Grinding composition

Abstract

To provide a polishing composition by which an edge roll-off amount can be reduced effectively in polishing a silicon wafer.SOLUTION: A polishing composition comprises: abrasive grains; a basic compound; a nitrogen-containing water-soluble polymer; and water. The nitrogen-containing water-soluble polymer has a constituting unit including at least one structure selected from a group consisting of an amide structure, an azole structure, a lactam structure, a morpholine structure and an amidine structure; a proportion of the amide structure to a total mass of the constituting unit is 30 mass% or less. In addition, the nitrogen-containing water-soluble polymer has no N-H bond in its molecule.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polishing composition. This application claims priority to Japanese Patent Application No. 2017-72667, filed on March 31, 2017, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] Silicon wafers used as components of semiconductor products are generally polished to a high-quality mirror finish through a lapping process and a polishing process. The polishing process typically includes a preliminary polishing process and a final polishing process. Patent documents related to polishing compositions include, for example, Patent Documents 1 to 4. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 135949 [Patent Document 2] International Publication No. 2012 / 005289 [Patent Document 3] Japanese Patent Application Publication No. 2016-124943 [Patent Document 4] Japanese Patent Application Publication No. 2014-216464 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have investigated the inclusion of a basic compound in a polishing composition used for polishing silicon wafers and the like in order to improve the polishing rate. However, although the inclusion of a basic compound in the polishing composition can improve the polishing rate, the edge vicinity, i.e., the outer periphery of the silicon wafer, may be over-polished compared to the central portion. As a result, there is a risk of an undesirable reduction in the thickness of the outer periphery after polishing (edge ​​roll-off).

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polishing composition that can effectively reduce the amount of edge roll-off after polishing. [Means for solving the problem]

[0006] According to the present specification, a polishing composition is provided. This polishing composition contains abrasive grains, a basic compound, a nitrogen-containing water-soluble polymer, and water. The nitrogen-containing water-soluble polymer does not have an N-H bond in its molecule. This composition can effectively reduce the amount of edge roll-off after polishing.

[0007] In a preferred embodiment of the polishing composition disclosed herein, the nitrogen-containing, water-soluble polymer has a structural unit A in its main chain. The structural unit A includes at least one structure selected from the group consisting of an amide structure, an azole structure, a lactam structure, a morpholine structure, and an amidine structure. A nitrogen-containing, water-soluble polymer having such a structural unit A in its main chain can effectively contribute to reducing the amount of edge roll-off.

[0008] In a preferred embodiment of the polishing composition disclosed herein, the proportion of amide structures relative to the total mass of the structural unit A is 30 mass% or less. When the proportion of amide structures in the structural unit A is within this range, the above-mentioned edge roll-off reducing effect can be more effectively exhibited.

[0009] In a preferred embodiment of the polishing composition disclosed herein, the nitrogen-containing water-soluble polymer is polyacryloylmorpholine, which can effectively contribute to reducing the amount of edge roll-off.

[0010] In a preferred embodiment of the polishing composition disclosed herein, the nitrogen-containing water-soluble polymer is polyvinylimidazole, which can effectively contribute to reducing the amount of edge roll-off.

[0011] In a preferred embodiment of the polishing composition disclosed herein, the abrasive grains are silica grains. By using silica grains as the abrasive grains, the effect of reducing the edge roll-off amount due to the nitrogen-containing water-soluble polymer is more suitably exhibited.

[0012] The polishing composition disclosed herein can be preferably applied to polishing of silicon, for example, polishing of silicon after lapping. A particularly preferred application is pre-polishing of silicon. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.

[0014] <Nitrogen-containing water-soluble polymer> The polishing composition disclosed herein contains a nitrogen-containing water-soluble polymer that does not have an N-H bond in its molecule. Here, the term "water-soluble polymer" refers to a water-soluble compound having the same (homopolymer) or different (copolymer) repeating units. Typically, the compound has a weight-average molecular weight (Mw) of 5,000 or more. By incorporating a nitrogen-containing water-soluble polymer that does not have an N-H bond in its molecule into a polishing composition, the amount of edge roll-off after polishing can be effectively reduced. The reason for this effect is believed to be, for example, as follows: Since the nitrogen-containing water-soluble polymer does not have an N-H bond in its molecule, which indicates hydrophilicity, it can exhibit high adsorption ability to the object to be polished, which generally exhibits hydrophobicity. Therefore, the nitrogen-containing water-soluble polymer adequately adsorbs to the outer periphery of the object to be polished during polishing, protecting the outer periphery and preventing excessive polishing of the outer periphery. This is believed to contribute to the reduction of the amount of edge roll-off. However, this reason alone should not be interpreted as limiting.

[0015] The nitrogen-containing water-soluble polymer in the technology disclosed herein is not particularly limited as long as it has one or more nitrogen atoms (N) in the molecule and the nitrogen atom does not have an N-H bond. For example, the nitrogen-containing water-soluble polymer may be a polymer having a structural unit A in its main chain that does not have an N-H bond. The structural unit A contains main-chain carbon atoms that constitute the main chain of the nitrogen-containing water-soluble polymer and a nitrogen-containing structure containing a nitrogen atom. The nitrogen-containing water-soluble polymer disclosed herein may contain one type of structural unit A or two or more types of structural unit A. The number of main-chain carbon atoms in the structural unit A is not particularly limited, but is typically 2 to 10, preferably 2 to 8, more preferably 2 to 6, and even more preferably 2 to 4, for example, 2 or 3. The nitrogen-containing water-soluble polymer may also be a compound in which one or more hydrogen atoms bonded to the main-chain carbon atoms are each independently substituted with a substituent other than a hydrogen atom, such as a methyl group, a phenyl group, a benzyl group, a halogen group, a difluoromethyl group, a trifluoromethyl group, or a cyano group. Here, the halogen group is, for example, F, Cl, Br, or the like.

[0016] The nitrogen-containing structure is preferably directly bonded to the carbon atom constituting the main chain. The nitrogen-containing structure is not particularly limited as long as it has one or more nitrogen atoms and the nitrogen atoms do not have an N-H bond. For example, the nitrogen-containing structure may be one or more of an N-H bond-free amide structure, an imide structure, an aziridine structure, an azetidine structure, an azeto structure, an azolidine structure, an azole structure, an azinane structure, a pyridine structure, an azepane structure, an azepine structure, a lactam structure, a morpholine structure, a quinoline structure, an indole structure, and an amidine structure. Among these, a structural unit A having any of an amide structure, an azole structure, a lactam structure, a morpholine structure, and an amidine structure is preferred. Here, the amide structure refers to a structure in which the carbon atom adjacent to the nitrogen atom has a double bond with an oxygen atom, and typically refers to a structure represented by -C(=O)-N-. The azole structure refers to a five-membered heterocyclic ring structure containing one or more nitrogen atoms, and is a concept that includes structures substituted with heteroatoms other than nitrogen atoms. Examples of heteroatoms other than nitrogen atoms include oxygen atoms (O) and sulfur atoms (S). The azole structure may include, for example, a pyrrole structure, an imidazole structure, a pyrazole structure, an isothiazole structure, an isoxazole structure, and a furazan structure. A lactam structure has a -C(=O)-NR structure as part of the heterocycle. a -, and may include an α-lactam structure, a β-lactam structure, a γ-lactam structure, a δ-lactam structure, an ε-caprolactam structure, etc. An amidine structure is a -C(=NR a )-NR b R c By performing polishing using a nitrogen-containing water-soluble polymer having in its main chain a structural unit A containing a nitrogen-containing structure as described above, the amount of edge roll-off on the polished surface can be effectively reduced.

