JP2008303315A - New vinyl ether copolymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for forming a resist protective film for immersion lithography, for forming a protective film that has high water repellency against water or an immersion medium essentially comprising water, is easily peeled by a developer solution and does not cause mixing with a photoresist layer. <P>SOLUTION: A vinyl ether copolymer is disclosed, which has a vinyl ether structural unit expressed by general formula (1) (wherein Y represents an alkylene group, an alkyleneoxy group or an alkyleneoxyalkyl group, Z represents a 6-15C monocyclic or condensed polycyclic or crosslinked polycyclic alicyclic group which may have a substituent, and n represents 0 or 1) and a maleimide structural unit expressed by general formula (2) (wherein each of R<SP>13</SP>and R<SP>14</SP>independently represents a hydrogen atom, a 1-5C chain or cyclic hydrocarbon group, an entirely or partially fluorinated 1-5C chain or cyclic hydrocarbon group or a halogen atom). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a novel vinyl ether copolymer containing alicyclic vinyl ethers and maleimides as constituent units, and a method for producing the same. The vinyl ether copolymer of the present invention has a high water repellency and can provide a resin film soluble in an alkaline solution, and is particularly useful as a material for forming a protective film for an immersion resist.

  In lithography used for the manufacture of semiconductor elements, the formation of finer patterns is required as the degree of integration increases. Shortening the wavelength of the exposure light source is indispensable for pattern miniaturization, but now lithography using krypton fluoride (KrF) excimer laser light (wavelength 248 nm) is becoming the mainstream, and argon fluoride (ArF) excimer laser Lithography using light (wavelength 193 nm) with a line width of 100 nm or less has also been put into practical use. Furthermore, lithography technology using fluorine dimer (F2) excimer laser light (wavelength 157 nm), extreme ultraviolet light (EUV), X-rays, electron beams, etc. is in the development stage.

  Recently, immersion lithography has been proposed as a means for extending the life of exposure technology using an ArF excimer laser. This is a process of impregnating water or an immersion medium containing water as a main component between the photoresist film formed on the wafer at the time of exposure and the lens of the exposure apparatus. Since the components such as the photoacid generator in the photoresist layer are eluted in the immersion medium because they are in contact with the immersion medium, or the immersion medium is absorbed in the photoresist layer, the sensitivity is reduced. There was a problem of causing fluctuations in resolution. Further, since the impregnated immersion fluid remains on the resist layer, there is a problem that a pattern defect peculiar to immersion lithography which is not observed in dry exposure occurs.

In order to solve these problems related to the immersion lithography, a method of forming a protective film on the upper layer of the photoresist film has been proposed for the purpose of protecting the photoresist film from the immersion medium (Patent Document 1, Non-Patent Document 1). Reference 1).
This protective film ensures sufficient transparency with respect to the exposure wavelength to be used, and can form a protective film stably without causing intermixing with the photoresist layer. For example, water or water is the main component. It is required to have sufficient resistance to the immersion medium, have high water repellency to the immersion medium, and can be easily peeled off by a release agent or developer.
International Publication No. 2004/074937 Pamphlet Nikkei Microdevice April 2004 issue

  The present invention has been made in order to overcome the above-described circumstances, has high water repellency with respect to water or an immersion medium for water, is easily peeled off by a developer, and is mixed with a photoresist layer. It is an object of the present invention to provide a resist protective film forming material for immersion lithography for forming a protective film that does not cause erosion.

  As a result of intensive studies in view of the above problems, the present inventors have found a copolymer comprising at least a vinyl ether structural unit represented by the following general formula (1) and a maleimide structural unit represented by the following general formula (2). The present inventors have found that a resist protective film using a protective film forming material containing water has water repellency with respect to water or an immersion medium containing water as a main component and can be easily peeled off with an alkali developer.

