Additive for CMP, and CMP composition containing same

Abstract

Provided is an additive for CMP, which contains a polycarboxylic acid-based copolymer that contains, as constituent monomers, 5-95 mol% of (a) a compound represented by formula (1): R1O(AO)nR2 (wherein R1 represents a hydrocarbon group having 1-18 carbon atoms; R2 represents an unsaturated hydrocarbon group having 2-5 carbon atoms; AO represents one or more types of oxyalkylene groups each having 2-4 carbon atoms; and n represents the average number of moles of oxyalkylene groups added and is a numerical value of 1-100), 0-95 mol% of (b) a maleic acid-based compound, and 0-60 mol% of (c) a compound copolymerizable with the compound (a) and the compound (b) (wherein the total amount of the compound (b) and the compound (c) is 5-95 mol%) and that has a weight average molecular weight of 14,000 or less. As a result, it becomes possible to provide a technique that can prevent the aggregation of abrasive grains and can improve a polishing speed without using grains of a surface-modified metal oxide or the like as the abrasive grains.

Description

CMP polishing additive and CMP polishing composition containing the same

[0001] The present invention relates to a CMP polishing additive and a CMP polishing composition containing the same. In the present invention, "CMP" means chemical mechanical polishing.

[0002] In the development of semiconductor devices, such as semiconductor integrated circuits, miniaturization and speedup have recently led to demands for higher density and integration through finer wiring and layering. Various techniques, such as CMP, have been used to achieve this. CMP is an essential technique for surface planarization of interlayer insulating films and other processed films, plug formation, and embedded metal wiring formation, and is used to smooth substrates.

[0003] In CMP, alumina-based abrasives, ceria (cerium oxide)-based abrasives, silica-based abrasives, and the like are generally used. If these abrasive grains aggregate to form coarse particles, this can lead to defects on the polished surface. Therefore, dispersants are generally added to prevent the aggregation of abrasive grains and suppress defects on the polished surface.

[0004] On the other hand, in recent years, the abrasive grains themselves have been made finer to further reduce defects on the polished surface. However, this finer grain size may decrease the polishing rate and production efficiency in some cases, even when a dispersant is used.

[0005] Therefore, in order to improve the polishing rate compared to conventional methods, Patent Document 1 proposes a CMP abrasive that contains abrasive grains and a liquid medium, and the abrasive grains include metal oxide particles or metal hydroxide particles that have been surface-modified with an epoxide compound.

[0006] Japanese Patent Application Laid-Open No. 2019-196467

[0007] According to the invention described in Patent Document 1, it is possible to improve the polishing rate, but it is necessary to use particles of metal oxide or the like whose surfaces have been previously modified with an epoxide compound as abrasive grains, and after the abrasive grain surfaces have been modified, it is necessary to wash away any unreacted epoxide compound, and there is room for improvement in that there are many steps involved.

[0008] Therefore, an object of the present invention is to provide a technology that can suppress agglomeration of abrasive grains and improve the polishing rate without using particles of surface-modified metal oxides or the like as abrasive grains.

[0009] The present inventors have conducted extensive research in light of the above-mentioned problems and have found that the above-mentioned problems can be solved by simply adding a specific polycarboxylic acid copolymer to a polishing process using ordinary abrasive grains and a dispersant.

[0010] [1] As a constituent monomer, (a) a compound represented by the following formula (1): R １ O(AO)nR ２ ...(1) (In formula (1), R １ represents a hydrocarbon group having 1 to 18 carbon atoms, and R ２ (a) is an unsaturated hydrocarbon group having 2 to 5 carbon atoms, AO is one or more oxyalkylene groups having 2 to 4 carbon atoms, and n is the average number of moles of oxyalkylene groups added, which is a number from 1 to 100; (b) 5 to 95 mol % of a compound represented by the formula (a), (b) 0 to 95 mol % of a maleic acid compound, and (c) 0 to 60 mol % of a compound copolymerizable with the (a) compound and the (b) compound (provided that the total of the (b) compound and the (c) compound is 5 to 95 mol %), and a polycarboxylic acid copolymer having a weight average molecular weight of 14,000 or less. [2] The CMP polishing composition according to the preceding paragraph [1], which contains the additive for CMP polishing and abrasive grains, wherein the CMP polishing composition contains 0.1 to 10 wt % of abrasive grains, and the CMP polishing composition contains 0.1 to 60 parts by mass of the additive for CMP polishing per 100 parts by mass of the abrasive grains.