[0017] In a preferred embodiment, the proportion of amide structures (CON: formula weight 42) relative to the total mass of the structural unit A is approximately 50% by mass or less. The proportion of the amide structures is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. When the proportion of amide structures in the structural unit A is within this range, the nitrogen-containing water-soluble polymer can exhibit high adsorption ability to the object to be polished. Therefore, the aforementioned effect of reducing edge roll-off can be more effectively achieved. The lower limit of the proportion of the amide structures is not particularly limited, but can be, for example, 5% by mass or more. From the viewpoint of making the nitrogen-containing water-soluble polymer more soluble in water, the proportion of the amide structures may be, for example, 10% by mass or more, typically 20% by mass or more. The proportion of the amide structures may also be 0% by mass. That is, the structural unit A may be substantially free of amide structures. The technology disclosed herein can be preferably implemented in an embodiment in which the proportion of amide structures in the structural unit A is 0% by mass or more and 40% by mass or less, for example, 0% by mass or more and 35% by mass or less, typically 25% by mass or more and 30% by mass or less.

[0018] The structural unit A is preferably derived from a polymerizable monomer. That is, the nitrogen-containing water-soluble polymer disclosed herein is preferably a polymer obtained by polymerizing or copolymerizing a monomer component containing one or more polymerizable monomers. The polymerizable monomer preferably has a polymerizable group having an ethylenically unsaturated bond. Here, the ethylenically unsaturated bond refers to a carbon-carbon double bond capable of radical polymerization. The hydrogen atom bonded to the carbon atom constituting the ethylenically unsaturated bond may be substituted with a substituent containing the aforementioned nitrogen-containing structure. The polymerizable group having an ethylenically unsaturated bond may be a part of a functional group such as an acryloyl group, and examples thereof include a vinyl group, a vinylidene group, and a vinylene group. The polymerizable monomer is preferably one in which the hydrogen atom bonded to the carbon atom constituting the polymerizable group is substituted with a substituent containing the aforementioned nitrogen-containing structure.

[0019] In the technology disclosed herein, particularly preferred examples of the structural unit A include those derived from a polymerizable monomer a represented by the following general formula (1): The nitrogen-containing water-soluble polymer disclosed herein is preferably a polymer obtained by polymerizing or copolymerizing a monomer component containing the monomer a represented by the following general formula (1):

[0020] General formula (1): CH2=CR 1 X (1) In the above general formula (1), R 1 is a hydrogen atom, a methyl group, a phenyl group, a benzyl group, a chloro group, a difluoromethyl group, a trifluoromethyl group, or a cyano group. Among these, a hydrogen atom, a methyl group, or a phenyl group is preferred. X is a group selected from an amide group, an amidine group, and a heterocyclic group containing a nitrogen atom, and does not have an N-H bond.

[0021] X in the above monomer a is an amide group, i.e., —C(═O)—NR 2 R 3 In the case of R 2 ,R 3may be a group selected from alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, alkoxy groups, alkoxyalkyl groups, alkylol groups, acetyl groups, and aromatic groups, which may have a substituent. The total number of carbon atoms in the alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, alkoxy groups, alkoxyalkyl groups, alkylol groups, and acetyl groups, which may have a substituent, is 1 to 40. The total number is preferably 1 to 24, more preferably 1 to 14, and even more preferably 1 to 10. The total number of carbon atoms in the alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, alkoxy groups, alkoxyalkyl groups, alkylol groups, and acetyl groups, excluding substituents, is 1 to 18. The number of carbon atoms is preferably 1 to 8, more preferably 1 to 4. The alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, alkoxy groups, alkoxyalkyl groups, alkylol groups, and acetyl groups, which may have a substituent, may be linear or cyclic, but is preferably linear. Here, "linear" refers to either linear or branched. The aromatic group is an aryl group which may have a substituent. The total number of carbon atoms in the aromatic group is 6 to 60. The total number is preferably 6 to 36, more preferably 6 to 24, and even more preferably 6 to 12. Substituents which the alkyl group, alkenyl group, alkynyl group, aralkyl group, alkoxy group, alkoxyalkyl group, alkylol group, acetyl group, and aromatic group may have include a hydroxyl group; a halogen atom such as a chlorine atom; and a cyano group. Substituents which the alkyl group, alkenyl group, alkynyl group, aralkyl group, alkoxy group, alkoxyalkyl group, alkylol group, and acetyl group may have further include the above-mentioned aromatic group. Substituents which the aromatic group may have further include the above-mentioned alkyl group, alkenyl group, alkynyl group, aralkyl group, alkoxy group, alkoxyalkyl group, alkylol group, and acetyl group. In particular, R 2 ,R 3 is preferably an alkyl group having 1 to 18 carbon atoms (preferably 1 to 8, for example 1 to 4, typically 1, 2 or 3). The alkyl group may be linear or branched. 2 ,R 3is also preferably an alkoxy group, an alkoxyalkyl group, an alkylol group, or an acetyl group. The alkoxy group is preferably an alkoxy group having 1 to 8 carbon atoms (e.g., 1 to 6, typically 1 to 4) (e.g., a methoxy group). The alkoxyalkyl group is preferably an alkoxyalkyl group having 1 to 8 carbon atoms (e.g., 1 to 6, typically 1 to 4) (e.g., a methoxymethyl group, an ethoxymethyl group, a propoxymethyl group, a butoxymethyl group). The alkylol group is more preferably an alkylol group having 1 to 8 carbon atoms (e.g., 1 to 6, typically 1, 2, or 3) (e.g., a methylol group, an ethylol group, a propylol group). R 2 ,R 3 may be the same or different. 2 and R 3 R may be bonded to each other to form a cyclic structure. 2 ,R 3 When they are bonded together to form a ring structure, -R 2 R 3 -Ha-(CH2) n In this case, n is preferably an integer of 3 to 10. It is more preferable that n is 4 to 6. The cyclic structure may be a cyclic structure linked via O or S. For example, -R 2 R 3 - is -(CH2) m -O-(CH2) l -or-(CH2) m -S-(CH2) l -, among others -(CH2) m -O-(CH2) l - is preferable. Here, m is an integer of 1 to 5. The above m is preferably 1 to 3, more preferably 2 or 3. 1 is an integer of 1 to 5. The above l is preferably 1 to 3, more preferably 2 or 3. R 2 ,R 3At least one of the hydrogen atoms constituting the group may be substituted with an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkoxy group, an alkoxyalkyl group, an alkylol group, an acetyl group, an aromatic group, or the like, and may also be substituted with a hydroxyl group, a halogen atom, an amino group, a cyano group, or the like.

