JP4635614B2 - Copolymer and resin composition for immersion film - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is useful for protecting a photoresist film during immersion exposure used for lithography miniaturization and forming an upper layer film that suppresses elution of a photoresist film component and protects a lens of a projection exposure apparatus. The present invention relates to an upper layer film-forming composition for immersion and a copolymer used therefor.

Stepper-type or step-and-scan projection exposure apparatus for transferring a reticle pattern as a photomask to each shot area on a photoresist-coated wafer via a projection optical system when manufacturing a semiconductor element or the like Is used.
The resolution of the projection optical system provided in the projection exposure apparatus becomes higher as the exposure wavelength used is shorter and the numerical aperture of the projection optical system is larger. For this reason, with the miniaturization of integrated circuits, the exposure wavelength, which is the wavelength of radiation used in the projection exposure apparatus, has become shorter year by year, and the numerical aperture of the projection optical system has also increased.
Further, when performing exposure, the depth of focus is important as well as the resolution. The resolution R and the depth of focus δ are each expressed by the following equations.
R = k1 · λ / NA (i)
δ = k2 · λ / NA ² (ii)
Here, λ is the exposure wavelength, NA is the numerical aperture of the projection optical system, and k1 and k2 are process coefficients. In order to obtain the same resolution R, a larger depth of focus δ can be obtained by using radiation having a short wavelength.

In this case, a photoresist film is formed on the exposed wafer surface, and the pattern is transferred to the photoresist film. In a conventional projection exposure apparatus, a space in which a wafer is placed is filled with air or nitrogen. At this time, when the space between the wafer and the lens of the projection exposure apparatus is filled with a medium having a refractive index n, the resolution R and the depth of focus δ are expressed by the following equations.
R = k1 · (λ / n) / NA (iii)
δ = k2 · nλ / NA ² (iv)
For example, when water is used as the medium in the ArF process, if the refractive index n = 1.44 of light having a wavelength of 193 nm is used, the resolution R is 69.compared to the exposure using air or nitrogen as the medium. 4% (R = k1 · (λ / 1.44) / NA), and the focal depth is 144% (δ = k2 · 1.44λ / NA ² ).
A projection exposure method capable of shortening the wavelength of radiation for exposure and transferring a finer pattern is called immersion exposure, and is an essential technique for lithography miniaturization, particularly lithography of several tens of nanometers. The projection exposure apparatus is also known (see Patent Document 1).
In the immersion exposure method, a photoresist film applied and formed on a wafer and a lens of a projection exposure apparatus are in contact with a medium having a refractive index n. For example, when water is used as a medium, water may permeate the photoresist film and the resolution of the photoresist may be reduced. In addition, the lens of the projection exposure apparatus may contaminate the lens surface due to elution of components constituting the photoresist into water.

For this reason, there is a method of forming an upper layer film on the photoresist film for the purpose of blocking the photoresist film from a medium such as water, but this upper layer film has sufficient transparency with respect to the wavelength of radiation and the photoresist. A protective film can be formed on the photoresist film without causing intermixing with the film, and a stable coating can be maintained without leaching into the medium during immersion exposure, thereby increasing the contact angle that can reduce resistance to lens movement. In addition, it is necessary to form an upper layer film that easily dissolves in an alkaline solution that is a developer. The contact angle of the upper layer film with respect to the immersion medium is desired to be 70 ° or more.
In addition, it is required that a resist designed on the assumption of use in a normal dry environment can be used as an immersion resist as it is. For this purpose, there is a need for an upper film for immersion that can protect the resist film from the immersion liquid without deteriorating the original performance designed for normal dry use, not for immersion.
Japanese Patent Laid-Open No. 11-176727

  The present invention has been made to overcome such problems, and has sufficient transparency at an exposure wavelength, particularly 193 nm (ArF), and forms a coating on the photoresist without causing intermixing with the photoresist film. It can be formed, maintains a stable coating without leaching into the medium during immersion exposure, has a large contact angle with the immersion medium of 70 ° or more, and further deteriorates the shape of the pattern after dry exposure without immersion exposure. An object of the present invention is to provide an upper layer resin composition for forming an upper layer film that is easily dissolved in an alkali developer and a copolymer used in the composition.

（式（３）において、Ｒはメチル基を、Ｒ'およびＲ''は水素原子を表し、Ｒ ⁵ は２価の鎖状炭化水素基を表す。） The copolymer for immersion upper layer film of the present invention is a copolymer for forming an upper layer film to be coated with a photoresist film subjected to immersion exposure, and the copolymer is a repeating unit having a carboxyl group. Containing 20 to 60 mol% of all repeating units, including repeating units derived from a hydroxyl group-containing (meth) acrylic acid alkyl ester , wherein the hydroxyl group-containing (meth) acrylic acid alkyl ester is represented by the formula (3), gel The weight average molecular weight measured by a permeation chromatography method is 2,000 to 100,000.

(In Formula (3), R represents a methyl group, R ′ and R ″ represent a hydrogen atom, and R ⁵ represents a divalent chain hydrocarbon group.)

  The resin composition for an immersion upper layer film of the present invention is a resin composition for forming an upper layer film coated with a photoresist film subjected to immersion exposure, and the composition is a resin that dissolves in a developer. Is dissolved in a solvent containing a monohydric alcohol, and the resin is the copolymer of the present invention.

Since the copolymer of this invention contains the repeating unit which has a carboxyl group, the solubility with respect to an alkali developing solution improves.
In addition, since (meth) acrylic acid ester having a fluorine atom-containing group in its side chain is included as a repeating unit, the refractive index of the upper layer film and the contact angle with respect to the immersion medium can be adjusted by adjusting the type and blending amount. Can be controlled.
Furthermore, since the hydroxyl group-containing (meth) acrylic acid alkyl ester is contained as a repeating unit, the solubility in the alcohol used as a solvent of the resin composition for a liquid immersion upper layer film is improved.
Therefore, it can be used very suitably for the manufacture of semiconductor devices that are expected to be further miniaturized in the future.

The resin constituting the upper layer film-forming composition of the present invention can form a stable film on a medium such as water upon irradiation with radiation during immersion exposure, and is dissolved in a developer for forming a resist pattern. Resin.
Here, a film that is stable to a medium such as water at the time of radiation irradiation means that, for example, the change in film thickness measured by the method for evaluating stability to water described later is within 0.5% of the initial film thickness. Say. Further, “dissolving in a developer after formation of a resist pattern” means that there is no residue on the resist pattern after development using an alkaline aqueous solution and the upper layer film is removed. That is, the resin according to the present invention is an alkali-soluble resin that hardly dissolves in a medium such as water and dissolves in the alkaline aqueous solution during development using the alkaline aqueous solution after irradiation.
The upper layer film made of such an alkali-soluble resin prevents direct contact between the photoresist film and a medium such as water during immersion exposure, and does not deteriorate the lithography performance of the photoresist film due to the penetration of the medium. In addition, the lens of the projection exposure apparatus is prevented from being contaminated by components eluted from the photoresist film.

式（１）で表される単量体において、Ｒ、Ｒ'およびＲ''は、それぞれ独立に、水素原子、メチル基、ヒドロキシメチル基、トリフルオロメチル基、またはフェニル基を表す。 Ａは、単結合、カルボニル基、カルボニルオキシ基、オキシカルボニル基を表し、Ｂは、単結合、炭素数１〜２０の２価の有機基を示す。炭素数１〜２０の２価の有機基としては、メチレン基、エチレン基、１，３−プロピレン基もしくは１，２−プロピレン基などのプロピレン基、テトラメチレン基、ペンタメチレン基、ヘキサメチレン基、ヘプタメチレン基、オクタメチレン基、ノナメチレン基、デカメチレン基、ウンデカメチレン基、ドデカメチレン基、トリデカメチレン基、テトラデカメチレン基、ペンタデカメチレン基、ヘキサデカメチレン基、ヘプタデカメチレン基、オクタデカメチレン基、ノナデカメチレン基、インサレン基、１−メチル−１，３−プロピレン基、２−メチル−１，３−プロピレン基、２−メチル−１，２−プロピレン基、１−メチル−１，４−ブチレン基、２−メチル−１，４−ブチレン基、メチリデン基、エチリデン基、プロピリデン基、または、２−プロピリデン基等の飽和鎖状炭化水素基；フェニレン基、トリレン基等のアリレン基；１，３−シクロブチレン基などのシクロブチレン基、１，３−シクロペンチレン基などのシクロペンチレン基、１，４−シクロヘキシレン基などのシクロヘキシレン基、１，５−シクロオクチレン基などのシクロオクチレン基等の炭素数３〜１０のシクロアルキレン基などの単環式炭化水素環基；１，４−ノルボルニレン基もしくは２，５−ノルボルニレン基などのノルボルニレン基、１，５−アダマンチレン基、２，６−アダマンチレン基などのアダマンチレン基等の２〜４環式炭素数４〜２０の炭化水素環基などの架橋環式炭化水素環基；ポリエチレングリコール、ポリプロピレングリコールなどの炭素数１〜１０のポリアルキレングリコールより誘導される２価の基等が挙げられる。 The repeating unit having a carboxyl group constituting the copolymer of the present invention can be obtained by polymerizing a monomer represented by the following formula (1).

