４ The water-soluble polymer P may be Ａ It is advantageous that the Mw is not too small from the viewpoint of the adsorptivity to abrasive grains and silicon wafers, electrostatic repulsion, etc.

[0036] Water-soluble polymer P Ａ The Mw of the polymer can be calculated from the value based on aqueous gel permeation chromatography (GPC) (aqueous, polyethylene oxide equivalent). The same applies to the Mw of the water-soluble polymers and surfactants described below. As the GPC measuring device, it is recommended to use the "HLC-8320GPC" model manufactured by Tosoh Corporation. Measurement can be carried out, for example, under the following conditions. The same method is also used in the examples described below. [GPC measurement conditions] Sample concentration: 0.1 wt% Column: TSKgel GMPWＸＬ Detector: differential refractometer Eluent: 100 mM sodium nitrate aqueous solution Flow rate: 1 mL / min Measurement temperature: 40°C Sample injection volume: 100 μL

[0037] The water-soluble polymer P in the polishing composition disclosed herein Ａ The content of the water-soluble polymer P can be specified in relation to the abrasive grains. Ａ The content of the water-soluble polymer P can be, for example, 0.01 parts by weight or more, and from the viewpoint of reducing defects, etc., it is appropriate to set it to 0.1 parts by weight or more, preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 3 parts by weight or more, and may be, for example, 4 parts by weight or more. Ａ In view of the dispersion stability of the polishing composition, the content of the water-soluble polymer P relative to 100 parts by weight of the abrasive grains may be, for example, 50 parts by weight or less, or 30 parts by weight or less. Ａ The content is suitably 15 parts by weight or less, preferably 10 parts by weight or less, may be 8 parts by weight or less, or may be 7 parts by weight or less.

[0038] Water-soluble polymer P Ａ can be obtained by known methods (specifically, various polymerization methods) or commercially available.

[0039] <Water-soluble polymer> In some embodiments, the polishing composition disclosed herein contains the water-soluble polymer P ＡThe water-soluble polymer may contain one or more water-soluble polymers different from the above. By adsorbing to the abrasive grains or silicon wafer, the water-soluble polymer can be useful for protecting the surface of the silicon wafer and improving the wettability of the silicon wafer surface after polishing. On the other hand, when the water-soluble polymer is adsorbed to the abrasive grains or silicon wafer, the electrostatic repulsion between the silicon wafer and the abrasive grains generally tends to decrease, and this decrease in electrostatic repulsion increases the frequency of contact between the silicon wafer surface and the abrasive grains, which may cancel out part of the effect of improving the surface quality after polishing. According to the technology disclosed herein, the water-soluble polymer and the above water-soluble polymer P Ａ By using a combination of these, even in an embodiment containing the water-soluble polymer, excessive contact between the surface of the silicon wafer and the abrasive grains can be appropriately suppressed, and a higher quality surface can be achieved.

[0040] Examples of water-soluble polymers that can be contained in the polishing composition disclosed herein include compounds containing, in the molecule, 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, or the like. Examples of water-soluble polymers that can be used include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, polyvinyl alcohol polymers, polymers containing nitrogen atoms, and polymers containing (meth)acrylic acid units. As an embodiment of the nitrogen-containing polymer, an N-vinyl type polymer, an N-(meth)acryloyl type polymer, or the like can be used. The water-soluble polymer may be a polymer derived from a natural product, or a synthetic polymer.

[0041] In some embodiments, a polyvinyl alcohol-based polymer may be used as the water-soluble polymer. In this specification, a polyvinyl alcohol-based polymer refers to a polymer containing vinyl alcohol units (hereinafter also referred to as "VA units") as its repeating units. One type of polyvinyl alcohol-based polymer may be used alone, or two or more types may be used in combination. The polyvinyl alcohol-based polymer may contain only VA units as repeating units, or may contain VA units and repeating units other than VA units (hereinafter also referred to as "non-VA units"). The polyvinyl alcohol-based polymer may be a random copolymer containing VA units and non-VA units, a block copolymer, an alternating 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.

[0042] The polyvinyl alcohol-based polymer may be unmodified polyvinyl alcohol (unmodified PVA) or modified polyvinyl alcohol (modified PVA). Here, unmodified PVA is a polymer produced by hydrolysis (saponification) of polyvinyl acetate, and has a repeating unit (-CH ２ -CH(OCOCH ３ )-) and a polyvinyl alcohol-based polymer that is substantially free of repeating units other than VA units. The degree of saponification of the unmodified PVA may be, for example, 60% or more, and from the viewpoint of water solubility, may be 70% or more, 80% or more, or 90% or more. In some embodiments, the degree of saponification of the unmodified PVA may be 98% or more (complete saponification).

[0043] The polyvinyl alcohol-based polymer may be a modified PVA containing VA units and non-VA units having at least one structure selected from oxyalkylene groups, carboxy groups, (di)carboxylic acid groups, (di)carboxylic acid ester groups, phenyl groups, naphthyl groups, sulfo groups, amino groups, hydroxyl groups, amide groups, imide groups, nitrile groups, ether groups, ester groups, and salts thereof. Non-VA units that may be contained in the modified PVA include, but are not limited to, repeating units derived from N-vinyl monomers or N-(meth)acryloyl monomers, as described below, repeating units derived from ethylene, repeating units derived from alkyl vinyl ethers, repeating units derived from vinyl esters of monocarboxylic acids having 3 or more carbon atoms, and repeating units derived from (di)acetone compounds. A preferred example of the N-vinyl monomer is N-vinylpyrrolidone. A preferred example of the N-(meth)acryloyl monomer is N-(meth)acryloylmorpholine. The alkyl vinyl ether may be a vinyl ether having an alkyl group having from 1 to 10 carbon atoms, such as propyl vinyl ether, butyl vinyl ether, or 2-ethylhexyl vinyl ether. The vinyl ester of a monocarboxylic acid having from 3 to 7 carbon atoms may be a vinyl ester of a monocarboxylic acid having from 3 to 7 carbon atoms, such as vinyl propanoate, vinyl butanoate, vinyl pentanoate, or vinyl hexanoate. Suitable examples of the (di)acetone compound include diacetone (meth)acrylamide and acetylacetone.

[0044] In some preferred embodiments, an acetalized polyvinyl alcohol polymer is used as the polyvinyl alcohol polymer. An example of an acetalized polyvinyl alcohol polymer is a modified PVA in which some of the VA units contained in the polyvinyl alcohol polymer have been acetalized. The modified PVA in which some of the VA units contained in the polyvinyl alcohol polymer have been acetalized (acetalized PVA (ac-PVA)) can be obtained by reacting some of the hydroxy groups of the polyvinyl alcohol polymer with an aldehyde compound or a ketone compound to acetalize the polymer. Typically, the acetalized polyvinyl alcohol polymer is obtained by the acetalization reaction of a polyvinyl alcohol polymer with an aldehyde compound. In some preferred embodiments, the aldehyde compound has 1 to 7 carbon atoms, more preferably 2 to 7 carbon atoms.

[0045] Examples of the aldehyde compound include formaldehyde; linear or branched alkyl aldehydes such as acetaldehyde, propionaldehyde, n-butylaldehyde, isobutyraldehyde, t-butylaldehyde, and hexylaldehyde; and alicyclic or aromatic aldehydes such as cyclohexanecarbaldehyde and benzaldehyde. These may be used alone or in combination of two or more. With the exception of formaldehyde, one or more hydrogen atoms may be substituted with a halogen or the like. Among these, linear or branched alkyl aldehydes are preferred because of their high solubility in water and ease of acetalization reaction, and among these, acetaldehyde, n-propylaldehyde, n-butylaldehyde, and n-pentylaldehyde are more preferred.

[0046] In addition to the above, aldehyde compounds having 8 or more carbon atoms such as 2-ethylhexylaldehyde, nonylaldehyde, and decylaldehyde may also be used as the aldehyde compound.

[0047] Acetalized polyvinyl alcohol-based polymers have the following chemical formula: -CH ２The copolymer contains a VA unit, which is a structural moiety represented by —CH(OH)—; and an acetalized structural unit (hereinafter also referred to as a “VAC unit”) represented by the following general formula (1):

[0048] (In formula (1), R is a hydrogen atom or a linear or branched alkyl group, and the alkyl group may be substituted with a functional group.)

[0049] In some preferred embodiments, R in the above formula (1) is a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms. R may be one of these groups or a combination of two or more of these groups. From the viewpoint of improving haze reduction performance, R is preferably a linear or branched alkyl chain having 1 to 6 carbon atoms.

