Polymer, acid detergent, and production method for polymer

Abstract

Provided is a water-soluble polymer that has a low viscosity and can withstand use in strongly acidic or powerfully oxidizing environments such as in hydrogen peroxide.　A polymer according to the present invention includes a structural unit represented by formula (1) and has a viscosity of at least 10 mPa·s in a 10 mass% aqueous solution. (In formula (1), m and n are 0 or 1, m+n=1, and R1–R5 represent a hydrogen atom, a C1–8 alkyl group or hydroxyalkyl group, or a phenyl group.)

Description

Polymer, acid cleaning agent, and method for producing polymer

[0001] This invention relates to a polymer with excellent acid resistance, a method for producing the same, and an acid cleaning agent using the polymer.

[0002] Chemical mechanical polishing (CMP) is performed on the surfaces (processed surfaces) of materials such as semiconductor devices and electronic components, particularly thin substrates (workpieces to be polished) including Si substrates (silicon wafers), hard disk substrates, glass, and LCD (liquid crystal display) substrates, using polishing slurry and polishing pads. In the semiconductor device manufacturing process, processing technologies for increasing density and miniaturization are becoming increasingly important. One such processing technology, CMP (chemical mechanical polishing), is gaining importance in the semiconductor device manufacturing process as a technique for flattening steps (surface irregularities) formed on the substrate.

[0003] In such semiconductor manufacturing processes, as semiconductor devices become smaller and more highly integrated, cleaning is performed to remove metal residues such as abrasive particles and polishing debris remaining on the wafer during wafer planarization in the CMP (chemical mechanical polishing) process. Cleaning compositions used for cleaning include, for example, water-soluble polymers such as specific polycarboxylic acids (Patent Document 1) and ammonium that forms salts with specific water-soluble polymers (Patent Document 2). It has also been proposed to add nitrogen-containing water-soluble polymers to the CMP polishing solution to increase the polishing rate and reduce haze (Patent Document 3). Furthermore, it is known that adding a predetermined nitrogen-containing water-soluble polymer to the polishing solution in a certain proportion increases the smoothness and polishing speed of the object (Patent Document 4).

[0004] Japanese Patent Publication No. 11-181494, Japanese Patent Publication No. 2006-41494, Japanese Patent Publication No. 2015-73055, Japanese Patent Publication No. 2009-1811

[0005] In such polishing solutions and post-polishing cleaning agents, attention is being paid to incorporating water-soluble polymers, such as poly-N-vinylcarboxylic acid amide, which have high adhesion to abrasive particles and high heat resistance themselves.

[0006] Regarding polishing liquids, since they are used to polish polishing materials by combining mechanical polishing with a chemical reaction, the reaction is often controlled and accelerated by the pH of the liquid. Also, regarding cleaning agents, they are used in the cleaning process after the polishing process, and the cleaning agents themselves are made acidic or basic to clean particles, metals, and organic substances. Therefore, the range of pH, oxidizing properties, and reducing properties used is wide. In particular, when using strong acids or hydrogen peroxide with strong oxidizing power, conventional water-soluble polymer materials have a high deterioration rate and cannot withstand repeated use, resulting in the problem that the life cycle of polishing liquids and cleaning liquids must be shortened. The same problem is also observed when using strong bases or bases with high reducing power, and the life cycle of polishing liquids and cleaning liquids is shortened. A water-soluble polymer material that can withstand such an environment has been desired.

[0007] Under such circumstances, the inventors of the present invention have found that a specific polymer has a low viscosity and is a material that can withstand the above environment. By using it in polishing liquids and cleaning agents for semiconductors, the performance imparted by the water-soluble polymer can be maintained even in repeated use under a wide range of pH and redox properties.

[0008] The configuration of the present invention is as follows. [1] A polymer containing a structural unit represented by the following formula (1), wherein the viscosity of a 10% by mass aqueous solution is 10 mPa·s or more.

