JP2011227290A - Material for forming protective film and forming method for resist pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for forming a protective film which is capable of improving water repellency while suppressing a deterioration in alkali solubility of the protective film, and to provide a forming method for a resist pattern using the material for forming a protective film.SOLUTION: A material for forming a protective film contains an alkali-soluble polymer having a structural unit derived from a monomer represented by formula (A-1). In the formula, Rrepresents a group expressed by formula (a-1) or formula (a-2), Qrepresents a divalent linkage group which may have a single bond or a fluorine atom, and Rrepresents an organic group which may have a fluorine atom.

Description

  The present invention relates to a protective film forming material for forming a protective film laminated on a resist film, and a resist pattern forming method using the protective film forming material.

  Conventionally, an immersion exposure process has attracted attention as a new lithography technique (see Non-Patent Documents 1 to 3). According to this immersion exposure process, the conventional exposure optical path space is replaced with a so-called immersion exposure liquid (pure water, etc.), so that even with a light source having the same exposure wavelength, a higher resolution and depth of focus can be achieved. It is possible to form an excellent resist pattern.

  In this immersion exposure process, since the exposure is performed with the immersion exposure liquid interposed on the resist film, as a matter of course, the resist film is altered by the immersion exposure liquid, and the elution component from the resist film. There is a concern about the refractive index fluctuation accompanying the alteration of the liquid for immersion exposure due to.

  Under such circumstances, by forming a protective film using a fluorine-containing resin on the resist film and interposing an immersion exposure liquid on the protective film, the resist film can be altered and liquid by the immersion exposure liquid. There has been proposed a technique aimed at simultaneously preventing refractive index fluctuations accompanying alteration of the immersion exposure liquid itself (see Patent Document 1).

  In addition, from the viewpoints of simplifying the resist pattern formation process and improving production efficiency, by using a protective film using an alkali-soluble polymer, removal of the protective film and unnecessary resist film during alkali development after immersion exposure A technique has been proposed in which a resist pattern is obtained by simultaneously removing the resist (see Patent Document 2).

International Publication No. 2004/074937 Pamphlet JP 2005-157259 A

"Journal of Vacuum Science & Technology B", (USA), 1999, Vol. 17, No. 6, pp. 3306-3309 "Journal of Vacuum Science & Technology B", (USA), 2001, Vol. 19, No. 6, pp. 2353-2356 “Proceedings of SPIE” (USA), 2002, 4691, pages 459-465.

  By the way, in recent years, a local liquid immersion exposure process in which only a space between an exposure lens that scans at a high speed and a substrate on which a protective film is formed on a resist film is filled with liquid for liquid immersion exposure has been studied. In the local liquid immersion exposure process, for example, a substrate on which a protective film / resist film is formed is placed on a wafer stage, an exposure lens is arranged above the protective film at a predetermined interval, and the exposure lens is moved at a high speed. While performing scanning movement, the liquid for immersion exposure is continuously dropped from one nozzle onto the protective film, and at the same time, the liquid is sucked from the other nozzle and exposed.

  In this local liquid immersion exposure process, the liquid for immersion exposure needs to follow the scanning exposure lens. For this reason, the protective film is required to have high water repellency. Particularly recently, since the scanning speed of the immersion exposure machine has been increasing year by year in order to improve the throughput, a protective film with higher water repellency has been demanded.

  However, in the case of a protective film using an alkali-soluble polymer, water repellency and alkali solubility are in a trade-off relationship, and thus there is a problem that alkali solubility is lowered when water repellency is improved. One of the causes is that the influence of the structural unit mainly contributing to water repellency among the structural units of the alkali-soluble polymer on the alkali solubility is great. Therefore, if it is possible to reduce the influence of this structural unit on the alkali solubility, it is considered that the water repellency can be improved while suppressing the decrease in the alkali solubility of the protective film. The material has not been known so far.

  The present invention has been made in view of the above problems, and provides a protective film-forming material capable of improving water repellency while suppressing a decrease in alkali solubility of the protective film, and the protective film-forming material. It is an object of the present invention to provide a used resist pattern forming method.

  The inventors of the present invention have made extensive studies to achieve the above object. As a result, it has been found that the above problem can be solved by including an alkali-soluble polymer having a specific structural unit in the protective film forming material, and the present invention has been completed. Specifically, the present invention provides the following.

［式中、Ｒ^０は下記式（ａ−１）又は式（ａ−２）で表される基を示し、Ｑ^０はフッ素原子を有していてもよい２価の連結基を示し、Ｒ^１はフッ素原子を有していてもよい有機基を示し、ｎは０又は１を示す。

（式中、Ｒ^０１は水素原子、又は炭素数１〜５のアルキル基若しくはハロゲン化アルキル基を示し、Ｒ^０２は水素原子、又は炭素数１〜６のアルキル基若しくはハロゲン化アルキル基を示し、Ｚは炭素数１若しくは２のアルキレン基又は酸素原子を示し、ｍは０〜３の整数を示す。）］ A first aspect of the present invention is a protective film-forming material for forming a protective film laminated on a resist film, the structural unit derived from a monomer represented by the following formula (A-1) A protective film-forming material containing an alkali-soluble polymer.

[Wherein, R ⁰ represents a group represented by the following formula (a-1) or (a-2), Q ⁰ represents a divalent linking group optionally having a fluorine atom, and R ¹ represents an organic group which may have a fluorine atom, and n represents 0 or 1.

(In the formula, R ⁰¹ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group, R ⁰² represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a halogenated alkyl group, Z represents an alkylene group having 1 or 2 carbon atoms or an oxygen atom, and m represents an integer of 0 to 3)]

In the present application, “structural unit” means a monomer unit (monomer unit) constituting a polymer compound (polymer, copolymer).
Moreover, the linking group or the organic group “may have a fluorine atom” means that part or all of the hydrogen atoms of the linking group or the organic group may be substituted with a fluorine atom. .

  A second aspect of the present invention is a resist pattern forming method using an immersion exposure process, wherein a resist film is provided on a substrate, and the protective film forming material according to the present invention is used on the resist film. Forming a protective film, and placing an immersion exposure liquid on at least the protective film of the substrate, and selectively exposing the resist film through the immersion exposure liquid and the protective film. And a developing step of developing the resist film after exposure by removing the protective film with a developer.

  The present invention provides a protective film forming material capable of improving water repellency while suppressing a decrease in alkali solubility of the protective film, and a resist pattern forming method using the protective film forming material. be able to.

≪Material for protective film formation≫
The material for forming a protective film according to the present invention contains an alkali-soluble polymer having a specific structural unit. Hereinafter, each component contained in the material for forming a protective film according to the present invention will be described.

<(A) Alkali-soluble polymer>
[Structural Unit Derived from Monomer Represented by Formula (A-1)]
The alkali-soluble polymer has at least a structural unit derived from a monomer represented by the following formula (A-1). When the alkali-soluble polymer has such a structural unit, water repellency can be improved while suppressing a decrease in alkali solubility of the protective film to be formed.