[0022] X in the above monomer a is an amidine group, i.e., -C(=NR 4 )-NR 5 R 6 In the case of R 4 ,R 5 ,R 6 may be a group selected from alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, alkoxy groups, alkoxyalkyl groups, alkylol groups, and acetyl groups, which may have a substituent. The total number of carbon atoms in the alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, alkoxy groups, alkoxyalkyl groups, alkylol groups, and acetyl groups, which may have a substituent, is 1 to 40, preferably 1 to 24, more preferably 1 to 14, and even more preferably 1 to 10. The total number of carbon atoms in the alkyl groups, alkenyl groups, alkynyl groups, aralkyl groups, alkoxy groups, alkoxyalkyl groups, alkylol groups, and acetyl groups, excluding the substituents, is 1 to 18, preferably 1 to 8, and more preferably 1 to 4. Among these, R 4 ,R 5 ,R 6 is preferably an alkyl group having 1 to 18 carbon atoms, preferably 1 to 8, for example 1 to 4, typically 1, 2 or 3 carbon atoms. The alkyl group may be linear or branched. 4 ,R 5 ,R 6 It is also preferred that R is an alkoxy group, an alkoxyalkyl group, an alkylol group, or an acetyl group. 4 ,R 5 ,R 6 may be the same or different. 5 and R 6 may be bonded to each other to form a cyclic structure.

[0023] When X in the monomer a is a heterocyclic group containing a nitrogen atom, the heterocyclic group containing a nitrogen atom may be an aliphatic heterocyclic group or an aromatic heterocyclic group having no N-H bond. The aliphatic heterocyclic group and the aromatic heterocyclic group may be either a monocyclic group or a fused ring group. The total number of atoms constituting the ring in the aliphatic heterocyclic group and the aromatic heterocyclic group may be 3 to 15, preferably 3 to 12, more preferably 3 to 10, and even more preferably 3 to 6. The aliphatic heterocyclic group and the aromatic heterocyclic group may contain oxygen atoms or sulfur atoms as ring-constituting atoms in addition to carbon atoms and nitrogen atoms. When the heterocyclic group containing a nitrogen atom is an aliphatic heterocyclic group, examples thereof include a piperidinyl group, a piperazinyl group, a piperazyl group, a pyrrolidinyl group, an imidazolidinyl group, a pyrazolidinyl group, a thiazolidinyl group, an isothiazolidinyl group, an oxazolidinyl group, an isoxazolidinyl group, a morpholinyl group, a pyrrolidone group, etc., among which a pyrrolidone group is preferred.When the heterocyclic group containing a nitrogen atom is an aromatic heterocyclic group, examples thereof include a pyridyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a triazinyl group, a pyrrolyl group, an imidazolyl group, a pyrazolyl group, an oxazolyl group, an isoxazolyl group, a thiazolyl group, an isothiazolyl group, a furazanyl group, a triazolyl group, etc., among which an imidazolyl group is preferred.It is preferred that the nitrogen atom constituting the ring of the heterocyclic group is directly bonded to the carbon atom constituting the vinyl group (CH2=C-). At least one of the hydrogen atoms constituting the heterocyclic group may be substituted with an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkoxy group, an alkoxyalkyl group, an alkylol group, an acetyl group, an aromatic group, or the like, and may also be substituted with a hydroxyl group, a halogen atom, an amino group, a cyano group, or the like.

[0024] A preferred example of the monomer a is R 1 is a hydrogen atom or a methyl group, and X is -C(=O)-NR 2 R 3 and R 2 ,R 3are bonded to each other to form a cyclic structure. Specific examples of such monomer a1 include N-acryloylpiperidine, N-acryloylpiperidin-2-one, N-acryloylpiperazine, N-acryloylmorpholine, N-acryloyl-2-methylmorpholine, N-acryloyl-3-morpholinone, N-acryloyl-3,5-morpholinedione, N-acryloylthiomorpholine, N-acryloylpyrrolidine, N-acryloylpyrrolidone, N-acryloylaziridine, N-acryloylazetidine, N-acryloylazetidin-2-one, N-acryloylazepane, N-acryloylazocane, N-acryloylcaprolactam, N- Examples include methacryloylpiperidine, N-methacryloylpiperidin-2-one, N-methacryloylpiperazine, N-methacryloylmorpholine, N-methacryloyl-2-methylmorpholine, N-methacryloyl-3-morpholinone, N-methacryloyl-3,5-morpholinedione, N-methacryloylthiomorpholine, N-methacryloylpyrrolidine, N-methacryloylpyrrolidone, N-methacryloylaziridine, N-methacryloylazetidine, N-methacryloylazetidin-2-one, N-methacryloylazepane, N-methacryloylazocane, and N-methacryloylcaprolactam. Among these, N-acryloylmorpholine is preferred.

[0025] Other examples of the monomer a include R 1 is a hydrogen atom or a methyl group, and X is -C(=O)-NR 2 R 3 and R 2 ,R 3is a group selected from an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkoxy group, an alkoxyalkyl group, an alkylol group, an acetyl group and an aromatic group. Specific examples of such monomer a2 include N,N-dialkylacrylamides such as N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-dipropylacrylamide, N,N-diisopropylacrylamide, N,N-dibutylacrylamide, N,N-diisobutylacrylamide, N,N-di-tert-butylacrylamide, N,N-diheptylacrylamide, N,N-dioctylacrylamide, N,N-di-tert-octylacrylamide, N,N-didodecylacrylamide, and N,N-dioctadecylacrylamide; substituted N,N-dialkylacrylamides such as N,N-bis(2-hydroxyethyl)acrylamide and N,N-bis(2-cyanoethyl)acrylamide; N,N-dialkenylacrylamides such as N,N-diallylacrylamide; N,N-diphenylacrylamide, N,N-dibenzylacrylamide, and the like. aromatic group-containing acrylamides such as benzyl acrylamide; N,N-dialkylol acrylamides such as N,N-dimethylolacrylamide, N,N-diethylolacrylamide, and N,N-dipropylolacrylamide; N-alkoxy-N-alkylacrylamides such as N-methyl-N-methoxyacrylamide, N-methyl-N-ethoxyacrylamide, N-methyl-N-propoxyacrylamide, N-methyl-N-butoxyacrylamide, N-ethyl-N-methoxyacrylamide, N-ethyl-N-ethoxyacrylamide, N-ethyl-N-butoxyacrylamide, N-propyl-N-methoxyacrylamide, N-propyl-N-ethoxyacrylamide, N-butyl-N-methoxyacrylamide, and N-butyl-N-ethoxyacrylamide; N,N-diacetylacrylamide; N,N-diacetoneacrylamide;N,N-dimethylmethacrylamide, N,N-diethylmethacrylamide, N,N-dipropylmethacrylamide, N,N-diisopropylmethacrylamide, N,N-dibutylmethacrylamide, N,N-diisobutylmethacrylamide, N,N-di-tert-butylmethacrylamide, N,N-diheptylmethacrylamide, N,N-dioctylmethacrylamide, N,N-di-tert-octylmethacrylamide, N,N-dide N,N-Dialkyl methacrylamides such as decyl methacrylamide and N,N-dioctadecyl methacrylamide; substituted N,N-dialkyl methacrylamides such as N,N-bis(2-hydroxyethyl) methacrylamide and N,N-bis(2-cyanoethyl) methacrylamide; N-Dialkenyl methacrylamides such as N,N-diallyl methacrylamide; aromatic methacrylamides such as N,N-diphenyl methacrylamide and N,N-dibenzyl methacrylamide. Examples of suitable methacrylamides include aromatic group-containing methacrylamides; N,N-dialkylol methacrylamides such as N,N-dimethylol methacrylamide, N,N-diethylol methacrylamide, and N,N-dipropylrol methacrylamide; N-alkoxy-N-alkyl methacrylamides such as N-methyl-N-methoxy methacrylamide, N-methyl-N-ethoxy methacrylamide, N-methyl-N-propoxy methacrylamide, N-methyl-N-butoxy methacrylamide, N-ethyl-N-methoxy methacrylamide, N-ethyl-N-ethoxy methacrylamide, N-ethyl-N-butoxy methacrylamide, N-propyl-N-methoxy methacrylamide, N-propyl-N-ethoxy methacrylamide, N-butyl-N-methoxy methacrylamide, and N-butyl-N-ethoxy methacrylamide; N,N-diacetyl methacrylamide; and N,N-diacetone methacrylamide. ;

