Polishing composition and polishing method

Abstract

Provided is a polishing composition which is used for polishing surfaces made of a silicon material and which can yield polished surfaces having excellent wettability and a reduced number of defects. The polishing composition is used for polishing surfaces made of a silicon material. The polishing composition comprises abrasive grains, a basic compound, a random copolymer comprising a vinyl alcohol unit and an N-vinylpyrrolidone unit, and a nonionic surfactant. The nonionic surfactant has a molecular weight of less than 3,000. The content α [wt%] of the nonionic surfactant is in the range of 0.00035<α<0.00500.

Description

Polishing composition and polishing method

[0001] The present invention relates to a polishing composition and a polishing method. This application claims priority to Japanese Patent Application No. 2023-161704, filed on September 25, 2023, 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. 7104053 Japanese Patent No. 6801964 Japanese Patent No. 7050684

[0004] Polishing compositions used to polish semiconductor substrates such as silicon wafers and other substrates, for example, polishing compositions used in finish polishing processes (particularly finish polishing processes for semiconductor substrates such as silicon wafers and other substrates), are required to achieve high-quality surfaces after polishing. For example, if the substrate is properly protected by adding a water-soluble polymer to the polishing composition, it is possible to improve the surface quality after polishing, such as by reducing the haze value. On the other hand, the presence of residues of the water-soluble polymer on the substrate surface after polishing can increase defects (e.g., LPD-N (Light Point Defect Non-Cleanable)) during surface inspection of the substrate. Therefore, in polishing using a polishing composition containing a water-soluble polymer, it is necessary to improve surface quality by reducing defects (e.g., LPD-N) on the substrate surface after polishing. For example, Patent Documents 1 to 3 describe polishing compositions containing colloidal silica, ammonia, and a random copolymer of vinyl alcohol and N-vinylpyrrolidone, and evaluate the LPD-N after polishing using the polishing composition.

[0005] Furthermore, in order to obtain a high-quality surface, it is preferable that the polished silicon wafer surface has sufficient wettability. By keeping the polished surface wet with water (with a water film attached), foreign matter in the air can be prevented from directly adhering to the polished surface. A silicon wafer surface having such a surface is likely to obtain a higher-quality surface after cleaning.

[0006] The present invention was created in view of the above circumstances, and aims to provide a polishing composition that can be used to polish a surface made of a silicon material, and that can provide excellent wettability to the surface after polishing and reduce defects, and a polishing method using the polishing composition.

[0007] According to the present specification, there is provided a polishing composition for use in polishing a surface made of a silicon material. The polishing composition comprises abrasive grains, a basic compound, a random copolymer containing vinyl alcohol units and N-vinylpyrrolidone units, and a nonionic surfactant. The molecular weight of the nonionic surfactant is less than 3,000. The content α [wt %] of the nonionic surfactant in the polishing composition is within the range of 0.00035 < α < 0.00500. When a polishing composition comprises abrasive grains, a basic compound, and a random copolymer containing vinyl alcohol units and N-vinylpyrrolidone units, and further contains a nonionic surfactant with a molecular weight of less than 3,000 within the above-mentioned α content range, the polished surface made of a silicon material has excellent wettability and can reduce defects on the surface.

[0008] In some embodiments, the ratio of the content of the nonionic surfactant to the content of the random copolymer containing vinyl alcohol units and N-vinylpyrrolidone units is 0.01 or more and 2.0 or less by weight. In embodiments in which the nonionic surfactant is used in the above ratio relative to the random copolymer, the effects of the technology disclosed herein can be preferably realized.

[0009] In some embodiments, the polishing composition contains silica particles as the abrasive grains. A polishing composition containing silica particles as the abrasive grains tends to provide a polished surface with excellent surface quality.

[0010] The polishing composition disclosed herein can be a concentrate. The polishing composition disclosed herein can be manufactured, distributed, and stored as a concentrate.

[0011] In some embodiments, a polishing method is provided, comprising the step of polishing a surface of a silicon material with the polishing composition, whereby the polished surface of the silicon material has excellent wettability and reduced defects.

[0012] 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.

[0013] <Abrasive Grains (A)> The polishing composition disclosed herein contains abrasive grains. The abrasive grains contribute to improving the polishing rate by mechanically polishing the surface of the object to be polished. The material and properties of the abrasive grains are not particularly limited and can be appropriately selected depending on the purpose and mode of use 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; and carbonates such as calcium carbonate and barium carbonate. 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, etc. Such abrasive grains may be used alone or in combination of two or more types.

[0014] The abrasive grains are preferably inorganic particles, and among these, particles made of metal or semi-metal oxides are preferred, with silica particles being particularly preferred. In polishing compositions that can be used for polishing (e.g., finish polishing) objects having a silicon surface, such as silicon wafers, it is particularly useful to employ silica particles as the abrasive grains. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which substantially only silica particles are used as the abrasive grains. From this perspective, the proportion of silica particles in the total amount of abrasive grains is suitably 90% by weight or more, preferably 95% by weight or more, and more preferably 98% by weight or more (e.g., 99 to 100% by weight).