[0050] From the viewpoint of improving haze reduction performance, the acetalization degree of the acetalized polyvinyl alcohol-based polymer can be 1 mol% or more, may be 5 mol% or more, preferably 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, particularly preferably 25 mol% or more (e.g., 27 mol% or more). From the viewpoint of improving hydrophilicity, the acetalization degree of the acetalized polyvinyl alcohol-based polymer is preferably less than 60 mol%, even more preferably 50 mol% or less, more preferably 40 mol% or less, particularly preferably 35 mol% or less (e.g., 33 mol% or less). In this specification, "acetalization degree" refers to the proportion of acetalized structural units (VAC units) in all repeating units constituting the acetalized polyvinyl alcohol-based polymer.

[0051] Furthermore, as the polyvinyl alcohol-based polymer, a cation-modified polyvinyl alcohol into which a cationic group such as a quaternary ammonium structure has been introduced may be used. Examples of the cation-modified polyvinyl alcohol include those into which a cationic group derived from a monomer having a cationic group, such as a diallyldialkylammonium salt or an N-(meth)acryloylaminoalkyl-N,N,N-trialkylammonium salt, has been introduced. Furthermore, as the vinyl alcohol-based polymer, a non-VA unit having the chemical formula: -CH ２-CH(CR １ (OR ４ )-CR ２ (OR ５ )-R ３ )-, where R １ ~R ３ each independently represents a hydrogen atom or an organic group, R ４ and R ５ are each independently a hydrogen atom or R ６ -CO- (wherein, R ６ represents an alkyl group. For example, R １ ~R ３ When at least one of R is an organic group, the organic group may be a linear or branched alkyl group having 1 to 8 carbon atoms. ６ can be a linear or branched alkyl group having from 1 to 8 carbon atoms.

[0052] In some embodiments, the modified PVA used is a modified PVA having a 1,2-diol structure in a side chain. １ ~R ５ A modified PVA (butenediol-vinyl alcohol copolymer (BVOH)) containing non-VA units in which is a hydrogen atom can be employed.

[0053] The proportion of moles of VA units to the total number of moles of repeating units constituting the polyvinyl alcohol-based polymer may be, for example, 5% or more, 10% or more, 20% or more, or 30% or more. While not particularly limited, in some embodiments, the proportion of moles of VA units may be 50% or more, 65% or more, 75% or more, 80% or more, or 90% or more (e.g., 95% or more, or 98% or more). Substantially 100% of the repeating units constituting the polyvinyl alcohol-based polymer may be VA units. Here, "substantially 100%" means that the polyvinyl alcohol-based polymer does not, at least intentionally, contain non-VA units. Typically, the proportion of moles of non-VA units to the total number of moles of repeating units is less than 2% (e.g., less than 1%), including 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, 90% or less, 80% or less, or 70% or less.

[0054] The content of VA units in the polyvinyl alcohol-based polymer (content by weight) 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. While not particularly limited, in some embodiments, the content of VA units may be 50% by weight or more (e.g., more than 50% by weight), 70% by weight or more, or 80% by weight or more (e.g., 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-based polymer may be VA units. Here, "substantially 100% by weight" means that non-VA units are not, at least intentionally, contained as repeating units constituting the polyvinyl alcohol-based polymer, and typically means that the content of non-VA units in the polyvinyl alcohol-based polymer is less than 2% by weight (e.g., 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.

[0055] A polyvinyl alcohol-based polymer may contain multiple polymer chains with different VA unit contents within the same molecule. Here, the term "polymer chain" refers to a segment that constitutes a part of a single polymer molecule. For example, a polyvinyl alcohol-based polymer may contain, within the same molecule, a polymer chain A with a VA unit content of more than 50% by weight and a polymer chain B with a VA unit content of less than 50% by weight (i.e., a non-VA unit content of more than 50% by weight).

[0056] The 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 the 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.

[0057] 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, or 98% by weight or more. Substantially 100% by weight of the repeating units constituting polymer chain B may be non-VA units.

[0058] Examples of polyvinyl alcohol-based polymers containing polymer chain A and polymer chain B in the same molecule include block copolymers and graft copolymers containing these polymer chains. The graft copolymer may be a graft copolymer having a structure in which polymer chain B (side chain) is grafted to polymer chain A (main chain), or a graft copolymer having a structure in which polymer chain A (side chain) is grafted to polymer chain B (main chain). In some embodiments, a polyvinyl alcohol-based polymer having a structure in which polymer chain B is grafted to polymer chain A can be used.

[0059] Examples of polymer chain B include polymer chains having a repeating unit derived from an N-vinyl type monomer as the main repeating unit, polymer chains having a repeating unit derived from an N-(meth)acryloyl type monomer as the main repeating unit, polymer chains having a repeating unit derived from a vinyl dicarboxylate such as fumaric acid, maleic acid, or maleic anhydride as the main repeating unit, polymer chains having a repeating unit derived from an aromatic vinyl monomer such as styrene or vinylnaphthalene as the main repeating unit, and polymer chains having an oxyalkylene unit as the main repeating unit. In this specification, unless otherwise specified, the term "main repeating unit" refers to a repeating unit contained in an amount of more than 50% by weight.

[0060] A suitable example of the polymer chain B is a polymer chain having an N-vinyl monomer as the main repeating unit, i.e., an N-vinyl 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, and may be 70% by weight or more, 85% by weight or more, or 95% by weight or more. Substantially all of the polymer chain B may be repeating units derived from N-vinyl monomers.

[0061] In this specification, examples of N-vinyl monomers include monomers having a nitrogen-containing heterocycle (e.g., a lactam ring) and N-vinyl linear amides. Specific examples of N-vinyl lactam monomers include N-vinylpyrrolidone, N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam, N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholinedione. Specific examples of N-vinyl linear amides include N-vinylacetamide, N-vinylpropionic acid amide, and N-vinylbutyric acid amide. Polymer chain B may be, for example, an N-vinyl polymer chain in which more than 50% by weight (e.g., 70% by weight or more, 85% by weight or more, or 95% by weight or more) of its repeating units are N-vinylpyrrolidone units. Substantially all of the repeating units constituting polymer chain B may be N-vinylpyrrolidone units.

[0062] Another example of polymer chain B is a polymer chain having a repeating unit derived from an N-(meth)acryloyl-type monomer as the main repeating unit, i.e., 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, 85% by weight or more, or 95% by weight or more. Substantially all of polymer chain B may be repeating units derived from N-(meth)acryloyl-type monomers.

[0063] 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-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; and N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di(n-butyl)(meth)acrylamide. Examples of cyclic amides having an N-(meth)acryloyl group include N-(meth)acryloylmorpholine and N-(meth)acryloylpyrrolidine.

[0064] Other examples of polymer chain B include polymer chains containing oxyalkylene units as main repeating units, i.e., oxyalkylene-based polymer chains. The content of oxyalkylene units in the oxyalkylene-based polymer chain is typically more than 50% by weight, and may be 70% by weight or more, 85% by weight or more, or 95% by weight or more. Substantially all of the repeating units contained in polymer chain B may be oxyalkylene units.

[0065] Examples of oxyalkylene units include oxyethylene units, oxypropylene units, oxybutylene units, etc. Such oxyalkylene units may be repeating units derived from the corresponding alkylene oxides. The oxyalkylene units contained in the oxyalkylene polymer chain may be one type or two or more types. For example, the oxyalkylene polymer chain may contain a combination of oxyethylene units and oxypropylene units. In an oxyalkylene polymer chain containing two or more types of oxyalkylene units, the oxyalkylene units may be a random copolymer, a block copolymer, an alternating copolymer, or a graft copolymer of the corresponding alkylene oxides.

[0066] Further examples of the polymer chain B include a polymer chain containing a repeating unit derived from an alkyl vinyl ether (e.g., a vinyl ether having an alkyl group having from 1 to 10 carbon atoms), a polymer chain containing a repeating unit derived from a monocarboxylic acid vinyl ester (e.g., a vinyl ester of a monocarboxylic acid having 3 or more carbon atoms), and a polymer chain into which a cationic group (e.g., a cationic group having a quaternary ammonium structure) has been introduced.