That is, the present invention provides at least the following general formula (1)

Wherein Y represents an alkylene group, an alkyleneoxy group or an alkyleneoxyalkyl group, and Z represents a monocyclic, condensed polycyclic or bridged polycyclic having 6 to 15 carbon atoms which may have a substituent. A vinyl ether structural unit represented by the following formula: n represents 0 or 1;
The following general formula (2):

(Wherein R ¹³ and R ¹⁴ are each independently a hydrogen atom, a chain or cyclic hydrocarbon group having 1 to 5 carbon atoms, a completely or partially fluorinated chain structure having 1 to 5 carbon atoms, or The present invention provides a vinyl ether copolymer having a maleimide-based structural unit represented by a cyclic hydrocarbon group or a halogen atom and a method for producing the same.

  The present invention also provides a resist protective film forming material for immersion lithography comprising the above vinyl ether copolymer, and immersion lithography formed by applying and drying the material on a photoresist film. A resist protective film is provided.

  The resist upper layer film formed of the resist protective film forming material for immersion lithography containing the novel vinyl ether copolymer of the present invention prevents the resist layer from being violated by water or an immersion medium mainly composed of water, and It can be easily peeled off with an alkali developer. Therefore, it can be used very suitably for the manufacture of semiconductor devices which are expected to be further miniaturized in the future.

  The novel vinyl ether copolymer of the present invention has at least the following general formula (1)

Wherein Y represents an alkylene group, an alkyleneoxy group or an alkyleneoxyalkyl group, and Z represents a monocyclic, condensed polycyclic or bridged polycyclic having 6 to 15 carbon atoms which may have a substituent. A vinyl ether structural unit represented by the following formula: n represents 0 or 1;
The following general formula (2):

(Wherein R ¹³ and R ¹⁴ are each independently a hydrogen atom, a chain or cyclic hydrocarbon group having 1 to 5 carbon atoms, a completely or partially fluorinated chain structure having 1 to 5 carbon atoms, or A maleic structural unit represented by a cyclic hydrocarbon group or a halogen atom.

In general formula (1), the alkylene group represented by Y is preferably a linear or branched alkylene group having 1 to 6 carbon atoms, more preferably a linear alkylene group having 1 to 6 carbon atoms, particularly A methylene group, an ethylene group, a trimethylene group and a tetramethylene group are preferred. The alkylene group is preferably a C ₂ -C ₄ alkyleneoxy group, particularly an ethyleneoxy group, trimethylene group is preferred. The alkyleneoxy alkyl group, preferably a C ₂ -C ₄ alkyleneoxy -C ₂ -C ₄ alkyl group, ethyleneoxy ethyl ethyleneoxy propyl group, propyleneoxy ethyl, propyleneoxy propyl group and the like.

  The alicyclic group represented by Z is preferably a condensed polycyclic or bridged polycyclic alicyclic group having 6 to 15 carbon atoms, specifically, a tricyclodecanyl group, a tetracyclodecanyl group, a tetracyclo group. A dodecanyl group, a pentacyclopentadecanyl group, an adamantyl group, etc. are mentioned. These alicyclic groups include an alkyl group having 1 to 6 carbon atoms, a fluorine atom, an alkyl group having 1 to 6 carbon atoms which is fluorinated all or part, a hydroxyl group, an acetal-protected hydroxyl group, and a carbon number. 1 to 5 alkoxy groups, carboxyl groups, nitrile groups, etc. may be substituted. As a substituent on these alicyclic groups, an alkyl group having 1 to 6 carbon atoms is particularly preferable.

  Of the structural units represented by the general formula (1), a structural unit represented by the following formula is particularly preferred.

In the general formula (2), as the chain-like or cyclic hydrocarbon group having 1 to 5 carbon atoms represented by R ¹³ and R ^14, straight-chain or branched alkyl group having 1 to 5 carbon atoms, carbon atoms 3 to 5 cycloalkyl groups are preferable, and specific examples include a methyl group, an ethyl group, an isopropyl group, a cyclopropyl group, and a cyclopentyl group. Examples of the completely or partially fluorinated linear or cyclic hydrocarbon group having 1 to 5 carbon atoms include a fluorinated linear or branched alkyl group having 1 to 5 carbon atoms, fluorinated A C3-C5 cycloalkyl group is mentioned, Specifically, a trifluoromethyl group, a tetrafluoroethyl group, etc. are mentioned. Examples of the halogen atom include fluorine, chlorine, bromine and iodine. Of these R ¹³ and R ¹⁴ , an alkyl group having 1 to 5 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, and a halogen atom are particularly preferable.

