Polishing composition and polishing method

Abstract

Provided is a polishing composition which is used for polishing a surface formed from a silicon material, has excellent wettability of the surface after polishing, and is capable of reducing defects. Provided is a polishing composition for polishing a surface formed from a silicon material. The polishing composition includes abrasive grains, a basic compound, a random copolymer including a vinyl alcohol unit and an N-vinylpyrrolidone unit, and a nonionic surfactant. The molecular weight of the nonionic surfactant is less than 3000. In addition, the content [alpha] (wt%) of the nonionic surfactant is 0.00035 lt. [alpha] [lt]; and the thickness is within the range of 0.00500.

Description

Technical Field

[0001] This invention relates to a grinding composition and a grinding method.

[0002] This application claims priority based on Japanese Patent Application No. 2023-161704, filed on September 25, 2023, the entire contents of which are incorporated herein by reference. Background Technology

[0003] For the surfaces of materials such as metals, semi-metals, non-metals, and their oxides, abrasive compositions are used for precision grinding. For example, the surface of silicon wafers, which are used as components of semiconductor devices, is typically processed into a high-quality mirror finish through a lapping (coarse grinding) step and a polishing (precision grinding) step. The polishing step generally includes a pre-polishing step (preparatory grinding step) and a fine polishing step (final polishing step). Related technical literature on abrasive compositions mainly used in the grinding of semiconductor substrates such as silicon wafers includes Patent Documents 1-3.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 7104053

[0007] Patent Document 2: Japanese Patent No. 6801964

[0008] Patent Document 3: Japanese Patent No. 7050684 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Polishing compositions for polishing semiconductor substrates such as silicon wafers and other substrates, such as polishing compositions for fine polishing steps (especially for fine polishing steps of semiconductor substrates such as silicon wafers and other substrates), require a high-quality surface finish after polishing. For example, when the substrate is properly protected by including a water-soluble polymer in the polishing composition, the surface quality after polishing, such as a reduction in haze value, can be improved. On the other hand, when residues of the aforementioned water-soluble polymer are present on the surface of the polished substrate, they may become a factor increasing defects (e.g., LPD-N, non-cleanable light point defects) during surface inspection of the substrate. Therefore, in polishing using polishing compositions containing water-soluble polymers, it is required to improve surface quality by reducing surface defects (e.g., LPD-N) on the polished substrate. For example, Patent Documents 1-3 disclose a polishing composition containing colloidal silica, ammonia, and a random copolymer containing vinyl alcohol and N-vinylpyrrolidone, and evaluate LPD-N after polishing using this polishing composition.

[0011] Furthermore, to obtain a high-quality surface, it is preferable that the surface of the polished silicon wafer has sufficient wettability. By keeping the polished surface moist (with a film of water adhering to it) with water, it is possible to prevent foreign matter in the air from directly adhering to the polished surface. Silicon wafers with such a surface are easier to clean and obtain a higher quality surface.

[0012] The present invention was made in view of the above circumstances, and its object is to provide a polishing composition and a polishing method using the polishing composition for polishing a surface formed of silicon material, wherein the polished surface has excellent wettability and can reduce defects.

[0013] Solution for solving the problem

[0014] According to this specification, a polishing composition is provided for polishing surfaces formed of silicon material. The polishing composition comprises abrasive particles, an alkaline compound, a random copolymer comprising vinyl alcohol units and N-vinylpyrrolidone units, and a nonionic surfactant. The molecular weight of the nonionic surfactant is less than 3000. Furthermore, the content α [weight %] of the nonionic surfactant in the polishing composition is in the range of 0.00035 < α < 0.00500. Based on the polishing composition comprising abrasive particles, an alkaline compound, and a random copolymer comprising vinyl alcohol units and N-vinylpyrrolidone units, further comprising a nonionic surfactant with a molecular weight less than 3000 within the aforementioned content α range, the polished surface formed of silicon material exhibits excellent wettability and can reduce surface defects.

[0015] In various embodiments, the ratio of the content of the nonionic surfactant to the content of the random copolymer comprising vinyl alcohol units and N-vinylpyrrolidone units, based on weight, is 0.01 or more and 2.0 or less. Using the aforementioned ratio of the nonionic surfactant to the random copolymer preferably achieves the effects of the present disclosure.

[0016] In various methods, the grinding composition includes silica particles as the abrasive grains. According to the grinding composition containing silica particles as abrasive grains, a grinding surface with excellent surface quality can be easily obtained.

[0017] The grinding composition disclosed herein can be a concentrated liquid. The grinding composition disclosed herein can be manufactured, distributed, and stored in the form of a concentrated liquid.

[0018] Among various methods, a polishing method is provided, which includes the step of polishing a surface formed of silicon material using the above-described polishing composition. According to the above polishing method, the polished surface formed of silicon material exhibits excellent wettability and can reduce defects on the surface. Detailed Implementation

[0019] The preferred embodiments of the present invention will now be described. It should be noted that matters necessary for implementing the present invention other than those specifically mentioned in this specification are understood to be design matters based on prior art by those skilled in the art. The present invention can be implemented based on the disclosures in this specification and common technical knowledge in this field.

[0020] <Abrasive grains (A)>

[0021] The grinding composition disclosed herein comprises abrasive grains. These abrasive grains contribute to increasing the grinding rate by mechanically grinding the surface of the object being ground. The material or properties of the abrasive grains are not particularly limited and can be appropriately selected based on the intended use or method of application of the grinding 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 hematite 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 or barium carbonate. Specific examples of organic particles include: polymethyl methacrylate (PMMA) particles or poly(meth)acrylic acid particles (here, (meth)acrylic acid refers to particles containing acrylic acid and methacrylic acid), and polyacrylonitrile particles. Such abrasive grains can be used alone or in combination of two or more.

[0022] As the aforementioned abrasive grains, inorganic particles are preferred, particularly those composed of oxides of metals or semi-metals, and especially silicon dioxide particles. The use of silicon dioxide particles as abrasive grains is particularly significant in abrasive compositions that can be used for polishing (e.g., fine polishing) objects such as silicon wafers having surfaces formed of silicon. The technology disclosed herein, for example, can be preferably implemented by using essentially only silicon dioxide particles as the aforementioned abrasive grains. From this viewpoint, it is suitable for the proportion of silicon dioxide particles in the total amount of abrasive grains to be 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).

[0023] Specific examples of silica particles include colloidal silica, fumed silica, and precipitated silica. Silica particles can be used alone or in combination of two or more. From the viewpoint of easily obtaining a polished surface with excellent quality after grinding, colloidal silica is particularly preferred. As colloidal silica, examples preferably are colloidal silica produced by ion exchange using water glass (Na silicate) as a raw material, and alkoxide-based colloidal silica (colloidal silica produced through the hydrolysis and condensation reaction of alkoxysilanes). Colloidal silica can be used alone or in combination of two or more.