[0011] According to the present invention, it is possible to provide a technology that can suppress agglomeration of abrasive grains and improve the polishing rate without using particles of surface-modified metal oxides or the like as abrasive grains.

[0012] In this specification, numerical ranges defined using the symbol "to" are intended to include both the upper and lower limits of the symbol. For example, "2 to 4" means 2 or more and 4 or less. Furthermore, when a concentration or amount is specified, any higher concentration or amount can be associated with any lower concentration or amount. For example, the descriptions "2 to 10% by mass" and "preferably 4 to 8% by mass" also encompass the descriptions "2 to 4% by mass," "2 to 8% by mass," "4 to 10% by mass," and "8 to 10% by mass."

[0013] Hereinafter, an embodiment of the present invention will be described.

[0014] (CMP Polishing Additive) The CMP polishing additive according to an embodiment of the present invention comprises, as constituent monomers, a polycarboxylic acid copolymer (hereinafter simply referred to as a "polycarboxylic acid copolymer") containing, as constituent monomers, 5 to 95 mol% of a compound represented by the following formula (1) (hereinafter sometimes referred to as "(a) compound"), (b) 0 to 95 mol% of a maleic acid compound (hereinafter sometimes referred to as "(b) compound"), and (c) 0 to 60 mol% of a compound copolymerizable with the (a) compound and the (b) compound (hereinafter sometimes referred to as "(c) compound") (provided that the total of the (b) compound and the (c) compound is 5 to 95 mol%). The weight-average molecular weight of the polycarboxylic acid copolymer is 14,000 or less.

[0015] Formula (1): R １ O(AO)nR ２ ...(1) (In formula (1), R １ represents a hydrocarbon group having 1 to 18 carbon atoms, and R ２ represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, AO represents one or more oxyalkylene groups having 2 to 4 carbon atoms, and n represents the average number of moles of oxyalkylene groups added, which is a number from 1 to 100.

[0016] The compound (a) is a compound represented by the formula (1). １ R may be a hydrocarbon group having 1 to 18 carbon atoms. The structure of the hydrocarbon group is not particularly limited, and may be linear, branched, or cyclic. １Examples of R include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a cyclohexyl group, a phenyl group, and a benzyl group. １ As the alkyl group, a hydrocarbon group having 1 to 4 carbon atoms is preferred, and a methyl group, an ethyl group, a propyl group, or a butyl group is more preferred.

[0017] In formula (1), R ２ R may be an unsaturated hydrocarbon group having 2 to 5 carbon atoms. The structure of the unsaturated hydrocarbon group is not particularly limited, and may be linear or branched. ２ Examples of R include a vinyl group, an allyl group, an isopropenyl group, a 1-propenyl group, a methallyl group, and a 3-butenyl group. ２ is preferably an unsaturated hydrocarbon group having 3 to 4 carbon atoms, and is more preferably an allyl group or a methallyl group, since they have suitable polymerizability and are easily copolymerizable with the compound (b).

[0018] In formula (1), AO may be an oxyalkylene group having 2 to 4 carbon atoms. The structure of the oxyalkylene group is not particularly limited, and may be linear or branched. AO may be one type or two or more types. When two or more types of AO are used, the addition form may be random or block. Examples of AO include an oxyethylene group, an oxypropylene group, an oxybutylene group, and an oxytetramethylene group. AO is preferably an oxyethylene group, an oxypropylene group alone, or a combination of an oxyethylene group and an oxypropylene group.

[0019] In formula (1), n ​​represents the average number of moles of oxyalkylene groups added, and may be a number from 1 to 100. n is preferably a number from 10 to 60, and more preferably a number from 10 to 30. If n is less than 1, it tends to be difficult to obtain the effect of improving the polishing rate. On the other hand, if n exceeds 100, the viscosity tends to increase, making it difficult to handle.

[0020] (a) The compound is R １ A polyoxyalkylene compound represented by O(AO)nH is ２ Alternatively, an unsaturated hydrocarbon group represented by R ２ A polyoxyalkylene compound represented by O(AO)nH is １ Alternatively, a hydrocarbon group represented by the following formula may be introduced.

