JP4525454B2 - Upper layer film forming composition and photoresist pattern forming method - Google Patents

Description

  The present invention is an upper layer film useful for protecting a photoresist during immersion exposure used for lithography miniaturization and for forming an upper layer film that suppresses elution of a photoresist component and protects a lens of a projection exposure apparatus. The present invention relates to a forming composition and a method for forming a photoresist pattern using the upper film forming composition.

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, which is an essential technique for miniaturization of lithography, particularly lithography of several tens of nanometers. The projection exposure apparatus is also known (see Patent Document 1).
In the immersion exposure method, the photoresist film applied and formed on the wafer and the lens of the projection exposure apparatus are in contact with the immersion medium. Therefore, the immersion medium may penetrate into 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 by elution of components constituting the photoresist into the immersion medium.

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 and the immersion medium, for example, water, but this upper layer film has sufficient permeability to the wavelength of radiation. A protective film can be formed on the photoresist film without causing intermixing with the photoresist film, and a stable film can be maintained without leaching into the immersion medium during immersion exposure. It is necessary to form an upper layer film that dissolves in
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, an immersion upper layer film that can protect the resist film from the immersion liquid without deteriorating the original performance designed for dry use is required.
Japanese Patent Laid-Open No. 11-176727

  The present invention has been made in order to overcome such problems, and has sufficient transparency at exposure wavelengths, particularly 248 nm (KrF) and 193 nm (ArF), and can be used without intermixing with a photoresist film. An object of the present invention is to provide an upper film forming composition for immersion for forming an upper film that can form a film on a resist and that does not deteriorate in performance from dry exposure and that is easily dissolved in an alkaline developer. And

（式（１）においてＲ¹およびＲ²は、水素原子、炭素数１〜４のアルキル基、または炭素数１〜４のフルオロアルキル基であり、少なくとも一方は炭素数１〜４のフルオロアルキル基を表し、式（２）においてＲｆは、炭素数１〜１０のパーフルオロアルキル基、または炭素数３〜１０のパーフルオロシクロアルキル基を表す。）
また、上記式（１）で表される基を側鎖末端に有する繰り返し単位が下記式（１−１）で表されることを特徴とする。

（式（１−１）においてＲは水素原子または炭素数１〜４のアルキル基を、Ｒ³は２価の有機基をそれぞれ表す。）
また、上記式（２）で表される基を側鎖末端に有する繰り返し単位が下記式（２−１）で表されることを特徴とする。

（式（２−１）においてＲは水素原子または炭素数１〜４のアルキル基を、Ｒ⁴は２価の有機基を、Ｒｆは炭素数１〜１０のパーフルオロアルキル基または炭素数３〜１０のパーフルオロシクロアルキル基をそれぞれ表す。） The present invention relates to a composition for forming an upper layer film coated on a photoresist film, the composition comprising at least one of a resin that dissolves in a developer for developing the photoresist film, an acid, and a radiation-sensitive acid generator. It is characterized by including one.
The resin used in the upper layer film-forming composition is represented by the repeating unit having a group represented by the following formula (1) at the end of the side chain, the repeating unit having a carboxyl group at the end of the side chain, and the following formula (2). It is a resin containing at least one repeating unit selected from the group consisting of repeating units having a group at the end of the side chain.

(R ¹ and R ² in formula (1) represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a fluoroalkyl group having 1 to 4 carbon atoms, at least one of the fluoroalkyl group having 1 to 4 carbon atoms In the formula (2), Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluorocycloalkyl group having 3 to 10 carbon atoms.)
Moreover, the repeating unit which has group represented by the said Formula (1) in a side chain terminal is represented by following formula (1-1), It is characterized by the above-mentioned.

(In the formula (1-1), R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ³ represents a divalent organic group.)
Moreover, the repeating unit which has group represented by the said Formula (2) in the side chain terminal is represented by following formula (2-1), It is characterized by the above-mentioned.

(In Formula (2-1), R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁴ represents a divalent organic group, Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms, or 3 to 3 carbon atoms. Each represents 10 perfluorocycloalkyl groups.)

The acid used in the upper layer film-forming composition has a dissociation constant (pKa) of 2 or less.
Further, this acid is characterized in that it is an acid that is soluble in alcohol and has a sulfo group in the molecule.
The radiation-sensitive acid generator used in the upper layer film-forming composition is characterized by being dissolved in alcohol and generating an acid upon irradiation with radiation.
The photoresist pattern forming method of the present invention includes a step of applying a photoresist on a substrate to form a photoresist film, a step of forming the upper layer film of the present invention on the photoresist film, the photoresist film, and A step of forming a resist pattern by irradiating the upper layer film with radiation through a mask having a predetermined pattern via an immersion medium and then developing the film.

The composition for forming the upper layer film of the present invention can be easily applied to a photoresist film, and the formed upper layer film protects the lens and the resist during immersion exposure, and has resolution, developability, etc. It is possible to form a resist pattern having excellent patterning characteristics.
Therefore, it can be used very suitably for the manufacture of semiconductor devices that are expected to be further miniaturized in the future.

  The upper layer film obtained from the composition for forming the upper layer film for immersion prevents the photoresist film and the immersion medium from coming into direct contact during immersion exposure, and lithography of the photoresist film by penetration of the immersion medium. There is an effect of preventing the lens of the projection exposure apparatus from being contaminated by a component eluted from the photoresist film without deteriorating the performance.

