Polishing agent, additive liquid for polishing agent, and polishing method

Abstract

The present invention provides an abrasive with a high selectivity ratio of silicon oxide film to silicon nitride film and inhibits the agglomeration of abrasive particles that cause grinding damage, an additive liquid for the abrasive, and a grinding method that enables high-speed grinding and inhibits grinding damage. An abrasive comprising abrasive particles, a water-soluble polymer, and water, wherein the water-soluble polymer is a copolymer of monomer (A) and monomer (B) other than monomer (A), wherein monomer (A) is selected from at least one of unsaturated dicarboxylic acids, their derivatives, and salts thereof, and wherein monomer (B) is a monomer containing an ethylene double bond and not containing an acidic group, and wherein the acid value of the water-soluble polymer is 200 to 450 mgKOH / g.

Description

Abrasives, abrasive additives and grinding methods This invention relates to an abrasive, an additive for the abrasive, and a grinding method. In recent years, with the increasing integration and functionality of semiconductor integrated circuits, the development of microfabrication technologies to miniaturize and increase the density of semiconductor devices has been promoted. Previously, in the manufacturing of semiconductor integrated circuit devices (hereinafter also referred to as semiconductor devices), chemical mechanical polishing (CMP) was used to planarize interlayer insulating films or embedded wiring to prevent problems such as surface roughness (steps) exceeding the depth of focus of lithography and thus failing to obtain sufficient resolution in the process of manufacturing semiconductor integrated circuit devices (hereinafter also referred to as semiconductor devices). As the requirements for high precision or miniaturization of devices become more stringent, high planarization based on CMP is becoming increasingly important. Furthermore, in recent years, in order to further miniaturize semiconductor devices, a shallow trench isolation method (hereinafter referred to as STI) using narrower device separation trenches has been introduced in the manufacturing of semiconductor devices. STI is a method of forming electrically insulating device regions by forming trenches on a silicon substrate and embedding insulating films within the trenches. An example of STI will be described with reference to Figures 1A and 1B. In the example of Figures 1A and 1B, firstly, as shown in Figure 1A, after the device region of the silicon substrate 1 is masked with a silicon nitride film 2, a trench 3 is formed on the silicon substrate 1, and an insulating film such as a silicon oxide film 4 is deposited in a manner that fills the trench 3. Subsequently, by means of CMP, the silicon oxide film 4 in the groove 3 which is the concave portion is left behind, and the silicon oxide film 4 on the silicon nitride film 2 which is the convex portion is ground away, thereby obtaining the component separation structure in which the silicon oxide film 4 is embedded in the groove 3 as shown in FIG1B. In CMP within STI, by increasing the selectivity ratio (grinding speed ratio) of the silicon dioxide film to the silicon nitride film, grinding can be stopped at the point where the silicon nitride film is exposed. This grinding method, which uses the silicon nitride film as a barrier film, yields a smoother surface compared to conventional grinding methods. Furthermore, recent CMP technologies have demanded a high selectivity ratio. For example, in Patent Document 1, as a method for suppressing the grinding speed of the aforementioned barrier film, a specific grinding fluid containing a polymer is disclosed, wherein the polymer has a first molecular chain directly bonded by specific functional groups and a second molecular chain branching from the first molecular chain. Furthermore, Patent Document 2 discloses an abrasive for improving the selectivity ratio of silicon dioxide films to silicon nitride films. This abrasive contains a specific water-soluble polymer, cerium oxide particles, and water, and has a pH value of 4 to 9. [Prior Art Documents] [Patent Documents] [Patent Document 1] International Publication No. 2017 / 043139 [Patent Document 2] Japanese Patent Application Publication No. 2019-87660 [The problem the invention aims to solve] The present invention aims to provide an abrasive with a high selectivity ratio of silicon oxide film to silicon nitride film and to suppress abrasive particle aggregation that causes grinding damage, an additive for the abrasive, and a grinding method that enables high-speed grinding and suppresses grinding damage. [Technical Means for Solving the Problem] The abrasive of the present invention comprises abrasive particles, a water-soluble polymer, and water. The water-soluble polymer is a copolymer of monomer (A) and monomer (B) other than monomer (A). The monomer (A) is selected from at least one of unsaturated dicarboxylic acids, their derivatives, and salts thereof. The monomer (B) is a monomer containing an ethylene double bond and without an acidic group. The acid value of the water-soluble polymer is 200-450 mgKOH / g. The abrasive additive of the present invention comprises a water-soluble polymer and water. The water-soluble polymer is a copolymer of monomer (A) and monomer (B) other than monomer (A). The monomer (A) is selected from at least one of unsaturated dicarboxylic acids, their derivatives, and salts thereof. The monomer (B) is a monomer containing an ethylene double bond and without an acidic group. The acid value of the water-soluble polymer is 200-450 mgKOH / g. The polishing method of this invention involves supplying an polishing agent while simultaneously bringing the surface to be polished into contact with a polishing pad, and performing polishing through the relative motion between the two. The polishing agent described above is used as the polishing agent to polish the silicon oxide-containing surface of a semiconductor substrate. [Effects of the Invention] The present invention provides an abrasive with a high selectivity ratio between silicon oxide film and silicon nitride film and inhibits abrasive particle aggregation, an abrasive additive, and a grinding method that enables high-speed grinding and inhibits grinding damage. The embodiments of the present invention will be described below. The present invention is not limited to the following embodiments; other embodiments that conform to the spirit of the present invention may also fall within its scope. For clarity, the following descriptions and drawings are appropriately simplified. Furthermore, for ease of explanation, the scales of the components in the drawings may sometimes differ significantly. Furthermore, in this invention, "surface to be polished" refers to the surface of the object to be polished, such as its surface. In this specification, the surface that appears at an intermediate stage on the semiconductor substrate during the manufacturing process of a semiconductor device is also included in the "surface to be polished." "Silicon oxide" primarily refers to silicon dioxide, but is not limited to this; it may also include silicon oxides other than silicon dioxide. "Selectivity ratio" refers to the polishing speed (R) of the object to be polished (e.g., a silicon oxide film). AThe polishing speed (R) relative to the barrier film B (e.g., silicon nitride film) B The ratio of (R) A / R B In this invention, water solubility means "dissolving 10 mg or more in 100 g of water at 25°C". "(Meth)acrylic acid" is a general term for "methacrylic acid" and "acrylic acid", as are (meth)acrylyl, (meth)acrylate, etc. Furthermore, the "~" indicating a numerical range includes the values ​​before and after it as the lower and upper limits. [Abrasive] The abrasive of the present invention (hereinafter also referred to as the abrasive) is characterized in that it comprises abrasive particles, a water-soluble polymer, and water, wherein the water-soluble polymer is a copolymer of monomer (A) and monomer (B) other than monomer (A), wherein monomer (A) is selected from at least one of unsaturated dicarboxylic acids, their derivatives, and salts thereof, wherein monomer (B) is a monomer containing an ethylene double bond and not containing an acidic group, and wherein the acid value of the water-soluble polymer is 200 to 450 mgKOH / g. When this abrasive is used in CMP applications involving surfaces containing a silicon oxide film (e.g., silicon dioxide film) such as those in STI, it can suppress abrasion damage and achieve a higher abrasion speed relative to the silicon oxide film. On the other hand, it can suppress abrasion of silicon nitride films, resulting in a higher selectivity ratio between silicon oxide and silicon nitride films, thus achieving a higher degree of planarity. The mechanism by which this abrasive achieves these effects is not yet fully understood, but it is speculated that it is due to the adsorption of the specific water-soluble polymer onto both the surface being abraded (especially the silicon nitride surface) and the abrasive particles. The carboxyl groups, derivatives, and salts of the water-soluble polymer (hereinafter sometimes referred to as carboxyl groups, etc.) readily adsorb onto the silicon nitride surface, thereby suppressing abrasion of the silicon nitride surface through the adsorbed water-soluble polymer. In particular, by using a water-soluble polymer with an acid value of 450 mgKOH / g or less, the selectivity ratio between silicon nitride and silicon oxide is increased. On the other hand, the water-soluble polymer adsorbed onto the abrasive particles inhibits the aggregation of these particles, thereby suppressing the generation of coarse particles. In particular, by using water-soluble polymers with an acid value of 200 mgKOH / g or higher, they are easily adsorbed onto the abrasive particles, and the increased solubility of the water-soluble polymers also inhibits the aggregation of the water-soluble polymers themselves. This abrasive contains at least abrasive particles, a water-soluble polymer, and water, and may also contain other components within the scope of achieving the effects of this invention. The components that may be contained in this abrasive are described below. <Abrasive Particles> In this abrasive compound, the abrasive particles can be appropriately selected from those used for CMP. Examples of abrasive particles include, for example, at least one selected from the group consisting of silicon dioxide particles, alumina particles, zirconium oxide particles, cerium compound particles (e.g., cerium oxide particles, cerium hydroxide particles), titanium dioxide particles, germanium oxide particles, and core-shell particles using these as core particles. Examples of silicon dioxide particles include colloidal silicon dioxide and fuming silicon dioxide. Colloidal alumina can also be used as the alumina particles. The aforementioned core-shell particles comprise a core particle (e.g., silicon dioxide particles, aluminum oxide particles, zirconium oxide particles, cerium compound particles, titanium dioxide particles, germanium oxide particles) and a thin film covering the surface of the core particle. Examples of materials for the thin film include at least one oxide selected from silicon dioxide, aluminum oxide, zirconium oxide, cerium oxide, titanium dioxide, germanium oxide, iron oxide, manganese oxide, zinc oxide, yttrium oxide, calcium oxide, magnesium oxide, lanthanum oxide, and strontium oxide. Furthermore, the thin film can also be formed from a plurality of nanoparticles comprising such oxides. The particle size of the aforementioned core particles is preferably 0.01 μm to 0.5 μm, more preferably 0.03 μm to 0.3 μm. The particle size of the aforementioned nanoparticles only needs to be smaller than the particle size of the aforementioned core particles, preferably 1 nm to 100 nm, more preferably 5 nm to 80 nm. As abrasive grains, regarding the superior grinding speed of the insulating film, silicon dioxide particles, aluminum oxide particles, or cerium compound particles are preferred, with cerium compound particles being more preferred. When the surface being ground contains an insulating film (especially a silicon oxide film), cerium oxide particles are even more preferred for achieving a higher grinding speed. In the case of core-shell type particles, the film preferably contains silicon dioxide, aluminum oxide, or a cerium compound, with cerium oxide being more preferred. One type of abrasive grain can be used alone or in combination of two or more types. The content of cerium oxide relative to the total mass of abrasive particles is preferably 70% or more by mass, more preferably 80% or more by mass, further preferably 90% or more by mass, particularly preferably 95% or more by mass, and most preferably 100% by mass. If the content of cerium oxide relative to the total mass of abrasive particles is 70% or more by mass, it is particularly easy to increase the abrasion speed of the insulating film. Cerium oxide particles can be used as appropriate by those known to the public, for example, cerium oxide particles manufactured by the methods described in Japanese Patent Application Publication No. 11-12561, Japanese Patent Application Publication No. 2001-35818, and Japanese Patent Application Publication No. 2010-505735. Specifically, examples include: cerium hydroxide gel prepared by adding alkali to an aqueous solution of cerium(IV) ammonium nitrate, followed by filtration, washing, and calcination to obtain cerium oxide particles; cerium carbonate pulverized and calcined, then pulverized and graded to obtain cerium oxide particles; and cerium(III) salt chemically oxidized in liquid to obtain cerium oxide particles, etc. Cerium oxide particles may also contain impurities other than cerium oxide. The cerium oxide content in one cerium oxide particle is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and most preferably 100% by mass (without impurities). If the cerium oxide content in the cerium oxide particles is 80% by mass or more, it is easier to increase the polishing speed of the insulating film. The average particle size of the abrasive particles is preferably 0.01 μm to 0.5 μm, and more preferably 0.03 μm to 0.3 μm. If the average particle size is less than 0.5 μm, the mechanical force exerted on the surface being abraded is reduced, thus suppressing abrasion damage such as scratches. Furthermore, if the average particle size is 0.01 μm or more, abrasive particle aggregation is suppressed, resulting in excellent storage stability of the abrasive and superior abrasive speed. Furthermore, since the abrasive particles exist in the liquid as aggregated particles (secondary particles) formed by the aggregation of primary particles, the above-mentioned average particle size is the average secondary particle size. The average secondary particle size is measured using a particle size analyzer such as a laser diffraction scattering instrument, which disperses the dispersion in a dispersion medium such as pure water. The content of the aforementioned abrasive particles relative to the total mass of the abrasive is preferably 0.01% to 10.0% by mass, more preferably 0.05% to 2.0% by mass, further preferably 0.1% to 1.5% by mass, and particularly preferably 0.15% to 1.0% by mass. If the content ratio of abrasive particles is above the aforementioned lower limit, an excellent grinding speed for the surface being ground is obtained. On the other hand, if the content ratio of abrasive particles is below the aforementioned upper limit, abrasive particle aggregation can be suppressed, and the increase in viscosity of the abrasive is suppressed, resulting in excellent operability. <Water-soluble polymer> In this abrasive, the water-soluble polymer is a copolymer of monomer (A) and monomer (B). Monomer (A) is selected from at least one of unsaturated dicarboxylic acids, their derivatives, and salts thereof. Monomer (B) is a monomer other than monomer (A), containing ethylene double bonds and lacking acidic groups. The acid value of the water-soluble polymer is 200–450 mgKOH / g. By