In the monomer represented by the formula (1), R, R ′ and R ″ each independently represents a hydrogen atom, a methyl group, a hydroxymethyl group, a trifluoromethyl group, or a phenyl group. A represents a single bond, a carbonyl group, a carbonyloxy group, or an oxycarbonyl group, and B represents a single bond or a divalent organic group having 1 to 20 carbon atoms. Examples of the divalent organic group having 1 to 20 carbon atoms include a methylene group, an ethylene group, a 1,3-propylene group or a 1,2-propylene group such as a propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, Heptamethylene group, octamethylene group, nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group, tridecamethylene group, tetradecamethylene group, pentadecamethylene group, hexadecamethylene group, heptacamethylene group, octadecamethan group Methylene group, nonadecamethylene group, insalene group, 1-methyl-1,3-propylene group, 2-methyl-1,3-propylene group, 2-methyl-1,2-propylene group, 1-methyl-1, 4-butylene group, 2-methyl-1,4-butylene group, methylidene group, ethylidene group, propylidene group, Is a saturated chain hydrocarbon group such as a 2-propylidene group; an arylene group such as a phenylene group or a tolylene group; a cyclobutylene group such as a 1,3-cyclobutylene group or a cyclopentylene group such as a 1,3-cyclopentylene group. Monocyclic hydrocarbon ring groups such as cycloalkylene groups having 3 to 10 carbon atoms such as ylene groups, cyclohexylene groups such as 1,4-cyclohexylene groups, and cyclooctylene groups such as 1,5-cyclooctylene groups 2 to 4 cyclic carbon atoms such as norbornylene group such as 1,4-norbornylene group or 2,5-norbornylene group, adamantylene group such as 1,5-adamantylene group and 2,6-adamantylene group, etc. Bridged cyclic hydrocarbon ring groups such as 20 hydrocarbon ring groups; polyalkylene glycols having 1 to 10 carbon atoms such as polyethylene glycol and polypropylene glycol Divalent group derived from Le and the like.

式（１−１）〜式（１−３）において、Ｒ、Ｒ'およびＲ''は式（１）のＲ、Ｒ'およびＲ''と同一であり、Ｒ¹は、メチレン基、エチレン基などの炭素数１〜２０のアルキレン基、１，４−ノルボルニレン基もしくは２，５−ノルボルニレン基などのノルボルニレン基、１，５−アダマンチレン基、２，６−アダマンチレン基などのアダマンチレン基等の架橋環式炭化水素環基、ポリエチレングリコール、ポリプロピレングリコールなどの炭素数２〜１０のポリアルキレングリコールより誘導される２価の基を表し、Ｒ²は、単結合、炭素数１〜２０のアルキレン基を表す。 In the monomer represented by the formula (1), preferable monomers are represented by the following formula (1-1), formula (1-2), and formula (1-3).

In the formulas (1-1) to (1-3), R, R ′ and R ″ are the same as R, R ′ and R ″ in the formula (1), and R ¹ is a methylene group, ethylene An alkylene group having 1 to 20 carbon atoms such as a group, a norbornylene group such as a 1,4-norbornylene group or a 2,5-norbornylene group, an adamantylene group such as a 1,5-adamantylene group and a 2,6-adamantylene group Represents a divalent group derived from a polyalkylene glycol having 2 to 10 carbon atoms such as a crosslinked cyclic hydrocarbon ring group such as polyethylene glycol and polypropylene glycol, and R ² is a single bond, having 1 to 20 carbon atoms. Represents an alkylene group.

As the monomer represented by the formula (1-1), (meth) acrylic acid, crotonic acid, cinnamic acid, atropic acid, 3-acetyloxy (meth) acrylic acid, 3-benzoyloxy (meth) acrylic Examples thereof include unsaturated monocarboxylic acids such as acid, α-methoxyacrylic acid, and 3-cyclohexyl (meth) acrylic acid. Among them, (meth) acrylic acid and crotonic acid are preferable.
Examples of the monomer represented by the formula (1-2) include 2-bicyclo [2.2.1] hept-5-enecarboxylic acid and bicyclo [2.2.1] hept-5-ene-2- Ylmethanecarboxylic acid, 4-tricyclo [5.2.1.0 ^2,6 ] dec-8-enecarboxylic acid, tricyclo [5.2.1.0 ^2,6 ] dec-8-en-4-yl And methanecarboxylic acid and the like. Among these, 2-bicyclo [2.2.1] hept-5-enecarboxylic acid, bicyclo [2.2.1] hept-5-en-2-ylmethanecarboxylic acid Is preferred.
As the monomer represented by the formula (1-3), 4-vinylbenzoic acid, 4-vinylphenylacetic acid, 4-vinyldihydrocinnamic acid, 4- (4-vinylphenyl) butyric acid, 5- (4- Vinylphenyl) valeric acid, 12- (4-vinylphenyl) lauric acid, 3- (4-vinylphenyl) isobutyric acid, 4- (4-vinylphenyl) isovaleric acid, 3- (4-vinylphenyl) pivalic acid 4-isopropenylbenzoic acid, 4-isopropenylphenylacetic acid, 4-isopropenyldihydrocinnamic acid, 4- (4-isopropenylphenyl) butyric acid, 5- (4-isopropenylphenyl) valeric acid, 4- (1 -Propenyl) benzoic acid, 4- (1-propenyl) phenylacetic acid, 4- (1-propenyl) dihydrocinnamic acid, 4- (4- (1-propenyl) phenyl) butyric acid, 5- (4- (1-propyl) (Lopenyl) phenyl) valeric acid, 2-vinylbenzoic acid, 2-vinylphenylacetic acid, 2-vinyldihydrocinnamic acid, 4- (2-vinylphenyl) butyric acid, 5- (2-vinylphenyl) valeric acid, 12- ( 2-vinylphenyl) lauric acid, 3- (2-vinylphenyl) isobutyric acid, 4- (2-vinylphenyl) isovaleric acid, 3- (2-vinylphenyl) pivalic acid, 2-isopropenylbenzoic acid, 2 -Isopropenylphenylacetic acid, 2-isopropenyldihydrocinnamic acid, 4- (2-isopropenylphenyl) butyric acid, 5- (2-isopropenylphenyl) valeric acid, 2- (1-propenyl) benzoic acid, 2- ( 1-propenyl) phenylacetic acid, 2- (1-propenyl) dihydrocinnamic acid, 4- (2- (1-propenyl) phenyl) butyric acid, 5- (2- (1-propenyl) Phenyl) valeric acid can be mentioned, among which 4-vinylbenzoic acid, 4-vinylphenylacetic acid, 4-vinyldihydrocinnamic acid and 4-isopropenylbenzoic acid are preferred.
Of the above, (meth) acrylic acid and crotonic acid are preferred.