[0015] 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 an ion exchange method 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.

[0016] The true specific gravity of the silica constituting the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. The upper limit of the true specific gravity of silica is not particularly limited, but is typically 2.3 or less, for example, 2.2 or less. The true specific gravity of the silica particles can be measured by a liquid substitution method using ethanol as a substitution liquid.

[0017] The average primary particle diameter of the abrasive grains (typically silica particles, preferably colloidal silica) is not particularly limited, but is preferably 5 nm or more, more preferably 10 nm or more, from the viewpoint of polishing rate, etc. From the viewpoint of obtaining a higher polishing effect (e.g., effects such as haze reduction and defect removal), the average primary particle diameter is preferably 15 nm or more, more preferably 20 nm or more (e.g., more than 20 nm). Furthermore, from the viewpoint of scratch prevention, etc., the average primary particle diameter of the abrasive grains is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 45 nm or less. From the viewpoint of easily obtaining a surface with a lower haze, in some embodiments, the average primary particle diameter 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.

[0018] 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 / cm３ ) × BET value (m ２ The 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."

[0019] The average secondary particle diameter of the abrasive grains (typically silica particles) is not particularly limited and can be appropriately selected, for example, from a range of about 15 nm to 300 nm. From the viewpoint of improving the polishing rate, the average secondary particle diameter is preferably 30 nm or more, more preferably 35 nm or more. In some embodiments, the average secondary particle diameter may be, for example, 40 nm or more, 42 nm or more, or preferably 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 120 nm or less, more preferably 100 nm or less, even more preferably 70 nm or less, for example, 60 nm or less, or even 50 nm or less.

[0020] 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, a product named "Nanotrac UPA-UT151" manufactured by Nikkiso Co., Ltd.

[0021] The shape (external shape) of the abrasive grains (typically silica particles) 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, silica particles in which most of the particles are peanut-shaped or cocoon-shaped can be preferably used.

[0022] Although not particularly limited, the average value of the long axis / short axis ratio (average aspect ratio) of the abrasive grains (typically silica particles) is, in principle, 1.0 or more, preferably 1.05 or more, more preferably 1.1 or more, and may be 1.2 or more. By increasing the average aspect ratio, a higher polishing rate can be achieved. Furthermore, from the viewpoint of reducing scratches, etc., the average aspect ratio of the abrasive grains (typically silica particles) is preferably 3.0 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and may be 1.4 or less.

[0023] The shape (external shape) and average aspect ratio of abrasive grains (typically silica particles) 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 (abrasive particles, typically silica particles) 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.

[0024] <Basic Compound (B)> The polishing composition disclosed herein contains a basic compound. In this specification, a basic compound refers to a compound that dissolves in water and increases the pH of the aqueous solution. By incorporating a basic compound into the polishing composition, the polishing target can be efficiently polished by its chemical polishing action (alkaline etching). 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 bicarbonates, 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. These basic compounds can be used alone or in combination of two or more.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] <VA-VP Random Copolymer (C)> The polishing composition disclosed herein contains a random copolymer (hereinafter also referred to as a "VA-VP random copolymer") containing vinyl alcohol units (hereinafter also referred to as "VA units") and N-vinylpyrrolidone units (hereinafter also referred to as "VP units"). Here, the VA units are units represented by the following chemical formula: -CH ２ The VA unit refers to a structural unit (repeating unit) represented by the formula -CH(OH)-. VA units can be obtained, for example, by hydrolysis (also known as saponification) of a structural unit formed by vinyl polymerization of a vinyl ester monomer such as vinyl acetate. VP units refer to a structural unit derived from N-vinylpyrrolidone as a monomer in one molecule of the random copolymer. The VA-VP random copolymer can be obtained, for example, by partial or complete saponification of a random copolymer of vinyl acetate and N-vinylpyrrolidone. By using a VA-VP random copolymer having the above chemical structure, the polished surface can be suitably protected while maintaining excellent wettability after polishing. By using the VA-VP random copolymer in combination with a predetermined amount of a low-molecular-weight nonionic surfactant, as described in detail below, the polished surface can be maintained with excellent wettability and reduced surface defects. The VA-VP random copolymer may be used alone, or two or more copolymers having different molar ratios of VA units to VP units or two or more copolymers having different Mws may be used in combination. The VA-VP random copolymer may contain structural units other than VA units and VP units, or may be substantially free of structural units other than VA units and VP units, as long as the functions of the copolymer and the effects of the invention are not significantly impaired.