The resin constituting the upper layer film-forming composition of the present invention is a resin that can form a stable film in an immersion medium, for example, water upon irradiation with radiation, and is soluble in a developer for forming a resist pattern. .
Here, the film that is stable in water at the time of radiation irradiation means that the change in film thickness is 3% or less of the initial film thickness as measured by the water stability evaluation method described later. 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 water and dissolves in the aqueous alkaline solution at the time of development using the aqueous alkaline solution after irradiation irradiated through water.

The alkali-soluble resin has a repeating unit having a group represented by formula (1) at a side chain end, a repeating unit having a carboxyl group at a side chain end, and a group represented by formula (2) at a side chain end. A resin containing at least one repeating unit selected from the group consisting of repeating units.
Examples of the main chain of the resin include addition polymerization resins or ring-opening polymerization resins of norbornene derivatives, norbornene derivatives and maleic anhydride copolymer resins, and addition polymerization resins of (meth) acrylic acid derivatives. Of these, addition polymerization resins of (meth) acrylic acid derivatives obtained by polymerizing radically polymerizable monomers are preferred.

R ¹ and R ² in Formula (1) are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a fluoroalkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, and t-butyl group. And the like. The C1-C4 fluoroalkyl group refers to a group in which part or all of the hydrogen atoms in the C1-C4 alkyl group are substituted with fluorine atoms.
Further, at least one of R ¹ and R ² is the above-described fluoroalkyl group having 1 to 4 carbon atoms.

式（１−１）においてＲは水素原子または炭素数１〜４のアルキル基を、Ｒ³は２価の有機基を、それぞれ表す。
炭素数１〜４のアルキル基としては、例えば、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、２−メチルプロピル基、１−メチルプロピル基、ｔ−ブチル基等のアルキル基が挙げられる。
２価の有機基としては、好ましくは２価の炭化水素基であり、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である。
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等が挙げられる
。 The repeating unit having a group represented by the formula (1) at the end of the side chain is a repeating unit having an alcoholic hydroxyl group having a fluoroalkyl group at least at the α-position carbon atom in the side chain. As the fluoroalkyl group, a trifluoromethyl group is preferable. By containing at least one fluoroalkyl group at the α-position, the hydrogen atom of the alcoholic hydroxyl group is easily released due to the electron withdrawing property of the fluoroalkyl group, and is acidic in an aqueous solution. Therefore, when the immersion medium is pure water, it becomes insoluble in the pure water, but becomes alkali-soluble.
As a preferred repeating unit having a group represented by the formula (1) at the end of the side chain, a repeating unit represented by the formula (1-1) can be mentioned.

In formula (1-1), R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ³ represents a divalent organic group.
Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, and t-butyl group. And the like.
The divalent organic group is preferably a divalent hydrocarbon group, and among the divalent hydrocarbon groups, a chain or cyclic hydrocarbon group is preferable.
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, 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 ³ 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.
R ³ is preferably a hydrocarbon group containing a 2,5-norbornylene group, 1, 2, ethylene group or propylene group.
The suitable radically polymerizable monomer which produces | generates the repeating unit represented by the said Formula (1-1) is represented below.

  The ratio of the radical polymerizable monomer that generates the repeating unit represented by the formula (1-1) is preferably 5 to 100 mol%, particularly preferably 10 to 90 mol%, based on the entire resin. Most preferably, it is 20-80 mol%. If the ratio of the radically polymerizable monomer is less than 5 mol%, not only the solubility of the resulting resin in an alcohol solvent is remarkably deteriorated, but also the solubility in an alkaline aqueous solution as a developing solution is remarkably reduced, and a photoresist is formed as a residue after development. May remain on the film.

Examples of the radical polymerizable monomer that gives a repeating unit having a carboxyl group include (meth) acrylic acid, crotonic acid, cinnamic acid, atropic acid, 3-acetyloxy (meth) acrylic acid, and 3-benzoyloxy (meth). Unsaturated monocarboxylic acids such as acrylic acid, α-methoxyacrylic acid, 3-cyclohexyl (meth) acrylic acid; unsaturated polycarboxylic acids such as fumaric acid, maleic acid, citraconic acid, mesaconic acid, itaconic acid; the unsaturated Monoesters such as monomethyl ester, monoethyl ester, mono n-propyl ester and mono n-butyl ester of polycarboxylic acid; 2- (meth) acrylamide-2-methylpropanecarboxylic acid, 2-α-carboxyacrylamide-2 -Methylpropanecarboxylic acid, 2-α-carboxymethylacrylami 2-methylpropanecarboxylic acid, 2-α-methoxycarbonylacrylamide-2-methylpropanecarboxylic acid, 2-α-acetyloxyacrylamide-2-methylpropanecarboxylic acid, 2-α-phenylacrylamide-2-methylpropanecarboxylic acid Acid, 2-α-benzylacrylamide-2-methylpropanecarboxylic acid, 2-α-methoxyacrylamide-2-methylpropanecarboxylic acid, 2-α-cyclohexylacrylamide-2-methylpropanecarboxylic acid, 2-α-cyanoacrylamide -2-methylpropanecarboxylic acid and the like.
Among the above, (meth) acrylic acid and crotonic acid are preferable.