using the aforementioned specific water-soluble polymer, abrasive damage can be suppressed, and a higher selectivity ratio of silicon oxide film to silicon nitride film can be obtained. The water-soluble polymer comprises at least structural units derived from monomer (A) and structural units derived from monomer (B), and may further comprise other structural units within the scope of achieving the effects of this invention. (Monomer (A)) Monomer (A) comprises one or more selected from unsaturated dicarboxylic acids, derivatives of such unsaturated dicarboxylic acids, salts of such unsaturated dicarboxylic acids, and salts of derivatives of such unsaturated dicarboxylic acids. Monomer (A) facilitates the adsorption of water-soluble polymers onto abrasive particles or silicon nitride surfaces and adjusts the acid value of the water-soluble polymers. The unsaturated dicarboxylic acid in monomer (A) can be any compound having two carboxyl groups and an ethylene double bond in one molecule. The two carboxyl groups can also be an anhydride, such as maleic anhydride. Furthermore, in the intended use of this abrasive, the anhydride in the water-soluble polymer typically undergoes hydrolysis. The unsaturated dicarboxylic acid can have a cyclic structure or be a chain compound without a cyclic structure; in terms of adsorption to the surface being abraded, a chain compound is preferred. Also, the number of ethylene double bonds can be one or more, preferably one to two, and more preferably one. Specific examples of unsaturated dicarboxylic acids include: maleic acid, fumaric acid, icosinic acid, citrate, succinic acid, 2-allylmalonic acid, isopropyl succinic acid, etc. In terms of polymerizability, maleic acid, icosinic acid, or fumaric acid are preferred, and maleic acid is more preferred. Furthermore, unsaturated dicarboxylic acids can be used alone or in combination of two or more. A salt of an unsaturated dicarboxylic acid refers to a compound in which at least one of the two carboxyl groups of the aforementioned unsaturated dicarboxylic acid becomes a salt. Furthermore, salts of unsaturated dicarboxylic acids include not only those formed at the monomeric time point, but also those formed after copolymerization of unsaturated dicarboxylic acids. As a carboxylate (also denoted as COO) - Examples of suitable salts include alkali metal salts and ammonium salts. Specifically, examples include sodium salts, potassium salts, ammonium salts, monoethanol ammonium salts, diethanol ammonium salts, and triethanol ammonium salts. However, considering the potential for metal contamination, ammonium salts are preferred. Derivatives of unsaturated dicarboxylic acids are compounds formed by derivatization of at least one of the two carboxyl groups of the aforementioned unsaturated dicarboxylic acids. Furthermore, derivatives of unsaturated dicarboxylic acids include not only those formed by derivatization at a specific time point of the monomer, but also those formed by derivatization (e.g., esterification) after copolymerization of the unsaturated dicarboxylic acids. Additionally, derivatization can be deactivated after copolymerization; for example, the ester can be hydrolyzed after copolymerization. As a derivatized carboxyl group (also denoted as COR, where R is a substituent), examples include esters (C(=O)OR). 1 , where R 1 (organic group), amide (C(=O)NR) 2 R 3 , where R 2 and R 3 Each can be independently represented by a hydrogen atom or an organic group, etc. As R 1 The organic group in the form of the saturated hydrocarbon group is preferably a saturated hydrocarbon group that can have substituents or oxygen atoms between carbon-carbon bonds. This saturated hydrocarbon group can be straight-chain, branched, or cyclic. Examples of substituents that can be present in the saturated hydrocarbon group include hydroxyl groups and halogen atoms. Furthermore, examples of saturated hydrocarbon groups with oxygen atoms between carbon-carbon bonds include ethylene oxide, propylene oxide, and other epoxides (-(R...)...) 11 O) n H, where R 11 It is an alkyl group having 1 to 6 carbon atoms, where n is an integer greater than or equal to 1, preferably an integer from 1 to 50, etc. R 1 The preferred carbon number is 1 to 50, more preferably 2 to 30, and even more preferably 5 to 20. R 2 and R 3 Each can be independently a hydrogen atom or an organic group. (Regarding R) 2 Or R 3 In the case of an organic group, examples of such organic groups include those related to R. 1 Those that are the same, and those that are in better condition, are also the same. In unsaturated dicarboxylic acid derivatives, the two carboxylic acids can be the same or different derivatives. Alternatively, they can be derived from only one of the two carboxyl groups. Examples of unsaturated dicarboxylic acid derivatives include: unsaturated dicarboxylic acid monoesters, unsaturated dicarboxylic acid diesters, unsaturated dicarboxylic acid monoacrylamines, and unsaturated dicarboxylic acid diacrylamines. Regarding the adsorption properties to the surface being ground, unsaturated dicarboxylic acid derivatives are preferred. The salt of an unsaturated dicarboxylic acid derivative is a compound in which one of the aforementioned unsaturated dicarboxylic acids is a derivative formed by derivatization, and the other undergoes salt formation. Furthermore, the salt of an unsaturated dicarboxylic acid derivative includes not only those that undergo derivatization and / or salt formation at the monomeric point in time, but also those that undergo derivatization and / or salt formation after copolymerization of the unsaturated dicarboxylic acid. Moreover, the carboxylic acid derivative and the salt in the salt of an unsaturated dicarboxylic acid derivative are, as described above, preferably in the same manner. Furthermore, a salt of an unsaturated dicarboxylic acid monoester is preferred. Monomer (A) comprises one or more selected from unsaturated dicarboxylic acids, derivatives of such unsaturated dicarboxylic acids, salts of such unsaturated dicarboxylic acids, and salts of derivatives of such unsaturated dicarboxylic acids. When monomer (A) comprises two or more of these, for example, it may be a combination of two or more unsaturated dicarboxylic acids of different types, or, for example, it may be a combination of one or more unsaturated dicarboxylic acids and one or more derivatives and / or salts of such unsaturated dicarboxylic acids. Regarding monomer (A), in terms of the adsorption of water-soluble polymers onto abrasive particles or silicon nitride surfaces, it is preferred that it contains one or more selected from unsaturated dicarboxylic acids and salts of unsaturated dicarboxylic acids. (Monomer (B)) Monomer (B) is a compound other than monomer (A) that contains vinyl double bonds and does not contain acidic groups. Monomer (B) helps to inhibit the aggregation of abrasive particles, or to suppress the grinding speed of silicon nitride surfaces, and also adjusts the acid value of water-soluble polymers. The number of vinyl double bonds in one molecule of monomer (B) may be one or more, preferably one to two, and more preferably one. Monomer (B) may be selected from monomers without acidic groups and used alone, or selected from two or more monomers. As monomer (B), it can be a monomer with a cyclic structure or a monomer without a cyclic structure. In terms of suppressing abrasive particle aggregation or suppressing the grinding speed of silicon nitride surfaces, it is preferable that monomer (B) includes a monomer with a cyclic structure. Examples of monomers with cyclic structures include: monocyclic cyclic alkenes such as cyclobutene, cyclopentene, cyclohexene, cycloheptene, and cyclooctene, and their derivatives; cyclic conjugated dienes such as cyclopentadiene, cyclohexadiene, cycloheptadiene, and cyclooctadiene, and their derivatives; polycyclic alkenes such as norcamphene, dicyclopentadiene, tricyclodecene, tetracyclododecene, and hexacycloheptadecene, and their derivatives; vinyl alicyclic hydrocarbons such as