  Moreover, among the structural units represented by the general formula (2), a structural unit represented by the following formula is particularly preferable.

  The copolymer of the present invention may be a copolymer containing structural units other than the above general formulas (1) and (2) in order to adjust the performance as a protective film used in immersion lithography. .

  The structural unit other than the general formulas (1) and (2) is not particularly limited as long as it is a structural unit obtained from a monomer having a polymerizable unsaturated double bond. 1), (meth) acrylic acid derivative (monomer 2), dicarboxylic acid derivative (monomer 3), N-substituted maleimide derivative (monomer 4), styrene derivative (monomer 5), etc. The structural unit obtained by copolymerizing with a monomer is mentioned.

  Examples of the monomer 1 include a chain alkyl vinyl ether which may have a substituent. Specific examples thereof include n-butyl vinyl ether, t-butyl vinyl ether, ethyl vinyl ether, triethylene glycol monovinyl ether, diethylene glycol monoester. Examples include vinyl ether, hydroxyethyl vinyl ether, dihydrofuran, dihydropyran, 2,2,2-trifluoroethyl vinyl ether, and ethyl trifluorovinyl ether. Examples of the monomer 2 include (meth) acrylate, and specific examples thereof include methyl (meth) acrylate, γ-butyrolactone (meth) acrylate, norbornalactone (meth) acrylate, and tricyclodecanyl (meth) acrylate. , Adamantyl (meth) acrylate, methyladamantyl (meth) acrylate, hydroxyadamantyl methacrylate, trifluoromethyl (meth) acrylate, and the like. Examples of the monomer 3 include anhydrides such as maleic acid, fumaric acid, and itaconic acid or esters thereof, and specific examples thereof include maleic anhydride, dimethyl maleate, diethyl fumarate, diethyl itaconate, and the like. It is done. Specific examples of the monomer 4 include N-hydroxymaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-adamantylmaleimide and the like. Specific examples of the monomer 5 include styrene, p-hydroxystyrene, m-hydroxystyrene, acetoxystyrene, t-butoxystyrene, t-butoxycarbonyloxystyrene, trimethylsilyloxystyrene, α-methylstyrene, and the like. .

  Of these monomers, monomer 3 (dicarboxylic acid derivative), further an anhydride of dicarboxylic acid is preferable, and maleic anhydride is particularly preferable.

  The composition of the structural unit of the copolymer of the present invention can be selected within a range that does not impair the performance as a protective film used in immersion lithography. For example, the structural unit (general formula (1)) is usually 20 to 80 mol%, preferably 30 to 70 mol%, more preferably 40 to 60 mol%. Moreover, the said structural unit (General formula (2)) is 20-80 mol% normally, Preferably it is 30-70 mol%, More preferably, it is 40-60 mol%. Moreover, the monomer 1-the monomer 5 are 0-60 mol% normally, Preferably it is 0-50 mol%, More preferably, it is 0-20 mol%. Among these, those containing 0 to 20 mol% of the monomer 3 are particularly preferable.

  When the copolymer of the present invention is used for a resist protective film forming material for immersion lithography, the weight average molecular weight is preferably 2,000 to 100,000, and preferably 4,000 to 50,000. If the weight average molecular weight is too small, mixing with the resist film is likely to occur, and resistance to an immersion medium such as water decreases. On the other hand, if the weight average molecular weight is too large, the solubility in an organic solvent, which will be described later, is lowered, causing a problem in film formability. The polydispersity (Mw / Mn) of the resin is usually 1-5.

  The vinyl ether copolymer of the present invention can be obtained by radical polymerization of vinyl ether monomers and maleimide monomers corresponding to the general formulas (1) and (2). Moreover, 1 type (s) or 2 or more types of monomers can be used for the vinyl ether type monomer and maleimide type monomer which are used for superposition | polymerization, respectively.