[0024] 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. There is no particular upper limit to the true specific gravity of the silica, but it is generally 2.3 or less, for example, 2.2 or less. The true specific gravity of the silica particles can be determined by a liquid substitution method using ethanol as the substitution liquid.

[0025] The average primary particle size of the abrasive grains (generally silica particles, preferably colloidal silica) is not particularly limited, but from the viewpoint of grinding rate, it is preferably 5 nm or more, more preferably 10 nm or more. From the viewpoint of obtaining higher grinding effects (e.g., reduction of haze, removal of defects, etc.), the above-mentioned average primary particle size is preferably 15 nm or more, more preferably 20 nm or more (e.g., more than 20 nm). Furthermore, from the viewpoint of preventing scratches, the average primary particle size 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 lower haze, the average primary particle size of the abrasive grains can be 43 nm or less, less than 40 nm, less than 38 nm, less than 35 nm, less than 32 nm, or less than 30 nm in various ways.

[0026] It should be noted that in this specification, the average primary particle size refers to the specific surface area (BET value) measured by the BET method, expressed as: average primary particle size (nm) = 6000 / (true density (g / cm³)). 3 )×BET value (m 2 The particle size (BET particle size) is calculated using the formula ( / g). The specific surface area can be measured, for example, using a surface area measuring device manufactured by Micromeritex, trade name "FlowSorb II 2300".

[0027] The average secondary particle size of the abrasive grains (generally silica particles) is not particularly limited, and can be appropriately selected from a range of approximately 15 nm to 300 nm. From the viewpoint of improving the grinding rate, the aforementioned average secondary particle size is preferably 30 nm or more. More preferably, it is 35 nm or more. In various embodiments, the aforementioned average secondary particle size can be, for example, 40 nm or more, or 42 nm or more, preferably 44 nm or more. Furthermore, the aforementioned average secondary particle size is generally advantageous to be below 250 nm, preferably below 200 nm, and more preferably below 150 nm. In various embodiments, the aforementioned average secondary particle size is 120 nm or less, more preferably below 100 nm, and even more preferably below 70 nm, for example, below 60 nm or below 50 nm.

[0028] It should be noted that, 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 abrasive grains can be measured, for example, by using the dynamic light scattering method of the product "NanotracUPA-UT151" manufactured by Nikkiso Corporation.

[0029] The shape (outer shape) of the abrasive particles (generally silica particles) can be spherical or non-spherical. Specific examples of non-spherical particles include: peanut-shaped (i.e., peanut shell-shaped), cocoon-shaped, konpeito-shaped, rugby ball-shaped, etc. For example, it is preferable to use silica particles that are mostly peanut-shaped or cocoon-shaped.

[0030] While not specifically limited, the average aspect ratio (average aspect ratio) of the abrasive grains (generally silica particles) is generally 1.0 or higher, preferably 1.05 or higher, more preferably 1.1 or higher, and can be 1.2 or higher. Increasing the average aspect ratio allows for higher grinding rates. Furthermore, from the viewpoint of reducing scratches, the average aspect ratio of the abrasive grains (generally silica particles) is preferably 3.0 or lower, more preferably 2.0 or lower, more preferably 1.5 or lower, and can be 1.4 or lower.

[0031] The shape (outline) or average aspect ratio of abrasive grains (typically silica particles) can be determined, for example, by observation using an electron microscope. A specific procedure for determining the average aspect ratio involves, for example, using a scanning electron microscope (SEM), drawing the smallest rectangle circumscribed to each individual grain image for a specific number (e.g., 200) of identifiable, individual grain shapes. Then, for each rectangle drawn for each grain image, the length of its longer side (the value of the major diameter) is divided by the length of its shorter side (the value of the minor diameter), and this value is used as the major diameter / minor diameter ratio (ARR). The average aspect ratio is obtained by arithmetically averaging the aspect ratios of the specific number of grains mentioned above.

[0032] <Basic Compound (B)>

[0033] The grinding composition disclosed herein contains an alkaline compound. In this specification, an alkaline compound refers to a compound that dissolves in water and has the function of increasing the pH of the aqueous solution. By including an alkaline compound in the grinding composition, the workpiece can be efficiently ground using its chemical grinding action (alkaline etching). As the alkaline compound, organic or inorganic alkaline compounds containing nitrogen, alkaline compounds containing phosphorus, alkali metal hydroxides, alkaline earth metal hydroxides, various carbonates or bicarbonates, etc., can be used. Examples of nitrogen-containing alkaline compounds include quaternary ammonium compounds, ammonia, amines (preferably water-soluble amines), etc. Examples of phosphorus-containing alkaline compounds include quaternary phosphorus compounds. Such alkaline compounds can be used alone or in combination of two or more.

[0034] 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, imidazoles, triazoles, and other azoles. Specific examples of quaternary phosphonium compounds include tetramethylphosphonium hydroxide and tetraethylphosphonium hydroxide.

[0035] As quaternary ammonium compounds, quaternary ammonium salts (generally strong bases) such as tetraalkylammonium salts and hydroxyalkyltrialkylammonium salts can be used. The anionic component of this quaternary ammonium salt can be, for example, OH-. - F - Cl - ,Br - I - ClO4 -, BH4 - etc. As examples of the above quaternary ammonium compounds, there may be mentioned: quaternary ammonium salts in which the anion is OH - , that is, quaternary ammonium hydroxides. As specific examples of quaternary ammonium hydroxides, there may be mentioned: tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide and tetrahexylammonium hydroxide; hydroxyalkyltrialkylammonium hydroxides such as 2-hydroxyethyltrimethylammonium hydroxide (referred to as choline); etc.

[0036] Among these basic compounds, for example, at least one basic compound selected from alkali metal hydroxides, quaternary ammonium hydroxides and ammonia can be preferably used. Among them, tetraalkylammonium hydroxides (for example, tetramethylammonium hydroxide) and ammonia are more preferable, and ammonia is particularly preferable.