  The proportion of the radically polymerizable monomer that gives the repeating unit having a carboxyl group is preferably 1 to 50 mol%, particularly preferably 1 to 40 mol%, more preferably 5 to 30 mol%, based on the entire resin. It is. When the ratio of the radically polymerizable monomer is less than 1 mol%, the solubility in an alkaline aqueous solution as a developer is remarkably lowered, and it may remain on the photoresist film as a residue after development. On the other hand, if it exceeds 50 mol%, the polarity becomes too high, and swelling, elution or peeling occurs due to contact with water during immersion exposure.

式（２−１）においてＲは水素原子または炭素数１〜４のアルキル基を表す。炭素数１〜４のアルキル基としては、例えば、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、２−メチルプロピル基、１−メチルプロピル基、ｔ−ブチル基等のアルキル基が挙げられる。
式（２−１）においてＲ⁴は２価の有機基を表す。
２価の有機基としては、好ましくは２価の炭化水素基であり、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である。
好ましいＲ⁴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
。 The repeating unit having a group represented by the formula (2) at the end of the side chain is preferably represented by the following formula (2-1).

In the formula (2-1), R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, and t-butyl group. And the like.
In the formula (2-1), R ⁴ represents a divalent organic group.
The divalent organic group is preferably a divalent hydrocarbon group, and among the divalent hydrocarbon groups, a chain or cyclic hydrocarbon group is preferable.
Preferred R ⁴ 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 ⁴ contains a divalent aliphatic cyclic hydrocarbon group, an alkylene group having 1 to 4 carbon atoms can be inserted as a spacer between the —NH— group and the aliphatic cyclic hydrocarbon group. it can.
R ⁴ is preferably a hydrocarbon group containing 2,5-norbornylene group or 1,5-adamantylene group, ethylene group, 1,3-propylene group.

In Formula (2-1), Rf is the same as Rf in Formula (2), and represents a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluorocycloalkyl group having 3 to 10 carbon atoms.
Rf includes trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, nonafluorobutyl group, undecafluoropentyl group, tridecafluorohexyl group, pentadecafluoroheptyl group, heptadecafluorooctyl group, nonadeca Linear perfluoroalkyl group such as fluorononyl group, (1-trifluoromethyl) tetrafluoroethyl group, (1-trifluoromethyl) hexafluoropropyl group, 1,1-bistrifluoromethyl-2,2,2 -A perfluorocycloalkyl group such as a branched perfluoroalkyl group such as a trifluoroethyl group, a cyclic perfluoroalkyl group such as a nonafluorocyclopentyl group and an undecafluorocyclohexyl group.
Among these, a trifluoromethyl group and a pentafluoroethyl group are preferable. Due to the electron-withdrawing effect of the fluoroalkyl group, the hydrogen atom of the amino group is likely to be eliminated and becomes acidic in an aqueous solution. Therefore, when the immersion medium is pure water, it is insoluble in the pure water, but is soluble in an alkaline aqueous solution.

  The ratio of the radically polymerizable monomer that gives the repeating unit represented by the formula (2-1) is preferably 5 to 100 mol%, particularly preferably 10 to 90 mol%, more particularly based on the whole resin. Preferably it is 20-80 mol%. If the ratio of the radically polymerizable monomer is less than 5 mol%, not only the solubility of the resulting resin in an alcohol solvent is remarkably deteriorated, but also the solubility in an alkaline aqueous solution as a developing solution is remarkably reduced, and a photoresist is formed as a residue after development. May remain on the film.

The suitable radically polymerizable monomer which produces | generates the repeating unit represented by the said Formula (2-1) is represented below.

The resin of the present invention can be copolymerized with other radical polymerizable monomers for the purpose of controlling the molecular weight of the resin, the glass transition point, the solubility in a solvent, and the like. “Other” means a radical polymerizable monomer other than the above-mentioned radical polymerizable monomers.
Suitable monomers that can be copolymerized include (meth) acrylic acid esters, hydroxyl group-containing (meth) acrylic acid esters, (meth) acrylic acid fluoroalkyl esters, and hydroxystyrenes.

(Meth) acrylic acid esters include (meth) acrylic acid alkyl esters, (meth) acrylic acid aryl esters, (meth) acrylic acid alicyclic alkyl esters, and the like.
Examples of (meth) acrylic acid esters include 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 (meta ) 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, -Adamantyl-1 Methylethyl (meth) acrylate, 1-bicyclo [2.2.1] heptyl-1-methylethyl (meth) acrylate, tricyclo [5.2.1.0 ^{2, 6]} decyl (meth) acrylate, phenyl (meth ) Acrylate, benzyl (meth) acrylate, among which n-butyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, tricyclo [5.2.1.0 ^2,6 ] Decyl (meth) acrylate is preferred.

The hydroxyl group-containing (meth) acrylic acid esters 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 thereof include dihydroxy-1-adamantyl (meth) acrylate, and among these, 2-hydroxyethyl (meth) acrylate and 3-hydroxy-1-adamantyl (meth) acrylate are preferable.
The (meth) acrylic acid esters and hydroxyl group-containing (meth) acrylic acid esters can be used alone or in admixture of two or more.