In the above formula (A-1), R ⁰ represents a group represented by the following formula (a-1) or formula (a-2).

In the above formula (a-1), R ⁰¹ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group.
Examples of the alkyl group having 1 to 5 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, and neopentyl group. A linear or branched alkyl group is mentioned.
Examples of the halogenated alkyl group having 1 to 5 carbon atoms include groups in which part or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms are substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.
R ⁰¹ is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a fluorinated alkyl group, more preferably a hydrogen atom or a methyl group, and further preferably a methyl group.

In the formula (a-2), R ⁰² represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a halogenated alkyl group.
Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group, isopentyl group, cyclopentyl group, n -A linear, branched, or cyclic alkyl group such as a hexyl group, an isohexyl group, or a cyclohexyl group.
Examples of the halogenated alkyl group having 1 to 6 carbon atoms include groups in which some or all of the hydrogen atoms of the above alkyl group having 1 to 6 carbon atoms have been substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable. The halogenated alkyl group is preferably a perfluoroalkyl group in which all of the hydrogen atoms are substituted with fluorine atoms from the viewpoint of improving water repellency.
R ⁰² is preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a fluorinated alkyl group, more preferably a hydrogen atom or a perfluoroalkyl group having 1 to 6 carbon atoms, More preferably.

In said formula (a-2), Z shows a C1-C2 alkylene group or an oxygen atom, and a methylene group is preferable.
m represents an integer of 0 to 3, and m = 0 is preferable.

In the above formula (A-1), Q ⁰ represents a divalent linking group which may have a fluorine atom.
Examples of the divalent linking group include a divalent hydrocarbon group which may have a substituent. The hydrocarbon group may be an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group containing both.

The aliphatic hydrocarbon group may be saturated or unsaturated, but is preferably saturated. More specifically, a linear or branched aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing a ring in the structure, and the like can be given.
The linear or branched aliphatic hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 5 carbon atoms.
The linear aliphatic hydrocarbon group is preferably a linear alkylene group, and specific examples include a methylene group, an ethylene group, a propylene group, a butylene group, and a pentylene group.
As the branched aliphatic hydrocarbon group, a branched alkylene group is preferred, and specifically, —CH (CH ₃ ) —, —CH (CH ₂ CH ₃ ) —, —C (CH ₃ ). _{2 -, - C (CH 3} ) (CH 2 CH 3) -, - C (CH 3) (CH 2 CH 2 CH 3) -, - C (CH 2 CH 3) 2 - ; alkylethylene groups such as - _{CH (CH 3) CH 2 -} , - CH (CH 3) CH (CH 3) -, - C (CH 3) 2 CH 2 -, - CH (CH 2 CH 3) CH 2 -, - C (CH 2 An alkylethylene group such as CH ₃ ) ₂ CH ₂ —; an alkylpropylene group such as —CH (CH ₃ ) CH ₂ CH ₂ — and —CH ₂ CH (CH ₃ ) CH ₂ —; —CH (CH ₃ ) CH _{2 CH 2 CH 2 -, - CH} 2 CH (CH 3) CH 2 CH 2 - , etc. Rukirubuchiren group, alkyl alkylene group such as and the like. The alkyl group in the alkyl alkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.
The chain aliphatic hydrocarbon group may have a substituent. Examples of the substituent include a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, and an oxygen atom (= O).

As the aliphatic hydrocarbon group containing a ring in the structure, a cyclic aliphatic hydrocarbon group (a group obtained by removing two hydrogen atoms from an aliphatic hydrocarbon ring), the cyclic aliphatic hydrocarbon group is the above-mentioned Examples thereof include a group bonded to the terminal of a chain aliphatic hydrocarbon group or interposed in the middle of a chain aliphatic hydrocarbon group.
The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably 3 to 12 carbon atoms.
The cyclic aliphatic hydrocarbon group may be a monocyclic group or a polycyclic group.
The monocyclic group is preferably a group in which two hydrogen atoms are removed from a C 3-6 monocycloalkane. Specific examples of the monocycloalkane include cyclopentane and cyclohexane.
As the polycyclic group, a group in which two hydrogen atoms are removed from a polycycloalkane having 7 to 12 carbon atoms is preferable. Specific examples of the polycycloalkane include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
The cyclic aliphatic hydrocarbon group may have a substituent. Examples of the substituent include an alkyl group having 1 to 5 carbon atoms, a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, an oxygen atom (= O), and the like.

The aromatic hydrocarbon group includes, for example, one more aromatic hydrocarbon nucleus of a monovalent aromatic hydrocarbon group such as a phenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, an anthryl group, and a phenanthryl group. A divalent aromatic hydrocarbon group excluding a hydrogen atom; part of the carbon atoms constituting the ring of the divalent aromatic hydrocarbon group is substituted with a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom Aromatic hydrocarbon group: arylalkyl group such as benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, 2-naphthylethyl group, etc., and the aromatic hydrocarbon Aromatic hydrocarbon group in which one hydrogen atom is further removed from the nucleus of
The aromatic hydrocarbon group may have a substituent. Examples of the substituent include an alkyl group having 1 to 5 carbon atoms, a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, an oxygen atom (= O), and the like.

The divalent linking group represented by Q ⁰ may contain a divalent group containing a hetero atom. Specific examples of the divalent group include —O—, —C (═O) —, —C (═O) —O—, —O—C (═O) —O—, —NH—, — NR-, —NH—C (═O) —, ═N—, —S—, —S (═O) ₂ , —S (═O) ₂ —O— and the like can be mentioned. R is a substituent such as an alkyl group or an acyl group. The substituent preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 5 carbon atoms.

In the above formula (A-1), R ¹ represents an organic group which may have a fluorine atom.
The structure of the organic group may be linear, branched or cyclic, but is preferably linear or branched.
The organic group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, still more preferably 1 to 10 carbon atoms, and particularly preferably 1 to 5 carbon atoms.
From the viewpoint of improving water repellency, this organic group preferably has a fluorination rate of 25% or more, more preferably 50% or more, and further preferably 60% or more. The “fluorination rate” is the ratio (%) of (number of fluorine atoms) to (total number of hydrogen atoms and fluorine atoms) in the organic group.

R ¹ is preferably a methyl group, an ethyl group, or a fluorinated hydrocarbon group which may have a substituent.

Regarding the fluorinated hydrocarbon group which may have a substituent, the hydrocarbon group may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group, but may be an aliphatic hydrocarbon group. preferable. The aliphatic hydrocarbon group may be saturated or unsaturated, but is preferably saturated. That is, R ¹ is more preferably a fluorinated saturated hydrocarbon group or a fluorinated unsaturated hydrocarbon group, and further preferably a fluorinated saturated hydrocarbon group, that is, a fluorinated alkyl group.
Examples of the fluorinated alkyl group include groups in which some or all of the hydrogen atoms of the unsubstituted alkyl group described below are substituted with fluorine atoms.