[0009] (In formula (1), m and n are 0 or 1, and m + n = 1, R ３ ~R ５ represents any one of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a hydroxyalkyl group, and a phenyl group) [2] In the above formula (1), m = 1, R １ ~R ３ is a hydrogen atom, and R ４ ~R ５ is an alkyl group having 1 to 8 carbon atoms or a hydroxyalkyl group, and the polymer of [1]. [3] m = 0, n = 1, and R １ ~R ３ is a hydrogen atom, R ４ ~R ５[1] is a polymer of [1], wherein the polymer is one of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and a phenyl group, and the viscosity of a 10% by mass aqueous solution is 10 mPa·s or more and less than 2000 mPa·s, or the viscosity of a 4% by mass aqueous solution is 500 mPa·s or more and less than 50000 mPa·s. [4] A polymer of [2] having a weight-average molecular weight of 1000 to 6000000. [5] A polymer of [3] having a weight-average molecular weight of 300000 or less. [6] An acid cleaning agent comprising the polymers of [1] to [5]. [7] An acid cleaning agent of [6] further comprising hydrogen peroxide. [8] A monomer represented by the following formula (2) in an aqueous solution using water as a medium.

[0010] A method for producing a polymer by radical polymerization using an azo polymer initiator. (In formula (2), m and n are 0 or 1, and m + n = 1, R １ ~R ５ (wherein represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or a hydroxyalkyl group, and an alkyl group of a phenyl group) [9] In formula (2) above, m = 1 and R １ ~R ３ R is a hydrogen atom, ４ ~R ５ A method for producing the polymer of [8], wherein the alkyl group has 1 to 8 carbon atoms.

[0011] The polymer of the present invention is highly resistant to strong acids or highly oxidizing hydrogen peroxide, and does not degrade easily. Therefore, when used in abrasives and cleaning agents, it can withstand repeated use, extending their lifecycle and leading to cost reductions in semiconductor manufacturing. Furthermore, the polymer of the present invention has a high ability to prevent dishing, which is excessive removal of copper wiring during CMP (Chemical Polishing) caused by acids such as hydrogen peroxide, and can maintain this performance for a long period of time.

[0012] The embodiments of the present invention will be described below, but these embodiments are not limited to the description below.

[0013] (1) Polymer This embodiment is a polymer containing a constituent unit represented by the following formula (1), and the viscosity of a 10% by mass aqueous solution is 10 mPa·s or more.

[0014] (In equation (1), m and n are 0 or 1, and m + n = 1, R １ ~R ５ (wherein represents a hydrogen atom, an alkyl group or hydroxyalkyl group having 1 to 8 carbon atoms, and a phenyl group.) Such polymers are water-soluble polymers and exhibit amphiphilic properties.

[0015] Specifically, when m=1 and n=0, R １ ~R ３ R is a hydrogen atom. ４ ~R ５ This is a polymer such as N,N-dimethylacrylamide (hereinafter collectively referred to as PDMA) which consists of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and a hydroxyalkyl group, and m=0, n=1, R １ ~R ３ R is a hydrogen atom. ４ ~R ５ Examples include polymers such as N-vinylacetamide (hereinafter collectively referred to as PNVA) which are composed of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and a phenyl group, and copolymers thereof, as well as copolymers with other monomers. Other monomers are at least one monomer selected from the group consisting of unsaturated carboxylic acid monomers, salts of unsaturated carboxylic acid monomers, unsaturated carboxylic acid ester monomers, vinyl ester monomers, and unsaturated nitrile monomers. More preferably, these are (meth)acrylic acid and its salts, and even more preferably, sodium acrylate. In this specification, "(meth)acrylic acid" means acrylic acid and methacrylic acid.

[0016] In this embodiment, the polymer is preferably soluble in water if the ratio of the number of moles of constituent units derived from other monomers (hereinafter also referred to as "other constituent units") to the constituent unit represented by formula (1) is set to 1.00 is less than 0.250. It is more preferable that the ratio of the number of moles of other constituent units is 0.150 or less, and even more preferable that it is 0. Therefore, the polymer in this embodiment is preferably a homopolymer composed of the constituent units of formula (1).

[0017] In this embodiment, a homopolymer of PDMA or a homopolymer of PNVA is preferred, and R ４ and R ５ are methyl or ethyl groups, and a homopolymer of PDMA in which both are methyl groups is preferred because it has high resistance to acids, particularly hydrogen peroxide.