[0029] The molar ratio (VA / VP) of VA units / VP units in the VA-VP random copolymer is not particularly limited. The molar ratio (VA / VP) can be set within an appropriate range so that the copolymer functions as a random copolymer. In some embodiments, the molar ratio (VA / VP) may be, for example, 50 / 50 or more, 65 / 35 or more, 70 / 30 or more, 75 / 25 or more, 80 / 20 or more, 85 / 15 or more, or 90 / 10 or more (e.g., greater than 90 / 10). In some embodiments, the molar ratio (VA / VP) may be, for example, 99 / 1 or less, 98 / 2 or less, 97 / 3 or less, 95 / 5 or less, or 93 / 7 or less.

[0030] The weight-average molecular weight (Mw) of the VA-VP random copolymer is not particularly limited. Random copolymers containing VA units and VP units can provide sufficient wettability whether the molecular weight is small or large. Although not particularly limited, in some embodiments, the Mw of the VA-VP random copolymer is, for example, 100 × 10 ４ It can be 60×10 ４ In some preferred embodiments, from the viewpoint of concentration efficiency, the Mw is 30×10 ４ or less, for example, 20×10 ４ It may be 10×10 or less. ４ Less than 8 x 10 is also acceptable. ４ Less than 5 x 10 ４ Less than 3 × 10 ４ As the Mw decreases, the dispersion stability of the VA-VP random copolymer tends to improve. ４ or less, 1.8 × 10 ４ It may be less than 1.5 × 10 ４ Less than (e.g., 1.5 x 10 ４ In addition, from the viewpoint of favorably protecting the polished surface and improving wettability after polishing, in some embodiments, the Mw may be, for example, 0.2 × 10 ４ or more, and may be 0.25 × 10 ４Or 0.3 x 10 ４ or more, 0.5 × 10 ４ or more, 0.8 × 10 ４ As the Mw of the VA-VP random copolymer increases, the effect of improving the protection of the object to be polished tends to increase. From this viewpoint, in some preferred embodiments, the Mw is 1.0 × 10 ４ or more (for example, 1.0 × 10 ４ (over 1.5 × 10 ４ or more, 1.8 × 10 ４ or more, 2.0 × 10 ４ or more (e.g., 2.0 × 10 ４ (over 2.3 × 10 ４ or more, 2.5 × 10 ４ or more, 2.8 × 10 ４ More than that is fine.

[0031] The Mw of the water-soluble polymer can be calculated from the value (water-based, polyethylene oxide equivalent) based on aqueous gel permeation chromatography (GPC). The same applies to the Mw of the above VA-VP random copolymer and any water-soluble polymer described below. As a GPC measuring device, it is recommended to use a model "HLC-8320GPC" manufactured by Tosoh Corporation. Measurement can be performed, 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 GMPW ＸＬ Detector: differential refractometer Eluent: 100 mM sodium nitrate aqueous solution Flow rate: 1 mL / min Measurement temperature: 40°C Sample injection volume: 200 μL

[0032] Although not particularly limited, in some embodiments, the content of the VA-VP random copolymer in the polishing composition can be, for example, 0.01 parts by weight or more per 100 parts by weight of abrasive grains (typically silica particles). From the viewpoint of improving wettability, 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, or even 1.5 parts by weight or more, or even 2 parts by weight or more. The content of the VA-VP random copolymer per 100 parts by weight of abrasive grains may, for example, be 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 VA-VP random copolymer per 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, or may be less than 3 parts by weight, or may be 2.5 parts by weight or less. By appropriately setting the amount of the VA-VP random copolymer used within the above range, it is possible to achieve a surface that has excellent wettability after polishing while suitably protecting the polished surface.

[0033] Although not particularly limited, in some embodiments, the ratio (B / C) of the content (B) of the basic compound to the content (C) of the VA-VP random copolymer in the polishing composition can be, for example, 0.01 or more by weight. From the viewpoint of the polishing rate and the like, it is appropriate to set it to 0.1 or more, preferably 0.5 or more, more preferably 1.0 or more, even more preferably 2.0 or more, and may even be 2.5 or more. In some embodiments, the ratio (B / C) may be, for example, 15 or less by weight, or may even be 10 or less. In addition, from the viewpoint of suitably protecting the polished surface and maintaining or improving surface quality, the ratio (B / C) is suitably 7 or less, preferably 5 or less, more preferably 4 or less. By appropriately setting the content of the VA-VP random copolymer and the content of the basic compound so that the ratio (B / C) is within the above range, high surface quality can be obtained.

[0034] <Nonionic surfactant (D) with a molecular weight of less than 3000> The polishing composition disclosed herein contains a nonionic surfactant with a molecular weight of less than 3000. By containing the VA-VP random copolymer and further containing a nonionic surfactant with a molecular weight of less than 3000 in an appropriate concentration range, the polished surface has excellent wettability, and the surface of the object to be polished is suitably protected, thereby reducing defects. Furthermore, by including the nonionic surfactant, haze on the polished surface can be further reduced. The use of a nonionic surfactant is advantageous from the standpoints of low foaming and ease of pH adjustment. Examples of the nonionic surfactant include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyalkylene derivatives (e.g., polyoxyalkylene adducts) such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters; copolymers of multiple types of oxyalkylenes (e.g., diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers); etc. The nonionic surfactants can be used alone or in combination of two or more.