vinylcyclobutane, vinylcyclobutene, vinylcyclopentane, vinylcyclopentene, vinylcyclohexane, vinylcyclohexene, vinylcycloheptane, vinylcycloheptene, vinylcyclooctane, vinylcyclooctene, N-vinylpyrrolidone, N-vinylcarbazole, and 4-vinylpyridine, and their derivatives; vinyl aromatic monomers such as styrene, methylstyrene, vinyltoluene, p-tert-butylstyrene, chloromethylstyrene, o-(or p-, m-)hydroxystyrene, and o-(or p-, m-)hydroxyphenyl acrylates, and their derivatives; etc. Furthermore, examples of monomers without a cyclic structure include: olefins such as ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, isopropylene, isobutene, isopentene, isohexene, isoheptene, isooctene, isononene, and isodecanene, and their derivatives; aliphatic conjugated dienes such as butadiene, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene, and their derivatives; and (meth)acrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, 2-hydroxyethyl methacrylate, and hydroxypropyl methacrylate, and their derivatives. β-hydroxyethyl acrylate, β-hydroxypropyl acrylate, and β-hydroxyethyl methacrylate, and other vinyl unsaturated carboxylic acid hydroxyalkyl esters and their derivatives; glycidyl acrylate and glycidyl methacrylate, and other unsaturated carboxylic acid glycidyl esters and their derivatives; acrolein and allyl alcohol, and other vinyl compounds and their derivatives; acrylonitrile, methacrylonitrile, and other vinyl unsaturated nitriles and their derivatives; acrylamide, methacrylonitrile, N-hydroxymethylacrylonitrile, and diacetone acrylamide, and other vinyl unsaturated carboxylic acid amides and their derivatives; etc. Regarding monomer (B), in terms of suppressing abrasive particle aggregation or inhibiting the grinding speed of silicon nitride surfaces, it is preferable to include a compound containing a 5-membered or 6-membered ring and an olefin having 3 to 7 carbon atoms, and more preferably to include styrene, N-vinylpyrrolidone, 4-vinylpyridine, or isobutylene, and even more preferably to include styrene or isobutylene. When monomer (B) is in such a case, the hydrophobicity of the following water-soluble polymer becomes suitable, and the selectivity is further improved. (Other Monomers) The water-soluble polymer may also contain other monomers within the scope of the effects of this invention. Examples of other monomers include unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid. The ratio of other monomers relative to the total amount of monomers constituting the water-soluble polymer is preferably 10 mol% or less, more preferably 5 mol% or less, and even more preferably 1 mol% or less. (Other characteristics of water-soluble polymers) When each of the above monomers is a monofunctional monomer with one ethylene double bond, a chain-like water-soluble polymer can be obtained. This water-soluble polymer can be a random copolymer formed by random bonding of monomer (A) and monomer (B), or it can be a block copolymer formed by monomer (A) and monomer (B) each forming one or more blocks. The adsorption capacity of water-soluble polymers for silicon nitride surfaces and abrasive particles can be evaluated according to the following formula (1). X = (COOH and COO in the above water-soluble polymer) - (Quantity of COOH and COO in the above water-soluble polymer) / (Quantity of COOH and COO in the above water-soluble polymer) - (and the quantity of COR) ・・・(1) X represents the percentage of underivatively derivatized carboxyl groups in the water-soluble polymer. Here, compared to carboxylic acid derivatives (COR), carboxyl groups (COOH) and carboxylates (COO) are considered more common. - Through hydrophilic or electrostatic interactions, it tends to exhibit excellent adsorption properties for silicon nitride surfaces and abrasive particles. Therefore, the larger the value of X, the easier it is for the water-soluble polymer to adsorb onto silicon nitride surfaces and abrasive particles. If the water-soluble polymer adsorbs onto the silicon nitride surface, a protective film is formed on the silicon nitride surface, inhibiting the abrasive particles from grinding the silicon nitride surface. Therefore, a higher selectivity ratio can be obtained. If the water-soluble polymer adsorbs onto the abrasive particles, the dispersibility of the abrasive particles is improved mainly due to steric hindrance. Higher dispersibility of the abrasive particles can inhibit agglomeration and the formation of coarse particles, thus reducing the likelihood of abrasive damage. Based on the above points, X is preferably larger. Specifically, X is preferably 0.5 or higher, more preferably 0.55 or higher, further preferably 0.6 or higher, further preferably 0.65 or higher, particularly preferably 0.7 or higher, extremely preferably 0.75 or higher, and most preferably 0.8 or higher. Furthermore, the upper limit of X is 1. The value of X can be calculated, for example, based on the amount of monomer added in the synthesis of the water-soluble polymer. Alternatively, it can also be based on... 13 The value of X is determined by the peak area of ​​the C-NMR measurement results. Furthermore, the value of X can be adjusted by appropriately selecting monomers when copolymerizing the monomers to obtain the water-soluble polymer, or by performing derivatization or derivatization after copolymerization. The molar ratio of monomer (A) constituting the water-soluble polymer relative to the total monomer content is preferably 5 mol% or more, and more preferably 10 mol% or more. If the molar ratio of monomer (A) is 5 mol% or more, the water-soluble polymer has sufficient COOH and COO. - This improves the adsorption capacity of the water-soluble polymer on the silicon nitride surface and abrasive particles. The molar ratio of monomer (A) constituting the water-soluble polymer relative to the total monomer content is preferably 70 mol% or less, more preferably 60 mol% or less, further preferably 50 mol% or less, particularly preferably 40 mol% or less, and extremely preferably 35 mol% or less. If the molar ratio of monomer (A) is 70 mol% or less, the water-soluble polymer has sufficient monomer (B), thereby increasing the hydrophobicity of the water-soluble polymer. Regarding the protective film formed by the water-soluble polymer adsorbed on the silicon nitride surface, since the higher the hydrophobicity of the water-soluble polymer, the more difficult it is for the abrasive particles to approach, the selectivity is further improved. The acid value of the water-soluble polymer tends to depend on the molar ratio of X and monomer (A) mentioned above. That is, the larger X is, and / or the larger the molar ratio of monomer (A), the more likely the acid value will be larger. The acid value of the water-soluble polymer is preferably 200 mgKOH / g or higher, more preferably 230 mgKOH / g or higher, and even more preferably 250 mgKOH / g or higher. If the acid value of the water-soluble polymer is 200 mgKOH / g or higher, then at least one of the molar ratios of X and monomer (A) is sufficiently large, thereby improving the adsorption capacity of the water-soluble polymer for silicon nitride surfaces and abrasive particles. Furthermore, if the acid value of the water-soluble polymer is 200 mgKOH / g or higher, then the solubility of the water-soluble polymer relative to water is improved, and the aggregation of the water-soluble polymer is suppressed. The acid value of the water-soluble polymer is preferably below 450 mgKOH / g, more preferably below 420 mgKOH / g, and even more preferably below 400 mgKOH / g. If the acid value of the water-soluble polymer is below 450 mgKOH / g, the molar ratio of monomer (A) is below a certain value, thus, as mentioned above, the selectivity is further improved. Furthermore, the acid value represents the mass (mg) of potassium hydroxide required to neutralize the acidic components contained in 1 g of the polymer's solids component, and is a value measured by the method described in JIS K 0070:1992. The weight-average molecular weight of the water-soluble polymer can be appropriately adjusted, for example, within the range of 100,000 or less. Preferably, the weight-average