In addition to the monomer represented by the above formula (1) as a monomer that generates a repeating unit having a carboxyl group, the solubility in an alkali developer does not become too high and does not cause intermixing with a resist. Within the range, other carboxyl group-containing monomers can be used, preferably within 50 mol% with respect to the total amount of carboxyl group-containing monomers.
Other carboxyl group-containing monomers include fumaric acid, maleic acid, citraconic acid, mesaconic acid, itaconic acid and other unsaturated polycarboxylic acids; 2- (meth) acrylamide-2-methylpropanecarboxylic acid, 2-α -Carboxyacrylamide-2-methylpropanecarboxylic acid, 2-α-carboxymethylacrylamide-2-methylpropanecarboxylic acid, 2-α-methoxycarbonylacrylamide-2-methylpropanecarboxylic acid, 2-α-acetyloxyacrylamide-2 -Methylpropanecarboxylic acid, 2-α-phenylacrylamide-2-methylpropanecarboxylic acid, 2-α-benzylacrylamide-2-methylpropanecarboxylic acid, 2-α-methoxyacrylamide-2-methylpropanecarboxylic acid, 2- α-Cyclohexylacrylic Examples thereof include amido-2-methylpropanecarboxylic acid and 2-α-cyanoacrylamide-2-methylpropanecarboxylic acid.

式（２）において、Ｒ、Ｒ'およびＲ''は式（１）のＲ、Ｒ'およびＲ''と同一であり、Ｒ³は、有機基を表し、好ましくは２価の炭化水素基を表す。２価の炭化水素基の中で好ましくは鎖状または環状の炭化水素基を表す。
好ましいＲ³としては、メチレン基、エチレン基、１，３−プロピレン基もしくは１，２−プロピレン基などのプロピレン基、テトラメチレン基、ペンタメチレン基、ヘキサメチレン基、ヘプタメチレン基、オクタメチレン基、ノナメチレン基、デカメチレン基、ウンデカメチレン基、ドデカメチレン基、トリデカメチレン基、テトラデカメチレン基、ペンタデカメチレン基、ヘキサデカメチレン基、ヘプタデカメチレン基、オクタデカメチレン基、ノナデカメチレン基、インサレン基、１−メチル−１，３−プロピレン基、２−メチル−１，３−プロピレン基、２−メチル−１，２−プロピレン基、１−メチル−１，４−ブチレン基、２−メチル−１，４−ブチレン基、メチリデン基、エチリデン基、プロピリデン基、または、２−プロピリデン基等の飽和鎖状炭化水素基；１，３−シクロブチレン基などのシクロブチレン基、１，３−シクロペンチレン基などのシクロペンチレン基、１，４−シクロヘキシレン基などのシクロヘキシレン基、１，５−シクロオクチレン基などのシクロオクチレン基等の炭素数３〜１０のシクロアルキレン基などの単環式炭化水素環基；１，４−ノルボルニレン基もしくは２，５−ノルボルニレン基などのノルボルニレン基、１，５−アダマンチレン基、２，６−アダマンチレン基などのアダマンチレン基等の２〜４環式炭素数４〜３０の炭化水素環基などの架橋環式炭化水素環基；２−（スルホニルアミノ）エチル基、３−（スルホニルアミノ）プロピル基、２−（スルホニルアミノ）プロピル基、４−（スルホニルアミノ）ブチル基、３−（スルホニルアミノ）ブチル基、２−（スルホニルアミノ）ブチル基、３−（スルホニルアミノ）２−メチルプロピル基、２−（スルホニルアミノ）−１，１−ジメチルエチル基、２−（スルホニルアミノ）−２−メチルプロピル基などのスルホニルアミノ基、フェニレン基等が挙げられる。 The (meth) acrylic acid ester having a fluorine atom-containing group that can be used in the present invention in its side chain can control the refractive index and contact angle of the upper layer film, and is represented by the following formula (2).

In the formula (2), R, R ′ and R ″ are the same as R, R ′ and R ″ in the formula (1), R ³ represents an organic group, preferably a divalent hydrocarbon group. Represents. Of the divalent hydrocarbon groups, a chain or cyclic hydrocarbon group is preferred.
Preferred R ³ is a methylene group, an ethylene group, a propylene group such as a 1,3-propylene group or a 1,2-propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, Nonamethylene group, Decamemethylene group, Undecamethylene group, Dodecamethylene group, Tridecamethylene group, Tetradecamethylene group, Pentacamethylene group, Hexadecamethylene group, Heptadecamethylene group, Octadecamethylene group, Nonadecamethylene group, Insalene group, 1-methyl-1,3-propylene group, 2-methyl-1,3-propylene group, 2-methyl-1,2-propylene group, 1-methyl-1,4-butylene group, 2-methyl -1,4-butylene group, methylidene group, ethylidene group, propylidene group, or 2-propylene Saturated chain hydrocarbon groups such as den groups; cyclobutylene groups such as 1,3-cyclobutylene groups; cyclopentylene groups such as 1,3-cyclopentylene groups; cyclohexylenes such as 1,4-cyclohexylene groups A monocyclic hydrocarbon ring group such as a cycloalkylene group having 3 to 10 carbon atoms such as a cyclooctylene group such as a 1,5-cyclooctylene group; a 1,4-norbornylene group or a 2,5-norbornylene group Such as norbornylene group, 1,5-adamantylene group, adamantylene group such as 2,6-adamantylene group, etc., bridged cyclic hydrocarbon ring such as 2-4 cyclic hydrocarbon ring group having 4-30 carbon atoms Groups: 2- (sulfonylamino) ethyl group, 3- (sulfonylamino) propyl group, 2- (sulfonylamino) propyl group, 4- (sulfonylamino) butyl group, (Sulfonylamino) butyl group, 2- (sulfonylamino) butyl group, 3- (sulfonylamino) 2-methylpropyl group, 2- (sulfonylamino) -1,1-dimethylethyl group, 2- (sulfonylamino) -2- Examples include a sulfonylamino group such as a methylpropyl group, a phenylene group, and the like.

In Formula (2), R ⁴ includes a C 1-20 fluoroalkyl group.
Examples of the fluoroalkyl group having 1 to 20 carbon atoms include difluoromethyl group, perfluoromethyl group, 2,2-difluoroethyl group, 2,2,2-trifluoroethyl group, perfluoroethyl group, 2,2,3 , 3-tetrafluoropropyl group, perfluoroethylmethyl group, perfluoropropyl group, 2,2,3,3,4,4-hexafluorobutyl group, perfluorobutyl group, 1,1-dimethyl-2,2 , 3,3-tetrafluoropropyl group, 1,1-dimethyl-2,2,3,3,3-pentafluoropropyl group, 2- (perfluoropropyl) ethyl group, 2,2,3,3,4 , 4,5,5-octafluoropentyl group, perfluoropentyl group, 1,1-dimethyl-2,2,3,3,4,4-hexafluorobutyl group, 1,1-dimethyl-2, , 3,3,4,4,4-heptafluorobutyl group, 2- (perfluorobutyl) ethyl group, 2,2,3,3,4,4,5,5,6,6-decafluorohexyl group Perfluoropentylmethyl group, perfluorohexyl group, 1,1-dimethyl-2,2,3,3,4,4,5,5-octafluoropentyl group, 1,1-dimethyl-2,2,3 , 3,4,4,5,5,5-nonafluoropentyl group, 2- (perfluoropentyl) ethyl group, 2,2,3,3,4,4,5,5,6,6,7, 7-dodecafluoroheptyl group, perfluorohexylmethyl group, perfluoroheptyl group, 2- (perfluorohexyl) ethyl group, 2,2,3,3,4,4,5,5,6,6,7, 7,8,8-tetradecafluorooctyl group, perfluoroheptyl Til group, perfluorooctyl group, 2- (perfluoroheptyl) ethyl group, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9- Hexadecafluorononyl group, perfluorooctylmethyl group, perfluorononyl group, 2- (perfluorooctyl) ethyl group, 2,2,3,3,4,4,5,5,6,6,7,7 , 8,8,9,9,10,10-octadecafluorodecyl group, perfluorononylmethyl group, perfluorodecyl group, 2,2,3,4,4,4-hexafluorobutyl group, 2,2 3,3,4,4,4-heptafluorobutyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, 3,3,4,4,5,5 , 6,6,7,7,8,8,8-tridodecafluorooctyl group. .