[0035] 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 oleyl ether, polyoxyethylene propylene ...propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, polyoxyethylene propylene glycol, 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, polyoxyethylene hydrogenated castor oil, polyoxyethylene methyl glucoside, polyoxypropylene methyl glucoside, and the like.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.

[0036] The molecular weight of the nonionic surfactant is less than 3000. By using a surfactant with a molecular weight of less than 3000, defects can be reduced. A small molecular weight of the nonionic surfactant is advantageous from the viewpoint of filterability, cleanability, etc. In some preferred embodiments, the molecular weight of the nonionic surfactant is, for example, less than 2500, more preferably less than 2000, even more preferably 1900 or less (e.g., less than 1800), even more preferably 1500 or less, and particularly preferably 1000 or less (e.g., 500 or less). In addition, from the viewpoint of surface activity, etc., the molecular weight of the nonionic surfactant is usually appropriate to be 200 or more, and from the viewpoint of haze reduction effect, etc., it is preferably 250 or more (e.g., 300 or more).

[0037] 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. The GPC measurement conditions may be the same as those for the water-soluble polymer. 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.

[0038] The content α [wt%] of the nonionic surfactant having a molecular weight of less than 3000 in the polishing composition (typically a polishing liquid) is within the range of 0.00035<α<0.00500. When the α is greater than 0.00035, defects can be reduced. Furthermore, when the α is less than 0.00500, excellent wettability and defect reduction effects can be obtained. From this viewpoint, in some preferred embodiments, the α is 0.00050 or more, may be 0.00100 or more, or may be 0.00150 or more. Furthermore, in some preferred embodiments, the α is 0.00400 or less, more preferably 0.00300 or less, even more preferably 0.00250 or less, even more preferably 0.00200 or less, even more preferably 0.00150 or less, particularly preferably 0.00100 or less, and may be 0.00080 or less.

[0039] Although not particularly limited, in some embodiments, the content of the nonionic surfactant having a molecular weight of less than 3000 is typically 20 parts by weight or less per 100 parts by weight of abrasive grains (typically silica particles) from the viewpoints of wettability, defect reduction, cleanability, etc., and may be 10 parts by weight or less, or may be 5 parts by weight or less. From the viewpoint of better achieving both wettability and defect reduction, in some preferred embodiments, the content of the nonionic surfactant per 100 parts by weight of abrasive grains is 4 parts by weight or less, more preferably 3 parts by weight or less, even more preferably 2 parts by weight or less, even more preferably 1 part by weight or less (e.g., less than 1 part by weight), particularly preferably 0.8 parts by weight or less, may be 0.6 parts by weight or less, or may be 0.5 parts by weight or less. From the viewpoint of better demonstrating the defect reduction effect, in some embodiments, the content of the surfactant per 100 parts by weight of abrasive grains is appropriately 0.001 parts by weight or more, may be 0.01 parts by weight or more, or may be 0.1 parts by weight or more. In some preferred embodiments, the content of the nonionic surfactant per 100 parts by weight of abrasive grains is 0.25 parts by weight or more, more preferably 0.3 parts by weight or more, and even more preferably 0.4 parts by weight or more.

[0040] Although not particularly limited, in some embodiments, the ratio (D / C) of the content (D) of the nonionic surfactant having a molecular weight of less than 3000 to the content (C) of the VA-VP random copolymer can be, for example, 0.001 or more by weight. From the viewpoint of defect reduction, etc., it is appropriate to set it to 0.005 or more, preferably 0.01 or more, and may be 0.03 or more, or may be 0.05 or more. From the viewpoint of further reducing defects, in some preferred embodiments, the ratio (D / C) is 0.10 or more, more preferably 0.15 or more, even more preferably 0.20 or more, may be 0.40 or more, may be 0.50 or more, may be 0.60 or more, or may be 0.70 or more. Furthermore, from the viewpoint of wettability, defect reduction, etc., in some embodiments, the ratio (D / C) may be, for example, 10 or less by weight, or may be 5 or less. From the viewpoint of achieving a better balance between wettability and defect reduction, in some preferred embodiments, the ratio (D / C) is 2.0 or less, preferably 1.0 or less (e.g., less than 1.0), more preferably 0.5 or less, even more preferably 0.3 or less, and may be, for example, 0.20 or less.

[0041] <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.