[0018] As one aspect, the polymer of this embodiment may have a viscosity of 10 mPa·s or more at 20°C in a 10% by mass aqueous solution. In the case of PDMA, it can be used without particular limitation from low viscosity to high viscosity. Therefore, for PDMA, products with low molecular weight to high molecular weight can be used. Specifically, for PDMA, those having a weight average molecular weight in the range of 1000 to 6000000 are preferred. If it is within this range of weight average molecular weight, it can be used without particular limitation. For PNVA, although it is limited to low molecular weight products with low viscosity, it can be used. It can be used if the polymerization average molecular weight is 300000 or less.

[0019] In the case of PNVA, the viscosity of a 10% by mass aqueous solution is 10 mPa·s or more and less than 2000 mPa·s, or the viscosity of a 4% by mass aqueous solution is 500 mPa·s or more and less than 50000 mPa·s. In the case of PNVA, the viscosity at 20°C in a 10% by mass aqueous solution is 10 mPa·s or more and less than 2*** mPa·s, preferably 10 mPa·s or more and less than 1000 mPa·s, more preferably 15 mPa·s or more and less than 100 mPa·s. Also, the viscosity at 20°C in a 4% by mass aqueous solution is 500 mPa·s or more and less than 5000 mPa·s.

[0020] The viscosity in this specification is measured at 20°C. And high viscosity refers to those having a viscosity of 10000 mPa·s or more in a 10% by mass aqueous solution or a viscosity of 2000 mPa·s or more in a 4% by mass aqueous solution, medium viscosity refers to those having a viscosity of 2000 mPa·s or more and less than 10000 mPa·s in a 10% by mass aqueous solution, and low viscosity refers to those having a viscosity of 10 mPa·s or more and less than 2000 mPa·s in a 10% by mass aqueous solution.

[0021] Such polymers have very high heat resistance and excellent acid resistance in an aqueous solution state. The polymer of the present invention preferably has a low molecular weight generation ratio of 10% or less under any conditions after being immersed in a 1 mol% sodium nitrate aqueous solution and a 0.5 mol% sodium hydroxide aqueous solution at 70°C for 7 days. Further, the polymer of the present invention preferably has a low molecular weight generation ratio of 10% or less after being immersed in a 4 mol% hydrogen peroxide aqueous solution at 23°C for 7 days. Furthermore, the polymer of the present invention preferably has a low molecular weight generation ratio of 40% or less after being immersed in a 1 mol% sodium nitrate aqueous solution and a 0.5 mol% sodium hydroxide aqueous solution at 70°C for 7 days. The low molecular weight generation ratio is evaluated from the change rates of molecular weight and viscosity.

[0022] (2) Method for producing polymer The method for producing the polymer of the present embodiment is to polymerize a monomer represented by the following formula (2) in an aqueous solution using an aqueous medium.

[0023] using an azo-based polymerization initiator by radical polymerization. (In formula (2), m and n are 0 or 1, m + n = 1, and R １ ~R ５ represents any one of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a hydroxyalkyl group, and a phenyl group)

[0024] In formula (2), when m = 1, n = 0, and R １ ~R ３ are hydrogen atoms, N-dialkylacrylamide represented by the following formula (2-1) can be mentioned.

[0025] (In formula (2-1), R ４ ~R ５ represents any one of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and a hydroxyalkyl group)

[0026] As the monomer represented by the general formula (2-1), a monomer in which both R ４ and R ５ are alkyl groups having 1 to 8 carbon atoms (where they may be the same or different), a monomer in which R ４ is a hydrogen atom and R ５ is an alkyl group having 1 to 8 carbon atoms, a monomer in which R ４is a hydrogen atom, R ５ Preferably, R is selected from the group consisting of monomers that are hydroxyalkyl groups having 1 to 2 carbon atoms. ４ is a hydrogen atom, R ５ A monomer in which the group is a methyl group or an ethyl group is preferred, and a monomer in which the group is a methyl group is more preferred.