molecular weight is 500 or more, more preferably 1,000 or more, and even more preferably 5,000 or more. If the weight-average molecular weight is 500 or more, the adsorption capacity of the aforementioned water-soluble polymer becomes sufficient. Furthermore, the weight-average molecular weight is preferably 50,000 or less, more preferably 40,000 or less, even more preferably 30,000 or less, particularly preferably 20,000 or less, more preferably 15,000 or less, and most preferably 10,000 or less. If the weight-average molecular weight is 50,000 or less, the aggregation of the water-soluble polymers is suppressed. Moreover, the weight-average molecular weight is a value based on polystyrene, determined by gel permeation chromatography (GPC). Regarding the content (concentration) of water-soluble polymer in this abrasive, in order to obtain a higher grinding speed and a higher selectivity relative to the silicon oxide film, it is preferably 0.001 to 10.0% by mass relative to the total mass of the abrasive, more preferably 0.01 to 5.0% by mass, and even more preferably 0.01 to 2.0% by mass. (Manufacturing Method of Water-Soluble Polymers) The manufacturing method of water-soluble polymers can be appropriately selected from known polymerization methods. For example, in the case of random copolymers, monomer (A), monomer (B), and other monomers as needed can be mixed, and then an initiator can be added. Polymerization can be carried out by known polymerization methods such as solution polymerization, bulk polymerization, and various free radical polymerizations. Among these, solution polymerization is preferred in terms of ease of adjusting the weight average molecular weight of the copolymer. <Water> This abrasive contains water as a medium for dispersing the abrasive particles (A) and the metal salt (B). There is no particular limitation on the type of water, but considering the impact on water-soluble polymers, the prevention of impurity contamination, and the impact on pH value, it is preferable to use pure water, ultrapure water, or ion-exchanged water. <Other Ingredients> This abrasive may also contain other ingredients within the scope of achieving the effects of the present invention described above. Examples of other ingredients include: pH adjusters, anti-agglomerating agents, dispersants, lubricants, viscosity enhancers, viscosity modifiers, preservatives, etc. (pH Adjuster) This abrasive may also contain a pH adjuster to bring the pH value to a specified value. The pH adjuster may be appropriately selected from acidic compounds, basic compounds, or amphoteric compounds such as amino acids, and their salts. In this abrasive, it is preferable to contain an acid (acidic compound) as the pH adjuster. Examples of acids include inorganic acids, organic acids, and their salts. Examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, etc., and their ammonium, sodium, and potassium salts may also be used. Examples of organic acids include compounds having carboxyl, sulfonyl, or phosphate groups as acidic groups, and their ammonium, sodium, and potassium salts, etc., wherein organic acids having 1 to 2 carboxyl groups per molecule are preferred. One pH adjuster may be used alone, or in combination of two or more. Examples of organic acids containing a carboxyl group include: alkyl monocarboxylic acids such as formic acid, acetic acid, and propionic acid; heterocyclic carboxylic acids such as 2-pyridinecarboxylic acid, 3-pyridinecarboxylic acid, 4-pyridinecarboxylic acid, 2,3-pyridinedicarboxylic acid, 2,4-pyridinedicarboxylic acid, 2,5-pyridinedicarboxylic acid, 2,6-pyridinedicarboxylic acid, 3,4-pyridinedicarboxylic acid, 3,5-pyridinedicarboxylic acid, pyridinecarboxylic acid, 2,3-pyridinedicarboxylic acid, 2-quinolinecarboxylic acid, pyroglutamic acid, pyridinecarboxylic acid, DL-2-piperidinecarboxylic acid, 2-furancarboxylic acid, 3-furancarboxylic acid, tetrahydrofuran-2-carboxylic acid, and tetrahydrofuran-2,3,4,5-tetracarboxylic acid; and alicyclic carboxylic acids such as cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cycloheptanecarboxylic acid, and cyclohexanecarboxylic acid. Carboxylic acids containing an amino group include: alanine, glycine, glycyl glycine, aminobutyric acid, N-acetylglycine, N,N-di(2-hydroxyethyl)glycine, N-(tert-butoxycarbonyl)glycine, proline, trans-4-hydroxy-L-proline, phenylalanine, sarcosine, hydantoin, creatine, N-[tris(hydroxymethyl)methyl]glycine, glutamic acid, aspartic acid, etc.; lactic acid, malic acid, citric acid, tartaric acid, glycolic acid, gluconic acid, salicylic acid, 2-hydroxyisobutyric acid, glyceric acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, etc.; and pyruvic acid, acetylacetic acid, acetylacetic acid, etc., which contain a ketone group (keto acids). Oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, glutaric acid, adipic acid, phthalic acid; etc. The organic acid used is preferably selected from one or more of acetic acid, gluconic acid, lactic acid, pyridinecarboxylic acid, malic acid, oxalic acid, succinic acid, adipic acid, maleic acid, 2-hydroxyisobutyric acid, 2-bis(hydroxymethyl)propionic acid, and 2-bis(hydroxymethyl)butyric acid. More preferably, it is selected from one or more of pyridinecarboxylic acid, succinic acid, adipic acid, maleic acid, 2-hydroxyisobutyric acid, 2-bis(hydroxymethyl)propionic acid, and 2-bis(hydroxymethyl)butyric acid. Using such organic acids as pH adjusters can achieve a higher grinding speed for silicon oxide films and a higher selectivity ratio between silicon oxide films and silicon nitride films. The mechanism of this effect is not yet fully understood, but it is speculated that when such organic acids are used in conjunction with the water-soluble polymer of the present invention, the interaction between the abrasive particles and the silicon oxide film increases, and the water-soluble polymer is easily adsorbed onto the silicon nitride film, thereby appropriately forming a protective film. Furthermore, as a pH adjuster, it may also contain alkaline compounds. Examples of alkaline compounds include: ammonia, potassium hydroxide; quaternary ammonium hydroxides such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; and organic amines such as monoethanolamine and ethylenediamine. The pH value of this abrasive is preferably 5 to 8. If the pH value is below 8, the abrasion speed of the silicon nitride film is further suppressed, and the selectivity is further improved. Conversely, if the pH value is above 5, the abrasion speed of the silicon oxide film is further improved, and the selectivity is further improved. Regarding the pH value of this abrasive, it is more preferably 5.2 to 7.8. The content ratio of the pH adjuster can be appropriately adjusted to achieve the above-mentioned pH value. As an example, it can be 0.005 to 2.0% by mass relative to the total abrasive, preferably 0.01 to 1.5% by mass, and more preferably 0.01 to 0.3% by mass. Dispersants are used to stably disperse abrasive particles in a dispersion medium; examples include anionic, cationic, nonionic, and amphoteric surfactants. Lubricants are used by users to improve the lubricity of the abrasive and enhance the in-plane uniformity of the grinding speed; examples include water-soluble polymers such as polyethylene glycol and polyglycerol. The preparation method of this abrasive can be appropriately selected from the following methods, which involve uniformly dispersing or dissolving the abrasive particles, water-soluble polymer, and other components used as needed in water as a medium. For example, it is preferable to prepare a dispersion of the abrasive particles and an aqueous solution of the water-soluble polymer (also called a grinding additive) separately, and then prepare the abrasive by mixing them. According to this method, the dispersion and grinding additive exhibit excellent storage stability and ease of transport. This abrasive is preferably prepared immediately before use by performing the above mixing in a grinding apparatus. [Grinding Additive] The grinding additive of the present invention is an additive for preparing