[0042] <Optional Water-Soluble Polymer> Although not particularly limited, for the purpose of improving surface quality, such as further reducing defects, the polishing composition may optionally contain a water-soluble polymer other than the above-mentioned VA-VP random copolymer (also referred to as an "optional water-soluble polymer"), or may be substantially free of the optional water-soluble polymer. As the optional water-soluble polymer, one or more types selected from water-soluble polymers other than random copolymers containing VA units and VP units can be used.

[0043] The type of optional water-soluble polymer is not particularly limited, and those having at least one functional group selected from a cationic group, an anionic group, and a nonionic group can be used. The optional water-soluble polymer may have a hydroxyl group, a carboxyl group, an acyl group, an acyloxy group, a sulfo group, an amide group, a quaternary ammonium structure, a heterocyclic structure, a vinyl structure, a polyoxyalkylene structure, or the like. Examples of the optional water-soluble polymer include cellulose derivatives; starch derivatives; polymers containing oxyalkylene units such as copolymers of ethylene oxide (EO) and propylene oxide (PO); vinyl alcohol-based polymers; polymers containing nitrogen atoms such as polymers containing N-vinyl type monomer units, imine derivatives, and polymers containing N-(meth)acryloyl type monomer units; and polymers containing carboxylic acids (including anhydrides). Specific examples include pullulan, random copolymers and block copolymers of ethylene oxide (EO) and propylene oxide (PO), polyglycerin, polyvinyl alcohol (PVA), acetalized polyvinyl alcohol, butenediol polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfonic acid group-modified polyvinyl alcohol, polyvinyl alcohol polyvinylpyrrolidone graft copolymer, polyvinyl alcohol polyethylene oxide graft copolymer, polyvinyl alcohol polyethylene oxide random copolymer, polyisoprene sulfonic acid, polyvinylsulfonic acid, Examples of the optional water-soluble polymer include sulfonic acid, polyallylsulfonic acid, polyisoamylenesulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polyethylene glycol, polyvinylimidazole, polyvinylcarbazole, polyvinylpyrrolidone, polyvinylacetamide, polyacryloylmorpholine, polyhydroxyethylacrylamide, polyallylamine, glycidol-modified polyallylamine, methyldiallylamine-sulfur dioxide copolymer, polyvinylcaprolactam, polyvinylpiperidine, olefin-maleic acid (anhydride) copolymer, and styrene-maleic acid (anhydride) copolymer. The optional water-soluble polymer may be used alone or in combination of two or more. From the viewpoint of simplifying the composition, the polishing composition disclosed herein does not necessarily contain the optional water-soluble polymer.

[0044] The Mw of the water-soluble polymer is not particularly limited. In some embodiments, the Mw of the water-soluble polymer is, for example, about 200×10 ４ It may be less than or equal to approximately 100×10 ４ Less than 70 x 10 ４ Less than 60 x 10 ４ Less than 50 x 10 ４ Less than 40 x 10 ４ Less than 30 x 10 ４ In order to improve the surface quality, in some embodiments, the Mw may be, for example, 1.0 × 10 ４ It may be 5×10 or more. ４ More than 10 x 10 ４ or more (for example, 10 x 10 ４ In some embodiments, the Mw may be 15×10 ４ The above is appropriate, 20 x 10 ４ or more, 25 × 10 ４ More than 30 x 10 ４ or more (e.g., 30 x 10 ４ Super) is also acceptable.

[0045] In embodiments using an optional water-soluble polymer, the content of the optional water-soluble polymer in the polishing composition can be appropriately set within a range that does not significantly impair the effects of the present invention. Furthermore, the polishing composition disclosed herein can be implemented in an embodiment that is substantially free of any optional water-soluble polymer. From this perspective, in embodiments in which the polishing composition contains an optional water-soluble polymer and embodiments in which the polishing composition is substantially free of any optional water-soluble polymer, the proportion of the optional water-soluble polymer in the total water-soluble polymers contained in the polishing composition may be 80 wt % or less, 50 wt % or less (e.g., less than 50 wt %), 30 wt % or less, 20 wt % or less, 10 wt % or less, or 5 wt % or less (e.g., 0 to 5 wt %).

[0046] <Optional Surfactant> Although not particularly limited, the polishing composition may optionally contain a surfactant (optional surfactant) other than a nonionic surfactant having a molecular weight of less than 3000, or may be substantially free of such optional surfactant, as long as the effects of the invention are not significantly impaired. Examples of optional surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants having a molecular weight of 3000 or more. The optional surfactants may be used alone or in combination of two or more.

[0047] In embodiments in which an optional surfactant is used, the content of the optional surfactant in the polishing composition can be appropriately set within a range that does not significantly impair the effects of the present invention. Furthermore, the polishing composition disclosed herein can be implemented in an embodiment in which the optional surfactant is substantially absent. From this perspective, in embodiments in which the polishing composition contains an optional surfactant and embodiments in which the polishing composition is substantially absent, the proportion of the optional surfactant in the total surfactants contained in the polishing composition may be 50 wt % or less (e.g., less than 50 wt %), 30 wt % or less, 20 wt % or less, 10 wt % or less, or 5 wt % or less (e.g., 0 to 5 wt %).