[0027] Examples of monomers represented by general formula (2-1) include N-methylacrylamide (MAA), N-ethylacrylamide, N-propylacrylamide, N-isopropylacrylamide (NIPAM), N-butylacrylamide, N-isobutylacrylamide, N-tertiarybutylacrylamide, N-heptylacrylamide, N-octylacrylamide, N-tertiaryoctylacrylamide, N-methylolacrylamide, N-hydroxyethylacrylamide (HEAA), N,N-dimethylacrylamide (DMAA), N,N-diethylacrylamide (DEAA), N,N-dipropylacrylamide, N,N-diisopropylacrylamide, N,N-dibutylacrylamide, N,N-diisobutylacrylamide, N,N-diheptylacrylamide, N,N-dioctylacrylamide, N,N-dimethylolacrylamide, and N,N-dihydroxyethylacrylamide. These can be used individually or in combination of two or more. Among these monomers, N-isopropylacrylamide, N-hydroxyethylacrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide are preferred, with N-hydroxyethylacrylamide being more preferred.

[0028] In formula (2), m=0, n=1, R １ ~R ３ In the case of a hydrogen atom, an example is the N-vinyl carboxylic acid amide represented by the following formula (2-2).

[0029] (In formula (2-2), R ４ ~R ５ (This represents either a hydrogen atom, an alkyl group with 1 to 8 carbon atoms, or a phenyl group.)

[0030] Examples of N-vinyl carboxylic acid amides represented by general formula (2-2) include N-vinylformamide, N-vinylacetamide, N-vinylpropionamide, N-vinylbenzamide, N-vinyl-N-methylformamide, N-vinyl-N-ethylformamide, N-vinyl-N-methylacetamide, and N-vinyl-N-ethylacetamide. Of these, N-vinylacetamide is particularly preferred due to the balance between the hydrophilicity and hydrophobicity of the polymer. N-vinyl carboxylic acid amides may be used alone or in combination. The above N-vinyl carboxylic acid amides do not include those with a cyclic structure.

[0031] The polymer of this embodiment can be produced by known methods, but a polymer that satisfies the above viscosity characteristics can be produced by radical polymerization of the monomer in an aqueous solution using an azo polymer initiator. The aqueous medium is not particularly limited and can be distilled water, deionized water, tap water, etc., but deionized water is preferred.

[0032] The polymerization initiator can be any of those commonly used in the radical polymerization of vinyl compounds, without being limited to any specific type. Examples include redox polymerization initiators, azo compound polymerization initiators, and peroxide polymerization initiators, but in this embodiment, azo compound polymerization initiators are preferred. Molecular weight adjustment may be performed using a chain transfer agent as needed.

[0033] Examples of redox polymerization initiators include combinations of ammonium persulfate with sodium thiosulfate, sodium bisulfate, trimethylamine, or tetramethylethylenediamine, or combinations of t-butyl hydroperoxide with sodium thiosulfate or sodium bisulfate.

[0034] Examples of peroxide-based polymerization initiators include persulfates such as sodium, potassium, and ammonium, and organic peroxides such as benzoyl peroxide, lauroyl peroxide, caproyl peroxide, t-butyl peroctoate, and diacetyl peroxide.

[0035] Examples of azo compound polymerization initiators include 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis(isobutyrate), dimethyl-2,2'-azobis(2-methylbutyrate), and dimethyl-2,2'-azobis(2,4-dimethylpentanoate), 2,2'-azobis(2-amidinopropane) dihydrochloride, and 2,2' Examples include azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] n hydrate, 2,2'-azobis{2-[N-(2-carboxyethyl)amidino]propane} n hydrate, 2,2'-azobis(2-methylpropionic acid)dimethyl, 2,2'-azobis(2-methylpropionic acid)dimethyl, etc.

[0036] Among the polymerization initiators mentioned above, in polymerization methods using water as the solvent, it is most preferable to use 2,2'-azobis[N-(carboxyethyl)-2-methylpropionamidine]tetrahydrate (trade name: VA-057, azo compound polymerization initiator manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), which does not contain halogens, considering the impact of halogen residues in the polymer on coatings and electronic devices, heat resistance, and especially thermal discoloration performance.

[0037] The amount of radical polymerization initiator used is preferably 0.05 parts by mass or more and 2.0 parts by mass or less, more preferably 0.1 parts by mass or more and 0.8 parts by mass or less, and even more preferably 0.4 parts by mass or more and 0.7 parts by mass or less, per 100 parts by mass of all monomers, in the case of azo compound polymerization initiators. In the case of redox polymerization initiators, the amount is preferably 0.001 parts by mass or more and 0.03 parts by mass or less, more preferably 0.003 parts by mass or more and 0.01 parts by mass or less, and even more preferably 0.004 parts by mass or more and 0.009 parts by mass or less, per 100 parts by mass of all monomers. If the amount of radical polymerization initiator used is within the above range, both the polymerization rate and the molecular weight of the copolymer tend to be favorable.