  The vinyl ether monomer is represented by the following general formula (3).

(Wherein Y and Z are the same as above)

  More preferable vinyl ether monomers include those represented by the following formula.

  The maleimide monomer is represented by the following general formula (4).

(Wherein R ¹³ and R ¹⁴ are the same as above)

  More preferred maleimide monomers include those represented by the following formula.

  The copolymer of the present invention can be synthesized by general radical polymerization. The polymerization initiator to be used is not particularly limited as long as it is a normal radical generator, but 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, dimethyl-2, Azo compounds such as 2′-azoisobutyrate, 1,1′-azobis-1-cyclohexanenitrile, 4,4′-azobis-4-cyanovaleric acid; decanoyl peroxide, lauroyl peroxide, benzoyl peroxide , 3,5,5-trimethylhexaloyl peroxide, succinic acid peroxide, tert-butylperoxy-2-ethylhexanoate and the like can be used alone or in combination.

  The polymerization solvent is not particularly limited as long as it can dissolve the monomer and the polymer. For example, ketones such as acetone, methyl ethyl ketone, and methyl amyl ketone; ethers such as tetrahydrofuran, dioxane, glyme, and propylene glycol monomethyl ether; ethyl acetate, ethyl lactate, and the like Esters; ether esters such as propylene glycol methyl ether acetate; lactones such as γ-butyrolactone, and the like can be used alone or in combination.

  The polymerization method is not particularly limited as long as radical polymerization is possible, but all monomers, initiators, chain transfer agents are dissolved in a polymerization solvent and heated to the polymerization temperature, so-called batch polymerization method, monomers, initiators. Further, it can be achieved by a so-called dropping polymerization method in which a part or all of the chain transfer agent is dropped into a polymerization system heated to a polymerization temperature.

  The polymerization temperature is selected depending on the boiling point of the polymerization solvent to be used, the half-life temperature of the polymerization initiator, and the like, but in general, a range of 60 to 100 ° C, preferably 70 to 90 ° C is selected. The polymerization time is 1 to 24 hours, preferably 2 to 20 hours.

  After the polymerization, reprecipitation with a poor solvent alone or a mixed solvent of a poor solvent and a good solvent and washing as necessary to purify the polymer. By this operation, unnecessary substances such as unreacted monomers, oligomers, polymerization initiators and residues thereof are removed. The poor solvent is not particularly limited as long as it is a solvent in which the polymer is difficult to dissolve. For example, water, alcohols such as methanol and isopropanol, and hydrocarbons such as hexane and heptane can be selected. The good solvent is not particularly limited as long as it is a solvent in which a monomer, an oligomer, a polymerization initiator and a residue thereof are easily dissolved, but the same as the polymerization solvent is preferable in terms of management of the production process.

  Since the purified polymer contains the solvent used for purification, it is dissolved in a solvent for forming a protective film for immersion lithography after drying under reduced pressure, or dissolved in a good solvent such as the solvent or polymerization solvent. Then, after adding the solvent or supplying it as necessary, the other solvent is distilled off under reduced pressure.

  The copolymer having the structural units represented by the general formula (1) and the general formula (2), which are the main components of the resist protective film forming material for immersion lithography of the present invention, may be contained alone or in combination of two or more. The solid content concentration of these copolymers may be any concentration that can be coated on the photoresist layer, specifically 0.1 to 40% by weight, preferably 1 to 30% by weight. It is.

  The organic solvent constituting the protective film-forming material degrades the lithography performance without easily dissolving the copolymer and without dissolving the resist when the coating film is dried on the photoresist film. It can be used. As such an organic solvent, a chain or cyclic hydrocarbon having 5 to 20 carbon atoms or a partially fluorinated chain or cyclic hydrocarbon having 5 to 20 carbon atoms is preferably used.