[0048] <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.

[0049] 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 salt, potassium salt, lithium salt, 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, lithium salts, etc.) and ammonium salts of inorganic acids.

[0050] 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.

[0051] 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 substrate (e.g., a silicon wafer), the surface of the substrate 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.

[0052] <pH> The pH of the polishing composition disclosed herein is not particularly limited, and an appropriate pH can be adopted depending on the substrate, etc. 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, from the viewpoint of preventing dissolution of 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.

[0053] In the technology disclosed herein, the pH of the polishing composition is measured using a pH meter (for example, a glass electrode hydrogen ion concentration indicator (Model F-72) manufactured by Horiba, Ltd.). More specifically, a three-point calibration is performed 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)), and then the glass electrode is placed in the polishing composition to be measured for 2 minutes or more. After the pH of the polishing composition has stabilized, the pH of the polishing composition is measured.

[0054] <Polishing Liquid> The polishing composition disclosed herein is typically supplied to the surface of a substrate in the form of a polishing liquid containing the polishing composition, and is used to polish the substrate. The polishing liquid can be prepared, for example, by diluting any of the polishing compositions disclosed herein (typically with water). Alternatively, the polishing composition can be used as a polishing liquid as is. Another example of a polishing liquid containing the polishing composition disclosed herein is a polishing liquid obtained by adjusting the pH of the composition.

[0055] The content of abrasive grains (typically silica particles) in the polishing liquid is not particularly limited, and is, for example, 0.005 wt% or more, preferably 0.01 wt% or more, more preferably 0.03 wt% or more, even more preferably 0.05 wt% or more, and may be 0.08 wt% or more, or even 0.10 wt% or more (e.g., greater than 0.10 wt%). 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, for example, 1 wt% or less, 0.5 wt% or less, 0.4 wt% or less, or 0.3 wt% or less. This makes it easier to maintain surface quality.

[0056] The content of the basic compound in the polishing liquid is not particularly limited. From the viewpoint of improving the polishing rate, etc., it is usually appropriate for the content to be 0.0005 wt % or more, preferably 0.001 wt % or more, more preferably 0.003 wt % or more, and even more preferably 0.005 wt % or more (e.g., more than 0.005 wt %). Furthermore, from the viewpoint of improving surface quality (e.g., reducing haze), etc., it is appropriate for the content to be less than 0.1 wt %, preferably less than 0.05 wt %, and even more preferably less than 0.03 wt % (e.g., less than 0.025 wt %, or even less than 0.01 wt %).

[0057] From the viewpoint of improving wettability, the content of the VA-VP random copolymer in the polishing liquid may be, for example, 0.0001 wt % or more, and typically 0.0005 wt % or more is appropriate. In some preferred embodiments, the content is 0.001 wt % or more, for example, 0.002 wt % or more, or even 0.0025 wt % or more. The upper limit of the content of the VA-VP random copolymer is not particularly limited and can be, for example, 0.05 wt % or less. From the viewpoint of stability at the concentrated liquid stage, polishing rate, cleanability, and the like, in some embodiments, the content of the VA-VP random copolymer is preferably 0.03 wt % or less, more preferably 0.015 wt % or less, and even more preferably 0.01 wt % or less. The polishing liquid disclosed herein can also be preferably implemented in an embodiment in which the content of the VA-VP random copolymer is, for example, 0.008 wt % or less, 0.006 wt % or less, or 0.004 wt % or less.

[0058] The content of the nonionic surfactant having a molecular weight of less than 3,000 in the polishing liquid is within the range described above as the content α.

[0059] <Concentrate> 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 substrate. 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 a desired time to prepare a polishing liquid (working slurry), which can then be supplied to a substrate. The dilution can be performed, for example, by adding water to the concentrated liquid and mixing.

[0060] 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 (e.g., more than 1% by weight).

[0061] In some embodiments, the content of the basic compound in the concentrate can be, for example, less than 15 wt%. From the viewpoint of storage stability, etc., the content is usually preferably 10 wt% or less (e.g., less than 10 wt%), more preferably 3 wt% or less, and may be 1 wt% or less (e.g., less than 1 wt%), or even 0.5 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 0.05 wt% or more, and even more preferably 0.1 wt% or more.

[0062] In some embodiments, the total content of water-soluble polymers in the concentrate (which may be the content of the VA-VP random copolymer) 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.