[0067] The polyvinyl alcohol-based polymer serving as the water-soluble polymer is preferably a modified polyvinyl alcohol, which is a copolymer containing VA units and non-VA units. The degree of saponification of the modified polyvinyl alcohol-based polymer serving as the water-soluble polymer is typically 50 mol% or more, preferably 65 mol% or more, more preferably 70 mol% or more, for example, 75 mol% or more. When a modified PVA having a 1,2-diol structure is used as the copolymer containing VA units and non-VA units, the degree of saponification of the polyvinyl alcohol-based polymer may be 95 mol% or more (e.g., more than 95 mol%), or even 98 mol% or more. In principle, the degree of saponification of the polyvinyl alcohol-based polymer is 100 mol% or less. While not particularly limited, in some embodiments, when the non-VA units contain nitrogen atoms, a polymer having a VA unit content of 50 wt% or more is used as the water-soluble polymer (polyvinyl alcohol-based polymer).

[0068] In some embodiments, an N-vinyl polymer can be used as the water-soluble polymer. Examples of N-vinyl polymers include polymers containing repeating units derived from monomers having a nitrogen-containing heterocycle (e.g., a lactam ring). Examples of such polymers include homopolymers and copolymers of N-vinyl lactam monomers (e.g., copolymers in which the copolymerization ratio of N-vinyl lactam monomers exceeds 50% by weight), homopolymers and copolymers of N-vinyl linear amides (e.g., copolymers in which the copolymerization ratio of N-vinyl linear amides exceeds 50% by weight), and the like.

[0069] Specific examples of N-vinyl lactam monomers (i.e., compounds having a lactam structure and an N-vinyl group in one molecule) include N-vinylpyrrolidone (VP), N-vinylpiperidone, N-vinylmorpholinone, N-vinylcaprolactam (VC), N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholinedione. Specific examples of polymers containing N-vinyl lactam monomer units include polyvinylpyrrolidone, polyvinylcaprolactam, random copolymers of VP and VC, random copolymers of one or both of VP and VC with other vinyl monomers (e.g., acrylic monomers, vinyl ester monomers, etc.), block copolymers, alternating copolymers, and graft copolymers containing polymer chains containing one or both of VP and VC. Specific examples of N-vinyl linear amides include N-vinylacetamide, N-vinylpropionic acid amide, and N-vinylbutyric acid amide.

[0070] In some other embodiments, an N-(meth)acryloyl polymer may be used as the water-soluble polymer. Examples of N-(meth)acryloyl polymers include homopolymers and copolymers of N-(meth)acryloyl monomers (typically copolymers in which the copolymerization ratio of N-(meth)acryloyl monomers exceeds 50% by weight). Examples of N-(meth)acryloyl monomers include linear amides having an N-(meth)acryloyl group and cyclic amides having an N-(meth)acryloyl group. In this specification, the term "(meth)acryloyl" refers to both acryloyl and methacryloyl groups in a comprehensive sense. In this specification, the term "(meth)acryloyl group" refers to both acryloyl and methacryloyl groups in a comprehensive sense.

[0071] Examples of chain amides having an N-(meth)acryloyl group include (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; and N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and N,N-di(n-butyl)(meth)acrylamide. Other examples include N-hydroxyethylacrylamide (HEAA). Examples of polymers containing chain amides having an N-(meth)acryloyl group as a monomer unit include homopolymers of N-isopropylacrylamide and copolymers of N-isopropylacrylamide (for example, copolymers in which the copolymerization ratio of N-isopropylacrylamide exceeds 50% by weight). In this specification, the term "(meth)acrylamide" refers to acrylamide and methacrylamide in a comprehensive sense.

[0072] Examples of cyclic amides having an N-(meth)acryloyl group include N-acryloylmorpholine, N-acryloylthiomorpholine, N-acryloylpiperidine, N-acryloylpyrrolidine, N-methacryloylmorpholine, N-methacryloylpiperidine, and N-methacryloylpyrrolidine. Examples of polymers containing cyclic amides having an N-(meth)acryloyl group as monomer units include acryloylmorpholine-based polymers (PACMO). Typical examples of acryloylmorpholine-based polymers include homopolymers of N-acryloylmorpholine (ACMO) and copolymers of ACMO (e.g., copolymers in which the copolymerization ratio of ACMO exceeds 50% by weight). In acryloylmorpholine-based polymers, the proportion of the number of moles of ACMO units in the number of moles of all repeating units is typically 50% or more, and suitably 80% or more (e.g., 90% or more, typically 95% or more). All repeating units of the water-soluble polymer may be substantially composed of ACMO units.

[0073] In some embodiments, the water-soluble polymer is a polymer derived from natural products, such as cellulose derivatives and starch derivatives.

[0074] In some embodiments, a cellulose derivative is used as the water-soluble polymer. Here, the cellulose derivative is a polymer containing β-glucose units as the main repeating unit. Specific examples of cellulose derivatives include hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and carboxymethyl cellulose. Of these, HEC is preferred.

[0075] In some other embodiments, the water-soluble polymer is a starch derivative, which is a polymer containing α-glucose units as the main repeating unit, such as pregelatinized starch, pullulan, carboxymethyl starch, and cyclodextrin.

[0076] In some other preferred embodiments, a synthetic polymer is used as the water-soluble polymer.

[0077] In some embodiments, a polymer containing an oxyalkylene unit is used as the water-soluble polymer. Examples of polymers containing an oxyalkylene unit include polyethylene oxide (PEO), block copolymers of ethylene oxide (EO) and propylene oxide (PO) or butylene oxide (BO), and random copolymers of EO and PO or BO. Among these, block copolymers of EO and PO or random copolymers of EO and PO are preferred. The block copolymer of EO and PO may be a diblock copolymer containing a PEO block and a polypropylene oxide (PPO) block, or a triblock copolymer. Examples of the triblock copolymer include PEO-PPO-PEO type triblock copolymers and PPO-PEO-PPO type triblock copolymers. Typically, PEO-PPO-PEO type triblock copolymers are more preferred.

[0078] In this specification, unless otherwise specified, the term "copolymer" refers collectively to various copolymers such as random copolymers, alternating copolymers, block copolymers, and graft copolymers.

[0079] In a block copolymer or random copolymer of EO and PO, the molar ratio of EO to PO (EO / PO) constituting the copolymer is preferably greater than 1, more preferably 2 or more, and even more preferably 3 or more (e.g., 5 or more), from the viewpoints of solubility in water, washability, etc.

[0080] In some embodiments, a carboxylic acid polymer is used as the water-soluble polymer. Examples of carboxylic acid polymers include polymers containing maleic acid units and polymers containing (meth)acrylic acid units. Examples of polymers containing maleic acid units include styrene-maleic acid copolymers or salts thereof, styrene-maleic anhydride copolymers, styrene sulfonic acid-maleic acid copolymers or salts thereof, copolymers of styrene sulfonate and maleic acid, and maleic acid-vinyl acetate copolymers. Examples of polymers containing (meth)acrylic acid units include polyacrylic acid or salts thereof, styrene-acrylic acid copolymers or salts thereof, styrene sulfonic acid-acrylic acid copolymers or salts thereof, copolymers of styrene sulfonate and acrylic acid, acrylic acid-vinyl acetate copolymers, and acrylic acid / sulfonic acid monomer copolymers. In this specification, (meth)acrylic acid refers collectively to acrylic acid and methacrylic acid.

[0081] In the technology disclosed herein, the weight average molecular weight (Mw) of the water-soluble polymer is not particularly limited. The Mw of the water-soluble polymer is, for example, about 200×10 ４ or less, and may be approximately 150×10 ４ From the viewpoint of cleaning properties, it is preferable to use a value of about 100×10 ４ is approximately 50×10 ４ From the viewpoint of protecting the polishing surface, the Mw of the water-soluble polymer may be, for example, 0.5 × 10 ４In some embodiments, the Mw is 1.0×10 or more. ４ The above is appropriate, and 2 x 10 ４ or more, for example, 5×10 ４ More than that is fine.

[0082] Although not particularly limited, in some embodiments, the content of the water-soluble polymer in the polishing composition (when two or more water-soluble polymers are contained, the total content thereof) can be, for example, 0.01 parts by weight or more relative to 100 parts by weight of abrasive grains (typically silica particles). From the viewpoint of haze reduction, etc., it is appropriate to set it to 0.1 parts by weight or more, preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, and even 2 parts by weight or more. Furthermore, the content of the water-soluble polymer relative to 100 parts by weight of abrasive grains may be, for example, 50 parts by weight or less, or may be 30 parts by weight or less. From the viewpoint of dispersion stability of the polishing composition, etc., in some embodiments, the content of the water-soluble polymer relative to 100 parts by weight of abrasive grains is appropriate to be 15 parts by weight or less, preferably 10 parts by weight or less, more preferably 5 parts by weight or less, for example, 3.5 parts by weight or less. By appropriately setting the amount of the water-soluble polymer used within the above range, high surface quality can be obtained.