  Specific examples of the hydrocarbon or fluorinated hydrocarbon include, for example, pentane, hexane, octane, decane, 2-methyl-butane, cyclohexane, cyclooctane, decalin, perfluorohexane, perfluoroheptane, and the like. Can be used alone or as a mixed solvent of two or more.

  Moreover, in order to adjust applicability | paintability, organic solvents other than the said solvent can be included. Examples of organic solvents other than the above solvents include methanol, ethanol, isopropanol, n-butanol, t-butanol, 2-methyl-2-butanol, ethylene glycol, propylene glycol, tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, Examples include propylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, toluene, xylene, ethyl acetate, and butyl acetate. These blending ratios are preferably 30% by weight or less, more preferably 10% by weight or less in the solvent component. If the amount of these solvents is too large, problems such as dissolution of the photoresist layer occur when the protective film forming material is applied to the upper layer of the photoresist, and the pattern shape is deteriorated.

  Furthermore, the protective film-forming material of the present invention can appropriately contain an additive such as a surfactant for the purpose of improving coating properties. Examples of the additive include BM-1000 (manufactured by BM Chemie), Surflon S-112, S-141 (manufactured by Asahi Glass Co., Ltd.), and the like.

  Moreover, the material for forming a protective film of the present invention is preferably as less as possible for impurities such as metals, and this can improve the yield in the manufacture of semiconductor elements. Therefore, impurities such as metals are preferably 100 ppm or less, particularly 10 ppm or less.

  The protective film of the present invention can be obtained by applying and drying the protective film-forming material on the photoresist upper layer. The method of coating and drying is preferably a spin coating method in which a wafer is rotated and coated and dried from the viewpoint of productivity. The thickness of the protective film is not particularly limited as long as it is a thickness suitable for manufacturing a semiconductor element, but is preferably 1 to 500 nm, more preferably 10 to 200 nm. If the film thickness is too thin, the resist cannot be protected from an immersion medium such as water, and the photoacid generator in the resist layer is eluted, resulting in a deterioration of the pattern shape. Further, from the viewpoint of the transmittance of the protective film, if the film thickness is too thick, the sensitivity is greatly lowered and the productivity is lowered.

  Although the drying temperature for forming this protective film is not specifically limited, For example, it forms by performing for 20 to 120 seconds, Preferably it is 20 to 90 second on the temperature conditions of 70 to 150 degreeC, Preferably it is 80 to 140 degreeC. Is done.

  The protective film of the present invention has high water repellency. That is, the contact angle of the protective film of the present invention with respect to pure water is preferably 60 ° or more, particularly preferably 65 ° or more.

  The protective film of the present invention can be easily peeled off with an alkaline developer. The alkali developer that can be used is not particularly limited as long as it does not dissolve the photoresist film, but an aqueous tetramethylammonium hydroxide solution is preferably used. For example, the dissolution rate of the protective film of the present invention with a 2.38% tetramethylammonium hydroxide aqueous solution is preferably 25 nm / sec or more, particularly preferably 50 nm / sec or more. Specifically, the protective film can be peeled off by immersion treatment or the like.

  Examples of the present invention will be described below, but the scope of the present invention is not limited to these examples.

Example 1
Synthesis of tricyclodecanyl vinyl ether / maleimide copolymer

In a 100 mL eggplant-shaped flask equipped with a stirrer, 10.02 g of tricyclodecanyl vinyl ether (hereinafter TCDVE), 31.39 g of tetrahydrofuran (hereinafter THF), 5.45 g of maleimide (hereinafter MI), 2,2′-azobis ( 1.82 g of dimethyl (isobutyrate) (hereinafter referred to as MAIB) was added, immersed in an oil bath heated to 80 ° C. with a cooling tube attached, and aged for 6 hours. The obtained polymerization solution was put into 195 g of hexane to precipitate the resin, and then the resin was filtered off using a filter paper with 1 micron retention particles. Thereafter, the resin was dried under reduced pressure at 1 torr and 60 ° C. for 12 hours to obtain 13.53 g of resin. Table 1 shows the average composition calculated from the integration ratio of ¹³ C-NMR and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) by GPC analysis (polystyrene conversion).