[0063] In some embodiments, the surfactant content in the concentrate (e.g., the content of nonionic surfactants having a molecular weight of less than 3000) can be, for example, 0.25% by weight or less, preferably 0.15% by weight or less, more preferably 0.1% by weight or less, and may be 0.05% by weight or less, or may be 0.025% by weight or less. Also, the surfactant content in the concentrate (e.g., the content of nonionic surfactants having a molecular weight of less than 3000) can be, for example, 0.0001% by weight or more, preferably 0.001% by weight or more, more preferably 0.005% by weight or more, and even more preferably 0.01% by weight or more.

[0064] <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.

[0065] 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.

[0066] <Applications> The polishing composition disclosed herein is suitable for polishing a surface made of a silicon material (typically, polishing a silicon wafer). Specific examples of silicon materials include silicon single crystal, amorphous silicon, and polysilicon. The polishing composition disclosed herein can be particularly preferably used for polishing a surface made of silicon single crystal (for example, polishing a silicon wafer).

[0067] The polishing composition disclosed herein can be preferably applied to a polishing process of a substrate (e.g., a silicon wafer). Before the polishing process using the polishing composition disclosed herein, the substrate may be subjected to a general treatment that can be applied to a substrate in a process upstream of the polishing process, such as lapping or etching.

[0068] The polishing composition disclosed herein is effective when used in the final polishing step of a substrate (e.g., a silicon wafer) or in the polishing step immediately preceding it, and is particularly preferably used in the final polishing step. Here, the final polishing step refers to the final polishing step in the manufacturing process of the 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 step.

[0069] The polishing composition disclosed herein is effective, for example, for polishing (typically finish polishing or polishing immediately before finish polishing) 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 the substrate can be measured, for example, using a laser scanning surface roughness meter "TMS-3000WRC" manufactured by Schmitt Measurement Systems Inc.

[0070] <Polishing> The polishing composition disclosed herein can be used to polish a substrate, for example, in an embodiment including the following steps. A preferred embodiment of a method for polishing a silicon wafer as a substrate 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 the polishing liquid as is.

[0071] Next, the polishing liquid is supplied to the substrate, and polishing is performed by a conventional method. For example, when performing finish polishing of a silicon wafer, typically, a silicon wafer that has undergone a lapping process is set in a general polishing device, and a 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 substrate is completed through this polishing process.

[0072] 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.

[0073] A substrate polished with the polishing composition disclosed herein is 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 ２Examples of cleaning solutions that can be used include an ozone water cleaning solution, a mixture of ozone water and ozone water, and a hydrofluoric acid cleaning solution. The temperature of the cleaning solution can be set to, for example, a range from room temperature (typically about 15°C to 25°C) to about 90°C. From the viewpoint of improving the cleaning effect, a cleaning solution of about 50°C to 85°C can be preferably used.

[0074] 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.

[0075] The matters disclosed by this specification include the following. [1] A polishing composition used for polishing a surface made of a silicon material, comprising: abrasive grains; a basic compound; a random copolymer containing vinyl alcohol units and N-vinylpyrrolidone units; and a nonionic surfactant, wherein the molecular weight of the nonionic surfactant is less than 3,000; and the content α [wt %] of the nonionic surfactant is within the range of 0.00035 < α < 0.00500. [2] The polishing composition according to [1] above, wherein the ratio of the content of the nonionic surfactant to the content of the random copolymer containing vinyl alcohol units and N-vinylpyrrolidone units is 0.01 or more and 2.0 or less by weight. [3] The polishing composition according to [1] or [2] above, comprising silica particles as the abrasive grains. [4] A concentrated solution of the polishing composition according to any of [1] to [3] above. [5] A polishing method comprising polishing a surface made of a silicon material with the polishing composition according to any one of [1] to [4] above.

[0076] 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 "%" are by weight unless otherwise specified.

[0077] <Preparation of Polishing Composition> (Examples 1 to 3, Comparative Examples 2 and 3) Abrasive grains, a basic compound, a water-soluble polymer, a surfactant, and deionized water were mixed to prepare a concentrated solution of the polishing composition according to each example. Colloidal silica with an average primary particle size of 25 nm was used as the abrasive grains. Ammonia was used as the basic compound. A water-soluble polymer having a Mw of about 3.0 x 10 and containing vinyl alcohol units and N-vinylpyrrolidone units was used as the water-soluble polymer. ４ A random copolymer (poly(VA-r-VP)) having the formula (I) was used. Polyoxyethylene decyl ether (C10EO5) having 5 moles of ethylene oxide added was used as the surfactant. The resulting concentrated polishing composition was diluted 40 times by volume with deionized water to obtain polishing compositions according to each example having an abrasive concentration of 0.13%, a basic compound concentration of 0.01%, a poly(VA-r-VP) concentration of 0.003%, and a C10EO5 concentration as shown in Table 1.

[0078] (Example 4) A random copolymer (poly(VA-r-VP)) having a Mw of about 3,000 and containing vinyl alcohol units and N-vinylpyrrolidone units was used as the water-soluble polymer. Otherwise, a polishing composition according to this example was prepared in the same manner as in Example 2.