[0026] Other preferred examples of the monomer a include R 1is a hydrogen atom or a methyl group, and X is a heterocyclic group containing a nitrogen atom. Specific examples of such monomer a3 include N-vinyl-2-pyrrolidone, N-vinylpyrazine, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N-vinylpyridazine, N-vinylpyridine, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrrole, N-methylvinylpyrrolidone, N-vinylpiperidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, and N-vinyl-3,5-morpholinedione. Among these, N-vinyl-2-pyrrolidone and N-vinylimidazole are preferred. The above polymerizable monomer a can be used alone or in combination of two or more.

[0027] The molecular weight of the nitrogen-containing water-soluble polymer is not particularly limited. For example, the Mw of the nitrogen-containing water-soluble polymer is typically 1×10 3 From the viewpoint of reducing the amount of roll-off, it is preferable that the 3 or more, more preferably 1×10 4 More preferably, 1.5 × 10 4 The Mw of the nitrogen-containing water-soluble polymer is typically 100×10 4 Below 90 × 10, preferably 4 Less than or equal to 75×10 4 Below 60 × 10, more preferably 4 When the nitrogen-containing water-soluble polymer is a nitrogen-containing water-soluble polymer having the structural unit A derived from the monomer a1 in the main chain, from the viewpoint of reducing the amount of roll-off, the Mw is preferably 5 × 10 or less. 4 More preferably, 10 × 10 4 More preferably, 30 × 10 4 More preferably, 50×10 4 For example, 70×10 4When the nitrogen-containing water-soluble polymer is a nitrogen-containing water-soluble polymer having the structural unit A derived from the monomer a3 in the main chain, from the viewpoint of reducing the amount of roll-off, the Mw is preferably 0.5 × 10 or less. 4 or more, more preferably 1×10 4 More preferably, 1.5 × 10 4 For example, 30×10 4 The Mw of the nitrogen-containing water-soluble polymer can be determined by gel permeation chromatography (GPC).

[0028] The nitrogen-containing, water-soluble polymer disclosed herein is preferably composed essentially of the structural unit A. In other words, the proportion (molar ratio) of the number of moles of the structural unit A to the number of moles of all structural units contained in the molecular structure of the nitrogen-containing, water-soluble polymer is preferably 99 mol % or more. The molar ratio can be, for example, 99.9 mol % or more, typically 99.9 to 100 mol %. Suitable examples of such a polymer include a homopolymer composed of only one type of polymerizable monomer a disclosed herein and a copolymer composed of two or more types of polymerizable monomer a.

[0029] Furthermore, the nitrogen-containing, water-soluble polymer disclosed herein may be a copolymer containing a structural unit (hereinafter also referred to as "structural unit B") derived from one or more of polymerizable monomer a and copolymerizable monomer b, provided that the effects of the invention are not significantly impaired. The structural unit B is defined as being different from the structural unit A. The structural unit B may also be a structural unit that does not contain a nitrogen atom. The proportion (molar ratio) of the structural unit B in the nitrogen-containing, water-soluble polymer may be less than 50 mol%. The molar ratio may be, for example, less than 30 mol%, typically less than 10 mol%.

[0030] The "mol %" mentioned above is a molar ratio calculated by regarding one structural unit derived from one monomer as one molecule. Here, one monomer includes polymerizable monomer a and monomer b. Therefore, the proportions of the structural units A and B mentioned above can correspond to the molar ratios of polymerizable monomer a and monomer b, respectively, in the total monomer components used in the polymerization.

[0031] <Water> The polishing composition disclosed herein typically contains water in addition to the nitrogen-containing water-soluble polymer. Ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. can be preferably used as the water. To minimize the inhibition of the functions of other components contained in the polishing composition, the water used preferably has a total transition metal ion content of, for example, 100 ppb or less. For example, the purity of the water can be increased by removing impurity ions using an ion exchange resin, removing foreign matter using a filter, distillation, or other procedures. The polishing composition disclosed herein may further contain an organic solvent that can be uniformly mixed with water, if necessary. Examples of the organic solvent include lower alcohols and lower ketones. Generally, the solvent contained in the polishing composition preferably comprises 90% by volume or more of water, more preferably 95% by volume or more of water. Typically, the solvent contained in the polishing composition comprises 99 to 100% by volume of water.

[0032] <Abrasive grain> The polishing composition disclosed herein contains abrasive grains in addition to a nitrogen-containing water-soluble polymer and water. In the technology disclosed herein, the material and properties of the abrasive grains are not particularly limited and can be appropriately selected depending on the intended use and manner of use of the polishing composition. Examples of abrasive grains include inorganic particles, organic particles, and organic-inorganic composite particles. Specific examples of inorganic particles include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and red iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles, poly(meth)acrylic acid particles, and polyacrylonitrile particles. Here, (meth)acrylic acid refers collectively to acrylic acid and methacrylic acid. Such abrasive grains can be used alone or in combination of two or more.