[0083] In some embodiments, the water-soluble polymer content W Ｐ Water-soluble polymer P Ａ Content of W Ａ The ratio (W Ａ / W Ｐ ) is not particularly limited, and may be, for example, 0.1 or more, 0.2 or more, or 0.3 or more by weight. In some other embodiments, the ratio (W Ａ / W Ｐ ) may be, for example, 0.5 or more, 1 or more, or 1.5 or more on a weight basis. Ａ / W Ｐ The upper limit of the number of carbon atoms is not particularly limited, but may be, for example, 10 or less, 8 or less, 6 or less, or 4 or less by weight.

[0084] In an embodiment using a polishing composition containing a water-soluble polymer, the water-soluble polymer may be, for example, a cellulose derivative (e.g., HEC) that is adsorbent to both abrasive grains (typically, silica particles) and silicon wafers, or ac-PVA, which primarily adsorbs to silicon wafers, may be used in combination with PACMO, which primarily adsorbs to abrasive grains, or ac-PVA may be used alone. The type of water-soluble polymer can be appropriately selected taking into consideration the degree of protection provided to the surface of the silicon wafer, etc. By selecting or combining water-soluble polymers, the adsorption of the water-soluble polymer to the abrasive grains and silicon wafers can be adjusted in a well-balanced manner, making it easier to obtain a high-quality polished surface.

[0085] <Basic Compound> The polishing composition disclosed herein contains a basic compound. In this specification, the term "basic compound" refers to a compound that dissolves in water and increases the pH of the aqueous solution. Examples of basic compounds that can be used include nitrogen-containing organic or inorganic basic compounds, phosphorus-containing basic compounds, alkali metal hydroxides, alkaline earth metal hydroxides, various carbonates and hydrogen carbonates, etc. Examples of nitrogen-containing basic compounds include quaternary ammonium compounds, ammonia, amines (preferably water-soluble amines), etc. Examples of phosphorus-containing basic compounds include quaternary phosphonium compounds. Such basic compounds can be used alone or in combination of two or more.

[0086] Specific examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of carbonates or bicarbonates include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate. 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 azoles such as imidazole and triazole. Specific examples of quaternary phosphonium compounds include quaternary phosphonium hydroxides such as tetramethylphosphonium hydroxide and tetraethylphosphonium hydroxide.

[0087] As the quaternary ammonium compound, a quaternary ammonium salt (typically a strong base) such as a tetraalkylammonium salt or a hydroxyalkyltrialkylammonium salt can be used. The anion component in such a quaternary ammonium salt is, for example, OH － , F － , Cl － ,Br － , I － , ClO ４ － , B.H. ４ － Examples of the quaternary ammonium compounds include those in which the anion is OH － Specific examples of quaternary ammonium hydroxides include tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, and tetrahexylammonium hydroxide; hydroxyalkyltrialkylammonium hydroxides such as 2-hydroxyethyltrimethylammonium hydroxide (also known as choline); and the like.

[0088] Among these basic compounds, at least one basic compound selected from, for example, alkali metal hydroxides, quaternary ammonium hydroxides, and ammonia can be preferably used. Among these, tetraalkylammonium hydroxides (e.g., tetramethylammonium hydroxide) and ammonia are more preferred, and ammonia is particularly preferred.

[0089] <Surfactant> In some embodiments, the polishing composition preferably contains at least one surfactant. The inclusion of a surfactant in the polishing composition can be advantageous in suppressing or reducing the increase in haze on the polished surface. Any of anionic, cationic, nonionic, and amphoteric surfactants can be used as the surfactant. Typically, anionic or nonionic surfactants are preferred. Nonionic surfactants are more preferred from the viewpoint of optimally exhibiting the effects of the polishing composition disclosed herein. Examples of nonionic surfactants include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyalkylene derivatives (e.g., polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters) (e.g., polyoxyalkylene adducts); and copolymers of multiple oxyalkylenes (e.g., diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers). The surfactants can be used alone or in combination of two or more.

[0090] Specific examples of nonionic surfactants include block copolymers of ethylene oxide (EO) and propylene oxide (PO) (diblock copolymers, PEO (polyethylene oxide)-PPO (polypropylene oxide)-PEO type triblock copolymers, PPO-PEO-PPO type triblock copolymers, etc.), random copolymers of EO and PO, polyoxyethylene glycol, polyoxyethylene propyl ether, polyoxyethylene butyl ether, polyoxyethylene pentyl ether, polyoxyethylene hexyl ether, polyoxyethylene octyl ether, 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, polyoxyethylene isostearyl ether, polyoxyethylene octyl ether, polyoxyethylene ... Examples of the hydroxypropyl ether include oleyl ether, polyoxyethylene phenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene laurylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene distearate, polyoxyethylene monooleate, polyoxyethylene dioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopaltimate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tetraoleate, polyoxyethylene castor oil, and polyoxyethylene hydrogenated castor oil.Among these, preferred surfactants include block copolymers of EO and PO (particularly PEO-PPO-PEO type triblock copolymers), random copolymers of EO and PO, and polyoxyethylene alkyl ethers (e.g., polyoxyethylene decyl ether).As the polyoxyethylene alkyl ether, those having an EO addition mole number of about 1 to 10 (e.g., about 3 to 8) can be preferably used.

[0091] The molecular weight of the surfactant is, for example, less than 5,000, and is preferably 4,000 or less from the viewpoint of filterability and washability, and may be, for example, less than 3,000. Furthermore, from the viewpoint of surface activity, the molecular weight of the surfactant is usually suitably 200 or more, and from the viewpoint of the effect of suppressing or reducing haze increase, it is preferably 250 or more (e.g., 300 or more). A more preferred range of the molecular weight of the surfactant may vary depending on the type of surfactant. For example, when a polyoxyethylene alkyl ether is used as the surfactant, its molecular weight is, for example, preferably less than 2,000, more preferably 1,900 or less (e.g., less than 1,800), even more preferably 1,500 or less, and may be 1,000 or less (e.g., 500 or less). Furthermore, when a block copolymer of EO and PO is used as the surfactant, its weight average molecular weight may be, for example, 500 or more, 1,000 or more, even 1,500 or more, 2,000 or more, or even 2,500 or more. The upper limit of the weight average molecular weight is, for example, less than 5,000, preferably 4,500 or less, and may be, for example, less than 4,000.

[0092] The molecular weight of the surfactant may be the molecular weight calculated from the chemical formula, or the weight average molecular weight (water-based, polyethylene glycol equivalent) determined by GPC. For example, in the case of polyoxyethylene alkyl ether, it is preferable to use the molecular weight calculated from the chemical formula, and in the case of a block copolymer of EO and PO, it is preferable to use the weight average molecular weight determined by GPC.

[0093] Although not particularly limited, in an embodiment in which the polishing composition contains a surfactant, the content of the surfactant is usually suitably 20 parts by weight or less, preferably 10 parts by weight or less, and more preferably 6 parts by weight or less (e.g., 3 parts by weight or less) relative to 100 parts by weight of abrasive grains (typically silica particles) from the viewpoint of cleaning properties, etc. From the viewpoint of better exerting the effect of using the surfactant, the content of the surfactant relative to 100 parts by weight of abrasive grains is suitably 0.001 parts by weight or more, preferably 0.01 parts by weight or more, more preferably 0.1 parts by weight or more, and may be 0.5 parts by weight or more.

[0094] <Water> The water contained in the polishing composition disclosed herein can preferably be ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like. To minimize the inhibition of the functions of other components contained in the polishing composition, the water used preferably has a total transition metal ion content of 100 ppb or less. For example, the purity of the water can be increased by removing impurity ions using an ion exchange resin, removing foreign matter using a filter, or by distillation, among other procedures. The polishing composition disclosed herein may further contain an organic solvent (e.g., a lower alcohol or a lower ketone) that is uniformly miscible with water, as needed. Preferably, 90% by volume or more of the solvent contained in the polishing composition is water, and more preferably 95% by volume or more (e.g., 99 to 100% by volume) is water.

[0095] <Other Components> The polishing composition disclosed herein may further contain, as necessary, known additives that can be used in polishing compositions (e.g., polishing compositions used in the finish polishing step of silicon wafers), such as organic acids, organic acid salts, inorganic acids, inorganic acid salts, chelating agents, preservatives, and antifungal agents, within the range that does not significantly impair the effects of the present invention.