  Examples of the (meth) acrylic acid ester having a group containing a fluorine atom in its side chain include difluoromethyl (meth) acrylate, perfluoromethyl (meth) acrylate, 2,2-difluoroethyl (meth) acrylate, 2,2 , 2-trifluoroethyl (meth) acrylate, perfluoroethyl (meth) acrylate, 1- (perfluoromethyl) ethyl (meth) acrylate, 2- (perfluoromethyl) ethyl (meth) acrylate, 2,2,3 , 3-tetrafluoropropyl (meth) acrylate, perfluoroethylmethyl (meth) acrylate, di (perfluoromethyl) methyl (meth) acrylate, perfluoropropyl (meth) acrylate, 1-methyl-2,2,3 3-tetrafluoropropyl (meth) acryl 1- (perfluoroethyl) ethyl (meth) acrylate, 2- (perfluoroethyl) ethyl (meth) acrylate, 2,2,3,3,4,4-hexafluorobutyl (meth) acrylate, Fluoropropylmethyl (meth) acrylate, perfluorobutyl (meth) acrylate, 1,1-dimethyl-2,2,3,3-tetrafluoropropyl (meth) acrylate, 1,1-dimethyl-2,2,3 3,3-pentafluoropropyl (meth) acrylate, 2- (perfluoropropyl) ethyl (meth) acrylate, 2,2,3,3,4,4,5,5-octafluoropentyl (meth) acrylate, per Fluorobutylmethyl (meth) acrylate, perfluoropentyl (meth) acrylate, 1,1-dimethyl 2,2,3,3,4,4-hexafluorobutyl (meth) acrylate, 1,1-dimethyl-2,2,3,3,4,4,4-heptafluorobutyl (meth) acrylate, 2- (Perfluorobutyl) ethyl (meth) acrylate, 2,2,3,3,4,4,5,5,6,6-decafluorohexyl (meth) acrylate, perfluoropentylmethyl (meth) acrylate, perfluoro Hexyl (meth) acrylate, 1,1-dimethyl-2,2,3,3,4,4,5,5-octafluoropentyl (meth) acrylate, 1,1-dimethyl-2,2,3,3 4,4,5,5,5-nonafluoropentyl (meth) acrylate, 2- (perfluoropentyl) ethyl (meth) acrylate, 2,2,3,3,4,4,5,5,6,6 , 7,7-dodecafluoroheptyl (meth) acrylate, perfluorohexylmethyl (meth) acrylate, perfluoroheptyl (meth) acrylate, 2- (perfluorohexyl) ethyl (meth) acrylate, 2,2,3,3 4,4,5,5,6,6,7,7,8,8-tetradecafluorooctyl (meth) acrylate, perfluoroheptylmethyl (meth) acrylate, perfluorooctyl (meth) acrylate, 2- (per Fluoroheptyl) ethyl (meth) acrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononyl (meth) acrylate, Perfluorooctylmethyl (meth) acrylate, perfluorononyl (meth) acrylate, 2- (perfluoroo Til) ethyl (meth) acrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-octadecafluorodecyl (meth) ) Acrylate, perfluorononylmethyl (meth) acrylate, perfluorodecyl (meth) acrylate, 2,2,3,4,4,4-hexafluorobutyl (meth) acrylate, 2,2,3,3,4 4,4-heptafluorobutyl (meth) acrylate, 3,3,4,4,5,5,6,6,6-nonafluorohexyl (meth) acrylate, 3,3,4,4,5,5 Fluoroalkyl (meth) acrylates having 1 to 20 carbon atoms in the fluoroalkyl group such as 6,6,7,7,8,8,8-tridecafluorooctyl (meth) acrylate,

(2,2,2-trifluoroethyl) α-carboxyacrylate, (perfluoroethylmethyl) α-carboxyacrylate, (2,2,2-trifluoroethyl) α-carboxymethylacrylate, (perfluoroethylmethyl) α-carboxymethyl acrylate, (2,2,2-trifluoroethyl) α-methoxycarbonyl acrylate, (perfluoroethylmethyl) α-methoxycarbonyl acrylate, (2,2,2-trifluoroethyl) α-acetyloxy Acrylate, (perfluoroethyl methyl) α-acetyloxy acrylate, (2,2,2-trifluoroethyl) α-phenyl acrylate, (perfluoroethyl methyl) α-phenyl acrylate, (2,2,2-trifluoro Ethyl) α-benzylacryl Rate, (perfluoroethyl methyl) α-benzyl acrylate, (2,2,2-trifluoroethyl) α-ethoxy acrylate, (perfluoroethyl methyl) α-ethoxy acrylate, (2,2,2-trifluoroethyl) ) Α-2-methoxyethyl acrylate, (perfluoroethylmethyl) α-2-methoxyethyl acrylate, (2,2,2-trifluoroethyl) α-cyclohexyl acrylate, (perfluoroethylmethyl) α-cyclohexyl acrylate, (2,2,2-trifluoroethyl) α-cyanoacrylate, (perfluoroethylmethyl) α-cyanoacrylate, 3 [4 [1-trifluoromethyl-2,2-bis [bis (trifluoromethyl) fluoro Methyl] ethynyloxy] benzooxy] 2-hydro Xylpropyl (meth) acrylate, (2,2,3,3,3-pentafluoropropyl) 2-phenyl acrylate, (2,2,3,3,3-pentafluoropropyl) 2-benzyl acrylate, (2,2 , 3,3,3-pentafluoropropyl) 2-ethoxyacrylate, (2,2,3,3,3-pentafluoropropyl) 2-cyclohexyl acrylate, (2,2,3,3,3-pentafluoropropyl) ) 2-cyanoacrylate, 2-(((trifluoromethyl) sulfonyl) amino) ethyl-1-methacrylate, 2-(((trifluoromethyl) sulfonyl) amino) ethyl-1-acrylate, and the like. These fluoroalkyl group-containing monomers can be used alone or in admixture of two or more.
In the present invention, as the fluoroalkyl group-containing monomer, fluoroalkyl (meth) acrylates having 1 to 20 carbon atoms of the fluoroalkyl group are preferable, and among them, perfluoroalkyl (meth) acrylate and perfluoroalkyl group Particularly preferred are fluoroalkyl (meth) acrylates in which is bonded to the ester oxygen atom via a methylene group, an ethylene group or a sulfonylamino group.

Examples of the hydroxyl group-containing (meth) acrylic acid alkyl ester that can be used in the present invention include monomers in which a carboxyl group is substituted with a hydroxyl group in formulas (1-1) and (1-2).
Examples of the hydroxyl group-containing (meth) acrylic acid alkyl ester include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2, 3-dihydroxypropyl (meth) acrylate, polypropylene glycol (meth) acrylate, 2-hydroxycyclohexyl (meth) acrylate, 4-hydroxycyclohexyl (meth) acrylate, 3-hydroxy-1-adamantyl (meth) acrylate, 3,5- Examples include dihydroxy-1-adamantyl (meth) acrylate, among which 2-hydroxyethyl (meth) acrylate and 3-hydroxy-1-adamantyl (meth) acrylate are preferred. .
These monomers can be used alone or in combination of two or more.

式（３）において、Ｒ、Ｒ'およびＲ''は式（１）のＲ、Ｒ'およびＲ''と同一であり、Ｒ⁵は有機基を表し、好ましくは２価の炭化水素基を表す。２価の炭化水素基の中で好ましくは鎖状または環状の炭化水素基を表す。
好ましいＲ⁵としては、メチレン基、エチレン基、１，３−プロピレン基もしくは１，２−プロピレン基などのプロピレン基、テトラメチレン基、ペンタメチレン基、ヘキサメチレン基、ヘプタメチレン基、オクタメチレン基、ノナメチレン基、デカメチレン基、ウンデカメチレン基、ドデカメチレン基、トリデカメチレン基、テトラデカメチレン基、ペンタデカメチレン基、ヘキサデカメチレン基、ヘプタデカメチレン基、オクタデカメチレン基、ノナデカメチレン基、インサレン基、１−メチル−１，３−プロピレン基、２−メチル−１，３−プロピレン基、２−メチル−１，２−プロピレン基、１−メチル−１，４−ブチレン基、２−メチル−１，４−ブチレン基、メチリデン基、エチリデン基、プロピリデン基、または、２−プロピリデン基等の飽和鎖状炭化水素基、１，３−シクロブチレン基などのシクロブチレン基、１，３−シクロペンチレン基などのシクロペンチレン基、１，４−シクロヘキシレン基などのシクロヘキシレン基、１，５−シクロオクチレン基などのシクロオクチレン基等の炭素数３〜１０のシクロアルキレン基などの単環式炭化水素環基、１，４−ノルボルニレン基もしくは２，５−ノルボルニレン基などのノルボルニレン基、１，５−アダマンチレン基、２，６−アダマンチレン基などのアダマンチレン基等の２〜４環式炭素数４〜３０の炭化水素環基などの架橋環式炭化水素環基等が挙げられる。 Further, a (meth) acrylic acid derivative containing a fluoroalkyl group and a hydroxyl group represented by the following formula (3) can be used.