[0033] The abrasive grains are preferably inorganic particles, and particularly preferred are particles made of metal or metalloid oxides. Silica grains are a suitable example of abrasive grains that can be used in the technology disclosed herein. For example, when the technology disclosed herein is applied to a polishing composition for polishing silicon wafers, it is particularly preferred to use silica grains as abrasive grains. The reason for this is as follows: When the object to be polished is a silicon wafer, using silica grains composed of the same element as the object to be polished and oxygen atoms as abrasive grains prevents the generation of metal or metalloid residues other than silicon after polishing. This eliminates the risk of contamination of the silicon wafer surface or deterioration of the electrical properties of the silicon wafer due to the diffusion of metals or metalloids other than silicon into the object to be polished. Furthermore, since the hardness of silicon and silica is similar, polishing can be performed without excessive damage to the silicon wafer surface. From this perspective, a preferred form of polishing composition is a polishing composition containing only silica grains as abrasive grains. Specific examples of silica grains include colloidal silica, fumed silica, precipitated silica, etc. From the viewpoint of being less likely to cause scratches on the surface of the object to be polished and realizing a surface with lower haze, preferred silica particles include colloidal silica and fumed silica. Among them, colloidal silica is preferred. For example, colloidal silica can be preferably used as an abrasive grain in a polishing composition used for polishing silicon wafers. Here, polishing refers to at least one of pre-polishing and final polishing, preferably pre-polishing.

[0034] In the technology disclosed herein, the abrasive grains contained in the polishing composition may be in the form of primary particles, or may be in the form of secondary particles in which a plurality of primary particles are aggregated. Also, abrasive grains in the form of primary particles and abrasive grains in the form of secondary particles may be mixed. In a preferred embodiment, at least a portion of the abrasive grains are contained in the polishing composition in the form of secondary particles.

[0035] Average primary particle diameter of abrasive grains D P1is not particularly limited, but from the viewpoint of polishing speed, etc., it is preferably 5 nm or more, more preferably 10 nm or more, and particularly preferably 20 nm or more. P1 The average primary particle diameter D is preferably 25 nm or more, and more preferably 30 nm or more. P1 Abrasive grains having an average primary particle size of 40 nm or more may be used. From the viewpoint of storage stability, the average primary particle size of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, for example, 100 nm or less. Here, storage stability includes, for example, dispersion stability. In the technology disclosed herein, the average primary particle diameter D P1 For example, D is calculated from the specific surface area (BET value) measured by the BET method. P1 [nm]=6000 / (True density [g / cm 3 ]×BET value [m 2 For example, in the case of silica particles, D P1 The specific surface area can be calculated using the formula: [nm] = 2727 / BET value [nm]. The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300".

[0036] Average secondary particle diameter D of abrasive grains P2 is not particularly limited, but is preferably 15 nm or more, more preferably 30 nm or more, from the viewpoint of polishing speed, etc. From the viewpoint of obtaining a higher polishing effect, the average secondary particle diameter D P2 From the viewpoint of storage stability, the average secondary particle diameter D of the abrasive grains is preferably 50 nm or more. P2 The average secondary particle diameter D of the abrasive grains is suitably 300 nm or less, preferably 260 nm or less, and more preferably 220 nm or less. Here, the storage stability includes, for example, dispersion stability. P2 can be measured by dynamic light scattering using, for example, a model "UPA-UT151" manufactured by Nikkiso Co., Ltd.

[0037] The shape (external shape) of the abrasive grains may be spherical or non-spherical. Specific examples of non-spherical abrasive grains include peanut-shaped (i.e., the shape of a peanut shell), cocoon-shaped, confetti-shaped, and rugby ball-shaped.

[0038] The shape (external shape) of the abrasive grains can be determined, for example, by observation using an electron microscope.

[0039] <Basic compounds> The polishing composition disclosed herein contains a basic compound. Here, the basic compound refers to a compound that has the function of increasing the pH of a polishing composition when added to the composition. The basic compound may be an organic basic compound or an inorganic basic compound. The basic compounds may be used alone or in combination of two or more.

[0040] Examples of the organic basic compound include quaternary ammonium salts such as tetraalkylammonium salts. The anion in the ammonium salts is, for example, OH. - , F - , Cl - , Br - , I - , ClO4 - , BH4 - For example, quaternary ammonium salts such as choline, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide can be preferably used. Among these, tetramethylammonium hydroxide is preferred. Other examples of organic basic compounds include quaternary phosphonium salts such as tetraalkylphosphonium salts. The anion in the phosphonium salts is, for example, OH - , F - , Cl - , Br - , I - , ClO4 - , BH4 -For example, halides and hydroxides of tetramethylphosphonium, tetraethylphosphonium, tetrapropylphosphonium, tetrabutylphosphonium, etc. can be preferably used. Other examples of organic basic compounds include amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine; piperazines such as 1-(2-aminoethyl)piperazine and N-methylpiperazine; azoles such as imidazole and triazole; guanidine; and the like.

[0041] Examples of inorganic basic compounds include ammonia; hydroxides of ammonia, alkali metals, or alkaline earth metals; carbonates of ammonia, alkali metals, or alkaline earth metals; hydrogen carbonates of ammonia, alkali metals, or alkaline earth metals; etc. Specific examples of the hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of the carbonates or hydrogen carbonates include ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate, etc.

[0042] Preferred optional basic compounds include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, and sodium carbonate. Among these, preferred compounds include ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, and potassium carbonate. More preferred compounds include tetramethylammonium hydroxide and potassium carbonate.

[0043] <Other ingredients> The polishing composition disclosed herein may further contain, as necessary, known additives that can be used in polishing compositions, such as a chelating agent, other water-soluble polymers, surfactants, organic acids, organic acid salts, inorganic acids, inorganic acid salts, preservatives, antifungal agents, etc., to the extent that the effects of the present invention are not significantly impaired. Here, the polishing composition is typically a polishing composition used in a polishing step of a silicon wafer.

[0044] The chelating agent forms complex ions with metal impurities that may be contained in the polishing composition and captures them. This serves to suppress contamination of the object to be polished by metal impurities. The chelating agent can be used alone or in combination of two or more. Examples of the chelating agent include aminocarboxylic acid chelating agents, organic phosphonic acid chelating agents, and organic sulfonic acid chelating agents. Examples of the aminocarboxylic acid chelating agent include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid, sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid, and sodium triethylenetetraminehexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, and α-methylphosphonosuccinic acid. Examples of organic sulfonic acid chelating agents include ethylenediaminetetrakismethylenesulfonic acid. Of these, organic phosphonic acid chelating agents or organic sulfonic acid chelating agents are more preferred, and ethylenediaminetetrakis(methylenephosphonic acid) is particularly preferred.

[0045] Examples of other water-soluble polymers include cellulose derivatives, starch derivatives, polymers containing oxyalkylene units, vinyl alcohol polymers, etc. Specific examples include hydroxyethyl cellulose, pullulan, random copolymers or block copolymers of ethylene oxide and propylene oxide, polyvinyl alcohol, polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonate, polyacrylate, polyvinyl acetate, polyethylene glycol, etc. The water-soluble polymers can be used alone or in combination of two or more. The polishing composition disclosed herein may be substantially free of the above-mentioned other water-soluble polymers.