The unsubstituted alkyl group may be linear, branched or cyclic, and may be a combination of a linear or branched alkyl group and a cyclic alkyl group.
The unsubstituted linear alkyl group preferably has 1 to 10 carbon atoms, and more preferably 1 to 8 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-nonyl group, and an n-decanyl group.
The unsubstituted branched alkyl group preferably has 3 to 10 carbon atoms, and preferably 3 to 8 carbon atoms. As the branched alkyl group, a tertiary alkyl group is preferable.
Examples of the unsubstituted cyclic alkyl group include groups in which one hydrogen atom has been removed from a monocycloalkane, or a polycycloalkane such as bicycloalkane, tricycloalkane, or tetracycloalkane. Specific examples include monocycloalkyl groups such as cyclopentyl group and cyclohexyl group; polycycloalkyl groups such as adamantyl group, norbornyl group, isobornyl group, tricyclodecanyl group, and tetracyclododecanyl group.
As the combination of an unsubstituted linear or branched alkyl group and a cyclic alkyl group, a group in which a cyclic alkyl group is bonded as a substituent to a linear or branched alkyl group, or a cyclic alkyl Examples include a group in which a linear or branched alkyl group is bonded as a substituent to the group.

  Examples of the substituent that the fluorinated hydrocarbon group may have include an alkyl group having 1 to 5 carbon atoms.

In R ¹ , the fluorinated alkyl group is preferably a linear or branched alkyl group. In particular, a group represented by the following formula (a-3) or formula (a-4) is preferable, and among them, a group represented by formula (a-3) is preferable.

In the above formula (a-3), R ¹² represents an unsubstituted alkylene group having 1 to 9 carbon atoms, and R ¹³ represents a fluorinated alkyl group having 1 to 9 carbon atoms. However, the total number of carbon atoms of R ¹² and R ¹³ is 10 or less. In the formula (a-4), R ^{14 to} R ¹⁶ each independently represent a linear alkyl group having 1 to 5 carbon atoms, and at least one of R ^{14 to} R ¹⁶ is an alkyl having a fluorine atom. It is a group.

In the above formula (a-3), the alkylene group for R ¹² may be linear, branched or cyclic, but is preferably linear or branched. Moreover, as for the carbon number, 1-5 are preferable. R ¹² is particularly preferably a methylene group, an ethylene group, or a propylene group.
In the above formula (a-3), R ¹³ is preferably a linear or branched fluorinated alkyl group having 1 to 5 carbon atoms, and particularly preferably a perfluoroalkyl group. Of _{these, -CF 3, -C 2 F 4} H, -C 2 F 5 are preferred.
In the above formula ^(a-4), the alkyl group of R 14 ^{to R 16,} preferably a methyl group or an ethyl group, more preferably a methyl group. Of the alkyl groups of R ^{14 to} R ¹⁶ , any one may be a fluorinated alkyl group, and all may be fluorinated alkyl groups.

In the above formula (A-1), n represents 0 or 1.
When n = 0, the monomer represented by the formula (A-1) is preferably ^{one in} which R ¹ is a methyl group or an ethyl group.
When n = 1, the monomer represented by the formula (A-1) is represented by the monomer represented by the following formula (A-1-1) or the formula (A-1-2) described later. Monomers are preferred.

-Monomer represented by formula (A-1-1)

In the formula (A-1-1), R ⁰ has the same meaning as the formula (A-1), Q ⁰¹ represents a divalent linking group having no fluorine atom, and R ¹¹ has a fluorine atom. An organic group is shown. Examples of Q ⁰¹ include those having no fluorine atom among Q ⁰ in formula (A-1). ^As the ^{R 11,} of ^{R 1} in the above formula (A-1), those having a fluorine atom.

  Among the monomers represented by the above formula (A-1-1), monomers represented by the following formulas (A-1-11) to (A-1-16) are preferable.

In the formulas (A-1-11) to (A-1-16), R ⁰ has the same meaning as the formula (A-1), and R ¹¹ has the same meaning as the formula (A-1-1). . R ⁵⁰ represents a substituent, R ⁵¹ and R ⁵² each independently represents an alkyl group having 1 to 10 carbon atoms, and R ⁵³ and R ⁵⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. Indicates. a1 to a3, a5 and a7 each independently represent an integer of 1 to 5, and a4, a6 and a8 each independently represent an integer of 0 to 5. d1 to d3 each independently represents 0 or 1, e represents an integer of 0 to 2, and A ¹ represents a cyclic alkylene group having 3 to 20 carbon atoms.

In the above formula (A-1-11), a1 is preferably an integer of 1 to 3, and more preferably 1 or 2.
In the formula (A-1-12), a2 and a3 are each independently preferably an integer of 1 to 3, and more preferably 1 or 2.
d1 is preferably 0.

In the above formula (A-1-13), a4 is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and even more preferably 1 or 2.
a5 is preferably an integer of 1 to 3, and more preferably 1 or 2.
Examples of the substituent for R ⁵⁰ include a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a halogenated alkyl group having 1 to 5 carbon atoms, and an oxygen atom (= O). Can be mentioned. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
e is preferably 0 or 1, and particularly preferably 0 from an industrial viewpoint.
d2 is preferably 0.

In the above formula (A-1-14), a6 is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and even more preferably 0 or 1.
a7 is preferably an integer of 1 to 3, and more preferably 1 or 2.
d3 is preferably 0.
R ⁵⁰ and e are as defined in the above formula (A-1-13).

In the formula (A-1-15), a8 is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and still more preferably 0 or 1.
R ⁵¹ and R ⁵² are preferably each independently a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms. Specifically, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, tert-pentyl, cyclopentyl, cyclohexyl, norbornyl, isobornyl, tri A cyclodecanyl group, an adamantyl group, a tetracyclododecanyl group, etc. are mentioned. The alkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably a methyl group or an ethyl group.
R ⁵³ and R ⁵⁴ are preferably each independently a hydrogen atom, or a linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms. The linear, branched, or cyclic alkyl group having 1 to 10 carbon atoms in R ⁵³ and R ⁵⁴ is the same as R ⁵¹ and R ⁵² described above.

In Formula (A-1-16), A ¹ is preferably a cyclic alkylene group having 3 to 12 carbon atoms.
The cyclic alkylene group may be either a monocyclic group or a polycyclic group.
The monocyclic group is preferably a group in which two hydrogen atoms are removed from a C 3-6 monocycloalkane. Specific examples of the monocycloalkane include cyclopentane and cyclohexane.
As the polycyclic group, a group in which two hydrogen atoms are removed from a polycycloalkane having 7 to 12 carbon atoms is preferable. Specific examples of the polycycloalkane include adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
The cyclic alkylene group may have a substituent. Examples of the substituent include an alkyl group having 1 to 5 carbon atoms, a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, an oxygen atom (= O), and the like.

Hereinafter, specific examples of the monomers represented by the formulas (A-1-11) to (A-1-16) will be shown. R ⁰ has the same ^{meaning as} in the above formula (A-1).