  Examples of (meth) acrylic acid fluoroalkyl esters include difluoromethyl (meth) acrylate, perfluoromethyl (meth) acrylate, 2,2-difluoroethyl (meth) acrylate, 2,2,2-trifluoroethyl (meta ) 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) Acrylate, 1- (Par (Luoroethyl) ethyl (meth) acrylate, 2- (perfluoroethyl) ethyl (meth) acrylate, 2,2,3,3,4,4-hexafluorobutyl (meth) acrylate, perfluoropropylmethyl (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, perfluorobutylmethyl (meth) acrylate, Perfluoropentyl (meth) acrylate, 1,1-dimethyl-2,2,3,3 , 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, perfluorohexyl (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-dodecaful Oloheptyl (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- (perfluoroheptyl) ethyl (meth) ) Acrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononyl (meth) acrylate, perfluorooctylmethyl (meta ) Acrylate, perfluorononyl (meth) acrylate, 2- (perfluorooctyl) ethyl (meth) ) Acrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-octadecafluorodecyl (meth) acrylate, perfluoro Nonylmethyl (meth) acrylate, perfluorodecyl (meth) acrylate, 2,2,3,4,4,4-hexafluorobutyl (meth) acrylate, 2,2,3,3,4,4,4-hepta Fluorobutyl (meth) acrylate, 3,3,4,4,5,5,6,6,6-nonafluorohexyl (meth) acrylate, 3,3,4,4,5,5,6,6,7 , 7,8,8,8-tridecafluorooctyl (meth) acrylate, etc., and fluoroalkyl (meth) acrylates having 1 to 20 carbon atoms in the fluoroalkyl group,

(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 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 an ester oxygen atom via a methylene group or an ethylene group.

  The proportion of fluoroalkyl (meth) acrylates in the alkali-soluble resin is usually 80 mol% or less, preferably 70 mol% or less. When there are too many of these repeating units, the solubility with respect to monohydric alcohol will become remarkably scarce, and it will become impossible to prepare as an upper film | membrane composition. Alternatively, the solubility in an alkaline aqueous solution, which is a developer, may be reduced after film formation, and may not be completely removed after development. Both of these defects may occur at the same time.

  Other dicarboxylic acid diesters such as diethyl maleate, diethyl fumarate and diethyl itaconate; aromatic vinyls such as styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene and p-methoxystyrene Nitrile group-containing radical polymerizable monomers such as acrylonitrile and methacrylonitrile; Amide bond-containing radical polymerizable monomers such as acrylamide and methacrylamide; Fatty acid vinyls such as vinyl acetate; Chlorine such as vinyl chloride and vinylidene chloride Contained radically polymerizable monomers; conjugated diolefins such as 1,3-butadiene, isoprene and 1,4-dimethylbutadiene can be used.

  Examples of the polymerization solvent used in producing the alkali-soluble resin include alcohols such as methanol, ethanol, ethylene glycol, diethylene glycol and propylene glycol; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol monomethyl ether and ethylene glycol monoethyl. Polyhydric alcohols such as 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 monoethyl ether Alkyl ethers of ethylene glycol ethyl ether acetate, diethylene glycol ethyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate and other polyhydric alcohol alkyl ether acetates; toluene, xylene and other aromatic hydrocarbons; acetone , Ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol; ethyl acetate, butyl acetate, ethyl 2-hydroxypropionate, 2-hydroxy-2-methylpropion Ethyl acetate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, 2-hydroxy-3- Methyl Chirubutan acid, methyl 3-methoxypropionate, 3-methoxypropionate, ethyl 3-ethoxy ethyl propionate, methyl 3-ethoxypropionate, ethyl acetate, esters such as butyl acetate. 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.

  The mass average molecular weight (hereinafter abbreviated as Mw) of the alkali-soluble resin of the present invention obtained by the above method is usually 2,000 to 200,000 in terms of polystyrene by gel permeation chromatography (GPC), preferably 2 , 500 to 100,000, more preferably 3,000 to 50,000. In this case, when the Mw of the alkali-soluble resin is less than 2,000, the water resistance and mechanical properties as the upper layer film are remarkably low. On the other hand, when the Mw exceeds 200,000, the solubility in a solvent described later is remarkably poor. The ratio (Mw / Mn) of the resin 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. is there. In addition, it is preferable that the resin 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 resin 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. . In this invention, resin can be used individually or in mixture of 2 or more types.