[0079] (Comparative Examples 1, 4 to 5) Except for changing the type of water-soluble polymer and the type of surfactant, polishing compositions according to each example were prepared in the same manner as in Example 2. In Table 1, HEC represents hydroxyethyl cellulose, PEO-PPO-PEO represents a PEO-PPO-PEO block copolymer with an Mw of 3000, and C12EO18SO3NH4 represents ammonium polyoxyethylene lauryl ether sulfate with an ethylene oxide addition mole number of 18.

[0080] <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 that had been subjected to lapping and etching was pre-polished under the following polishing condition 1. The pre-polishing was carried out using a polishing solution containing 0.6% abrasive grains (colloidal silica having an average primary particle size of 35 nm) and 0.08% tetramethylammonium hydroxide (TMAH) in deionized water.

[0081] [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: 2 min

[0082] The polishing compositions according to the respective examples prepared above were used as polishing liquids to polish the silicon wafers after the pre-polishing described above under the following polishing conditions 2, and subsequently under the polishing conditions 3.

[0083] [Polishing condition 2] Polishing device: Single-wafer polishing device manufactured by Okamoto Machine Tool Works, model "PNX-332B" Polishing load: 16 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 Polishing time: 2 min

[0084] [Polishing condition 3] 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 Polishing time: 2 min

[0085] <Water-repellent distance measurement> When the polished silicon wafer was unloaded, the longest distance (water-repellent distance) (mm) in the radial direction of the water-repellent region from the wafer edge was measured. When the water-repellent distance (mm) was 20 mm or less, it was judged as "Good" (pass), and when the water-repellent distance was more than 20 mm, it was judged as "Poor" (fail). The results are shown in the corresponding columns in Table 1.

[0086] <Cleaning> The polished silicon wafer removed from the polishing apparatus was subjected to a single-wafer cleaning process in which the wafer was cleaned with an ozone water cleaning solution (60 seconds), then cleaned with an SC-1 cleaning solution and a brush (110 seconds), and then cleaned with an ozone water cleaning solution (20 seconds) and a hydrofluoric acid cleaning solution (15 seconds) in one set, for a total of 15 sets, and then further cleaned with an ozone water cleaning solution (20 seconds). The silicon wafer was then dried.

[0087] <LPD-N Measurement> The number of LPD-N particles 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 Oblique mode of the device, and judged according to the following criteria. ⊚: The number of LPD-N particles was 100 or less. ◯: The number of LPD-N particles was more than 100 but not more than 500. ×: The number of LPD-N particles was more than 500. ⊚ and ◯ were judged as pass, and × was judged as fail. The results are shown in the relevant columns in Table 1.

[0088]

[0089] As shown in Table 1, in Examples 1 to 4, which used polishing compositions containing abrasive grains, a basic compound, a random copolymer containing VA units and VP units, and a nonionic surfactant with a molecular weight of less than 3000, and in which the content of the nonionic surfactant was more than 0.00035% but less than 0.005%, the water-repellent distance was 20 mm or less, the number of LPD-N particles was 500 or less, and the wettability was excellent, and the number of defects was small. On the other hand, in Comparative Example 1, in which HEC was used as the water-soluble polymer, both wettability and defects were inferior to those of the Examples. Furthermore, in Comparative Example 2, in which the content of the nonionic surfactant was 0.00035% or less, the water-repellent distance was small, but the number of LPD-N particles exceeded 500, and it was not possible to achieve both wettability and reduced defects. In Comparative Example 3, in which the content of the nonionic surfactant was 0.005% or more, the wettability and defect reduction were unacceptable. In Comparative Example 4, in which a nonionic surfactant with a molecular weight of 3,000 was used, the water-repellent distance was small, but the number of LPD-N exceeded 500, and both wettability and defect reduction were not achieved. Furthermore, in Comparative Example 5, in which an anionic surfactant was used instead of a nonionic surfactant, sufficient wettability was not obtained.

[0090] 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 a surface made of a silicon material, comprising: an abrasive grain; a basic compound; a random copolymer containing vinyl alcohol units and N-vinylpyrrolidone units; and a nonionic surfactant, wherein the molecular weight of the nonionic surfactant is less than 3,000; and the content α [wt %] of the nonionic surfactant is within the range of 0.00035<α<0.00500.

2. The polishing composition according to claim 1, wherein the ratio of the content of the nonionic surfactant to the content of the random copolymer containing vinyl alcohol units and N-vinylpyrrolidone units is 0.01 or more and 2.0 or less, on a weight basis.

3. The polishing composition according to claim 1 or 2, which contains silica particles as the abrasive grains.

4. A concentrated solution of the polishing composition according to claim 1 or 2.

5. A polishing method comprising polishing a surface of a silicon material with the polishing composition according to claim 1 or 2.

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