  The monomer represented by the formula (A-1-1) is preferably at least one selected from monomers represented by the formulas (A-1-11) to (A-1-16). At least one selected from monomers represented by formulas (A-1-11) to (A-1-14) is more preferable, and in the above formulas (A-1-11) to (A-1-13) At least one selected from the monomers represented is more preferred, and a monomer represented by the above formula (A-1-11) is particularly preferred.

-Monomer represented by Formula (A-1-2)

In the above formula (A-1-2), R ⁰ and R ¹ have the same meaning as in the above formula (A-1), and Q ⁰² represents a divalent linking group having a fluorine atom. Examples of Q ⁰² include those having a fluorine atom among Q ⁰ in formula (A-1).

  Among the monomers represented by the above formula (A-1-2), preferable examples include monomers represented by the following formulas (A-1-21) and (A-1-22).

In the formulas (A-1-21) and (A-1-22), R ⁰ has the same meaning as the formula (A-1).
R ⁶⁰ and R ⁶¹ each independently represent a hydrogen atom, an alkyl group, or a fluorinated alkyl group, and may be bonded to each other to form a ring.

The alkyl group in R ⁶⁰ and R ⁶¹ may be linear, branched or cyclic, but is preferably linear or branched.
In the case of a linear or branched alkyl group, the number of carbon atoms is preferably 1 to 5, more preferably a methyl group or an ethyl group, and particularly preferably an ethyl group.
In the case of a cyclic alkyl group, the number of carbon atoms is preferably 4-15, more preferably 4-12, and even more preferably 5-10. Specific examples include groups in which one hydrogen atom has been removed from a monocycloalkane or a polycycloalkane such as a bicycloalkane, tricycloalkane, or tetracycloalkane. More specifically, monocycloalkyl groups such as cyclopentyl group and cyclohexyl group; polycycloalkyl groups such as adamantyl group, norbornyl group, isobornyl group, tricyclodecanyl group and tetracyclododecanyl group; Of these, an adamantyl group is preferred.

The fluorinated alkyl group for R ⁶⁰ and R ⁶¹ is a group in which part or all of the hydrogen atoms in the above alkyl group are substituted with fluorine atoms.

R ⁶⁰ and R ⁶¹ may be bonded to each other to form a ring. Examples of such a ring include those obtained by removing two hydrogen atoms from the monocycloalkane or polycycloalkane. This ring is preferably a 4- to 10-membered ring, more preferably a 5- to 7-membered ring.

Among the above, R ⁶⁰ and R ⁶¹ are preferably a hydrogen atom or an alkyl group.

The formula (A-1-21), shows the (A-1-22) ^{in, R 62} is a fluorine atom or a fluorinated alkyl group.
In the fluorinated alkyl group for R ⁶² , the alkyl group not substituted with a fluorine atom may be linear, branched or cyclic.
In the case of a linear or branched alkyl group, the number of carbon atoms is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1 or 2.
In the fluorinated alkyl group, from the viewpoint of improving water repellency, the fluorination rate is preferably 30 to 100%, and more preferably 50 to 100%.

In the formula (A-1-21), R ¹⁷ represents an organic group having a fluorine atom, and examples of R ¹ in the formula (A-1) include those having a fluorine atom.
R ¹⁷ is preferably a fluorinated hydrocarbon group, more preferably a fluorinated alkyl group. Specifically, a fluorinated alkyl group having 1 to 5 carbon atoms is more preferable, and —CH ₂ —CF ₃ , —CH ₂ —CF ₂ —CF ₃ , —CH (CF ₃ ) ₂ , —CH ₂ —CF _{2 are used.} —CF ₂ —CF ₃ is particularly preferred, and —CH ₂ —CF ₃ is most preferred.

In the above formula (A-1-22), R ¹⁸ represents an alkyl group.
The alkyl group for R ¹⁸ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 5 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. preferable.

Hereinafter, specific examples of monomers represented by the above formulas (A-1-21) and (A-1-22) are shown. R ⁰ has the same ^{meaning as} in the above formula (A-1).

  The monomer represented by the above formula (A-1) may be used alone or in combination of two or more.

  The proportion of the structural unit derived from the monomer represented by the formula (A-1) is preferably 5 to 70 mol%, more preferably 10 to 50 mol%, and further preferably 15 to 25 mol% in the alkali-soluble polymer. preferable. By being in the said range, the water repellency and alkali solubility of the protective film formed can be made compatible.

[Structural Unit Derived from Monomer Represented by Formula (A-2)]
The alkali-soluble polymer preferably has a structural unit derived from a monomer represented by the following formula (A-2). When the alkali-soluble polymer has such a structural unit, the alkali solubility of the protective film to be formed can be improved.

In said formula (A-2), ^R0 is synonymous with said formula (A-1).
Q ¹ represents a divalent linking group which may have a fluorine atom. Examples of Q ¹ include the same groups as Q ⁰ in formula (A-1).

In the above formula (A-2), R ² and R ³ are each independently an alkyl group having 1 to 15 carbon atoms or a fluorinated alkyl group (however, the alkyl group or fluorinated alkyl group may have an ether bond interposed therebetween). In addition, a hydrogen atom or a part of the fluorine atom of the alkyl group or the fluorinated alkyl group may be substituted with a hydroxyl group), and at least one of R ² and R ³ represents a fluorinated alkyl group. Show.

The alkyl group having 1 to 15 carbon atoms in R ² and R ³ may be linear, branched or cyclic, but is preferably linear or branched.
Specific examples of the alkyl group include a linear alkyl group such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-decyl group, and an n-pentadecyl group; an isopropyl group, Branched alkyl groups such as isobutyl group and tert-butyl group; cyclic alkyl groups such as cyclopentyl group and cyclohexyl group; and the like.
Examples of the fluorinated alkyl group having 1 to 15 carbon atoms include groups in which part or all of the hydrogen atoms of the alkyl group having 1 to 15 carbon atoms are substituted with fluorine atoms.
In addition, it is preferable that at least one of R ² and R ³ is a fluorinated alkyl group, and both R ² and R ³ are fluorinated alkyl groups.

  Preferable monomers among the monomers represented by the above formula (A-2) include monomers represented by the following formulas (A-2-1) and (A-2-2).

In the above formulas (A-2-1) and (A-2-2), R ⁰¹ , R ⁰² , Z, m are synonymous with the above formulas (a-1) and (a-2). R ² and R ³ have the same meaning as in the above formula (A-2).
In the above formula ^{(A-2-1), R 70} is an alkylene group or from 1 to 10 carbon atoms shows a fluorinated alkylene group.
The alkylene group having 1 to 10 carbon atoms in R ⁷⁰ may be linear or branched. R ⁷⁰ is particularly preferably a methylene group, an ethylene group, an n-propylene group, or an isopropylene group.
Examples of the fluorinated alkyl group having 1 to 10 carbon atoms include groups in which some or all of the hydrogen atoms of the alkyl group having 1 to 10 carbon atoms have been substituted with fluorine atoms.

In said formula (A-2-2), ^R71 shows a C1-C10 alkylene group or a fluorinated alkylene group. Alkylene group or a fluorinated alkylene group include the same groups as the above R ^70. This alkyl group or fluorinated alkyl group may have an ether bond interposed.