[0046] The polishing composition may contain a surfactant as an optional component. The surfactant can contribute to improving the dispersion stability of the polishing slurry or its concentrate. Anionic or nonionic surfactants are preferably used as the surfactant. Nonionic surfactants are more preferred from the viewpoints of low foaming and ease of pH adjustment. Examples of nonionic surfactants include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyalkylene adducts such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, and polyoxyethylene sorbitan fatty acid esters; and copolymers of multiple oxyalkylenes (e.g., diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers). Of these, polyoxyethylene alkyl ethers are more preferred. The surfactants may be used alone or in combination of two or more. The Mw of surfactants is typically 1 x 10 4It is less than 1000, and preferably 9500 or less from the viewpoint of the filterability of the polishing composition and the cleanability of the object to be polished. The Mw of the surfactant is typically 200 or more, preferably 250 or more, and more preferably 300 or more (for example, 500 or more). The Mw of the surfactant can be a value calculated from the chemical formula.

[0047] Examples of organic acids include fatty acids such as formic acid, acetic acid, and propionic acid; aromatic carboxylic acids such as benzoic acid and phthalic acid; citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, organic sulfonic acids, and organic phosphonic acids. Examples of organic acid salts include alkali metal salts and ammonium salts of organic acids. Here, alkali metal salts include sodium salts and potassium salts. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of inorganic acid salts include alkali metal salts and ammonium salts of inorganic acids. Here, alkali metal salts include sodium salts and potassium salts. Organic acids and salts thereof, and inorganic acids and salts thereof may be used singly or in combination of two or more. Examples of the antiseptic and antifungal agent include isothiazolinone compounds, paraoxybenzoic acid esters, phenoxyethanol, and the like.

[0048] The polishing composition disclosed herein preferably contains substantially no oxidizing agent. If the polishing composition contains an oxidizing agent, when the composition is applied to an object to be polished, the surface of the object to be polished is oxidized, forming an oxide film. The object to be polished is, for example, a silicon wafer. This is because this increases the required polishing time. Specific examples of oxidizing agents include hydrogen peroxide (H2O2), sodium persulfate, ammonium persulfate, and sodium dichloroisocyanurate. Note that "substantially free of oxidizing agent" in a polishing composition means that an oxidizing agent is not intentionally added, at least. Therefore, a polishing composition that inevitably contains a trace amount of oxidizing agent due to raw materials, manufacturing method, etc., can be included in the concept of a polishing composition that is substantially free of oxidizing agent. Here, "trace amount" refers to, for example, the molar concentration of the oxidizing agent in the polishing composition being 0.0005 mol / L or less, preferably 0.0001 mol / L or less, more preferably 0.00001 mol / L or less, and particularly preferably 0.000001 mol / L or less.

[0049] <Preparation of Polishing Composition> The method for producing the polishing composition disclosed herein is not particularly limited. For example, the components contained in the polishing composition may be mixed using a well-known mixing device such as a blade mixer, an ultrasonic disperser, or a homomixer. The manner in which these components are mixed is not particularly limited. For example, all the components may be mixed at once, or may be mixed in an appropriately set order.

[0050] The polishing composition disclosed herein may be a single-component type or a multi-component type, including a two-component type.For example, the polishing composition may be configured so that a liquid A containing some of the components of the polishing composition and a liquid B containing the remaining components are mixed and used to polish an object to be polished.Here, the liquid A may typically be a component other than an aqueous solvent.

[0051] <Polishing liquid> The polishing composition disclosed herein is typically supplied to a polishing object in the form of a polishing liquid containing the polishing composition. The polishing liquid is then used to polish the object. The polishing liquid may be prepared, for example, by diluting any of the polishing compositions disclosed herein. Here, dilution typically refers to dilution with water. Alternatively, the polishing composition may be used as a polishing liquid as is. That is, the concept of a polishing composition in the technology disclosed herein encompasses both a polishing liquid (working slurry) that is supplied to a polishing object and used to polish the object, and a concentrated liquid (stock polishing liquid) that is diluted and used as a polishing liquid. Another example of a polishing liquid containing the polishing composition disclosed herein is a polishing liquid obtained by adjusting the pH of the composition.

[0052] The content of the nitrogen-containing water-soluble polymer in the polishing liquid disclosed herein is not particularly limited, but is typically 0.00001 wt % or more. From the viewpoint of reducing the amount of roll-off, the content is preferably 0.00005 wt % or more, more preferably 0.0001 wt % or more, and even more preferably 0.0003 wt % or more. Furthermore, from the viewpoint of achieving a high level of both polishing rate and edge roll-off reduction, the content of the nitrogen-containing water-soluble polymer is typically 0.01 wt % or less, preferably 0.008 wt % or less, and more preferably 0.005 wt % or less. The content is preferably, for example, 0.003 wt % or less, or 0.002 wt % or less. The technology disclosed herein can be preferably implemented in an embodiment in which the content of the nitrogen-containing water-soluble polymer is 0.0005 wt % or more and 0.001 wt % or less.

[0053] The content of abrasive grains in the polishing liquid disclosed herein is not particularly limited, but is typically 0.01 wt% or more, preferably 0.03 wt% or more, more preferably 0.05 wt% or more, and even more preferably 0.1 wt% or more. By increasing the content of abrasive grains, a higher polishing rate can be achieved. Furthermore, from the viewpoint of the dispersion stability of the polishing composition, the content is usually 10 wt% or less, preferably 5 wt% or less, more preferably 3 wt% or less, and even more preferably 1 wt% or less, for example, 0.8 wt% or less.

[0054] The content of the basic compound in the polishing liquid disclosed herein is usually 0.001 wt % or more. From the viewpoint of reducing the amount of roll-off, the content is preferably 0.005 wt % or more, more preferably 0.01 wt % or more, and even more preferably 0.03 wt % or more. Furthermore, from the viewpoint of achieving a high level of both polishing rate and edge roll-off reduction, the content of the basic compound is usually 1 wt % or less, preferably 0.5 wt % or less, and more preferably 0.3 wt % or less. The content is preferably, for example, 0.2 wt % or less.

[0055] When the polishing liquid disclosed herein contains a chelating agent, the content of the chelating agent in the polishing liquid is typically 0.0001 wt% or more. The content is preferably 0.0005 wt% or more, more preferably 0.001 wt% or more, even more preferably 0.0015 wt% or more, and particularly preferably 0.002 wt% or more. The content of the chelating agent is typically 0.05 wt% or less, preferably 0.01 wt% or less, more preferably 0.008 wt% or less, and even more preferably 0.005 wt% or less.

[0056] The pH of the polishing liquid is preferably 8.0 or higher, for example, 8.5 or higher, more preferably 9.0 or higher, even more preferably 9.5 or higher, and particularly preferably 10.0 or higher, for example, 10.5 or higher. As the pH of the polishing liquid increases, the polishing rate tends to improve. While the upper limit of the pH of the polishing liquid is not particularly limited, it is preferably 12.0 or lower, for example, 11.8 or lower, and more preferably 11.5 or lower. This allows for better polishing of the object to be polished. The above pH is preferably applied to polishing liquids used for polishing silicon wafers.

[0057] <Concentrate> The polishing composition disclosed herein may be in a concentrated form (i.e., in the form of a concentrated polishing liquid) before being supplied to an object to be polished. Such a concentrated polishing composition is advantageous from the viewpoints of convenience and cost reduction during production, distribution, storage, etc. The concentration ratio can be, for example, about 2 to 60 times in terms of volume.