[0021] R １ A polyoxyalkylene compound represented by O(AO)nH is ２ There is no particular limitation on the method for introducing the unsaturated hydrocarbon group represented by the formula (I), and for example, the polyoxyalkylene monoalkyl ether can be obtained by adding an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to the polyoxyalkylene monoalkyl ether and subjecting the resulting mixture to an etherification reaction with a monohalogenated unsaturated hydrocarbon such as allyl chloride, allyl bromide, allyl iodide, methallyl chloride or methallyl bromide.

[0022] Also, R ２ A polyoxyalkylene compound represented by O(AO)nH is １ There is no particular limitation on the method for introducing the hydrocarbon group represented by the formula (I), and for example, the compound can be obtained by adding an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to a polyoxyalkylene monoallyl ether or a polyoxyalkylene monomethallyl ether and subjecting the resulting mixture to an etherification reaction with a monohalogenated hydrocarbon such as methyl chloride, methyl bromide, butyl chloride, or butyl bromide.

[0023] The (a) compound may be used alone or in combination of two or more.

[0024] The (b) compound is a maleic acid-based compound. Examples of maleic acid-based compounds include maleic acid, maleic anhydride, and maleate salts. Examples of maleate salts include alkali metal salts, alkaline earth metal salts, ammonium salts, and organic amine salts. These salts may be mono- or di-substituted. Examples of alkali metal salts include monolithium salt, dilithium salt, monosodium salt, disodium salt, monopotassium salt, and dipotassium salt. Examples of alkaline earth metal salts include calcium salt and magnesium salt. Examples of ammonium salts include ammonium salt and diammonium salt. Examples of organic amine salts include alkylamine salts such as methylamine salt, dimethylamine salt, and ethylamine salt, and alkanolamine salts such as monoethanolamine salt, diethanolamine salt, triethanolamine salt, and methylethanolamine salt. As the (b) compound, maleic acid and maleic anhydride are preferred, with maleic anhydride being particularly preferred.

[0025] The compound (b) may be used alone or in combination of two or more.

[0026] The (c) compound is a compound copolymerizable with the above-mentioned (a) compound and (b) compound. Examples of the (c) compound include compounds having an aromatic ring, such as styrene and phenylmaleimide, and compounds having an ethylenically unsaturated bond, such as vinyl acetate, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, isobutylene, diisobutylene, and vinylcyclohexane. Preferred examples of the (c) compound include compounds having an aromatic ring, such as styrene and phenylmaleimide, and particularly preferred is phenylmaleimide.

[0027] The compound (c) may be used alone or in combination of two or more.

[0028] The content ratio of each of the (a) to (c) compounds that can be included as constituent monomers, i.e., the content ratio of the constituent units derived from each of the (a) to (c) compounds, can be calculated from the blending ratio when the constituent monomers are polymerized and can be adjusted appropriately based on the blending ratio. The content ratio (blending ratio) of each constituent monomer may be (a) compound:(b) compound:(c) compound = 5 to 95 mol %:0 to 95 mol %:0 to 60 mol %, assuming that the total of the (b) compound and the (c) compound is 5 to 95 mol %. Furthermore, the (a) compound is preferably 30 to 70 mol %, and when the (b) compound is included, the ratio is preferably 10 to 50 mol %, and when the (c) compound is included, the ratio is preferably 10 to 40 mol %. When the (a) to (c) compounds are included as constituent monomers, the ratio of the (a) compound:(b) compound:(c) compound = 30 to 70 mol %:10 to 50 mol %:10 to 40 mol % is preferred.

[0029] The synthesis of polycarboxylic acid copolymers can be carried out by known methods such as solution polymerization or bulk polymerization, and is not particularly limited. That is, the polymerization reaction can be carried out in the absence of a solvent or in the presence of a solvent. However, when the polymerization reaction is carried out in the presence of a solvent, solvents that can be used include water; alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; ketones such as acetone and methyl ethyl ketone; cyclic ethers such as tetrahydrofuran and dioxane; aliphatic hydrocarbons such as n-hexane, 2-ethylhexane, and methylcyclohexane; and aromatic hydrocarbons such as toluene and xylene. Of these, water, toluene, and methylcyclohexane are preferred. The amount of solvent used is typically 1 to 70% by mass, preferably 5 to 50% by mass, based on the total mass of the constituent monomers. The solution polymerization can be carried out batchwise or continuously.