[0038] Within limits that do not impair the objectives of the present invention, chain transfer agents may be used during polymerization for the purpose of adjusting the degree of polymerization of the polymer or introducing modifying groups to the ends of the polymer. Examples of chain transfer agents include aldehyde compounds such as acetaldehyde and propionaldehyde, ketone compounds such as acetone and methyl ethyl ketone, thiol compounds such as 2-hydroxyethanethiol, 3-mercaptopropionic acid, dodecanethiol, and thioacetic acid, halogenated hydrocarbon compounds such as carbon tetrachloride, trichloroethylene, and perchloroethylene, and phosphinate salts such as sodium phosphinate monohydrate. Among these, thiol compounds, aldehyde compounds, and ketone compounds are preferably used. The amount of chain transfer agent added is preferably 0.1% by mass or more and 2.0% by mass or less based on 100 parts by mass of the total amount of all monomers. Within this range, the objectives of adjusting the degree of polymerization and introducing modifying groups to the ends of the polymer can be sufficiently achieved. As for the mixing method, it may be stirred and mixed in the tank, or it may be added at the time of formulation and mixed as part of the formulation.

[0039] The polymerization temperature is preferably 30 to 100°C. More preferably, for high viscosity products it is 40 to 65°C, for medium to low viscosity products it is 60 to 98°C, even more preferably 50 to 60°C for high viscosity products, and most preferably 70 to 95°C for medium to low viscosity products.

[0040] In this manufacturing method, it is preferable to polymerize by dropwise adding a solution containing at least a polymerization initiator to an aqueous medium solution of the monomer. Similarly, if copolymer components are present, it is preferable to dropwise add the aqueous medium solution constituting the copolymer to the aqueous medium solution of the monomer. It is preferable to include a solvent during polymerization. A more preferable solvent is water, and pure water treated with an ionic resin is preferable. Even more preferable is the use of ultrapure water.

[0041] In polymerization, it is preferable to perform polymerization while stirring. Stirring is more preferably carried out using a device equipped with a motor, shaft, and stirring blades to mix the reaction system, and it is particularly preferable to have a device that can vary the stirring speed depending on the progress of the polymerization reaction. Regarding the shape of the stirring blades, there are turbine blades, paddle blades, propeller blades, anchor blades, and three-bladed swept-back blades. While the appropriate blade should be used in each case, anchor blades are preferable for high-viscosity polymers, and three-bladed swept-back blades are preferable for medium to low viscosity polymers. Stirring during the production of the copolymer of the present invention is preferable because it allows for the acquisition of a copolymer with a uniform and appropriate molecular weight distribution.

[0042] The resulting polymer can also be dried and converted into a powder. Specifically, powdering can be done by freeze-drying, drying and solidification grinding, or spray-drying, but spray-drying is the most preferred method.

[0043] (3) Acid cleaning agent The polymer described above is stable in a wide range of conditions, including acidic and alkaline, and can be used in oxidizing and reducing conditions. In particular, it is highly stable even when used with strong acids or highly oxidizing hydrogen peroxide, and therefore has the characteristic of being able to withstand repeated use. For this reason, the polymer of this embodiment can be used as an acid cleaning agent. The acid cleaning agent of this embodiment contains the polymer. Preferred embodiments include, for example, a composition containing hydrogen peroxide and the polymer. Specifically, cleaning agent compositions containing ammonia, hydrogen peroxide, the polymer and water, cleaning agent compositions containing hydrochloric acid, hydrogen peroxide, the polymer and water, cleaning agent compositions containing sulfuric acid, hydrogen peroxide, the polymer and water, and the like can be used.

[0044] Furthermore, this embodiment also includes abrasives containing an abrasive, a reducing agent such as hydrogen peroxide, the polymer, and water, and further containing an acid component such as an inorganic acid such as tungstic acid, hydrofluoric acid, hydrochloric acid, or sulfuric acid, an organic acid such as an amino acid, acetic acid, or oxalic acid, or a dispersant such as ethylene oxides. Such an acid cleaning agent can be used in the polishing and cleaning processes of semiconductor substrates. The above acid cleaning agent can be manufactured by mixing each component using known methods.