[0058] The polishing composition in the form of such a concentrate can be diluted at a desired time to prepare a polishing liquid, which can then be supplied to the object to be polished. The dilution can typically be carried out by adding the aqueous solvent described above to the concentrate and mixing. When the aqueous solvent is a mixed solvent, the dilution can be carried out by adding only some of the components of the aqueous solvent, or by adding a mixed solvent containing these components in a different amount ratio from the aqueous solvent. As will be described later, in a multi-agent polishing composition, some of the agents can be diluted and then mixed with other agents to prepare a polishing liquid, or multiple agents can be mixed and then the mixture can be diluted to prepare a polishing liquid.

[0059] The content of abrasive grains in the concentrate can be, for example, 50% by weight or less. From the viewpoint of the stability and filterability of the polishing composition, the content is usually preferably 45% by weight or less, more preferably 40% by weight or less. Here, the stability of the polishing composition refers to, for example, the dispersion stability of the abrasive grains. Furthermore, from the viewpoint of convenience and cost reduction during production, distribution, storage, etc., the content of abrasive grains can be, for example, 1.0% by weight or more, preferably 3.0% by weight or more, more preferably 5.0% by weight or more, and even more preferably 7.0% by weight or more.

[0060] The content of the nitrogen-containing water-soluble polymer in the concentrate is not particularly limited, but is usually 0.0003% by weight or more. The content is preferably 0.0015% by weight or more, more preferably 0.003% by weight or more, even more preferably 0.01% by weight or more, and particularly preferably 0.02% by weight or more. The content of the nitrogen-containing water-soluble polymer is usually 0.3% by weight or less, preferably 0.15% by weight or less, more preferably 0.1% by weight or less, and even more preferably 0.05% by weight or less.

[0061] The content of the basic compound in the concentrate is usually 0.03% by weight or more. The content is preferably 0.15% by weight or more, more preferably 0.3% by weight or more, and even more preferably 1% by weight or more. The content of the basic compound is usually 15% by weight or less, preferably 10% by weight or less, and more preferably 6% by weight or less.

[0062] When the concentrate disclosed herein contains a chelating agent, the content of the chelating agent in the polishing liquid is typically 0.003 wt% or more. The content is preferably 0.005 wt% or more, more preferably 0.01 wt% or more, even more preferably 0.03 wt% or more, and particularly preferably 0.05 wt% or more. The content of the chelating agent is typically 1.5 wt% or less, preferably 1 wt% or less, more preferably 0.5 wt% or less, even more preferably 0.3 wt% or less, and particularly preferably 0.1 wt% or less.

[0063] The polishing composition in the form of such a concentrate can be diluted at a desired time to prepare a polishing liquid, which can then be supplied to the object to be polished. The dilution can typically be carried out by adding the aqueous solvent described above to the concentrate and mixing. When the aqueous solvent is a mixed solvent, the dilution can be carried out by adding only some of the components of the aqueous solvent, or by adding a mixed solvent containing these components in a different amount ratio from the aqueous solvent. As will be described later, in a multi-agent polishing composition, some of the agents can be diluted and then mixed with other agents to prepare a polishing liquid, or multiple agents can be mixed and then the mixture can be diluted to prepare a polishing liquid.

[0064] <Application> The polishing composition disclosed herein can be used to polish objects of various materials and shapes. Examples of the material of the object include metals or semimetals, such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, stainless steel, and germanium, as well as alloys thereof; glassy materials, such as quartz glass, aluminosilicate glass, and glassy carbon; ceramic materials, such as alumina, silica, sapphire, silicon nitride, tantalum nitride, and titanium carbide; compound semiconductor substrate materials, such as silicon carbide, gallium nitride, and gallium arsenide; and resin materials, such as polyimide resin. The object may be composed of multiple materials. It is particularly suitable for polishing objects having a silicon surface. The technology disclosed herein is particularly suitable for polishing compositions containing silica particles as abrasives, particularly when the object to be polished is silicon. Typically, the polishing composition contains only silica particles as abrasives. The shape of the object to be polished is not particularly limited. The polishing composition disclosed herein can be preferably applied to polishing an object to be polished having a flat surface, such as a plate or polyhedron, or the edge of the object to be polished. For example, it can be preferably applied to polishing a wafer edge.

[0065] <Polishing method> The polishing composition disclosed herein can be preferably used as a polishing composition for polishing silicon. For example, it can be preferably used as a polishing composition for polishing single crystal or polycrystalline silicon wafers. Hereinafter, a preferred embodiment of a method for polishing an object to be polished using the polishing composition disclosed herein will be described. That is, a polishing liquid (slurry) containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include adjusting the concentration of the polishing composition to prepare the polishing liquid. Here, concentration adjustment may be, for example, dilution. Alternatively, the polishing composition may be used as the polishing liquid as it is. In addition, in the case of a multi-agent polishing composition, preparing the polishing liquid may include mixing the agents, diluting one or more agents before the mixing, or diluting the mixture after the mixing.

[0066] Next, the polishing liquid is supplied to the object to be polished, and polished by a conventional method. For example, when performing a primary polishing process on the object to be polished, the object to be polished that has undergone a lapping process is set in a general polishing device. In the primary polishing process, double-sided polishing is typically performed. The polishing liquid is supplied to the surface of the object to be polished (the surface to be polished) through the polishing pad of the polishing device. Typically, while continuously supplying the polishing liquid, the polishing pad is pressed against the surface of the object to be polished, and the two are moved relative to each other (for example, rotated). Thereafter, if necessary, a further secondary polishing process is performed, and finally, final polishing is performed to complete the polishing of the object to be polished. In the secondary polishing process, single-sided polishing is typically performed. The polishing pad used in the polishing process using the polishing composition disclosed herein is not particularly limited. For example, any of nonwoven fabric type, suede type, polyurethane type, abrasive type, and abrasive type may be used.

[0067] According to this specification, a method for manufacturing an abrasive article is provided, which includes a step of polishing an object to be polished using the polishing composition disclosed herein. The method for manufacturing an abrasive article disclosed herein may further include a step of performing final polishing on the object to be polished after the polishing step using the polishing composition. Here, final polishing refers to the last polishing step in the manufacturing process of the object, i.e., a step in which no further polishing is performed after that step. The final polishing step may be performed using the polishing composition disclosed herein, or may be performed using another polishing composition. In a preferred embodiment, the polishing process using the polishing composition is a polishing process upstream of the final polishing. In particular, it can be preferably applied to preliminary polishing after the lapping process. For example, it can be preferably used in a double-side polishing process (typically a first polishing process) after the lapping process, or in the first single-side polishing process (typically a first second polishing process) performed on a substrate after the double-side polishing process. The double-side polishing process and the first single-side polishing process require a higher polishing rate than the final polishing. Therefore, the polishing composition disclosed herein is suitable as a polishing composition used to polish an object to be polished in at least one (preferably both) of the double-side polishing process and the first single-side polishing process.