[0037] <VA-VP random copolymer (C)>

[0038] The polishing composition of the present disclosure contains a random copolymer (hereinafter also referred to as "VA-VP random copolymer") of vinyl alcohol units (hereinafter also referred to as "VA units") and N-vinylpyrrolidone units (hereinafter also referred to as "VP units"). Among them, the VA unit refers to a structural unit (repeating unit) represented by the following chemical formula in one molecule of the above random copolymer: -CH2-CH(OH)-. The VA unit can be obtained, for example, by hydrolyzing (also referred to as saponification) a structural unit obtained by vinyl polymerization of a vinyl ester monomer such as vinyl acetate. The VP unit refers to a structural unit derived from N-vinylpyrrolidone as a monomer in one molecule of the above random copolymer. The above VA-VP random copolymer can be obtained, for example, by partially saponifying or completely saponifying a random copolymer of vinyl acetate and N-vinylpyrrolidone. By using the VA-VP random copolymer having the above chemical structure, the polished surface can be appropriately protected while making the polished surface have excellent wettability. By combining the above VA-VP random copolymer with a specified amount of a low molecular weight nonionic surfactant described later, the polished surface has excellent wettability and the defects on the surface can be reduced. The above VA-VP random copolymer can be used alone, or two or more kinds having different molar ratios of VA units and VP units, or two or more kinds having different Mw can be used in combination. It should be noted that within the range not significantly impairing the functions of the copolymer and the effects of the invention, the above VA-VP random copolymer may contain structural units other than VA units and VP units, or may substantially not contain structural units other than VA units and VP units.

[0039] The molar ratio (VA / VP) of VA units to VP units in the aforementioned VA-VP random copolymer is not particularly limited. The molar ratio (VA / VP) can be set within an appropriate range to achieve the function of a random copolymer. In various embodiments, the molar ratio (VA / VP) can 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., exceeding 90 / 10). Furthermore, in various embodiments, the molar ratio (VA / VP) can be, for example, 99 / 1 or less, 98 / 2 or less, 97 / 3 or less, 95 / 5 or less, or 93 / 7 or less.

[0040] The weight-average molecular weight (Mw) of the aforementioned VA-VP random copolymer is not particularly limited. Sufficient wettability can be obtained with both low and high molecular weight random copolymers containing VA and VP units. While not particularly limited, the Mw of the aforementioned VA-VP random copolymer can, for example, be 100 × 10⁻⁶ units. 4 The appropriate value is 60×10. 4 Below. Considering factors such as concentration efficiency, among various preferred methods, the above Mw is 30 × 10. 4 For example, it could be 20×10 4 The following can be 10×10 4 The following can be 8×10 4 The following can be 5×10 4 The following can be 3×10 4 The dispersion stability of the above-mentioned VA-VP random copolymer tends to improve as Mw decreases. Mw can be 2 × 10⁻⁶. 4 The following can be 1.8 × 10 4 The following can be 1.5 × 10 4 The following (e.g., less than 1.5 × 10) 4 Furthermore, from the viewpoint of appropriately protecting the polished surface while improving the wettability after polishing, the aforementioned Mw can be 0.2 × 10⁻⁶ in various methods. 4 The above can be 0.25×10 4 The above can be 0.3×10 4 The above can be 0.5×10 4 The above can be 0.8 × 10 4 The above describes the effect of increasing Mw in the VA-VP random copolymer on protecting the workpiece. From this perspective, among various preferred methods, Mw is 1.0 × 10⁻⁶. 4 Above (e.g., more than 1.0 × 10)4 ), can be 1.5×10 4 The above can be 1.8 × 10 4 The above can be 2.0×10 4 Above (e.g., exceeding 2.0 × 10) 4 ), can be 2.3×10 4 The above can be 2.5 × 10 4 The above can be 2.8 × 10 4 above.

[0041] The molecular weight (Mw) of the water-soluble polymer can be calculated using the value obtained from water-based gel chromatography (GPC) (water-based, converted to polyethylene oxide). The same applies to the Mw of the aforementioned VA-VP random copolymer and any water-soluble polymer described later. The GPC measuring apparatus can be the "HLC-8320GPC" manufactured by TOSOH Corporation. The determination can be performed, for example, under the conditions described below. The same method is used for the examples described later.

[0042] [GPC Measurement Conditions]

[0043] Sample concentration: 0.1% by weight

[0044] Column: TSKgel GMPW XL

[0045] Detector: Differential refractometer

[0046] Eluent: 100mM sodium nitrate aqueous solution

[0047] Flow rate: 1 mL / min

[0048] Measurement temperature: 40℃

[0049] Sample injection volume: 200 μL

[0050] While not particularly limited, in various methods, the content of the aforementioned VA-VP random copolymer in the grinding composition, relative to 100 parts by weight of abrasive grains (generally silica particles), can be, for example, 0.01 parts by weight or more. From the viewpoint of improving wettability, 0.1 parts by weight or more is suitable, preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, 1.5 parts by weight or more, or 2 parts by weight or more. Relative to 100 parts by weight of abrasive grains, the content of the aforementioned VA-VP random copolymer can be, for example, 50 parts by weight or less, or 30 parts by weight or less. From the viewpoint of dispersion stability of the grinding composition, in various methods, the content of the aforementioned VA-VP random copolymer relative to 100 parts by weight of abrasive grains is suitable, preferably 10 parts by weight or less, more preferably 5 parts by weight or less, less than 3 parts by weight, or 2.5 parts by weight or less. By appropriately setting the amount of the aforementioned VA-VP random copolymer used within the above range, the grinding surface can be appropriately protected while achieving a surface with excellent wettability after grinding.

[0051] While not particularly limited, in various embodiments, the ratio (B / C) of the content of the alkaline compound (B) to the content (C) of the aforementioned VA-VP random copolymer in the grinding composition, based on weight, can be set to, for example, 0.01 or more. From the viewpoint of grinding rate, setting it to 0.1 or more is appropriate, preferably 0.5 or more, more preferably 1.0 or more, further preferably 2.0 or more, and can be 2.5 or more. Furthermore, in various embodiments, the aforementioned ratio (B / C), based on weight, can be, for example, 15 or less, and can be 10 or less. Furthermore, from the viewpoint of properly protecting the grinding surface and maintaining or improving surface quality, the aforementioned ratio (B / C) is appropriate to be 7 or less, preferably 5 or less, and more preferably 4 or less. By appropriately setting the content of the aforementioned VA-VP random copolymer and the alkaline compound to the aforementioned range of the ratio (B / C), high surface quality can be obtained.

[0052] <Nonionic surfactants with a molecular weight less than 3000 (D)>

[0053] The grinding composition disclosed herein contains a nonionic surfactant with a molecular weight of less than 3000. By containing the aforementioned VA-VP random copolymer and further containing a nonionic surfactant with a molecular weight of less than 3000 within an appropriate concentration range, the ground surface can have excellent wettability, and the surface of the object being ground can be appropriately protected, reducing defects. Furthermore, by containing the aforementioned nonionic surfactant, the haze of the ground surface can be further reduced. Using a nonionic surfactant is advantageous from the viewpoint of low foaming and ease of pH adjustment. Examples of such nonionic surfactants include: alkylene oxide polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyalkylene derivatives (e.g., polyoxyalkylene adducts) such as polyoxyethylene alkyl ethers, polyoxyethylene alkylbenzene ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glycerol ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters; and copolymers of various alkylene oxides (e.g., diblock copolymers, triblock copolymers, random copolymers, alternating copolymers). The aforementioned nonionic surfactants can be used alone or in combination of two or more.