[0045] The embodiment will be described in more detail below with reference to examples, but these are illustrative and not limiting to these examples.

[0046] [Example 1] PNVA GE191-107 Low Molecular Weight Type A 1L four-neck separable flask was fitted with a nitrogen gas inlet tube, stirrer, solvent dropper, thermometer, and nitrogen gas exhaust tube. 600g of deionized water was placed in the separable flask, the system was sealed, and the pressure was reduced to 13.3kPa using a vacuum pump while stirring. This process was repeated three times, returning to atmospheric pressure with nitrogen gas. Then, nitrogen was introduced into the system at a rate of 200ml / min while the temperature was raised, and the internal temperature was adjusted to 90.0°C. Simultaneously, 107g of N-vinylacetamide was placed in a 500ml flask, followed by 200g of deionized water, and dissolved and mixed. Next, 3.2 g (2.99% by mass of monomer) of 2,2'-azobis[N-(carboxyethyl)-2-methylpropionamidine]tetrahydrate (product name: VA-057, azo compound polymerization initiator manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., hereinafter also referred to as "initiator VA-057"), which is a polymerization initiator, was weighed into a 200 ml beaker, and 100 g of deionized water was added and dissolved and mixed. Two hours after the start of heating, the VA-057 solution was supplied dropwise to a 1 L flask by pump at an internal temperature of 90.0°C, and then the N-vinylacetamide solution mixed in a 500 ml flask was supplied dropwise by pump. Polymerization was carried out by adding the solutions dropwise while stirring for 2.5 hours at an internal temperature of 90.0 to 95.0°C. Subsequently, the mixture was stirred and held at 90.0–95.0°C for 30 minutes. Then, a solution of 0.5 g of VA-057 dissolved in 55 g of deionized water was supplied by pump, stirred and held at 90.0–95.0°C for 30 minutes, the outside of the container was cooled with 23°C tap water, and allowed to cool until the next day. The viscosity and weight-average molecular weight of the obtained polymer were measured as shown below, and further evaluations were performed on its resistance to hydrogen peroxide solution, ammonia solution, and acid dispersibility retention, and a final judgment was made.

[0047] [Example 2] PDMA107 Low Molecular Weight Type The monomer of Example 1 was changed to N,N-dimethylacrylamide, and a polymer was obtained under the same conditions. The viscosity and weight-average molecular weight of the obtained polymer were measured in the same manner as in Example 1, and further evaluations were performed on hydrogen peroxide aqueous solution resistance, ammonia aqueous solution resistance, and acid dispersibility retention resistance, and a determination was made.

[0048] [Example 3] PDMA043 High Molecular Weight Type A 2L four-neck separable flask was equipped with a nitrogen gas inlet tube, stirrer, solvent dropper, thermometer, and nitrogen gas exhaust tube. 708.0 g of deionized water was added to the separable flask, and 66.1 g of N'N'dimethylacrylamide was dissolved to prepare an aqueous solution. The system was sealed, and the pressure was reduced to 13.3 kPa using a vacuum pump. This process was repeated three times, returning the pressure to atmospheric pressure with nitrogen gas.

[0049] Subsequently, heating was initiated and the internal temperature was adjusted to 53.5°C. Two hours after the start of heating, 10 g of an aqueous solution containing 0.053 g of the initiator VA-057 (0.08% by mass of monomer) was added by syringe, and polymerization was carried out for 4 hours while stirring at an internal temperature of 50.0 to 62.0°C. After that, the bath temperature was raised to 80°C and the internal temperature was maintained at 75°C for 1 hour, at which point 865.4 g of deionized water for dilution was added, stirring was continued for about 1 hour, and then the external temperature of the container was cooled with tap water and allowed to cool until the next day. The viscosity and weight-average molecular weight of the obtained polymer were measured in the same manner as in Example 1, and further evaluations were performed on hydrogen peroxide aqueous solution resistance, ammonia aqueous solution resistance, and acid dispersibility retention resistance, and a determination was made.