  Among the monomers represented by the above formula (A-2-2), a monomer represented by the following formula (A-2-21) is preferable.

In the above formula ^{(A-2-21), R 02} , Z, m have the same meanings as in the above formula ^{(a-2), R 2} , R 3 are as defined in the above formula (A-2).
In the above formula ^(A-2-21), alkylene group or 1 to 6 carbon atoms R 72 ^{to R 74} each independently represents a fluorinated alkylene group. The total number of carbon atoms of R ^{72 to} R ⁷⁴ is preferably 2 to 10.
In the above formula (A-2-21), m is 0 or 1, and is preferably 0.

  As the monomer represented by the above formula (A-2), one type may be used alone, or two or more types may be used in combination.

  The proportion of the structural unit derived from the monomer represented by the formula (A-2) is preferably 30 to 95 mol%, more preferably 50 to 90 mol%, and even more preferably 75 to 85 mol% in the alkali-soluble polymer. preferable.

[Structural units derived from other monomers]
In addition to the structural units derived from the monomers represented by the above formulas (A-1) and (A-2), the alkali-soluble polymer includes structural units derived from monomers used in conventionally known alkali-soluble polymers. You may have in the range which does not affect the effect of invention. The proportion of structural units derived from such other monomers is preferably 30 mol% or less, more preferably 20 mol% or less in the alkali-soluble polymer. By setting it as such a ratio, the material for protective film formation can be adjusted to a desired characteristic, without impairing the effect of this invention.
Examples of the other monomer include monomers represented by the following formulas (A-3-1) to (A-3-3).

In the formulas (A-3-1) to (A-3-3), R ⁰ has the same meaning as the formula (A-1), R ⁸⁰ represents a single bond or an ester bond, and R ⁸¹ represents a single bond. Or an alkylene group or a fluoroalkylene group having 1 to 6 carbon atoms, and R ⁸² is a linear, branched, or cyclic alkyl group or fluoroalkyl group having 1 to 15 carbon atoms (provided that one alkyl group) Part may be via an ether bond, and a part of the hydrogen atom or fluorine atom of the alkyl group or fluoroalkyl group may be substituted with a hydroxyl group.

  The alkali-soluble polymer described above may be used as a single polymer or a mixture of a plurality of polymers. Moreover, in the range which does not inhibit the effect of this invention, it originates in the monomer represented by the alkali-soluble polymer which has a structural unit derived from the monomer represented by the said Formula (A-1), and the said Formula (A-1). You may mix and use the alkali-soluble polymer which does not have a structural unit.

  Such an alkali-soluble polymer can be synthesized by a known method. Moreover, the polystyrene conversion mass average molecular weight (Mw) by GPC (gel permeation chromatography) of this alkali-soluble polymer is not particularly limited, but is preferably 2000 to 80000, and preferably 3000 to 50000. Is more preferable, and it is more preferable that it is 3000-30000.

  The blending amount of the alkali-soluble polymer is preferably about 0.1 to 20% by mass, and more preferably 0.3 to 10% by mass with respect to the total amount of the protective film forming material.

<(B) Solvent>
The protective film-forming material according to the present invention preferably contains a solvent that dissolves the alkali-soluble polymer. Examples of the solvent include (b-1) alkyl alcohols, (b-2) fluorinated alkyl alcohols in which some or all of the hydrogen atoms are substituted with fluorine atoms, (b-3) ethers, (b -4) Fluorinated alkyl ethers and fluorinated alkyl esters in which part or all of the hydrogen atoms are substituted with fluorine atoms.

  The (b-1) alkyl alcohols preferably have 1 to 10 carbon atoms. Specific examples include ethanol, propanol, n-butanol, isobutanol, n-pentanol, 4-methyl-2-pentanol, and 2-octanol. Of these, isobutanol and 4-methyl-2-pentanol are preferable.

The (b-2) fluorinated alkyl alcohols in which some or all of the hydrogen atoms are substituted with fluorine atoms preferably have 4 to 12 carbon atoms. _{Specifically, C 4 F 9 CH 2 CH} 2 OH, is _C 3 F 7 _CH 2 OH preferable.

As the (b-3) ethers, alkyl ethers, monoalkyl ethers of polyhydric alcohols, terpene solvents having an ether bond, and the like can be used.
The alkyl ethers preferably have 2 to 10 carbon atoms, and more preferably 3 to 8 carbon atoms. Examples of such alkyl ethers include dimethyl ether, diethyl ether, methyl ethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, diamyl ether, diisoamyl ether and the like. Of these, diisopropyl ether, dibutyl ether, diamyl ether, and diisoamyl ether are preferable.
Examples of monoalkyl ethers of polyhydric alcohols include monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether of polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol. Of these, propylene glycol monobutyl ether is preferable.
Examples of the terpene solvent having an ether bond include 1,4-cineole, 1,8-cineole, and pinene oxide. Among these, 1,4-cineole and 1,8-cineole are preferable from the viewpoint of industrial availability.

  As the (b-4) fluorinated alkyl ethers and fluorinated alkyl esters in which some or all of the hydrogen atoms are substituted with fluorine atoms, those having 3 to 15 carbon atoms are preferably used.

In the fluorinated alkyl ethers, R ^A OR ^B (R ^A and R ^B each independently represents an alkyl group, the total number of carbon atoms of both alkyl groups is 3 to 15, and at least a part of the hydrogen atoms or All of them are substituted with fluorine atoms.) At least one selected from fluorinated alkyl ethers represented by the following formula can be used.

In the fluorinated alkyl esters, R ^A COOR ^B (R ^A and R ^B each independently represents an alkyl group, the total number of carbon atoms of both alkyl groups is 3 to 15, and at least a part of the hydrogen atoms or All of them are substituted by fluorine atoms.) At least one selected from fluorinated alkyl esters represented by the following formula can be used.

  Preferable examples of the fluorinated alkyl ether include compounds represented by the following formula (B-1). In addition, preferred examples of the fluorinated alkyl ester include compounds represented by the following formulas (B-2) and (B-3). However, it is not limited to these.

  These solvents can be used alone or in combination of two or more as required. Furthermore, it can be used in combination with a paraffinic solvent such as n-heptane and a fluorine solvent such as fluoro-2-butyltetrahydrofuran as long as the effects of the present invention are not impaired.

<(C) Crosslinking agent>
The material for forming a protective film according to the present invention may further contain a crosslinking agent as necessary. Examples of the crosslinking agent include a nitrogen-containing compound having an amino group in which a hydrogen atom is substituted with at least one substituent selected from a hydroxyalkyl group and an alkoxyalkyl group, and a hydrogen atom having a hydroxyalkyl group and an alkoxyalkyl group. At least one nitrogen-containing compound selected from among nitrogen-containing compounds having an imino group substituted with at least one substituent selected from among them can be used.