[0030] Examples of the polymerization initiator include peroxide initiators such as benzoyl peroxide; azo polymerization initiators such as 2,2'-azobisisobutyronitrile; and persulfate initiators such as ammonium persulfate and sodium persulfate. A chain transfer agent may also be used in combination, if necessary. In this case, the molar ratio (D / C) of the polymerization initiator (C) to the chain transfer agent (D) is usually 0.1≦(D) / (C)≦20, and preferably 0.4≦(D) / (C)≦5.

[0031] The polymerization temperature in the synthesis of the polycarboxylic acid copolymer is usually 50 to 100° C., preferably 60 to 90° C., and the polymerization time is usually 5 to 25 hours, preferably 5 to 10 hours. Note that the polymerization time in the case of stepwise temperature increase is the total time.

[0032] Examples of the azo initiator include 2,2'-azobis-2-methylpropionamidine hydrochloride, 2,2'-azobis-N-(2-hydroxyethyl)-2-methylpropionamidine hydrochloride, 2,2'-azobis-2-methyl-N-phenylpropionamidine hydrochloride, 2,2'-azobis-N-(4-chlorophenyl)-2-methylpropionamidine hydrochloride, 2,2'-azobis-N-(4-hydroxyphenyl)-2-methylpropionamidine hydrochloride, 2,2'-azobis- 2-Methyl-N-phenylmethylpropionamidine hydrochloride, 2,2'-azobis-2-methyl-N-2-propenylpropionamidine hydrochloride, 2,2'-azobis-2-methyl-N-[(1,1-bishydroxymethyl)-2-hydroxyethyl]propionamidine, 2,2'-azobis-2-methyl-N-[(1,1-bishydroxymethyl)ethyl]propionamidine, 2,2'-azobis-2-methyl-N-(2-hydroxyethyl)propionamidine, 2,2'- Azoamidine compounds such as azobis-2-methylpropionamidine dihydrate; 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis-2-(2-imidazolin-2-yl)propane hydrochloride, 2,2'-azobis-2-(5-methyl-2-imidazolin-2-yl)propane hydrochloride, 2,2'-azobis-2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane hydrochloride, 2,2'-azobis-2-(2-imidazoline-2 cyclic azoamidine compounds such as 2,2'-azobis-2-(3,4,5,6-tetrahydropyrimidin-2-yl)propane, 2,2'-azobis-2-(3,4,5,6-tetrahydropyrimidin-2-yl)propane hydrochloride, 2,2'-azobis-2-(5-hydroxy-3,4,5,6-tetrahydropyrimidin-2-yl)propane hydrochloride, and 2,2'-azobis-2-(4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl)propane hydrochloride; aqueous azo initiators such as azonitrile compounds such as 2-carbamoylazoisobutyronitrile;Examples of the oil-based azo initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis-2-methylbutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(dimethylisobutyrate), and 1,1'-azobis(cyclohexane-1-carbonitrile). The amount of the azo initiator used is usually 1 to 10 mol %, preferably 2 to 5 mol %, based on the total number of moles of the constituent monomers.

[0033] Examples of chain transfer agents include mercaptoethanol, mercaptoacetic acid, dodecyl mercaptan, thioglycerol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid, octyl thioglycolate, octyl 3-mercaptopropionate, 2-mercaptoethanesulfonic acid, and 2-benzothiazolethiol. Of these, mercaptoethanol, mercaptoacetic acid, dodecyl mercaptan, and 2-benzothiazolethiol are preferred. The amount of chain transfer agent used is typically 1 to 20 mol%, preferably 2 to 10 mol%, based on the total number of moles of constituent monomers. The chain transfer agents may be used alone or in combination of two or more.

[0034] Polycarboxylic acid copolymers obtained by various methods, such as solution polymerization, can be converted into hydrolysates or salts of the hydrolysates, as needed. For example, when maleic anhydride is used as compound (b), a polycarboxylic acid copolymer hydrolysate can be obtained by ring-opening some or all of the maleic anhydride units after the polymerization reaction through hydrolysis. Furthermore, a salt of the polycarboxylic acid copolymer hydrolysate can be obtained by neutralizing some or all of the maleic acid units of the polycarboxylic acid copolymer hydrolysate with an alkali. Examples of alkalis used for neutralization include hydroxides, carbonates, or bicarbonates of alkali metals such as lithium, sodium, and potassium; hydroxides of alkaline earth metals such as magnesium and calcium; alkylamines such as methylamine, dimethylamine, and ethylamine; alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, and methylethanolamine; and ammonia. These hydrolysates and salts thereof may be used alone or in combination.