It is preferable that the acid which can be mix | blended with the said resin is not a polymer but a dissociation constant (pKa) is 2 or less as a compound. When the dissociation constant (pKa) exceeds 2, problems such as a cross-sectional shape of the resist pattern after development occur.
The acid having a dissociation constant (pKa) of 2 or less is preferably an organic acid, and examples thereof include an acid having a sulfo group (—SO ₂ OH) in the molecule and an acid having a carboxyl group.
Among organic acids, sulfonic acids which are acids having a sulfo group (—SO ₂ OH) in the molecule are preferable because the dissociation constant (pKa) is small and the acidity is high.
As the sulfonic acid, trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, heptafluoropropanesulfonic acid, nonafluorobutanesulfonic acid, dodecafluoropentanesulfonic acid, tridecafluorohexanesulfonic acid, pentadecafluoroheptanesulfonic acid, Heptadecafluorooctanesulfonic acid, octadecafluorononanesulfonic acid, fluoromethanesulfonic acid, difluoromethanesulfonic acid, 1,1-difluoroethanesulfonic acid, 2,2,2-trifluoroethanesulfonic acid, 1,1-difluoro Propanesulfonic acid, 1,1,2,2-tetrafluoropropanesulfonic acid, 3,3,3-trifluoropropanesulfonic acid, 2,2,3,3,4,4,4-heptafluorobutanesulfone Acid 3,3,4,4,4-pentafluo Fluoroalkylsulfonic acids such as butanesulfonic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, isopropanesulfonic acid, butanesulfonic acid, isobutanesulfonic acid, 1,1-dimethylethanesulfonic acid, pentanesulfonic acid, 1- Alkyl sulfonic acids such as methyl butane sulfonic acid, 2-methyl butane sulfonic acid, 3-methyl butane sulfonic acid, neopentane sulfonic acid, hexane sulfonic acid, hebutane sulfonic acid, octane sulfonic acid, nonane sulfonic acid, decane sulfonic acid, Benzenesulfonic acid, 2-toluenesulfonic acid, 3-toluenesulfonic acid, 4-toluenesulfonic acid, 4-ethylbenzenesulfonic acid, 4-propylbenzenesulfonic acid, 4-butylbenzenesulfonic acid, 4- (t-butyl) benzene Sul Phosphonic acid, 2,5-dimethylbenzenesulfonic acid, 2-mesitylenesulfonic acid, 2,4-dinitrobenzenesulfonic acid, 4-chlorobenzenesulfonic acid, 4-bromobenzenesulfonic acid, 4-fluorobenzenesulfonic acid, 2,3 , 4,5,6-pentafluorobenzenesulfonic acid, 4-hydroxybenzenesulfonic acid, 4-sulfobenzoic acid, arylsulfonic acids such as 4-sulfoaniline, aralkylsulfonic acids such as benzylsulfonic acid and phenethylsulfonic acid, camphor And cyclic sulfonic acids such as sulfonic acid.
The above acids can be used alone or as a mixed acid.

The radiation-sensitive acid generator that can be blended with the resin is a component that generates an acid upon irradiation with radiation, an onium salt compound, a sulfonyloxyimide compound, a disulfonyldiazomethane compound, a sulfone compound, a sulfonic acid ester compound, Examples include oxime sulfonate compounds and hydrazine sulfonate compounds.
Among these acid generators, preferred are onium salt compounds and sulfonyloxyimide compounds which are soluble in alcohols, preferably monohydric alcohols, more preferably monohydric alcohols having 10 or less carbon atoms. By being an onium salt compound or a sulfonyloxyimide compound that dissolves in a monohydric alcohol, the cross-sectional shape of the resist pattern does not cause problems such as a headache.
Examples of the onium salts include iodonium salts, sulfonium salts, phosphonium salts, diazonium salts, ammonium salts, pyridinium salts, and the like, and iodonium salts and sulfonium salts are preferable.

Preferred examples of the acid generator include triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoro-n-butanesulfonate, triphenylsulfonium perfluoro-n-octanesulfonate, triphenylsulfonium 2-bicyclo [2.2.1]. ] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium 2- (3-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecanyl) -1 , 1-difluoroethanesulfonate, triphenylsulfonium N, N-bis (nonafluoro-n-butanesulfonyl) imidate, triphenylsulfonium camphorsulfonate,

4-cyclohexylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-cyclohexylphenyldiphenylsulfonium perfluoro-n-octanesulfonate, 4-cyclohexylphenyldiphenylsulfonium 2-bicyclo [2. 2.1] Hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium 2- (3-tetracyclo [4.4.0.1 ^2,5 .1 ^{7, 10]} dodecanyl) -1,1-difluoroethanesulfonate, 4-cyclohexyl-phenyl diphenyl sulfonium N, N-bis (nonafluoro -n- butanesulfonyl) imidate, 4-sik Hexylphenyl camphorsulfonate,

4-t-butylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-t-butylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-t-butylphenyldiphenylsulfonium perfluoro-n-octanesulfonate, 4-t-butylphenyl Diphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-t-butylphenyldiphenylsulfonium 2- (3-tetracyclo [4.4. 0.1 ^2,5 .1 ^7,10 ] dodecanyl) -1,1-difluoroethanesulfonate, 4-t-butylphenyldiphenylsulfonium N, N-bis (nonafluoro-n-butanesulfonyl) imidate, 4-t-butyl Phenyldiphenyl Rufonium camphorsulfonate, tri (4-t-butylphenyl) sulfonium trifluoromethanesulfonate, tri (4-t-butylphenyl) sulfonium nonafluoro-n-butanesulfonate, tri (4-t-butylphenyl) sulfonium perfluoro- n-octanesulfonate, tri (4-t-butylphenyl) sulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, tri (4-t- butylphenyl) sulfonium 2- (3-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecanyl) -1,1-difluoroethanesulfonate, tri (4-t- butylphenyl) sulfonium N, N -Bis (nonafluoro-n-butanesulfonyl) imidate, tri (4- - butylphenyl) sulfonium camphorsulfonate,