a grinding agent by mixing with the dispersion of the above-mentioned grinding particles. It contains a water-soluble polymer and water. The water-soluble polymer is a copolymer of monomer (A) and monomer (B) other than monomer (A). The monomer (A) is selected from at least one of unsaturated dicarboxylic acids, their derivatives, and salts thereof. The monomer (B) is a monomer containing an ethylene double bond and without an acidic group. The acid value of the water-soluble polymer is 200 to 450 mgKOH / g. By adding the above-mentioned grinding additive to the dispersion of abrasive particles, a high grinding speed can be maintained for silicon oxide films while the grinding speed of silicon nitride films can be suppressed to a low level, thereby achieving a high selectivity and flatness of the abrasive. The aforementioned grinding additive contains at least a water-soluble polymer and water, and may further include, as needed, pH adjusters, anti-coagulants, dispersants, lubricants, viscosity enhancers, viscosity modifiers, preservatives, etc. Furthermore, since these components are described above, their descriptions are omitted here. Moreover, when preparing a grinding agent by mixing two liquids—a dispersion of abrasive particles and a grinding additive—the concentration of cerium oxide particles in the dispersion and the concentration of the water-soluble polymer in the grinding additive can be concentrated to 2 to 100 times the concentration required for use, and then diluted to a specified concentration before use. More specifically, for example, when both the concentration of cerium oxide particles in the dispersion and the concentration of the water-soluble polymer in the additive are concentrated to 10 times, the mixture is stirred at a ratio of 10 parts by mass of the dispersion, 10 parts by mass of the grinding additive, and 80 parts by mass of water to prepare the grinding agent. In the above-mentioned grinding additive, the content ratio (concentration) of the water-soluble polymer is preferably 0.001 to 30% by mass of the total additive, more preferably 0.01 to 20% by mass, and even more preferably 0.1 to 10% by mass. Furthermore, in the above-mentioned dispersion of grinding particles, the content ratio of the grinding particles is preferably 0.2 to 40% by mass, more preferably 1 to 20% by mass, and even more preferably 5 to 10% by mass. [Grinding Method] The grinding method of the present invention involves supplying an abrasive while bringing the surface to be ground into contact with a grinding pad, and grinding is performed by the relative motion between the two. The abrasive of the present invention is used as the abrasive to grind the silicon oxide-containing surface of a semiconductor substrate. Here, examples of the surface to be polished include: a semiconductor substrate surface containing a silicon dioxide layer, a patternless wafer with a silicon nitride film and a silicon oxide film deposited on the surface of a semiconductor substrate, and a patterned wafer with these films arranged in a patterned configuration. As a semiconductor substrate, a substrate used by STI is a preferred example. The polishing agent of this invention is also effective for polishing interlayer insulating films between multilayer wirings in the manufacture of semiconductor devices. Examples of silicon oxide films used in STI substrates include PE-TEOS films, which are formed using tetraethoxysilane (TEOS) as a raw material and via plasma CVD. HDP films, formed using high-density plasma CVD, are also examples of silicon oxide films. HARP or FCVD films formed using other CVD methods, and SOD films formed by spin coating, can also be used. Examples of silicon nitride films include those formed using silane or dichlorosilane and ammonia as raw materials via low-pressure CVD, plasma CVD, or ALD. In this polishing method, a known polishing apparatus can be used. Figure 2 is a schematic diagram showing an example of a polishing apparatus. The polishing apparatus 20 shown in Figure 2 includes a polishing head 22 holding a semiconductor substrate 21 such as an STI substrate, a polishing plate 23, an polishing pad 24 attached to the surface of the polishing plate 23, and an polishing agent supply pipe 26 for supplying polishing agent 25 to the polishing pad 24. It is configured such that while polishing agent 25 is supplied from the polishing agent supply pipe 26, the surface of the semiconductor substrate 21 held on the polishing head 22 is brought into contact with the polishing pad 24, and the polishing head 22 and the polishing plate 23 rotate relative to each other to perform polishing. The polishing head 22 can perform both rotary and linear motion. Furthermore, the polishing platen 23 and polishing pad 24 can be the same size as or smaller than the semiconductor substrate 21. In this case, it is preferable to polish the entire surface of the semiconductor substrate 21 by moving the polishing head 22 relative to the polishing platen 23. Alternatively, the polishing platen 23 and polishing pad 24 may not rotate; for example, they can move in one direction in a belt-like manner. The polishing conditions of this polishing apparatus 20 are not particularly limited. The polishing pressure and speed can be further increased by applying a load to the polishing head 22, which presses it against the polishing pad 24. The polishing pressure is preferably around 0.5 to 50 kPa, and from the viewpoint of preventing polishing defects such as uniformity, flatness, and scratches on the polished surface of the semiconductor substrate 21 at the polishing speed, it is more preferably around 3 to 40 kPa. The rotational speed of the polishing pressure plate 23 and the polishing head 22 is preferably around 50 to 500 rpm. Furthermore, the supply amount of polishing flux 25 can be appropriately adjusted according to the composition of the polishing flux or the aforementioned polishing conditions. The abrasive pad 24 can be made of materials such as non-woven fabric, foamed polyurethane, porous resin, or non-porous resin. To facilitate the supply of abrasive 25 to the abrasive pad 24, or to accumulate a certain amount of abrasive 25 on the abrasive pad 24, the surface of the abrasive pad 24 can be grooved in a grid, concentric circle, or spiral pattern. Furthermore, if necessary, the surface of the abrasive pad 24 can be adjusted while the pad adjuster is in contact with the surface of the abrasive pad 24, and abrasion can be performed simultaneously. According to this grinding method, grinding damage can be suppressed, and a higher selectivity ratio of silicon oxide film to silicon nitride film can be obtained, thereby achieving grinding with higher flatness. The present invention will now be described in more detail with reference to embodiments and comparative examples, but the present invention is not limited to these embodiments. Furthermore, Examples 1-4 and Examples 8-12 are embodiments, and Examples 5-7 are comparative examples. [Measurement Method] <pH Value> The pH value was measured using a pH meter HM-30R manufactured by DKK Corporation of East Asia, with the temperature set to 25±5℃. <Average Secondary Particle Size> The average secondary particle size was measured using a laser scattering diffraction particle size distribution measuring device (manufactured by Horiba Corporation, device name: LA-950). <Abrasive Particle Agglomeration Degree> Particles with a diameter of 1 μm or larger were considered coarse particles. Using a particle size distribution measuring device (manufactured by Nihon Entegris GK, device name: AccuSizer780), the temperature was set to 25–30°C, and the number of coarse particles was measured three times. The average value was taken as the coarse particle number. Furthermore, the ratio of the number of coarse particles to the number of coarse particles in the abrasive of Example 1 was taken as the abrasive particle agglomeration degree. <Acid value> was determined by the method described in JIS K0070:1992. <Weight-average molecular weight (Mw)> was determined by gel permeation chromatography (GPC) under