  Examples of these nitrogen-containing compounds include melamine derivatives, urea derivatives, guanamine derivatives, acetoguanamine derivatives, benzoguanamine derivatives, succinyl, in which a hydrogen atom of an amino group is substituted with a methylol group and / or alkoxymethyl group. Examples thereof include amide derivatives, glycoluril derivatives in which a hydrogen atom of an imino group is substituted, and ethylene urea derivatives.

  These nitrogen-containing compounds are obtained by, for example, reacting the above-mentioned nitrogen-containing compounds with formalin in boiling water to form methylol, or further to this, lower alcohols, specifically methanol, ethanol, n-propanol, isopropanol, It can be obtained by reacting n-butanol, isobutanol or the like to be alkoxylated. Among them, a preferable crosslinking agent is tetrabutoxymethylated glycoluril.

  Furthermore, as a crosslinking agent, a condensation reaction product of a hydrocarbon compound substituted with at least one substituent selected from a hydroxyl group and an alkoxy group and a monohydroxymonocarboxylic acid compound can also be suitably used. As the monohydroxymonocarboxylic acid, those in which a hydroxyl group and a carboxyl group are bonded to the same carbon atom or two adjacent carbon atoms are preferable.

  When the crosslinking agent is blended, the blending amount is preferably about 0.5 to 10% by mass with respect to the blending amount of the alkali-soluble polymer.

<(D) acidic compound>
The protective film-forming material according to the present invention may further contain an acidic compound as necessary. When this acidic compound is added, the effect of improving the shape of the resist pattern can be obtained. Further, after immersion exposure, the resist film is exposed to an atmosphere containing a small amount of amine before development. Even in this case (reservation after exposure), adverse effects due to amines can be effectively suppressed by the interposition of the protective film. As a result, it is possible to prevent a large deviation in the dimensions of the resist pattern obtained by subsequent development.

  Examples of such an acidic compound include at least one selected from the following formulas (D-1), (D-2), (D-3), and (D-4).

In the above formulas (D-1), (D-2), (D-3), and (D-4), s represents an integer of 1 to 5, t represents an integer of 10 to 15, and u represents 2 Or v is independently 2 or 3, and R ^d1 is independently an alkyl group or fluorinated alkyl group having 1 to 15 carbon atoms (a hydrogen atom or a part of the fluorine atom is a hydroxyl group, an alkoxy group, Which may be substituted by a carboxyl group or an amino group).

  None of these acidic compounds are subject to the Important New Use Rules (SNUR) and have no adverse effects on the human body.

Specifically, as the acidic compound represented by the above formula (D-1), (C ₄ F ₉ SO ₂ ) ₂ NH, (C ₃ F ₇ SO ₂ ) ₂ NH, and the like are preferable. As the acidic compound represented by -2), specifically, C ₁₀ F ₂₁ COOH and the like are preferable.

  As the acidic compounds represented by the above formulas (D-3) and (D-4), specifically, compounds represented by the following formulas (D-5) and (D-6) are preferable, respectively. .

  When the acidic compound is blended, the blending amount is preferably about 0.1 to 10% by mass, and preferably about 0.1 to 3.0% by mass with respect to the total amount of the protective film forming material. Is more preferable.

<(E) Acid generation auxiliary agent that generates acid in the presence of acid>
The protective film-forming material according to the present invention may further contain an acid generation auxiliary as required. The acid generation auxiliary agent is an agent that does not have a function of generating an acid alone but generates an acid by the presence of the acid. As a result, even if the acid generated from the acid generator in the resist film diffuses into the protective film, the acid generated from the acid generating auxiliary agent in the protective film due to this acid may cause a shortage of acid in the resist film. Therefore, it is possible to compensate for the deterioration of the resolution of the resist pattern and the reduction of the depth of focus range, and it is possible to form a finer resist pattern.

  Such an acid generation aid is preferably an alicyclic hydrocarbon compound having both a carbonyl group and a sulfonyl group in the molecule.

  Specifically, such an acid generation auxiliary agent is preferably at least one selected from compounds represented by the following formulas (E-1) and (E-2).

In the above formulas (E-1) and (E-2), R ^e1 , R ^e2 , R ^e3 , and R ^e4 are each independently a hydrogen atom, or a straight or branched chain having 1 to 10 carbon atoms. X represents an alkyl group, and X represents an electrophilic group having a sulfonyl group.

  Here, examples of the “linear or branched alkyl group having 1 to 10 carbon atoms” include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert. -Butyl group, amyl group, isoamyl group, tert-amyl group, hexyl group, heptyl group, octyl group, isooctyl group, 2-ethylhexyl group, tert-octyl group, nonyl group, isononyl group, decyl group, isodecyl group, etc. A linear or branched saturated hydrocarbon group may be mentioned.

X is “electrophilic group having a sulfonyl group”. Here, the “electrophilic group having a sulfonyl group” is preferably —O—SO ₂ —Y. Y is a C1-C5 alkyl group or a C1-C10 halogenated alkyl group. Of these, Y is preferably a fluoroalkyl group.

  Specific examples of the compounds represented by the above formulas (E-1) and (E-2) include compounds represented by the following formulas (E-3) to (E-10).

  When mix | blending an acid generation adjuvant, it is preferable that the compounding quantity shall be 0.1-50 mass parts with respect to 100 mass parts of alkali-soluble polymers, and it is more preferable to set it as 1-20 mass parts. By setting it as such a range, it becomes possible to generate an acid effectively with respect to the acid eluted from a resist film, and to improve a resist pattern shape, without generating a coating nonuniformity.

<(F) Other>
The protective film-forming material according to the present invention may further contain a surfactant as necessary. Examples of the surfactant include “XR-104” (trade name: manufactured by Dainippon Ink & Chemicals, Inc.), but are not limited thereto. By blending such a surfactant, the coating properties and the ability to suppress the eluate can be further improved.

  When the surfactant is blended, the blending amount is preferably 0.001 to 10 parts by mass with respect to 100 parts by mass of the alkali-soluble polymer.

(Contact angle of protective film against water)
The water repellency of the protective film obtained using the material for forming a protective film according to the present invention is a contact angle with water, for example, a static contact angle (an angle formed between a water droplet surface on a horizontal resist film and the resist film surface). , Dynamic contact angle (Contact angle when water drops start to fall when the resist film is tilted. Contact angle (advance angle) at the front end point of the water drop direction, Contact angle at the end point behind the drop direction) (Fallback angle)), fall angle (inclination angle of the resist film when the water droplet starts to fall when the resist film is tilted), dynamic receding contact angle (resist film horizontally, etc.) It can be evaluated by measuring the contact angle at the end point behind the direction of movement of the water droplet when moving fast. For example, the higher the water repellency of the protective film, the larger the static contact angle, advancing angle, receding angle, and dynamic receding contact angle, while the falling angle becomes smaller.

  The dynamic contact angle and the static contact angle are DROP MASTER-700 (product name, manufactured by Kyowa Interface Science Co., Ltd.), AUTO SLIDING ANGLE: SA-30DM (product name, Kyowa) for the protective film formed under desired conditions. It can be measured by using a commercially available measuring apparatus such as Interface Science Co., Ltd., AUTO DISPENSER: AD-31 (product name, manufactured by Kyowa Interface Science Co., Ltd.). The dynamic receding contact angle can be measured by using a dynamic receding contact angle measuring device.