Example 2
Synthesis of tricyclodecanyl vinyl ether / maleimide / maleic anhydride copolymer

Into a 100 mL eggplant-shaped flask equipped with a stirrer was charged 10.08 g of TCDVE, 31.55 g of THF, 4.35 g of MI, 1.11 g of maleic anhydride (hereinafter referred to as MAH) and 1.81 g of MAIB. And was aged for 6 hours. The obtained polymerization solution was put into 175 g of hexane to precipitate the resin, and then the resin was filtered off using a filter paper with 1 micron retention particles. Thereafter, the resin was dried under reduced pressure at 1 torr and 60 ° C. for 12 hours to obtain 13.39 g of resin. Table 1 shows the average composition calculated from the integration ratio of ¹³ C-NMR and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) by GPC analysis (polystyrene conversion).

Example 3
Synthesis of tricyclodecanyl vinyl ether / maleimide / maleic anhydride copolymer TCDVE was changed to 10 g, MI 3.81 g, MAH 1.65 g, THF 31.41 g, MAIB 1.81 g and hexane 177 g. Otherwise, the same procedure as in Example 2 was performed to obtain 13.23 g of resin. Table 1 shows the average composition calculated from the integration ratio of ¹³ C-NMR and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) by GPC analysis (polystyrene conversion).

Example 4
Synthesis of tricyclodecanyl vinyl ether / maleimide copolymer In a 500 mL beaker equipped with a stirrer, 30.01 g of TCDVE, 16.34 g of MI, 70.56 g of THF, and 5.43 g of MAIB were added and stirred to completely dissolve. This is designated as Droplet 1. In a 200 mL three-necked flask equipped with a stirrer, 25.52 g of THF was charged, a condenser tube was attached, and immersed in an oil bath heated to 80 ° C. When THF began to reflux, the dropping liquid 1 was added over 2 hours, and then aged for 3 hours. The obtained polymerization liquid was put into 425 g of hexane to precipitate the resin, and the resin was filtered off using a filter paper having 1 micron retained particles. The obtained resin was again put into the same amount of hexane, stirred and filtered, and the resulting wet cake was dried under reduced pressure at 1 torr and 60 ° C. for 12 hours to obtain 36.65 g of resin. Table 1 shows the average composition calculated from the integration ratio of ¹³ C-NMR and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) by GPC analysis (polystyrene conversion).

Example 5
Synthesis of tricyclodecanyl vinyl ether / maleimide / maleic anhydride copolymer A 500 mL beaker equipped with a stirrer was charged with TCDVE 30.00 g, MI 13.07 g, THF 74.60 g, MAH 3.28 g, MAIB 5.43 g, and stirred completely. Dissolved. This is designated as Droplet 1. A 200 mL three-necked flask equipped with a stirrer was charged with 23.58 g of THF, fitted with a condenser, and immersed in an oil bath heated to 80 ° C. When THF began to reflux, the dropping liquid 1 was added over 2 hours, and then aged for 3 hours. The obtained polymerization solution was added to 418 g of hexane to precipitate the resin, and the resin was filtered off using a filter paper having 1 micron retained particles. The obtained resin was again put into the same amount of hexane, stirred and filtered, and the wet cake obtained was dried under reduced pressure at 1 torr and 60 ° C. for 12 hours to obtain 37.91 g of resin. Table 1 shows the average composition calculated from the integration ratio of ¹³ C-NMR and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) by GPC analysis (polystyrene conversion).