the following conditions: • Apparatus: HLC-8320GPC (Tosoh) • Column: TSKgel GMPWXL (Tosoh) • Detector: RI detector (polarity +) • Dissolution solution: 0.2 M NaNO3 3. Aqueous solution • Flow rate 1.0 mL / min • Column temperature 40°C • Calculated using standard PEO / PEG conversion <Selectivity Ratio> Evaluation was conducted using a fully automated CMP system, FREX300X (manufactured by Ebara Corporation). Two-layer polishing pads (Rodel IC-1570) were used, and a diamond pad adjuster (3M A165) was used for pad adjustment. Polishing conditions were set to a polishing pressure of 21 kPa, a polishing disc speed of 100 rpm, and a polishing head speed of 102 rpm. Unless otherwise specified, the flux supply rate was 250 ml / min. The polishing material used for evaluating selectivity was a 12-inch silicon substrate wafer with a silicon dioxide film formed by plasma CVD deposition using tetraethoxysilane or methane as raw materials. Similarly, wafers with a silicon nitride film formed by CVD deposition were also used (hereinafter referred to as "patternless wafers"). Furthermore, when measuring the thickness of silicon dioxide and silicon nitride films deposited on patternless wafers, a SCREEN VM-3210 thickness gauge was used. The polishing speeds of the silicon dioxide and silicon nitride films were calculated by determining the difference between the film thickness before polishing and the film thickness after one minute of polishing. The average polishing speed (nm / min) obtained from the polishing speeds at 49 points in the substrate was used as the polishing speed, and the ratio of the polishing speed of the silicon dioxide film to the polishing speed of the silicon nitride film (polishing speed of silicon dioxide film / polishing speed of silicon nitride film) was calculated as the selection ratio. [Water-soluble polymers] Water-soluble polymer A1: A copolymer comprising ammonium maleate (monomer (A)) and styrene (monomer (B)) in a 1:2 (molar ratio). Mw is 8000, acid value is 350 mgKOH / g, and X is 1. Furthermore, "ammonium maleate" refers to a compound in which at least one of the two carboxyl groups of maleic acid is an ammonium salt (the same applies hereinafter). Water-soluble polymer A2: A copolymer comprising ammonium maleate (monomer (A)) and styrene (monomer (B)) in a 1:3 (molar ratio). Mw is 10000, acid value is 275 mgKOH / g, and X is 1. Water-soluble polymer A3: A copolymer comprising ammonium maleate and an ammonium salt of an ester derivative of maleic acid (monomer (A)) and styrene (monomer (B)) in a 1:2 (molar ratio). Mw is 5000–10000, acid value is 220 mgKOH / g, and X is 0.7. Furthermore, "ester derivatives of maleic acid" refers to compounds formed by esterification of at least one of the two carboxyl groups of maleic acid. Water-soluble polymer B: A copolymer containing ammonium maleate salt (monomer (A)) and styrene (monomer (B)) in a 1:1 (molar ratio). Mw is 8000, acid value is 480 mgKOH / g, and X is 1. Water-soluble polymer C: A copolymer containing monoammonium maleate monoester salt (monomer (A)) and styrene (monomer (B)) in a 1:1 (molar ratio). Monomer (A) contains a small amount of maleate diester. Mw is 7000, acid value is 180 mgKOH / g, and X is 0.4. Water-soluble polymer D: Polyacrylic acid using Mw of 5000 and an acid value of approximately 780 mgKOH / g. X is 1. [Example 1] Cerium oxide particles and ammonium polyacrylate with a molecular weight of 5000, used as a dispersant, were added to deionized water at a mass ratio of 100:0.7. The mixture was stirred and then ultrasonically dispersed and filtered to prepare a cerium oxide particle dispersion with a concentration of 10% by mass of cerium oxide particles and a dispersant concentration of 0.07% by mass. Furthermore, the average secondary particle size of the cerium oxide particles was 0.11 μm. Subsequently, water-soluble polymer A was added to deionized water at a concentration of 0.005% by mass relative to the total amount of the abrasive, and the above-mentioned cerium oxide dispersion was added at a concentration of 0.25% by mass relative to the total amount of the abrasive. Then, 2-hydroxyisobutyric acid was added, and the pH was adjusted to 6.0 to obtain the abrasive (1). Furthermore, the average cerium oxide content of each of the above-mentioned cerium oxide particles was 95% by mass or more. [Examples 2 to 7] In Example 1, the water-soluble polymer, pH adjuster and target pH value were changed as shown in Table 1. Otherwise, the operation was carried out in the same way as in Example 1 to obtain abrasives (2) to (7). The selectivity ratio of abrasives (1) to (7) obtained in Examples 1 to 7 and the abrasive particle aggregation degree in the abrasives were determined by the above method. The results are shown in Table 1. [Table 1] Regarding the abrasives of Examples 5 and 7, which use polymers B or D with higher acid values ​​as water-soluble polymers, although the number of coarse particles was suppressed, the selectivity was as low as 20 or less. On the other hand, regarding the abrasive of Example 6, which uses polymer C with a higher acid value as a water-soluble polymer, the number of coarse particles was more than twice that of Example 1, and abrasive particle aggregation was confirmed. In contrast, regarding the abrasives of Examples 1 to 4, which use water-soluble polymers with an acid value of 200 to 450 mgKOH / g, it was shown that a high selectivity (e.g., 20 or more) and suppression of abrasive particle aggregation (e.g., the number of coarse particles being 2 or less) could be achieved simultaneously. Thus, the abrasive of the present invention, which uses a copolymer of monomer (A) and monomer (B) other than monomer (A) and a water-soluble polymer with an acid value of 200 to 450 mgKOH / g, shows a high selectivity for silicon oxide film and silicon nitride film, and suppresses abrasive particle aggregation that leads to abrasive damage. [Examples 8-12] In Example 1, the type of pH adjuster was changed as shown in Table 2. Otherwise, the operation was performed in the same manner as in Example 1 to obtain abrasives (8) to (12). The abrasive speed (Ox rate) and selectivity of the silicon dioxide films of abrasives (1) and abrasives (8) to (12) obtained in Examples 1, 8, and 12 were measured by the method described above. The results are shown in Table 2. Furthermore, the "Selectivity" in Table 2 records the value of the ratio relative to the selectivity of Example 12. [Table 2] Regarding the abrasives used in Examples 1 and 8-12 as pH adjusters, all exhibited excellent abrasive speed and high selectivity for silicon dioxide films. Among them, the abrasives in Examples 1 and 8-11, where the organic acid was a monocarboxylic acid or dicarboxylic acid, showed an even higher selectivity. [Industrial Applicability] According to the present invention, for example, in a CMP process containing silicon oxide on a polished surface, polishing damage can be suppressed, and a higher selectivity ratio of silicon oxide film to silicon nitride film can be achieved. Therefore, the polishing agent and polishing method of the present invention are suitable for planarization of insulating films for STI in semiconductor device manufacturing. The application claims priority based on Japanese Application Special Purpose 2022-11486 filed on January 28, 2022, the disclosure of which is incorporated herein in its entirety. 1: Silicon substrate 2: Silicon nitride film 3: Trench 4: Silicon oxide film 20: Polishing device 21: Semiconductor substrate 22: Polishing head 23: Polishing plate 24: Polishing pad 25: Polishing compound 26: Polishing compound supply piping Figure 1A is a cross-sectional view showing an example of a previous grinding method, depicting the object to be ground before grinding. Figure 1B is a cross-sectional view showing an example of a previous grinding method, depicting the object to be ground after grinding. Figure 2 is a schematic diagram of an example of a grinding apparatus. 20: Grinding device 21: Semiconductor substrate 22: Grinding head 23: Grinding plate 24: Grinding Pad 25: Abrasive 26: Abrasive supply piping