[0054] Specific examples of nonionic surfactants include: block copolymers of ethylene oxide (EO) and propylene oxide (PO) (diblock copolymers, PEO-PPO-PEO triblock copolymers, PPO-PEO-PPO 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 isodecanyl ether, polyoxyethylene tridecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene oil-based ether, polyoxyethylene phenyl ether, etc. Oxyethylidene octylphenyl ether, polyoxyethylidene nonylphenyl ether, polyoxyethylidene dodecylphenyl ether, polyoxyethylidene styrylated phenyl ether, polyoxyethylidene laurylamine, polyoxyethylidene stearylamine, polyoxyethylidene oleylamine, polyoxyethylidene monolaurate, polyoxyethylidene monostearate, polyoxyethylidene distearate, polyoxyethylidene monooleate, polyoxyethylidene dioleate, polyoxyethylidene sorbitol monolaurate, polyoxyethylidene sorbitol monopalmitate, polyoxyethylidene sorbitol monostearate, polyoxyethylidene sorbitol monostearate, polyoxyethylidene sorbitol monooleate, polyoxyethylidene sorbitol trioleate, polyoxyethylidene sorbitol tetraoleic acid, polyoxyethylidene castor oil, polyoxyethylidene hydrogenated castor oil, polyoxyethylidene methyl glucoside, polyoxyethylidene methyl glucoside, etc. Preferred surfactants include: block copolymers of EO and PO (especially PEO-PPO-PEO type triblock copolymers), random copolymers of EO and PO, and polyoxyethylene alkyl ethers (e.g., polyoxyethylene decyl ether). As a polyoxyethylene alkyl ether, a polyoxyethylene alkyl ether with an EO addition molar number of approximately 1 to 10 (e.g., approximately 3 to 8) is preferably used.

[0055] The aforementioned nonionic surfactants have a molecular weight of less than 3000. Using surfactants with a molecular weight of less than 3000 can reduce defects. The smaller molecular weight of nonionic surfactants is advantageous from the viewpoint of filtration or cleaning properties. Among various preferred embodiments, the molecular weight of the nonionic surfactant is, for example, less than 2500, more preferably less than 2000, even more preferably less than 1900 (e.g., less than 1800), even more preferably less than 1500, and particularly preferably less than 1000 (e.g., less than 500). Furthermore, from the viewpoint of interfacial activity, a molecular weight of 200 or more is generally appropriate for the nonionic surfactant, and from the viewpoint of haze reduction effect, 250 or more (e.g., 300 or more) is preferred.

[0056] The molecular weight of the surfactant can be calculated from the chemical formula or obtained by GPC (converted from aqueous or polyethylene glycol). The GPC measurement conditions can be the same as those for the water-soluble polymers described above. For example, in the case of polyoxyethylene alkyl ethers, it is preferable to use the molecular weight calculated from the chemical formula; in the case of block copolymers of EO and PO, it is preferable to use the weight-average molecular weight obtained by GPC as described above.

[0057] The content α [weight%] of the nonionic surfactant with a molecular weight less than 3000 in the grinding composition (generally a grinding slurry) is in the range of 0.00035 < α < 0.00500. By making α greater than 0.00035, defects can be reduced. Furthermore, by making α less than 0.00500, excellent wettability and defect reduction effects can be obtained. From this viewpoint, in various preferred embodiments, α is 0.00050 or more, 0.00100 or more, and 0.00150 or more. Furthermore, in various preferred embodiments, 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 can be 0.00080 or less.

[0058] While not specifically limited, in various methods, considering factors such as wettability, defect reduction, and cleaning properties, the content of nonionic surfactants with a molecular weight less than 3000 is generally suitable to be 20 parts by weight or less per 100 parts by weight of abrasive particles (generally silica particles), and can be 10 parts by weight or less, or 5 parts by weight or less. Considering both better wettability and defect reduction, in various preferred methods, the content of the aforementioned nonionic surfactant relative to 100 parts by weight of abrasive particles is 4 parts by weight or less, preferably 3 parts by weight or less, more preferably 2 parts by weight or less, further preferably 1 part by weight or less (e.g., less than 1 part by weight), particularly preferably 0.8 parts by weight or less, and can be 0.6 parts by weight or less, or 0.5 parts by weight or less. Considering better defect reduction effects, in various methods, the content of surfactant relative to 100 parts by weight of abrasive particles is suitable to be 0.001 parts by weight or more, and can be 0.01 parts by weight or more, or 0.1 parts by weight or more. In various preferred embodiments, the content of the above-mentioned nonionic surfactant 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, relative to 100 parts by weight of abrasive particles.

[0059] While not particularly limited, in various embodiments, the ratio (D / C) of the content (D) of the nonionic surfactant with a molecular weight less than 3000 to the content (C) of the VA-VP random copolymer, based on weight, can be, for example, 0.001 or more. From the viewpoint of reducing defects, 0.005 or more is appropriate, preferably 0.01 or more, and can be 0.03 or more, or 0.05 or more. From the viewpoint of further reducing defects, in various preferred embodiments, the ratio (D / C) is 0.10 or more, more preferably 0.15 or more, even more preferably 0.20 or more, and can be 0.40 or more, 0.50 or more, 0.60 or more, or 0.70 or more. Furthermore, from the viewpoint of wettability and defect reduction, in various embodiments, the ratio (D / C), based on weight, can be, for example, 10 or less, or 5 or less. From the viewpoint of better balancing wettability and reducing defects, among various preferred embodiments, the above 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, and even more preferably 0.3 or less, for example, 0.20 or less.

[0060] <Water>

[0061] The water contained in the grinding composition of this disclosure is suitable for use as ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. To minimize the obstruction of the function of other components contained in the grinding composition, the water used is preferably characterized by a total content of transition metal ions of less than 100 ppb. The purity of the water can be improved by, for example, removing impurity ions using ion exchange resins, removing foreign matter using filters, distillation, etc. It should be noted that the grinding composition of this disclosure may further contain an organic solvent (lower alcohols, lower ketones, etc.) that is homogeneous with water, depending on requirements. The solvent contained in the grinding composition is preferably 90% by volume or more water, more preferably 95% by volume or more (e.g., 99-100% by volume) water.

[0062] <Any water-soluble polymer>

[0063] While not specifically limited, for the purpose of further reducing defects and improving surface quality, the polishing composition may arbitrarily contain a water-soluble polymer other than the aforementioned VA-VP random copolymer (also referred to as "arbitrary water-soluble polymer"), or may substantially not contain such an arbitrary water-soluble polymer. As the arbitrary water-soluble polymer, one or more water-soluble polymers selected from random copolymers containing VA units and VP units may be used.