[0035] The weight average molecular weight (Mw) of the polycarboxylic acid copolymer may be 14,000 or less, preferably 12,000 or less, more preferably less than 10,000, and particularly preferably 8,000 or less. From the viewpoint of improving the polishing rate, Mw is preferably 3,000 or more. In this specification, the weight average molecular weight refers to the weight average molecular weight calculated as standard polyethylene glycol by gel permeation chromatography (GPC).

[0036] The CMP polishing additive according to the embodiment of the present invention includes the polycarboxylic acid copolymer. That is, the polycarboxylic acid copolymer itself may be used as the CMP polishing additive, or other components may be included in addition to the copolymer. Examples of other components include a solvent and a pH adjuster.

[0037] As the solvent, the polymerization solvent used in synthesizing the polycarboxylic acid copolymer may be used as is, or a desired solvent other than the polymerization solvent may be used after isolating the polycarboxylic acid copolymer after polymerization. As described above, the various solvents that can be used in polymerization can be used, and the type of solvent can be appropriately selected depending on the object to be polished, etc. In the case of CMP, water such as ion-exchanged water is preferred. The content of the solvent is not particularly limited, and can be, for example, 20 to 80 mass % of the total CMP polishing additive.

[0038] (CMP polishing composition) The CMP polishing composition according to an embodiment of the present invention contains the above-mentioned CMP polishing additive. The content of the CMP polishing additive is preferably 0.1 to 60 parts by mass as solid content per 100 parts by mass of abrasive grains. The CMP polishing composition contains abrasive grains and a dispersion medium in addition to the CMP polishing additive, and the CMP polishing composition is generally in the form of a slurry.

[0039] The abrasive grains that can be used can be appropriately selected depending on the object to be polished. For example, in the case of CMP applications, abrasive grains commonly used in CMP can be appropriately selected depending on the object to be polished, such as alumina, ceria (cerium oxide), colloidal silica, manganese oxide, and the like. When polishing inorganic insulating materials such as silicon oxide in semiconductor device manufacturing processes, ceria particles are preferred from the viewpoint of polishing speed. The size of the abrasive grains can be any size commonly used in the technical field, and can be appropriately selected depending on the application, such as an average grain size of 10 to 1,000 nm. The content of the abrasive grains may be 0.1 to 10 mass% of the total CMP polishing composition.

[0040] The dispersing medium that can be used can be selected appropriately depending on the application, etc. For example, aqueous solvents and organic solvents can be used. Examples of aqueous solvents include water such as ion-exchanged water. Examples of organic solvents include aromatic hydrocarbon solvents, aliphatic hydrocarbon solvents, ketone solvents, ester solvents, glycol ether solvents, terpene solvents, and alcohol solvents. For CMP applications, aqueous solvents are preferred, and water is more preferred. The content of the dispersing medium is preferably 400 to 100,000 parts by mass per 100 parts by mass of abrasive grains.

[0041] Usable dispersants can be selected appropriately from common dispersants capable of dispersing abrasive grains in a dispersion medium, depending on the type of abrasive grains and dispersion medium, etc. Examples include anionic dispersants, nonionic dispersants, cationic dispersants, and amphoteric dispersants. Furthermore, the dispersant is preferably water-soluble.

[0042] Specific examples of dispersants include phosphate compounds; hydrogen phosphate compounds; homopolymers of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, etc. (polyacrylic acid, etc.); ammonium salts or amine salts of the above polymers; copolymers of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, etc. with monomers such as alkyl acrylates (methyl acrylate, ethyl acrylate, etc.), hydroxyalkyl acrylates (hydroxyethyl acrylate, etc.), alkyl methacrylates (methyl methacrylate, ethyl methacrylate, etc.), hydroxyalkyl methacrylates (hydroxyethyl methacrylate, etc.), vinyl acetate, vinyl alcohol, etc. (copolymers of acrylic acid and alkyl acrylate, etc.); and ammonium salts or amine salts of the above copolymers.

[0043] The dispersants may be used alone or in combination of two or more.