Claims

1. An abrasive comprising abrasive particles, a water-soluble polymer, and water, wherein the water-soluble polymer is a copolymer of monomer (A) and monomer (B) other than monomer (A), wherein monomer (A) is selected from at least one of unsaturated dicarboxylic acids, their derivatives, and salts thereof, wherein monomer (B) is a monomer containing an ethylene double bond and without an acidic group, and wherein the acid value of the water-soluble polymer is 200-450 mgKOH / g.

2. The abrasive as claimed in claim 1, wherein X, as determined by the following formula (1), is 0.5 or more: X = (the number of COOH and COO- in the above water-soluble polymer) / (the number of COOH, COO- and COR in the above water-soluble polymer) ... (1) Wherein, R is a substituent.

3. The abrasive as claimed in claim 1 or 2, wherein the monomer (A) is selected from at least one of unsaturated dicarboxylic acids and their salts.

4. The abrasive as claimed in claim 1 or 2 further includes a pH adjuster.

5. The abrasive as claimed in claim 4, wherein the pH adjuster contains an acid.

6. The abrasive as claimed in claim 5, wherein the acid comprises an organic acid having 1 to 2 carboxyl groups.

7. The abrasive as claimed in claim 6, wherein the organic acid comprises at least one selected from acetic acid, gluconic acid, lactic acid, pyridinecarboxylic acid, malic acid, oxalic acid, succinic acid, adipic acid, maleic acid, 2-hydroxyisobutyric acid, 2-bis(hydroxymethyl)propionic acid and 2-bis(hydroxymethyl)butyric acid.

8. The abrasive as claimed in claim 1 or 2, wherein the unsaturated dicarboxylic acid comprises at least one selected from maleic acid, icosinic acid and fumaric acid.

9. The abrasive as claimed in claim 1 or 2, wherein the monomer (B) comprises at least one selected from monomers having a cyclic structure and olefins having 3 to 7 carbon atoms.

10. The abrasive as claimed in claim 9, wherein the monomer (B) comprises at least one selected from styrene, N-vinylpyrrolidone, 4-vinylpyridine and isobutylene.

11. The abrasive as claimed in claim 9, wherein the monomer (B) comprises styrene or isobutylene.

12. The abrasive as claimed in claim 1 or 2, wherein the weight average molecular weight of the water-soluble polymer is less than 10,000.

13. The abrasives requested in item 1 or 2 have a pH value of 5 to 8.

14. An abrasive additive comprising a water-soluble polymer and water, wherein the water-soluble polymer is a copolymer of monomer (A) and monomer (B) other than monomer (A), wherein monomer (A) is selected from at least one of unsaturated dicarboxylic acids, their derivatives, and salts thereof, wherein monomer (B) is a monomer containing an ethylene double bond and without an acidic group, and wherein the acid value of the water-soluble polymer is 200 to 450 mg KOH / g.

15. A polishing method comprising supplying an polishing agent while bringing the surface to be polished into contact with a polishing pad, and polishing by means of the relative motion between the two, wherein the polishing agent is any one of claims 1 to 13 as the polishing agent, for polishing the silicon oxide-containing surface of a semiconductor substrate.

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