[0064] There are no particular restrictions on the type of water-soluble polymer; any water-soluble polymer having at least one functional group selected from cationic, anionic, and nonionic groups can be used. Any water-soluble polymer can be a water-soluble polymer having hydroxyl, carboxyl, acyl, acyloxy, sulfonyl, amide, quaternary ammonium, heterocyclic, vinyl, or polyoxyalkylene structures. Examples of any water-soluble polymer include: cellulose derivatives; starch derivatives; copolymers of ethylene oxide (EO) and propylene oxide (PO) containing oxyalkylene units; vinyl alcohol polymers; polymers containing N-vinyl monomer units, imine derivatives, polymers containing N-(meth)acryloyl monomer units, and other polymers containing nitrogen atoms; and polymers containing carboxylic acids (including anhydrides). Specific examples include: pullulan, random copolymers or block copolymers of ethylene oxide (EO) and propylene oxide (PO), polyglycerol, polyvinyl alcohol (PVA), acetalized polyvinyl alcohol, butene glycol polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, polyvinyl alcohol-polyvinylpyrrolidone graft copolymer, polyvinyl alcohol-ethylene oxide graft copolymer, polyvinyl alcohol-ethylene oxide random copolymer, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoprene sulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polyethylene glycol, polyvinyl imidazole, polyvinyl carbazole, polyvinylpyrrolidone, polyvinyl acetamide, polyacryloylmorpholine, polyhydroxyethyl acrylamide, polyallylamine, glycidyl-modified polyallylamine, methyl diallylamine-sulfur dioxide copolymer, polyvinyl caprolactam, polyvinyl piperidine, olefin-maleic acid (anhydride) copolymer, styrene-maleic acid (anhydride) copolymer, etc. Any water-soluble polymer can be used alone or in combination of two or more. From the viewpoint of simplifying composition, the grinding composition disclosed herein may not contain any water-soluble polymer.

[0065] There are no particular limitations on the Mw of any water-soluble polymer. From the perspective of concentration efficiency, among various methods, the Mw of any water-soluble polymer can be, for example, approximately 200 × 10⁻⁶. 4 The following can be approximately 100×10 4 The following can be 70×10 4 The following can be 60×10 4 The following can be 50x10 4 The following can be 40x10 4 The following can be 30x10 4 The following. Furthermore, from the viewpoint of improving surface quality, in various ways, the aforementioned Mw can be, for example, 1.0 × 10⁻⁶. 4 The above can be 5×10 4 The above can be 10×10 4Above (e.g., more than 10×10) 4 In various configurations, the aforementioned Mw is 15 × 10⁻⁶. 4 The above is appropriate; 20×10 is acceptable. 4 The above can be 25×10 4 The above can be 30×10 4 Above (e.g., more than 30×10) 4 ).

[0066] In the case of using any water-soluble polymer, the content of any water-soluble polymer in the grinding composition can be appropriately set within a range that does not significantly impair the effects of the present invention. Furthermore, the grinding composition of this disclosure can be implemented in a manner that substantially does not contain any water-soluble polymer. From this viewpoint, in both the case of the grinding composition containing any water-soluble polymer and the case of the case that substantially does not contain any water-soluble polymer, the proportion of any water-soluble polymer contained in the grinding composition to the total water-soluble polymer can be 80% by weight or less, 50% by weight or less (e.g., less than 50% by weight), 30% by weight or less, 20% by weight or less, 10% by weight or less, or 5% by weight or less (e.g., 0 to 5% by weight).

[0067] <Any surfactant>

[0068] While not specifically limited, the grinding composition may, to the extent that it does not significantly impair the effect of the invention, arbitrarily contain surfactants other than nonionic surfactants with a molecular weight of less than 3000 (any surfactant), or may substantially not contain such any surfactant. Examples of such any surfactant include: nonionic surfactants with a molecular weight of 3000 or more, anionic surfactants, cationic surfactants, and amphoteric surfactants. Any surfactant may be used alone or in combination of two or more.

[0069] In the use of any surfactant, the content of any surfactant in the abrasive composition can be appropriately set within a range that does not significantly impair the effects of the present invention. Furthermore, the abrasive composition of this disclosure can be implemented substantially without any surfactant. From this viewpoint, in both the method of including any surfactant and the method of substantially not including any surfactant, the proportion of any surfactant in the abrasive composition relative to the total surfactant can be 50% by weight or less (e.g., less than 50% by weight), 30% by weight or less, 20% by weight or less, 10% by weight or less, or 5% by weight or less (e.g., 0 to 5% by weight).

[0070] <Other Ingredients>

[0071] The polishing composition disclosed herein may, as needed, further contain known additives such as organic acids, organic acid salts, inorganic acids, inorganic acid salts, chelating agents, preservatives, and fungicides that can be used in polishing compositions (e.g., polishing compositions for the fine polishing step of silicon wafers), without significantly impairing the effects of the present invention.

[0072] Organic acids and their salts, as well as 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 diphosphonic acid (HEDP) and methanesulfonic acid; organic phosphonic acids such as nitric acid tris(methylene phosphate) (NTMP) and phosphonobutane tricarboxylic acid (PBTC). Examples of organic acid salts include: alkali metal salts (sodium salts, potassium salts, lithium salts, etc.) or ammonium salts of organic acids. Examples of inorganic acids include: hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, hypophosphonic acid, boric acid, and carbonic acid. Examples of inorganic acid salts include alkali metal salts (sodium salts, potassium salts, lithium salts, etc.) or ammonium salts of inorganic acids.

[0073] The aforementioned chelating agents can be used alone or in combination of two or more. Examples of such chelating agents include aminocarboxylic acid chelating agents and organophosphonic acid chelating agents. Suitable examples of chelating agents include ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and diethylenetriaminepentaacetic acid. Examples of such preservatives and fungicides include isothiazolinone compounds, parabens, phenoxyethanol, etc.

[0074] The polishing composition disclosed herein is preferably substantially free of oxidants. When the polishing composition contains an oxidant, the surface of the substrate (e.g., a silicon wafer) will be oxidized to form an oxide film when the polishing composition is supplied to it, which may reduce the polishing rate. Specific examples of the oxidants mentioned in this invention include hydrogen peroxide (H2O2), sodium persulfate, ammonium persulfate, sodium dichloroisocyanurate, etc. It should be noted that "substantially free of oxidants" in polishing composition means that it does not actively contain oxidants. Therefore, polishing compositions that unavoidably contain trace amounts of oxidants from raw materials or manufacturing processes (e.g., the molar concentration of the oxidant 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, further preferably 0.00005 mol / L or less, and particularly preferably 0.00001 mol / L or less) can be included in the concept of "substantially free of oxidants" in this invention.