[0050] [Comparative Example 1] The following polymer was used, and viscosity and weight-average molecular weight were measured in the same manner as in Example 1. Furthermore, hydrogen peroxide aqueous resistance evaluation, ammonia aqueous resistance evaluation, and acid dispersibility retention evaluation were performed and a determination was made.

[0051] Comparative Example 1: Polyvinyl alcohol: Used in a 5% by mass aqueous solution of POVA PVA124 (Kuraray Co., Ltd.) Comparative Example 2: Polyethylene glycol: Used in a 20% by mass aqueous solution of PEG20000 reagent (Fujifilm Wako Pure Chemical Industries, Ltd.) Comparative Example 3: Polyethylene glycol: Used in a 10% by mass aqueous solution of PEG500000 reagent (Fujifilm Wako Pure Chemical Industries, Ltd.) Comparative Example 4: Polyvinylpyrrolidone: Used in a 10% by mass aqueous solution of PVP K-30 reagent (Nippon Shokubai Co., Ltd.) Comparative Example 5: PNVA GE191-043 High molecular weight type. Obtained by changing the monomer of Example 3 to N-vinylacetamide and polymerizing under the same conditions. Comparative Example 6: Carboxymethylcellulose sodium: Used in a 2% by mass aqueous solution of Sunrose (CMC) 350HC (Nippon Paper Industries Ltd.) Comparative Example 7: Carboxymethylcellulose sodium: Used in a 0.5% by mass aqueous solution of Sunrose (CMC) 200HC (Nippon Paper Industries Ltd.)

[0052] <Viscosity Measurement> Immerse the poly bottle containing the sample in a circulating constant-temperature water bath heated to 20°C, and adjust the internal polymer aqueous solution to 20°C ± 0.5°C. Then, measure the viscosity using a Type B viscometer as specified in JIS K-7117-1-1999. Record the value after 5 minutes at 50 rpm as the measured value.

[0053] Viscosity retention rate % The viscosity retention rate % was calculated using the following formula based on the initial viscosity and the viscosity after the processing described later. A retention rate of 95% or more was judged as ○, and anything below that was judged as ×.

[0054]

[0055] <Molecular Weight Measurement> Each polymer was dissolved in an eluent and allowed to stand for 20 hours. The solid content concentration in this solution was 0.1% by mass. This was filtered through a 0.45 μm membrane filter, and the weight-average molecular weight (Mw) of the filtrate was measured using GPC-MALS (multi-angle light scattering detector). MALS detector: DAWN HELEOS 8+, manufactured by Wyatt Technology Corporation Column: Resonax Shodex® SB-G 8B, SB-807HQ x 2, SB-806M-HQ Column temperature: 40°C Eluent: 0.025 mol sodium bicarbonate, pH adjusted to 9.0 with 0.025 mol sodium carbonate aqueous solution Flow rate: 0.7 mL / min Sample injection volume: 300 μL Laser wavelength: 633 nm Multi-angle fitting method: Zimm method

[0056] Molecular weight retention rate % The molecular weight retention rate was calculated using the following formula based on the initial weight-average molecular weight and the weight-average molecular weight after the processing described later. Samples with a retention rate of 95% or higher were judged as ○, and those below were judged as ×.

[0057]

[0058] <Evaluation of Hydrogen Peroxide Resistance> 88.57 g of the polymer aqueous solution was placed in a 100 ml polypropylene (PP) bottle, and 11.43 g of 35% by mass hydrogen peroxide solution was added on top. After adding the hydrogen peroxide solution, the bottle was tightly sealed and mixed. After standing at room temperature for 2 hours, the initial viscosity and initial molecular weight were measured at a constant temperature of 20°C in a constant temperature bath. After measuring the viscosity and molecular weight, the mixture was left to stand in a constant temperature bath at 23°C, and after one week, the temperature was adjusted to 20°C again and the viscosity was measured. These were taken as the viscosity and molecular weight after the elapsed period.

[0059] <Ammonia Water Resistance Evaluation> 86.67 g of the polymer aqueous solution is placed in a 100 ml polypropylene (PP) bottle, and 13.33 g of 30% by mass ammonia water (also called "ammonia aqueous solution") is added on top. After adding the ammonia water, the bottle is sealed tightly. After standing at room temperature for 2 hours, the initial viscosity is measured when the temperature is adjusted to 20°C in a constant temperature bath. After measuring the viscosity and molecular weight, the mixture is left to stand in a constant temperature bath at 70°C, and after one week, the temperature is adjusted to 20°C again and the viscosity is measured. These are considered the viscosity and molecular weight after the passage of time.