  The measured value of the advance angle of the protective film before the exposure and development is preferably 100 degrees or less, more preferably 70 to 100 degrees, and further preferably 80 to 95 degrees. When the advancing angle is 100 degrees or less, it is possible to suppress bubble entrainment that occurs when scanning is performed at high speed during exposure and causes defects in the resist pattern after development, and lithography characteristics and the like are good. .

  The measured value of the receding angle of the surface of the protective film before exposure and development is preferably 60 degrees or more, more preferably 60 to 150 degrees, still more preferably 70 to 130 degrees, 70 It is particularly preferable that the angle is -100 degrees. If the receding angle is equal to or greater than the lower limit, the lens followability of the liquid for immersion exposure is improved, and residual liquid droplets on the substrate for liquid immersion exposure liquid are reduced even when scanning is performed at high speed during exposure. In addition, the substance elution suppression effect at the time of immersion exposure is improved. Further, when the receding angle is not more than the upper limit value, the lithography characteristics are good.

  The measured value of the falling angle of the protective film before exposure and development is preferably 30 degrees or less, more preferably 0.1 to 30 degrees, and further preferably 0.1 to 20 degrees. Preferably, it is 0.1 to 10 degrees. When the falling angle is less than or equal to the upper limit value, the substance elution suppression effect during immersion exposure is improved. Further, when the sliding angle is at least the lower limit value, the lithography properties and the like are good.

  The measured value of the static contact angle of the protective film before exposure and development is preferably 70 degrees or more, more preferably 70 to 100 degrees, and further preferably 75 to 100 degrees. When the static contact angle is 70 degrees or more, the substance elution suppression effect from the protective film during immersion exposure is improved.

  The measured value of the dynamic receding contact angle of the protective film before exposure and development is preferably 60 degrees or more, more preferably 60 to 90 degrees, and particularly preferably 65 to 90 degrees. . When the dynamic receding contact angle is 60 degrees or more, the lithography characteristics are good.

  The above-mentioned various angles (static contact angle, dynamic contact angle (advance angle, receding angle), drop angle, dynamic receding contact angle) are determined according to the composition of the protective film forming material, for example, the alkali-soluble polymer. Adjustment by adjusting the type and content of the structural unit derived from the monomer represented by the formula (A-1), the type and content of the monomer to be copolymerized with the monomer represented by the formula (A-1) it can.

≪Resist pattern formation method≫
The resist pattern forming method according to the present invention includes a step of providing a resist film on a substrate, a step of forming a protective film on the resist film using the protective film forming material according to the present invention, and at least a protective film of the substrate A liquid for immersion exposure is disposed on the resist film, a step of selectively exposing the resist film via the liquid for immersion exposure and the protective film, and a resist after the exposure by removing the protective film with a developer. A developing step for developing the film.

  First, a resist film is provided on the substrate. Specifically, a known resist composition is applied to a substrate such as a silicon wafer by using a known method such as a spinner, and then prebaked (PAB treatment) to form a resist film. Note that the resist film may be formed after an organic or inorganic antireflection film (lower antireflection film) is provided on the substrate.

The resist composition is not particularly limited, and any resist composition that can be developed with an alkaline aqueous solution, including negative and positive resist compositions, can be used.
As such a resist composition, (i) a positive resist composition containing a naphthoquinone diazide compound and a novolac resin, (ii) an acid generator that generates an acid upon exposure, and a solubility in an alkaline aqueous solution that is decomposed by an acid. A positive resist composition containing an increasing compound and an alkali-soluble resin; (iii) an acid generator that generates an acid upon exposure; and an alkali-soluble resin having a group that decomposes by acid and increases solubility in an aqueous alkali solution And (iv) a negative resist composition containing an acid generator that generates an acid upon exposure, a crosslinking agent, and an alkali-soluble resin. However, the present invention is not limited to these. Absent.

  Next, a protective film is formed on the resist film using the protective film forming material according to the present invention. Specifically, the protective film is formed by uniformly applying the protective film-forming material according to the present invention to the surface of the resist film by the same method as described above, and baking and curing.

Next, an immersion exposure liquid is disposed on at least the protective film of the substrate. The immersion exposure liquid is not particularly limited as long as it is a liquid having a refractive index larger than that of air and smaller than that of a resist film to be used. Examples of such immersion exposure liquids include water (pure water, deionized water), fluorine-based inert liquids, etc., but immersion exposure liquids having high refractive index characteristics that are expected to be developed in the near future. Can also be used. Specific examples of the fluorine-based inert liquid include a fluorine-based compound such as C ₃ HCl ₂ F ₅ , C ₄ F ₉ OCH ₃ , C ₄ F ₉ OC ₂ H ₅ , and C ₅ H ₃ F ₇ as a main component. Liquid. Among these, from the viewpoints of cost, safety, environmental problems, and versatility, it is preferable to use water (pure water, deionized water), but exposure light having a wavelength of 157 nm (eg, F ₂ excimer laser). When using, it is preferable to use a fluorine-based solvent from the viewpoint of low exposure light absorption.

  Next, the resist film is selectively exposed through the immersion exposure liquid and the protective film. At this time, since the resist film is shielded from the immersion exposure liquid by the protective film, the resist film may be affected by the invasion of the immersion exposure liquid and suffer from alteration such as swelling, or conversely in the immersion exposure liquid. It is prevented that the optical characteristics such as the refractive index of the immersion exposure liquid itself are changed by elution of the components.

The wavelength used for exposure is not particularly limited, and is appropriately selected depending on the characteristics of the resist film. For example, it can be performed using radiation such as ArF excimer laser, KrF excimer laser, F ₂ excimer laser, extreme ultraviolet (EUV), vacuum ultraviolet (VUV), electron beam, X-ray, soft X-ray.

  In addition, it is preferable that the placement of the immersion exposure liquid on the protective film and the exposure of the resist film be performed simultaneously. That is, it is preferable that the exposure exposure liquid is continuously dropped from one nozzle onto the protective film while the exposure lens is scanned at a high speed, and at the same time, the exposure is preferably performed by suction from the other nozzle.

  When the exposure in the immersion state is completed, it is preferable to perform post-baking (PEB treatment) on the resist film while the protective film is stacked on the resist film.

  Next, the protective film is removed with an alkali developer, and the exposed resist film is developed. As the alkaline developer, a known developer can be appropriately selected and used. By this alkali development treatment, the protective film is dissolved and removed simultaneously with the soluble portion of the resist film.

  Finally, rinsing is performed using pure water or the like. In this rinsing, for example, water is dropped or sprayed on the surface of the substrate while rotating the substrate to wash away the developer on the substrate and the protective film component and resist composition dissolved by the developer. And by drying, the resist pattern by which the resist film was patterned in the shape according to the mask pattern is obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples.