[0075] <pH value>

[0076] The pH of the polishing composition of the present disclosure is not particularly limited, and an appropriate pH can be adopted according to the substrate or the like. In various modes, the pH of the polishing composition is suitably 8.0 or higher, preferably 8.5 or higher, and more preferably 9.0 or higher. When the pH of the polishing composition becomes higher, the polishing rate tends to increase. On the other hand, from the viewpoints of preventing the dissolution of silica particles and suppressing the reduction of mechanical polishing action, the pH of the polishing composition is generally suitably 12.0 or lower, preferably 11.0 or lower, more preferably 10.8 or lower, and further preferably 10.5 or lower.

[0077] It should be noted that in the technology of the present disclosure, the pH of the polishing composition can be measured by using a pH meter (for example, a glass electrode type hydrogen ion concentration indicator (model F-72) manufactured by Horiba, Ltd.). More specifically, the following method is used: 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)), after performing three-point calibration, insert the glass electrode into the polishing composition to be measured for more than 2 minutes. After the pH of the polishing composition stabilizes, measure the pH of the polishing composition.

[0078] <Polishing liquid>

[0079] The polishing composition of the present disclosure 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 above-mentioned polishing liquid can be, for example, a polishing liquid prepared by diluting any one of the polishing compositions of the present disclosure (typically diluted with water). Alternatively, the polishing composition can be directly used as a polishing liquid. As other examples of the polishing liquid containing the polishing composition of the present disclosure, there can be mentioned: a polishing liquid obtained by adjusting the pH of the composition.

[0080] The content of abrasive particles (generally silica particles) in the polishing slurry is not particularly limited, for example, it is 0.005% by weight or more, preferably 0.01% by weight or more, more preferably 0.03% by weight or more, even more preferably 0.05% by weight or more, and can be 0.08% by weight or more, or 0.10% by weight or more (e.g., more than 0.10% by weight). Higher polishing rates can be achieved by increasing the abrasive particle content. The above-mentioned content is preferably 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less, even more preferably 2% by weight or less, for example, 1% by weight or less, 0.5% by weight or less, 0.4% by weight or less, or 0.3% by weight or less. Therefore, surface quality can be easily maintained.

[0081] The content of alkaline compounds in the polishing slurry is not particularly limited. From the viewpoint of increasing polishing rate, it is generally appropriate to set the above content at 0.0005% by weight or more, preferably 0.001% by weight or more, more preferably 0.003% by weight or more, and even more preferably 0.005% by weight or more (e.g., more than 0.005% by weight). Furthermore, from the viewpoint of improving surface quality (e.g., reducing haze), it is appropriate to set the above content at less than 0.1% by weight, preferably less than 0.05% by weight, more preferably less than 0.03% by weight (e.g., less than 0.025% by weight, and even more preferably less than 0.01% by weight).

[0082] From the viewpoint of improving wettability, the content of the aforementioned VA-VP random copolymer in the polishing slurry is, for example, 0.0001% by weight or more, and typically 0.0005% by weight or more. In various preferred embodiments, the content is 0.001% by weight or more, for example, 0.002% by weight or more, and 0.0025% by weight or more. There is no particular upper limit to the content of the aforementioned VA-VP random copolymer, and it can be, for example, 0.05% by weight or less. From the viewpoint of stability, polishing rate, and cleaning properties in the concentrate stage, the content of the aforementioned VA-VP random copolymer is preferably 0.03% by weight or less, more preferably 0.015% by weight or less, and even more preferably 0.01% by weight or less. The polishing slurry of this disclosure can preferably be implemented with, for example, the content of the aforementioned VA-VP random copolymer being 0.008% by weight or less, 0.006% by weight or less, or 0.004% by weight or less.

[0083] The content of nonionic surfactants with a molecular weight of less than 3000 in the grinding slurry is taken from the range described above as content α.

[0084] <Concentrated Solution>

[0085] The polishing composition disclosed herein can be in a concentrated form (i.e., a concentrated polishing slurry) before being supplied to a substrate. This concentrated polishing composition is advantageous from the viewpoints of convenience in manufacturing, distribution, and storage, as well as cost reduction. The concentration ratio is not particularly limited; for example, it can be set at approximately 2 to 100 times the volume, and typically 5 to 50 times (e.g., 10 to 40 times) is suitable. Such a concentrated slurry can be diluted at a desired time to prepare a polishing slurry (working slurry), which is then supplied to the substrate. This dilution can be performed, for example, by adding water to the concentrated slurry and mixing.

[0086] When the grinding composition (i.e., concentrate) is diluted and used for grinding, the content of abrasive particles in the concentrate can be, for example, set to 25% by weight or less. From the viewpoint of dispersion stability or filterability of the grinding composition, this content is generally preferably 20% by weight or less, more preferably 15% by weight or less. In various preferred embodiments, the content of abrasive particles can be set to 10% by weight or less, or even 5% by weight or less. Furthermore, from the viewpoint of convenience in manufacturing, distribution, and storage, or cost reduction, the content of abrasive particles in the concentrate can be, for example, set to 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).

[0087] In various methods, the content of alkaline compounds in the above-mentioned concentrate can be, for example, set to less than 15% by weight. From the viewpoint of storage stability, the content is generally preferably 10% by weight or less (e.g., less than 10% by weight), more preferably 3% by weight or less, and can be 1% by weight or less (e.g., less than 1% by weight), or 0.5% by weight or less. Furthermore, from the viewpoint of convenience in manufacturing, distribution, and storage, or cost reduction, the content of alkaline compounds in the concentrate can be, for example, set to 0.005% by weight or more, preferably 0.01% by weight or more, more preferably 0.05% by weight or more, and even more preferably 0.1% by weight or more.

[0088] In various methods, the total content of water-soluble polymers in the above-mentioned concentrate (which may be the content of the above-mentioned VA-VP random copolymer) can be, for example, set at 3% by weight or less. From the viewpoint of the filterability or washability of the grinding composition, the above-mentioned content is generally preferably 1% by weight or less, more preferably 0.5% by weight or less. Furthermore, from the viewpoint of convenience in manufacturing, distribution, and storage, or cost reduction, the above-mentioned content is generally appropriate to be 0.001% by weight or more, preferably 0.005% by weight or more, more preferably 0.01% by weight or more.

[0089] In various ways, the content of surfactants in the above-mentioned concentrate (e.g., the content of nonionic surfactants with a molecular weight of less than 3000) may be set at 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 0.025% by weight or less. Furthermore, the content of surfactants in the above-mentioned concentrate (e.g., the content of nonionic surfactants with a molecular weight of less than 3000) may be set at 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.

[0090] <Preparation of Grinding Compositions>

[0091] The grinding composition used in this disclosure can be a single-agent form or a multi-agent form, primarily consisting of two agents. For example, it can be configured by mixing part A, which contains at least abrasive particles from the components of the grinding composition, with part B, which contains at least a portion of the remaining components, and mixing and diluting as needed at appropriate times to prepare a grinding fluid.