[0096] The organic acids and their salts, and the inorganic acids and their salts can be used alone or in combination of two or more. Examples of organic acids include fatty acids such as formic acid, acetic acid, and propionic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, itaconic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, glycolic acid, malonic acid, gluconic acid, alanine, glycine, lactic acid, organic sulfonic acids such as hydroxyethylidene diphosphate (HEDP) and methanesulfonic acid, and organic phosphonic acids such as nitrilotris(methylene phosphate) (NTMP) and phosphonobutanetricarboxylic acid (PBTC). Examples of organic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of organic acids. Examples of inorganic acids include hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, boric acid, and carbonic acid. Examples of inorganic acid salts include alkali metal salts (sodium salts, potassium salts, etc.) and ammonium salts of inorganic acids.

[0097] The chelating agent may be used alone or in combination of two or more. Examples of the chelating agent include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Suitable examples of the chelating agent include ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and diethylenetriaminepentaacetic acid. Examples of the preservatives and antifungal agents include isothiazolinone compounds, parahydroxybenzoic acid esters, phenoxyethanol, etc.

[0098] The polishing composition disclosed herein preferably does not substantially contain an oxidizing agent. If an oxidizing agent is contained in the polishing composition, when the polishing composition is supplied to a silicon wafer, the surface of the silicon wafer may be oxidized to form an oxide film, which may result in a decrease in the polishing rate. Specific examples of the oxidizing agent include hydrogen peroxide (H ２ O ２), sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, etc. In addition, "the polishing composition is substantially free of an oxidizing agent" means that the oxidizing agent is not contained at least intentionally. Therefore, a polishing composition that inevitably contains a trace amount of oxidizing agent due to raw materials, manufacturing method, etc. (for example, a polishing composition in which the molar concentration of the oxidizing agent in the polishing composition is 0.001 mol / L or less, preferably 0.0005 mol / L or less, more preferably 0.0001 mol / L or less, even more preferably 0.00005 mol / L or less, and particularly preferably 0.00001 mol / L or less) can be included in the concept of a polishing composition that is substantially free of an oxidizing agent as used herein.

[0099] <pH> The pH of the polishing composition disclosed herein is not particularly limited, and an appropriate pH can be adopted depending on the purpose and application. In some embodiments, the pH of the polishing composition is suitably 8.0 or higher, preferably 8.5 or higher, more preferably 9.0 or higher. As the pH of the polishing composition increases, the polishing rate tends to improve. On the other hand, for example, in an embodiment using silica particles as abrasive grains, from the viewpoint of preventing dissolution of the silica particles and suppressing a decrease in mechanical polishing action, the pH of the polishing composition is usually suitably 12.0 or lower, preferably 11.0 or lower, more preferably 10.8 or lower, and even more preferably 10.5 or lower.

[0100] In the technology disclosed herein, the pH of the polishing composition can be determined by using a pH meter (e.g., a glass electrode hydrogen ion concentration indicator (model number F-72) manufactured by Horiba, Ltd.) and performing three-point calibration using standard buffer solutions (phthalate pH buffer solution, pH: 4.01 (25°C), neutral phosphate pH buffer solution, pH: 6.86 (25°C), carbonate pH buffer solution, pH: 10.01 (25°C)), then placing the glass electrode in the composition to be measured and measuring the value after stabilization for at least two minutes.

[0101] <Polishing Liquid> The polishing composition disclosed herein is typically supplied to the surface of a silicon wafer in the form of a polishing liquid containing the polishing composition, and used to polish the silicon wafer. The polishing liquid can be prepared, for example, by diluting any of the polishing compositions disclosed herein (typically with water). Alternatively, the polishing composition may be used as is as a polishing liquid. Another example of a polishing liquid containing the polishing composition disclosed herein is a polishing liquid obtained by adjusting the pH of the composition.

[0102] The content of abrasive grains (typically silica particles) in the polishing liquid is not particularly limited, and is, for example, 0.01 wt % or more, preferably 0.05 wt % or more, more preferably 0.10 wt % or more, and even more preferably 0.15 wt % or more. By increasing the abrasive grain content, a higher polishing rate can be achieved. The content is suitably 10 wt % or less, preferably 7 wt % or less, more preferably 5 wt % or less, and even more preferably 2 wt % or less, and may be, for example, 1 wt % or less, 0.5 wt % or less, or 0.4 wt % or less. This makes it easier to maintain surface quality.

[0103] Water-soluble polymer P in polishing liquid Ａ The content of the water-soluble polymer P is not particularly limited, but from the viewpoint of improving surface quality, it may be, for example, 0.0001% by weight or more, and usually 0.0005% by weight or more is appropriate, and it is preferably 0.001% by weight or more, or 0.002% by weight or more, or 0.003% by weight or more, or 0.004% by weight or more. Ａ The upper limit of the content of the water-soluble polymer P is not particularly limited, and can be, for example, 0.1% by weight or less. In view of stability at the concentrated liquid stage, polishing rate, cleanability, etc., in some embodiments, the water-soluble polymer P Ａ The content is preferably 0.05% by weight or less, more preferably 0.02% by weight or less, and even more preferably 0.01% by weight or less, and may be 0.005% by weight or less, or may be less than 0.003% by weight.

[0104] The content of the water-soluble polymer in the polishing liquid (when two or more water-soluble polymers are contained, the total content thereof) is not particularly limited, and in some embodiments, it can be, for example, 0.0001 wt % or more. From the viewpoint of reducing haze, etc., the total content is preferably 0.0005 wt % or more, more preferably 0.001 wt % or more, even more preferably 0.002 wt % or more, and may be, for example, 0.005 wt % or more. Furthermore, the upper limit of the total content is, for example, 0.5 wt % or less, and from the viewpoint of polishing rate, etc., it is preferably 0.2 wt % or less, more preferably 0.1 wt % or less, and even more preferably 0.05 wt % or less (for example, 0.02 wt % or less, or even 0.015 wt % or less).

[0105] The content of the basic compound in the polishing liquid is not particularly limited. From the viewpoint of polishing at an appropriate polishing rate, the content is usually suitably 0.0005 wt % or more, preferably 0.001 wt % or more, and more preferably 0.003 wt % or more. Furthermore, from the viewpoint of improving surface quality (e.g., suppressing an increase in haze and reducing defects), the content is suitably less than 0.1 wt %, preferably less than 0.05 wt %, and more preferably less than 0.03 wt % (e.g., less than 0.025 wt %, or even less than 0.01 wt %).

[0106] When a surfactant is contained, the content of the surfactant in the polishing liquid (when two or more surfactants are contained, the total content thereof) is not particularly limited as long as it is within a range that does not significantly impair the effects of the present invention. Typically, the content of the surfactant can be, for example, 0.00001 wt % or more from the viewpoint of cleanability, etc. From the viewpoint of haze reduction, etc., the content is preferably 0.0002 wt % or more, more preferably 0.0003 wt % or more, and even more preferably 0.0005 wt % or more. Furthermore, from the viewpoint of polishing rate, etc., the content is preferably 0.1 wt % or less, more preferably 0.01 wt % or less, and even more preferably 0.005 wt % or less (for example, 0.002 wt % or less).

[0107] <Concentrated Liquid> The polishing composition disclosed herein may be in a concentrated form (i.e., in the form of a concentrated polishing liquid) before being supplied to a silicon wafer. Such a concentrated polishing composition is advantageous from the viewpoints of convenience and cost reduction during production, distribution, storage, etc. The concentration ratio is not particularly limited and can be, for example, about 2 to 100 times in volume terms, and typically about 5 to 50 times (e.g., about 10 to 40 times) is appropriate. Such a concentrated liquid can be diluted at the desired time to prepare a polishing liquid (working slurry), which can then be supplied to a silicon wafer. The dilution can be performed, for example, by adding water to the concentrated liquid and mixing.

[0108] When the polishing composition (i.e., concentrate) is diluted and used for polishing, the content of abrasive grains in the concentrate can be, for example, 25% by weight or less. From the viewpoint of the dispersion stability and filterability of the polishing composition, the content is usually preferably 20% by weight or less, more preferably 15% by weight or less. In some preferred embodiments, the content of abrasive grains may be 10% by weight or less, or may be 5% by weight or less. Furthermore, from the viewpoint of convenience and cost reduction during production, distribution, storage, etc., the content of abrasive grains in the concentrate can be, for example, 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 0.7% by weight or more, and even more preferably 1% by weight or more.