In the formula (3), R, R ′ and R ″ are the same as R, R ′ and R ″ in the formula (1), R ⁵ represents an organic group, preferably a divalent hydrocarbon group. To express. Of the divalent hydrocarbon groups, a chain or cyclic hydrocarbon group is preferred.
Preferred R ⁵ is a methylene group, an ethylene group, a propylene group such as a 1,3-propylene group or a 1,2-propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, Nonamethylene group, Decamemethylene group, Undecamethylene group, Dodecamethylene group, Tridecamethylene group, Tetradecamethylene group, Pentacamethylene group, Hexadecamethylene group, Heptadecamethylene group, Octadecamethylene group, Nonadecamethylene group, Insalene group, 1-methyl-1,3-propylene group, 2-methyl-1,3-propylene group, 2-methyl-1,2-propylene group, 1-methyl-1,4-butylene group, 2-methyl -1,4-butylene group, methylidene group, ethylidene group, propylidene group, or 2-propylene Saturated chain hydrocarbon groups such as den groups, cyclobutylene groups such as 1,3-cyclobutylene groups, cyclopentylene groups such as 1,3-cyclopentylene groups, and cyclohexylene groups such as 1,4-cyclohexylene groups Group, monocyclic hydrocarbon ring group such as cycloalkylene group having 3 to 10 carbon atoms such as cyclooctylene group such as 1,5-cyclooctylene group, 1,4-norbornylene group or 2,5-norbornylene group Such as norbornylene group, 1,5-adamantylene group, adamantylene group such as 2,6-adamantylene group, etc., bridged cyclic hydrocarbon ring such as 2-4 cyclic hydrocarbon ring group having 4-30 carbon atoms Groups and the like.

In particular, when R ⁵ contains a divalent aliphatic cyclic hydrocarbon group, an alkylene group having 1 to 4 carbon atoms is used as a spacer between the bistrifluoromethyl-hydroxy-methyl group and the aliphatic cyclic hydrocarbon group. It is preferable to insert.
In the formula (3), R ⁵ is preferably a 2,5-norbornylene group, a hydrocarbon group containing a 2,6-norbornylene group, or a 1,2-propylene group.

The copolymer of the present invention can be copolymerized with other radical polymerizable monomers for the purpose of controlling the molecular weight, glass transition point, etc. of the copolymer. “Other” means a radical polymerizable monomer other than the above-mentioned radical polymerizable monomers. Moreover, an acid dissociable group-containing monomer can be copolymerized.
Other radical polymerizable monomers or acid dissociable group-containing monomers include (meth) acrylic acid alkyl esters, (meth) acrylic acid aryl esters, dicarboxylic acid diesters, nitrile group-containing radical polymerizable monomers. Mer, amide bond-containing radical polymerizable monomer, fatty acid vinyls, chlorine-containing radical polymerizable monomer, conjugated diolefin, hydroxyl group-containing (meth) acrylic acid alicyclic alkyl ester, (meth) acrylic acid alicyclic Group alkyl ester and the like. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, isopropyl (meth) acrylate, n-hexyl (Meth) acrylate, cyclohexyl (meth) acrylate, 2-methylcyclohexyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, methoxydipropylene glycol (Meth) acrylate, butoxy-dipropylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, 2-methyl 2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, 2-propyl-2-adamantyl (meth) acrylate, 2-butyl-2-adamantyl (meth) acrylate, 1-methyl-1- Cyclohexyl (meth) acrylate, 1-ethyl-1-cyclohexyl (meth) acrylate, 1-propyl-1-cyclohexyl (meth) acrylate, 1-butyl-1-cyclohexyl (meth) acrylate, 1-methyl-1-cyclopentyl ( (Meth) acrylate, 1-ethyl-1-cyclopentyl (meth) acrylate, 1-propyl-1-cyclopentyl (meth) acrylate, 1-butyl-1-cyclopentyl (meth) acrylate, 1-adamantyl-1-methylethyl (meth) Acrylate (Meth) acrylic acid alkyl esters such as 1-bicyclo [2.2.1] heptyl-1-methylethyl (meth) acrylate; dicarboxylic acid diesters such as diethyl maleate, diethyl fumarate and diethyl itaconate; phenyl (meta ) (Meth) acrylic acid aryl esters such as acrylate and benzyl (meth) acrylate; aromatic vinyls such as styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, p-methoxystyrene, Nitrile group-containing radical polymerizable monomers such as acrylonitrile and methacrylonitrile; Amide bond-containing radical polymerizable monomers such as acrylamide, methacrylamide and trifluoromethanesulfonylaminoethyl (meth) acrylate; Fatty acid vinyl such as vinyl acetate Le ethers; vinyl chloride, chlorine-containing radical polymerizable monomers such as vinylidene chloride; 1,3-butadiene, isoprene, may be used conjugated diolefins such as 1,4-dimethyl butadiene.
These monomers can be used alone or in combination of two or more.

The copolymer of the present invention contains a repeating unit having a carboxyl group as an essential component, and the content thereof is 20 to 60 mol% of all repeating units constituting the copolymer containing the repeating unit having a carboxyl group. is there. If it exceeds 60 mol%, the solubility in an alkali developer may become too high, and if it is less than 20 mol%, the solubility in an alkali developer may be too low and development may not be possible.
In the copolymer of the present invention, it is preferable that a repeating unit derived from a hydroxyl group-containing (meth) acrylic acid alkyl ester is used in combination with a repeating unit having a carboxyl group as a copolymer for a liquid immersion upper layer film.
The repeating unit derived from the hydroxyl group-containing (meth) acrylic acid alkyl ester is 0 to 70 mol% of all repeating units constituting the copolymer. This is because if it exceeds 70 mol%, the solubility in an aqueous alkali solution may become too high.
The repeating unit derived from the (meth) acrylic acid ester having a group containing a fluorine atom in its side chain is 5 to 50 mol% of all repeating units constituting the copolymer. If it exceeds 50 mol%, the alkali solubility of the resin becomes too low, and the solubility in a solvent becomes low, making it difficult to prepare a resin solution. This is because the effect of controlling is lost.
Moreover, the repeating unit derived from the (meth) acrylic acid derivative containing a fluoroalkyl group and a hydroxyl group is 5 to 70 mol% of all repeating units constituting the copolymer. If the amount exceeds 70 mol%, the solubility of the alkaline aqueous solution may be too high, and if it is less than 5 mol%, the effect of controlling the refractive index and the contact angle will be lost.
In addition, the repeating unit other than the above is 0 mol% to 90 mol%, preferably 0 mol% to 80 mol%. If it exceeds 90 mol%, the solubility in an alkaline aqueous solution as a developer is lowered, and the upper layer film cannot be removed, and a residue may be generated on the resist pattern after development.

For example, the copolymer of the present invention is obtained by polymerizing a mixture of monomers that form each repeating unit in a suitable solvent using a radical polymerization initiator and optionally in the presence of a chain transfer agent. Can be manufactured.
Examples of the solvent that can be used for the polymerization include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, ethylene glycol, diethylene glycol, and propylene glycol; cyclic ethers such as tetrahydrofuran and dioxane. Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, propylene glycol monomethyl ether, propylene glycol Alkyl ethers of polyhydric alcohols such as rumonoethyl ether; alkyl ether acetates of polyhydric alcohols such as ethylene glycol ethyl ether acetate, diethylene glycol ethyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate; toluene, xylene, etc. Aromatic hydrocarbons of: ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol; ethyl acetate, butyl acetate, ethyl 2-hydroxypropionate, Methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, Esters such as ethyl loxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, ethyl acetate, butyl acetate Kind. Of these, cyclic ethers, alkyl ethers of polyhydric alcohols, alkyl ether acetates of polyhydric alcohols, ketones, and esters are preferable.