Example 6
Synthesis of Tricyclodecanyl Vinyl Ether / Maleimide Copolymer A 200 mL beaker equipped with a stirrer was charged with 16.34 g of MI, 52.10 g of THF, and 5.45 g of MAIB, and stirred to completely dissolve. This is designated as Droplet 1. A 200 mL three-necked flask equipped with a stirrer was charged with 29.97 g of TCDVE and 17.32 g of THF, fitted with a condenser, and immersed in an oil bath heated to 80 ° C. When THF began to reflux, the dropping liquid 1 was added over 2 hours, and then aged for 3 hours. The obtained polymerization solution was added to 353 g of hexane to precipitate the resin, and the resin was filtered off using a filter paper having 1 micron retained particles. The obtained resin was again put into the same amount of hexane, stirred and filtered, and the resulting wet cake was dried under reduced pressure at 1 torr and 60 ° C. for 12 hours to obtain 46.57 g of resin. Table 1 shows the average composition calculated from the integration ratio of ¹³ C-NMR and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) by GPC analysis (polystyrene conversion).

Example 7
Synthesis of Tricyclodecanyl Vinyl Ether / Maleimide Copolymer A 200 mL beaker equipped with a stirrer was charged with 12.69 g of MI, 40.49 g of THF, 4.21 g of MAIB, and 0.72 g of mercaptoethanol, and completely dissolved by stirring. This is designated as Droplet 1. A 200 mL three-necked flask equipped with a stirrer was charged with 23.30 g of TCDVE and 13.53 g of THF, fitted with a condenser, and immersed in an oil bath heated to 80 ° C. When THF began to reflux, the dropping liquid 1 was added over 2 hours, and then aged for 3 hours. The obtained polymerization solution was put into 273 g of hexane to precipitate the resin, and the resin was filtered off using a filter paper having 1 micron retained particles. The obtained wet cake was dried under reduced pressure at 1 torr and 60 ° C. for 12 hours to obtain 34.31 g of resin. Table 1 shows the average composition calculated from the ¹³ C-NMR integration ratio and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) as determined by GPC analysis (polystyrene conversion).

Example 8
Synthesis of tricyclodecanyl vinyl ether / maleimide copolymer A 200 mL beaker equipped with a stirrer was charged with 16.32 g of MI, 52.14 g of THF, 5.43 g of MAIB, and 1.42 g of pentaerythritol tetra (mercaptoacetate). Dissolved in. This is designated as Droplet 1. A 200 mL three-necked flask equipped with a stirrer was charged with 30.00 g of TCDVE and 17.51 g of THF, attached with a condenser, and immersed in an oil bath heated to 80 ° C. When THF began to reflux, the dropping liquid 1 was added over 2 hours, and then aged for 3 hours. The obtained polymerization liquid was put into 357 g of hexane to precipitate the resin, and the resin was filtered off using a filter paper having retention particles of 1 micron. The obtained wet cake was dried under reduced pressure at 1 torr and 60 ° C. for 12 hours to obtain 45.08 g of resin. Table 1 shows the average composition calculated from the ¹³ C-NMR integration ratio and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) as determined by GPC analysis (polystyrene conversion).

Example 9
Synthesis of tetracyclododecanyl vinyl ether / maleimide copolymer

A 20 mL eggplant-shaped flask equipped with a stirrer was charged with 2.99 g of tetracyclododecanyl vinyl ether (DMONVE), 8.99 g of THF, 1.43 g of MI, and 0.47 g of MAIB, and was heated to 70 ° C. with a condenser tube attached. It was immersed in an oil bath and aged for 6 hours. The obtained polymerization liquid was put into 42 g of hexane to precipitate the resin, and then the resin was filtered off using a filter paper having 1 micron retention particles. Thereafter, the resin was dried under reduced pressure at 1 torr and 60 ° C. for 12 hours to obtain 2.7 g of resin. Table 1 shows the average composition calculated from the integration ratio of ¹³ C-NMR and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) by GPC analysis (polystyrene conversion).

Comparative Example 1
Synthesis of tricyclodecanyl vinyl ether / maleic anhydride copolymer

TCDVE10.01g, THF31.59g, MAH5.50g, MAIB1.81g was put into a 100mL eggplant-shaped flask equipped with a stir bar, immersed in an oil bath heated to 80 ° C with a condenser tube, and aged for 6 hours I let you. The obtained polymerization solution was put into 156 g of methanol to precipitate the resin, and then the resin was filtered off using a filter paper having 1 micron retained particles. Thereafter, the resin was dried under reduced pressure at 1 torr and 60 ° C. for 12 hours to obtain 11.73 g of resin. Table 1 shows the average composition calculated from the integration ratio of ¹³ C-NMR and the weight molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn) by GPC analysis (polystyrene conversion).