[0092] The method for preparing the grinding composition is not particularly limited. For example, known mixing devices such as a wing mixer, an ultrasonic disperser, or a homogenizer can be used to mix the components constituting the grinding composition. The manner in which such components are mixed is not particularly limited; for example, all components can be mixed together, or mixed in a suitably set order.

[0093] <Application>

[0094] The polishing composition disclosed herein is applied to polishing surfaces formed of silicon materials (generally, polishing silicon wafers). Specific examples of silicon materials include monocrystalline silicon, amorphous silicon, and polycrystalline silicon. The polishing composition disclosed herein is particularly preferably used for polishing surfaces formed of monocrystalline silicon (e.g., polishing silicon wafers).

[0095] The polishing composition disclosed herein is preferably applicable to the polishing step of a substrate (e.g., a silicon wafer). Prior to the polishing step using the polishing composition disclosed herein, the substrate can be subjected to general processing that can be applied to the substrate in a step further upstream of the polishing step, such as grinding or etching.

[0096] The polishing composition disclosed herein is effective in fine polishing steps of substrates (e.g., silicon wafers) or in polishing steps immediately preceding them, and is particularly preferred for use in fine polishing steps. In this invention, a fine polishing step refers to the final polishing step in the manufacturing process of the target object (i.e., a step after which no further polishing is performed). The polishing composition disclosed herein is also used in polishing steps upstream of fine polishing (referring to pre-polishing steps between coarse polishing and final polishing steps, typically comprising at least one polishing step, and further comprising two, three, etc. polishing steps), for example, in polishing steps performed immediately preceding fine polishing.

[0097] The polishing composition disclosed herein is effective for polishing (typically fine polishing or polishing immediately preceding it) of silicon wafers whose surface condition has been adjusted to a surface roughness of 0.01 nm to 100 nm via upstream steps. It is particularly preferred for fine polishing. 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 System Inc.

[0098] <Grinding>

[0099] The polishing composition disclosed herein can be used, for example, for polishing a substrate in a manner that includes the following operations. A suitable method for polishing a silicon wafer as a substrate using the polishing composition disclosed herein will be described below.

[0100] That is, a grinding slurry comprising any of the grinding compositions disclosed herein is prepared. The preparation of the grinding slurry may include operations such as adjusting the concentration (e.g., dilution) and pH of the grinding composition. Alternatively, the grinding composition may be used directly as a grinding slurry.

[0101] Next, the polishing slurry is supplied to the substrate, and polishing is performed using conventional methods. For example, in the case of finishing polishing of a silicon wafer, typically, the silicon wafer that has undergone the polishing step is placed in a general polishing apparatus, and polishing slurry is supplied to the polishing target surface of the silicon wafer via the polishing pad of the apparatus. Typically, the polishing slurry is continuously supplied while the polishing pad is pressed against the polishing target surface of the silicon wafer, and the two are moved relative to each other (e.g., rotated). After this polishing step, the polishing of the substrate is completed.

[0102] The abrasive pads used in the above abrasive steps are not particularly limited. Abrasive pads such as polyurethane foam, non-woven fabric, and suede can be used. Each abrasive pad may contain abrasive particles or not. Generally, abrasive pads without abrasive particles are preferred.

[0103] The substrate polished using the polishing composition of this disclosure is typically cleaned. Cleaning can be performed using a suitable cleaning solution. The cleaning solution used is not particularly limited; for example, in the semiconductor field, common cleaning solutions such as SC-1 (a mixture of ammonium hydroxide (NH4OH), hydrogen peroxide (H2O2), and water (H2O)), SC-2 (a mixture of HCl, H2O2, and H2O), ozone water cleaning solution, and hydrofluoric acid cleaning solution can be used. The temperature of the cleaning solution can be set in the range of, for example, room temperature (typically about 15°C to 25°C) to about 90°C. From the viewpoint of improving the cleaning effect, a cleaning solution with a temperature of about 50°C to 85°C is preferred.

[0104] As described above, the technology disclosed herein may include a method for manufacturing an abrasive (e.g., a method for manufacturing a silicon wafer) that includes a polishing step (preferably fine polishing) using any of the above-described grinding methods, and an abrasive (e.g., a silicon wafer) manufactured by the method.

[0105] The following matters are disclosed in this specification.

[0106] [1] A grinding composition for grinding surfaces formed of silicon material,

[0107] The grinding composition comprises: abrasive grains, an alkaline compound, a random copolymer comprising vinyl alcohol units and N-vinylpyrrolidone units, and a nonionic surfactant.

[0108] The aforementioned nonionic surfactants have a molecular weight of less than 3000.

[0109] The content α [weight%] of the aforementioned nonionic surfactant is in the range of 0.00035 < α < 0.00500.

[0110] [2] The grinding composition according to [1], wherein, on a weight basis, the ratio of the content of the aforementioned nonionic surfactant to the content of the aforementioned random copolymer comprising vinyl alcohol units and N-vinylpyrrolidone units is 0.01 or more and 2.0 or less.

[0111] [3] The grinding composition according to [1] or [2] contains silica particles as the aforementioned abrasive grains.

[0112] [4] A concentrate of a grinding composition as described in any one of [1] to [3].

[0113] [5] A grinding method comprising grinding a surface formed of silicon material using a grinding composition as described in any one of [1] to [4].

[0114] Example

[0115] The following describes several embodiments of the present invention; however, it is not intended to limit the invention to the content disclosed in these embodiments. It should be noted that, unless otherwise specified, "parts" and "%" in the following description refer to weight.

[0116] <Preparation of Grinding Compositions>

[0117] (Examples 1-3, Comparative Examples 2-3)

[0118] Concentrated solutions of various grinding compositions were prepared by mixing abrasive particles, an alkaline compound, a water-soluble polymer, a surfactant, and deionized water. Colloidal silica with an average primary particle size of 25 nm was used as the abrasive particles. Ammonia was used as the alkaline compound. The Mw of the compound, which contains vinyl alcohol units and N-vinylpyrrolidone units, was approximately 3.0 × 10⁻⁶. 4 A random copolymer (poly(VA-r-VP)) was used as the water-soluble polymer. Polyoxyethylene decyl ether (C10EO5), with an addition molar amount of 5 by ethylene oxide, was used as the surfactant. By diluting the concentrate of the obtained grinding composition with deionized water to a volume ratio of 40 times, the concentrations of abrasive particles (0.13%), basic compounds (0.01%), poly(VA-r-VP), and C10EO5 were set as shown in Table 1, resulting in grinding compositions for various examples.