Moreover, as a polymerization catalyst in radical copolymerization, a normal radical polymerization initiator can be used, for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis- (methyl 2-methylpropionate), Azo compounds such as 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobis- (4-methoxy-2-dimethylvaleronitrile); benzoyl peroxide, lauroyl peroxide, tert-butylperoxy Examples include pivalate, organic peroxides such as 1,1′-bis- (tert-butylperoxy) cyclohexane, hydrogen peroxide, and the like. When a peroxide is used as a radical polymerization initiator, a redox initiator may be combined with a reducing agent.
Moreover, the reaction temperature in the said superposition | polymerization is 40-120 degreeC normally, Preferably it is 50-100 degreeC, and reaction time is 1-48 hours normally, Preferably it is 1-24 hours.

The weight average molecular weight (hereinafter abbreviated as Mw) of the copolymer obtained by the above polymerization is usually 2,000 to 100,000, preferably 2,500 to 50,000, in terms of polystyrene by gel permeation chromatography. More preferably, it is 3,000 to 20,000. In this case, if the copolymer Mw is less than 2,000, the solvent resistance and mechanical properties such as water resistance as the upper layer film are remarkably low. On the other hand, if it exceeds 100,000, the solubility in the solvent described later is remarkably high. bad. The ratio (Mw / Mn) of the copolymer Mw to the polystyrene-equivalent number average molecular weight (hereinafter abbreviated as Mn) by gel permeation chromatography (GPC) is usually 1 to 5, preferably 1 to 3. It is.
In addition, it is preferable that the copolymer has less impurities such as halogen and metal, whereby the coating property as an upper layer film and the uniform solubility in an alkali developer can be further improved. Examples of the copolymer purification method include chemical purification methods such as washing with water and liquid-liquid extraction, and combinations of these chemical purification methods with physical purification methods such as ultrafiltration and centrifugation. Can do. The copolymer of the present invention can be used as a resin component of the upper layer film-forming composition, and the copolymers can be used alone or in admixture of two or more.

The solvent constituting the composition for forming an upper layer film of the present invention dissolves the above copolymer and deteriorates lithography performance by causing intermixing with the photoresist film when applied on the photoresist film. Solvents that do not occur can be used.
Examples of such a solvent include a solvent containing a monohydric alcohol. For example, methanol, ethanol, 1-propanol, isopropanol, n-propanol, n-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, n-hexanol, cyclohexanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2- Methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pen Tanol, 2,2-dimethyl-3-pentanol, 2,3-dimethyl-3-pentanol, 2,4-di Tyl-3-pentanol, 4,4-dimethyl-2-pentanol, 3-ethyl-3-pentanol, 1-heptanol, 2-heptanol, 3-heptanol, 2-methyl-2-hexanol, 2-methyl -3-hexanol, 5-methyl-1-hexanol, 5-methyl-2-hexanol, 2-ethyl-1-hexanol, 4-methyl-3-heptanol, 6-methyl-2-heptanol, 1-octanol, 2 -Octanol, 3-octanol, 2-propyl-1-pentanol, 2,4,4-trimethyl-1-pentanol, 2,6-dimethyl-4-heptanol, 3-ethyl-2,2-dimethyl-pen Tanol, 1-nonanol, 2-nonanol, 3,5,5-trimethyl-1-hexanol, 1-decanol, 2-decano , 4-decanol, 3,7-dimethyl-1-octanol, 3,7-dimethyl-3-octanol and the like.
Of these monohydric alcohols, monohydric alcohols having 4 to 8 carbon atoms are preferred, and n-butanol and 4-methyl-2-pentanol are more preferred.

In addition, when the upper layer film is applied on the photoresist film, another solvent can be mixed for the purpose of adjusting the coating property. Other solvents have the effect of uniformly coating the upper layer film without eroding the photoresist film.
Other solvents include polyhydric alcohols such as ethylene glycol and propylene glycol; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether Alkyl ethers of polyhydric alcohols such as diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene glycol ethyl ether acetate, diethylene glycol ethyl Alkyl ether acetates of polyhydric alcohols such as ether acetate, propylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate; aromatic hydrocarbons such as toluene and xylene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy- Ketones such as 4-methyl-2-pentanone and diacetone alcohol; ethyl acetate, butyl acetate, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate , Ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, Kishipuropion acid ethyl esters such as methyl 3-ethoxypropionate, and water. Among these, cyclic ethers, polyhydric alcohol alkyl ethers, polyhydric alcohol alkyl ether acetates, ketones, esters, and water are preferable.

  The blending ratio of the other solvent is 30% by weight or less, preferably 20% by weight or less in the solvent component. If it exceeds 30% by weight, the photoresist film is eroded, causing problems such as intermixing with the upper layer film, and the resolution performance of the photoresist is significantly deteriorated.

In the upper layer film-forming composition of the present invention, a surfactant can be blended for the purpose of improving the coating property, defoaming property, leveling property and the like.
Surfactants include, for example, BM-1000, BM-1100 (above, manufactured by BM Chemie), MegaFuck F142D, F172, F173, F183 (above, manufactured by Dainippon Ink and Chemicals), Florard FC-135, FC-170C, FC-430, FC-431 (above, manufactured by Sumitomo 3M), Surflon S-112, S-113, S-131, S-141, Commercially available under trade names such as S-145 (above, manufactured by Asahi Glass Co., Ltd.), SH-28PA, i-190, i-193, SZ-6032, SF-8428 (above, made by Toray Dow Corning Silicone Co., Ltd.) Fluorosurfactant that has been used can be used.
The blending amount of these surfactants is preferably 5 parts by weight or less with respect to 100 parts by weight of the alkali-soluble resin.

The upper layer film-forming composition of the present invention is coated on a photoresist film for forming a pattern by irradiation with radiation. In particular, it can be used as an upper film forming composition for immersion. An example in the case of using as an upper film forming composition for immersion is described below.
In the step of forming a photoresist film by applying a photoresist on the substrate, for example, a silicon wafer, a wafer coated with aluminum, or the like can be used as the substrate. In order to maximize the potential of the resist film, an organic or inorganic antireflection film is formed on the substrate to be used, as disclosed in, for example, Japanese Patent Publication No. 6-12452. I can leave.
The photoresist used is not particularly limited, and can be selected in a timely manner according to the purpose of use of the resist. Examples of the resist include a chemically amplified positive type or negative type resist containing an acid generator.
When using the upper layer film of the present invention, a positive resist is particularly preferable. In a chemically amplified positive resist, an acid-dissociable organic group in the polymer is dissociated by the action of an acid generated from an acid generator by exposure to generate, for example, a carboxyl group. The solubility in an alkali developer is increased, and the exposed portion is dissolved and removed by the alkali developer to obtain a positive resist pattern.
The photoresist film is prepared by dissolving a resin for forming a photoresist film in a suitable solvent at a solid content concentration of, for example, 0.1 to 20% by weight, and then filtering the solution by, for example, a filter having a pore diameter of about 30 nm. The resist solution is prepared by applying it onto a substrate by an appropriate application method such as spin coating, cast coating, roll coating, etc., and pre-baking (hereinafter referred to as “PB”) to volatilize the solvent. To do. In this case, a commercially available resist solution can be used as it is.

The step of forming the upper layer film on the photoresist film using the upper layer film-forming composition is performed by applying the upper layer film-forming composition of the present invention on the photoresist film and usually baking again, thereby This is a step of forming an upper layer film. This step is a step of forming an upper layer film for the purpose of protecting the photoresist film and preventing contamination of the lens of the projection exposure apparatus caused by elution of components contained in the resist from the photoresist film to the liquid. is there.
As the thickness of the upper layer film is closer to an odd multiple of λ / 4m (λ is the wavelength of radiation and m is the refractive index of the upper layer film), the reflection suppressing effect at the upper interface of the resist film is increased. For this reason, it is preferable that the thickness of the upper layer film be close to this value. In the present invention, any of the pre-baking after applying the resist solution and the baking after applying the upper layer film-forming composition solution may be omitted for simplification of the process.