Evaluation of a resist protective film forming material for immersion lithography was performed by the following method.
(1) Evaluation of water repellency The resin obtained in Example 1 was dissolved in propylene glycol monomethyl ether acetate and adjusted to a concentration of 25% by weight. The obtained adjustment liquid was spin-coated on a silicon wafer and then baked at 90 ° C. for 60 seconds to produce a thin film having a thickness of 1 μM. 3 μL of pure water was deposited on the coating film, and the contact angle was measured. For the contact angle measurement, a contact angle measuring device (FAMAS) manufactured by Kyowa Interface Science Co., Ltd. was used. The contact angles of the resins obtained in Examples 2 to 10 and Comparative Example 1 were also measured in the same manner. The results are shown in Table 2.

(2) Evaluation of alkali developer solubility The resin obtained in Example 1 was dissolved in propylene glycol monomethyl ether acetate and adjusted to a concentration of 25% by weight. The obtained adjustment liquid was spin-coated on a silicon wafer and then baked at 90 ° C. for 60 seconds to produce a thin film having a thickness of 1 μM. 2.38% tetramethylammonium hydroxide was used as a developer, and the alkali dissolution rate of the thin film was measured. The dissolution rate was measured using Resotech Japan Co., Ltd. resist development analyzer RDA-812. The results are shown in Table 2.

  Since the vinyl ether copolymer of the present invention has high water repellency and is soluble in an alkaline developer, it is useful as a resist protective film forming material for immersion lithography, and further miniaturization is expected in the future. It can be used very suitably for the manufacture of semiconductor devices.

Claims (7)

At least the following general formula (1)

Wherein Y represents an alkylene group, an alkyleneoxy group or an alkyleneoxyalkyl group, and Z represents a monocyclic, condensed polycyclic or bridged polycyclic having 6 to 15 carbon atoms which may have a substituent. A vinyl ether structural unit represented by the following formula: n represents 0 or 1;
The following general formula (2):

(Wherein R ¹³ and R ¹⁴ are each independently a hydrogen atom, a chain or cyclic hydrocarbon group having 1 to 5 carbon atoms, a completely or partially fluorinated chain structure having 1 to 5 carbon atoms, or A vinyl ether copolymer having a maleimide structural unit represented by a cyclic hydrocarbon group or a halogen atom. The vinyl ether copolymer according to claim 1, wherein the general formula (1) as a structural unit is selected from the following formulas of at least one kind or two or more kinds.

The vinyl ether copolymer according to any one of claims 1 and 2, wherein the general formula (2) as a structural unit is selected from the following formulas of at least one kind or two or more kinds.

  Furthermore, the vinyl ether copolymer of any one of Claims 1-3 which has a structural unit derived from a dicarboxylic acid anhydride. At least the following general formula (3)

Wherein Y represents an alkylene group, an alkyleneoxy group or an alkyleneoxyalkyl group, and Z represents a monocyclic, condensed polycyclic or bridged polycyclic having 6 to 15 carbon atoms which may have a substituent. A vinyl ether monomer represented by the following formula: n represents 0 or 1;
The following general formula (4)

(Wherein R ¹³ and R ¹⁴ are each independently a hydrogen atom, a chain or cyclic hydrocarbon group having 1 to 5 carbon atoms, a completely or partially fluorinated chain structure having 1 to 5 carbon atoms, or The method for producing a vinyl ether copolymer according to any one of claims 1 to 4, wherein a maleimide monomer represented by a cyclic hydrocarbon group or a halogen atom is subjected to radical polymerization.   A material for forming a resist protective film for immersion lithography, comprising the copolymer according to claim 1.   A resist protective film for immersion lithography formed by applying and drying the resist protective film forming material for immersion lithography according to claim 6 on a photoresist film.