Diphenyliodonium trifluoromethanesulfonate, diphenyliodonium nonafluoro-n-butanesulfonate, diphenyliodonium perfluoro-n-octanesulfonate, diphenyliodonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2, 2-tetrafluoroethane sulfonate, diphenyliodonium 2- (3-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecanyl) -1,1-difluoroethanesulfonate, diphenyliodonium N, N-bis ( Nonafluoro-n-butanesulfonyl) imidate, diphenyliodonium camphorsulfonate, bis (4-t-butylphenyl) iodonium trifluoromethanesulfonate, bis (4-t-butylphenyl) iodonium Fluoro-n-butanesulfonate, bis (4-t-butylphenyl) iodonium perfluoro-n-octanesulfonate, bis (4-t-butylphenyl) iodonium 2-bicyclo [2.2.1] hept-2-yl 1,1,2,2-tetrafluoroethane sulfonate, bis (4-t- butylphenyl) iodonium 2- (3-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecanyl) - 1,1-difluoroethanesulfonate, bis (4-t-butylphenyl) iodonium N, N-bis (nonafluoro-n-butanesulfonyl) imidate, bis (4-t-butylphenyl) iodonium camphorsulfonate,

1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, (4-n-Butoxynaphthalen-1-yl) tetrahydrothiophenium perfluoro-n-octanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium 2-bicyclo [2.2. 1] Hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium 2- (3-tetracyclo [4.4. 0.1 ^2,5 .1 ^7,10] dodecanyl) -1,1-difluoroethanesulfonate, 1- (4 n- butoxy naphthalen-1-yl) tetrahydrothiophenium N, N-bis (nonafluoro -n- butanesulfonyl) imidate, 1- (4-n- butoxy-naphthalene-1-yl) tetrahydrothiophenium camphorsulfonate,

1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, (3,5-Dimethyl-4-hydroxyphenyl) tetrahydrothiophenium perfluoro-n-octanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium 2-bicyclo [2.2. 1] Hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium 2- (3-tetracyclo [4.4. 0.1 ^2,5 .1 ^7,10] dodecanyl) -1,1-difluoroethane scan Phonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium N, N-bis (nonafluoro-n-butanesulfonyl) imidate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydro Thiophenium camphorsulfonate,

N- (trifluoromethanesulfonyloxy) succinimide, N- (nonafluoro-n-butanesulfonyloxy) succinimide, N- (perfluoro-n-octanesulfonyloxy) succinimide, N- (2-bicyclo [2.2.1] Hept-2-yl-1,1,2,2-tetrafluoroethanesulfonyloxy) succinimide, N- (2- (3-tetracyclo [4.4.0.1 ^2,5 .1, ^7,10 ] dodecanyl) -1,1-difluoroethanesulfonyloxy) succinimide, N- (camphorsulfonyloxy) succinimide,

N- (trifluoromethanesulfonyloxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboximide, N- (nonafluoro-n-butanesulfonyloxy) bicyclo [2.2.1] hept -5-ene-2,3-dicarboximide, N- (perfluoro-n-octanesulfonyloxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboximide, N- ( 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonyloxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboxy imide, N- (2- (3- tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecanyl) -1,1-difluoroethane-sulfonyloxy) bicyclo [2.2.1] hept -5 -D 2,3-dicarboximide, N- (camphorsulfonyloxy oxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboximide, and the like.
The acid generator can be used as a single acid generator or a mixed acid generator.

The acid and the radiation sensitive acid generator can be used alone or as a mixture in an alkali-soluble resin.
With respect to 100 parts by mass of the resin component constituting the resin composition, the blending amount of at least one of the acid and the radiation-sensitive acid generator exceeds 0.05 parts by mass and is 20 parts by mass or less, preferably 0.1 to 15 parts. Part by mass, more preferably 0.5 to 10 parts by mass. If it is 0.05 parts by mass or less, a resist pattern having excellent patterning characteristics cannot be formed. When the amount exceeds 20 parts by mass, the film thickness of the resist film decreases after development, and the resist pattern tends to become tapered after development.
Moreover, when mix | blending as a mixture of an acid and a radiation sensitive acid generator, the mixing ratio of an acid and a radiation sensitive acid generator is although there is no restriction | limiting in particular, 10/1-1/10 are preferable.

The upper layer film-forming composition of the present invention is obtained by dissolving the above-described resin dissolved in the developer after irradiation and an acid or a radiation-sensitive acid generator in a solvent containing alcohol. As the alcohol, a monohydric alcohol is preferable. Further, a monohydric alcohol having 10 or less carbon atoms dissolves the above components, and when applied on the photoresist film, it causes intermixing with the photoresist film to improve lithography performance. It is preferable because it does not deteriorate.
Examples of the monohydric alcohol having 10 or less carbon atoms include methanol, ethanol, 1-propanol, isopropanol, n-propanol, 1-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 -C1-C6 monohydric alcohols such as pentanol and 4-methyl-2-pentanol; 2 2-dimethyl-3-pentanol, 2,3-dimethyl-3-pentanol, 2,4-dimethyl-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, etc. 2-ethyl-1-hexanol, 4-methyl-3-heptanol, 6-methyl-2-heptanol, 1-octanol, 2-octanol, 3-octanol, 2-propyl-1-pentanol C8 monohydric alcohols such as 2,4,4-trimethyl-1-pentanol; 2,6-dimethyl-4-heptanol, 3- C9 monohydric alcohols such as til-2,2-dimethyl-pentanol, 1-nonanol, 2-nonanol, 3,5,5-trimethyl-1-hexanol; 1-decanol, 2-decanol, 4 -Monohydric alcohols having 10 carbon atoms such as decanol, 3,7-dimethyl-1-octanol, 3,7-dimethyl-3-octanol and the like.
Among the monohydric alcohols, 4-methyl-2-pentanol, butanol, hexanol, or a mixed alcohol thereof is preferable because it hardly solidifies at low temperatures and hardly remains in the film during film formation.
Further, the amount of monohydric alcohol having 10 or less carbon atoms in the solvent containing alcohol is usually 10 with respect to all the solvents because it is difficult to coagulate at low temperature and hardly remains in the film during film formation. It is -100 mass%, Preferably it is 20-100 mass%.