[0044] The content of the dispersant is preferably 0.1 to 10 parts by mass in terms of solid content per 100 parts by mass of the abrasive grains.

[0045] In addition to the above-described components, the CMP polishing composition according to the embodiment may contain other components, such as a pH adjuster, a surfactant, an antifoaming agent, an oxidizing agent, and a rust inhibitor, as long as the components do not inhibit the functions of the other components.

[0046] The CMP polishing composition according to the embodiment can be prepared by a known method. For example, a method in which abrasive grains, a dispersant, a CMP polishing additive, a dispersion medium, and other components added as needed are added to a container and then dispersed at room temperature can be used. The order in which the components are added is not particularly limited. Dispersing equipment for the dispersion treatment can be any known dispersing machine. Examples include a roll mill, a ball mill, a bead mill, a sand mill, a homogenizer, a disperser, and a planetary mixer. Dispersion treatment can also be performed in an ultrasonic bath.

[0047] The CMP polishing composition according to the embodiment contains the additive for CMP polishing described above, and can suppress the aggregation of abrasive grains, maintain a good dispersion state of abrasive grains, and improve the polishing rate without using particles such as surface-modified metal oxides as abrasive grains. Such an effect of improving the polishing rate and the effect of suppressing the aggregation of abrasive grains can be evaluated by the method described in the Examples section below.

[0048] Next, the embodiment of the present invention will be described in more detail based on examples.

[0049] (Synthesis Example 1) In a 0.3 liter flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube, (a) a compound, monomer 1 (H2C=CHCHO(CH2CH2O) 22 CH3, that is, in the compound represented by formula (1), R １ is a methyl group, R ２166.2 g (0.16 mol) of a compound (a compound in which AO is an allyl group, AO is an oxyethylene group, and n is 22) and 15.7 g (0.16 mol) of maleic anhydride as compound (b) were added. Under a nitrogen gas atmosphere, 4.0 g (0.016 mol) of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] was added as a polymerization initiator, and the reaction was carried out at 70±5°C for 4 hours in the first stage and at 90±5°C for 3 hours in the second stage, yielding a polycarboxylic acid copolymer (random copolymer). The molecular weight of the resulting polycarboxylic acid copolymer was measured by GPC according to the method described below, and the weight average molecular weight was found to be 8,000.

[0050] Synthesis Example 2 A polycarboxylic acid copolymer (random copolymer) was obtained in the same manner as in Synthesis Example 1, except for using the formulation shown in Table 1. The molecular weight of the obtained polycarboxylic acid copolymer was measured by GPC according to the method described below, and the weight average molecular weight was found to be 8,000.

[0051] (Synthesis Example 3) In a 0.3 liter flask equipped with a stirrer, a thermometer, and a nitrogen gas inlet tube, (a) a compound, monomer 2 (H2C=CHCHO(CH2CH2O) 16 -(CH2CH(CH3)O)5C4H9, that is, in the compound represented by formula (1), R １ is a butyl group, R ２ 180.3 g (0.16 mol) of a compound in which n is 21 (wherein AO is an allyl group, AO is an oxyethylene group:oxypropylene group randomly added at a molar ratio of 16:5), and 15.7 g (0.16 mol) of maleic anhydride as compound (b) were added. Under a nitrogen gas atmosphere, 4.0 g (0.016 mol) of 2,2'-azobis[2-(2-imidazolin-2-yl)propane] was added as a polymerization initiator, and the reaction was carried out at 70±5°C for 4 hours in the first stage and at 90±5°C for 3 hours in the second stage, yielding a polycarboxylic acid copolymer (random copolymer). The molecular weight of the resulting polycarboxylic acid copolymer was measured by GPC according to the method described below, and the weight average molecular weight was found to be 8,000.

[0052] Synthesis Example 4 A polycarboxylic acid copolymer (random copolymer) was obtained in the same manner as in Synthesis Example 3, except for using the formulation shown in Table 1. The molecular weight of the obtained polycarboxylic acid copolymer was measured by GPC according to the method described below, and the weight average molecular weight was found to be 8,000.