The step of forming a resist pattern by irradiating the photoresist film and the upper layer film, for example, with water as a medium through a mask having a predetermined pattern, and then developing, performs immersion exposure, and performs predetermined exposure. This is a step of developing after baking at a temperature.
The pH of water filled between the photoresist film and the upper film can be adjusted. In particular, pure water is preferred.
The radiation used for immersion exposure depends on the photoresist film used and the combination of the photoresist film and the upper layer film for immersion, for example, visible rays; ultraviolet rays such as g rays and i rays; Various types of radiation such as ultraviolet rays; X-rays such as synchrotron radiation; and charged particle beams such as electron beams can be selectively used. In particular, an ArF excimer laser (wavelength 193 nm) or a KrF excimer laser (wavelength 248 nm) is preferable.
In order to improve the resolution, pattern shape, developability, etc. of the resist film, it is preferable to perform baking (hereinafter referred to as “PEB”) after exposure. The baking temperature is appropriately adjusted depending on the resist used and the like, but is usually about 30 to 200 ° C., preferably 50 to 150 ° C.
Then, the photoresist film is developed with a developer and washed to form a desired resist pattern. In this case, the upper layer film of the present invention does not need to be subjected to a separate peeling step and is completely removed during development or washing after development. This is one of the important features of the present invention.

  Examples of the developer used for forming the resist pattern in the present invention include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, ammonia, ethylamine, n-propylamine, diethylamine, and di-n-. Propylamine, triethylamine, methyldiethylamine, dimethylethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, pyrrole, piperidine, choline, 1,8-diazabicyclo- [5.4.0] -7-undecene And an alkaline aqueous solution in which 1,5-diazabicyclo- [4.3.0] -5-nonane and the like are dissolved. In addition, an appropriate amount of a water-soluble organic solvent, for example, alcohols such as methanol and ethanol, and a surfactant can be added to these developers. In the case where development is performed using the alkaline aqueous solution, it is usually washed with water after development.

Examples 1 to 3 and Comparative Example 1
Each copolymer was synthesized by the method shown below at the ratio shown in Table 1. In addition, Mw and Mn of each copolymer are GPC columns (trade name “G2000H _XL ” manufactured by Tosoh Corp.) in a high-speed GPC device (model “HLC-8120”) manufactured by Tosoh Corp .; _XL ”; one,“ G4000H _XL ”; one), gel permeation chromatography using monodisperse polystyrene as a standard under the analysis conditions of a flow rate of 1.0 ml / min, elution solvent tetrahydrofuran, and column temperature of 40 ° C. GPC). Further, the ratio of each repeating unit of the copolymer was measured by ¹³ C NMR.

上記単量体において、式（Ｍ−５）がカルボキシル基を有する繰返し単位を生成する単量体であり、式（Ｍ−６）および（Ｍ−９）が水酸基含有（メタ）アクリル酸アルキルエステルであり、式（Ｍ−３）（Ｍ−４）および（Ｍ−１０）がフッ素原子を含む基をその側鎖に有する（メタ）アクリル酸エステルであり、式（Ｍ−１）および（Ｍ−２）が水酸基とフッ素原子を含む基をその側鎖に有する（メタ）アクリル酸エステルであり、式（Ｍ−７）および（Ｍ−８）がその他の単量体である。 The monomers used for the synthesis of each copolymer are shown below as formulas (M-1) to (M-10).

In the above monomer, the formula (M-5) is a monomer that generates a repeating unit having a carboxyl group, and the formulas (M-6) and (M-9) are hydroxyl-containing (meth) acrylic acid alkyl esters. And the formulas (M-3), (M-4) and (M-10) are (meth) acrylic acid esters having a group containing a fluorine atom in the side chain, and the formulas (M-1) and (M -2) is a (meth) acrylic acid ester having a group containing a hydroxyl group and a fluorine atom in its side chain, and formulas (M-7) and (M-8) are other monomers.

A monomer solution prepared by dissolving a monomer and an initiator (methyl 2,2′-azobis- (2-methylpropionate)) in 200 g of isopropanol in a weight to be charged mol% shown in Table 1 was prepared. The total amount of monomers at the time of preparation was adjusted to 100 g. Further, the mol% of each monomer represents mol% with respect to the total amount of the monomer, and the mol% of initiator represents mol% with respect to the total amount of the monomer and the initiator.
100 g of isopropanol was added to a 1500 ml three-necked flask equipped with a thermometer and a dropping funnel, and purged with nitrogen for 30 minutes. The flask was heated to 80 ° C. while stirring with a magnetic stirrer. The monomer solution prepared earlier was added to the dropping funnel and dropped over 3 hours. After completion of the dropwise addition, the reaction was continued for another 3 hours and cooled to 30 ° C. or lower to obtain a copolymer solution.

The resulting copolymer was dropped into 3000 g of n-heptane stirring over 20 minutes, and stirring was further continued for 1 hour. The obtained slurry solution was filtered with a Buchner funnel, and the obtained white powder was added to 600 g of n-heptane and stirred to prepare a slurry solution, which was again filtered with a Buchner funnel. The obtained powder was dried for 24 hours in a vacuum dryer set at 50 ° C. Mw, Mw / Mn (dispersion degree of molecular weight), yield (% by weight) of the obtained copolymer, and the ratio of each repeating unit in the copolymer were measured. The results are shown in Table 2.

Example 4 to Example 6 and Comparative Example 2 to Comparative Example 3
An upper layer film-forming composition for immersion was prepared using the copolymer obtained in the above example. A solvent was added to 1 g of the solid content of the copolymer shown in Table 2 so as to have a ratio of 99 g of the solvent shown in Table 3, and the mixture was stirred for 2 hours, and then filtered through a filter having a pore size of 200 nm to prepare a solution. In Table 3, B represents normal butanol, and 4M2P represents 4-methyl-2-pentanol. In Table 3, the solvent ratio in the case of a mixed solvent represents a weight ratio.
The obtained upper layer film-forming composition was evaluated by the following method. The results are shown in Table 3. Comparative Example 3 is shown as a reference example, and is an example in which patterning evaluation was performed without using an upper layer film.
(1) Solubility evaluation method (solubility)
To 99 g of the solvent shown in Table 3, 1 g of the copolymer serving as the resin for the upper layer film was added and stirred at 100 rpm for 3 hours using a three-one motor. In addition, the copolymer obtained in Examples 1-12 used what dried and dried the copolymer solution at 100 degreeC for 24 hours. Then, if the mixture of the copolymer and the solvent is a uniform solution, it is judged that the solubility is good, and “○” is judged as poor solubility if undissolved or white turbidity is observed. did.

(2) Evaluation method of removability of upper layer film (removability)
The upper layer film was spin-coated on a 8-inch silicon wafer with CLEAN TRACK ACT8 (Tokyo Electron Co., Ltd.) and baked at 90 ° C. for 60 seconds to form a coating film having a thickness of 32 nm. The film thickness was measured using Lambda Ace VM90 (Dainippon Screen Co., Ltd.). This coating film was subjected to paddle development (developer 2.38% TMAH aqueous solution) for 60 seconds with CLEAN TRACK ACT8, spin-dried by shaking, and the wafer surface was observed. At this time, if there was no residue and it was developed, the removability was “◯”, and if the residue was observed, it was “x”.
(3) Intermixing evaluation method (intermixing)
JSR ArF AR1221J was spin-coated on an 8-inch silicon wafer that had been subjected to HMDS treatment (100 ° C., 60 seconds) in advance, and PB was performed on a hot plate at 90 ° C. for 60 seconds to form a coating film having a predetermined film thickness (300 nm). . Spin coat the above upper film composition for immersion on this coating film, form a coating film with a film thickness of 32 nm by PB (90 ° C., 60 seconds), and then clean the wafer with ultrapure water from a rinse nozzle of CLEAN TRACK ACT8. It was discharged for 60 seconds, spin-dried by shaking off at 4000 rpm for 15 seconds, and then paddle development was performed for 60 seconds with an LD nozzle using the CLEAN TRACK ACT8 to remove the upper layer film. In this development step, a 2.38% TMAH aqueous solution was used as a developer. The immersion coating film is removed by the development process, but the resist coating film is unexposed and remains as it is. Before and after this process, the film thickness is measured with Lambda Ace VM90 (Dainippon Screen Co., Ltd.). If the change in resist film thickness is within 0.5%, the resist film and the upper film for immersion are between It was judged that there was no intermixing of “○”, and when it exceeded 0.5%, it was judged as “X”.