[0109] In some embodiments, the water-soluble polymer P in the concentrate Ａ The content of can be, for example, 3 wt % or less. From the viewpoint of the filterability and washability of the polishing composition, the content is usually preferably 1 wt % or less, more preferably 0.5 wt % or less. Furthermore, from the viewpoint of convenience and cost reduction during production, distribution, storage, etc., the content is usually appropriate to be 0.001 wt % or more, preferably 0.005 wt % or more, more preferably 0.01 wt % or more.

[0110] In some embodiments, the content of the water-soluble polymer in the concentrate (when two or more water-soluble polymers are contained, the total content thereof) can be, for example, 3 wt % or less. From the viewpoint of the filterability and washability of the polishing composition, the content is usually preferably 1 wt % or less, more preferably 0.5 wt % or less. Furthermore, from the viewpoint of convenience and cost reduction during production, distribution, storage, etc., the content is usually 0.001 wt % or more, preferably 0.005 wt % or more, more preferably 0.01 wt % or more.

[0111] In some embodiments, the content of the basic compound in the concentrate can be, for example, less than 0.25 wt%. From the viewpoint of storage stability, etc., the content is usually preferably 0.15 wt% or less, more preferably 0.1 wt% or less. Furthermore, from the viewpoint of convenience and cost reduction during production, distribution, storage, etc., the content of the basic compound in the concentrate can be, for example, 0.005 wt% or more, preferably 0.01 wt% or more, more preferably 0.02 wt% or more, and even more preferably 0.05 wt% or more.

[0112] In an embodiment in which the polishing composition contains a surfactant, the surfactant content in the concentrate can be, for example, 0.25 wt % or less, preferably 0.15 wt % or less, more preferably 0.1 wt % or less, and may be 0.05 wt % or less, or may be 0.025 wt % or less. The surfactant content in the concentrate can be, for example, 0.0001 wt % or more, preferably 0.001 wt % or more, more preferably 0.005 wt % or more, and even more preferably 0.01 wt % or more.

[0113] <Preparation of Polishing Composition> The polishing composition used in the technology disclosed herein may be a single-component type or a multi-component type such as a two-component type. For example, the polishing composition may be configured to prepare a polishing liquid by mixing Part A containing at least abrasive grains among the components of the polishing composition with Part B containing at least a portion of the remaining components, and then mixing and diluting these at an appropriate timing as needed.

[0114] The method for preparing the polishing composition is not particularly limited. For example, the components constituting the polishing composition may be mixed using a well-known mixing device such as a blade mixer, an ultrasonic disperser, or a homomixer. The manner in which these components are mixed is not particularly limited. For example, all the components may be mixed at once, or may be mixed in an appropriately set order.

[0115] <Applications> The polishing composition disclosed herein is used for polishing silicon wafers, and can be preferably applied, for example, to a polishing step of silicon wafers. Prior to the polishing step with the polishing composition disclosed herein, the silicon wafer may be subjected to a general treatment that can be applied to silicon wafers in a step upstream of the polishing step, such as lapping or etching.

[0116] The polishing composition disclosed herein is effective when used in the final polishing step of silicon wafers or the polishing step immediately preceding it, and its use in the final polishing step is particularly preferred. Here, the final polishing step refers to the final polishing step in the manufacturing process of the target object (i.e., a step in which no further polishing is performed after that step). The polishing composition disclosed herein may also be used in a polishing step upstream of the final polishing step (a preliminary polishing step between the rough polishing step and the final polishing step, which typically includes at least a primary polishing step and may further include secondary, tertiary, etc. polishing steps), for example, a polishing step performed immediately preceding the final polishing.

[0117] The polishing composition disclosed herein is effective, for example, when applied to polishing (typically finish polishing or polishing immediately before finish polishing) of silicon wafers that have been prepared in an upstream process to have a surface roughness of 0.01 nm to 100 nm. Application to finish polishing is particularly preferred. The surface roughness Ra of a silicon wafer can be measured, for example, using a laser scanning surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement System Inc.

[0118] <Polishing> The polishing composition disclosed herein can be used for polishing silicon wafers, for example, in an embodiment including the following steps. A preferred embodiment of a method for polishing silicon wafers using the polishing composition disclosed herein is described below. That is, a polishing liquid containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include adjusting the concentration (e.g., diluting), adjusting the pH, or the like of the polishing composition to prepare the polishing liquid. Alternatively, the polishing composition may be used as is as the polishing liquid.

[0119] Next, the polishing liquid is supplied to the silicon wafer, and polishing is performed by a conventional method. For example, when performing finish polishing of a silicon wafer, typically, the silicon wafer that has undergone a lapping process is set in a general polishing device, and the polishing liquid is supplied to the surface to be polished of the silicon wafer through the polishing pad of the polishing device. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface to be polished of the silicon wafer, and the two are moved relatively (for example, rotated). Polishing of the silicon wafer is completed through this polishing process.

[0120] The polishing pad used in the polishing step is not particularly limited. For example, a polishing pad of a foamed polyurethane type, a nonwoven fabric type, a suede type, or the like can be used. Each polishing pad may contain abrasive grains or may not contain abrasive grains. Usually, a polishing pad that does not contain abrasive grains is preferably used.

[0121] Silicon wafers polished with the polishing composition disclosed herein are typically cleaned. Cleaning can be performed using an appropriate cleaning solution. The cleaning solution used is not particularly limited, and for example, SC-1 cleaning solution (ammonium hydroxide (NH )) commonly used in the semiconductor field can be used. ４ OH) and hydrogen peroxide (H ２ O ２ ) and water (H ２ O), SC-2 cleaning solution (HCl and H ２ O ２ and H ２The temperature of the cleaning liquid may be, for example, in the range of room temperature (typically about 15°C to 25°C) or higher, up to about 90°C. From the viewpoint of improving the cleaning effect, a cleaning liquid at about 50°C to 85°C may be preferably used.

[0122] As described above, the technology disclosed herein can include a method for manufacturing a polished product (e.g., a method for manufacturing a silicon wafer) that includes a polishing step (preferably finish polishing) by any of the polishing methods described above, and the provision of a polished product (e.g., a silicon wafer) manufactured by the method.

[0123] The matters disclosed in this specification include the following: [1] A polishing composition used for polishing silicon wafers, comprising abrasive grains and a water-soluble polymer P. Ａ a basic compound and water, Ａ [2] The polishing composition according to the above item [1], which contains silica particles as the abrasive grains. [3] The water-soluble polymer P Ａ [4] The polishing composition according to the above [1] or [2], further comprising a water-soluble polymer different from the water-soluble polymer P. Ａ [5] The polishing composition according to any one of the above [1] to [3], further comprising two or more water-soluble polymers different from the water-soluble polymer P. Ａ [6] The polishing composition according to any one of the above [1] to [4], wherein the water-soluble polymer P is a copolymer containing the structural unit A and a structural unit B that is substantially not anionic. Ａ [7] The polishing composition according to the above [5], wherein the water-soluble polymer P is a block copolymer. ＡThe polishing composition according to [5] or [6] above, which contains, as the structural unit B, at least a structural unit derived from any one monomer selected from the group consisting of a nitrogen atom-containing monomer, a vinyl alcohol-based monomer, an allyl alcohol-based monomer, a butylene-based monomer, an aromatic vinyl-based monomer, an acrylic acid ester-based monomer, and an ethylene glycol-based monomer. [8] The polishing composition according to any one of [1] to [7] above, which further contains a surfactant.

[0124] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" representing content and concentration are by weight unless otherwise specified.

[0125] <List of abbreviations> [Monomers] ACMO: N-acryloylmorpholine AMPS: 2-acrylamido-2-methylpropanesulfonic acid NIPAM: N-isopropylacrylamide DEAM: N,N-diethylacrylamide VB-PEO: p-vinylbenzyl methoxypolyoxyethylene ether (number of oxyethylene repeating units: ≒ 13)

[0126] [Water-soluble polymer] ac-PVA: acetalized polyvinyl alcohol PACMO: polyacryloylmorpholine HEC: hydroxyethyl cellulose

[0127] Experimental Example 1 Preparation of Polishing Composition Example 1 Abrasive grains, water-soluble polymer P Ａ A concentrated solution of the polishing composition according to Example 1 was prepared by mixing a basic compound, a water-soluble polymer, a surfactant, and deionized water. Colloidal silica (average primary particle size: 25 nm) was used as the abrasive grains. Ammonia was used as the basic compound. Water-soluble polymer P Ａ The copolymer is a copolymer of ACMO and AMPS in a molar ratio of 90:10, with a Mw of about 7.0 × 10 ４ The water-soluble polymer used was a block copolymer having a Mw of approximately 1.0 × 10 ４The surfactant used was polyoxyethylene decyl ether (C10EO5) with an ethylene oxide addition mole number of 5. The resulting concentrated polishing composition was diluted 20 times by volume with deionized water to a concentration of 0.2% abrasive grains, 0.005% basic compound, and 0.005% water-soluble polymer P. Ａ A polishing composition containing 0.008% of the surfactant, 0.005% of ac-PVA, and 0.001% of surfactant was obtained. The pH of this polishing composition was about 10.1.