[0119] (Example 4)

[0120] A random copolymer (poly(VA-r-VP)) with a Mw of about 3,000, having vinyl alcohol units and N-vinylpyrrolidone units, was used as the water-soluble polymer. The grinding composition of this example was prepared in the same manner as in Example 2.

[0121] (Compare Examples 1 and 4-5)

[0122] Except for changing the type of water-soluble polymer and the type of surfactant, the grinding compositions for 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 a Mw of 3000, and C12EO18SO3NH4 represents polyoxyethylene lauryl ether ammonium sulfate with an ethylene oxide addition molar number of 18.

[0123] Grinding of silicon wafers

[0124] As a substrate, a commercially available single-crystal silicon wafer (conductivity: P-type, crystal orientation: <100>, no COP (Crystal Originated Particle)) with a diameter of 300 mm, which had undergone grinding and etching, was pre-polished according to the grinding conditions described below 1. The pre-polishing was performed using a polishing slurry containing 0.6% abrasive particles (colloidal silica with an average primary particle size of 35 nm) and 0.08% tetramethylammonium hydroxide (TMAH) in deionized water.

[0125] [Grinding Condition 1]

[0126] Grinding device: Single-blade grinding device model "PNX-332B" manufactured by Okamoto Machinery Manufacturing Co., Ltd.

[0127] Grinding load: 20 kPa

[0128] Platform speed: 20 rpm

[0129] Grinding head (carrier) rotation speed: 20 rpm

[0130] Abrasive pad: Manufactured by Nitta DuPont, product name "SUBA400"

[0131] The grinding slurry supply rate is 1.0 L / min.

[0132] The temperature of the polishing slurry: 20℃

[0133] Platform cooling water temperature: 20℃

[0134] Grinding time: 2 min

[0135] Using the polishing compositions prepared in the examples described above as polishing fluid, the pre-polished silicon wafer was polished under polishing conditions 2, and then polished under polishing conditions 3.

[0136] [Grinding Condition 2]

[0137] Grinding device: Single-blade grinding device model "PNX-332B" manufactured by Okamoto Machinery Manufacturing Co., Ltd.

[0138] Grinding load: 16 kPa

[0139] Platform speed: 52 rpm

[0140] Grinding head (carrier) rotation speed: 50 rpm

[0141] Abrasive pad: Product name "POLYPAS275NX" manufactured by FUJIBO Ehime Co., Ltd.

[0142] The grinding slurry supply rate is 1.5 L / min.

[0143] Temperature of the abrasive liquid: 20°C

[0144] Temperature of the platform cooling water: 20°C

[0145] Abrasion time: 2 min

[0146] [Abrasion condition 3]

[0147] Abrasion device: Single - disk abrasion device manufactured by Okamoto Machine Works, model "PNX - 332B"

[0148] Abrasion load: 20 kPa

[0149] Rotational speed of the platform: 52 rpm

[0150] Rotational speed of the grinding head (carrier): 50 rpm

[0151] Abrasion pad: Manufactured by FUJIBO Ehime Co., product name "POLYPAS275NX"

[0152] Supply rate of the abrasive liquid: 1.5 L / min

[0153] Temperature of the abrasive liquid: 20°C

[0154] Temperature of the platform cooling water: 20°C

[0155] Abrasion time: 2 min

[0156] <Water - repellent distance measurement>

[0157] When taking out the abraded silicon wafer, measure the longest distance (water - repellent distance) (mm) in the radial direction of the water - repellent area from the wafer edge. When the water - repellent distance (mm) is 20 mm or less, it is judged as "〇" (qualified); when the water - repellent distance exceeds 20 mm, it is judged as "×" (unqualified). Record the results in the corresponding column of Table 1.

[0158] <Washing>

[0159] Take out the abraded silicon wafer from the abrasion device, use a single - wafer cleaning machine, clean it with ozone - water cleaning solution (60 seconds), then clean it with SC - 1 cleaning solution and a brush (110 seconds), then perform a cleaning process consisting of cleaning with ozone - water cleaning solution (20 seconds) and cleaning with hydrofluoric - acid cleaning solution (15 seconds) as a group, perform 15 groups in total, and further clean it with ozone - water cleaning solution (20 seconds). After that, dry the silicon wafer.

[0160] <LPD - N measurement>

[0161] The number of LPD-N particles present on the surface of a cleaned silicon wafer was determined using a wafer inspection device manufactured by KLA-Tencor, trade name "Surfscan SP5", in Oblique mode of the same device, and the determination was made according to the following criteria.

[0162] ◎: The number of LPD-Ns is less than 100.

[0163] 〇: The number of LPD-Ns is more than 100 but less than 500.

[0164] ×: The number of LPD-Ns exceeds 500.

[0165] Mark ◎ and 〇 as qualified, and × as unqualified. Record the results in the corresponding column of Table 1.

[0166] [Table 1]

[0167]

[0168] As shown in Table 1, in Examples 1-4, which used abrasive compositions containing abrasive particles, an alkaline compound, a random copolymer containing VA and VP units, and a nonionic surfactant with a Mw of less than 3000 and a nonionic surfactant content of more than 0.00035% and less than 0.005%, the water repellency distance was less than 20 mm, the number of LPD-Ns was less than 500, and the wettability was excellent with fewer defects. On the other hand, in Comparative Example 1, which used HEC as the water-soluble polymer, the wettability and defects were worse than in the Examples. Furthermore, in Comparative Example 2, where the nonionic surfactant content was less than 0.00035%, although the water repellency distance was small, the number of LPD-Ns exceeded 500, making it impossible to achieve both good wettability and reduced defects. In Comparative Example 3, where the nonionic surfactant content was more than 0.005%, both wettability and defects were unacceptable. Furthermore, in Comparative Example 4, which used a nonionic surfactant with a molecular weight of 3000, although the water repellency distance was small, the number of LPD-Ns exceeded 500, making it impossible to simultaneously achieve wettability and defect reduction. Moreover, in Comparative Example 5, which used an anionic surfactant instead of a nonionic surfactant, sufficient wettability could not be obtained.

[0169] Specific examples of the present invention have been described in detail above; however, these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes technologies modified or altered from the specific examples described above.

Claims

1. A polishing composition for polishing surfaces formed of silicon material. The grinding composition comprises: abrasive grains, an alkaline compound, a random copolymer comprising vinyl alcohol units and N-vinylpyrrolidone units, and a nonionic surfactant. The molecular weight of the nonionic surfactant is less than 3000. The content α [weight%] of the nonionic surfactant is in the range of 0.00035 < α < 0.00500.

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

3. The grinding composition according to claim 1 or 2, wherein it comprises silica particles as the abrasive grains.

4. A concentrate of the grinding composition according to claim 1 or 2.

5. A polishing method comprising polishing a surface formed of silicon material using the polishing composition of claim 1 or 2.

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