[0053] (Measurement of Weight-Average Molecular Weight) The weight-average molecular weight of the polycarboxylic acid copolymers obtained in Synthesis Examples 1 to 4 was measured by GPC (gel permeation chromatography). The GPC measurement conditions are as follows: Apparatus: HLC-8320GPC manufactured by Tosoh Corporation Column: Shodex-OHPak SB806M-HQ+SB802-HQ manufactured by Shodex Eluent: 0.05 mol / L NaNO ３ Flow rate: 1.0 mL / min Detector: Differential refractive index (RI) Temperature: 40°C Standard: Polyethylene glycol Sample: 100 μL of an aqueous solution containing 0.1% by mass of the active ingredient was injected

[0054] Table 1 shows the blends of the compounds (a), (b), and (c) used in Synthesis Examples 1 to 4 and the weight average molecular weights of the resulting polycarboxylic acid copolymers.

[0055]

[0056] (Examples 1 to 4, Comparative Example 1) Each component was added to a stirring vessel so as to have the composition shown in Table 2, and stirred for 2 minutes with a planetary mixer to obtain a slurry, which is a CMP polishing composition. In Table 2, ceria is cerium (IV) oxide manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., with an average particle size of about 300 nm, and ammonium polyacrylate is Kaocera 2110 manufactured by Kao Corporation.

[0057] (Evaluation) <Polishing Test> The polishing test was carried out using a precision polishing device (MA-200, manufactured by Musashino Electronics Co., Ltd.) equipped with a sample holder and a polishing plate. First, a polishing substrate (silicon thermal oxide film (silicon oxide film), 4 cm x 4 cm) was fixed to the sample holder, and a polishing pad (CMP cloth, manufactured by Musashino Electronics Co., Ltd.) was fixed to the polishing plate. Then, 200 mL of each of the slurries of Examples 1 to 4 and Comparative Example 1 was filled on the polishing pad. Next, the polishing substrate was pressed against the polishing pad with a processing load of 170 g / cm.２ The polishing plate was then rotated at a rotation speed of 74 rpm for 3 minutes to polish the substrate in the liquid. After polishing, the polished substrate was thoroughly washed with pure water and then dried.

[0058] The polishing rate was determined by measuring the thickness of the silicon oxide film on the polished substrate before and after polishing, and dividing the change in film thickness by the polishing time. An optical interference film thickness measurement device (Lambda Ace VM-8000J, manufactured by Dainippon Screen Mfg. Co., Ltd.) was used to measure the film thickness. The results are shown in Table 2.

[0059] <Particle Size Distribution Measurement> In order to evaluate the dispersion state of abrasive grains that affects surface defects for the slurries of Examples 1 to 4 and Comparative Example 1, particle size distribution was measured using a concentrated particle size analyzer (FPAR-1000, manufactured by Otsuka Electronics Co., Ltd.) to measure the median diameter D50. The results are shown in Table 2. The evaluation criteria were as follows: a D50 of less than 350 nm was considered acceptable (◯), and a D50 of 350 nm or greater was considered unacceptable (×).

[0060]

[0061] As shown in Table 2, by using a CMP polishing additive containing a specific polycarboxylic acid copolymer together with a general dispersant without using surface-modified metal oxide particles as abrasive particles, it is possible to suppress agglomeration of abrasive particles, exhibit a good particle size distribution, and improve the polishing rate of silicon oxide. On the other hand, the slurry of Comparative Example 1 showed a good particle size distribution, but because it did not contain the CMP polishing additive of the present invention, the polishing rate was insufficient.

Claims

1. As a constituent monomer, (a) a monomer represented by the following formula (1): R １ O(AO)nR ２ ...(1) (In formula (1), R １ represents a hydrocarbon group having 1 to 18 carbon atoms; R ２ represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, AO represents one or more oxyalkylene groups having 2 to 4 carbon atoms, and n represents the average number of moles of oxyalkylene groups added, which is a number from 1 to 100; (b) 0 to 95 mol % of a maleic acid compound; and (c) 0 to 60 mol % of a compound copolymerizable with the (a) compound and the (b) compound (with the proviso that the total of the (b) compound and the (c) compound is 5 to 95 mol %), and a polycarboxylic acid copolymer having a weight average molecular weight of 14,000 or less.

2. A CMP polishing composition comprising the CMP polishing additive and abrasive grains according to claim 1, wherein the CMP polishing composition contains 0.1 to 10 wt % abrasive grains, and the CMP polishing additive is contained in an amount of 0.1 to 60 parts by mass per 100 parts by mass of the abrasive grains.

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