[0060] <Resistance retention rate determination> The following criteria were used for determination: ○: Viscosity retention rate of 95% or more and 105% or less, and molecular weight retention rate of 95% or more and 105% or less ×: Those that do not meet the above criteria

[0061] <Evaluation of Acid Resistance and Dispersibility> 85 g of polymer aqueous solution was placed in a 100 ml polypropylene bottle. Next, 10 g of cerium oxide (OPSN-0090-1-15, Outrun Co., Ltd.) dispersion was added and mixed. 1 mol / L nitric acid (Kanto Chemical Co., Ltd. reagent) was added dropwise to the homogenized slurry by stirring to adjust the pH to 2.5, and the mixture was left to stand for 10 minutes. The initial state was observed using the following method. Approximately 0.5 g of the homogenized dispersion was taken with a dropper and dropped onto a 20 μm objective micrometer with a grid. The dispersion was spread uniformly and evaluated according to the following criteria.

[0062] Subsequently, the container holding the sample is left undisturbed in an oven preheated to 70°C for 30 days. After 30 days, it is removed from the oven, allowed to cool, and the dispersion state is checked using the method described above.

[0063] Judgment Criteria ○: No particles larger than 20 μm ×: Particles larger than 20 μm are present

[0064] <Overall Assessment> The overall assessment was made based on the following criteria: ○: Viscosity retention rate, molecular weight retention rate, and acid resistance dispersibility evaluation all passed. ×: Other than the above.

[0065]

[0066] As shown in Table 1, the polymer of this embodiment exhibits high resistance to hydrogen peroxide and ammonia. Furthermore, it maintains its dispersion and retention ability even under high-temperature nitric acid, which has a high oxidizing power. Thus, the polymer of this embodiment is a material that can be continuously used even in environments that are harsh on amphiphilic polymers, such as hydrogen peroxide water and ammonia water, and can be said to be an extremely useful amphiphilic polymer for the semiconductor field.

Claims

1. A polymer containing a constituent unit represented by the following formula (1), wherein the viscosity of a 10% by mass aqueous solution is 10 mPa·s or more. (In equation (1), m and n are 0 or 1, and m + n = 1, R １ ~R ５ (This represents one of the following: a hydrogen atom, an alkyl group or hydroxyalkyl group having 1 to 8 carbon atoms, or a phenyl group.) 2. In the above equation (1), m = 1, R １ ~R ３ is a hydrogen atom, R ４ ~R ５ The polymer according to claim 1, wherein is an alkyl group or hydroxyalkyl group having 1 to 8 carbon atoms.

3. When m = 0 and n = 1, R １ ~R ３ is a hydrogen atom, and R ４ ~R ５ is either a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group, and the viscosity of a 10% by mass aqueous solution is 10 mPa·s or more and less than 2000 mPa·s, or the viscosity of a 4% by mass aqueous solution is 500 mPa·s or more and less than 50000 mPa·s. The polymer according to claim 1.

4. The polymer according to claim 2, wherein the weight-average molecular weight is 1,000 to 6,000,000.

5. The polymer according to claim 3, wherein the weight-average molecular weight is 300,000 or less.

6. An acid cleaning agent comprising the polymers of claims 1 to 5.

7. The acid cleaning agent according to claim 6, further comprising hydrogen peroxide.

8. The monomer represented by the following formula (2) is used in an aqueous solution using an aqueous medium. A method for producing a polymer by radical polymerization using an azo polymer initiator. (In formula (2), m and n are 0 or 1, and m + n = 1, R １ ~R ５ (This represents a hydrogen atom, an alkyl group or hydroxyalkyl group having 1 to 8 carbon atoms, or an alkyl group of a phenyl group.) 9. In equation (2) above, m = 1, R １ ~R ３ is a hydrogen atom, R ４ ~R ５ A method for producing the polymer according to claim 8, wherein is an alkyl group having 1 to 8 carbon atoms.

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