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 and 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, ethyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate , Ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, 3- 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 for adjusting the coating performance is 30% by mass or less, preferably 20% by mass or less in the solvent component. If it exceeds 30% by mass, the photoresist film is eroded, causing problems such as intermixing with the upper film, and the resolution performance of the photoresist is significantly deteriorated.

A surfactant may be added to the composition for forming an upper layer film for immersion according to the present invention for the purpose of improving coating properties, antifoaming properties, leveling properties 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 mass or less with respect to 100 parts by mass of the alkali-soluble resin.

The photoresist pattern forming method of the present invention will be described.
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 for immersion formed with the composition 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.
For the photoresist film, the resin for forming the photoresist film is dissolved in a suitable solvent at a solid content concentration of, for example, 0.1 to 20% by mass, and then filtered through a filter having a pore diameter of, for example, 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.
Moreover, the density | concentration of resin in the upper film | membrane formation composition for immersion is 0.1-20 mass% normally, Preferably it is 0.1-10 mass%, Most preferably, it is 0.1-5 mass%.

The step of forming an upper layer film on the photoresist film using the liquid immersion 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 firing again. This is a step of forming an upper layer film of the present invention. 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 film with radiation through a mask having a predetermined pattern using an immersion medium, for example, water, and then developing is performed by immersion exposure. This is a step of developing after baking at a predetermined 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.
Next, the photoresist film is developed with a developer and washed to form a desired resist pattern. In this case, the upper film for immersion according to 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 is dissolved. In addition, an appropriate amount of a water-soluble organic solvent, for example, an alcohol such as methanol or ethanol, or 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.

Resin synthesis examples Resins (A-1) to (A-3) that can form a stable film in an immersion medium at the time of radiation irradiation, such as water, and are dissolved in the developer after forming the resist pattern are synthesized by the following method. did. The Mw of the resins (A-1) to (A-3) is GPC columns (2 G2000HXL, 1 G3000HXL, 1 G4000HXL) manufactured by Tosoh Corporation, and the flow rate is 1.0 ml / min. Measurement was performed by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard under the analysis conditions of tetrahydrofuran and a column temperature of 40 ° C.
Moreover, the monomer used for each resin synthesis | combination other than the monomer (M-1) and monomer (M-5) mentioned above is represented below as (M-9)-(M-11).

A monomer solution prepared by dissolving resins (A-1) to (A-3) in the amounts shown in Table 1 and an initiator (methyl azobisisobutyrate) in 60 g of isopropanol was prepared. In Table 1, the numbers in parentheses are molar ratios.
30 g of isopropanol was added to a 500 ml three-neck flask equipped with a thermometer and a dropping funnel, and a nitrogen purge was performed for 30 minutes. The flask was heated to 80 ° C. while stirring with a magnetic stirrer. The monomer solution prepared in advance was added to the dropping funnel and dropped over 3 hours. The reaction was continued for another 3 hours after the completion of the dropwise addition, and the mixture was cooled to 30 ° C. or lower.
After cooling, the polymerization solution was concentrated to 60 g, transferred to a separatory funnel together with 60 g of methanol and 500 g of n-heptane, and after stirring sufficiently, the lower layer was separated. The lower layer was mixed with 60 g of methanol and 500 g of n-heptane, transferred to a separatory funnel, and the lower layer was separated. The lower layer obtained here was solvent-substituted with 1-butanol, 4-methyl-2-pentanol or 1-hexanol. The solid content concentration of the solvent-substituted sample was calculated from the mass of the residue when heated for 2 hours on a hot plate heated to 140 ° C. with 0.3 g of the resin solution placed on an aluminum pan, and then the upper layer film It was used for solution preparation and yield calculation. The obtained resin solution was measured for molecular weight, molecular weight dispersity, and yield. The results are shown in Table 1.

Examples 1 to 21 and Comparative Examples 1 to 3
The upper layer film-forming composition is composed of the above resins (A-1) to (A-3), the following radiation sensitive acid generators (B-1) to (B-7) and / or acids (C-1) to (C-2).
Radiation sensitive acid generator (B)
(B-1): Triphenylsulfonium trifluoromethanesulfonate (B-2): Triphenylsulfonium nonafluoro-n-butanesulfonate (B-3): 4-cyclohexylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate ( B-4): 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate (B-5): 1- (4-n-butoxynaphthalen-1-yl) Tetrahydrothiophenium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate (B-6): bis (4-t-butylphenyl) iodonium nona Fluoro-n-butanesulfonate (B-7): N- (nonafluoro-n-butanesulfonyl) Oxy) bicyclo [2.2.1] hept-5-ene-2,3-dicarboximide acid (C)
(C-1): Camphorsulfonic acid (C-2): Toluenesulfonic acid Mass ratio of resin (A) and radiation-sensitive acid generator (B) and / or acid (C) shown in Table 2 in parentheses Were added to the mixture, and the solvent shown in Table 2 was added so as to obtain a 1.5% by mass solution. 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 2, 4M2P represents 4-methyl-2-pentanol, B represents n-butanol, and H represents n-hexanol.
In addition, Comparative Example 1 is shown as a reference example, and is an example in which patterning evaluation was performed without adding a radiation-sensitive acid generator (B) or acid (C). Comparative Example 2 was triphenylsulfonium trifluoromethanesulfonate. Is an example of 0.05 part by mass with respect to 100 parts by mass of the resin component, and Comparative Example 3 is an example exceeding 20 parts by mass.