[0128] (Examples 2 to 4) Water-soluble polymer P used in Example 1 Ａ The water-soluble polymer P having the structure shown in Table 1 (molar ratio of ACMO and AMPS, arrangement of structural units, and Mw) Ａ Polishing compositions according to the respective examples were obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed.

[0129] (Comparative Example 1) Water-soluble polymer P of Example 1 Ａ Instead, Mw is 3.5 × 10 ５ A polishing composition according to Comparative Example 1 was obtained in the same manner as in Example 1, except that PACMO of the above formula was used. Table 1 summarizes the outline of the polishing compositions according to each example of Experimental Example 1.

[0130] <Polishing of Silicon Wafer> A commercially available silicon single crystal wafer (conductivity type: P-type, crystal orientation: <100>, COP (Crystal Originated Particle)-free) having a diameter of 300 mm after lapping and etching was pre-polished under the following polishing condition 1 to prepare a silicon wafer. The pre-polishing was carried out using a polishing solution containing 1.0% abrasive grains (colloidal silica having an average primary particle size of 35 nm) and 0.068% potassium hydroxide in deionized water.

[0131] [Polishing condition 1] Polishing device: Single-wafer polishing device manufactured by Okamoto Machine Tool Works, model "PNX-332B" Polishing load: 20 kPa Rotation speed of surface plate: 20 rpm Rotation speed of head (carrier): 20 rpm Polishing pad: Product name "SUBA400" manufactured by Nitta DuPont Polishing liquid supply rate: 1.0 L / min Polishing liquid temperature: 20°C Surface plate cooling water temperature: 20°C Polishing time: 3 min

[0132] The polishing compositions according to the examples prepared above were used as polishing liquids to polish the silicon wafers that had been pre-polished as described above under the following polishing conditions 2.

[0133] [Polishing condition 2] Polishing device: Single-wafer polishing device manufactured by Okamoto Machine Tool Works, model "PNX-332B" Polishing load: 20 kPa Rotation speed of surface plate: 52 rpm Rotation speed of head (carrier): 50 rpm Polishing pad: Product name "POLYPAS275NX" manufactured by Fujibo Ehime Co., Ltd. Supply rate of polishing liquid: 1.5 L / min Temperature of polishing liquid: 20°C Temperature of surface plate cooling water: 20°C

[0134] The polished silicon wafer was removed from the polishing machine and washed for 60 seconds with a cleaning solution of ozone water (0.002%) using a single wafer cleaning machine. ４ OH (29%): H ２ O ２ The silicon wafer was then cleaned for 110 seconds using a cleaning solution of 2:5.3:48 (volume ratio) of ozone water (31%) and deionized water (DIW) and a brush (SC-1 cleaning). This was followed by a 20-second cleaning with ozone water and a 15-second cleaning with hydrofluoric acid, for a total of three cleaning sets. After further cleaning for 20 seconds with ozone water, the silicon wafer was dried.

[0135] <Measurement of Defects (LPD-N)> The number of defects (number of LPD-N) present on the surface of the silicon wafer after cleaning was measured using a wafer inspection device manufactured by KLA-Tencor Corporation, product name "Surfscan SP5," in the DC mode of the device. The measured number of LPD-N was converted into a relative value, with the number of LPD-N in Comparative Example 1 taken as 100%. Furthermore, when the number of LPD-N was 80% or less of that in Comparative Example 1, it was evaluated as "A," when it was more than 80% but less than 100%, it was evaluated as "B," and when it was 100% or more, it was evaluated as "C." The results are shown in the "LPD-N" column in Table 1.

[0136] <Haze Measurement> The haze (ppm) of the silicon wafer surface after cleaning was measured in DW2O mode using a wafer inspection device manufactured by KLA Tencor Corporation under the trade name "Surfscan SP5." The results were converted into relative values ​​(haze) with the haze value of Comparative Example 1 taken as 100%. Compared to Comparative Example 1, a case where the haze was less than 100% was evaluated as "A," a case where it was 100% or more and 105% or less was evaluated as "B," and a case where it was more than 105% was evaluated as "C." The results are shown in the "Haze" column in Table 1. A smaller haze value indicates a greater haze improvement effect.

[0137]

[0138] As shown in Table 1, the water-soluble polymer P containing the structural unit A derived from AMPS Ａ The polishing compositions of Examples 1 to 4 using the water-soluble polymer P suppressed an increase in haze and reduced the number of defects compared to the polishing composition of Comparative Example 1 using a polymer not containing the structural unit A derived from AMPS. Ａ The above effect was also obtained when

[0139] Experimental Example 2 Production of Polishing Composition Example 5 Abrasive grains, water-soluble polymer P ＡA concentrated solution of the polishing composition of Example 5 was prepared by mixing a basic compound, a water-soluble polymer, a surfactant, and deionized water. Colloidal silica (average primary particle size: 25 nm) was used as the abrasive grains. Ammonia was used as the basic compound. Water-soluble polymer P Ａ The copolymer is a copolymer of ACMO and AMPS in a molar ratio of 30:70, with a Mw of about 1.7 × 10 ５ The water-soluble polymer used was a block copolymer having a Mw of approximately 1.0 × 10 ４ The polishing composition concentrate was diluted 20 times by volume with deionized water to a concentration of 0.2% abrasive grains, 0.005% basic compound, and 0.005% water-soluble polymer P. Ａ A polishing composition containing 0.003% of the surfactant, 0.003% of ac-PVA, and 0.001% of surfactant was obtained. The pH of this polishing composition was about 10.1.

[0140] (Example 6) Water-soluble polymer P used in Example 5 Ａ was copolymerized with NIPAM and AMPS in a molar ratio of 20:80, and the Mw was about 5.1 × 10 ４ A polishing composition according to Example 6 was obtained in the same manner as in Example 5, except that the block copolymer was changed to the above.

[0141] (Comparative Example 2) Water-soluble polymer P of Example 5 Ａ Instead, Mw is 3.5 × 10 ５ A polishing composition according to Comparative Example 2 was obtained in the same manner as in Example 5, except that PACMO of the above formula was used. The polishing compositions according to each example of Experimental Example 2 are summarized in Table 2.

[0142] <Polishing of Silicon Wafer> The same type of silicon wafer was polished and cleaned under the same conditions as in Experimental Example 1 above.

[0143] <Measurement of Defects (LPD-N)> The number of LPD-N present on the surface of the silicon wafer after cleaning was measured using the same measurement method as in Experimental Example 1 above. The measured number of LPD-N was converted into a relative value, with the number of LPD-N in Comparative Example 2 taken as 100%. Furthermore, when the number of LPD-N was 80% or less than that of Comparative Example 2, it was evaluated as "A," when it was more than 80% but less than 100%, it was evaluated as "B," and when it was 100% or more, it was evaluated as "C." The results are shown in the "LPD-N" column in Table 2.

[0144] <Haze Measurement> The haze (ppm) of the silicon wafer surface after cleaning was measured using the same measurement method as in Experimental Example 1 above. The obtained results were converted into relative values ​​(haze) with the haze value for Comparative Example 2 taken as 100%. With respect to Comparative Example 2, cases where the haze was less than 100% were evaluated as "A", cases where it was 100% or more and 105% or less were evaluated as "B", and cases where it was more than 105% were evaluated as "C". The results are shown in the "Haze" column in Table 2.

[0145]

[0146] As shown in Table 2, the water-soluble polymer P containing the structural unit A derived from AMPS Ａ The polishing compositions of Examples 5 and 6 containing the structural unit A of AMPS suppressed an increase in haze and reduced the number of defects compared to the polishing composition of Comparative Example 2 using a polymer not containing the structural unit A derived from AMPS. The polishing composition of Example 6 using a water-soluble copolymer containing the structural unit A derived from AMPS and the structural unit B derived from NIPAM showed lower haze and further reduced the number of defects.