(4) Stability evaluation of the upper layer film composition for immersion in water (water resistance)
A coating film (film thickness 30 nm) of the upper film composition for immersion was formed on an 8-inch silicon wafer by spin coating and PB (90 ° C., 60 seconds), and the film thickness was measured with Lambda Ace VM90. On the same substrate, ultrapure water was discharged onto the wafer for 60 seconds from a rinse nozzle of CLEAN TRACK ACT8, and then spin-dried by shaking off at 4000 rpm for 15 seconds. The film thickness of this substrate was measured again. At this time, if the amount of film thickness reduction was within 0.5% of the initial film thickness, it was judged as stable, and it was judged as “◯”, and when it exceeded 0.5%, it was judged as “x”.

(5) Patterning evaluation A resist patterning evaluation method using the upper layer film will be described.
A coating film was formed on an 8-inch silicon wafer by applying a lower layer antireflection film ARC29A (produced by Brewer Science Co., Ltd.) with a film thickness of 77 nm (PB205 ° C., 60 seconds) by spin coating, and then patterning of JSR ArF AR1221J was performed. AR1221J was applied by spin coating and PB (130 ° C., 90 seconds) to a film thickness of 205 nm, and after PB, the upper film was spin coated, and a coating film having a film thickness of 32 nm was formed by PB (90 ° C., 60 seconds). Next, with ArF projection exposure apparatus S306C (Nikon Corporation), exposure was performed under optical conditions of NA: 0.78, Sigma: 0.85, 2/3 Ann, and ultrapure water was supplied from the rinse nozzle of CLEAN TRACK ACT8. After discharging on the wafer for 60 seconds, spin drying was performed by shaking off at 4000 rpm for 15 seconds. Thereafter, PEB (130 ° C., 90 seconds) is performed on the CLEAN TRACK ACT8 hot plate, paddle development (60 seconds) with the LD nozzle of the CLEAN TRACK ACT8, rinse with ultrapure water, and then shaken off at 4000 rpm for 15 seconds. Spin dried.
The substrate was observed with a scanning electron microscope (S-9360, manufactured by Hitachi Sokki Co., Ltd.) for a 90 nm line and space pattern, and the exposure amount at which the line width was 90 nm was determined as the optimum exposure amount. The minimum dimension of the line-and-space pattern resolved at this optimum exposure amount was taken as the resolution. The results are shown in Table 3. Moreover, the cross-sectional shape of a 90 nm line and space pattern was observed. FIG. 1 shows a cross-sectional shape of a line and space pattern. When the line width Lb in the middle of the film of the pattern 2 formed on the substrate 1 and the line width La in the upper part of the film are measured, 0.9 <= (La−Lb) / Lb <= 1.1 Was evaluated as “rectangular”, (La−Lb) / Lb <0.9 as “taper”, and (La−Lb) / Lb> 1.1 as “head tension”.
(6) Measurement of contact angle DSA-10 made by KRUS was used for measurement of contact angle. 0.5 ml of pure water was dropped onto the substrate on which the coating film was formed, the contact angle after 2 to 11 seconds after dropping was measured every other second, and the average value was obtained as the contact angle.

  The above-described copolymer of the present invention dissolves in a solvent containing a monohydric alcohol and dissolves in an alkaline developer, so that it can be easily applied to a photoresist film. In particular, at the time of immersion exposure using water as a medium, an upper layer film-forming composition capable of protecting a lens and a resist and forming a resist pattern excellent in resolution, developability and the like can be obtained. Therefore, it can be used very suitably for the manufacture of semiconductor devices that are expected to be further miniaturized in the future.

It is a figure which shows the cross-sectional shape of a line and space pattern.

Explanation of symbols

1 substrate 2 pattern

Claims (10)

A copolymer for forming an upper layer film to be coated with a photoresist film to be subjected to immersion exposure, wherein the copolymer contains 20 to 60 mol% of repeating units having a carboxyl group, It contains a repeating unit derived from a hydroxyl group-containing (meth) acrylic acid alkyl ester, the hydroxyl group-containing (meth) acrylic acid alkyl ester is represented by the formula (3), and the weight average molecular weight measured by gel permeation chromatography is 2 A copolymer for a liquid immersion upper layer film, characterized by being from 1,000 to 100,000.

(In Formula (3), R represents a methyl group, R ′ and R ″ represent a hydrogen atom, and R ⁵ represents a divalent chain hydrocarbon group.) The divalent chain hydrocarbon group is a divalent saturated linear characterized in that it is a hydrocarbon group claim 1 immersion upper layer film for copolymer according. The divalent saturated chain hydrocarbon group is methylene group, ethylene group, 1,3-propylene group, 1,2-propylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group. , Nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group, tridecamethylene group, tetradecamethylene group, pentadecamethylene group, hexadecamethylene group, heptacamethylene group, octadecamethylene group, nonacamethylene group , Insalene group, 1-methyl-1,3-propylene group, 2-methyl-1,3-propylene group, 2-methyl-1,2-propylene group, 1-methyl-1,4-butylene group, 2- A methyl-1,4-butylene group, a methylidene group, an ethylidene group, a propylidene group, or a 2-propylidene group; Immersion upper layer film for copolymer of claim 2 wherein. A repeating unit derived from a monomer in which the repeating unit derived from the hydroxyl group-containing (meth) acrylic acid alkyl ester is substituted with a hydroxyl group in the following formula (1-2) together with the repeating unit derived from the formula (3). The copolymer for liquid immersion upper layer film according to claim 1, which is contained.

(In Formula (1-2), R represents a methyl group, R ′ and R ″ represent a hydrogen atom, R ¹ represents an alkylene group having 1 to 20 carbon atoms, a divalent bridged cyclic hydrocarbon ring group, Alternatively, it represents a divalent group derived from a polyalkylene glycol having 2 to 10 carbon atoms.) The copolymer for an upper liquid immersion film according to claim 4, wherein R ¹ is a divalent bridged cyclic hydrocarbon ring group. The divalent bridged cyclic hydrocarbon ring group is a 1,4-norbornylene group, a 2,5-norbornylene group, a 1,5-adamantylene group, or a 2,6-adamantylene group. Item 6. The copolymer for an immersion upper layer film according to Item 5 . The monomer in which the carboxyl group in the formula (1-2) is substituted with a hydroxyl group is 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2,3-dihydroxypropyl methacrylate. And at least one selected from polypropylene glycol methacrylate, 2-hydroxycyclohexyl methacrylate, 4-hydroxycyclohexyl methacrylate, 3-hydroxy-1-adamantyl methacrylate, and 3,5-dihydroxy-1-adamantyl methacrylate. 4. The copolymer for immersion upper layer film according to 4 . The liquid immersion upper layer according to any one of claims 1 to 7 , comprising a repeating unit obtained by copolymerizing a (meth) acrylic acid ester having a group containing a fluorine atom in its side chain. Copolymer for membrane. Having a group containing fluorine atom in its side chain (meth) according to claim 8, wherein that the acrylic acid ester is a fluoroalkyl group-containing (meth) acrylate is the number of carbon atoms of the fluoroalkyl group having 1 to 20 Copolymer for liquid immersion upper layer film. A resin composition for forming an upper layer film to be coated on a photoresist film to be subjected to immersion exposure,
The composition is characterized in that a resin dissolved in a developer is dissolved in a solvent containing a monohydric alcohol, and the resin is the copolymer according to any one of claims 1 to 9. A resin composition for a liquid immersion upper layer film.

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