[0068] The polishing composition may be used in a manner in which it is used once for polishing and then disposed of (so-called "flow-through"), or may be recycled and reused. An example of a method for recycling a polishing composition is a method in which the used polishing composition discharged from a polishing apparatus is collected in a tank and the collected polishing composition is then supplied to the polishing apparatus again. When recycling a polishing composition, the amount of used polishing composition that is treated as waste liquid is reduced compared to when the polishing composition is used in a flow-through manner, thereby reducing the environmental impact. Furthermore, the reduced amount of polishing composition used can reduce costs. When recycling the polishing composition disclosed herein, new components, components that have decreased with use, or components that are desired to be increased may be added to the polishing composition during use at any time.

[0069] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0070] <Preparation of Polishing Composition> Example 1 A polishing composition was prepared by mixing abrasive grains, a nitrogen-containing water-soluble polymer, a basic compound, a chelating agent, and deionized water. Silica particles (average primary particle size 50 nm) were used as abrasive grains. The nitrogen-containing water-soluble polymer was Mw 55 × 10 4 The polishing composition used was polyacryloylmorpholine (hereinafter referred to as "PACMO"). The basic compounds used were tetramethylammonium hydroxide (hereinafter referred to as "TMAH"), imidazole (hereinafter referred to as "imd"), and potassium carbonate (hereinafter referred to as "K2CO3"). The chelating agent used was ethylenediaminetetrakis(methylenephosphonic acid) (hereinafter referred to as "EDTPO"). The polishing composition contained 15% abrasive grains, 0.024% PACMO, 2.1% TMAH, 0.24% imd, 1.4% K2CO3, and 0.08% EDTPO.

[0071] Example 2 Instead of PACMO, Mw1.7×10 4 Polyvinylimidazole (hereinafter referred to as "PVI") of the above formula was used. The content of PVI in the polishing composition was 0.024%. In other respects, the polishing composition of this example was prepared in the same manner as in Example 1.

[0072] Example 3 Instead of PACMO, Mw25×10 4 Polyvinylpyrrolidone (hereinafter referred to as "PVP") of the above formula was used. The content of PVP in the polishing composition was 0.024%. In other respects, the polishing composition of this example was prepared in the same manner as in Example 1.

[0073] (Comparative Example 1) Instead of PACMO, Mw6×10 4 Poly-N-isopropylacrylamide (hereinafter referred to as "PNIPAM") of the above formula was used. The content of PNIPAM in the polishing composition was 0.024%. In other respects, the polishing composition of this example was prepared in the same manner as in Example 1.

[0074] (Comparative Example 2) Instead of PACMO, Mw1×10 4 Poly-N-vinylacetamide (hereinafter referred to as "PNVA") of the above formula was used. The content of PNVA in the polishing composition was 0.024%. In other respects, the polishing composition of this example was prepared in the same manner as in Example 1.

[0075] (Comparative Example 3) Instead of PACMO, Mw29×10 4 Polyhydroxyethyl acrylamide (hereinafter referred to as "PHEAA") of the above formula was used. The content of PHEAA in the polishing composition was 0.024%. The polishing composition of this example was prepared in the same manner as in Example 1 except for the above.

[0076] Comparative Example 4 A polishing composition according to this example was prepared in the same manner as in Example 1, except that PACMO was not used.

[0077] For each polishing composition example, the type of nitrogen-containing water-soluble polymer used, the presence or absence of an NH bond, the proportion of amide structures relative to the total mass of structural unit A, and Mw are all shown in Table 1.

[0078] <Evaluation of silicon polishing rate> The polishing composition according to each example was diluted 30 times with water and used as a polishing liquid to carry out a polishing test on a silicon wafer, and the silicon removal rate and edge roll-off amount were evaluated. The test specimen was a 6 cm x 6 cm silicon wafer (conductivity type: P type, crystal orientation: <100> ) was used. This test piece was polished under the following conditions. The polishing rate was calculated according to the following formulas (a) and (b). The results are shown in the corresponding columns in Table 1. (a) Polishing depth [cm] = difference in weight of silicon wafer before and after polishing [g] / density of silicon [g / cm 3 ](=2.33g / cm 3 ) / polished area [cm 2 ](=36cm 2 ) (b) Polishing rate [μm / min] = Polishing removal rate [μm] / Polishing time [min] [Polishing conditions] Polishing device: Engis Japan tabletop polishing machine, model "EJ-380IN" Polishing pad: Nitta Haas, product name "MH S-15A" Polishing pressure: 27kPa Plate rotation speed: 50 rpm Head rotation speed: 40 rpm Polishing allowance: 8 μm Polishing liquid supply rate: 100 mL / min (flowing) Polishing liquid temperature: 25℃

[0079] <Edge roll-off evaluation> The amount of edge roll-off at the outer periphery of the polished silicon wafer was evaluated. The amount of edge roll-off was evaluated by measuring the amount of shape displacement on the silicon wafer surface using a NewView 5032 (Zygo, USA). Specifically, a relatively flat region located 2.0 mm to 4.0 mm from the outer periphery of the silicon wafer toward the center was defined as the reference region, and a straight line (reference line) approximating the amount of shape displacement in this region was drawn using the least squares method. Next, a point on the reference line was defined as the reference point, and the maximum amount of shape displacement of the silicon wafer was measured 2.0 mm from the outer periphery, and this was defined as the roll-off value of the silicon wafer. If the outer periphery of the silicon wafer has a drooping shape, the roll-off value is negative; if it has a raised shape, the roll-off value is positive. The results are shown in the "Roll-off value (nm)" column in Table 1.

[0080] [Table 1]

[0081] As shown in Table 1, the polishing compositions of Examples 1 to 3, which used a nitrogen-containing water-soluble polymer having no N-H bond, suppressed sagging of the silicon wafer edge and were superior in the effect of reducing the amount of edge roll-off compared to Comparative Examples 1 to 4. From these results, it was confirmed that the amount of edge roll-off can be reduced by using the nitrogen-containing water-soluble polymer having no N-H bond.

[0082] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

Claims

1. A polishing composition used for pre-polishing a single crystal silicon wafer having a surface made of silicon, comprising: The polishing material contains abrasive grains, a basic compound, a nitrogen-containing water-soluble polymer, and water, The nitrogen-containing water-soluble polymer does not have an N—H bond in the molecule, The nitrogen-containing water-soluble polymer has a structural unit A in its main chain, the structural unit A includes at least one structure selected from the group consisting of an amide structure, an azole structure, a lactam structure, a morpholine structure, and an amidine structure; the proportion of amide structures relative to the total mass of the structural unit A is 30 mass% or less, the nitrogen-containing water-soluble polymer is polyacryloylmorpholine, The weight average molecular weight of the nitrogen-containing water-soluble polymer is 30×10 4 or more and 75×10 4 or less, the content of the nitrogen-containing water-soluble polymer in the polishing composition is 0.00005% by weight or more and 0.008% by weight or less; The polishing composition includes at least one basic compound selected from the group consisting of ammonia, potassium hydroxide, sodium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, and sodium carbonate.

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

3. 3. The polishing composition according to claim 1, further comprising a chelating agent, the content of the chelating agent being 0.0001% by weight or more and 0.05% by weight or less.

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