The obtained upper layer film-forming composition was evaluated by the following method. The results are shown in Table 2.
(1) Solubility evaluation method (solubility)
About Examples 1-21 and Comparative Examples 1-3, resin (A) and a radiation sensitive acid generator (B) and / or acid (C) are mixed by the ratio (mass ratio) shown in the parenthesis of Table 2. And the solvent shown in Table 2 was added so that it might become a 1.5 mass% solution, and it stirred at 100 rpm for 3 hours using the three one motor. The resin (A) used was a resin solution obtained by drying the resin solution at 100 ° C. for 24 hours. Then, if the mixture of the resin and the solvent is a visually uniform solution, it is judged that the solubility is good, and if the undissolved or white turbidity is seen, the solubility is poor and “×” did.
(2) Evaluation method of removability of upper layer film (removability)
The upper layer film was spin-coated on an 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 mass% TMAH aqueous solution) for 60 seconds with CLEAN TRACK ACT8, spin-dried by shaking, and the wafer surface was observed. At this time, if the development was made without any residue by visual observation, the removability was evaluated as “◯”, and if the residue was observed as “X”.
(3) Patterning evaluation An evaluation method for resist patterning using the upper layer film will be described.
After a coating film was formed on an 8-inch silicon wafer with a lower layer antireflection film ARC29A (Brewer Science Co., Ltd.) with a film thickness of 77 nm (PB205 ° C., 60 seconds) by spin coating, patterning of JSR ArF AR1682J was performed. AR1682J was applied by spin coating and PB (110 ° C., 90 seconds) to a film thickness of 205 nm. After PB, the upper layer 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 a 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 (110 ° 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 cross-sectional shape of the 90 nm line and space pattern is observed at this optimum exposure amount, and the line width Lb in the middle of the film and the line width La in the upper part of the film are measured, and 0.9 ≦ (La−Lb) / Evaluation when Lb ≦ 1.1 is “rectangular”, when (La−Lb) / Lb <0.9 is “tapered”, and when (La−Lb) / Lb> 1.1 is evaluated as “head tension” did. In addition, the minimum line and space pattern size that can be resolved with the optimum exposure dose is taken as the resolution.

  The composition for forming an upper layer film for immersion according to the present invention comprises an immersion medium upon irradiation with radiation, for example, a resin that forms a stable film in water and dissolves in a developer after forming a resist pattern, and an acid and radiation-sensitive acid generator. Since it contains at least one of the agents, the lens and the photoresist film can be protected during immersion exposure, and a resist pattern excellent in resolution, developability, etc. can be formed, and further miniaturization is expected in the future. It can be used very suitably for the manufacture of semiconductor devices.

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

Explanation of symbols

1 substrate 2 pattern

Claims (8)

An upper film forming composition coated on a photoresist film,
The composition comprises an upper layer film-forming composition comprising a resin that dissolves in a developer for developing the photoresist film, and at least one of an acid and a radiation-sensitive acid generator. The resin has a repeating unit having a group represented by the following formula (1) at the end of the side chain, a repeating unit having a carboxyl group at the end of the side chain, and a group represented by the following formula (2) at the end of the side chain. 2. The upper layer film-forming composition according to claim 1, wherein the upper layer film-forming composition is a resin containing at least one repeating unit selected from the group consisting of repeating units.

(R ¹ and R ² in formula (1) represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a fluoroalkyl group having 1 to 4 carbon atoms, at least one of the fluoroalkyl group having 1 to 4 carbon atoms In the formula (2), Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms or a perfluorocycloalkyl group having 3 to 10 carbon atoms.) The upper layer film-forming composition according to claim 2, wherein the repeating unit having a group represented by the formula (1) at a side chain end is represented by the following formula (1-1).

(In the formula (1-1), R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ³ represents a divalent organic group.) The upper layer film-forming composition according to claim 2, wherein the repeating unit having a group represented by the formula (2) at a side chain end is represented by the following formula (2-1).

(In Formula (2-1), R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁴ represents a divalent organic group, Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms, or 3 to 3 carbon atoms. Each represents 10 perfluorocycloalkyl groups.) 2. The upper layer film-forming composition according to claim 1, wherein the acid has a dissociation constant (pKa) of 2 or less. 6. The upper layer film-forming composition according to claim 5, wherein the acid is an acid that dissolves in alcohol and has a sulfo group in the molecule. The upper-layer film-forming composition according to claim 1, wherein the radiation-sensitive acid generator is dissolved in alcohol and generates an acid upon irradiation with radiation. Applying a photoresist on the substrate to form a photoresist film, forming an upper layer film on the photoresist film, and forming a predetermined pattern on the photoresist film and the upper layer film via an immersion medium; A method of forming a resist pattern by irradiating radiation through a mask having, and then developing, to form a resist pattern,
The method for forming a photoresist pattern, wherein the step of forming the upper layer film is a step of forming an upper layer film using the upper layer film forming composition according to any one of claims 1 to 7.

Images