[0147] Experimental Example 3 Production of Polishing Composition Example 7 Abrasive grains, water-soluble polymer P Ａ A concentrated solution of the polishing composition of Example 7 was prepared by mixing a basic compound, a water-soluble polymer, a surfactant, and deionized water. Colloidal silica (average primary particle size: 25 nm) was used as the abrasive grains. Ammonia was used as the basic compound. Water-soluble polymer P Ａ The copolymer is a copolymer of ACMO and AMPS in a molar ratio of 30:70, with a Mw of about 1.7 × 10 ５The water-soluble polymer used was a block copolymer with a Mw of approximately 3.5 × 10 ５ and Mw of about 1.0 × 10 ４ The polishing composition concentrate was diluted 20 times by volume with deionized water to a concentration of 0.2% abrasive grains, 0.005% basic compound, and 0.005% water-soluble polymer P. Ａ A polishing composition containing 0.003%, 0.008%, 0.003%, and 0.001% of PACMO, 0.003%, 0.003%, and 0.001% of ac-PVA was obtained. The pH of this polishing composition was about 10.1.

[0148] (Example 8) Water-soluble polymer P Ａ NIPAM and AMPS were copolymerized in a molar ratio of 20:80, and the Mw was about 5.1 × 10 ４ A polishing composition according to Example 8 was obtained in the same manner as in Example 7, except that the block copolymer of the formula (1) was used.

[0149] (Example 9) Water-soluble polymer P Ａ DEAM and AMPS were copolymerized in a molar ratio of 20:80, and the Mw was about 2.6 × 10 ４ A polishing composition according to Example 9 was obtained in the same manner as in Example 7, except that the block copolymer of Example 9 was used.

[0150] (Example 10) Water-soluble polymer P Ａ VB-PEO and AMPS were copolymerized in a molar ratio of 20:80, and the Mw was about 4.3 × 10 ４ A polishing composition according to Example 10 was obtained in the same manner as in Example 7, except that the block copolymer of the formula (I) was used and its concentration was set to 0.005%.

[0151] (Comparative Example 3) Water-soluble polymer P Ａ A polishing composition according to Comparative Example 3 was obtained in the same manner as in Example 7, except that no acrylic acid was used and the amount of ac-PVA used was changed. The polishing compositions according to each example of Experimental Example 3 are summarized in Table 3.

[0152] <Polishing of Silicon Wafer> The same type of silicon wafer was polished and cleaned under the same conditions as in Experimental Example 1 above.

[0153] <Measurement of Defects (LPD-N)> The number of LPD-N present on the surface of the silicon wafer after cleaning was measured using the same measurement method as in Experimental Example 1 above. The measured number of LPD-N was converted into a relative value, with the number of LPD-N in Comparative Example 3 taken as 100%. Furthermore, when the number of LPD-N was 80% or less than that of Comparative Example 3, it was evaluated as "A", when it was more than 80% but less than 100%, it was evaluated as "B", and when it was 100% or more, it was evaluated as "C". The results are shown in the "LPD-N" column in Table 3.

[0154] <Haze Measurement> The haze (ppm) of the silicon wafer surface after cleaning was measured using the same measurement method as in Experimental Example 1 above. The obtained results were converted into relative values ​​(haze) with the haze value for Comparative Example 3 taken as 100%. With respect to Comparative Example 3, cases where the haze was less than 100% were evaluated as "A", cases where it was 100% or more and 105% or less were evaluated as "B", and cases where it was more than 105% were evaluated as "C". The results are shown in the "Haze" column in Table 3.

[0155]

[0156] As shown in Table 3, the water-soluble polymer P containing the structural unit A derived from AMPS Ａ According to the polishing compositions of Examples 7 to 10 containing the water-soluble polymer P Ａ The water-soluble polymer P containing the structural unit A derived from AMPS and the structural unit B derived from NIPAM, DEAM or VB-PEO reduced the number of defects while suppressing an increase in haze compared to the polishing composition of Comparative Example 3 which did not contain Ａ In the polishing compositions of Examples 8 to 10 using the above, the number of defects was further reduced.

[0157] Experimental Example 4 Production of Polishing Composition Example 11 Abrasive grains, water-soluble polymer P Ａ A concentrated solution of the polishing composition of Example 11 was prepared by mixing a basic compound, a water-soluble polymer, a surfactant, and deionized water. Colloidal silica (average primary particle size: 25 nm) was used as the abrasive grains. Ammonia was used as the basic compound. Water-soluble polymer P ＡThe copolymer is a copolymer of NIPAM and AMPS in a molar ratio of 20:80, with a Mw of about 5.1 × 10 ４ The water-soluble polymer used was a block copolymer with a Mw of approximately 2.5 × 10 ５ The surfactant used was HEC with a Mw of approximately 3.0 × 10 ３ The resulting concentrated polishing composition was diluted 20 times by volume with deionized water to a concentration of 0.2% abrasive grains, 0.005% basic compound, and 0.005% water-soluble polymer P. Ａ A polishing composition containing 0.004% of the surfactant, 0.004% of HEC, and 0.002% of surfactant was obtained. The pH of this polishing composition was about 10.1.

[0158] (Comparative Example 4) Water-soluble polymer P Ａ The polishing composition of Comparative Example 4 was obtained in the same manner as in Example 11, except that the amount of HEC used was changed and no additional agent was used. The polishing composition of each example of Experimental Example 4 is summarized in Table 4.

[0159] <Polishing of Silicon Wafer> The same type of silicon wafer was polished and cleaned under the same conditions as in Experimental Example 1 above.

[0160] <Measurement of Defects (LPD-N)> The number of LPD-N present on the surface of the silicon wafer after cleaning was measured using the same measurement method as in Experimental Example 1 above. The measured number of LPD-N was converted into a relative value, with the number of LPD-N in Comparative Example 4 taken as 100%. Furthermore, when the number of LPD-N was 80% or less than that of Comparative Example 4, it was evaluated as "A", when it was more than 80% but less than 100%, it was evaluated as "B", and when it was 100% or more, it was evaluated as "C". The results are shown in the "LPD-N" column in Table 4.

[0161] <Haze Measurement> The haze (ppm) of the silicon wafer surface after cleaning was measured using the same measurement method as in Experimental Example 1 above. The obtained results were converted into relative values ​​(haze) with the haze value for Comparative Example 4 taken as 100%. With respect to Comparative Example 4, cases where the haze was less than 100% were evaluated as "A", cases where it was 100% or more and 105% or less were evaluated as "B", and cases where it was more than 105% were evaluated as "C". The results are shown in the "Haze" column in Table 4.

[0162]

[0163] As shown in Table 4, the water-soluble polymer P containing the structural unit A derived from AMPS Ａ According to the polishing composition of Example 11 containing the water-soluble polymer P Ａ Compared with the polishing composition of Comparative Example 4 not containing any of the compounds, the number of defects was reduced while maintaining the same haze.

[0164] From the above results, it can be seen that in the polishing of silicon wafers, abrasive grains and a water-soluble polymer P containing a structural unit A derived from 2-acrylamido-2-methylpropanesulfonic acid (AMPS) are effective. Ａ It can be seen that a polishing composition containing a basic compound and water can reduce defects (LPD-N) while suppressing an increase in haze.

[0165] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

Claims

1. A polishing composition used for polishing silicon wafers, comprising abrasive grains and a water-soluble polymer P Ａ a basic compound and water, Ａ The polishing composition is a polymer containing a structural unit A derived from 2-acrylamido-2-methylpropanesulfonic acid.

2. The polishing composition according to claim 1, wherein the abrasive grains comprise silica particles.

3. The water-soluble polymer P Ａ The polishing composition according to claim 1 or 2, further comprising a water-soluble polymer different from the above.

4. The water-soluble polymer P Ａ The polishing composition according to claim 1 or 2, further comprising two or more water-soluble polymers different from the above.

5. The water-soluble polymer P Ａ 3. The polishing composition according to claim 1, wherein the structural unit A is a copolymer containing the structural unit B having substantially no anionicity.

6. The water-soluble polymer P Ａ The polishing composition according to claim 5 , wherein is a block copolymer.

7. The water-soluble polymer P Ａ 6. The polishing composition according to claim 5, wherein the structural unit B comprises at least a structural unit derived from any one monomer selected from the group consisting of a nitrogen atom-containing monomer, a vinyl alcohol-based monomer, an allyl alcohol-based monomer, a butylene-based monomer, an aromatic vinyl-based monomer, an acrylic acid ester-based monomer, and an ethylene glycol-based monomer.

8. The polishing composition according to claim 1 or 2, further comprising a surfactant.

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