<Example 1>
Using propylene glycol monobutyl ether as a solvent, the content of an alkali-soluble polymer (mass average molecular weight: 8900, dispersity: 1.8) represented by the following formula (X-1) is 1.6% by mass, The material for forming a protective film was prepared by dissolving each so that the content of the acidic compound represented by (Y-1) (GEM Co., Ltd., EF-N301) was 0.5% by mass.

  Next, an organic antireflection film composition “ARC-95” (trade name, manufactured by Brewer Science Co., Ltd.) was applied onto a 300 mm silicon wafer using a spinner and baked on a hot plate at 205 ° C. for 60 seconds. By drying, an organic antireflection film having a thickness of 90 nm was formed. A TArF-6a-554 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a resist composition containing an acrylic resin, is applied on the antireflection film and heated at 110 ° C. for 60 seconds to form a resist film having a thickness of 100 nm. Formed.

  On the resist film, the material for forming a protective film prepared above was applied using a spinner, and then heated at 90 ° C. for 60 seconds to form a protective film having a thickness of 35 nm.

50 μL of water was dropped on the surface of the protective film, and the static contact angle, the falling angle, the advancing angle, and the receding angle were measured using DROP MASTER-700 manufactured by Kyowa Interface Science Co., Ltd., and evaluated according to the following evaluation criteria. .
Static contact angle: ○ (70.0 degrees or more), × (less than 70.0 degrees)
Tumble angle: ◎ (less than 10.0 degrees), ◯ (10.0 degrees or more and 30.0 degrees or less), x (more than 30.0 degrees)
Advance angle: ○ (100.0 degrees or less), × (over 100.0 degrees)
Receding angle: ○ (60.0 degrees or more), × (less than 60.0 degrees)
Further, 50 μL of water is placed on the surface of the protective film, the silicon wafer on which the protective film is formed is moved horizontally at a constant speed, and the dynamic receding contact angle is measured using a dynamic receding contact angle measuring instrument. Evaluation was based on the evaluation criteria.
Dynamic receding contact angle: ◎ (65.0 degrees or more), ○ (60.0 degrees or more and less than 65.0 degrees), × (less than 60.0 degrees)
In this embodiment, the static contact angle, the falling angle, the advancing angle, the receding angle, and the dynamic receding contact angle may be collectively referred to as a contact angle.

  As a reference example, the surface of the resist laminate without the protective film, that is, the contact angle of the resist film surface was measured in the same manner as described above.

Furthermore, the substrate having a protective film was brought into contact with an aqueous 2.38 mass% tetramethylammonium hydroxide (TMAH) solution for 60 seconds, and the solubility in an alkali developer was evaluated. The evaluation was performed according to the following evaluation criteria by measuring the dissolution rate of the protective film by contact with an alkali developer.
Protective film dissolution rate: ◎ (20.0 mm / second or more), ○ (1.0 mm / second or more and less than 20.0 mm / second), × (less than 1.0 mm / second)
Table 1 shows the evaluation results and measured values of the contact angle and the protective film dissolution rate.

<Example 2>
Example except that the alkali-soluble polymer represented by the above formula (X-1) was changed to an alkali-soluble polymer represented by the following formula (X-2) (mass average molecular weight: 12600, dispersity: 2.0) In the same manner as in No. 1, a protective film forming material was prepared. Furthermore, the contact angle and the protective film dissolution rate were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 1>
Example except that the alkali-soluble polymer represented by the above formula (X-1) was changed to an alkali-soluble polymer represented by the following formula (X-3) (mass average molecular weight: 14900, dispersity: 1.7) In the same manner as in No. 1, a protective film forming material was prepared. Furthermore, the contact angle and the protective film dissolution rate were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

<Comparative example 2>
Example except that the alkali-soluble polymer represented by the above formula (X-1) was changed to an alkali-soluble polymer represented by the following formula (X-4) (mass average molecular weight: 8200, dispersity: 1.6) In the same manner as in No. 1, a protective film forming material was prepared. Furthermore, the contact angle and the protective film dissolution rate were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

＜実施例３＞
溶剤としてジイソアミルエーテルを用いて、下記式（Ｘ−５）で表されるアルカリ可溶性ポリマー（質量平均分子量：４６００、分散度：１．４）の含有量が２．４質量％、上記式（Ｙ−１）で表される酸性化合物（株式会社ジェムコ製、ＥＦ−Ｎ３０１）の含有量が０.７質量％となるようにそれぞれ溶解させて、保護膜形成用材料を調製した。さらに、実施例１と同様に接触角等及び保護膜溶解速度を測定し、評価した。結果を表１に示す。

<Example 3>
Using diisoamyl ether as a solvent, the content of an alkali-soluble polymer (mass average molecular weight: 4600, dispersity: 1.4) represented by the following formula (X-5) is 2.4% by mass, and the above formula ( Y-1) was dissolved so that the content of the acidic compound represented by Y-1) (manufactured by Gemco Co., Ltd., EF-N301) was 0.7% by mass to prepare a protective film forming material. Furthermore, the contact angle and the protective film dissolution rate were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

As can be seen from Table 1, Comparative Example 1 using a protective film-forming material containing an alkali-soluble polymer having no structural unit derived from the monomer represented by the formula (A-1) is a dynamic receding contact. While the corner was good, the protective film dissolution rate was poor. In addition, in order to improve the dissolution rate of the protective film in Comparative Example 1, Comparative Example 2 in which the constituent ratio of the alkali-soluble monomer in the alkali-soluble polymer was increased was good in the protective film dissolution rate, while the dynamic contact retreat The corner was bad. From this, it is understood that it is difficult to keep both the dynamic receding contact angle and the protective film dissolution rate good.
On the other hand, Examples 1-3 using the protective film-forming material containing an alkali-soluble polymer having a structural unit derived from the monomer represented by the formula (A-1) are Comparative Examples 1, 2 and In comparison, the dynamic receding contact angle and the protective film dissolution rate were both good. In particular, an example using a protective film-forming material containing an alkali-soluble polymer having a structural unit derived from a monomer in which R ⁰ is a group represented by formula (a-2) in formula (A-1) No. 3 had a very good dissolution rate of the protective film.

Claims (6)

A protective film forming material for forming a protective film laminated on a resist film,
The protective film formation material containing the alkali-soluble polymer which has a structural unit derived from the monomer represented by a following formula (A-1).

[Wherein, R ⁰ represents a group represented by the following formula (a-1) or (a-2), Q ⁰ represents a divalent linking group optionally having a fluorine atom, and R ¹ represents an organic group which may have a fluorine atom, and n represents 0 or 1.

(In the formula, R ⁰¹ represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group, R ⁰² represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a halogenated alkyl group, Z represents an alkylene group having 1 or 2 carbon atoms or an oxygen atom, and m represents an integer of 0 to 3)] The material for forming a protective film according to claim 1, wherein the monomer represented by the formula (A-1) is a monomer represented by the following formula (A-1-1) or formula (A-1-2).

[Wherein, R ⁰ has the same meaning as in formula (A-1), Q ⁰¹ represents a divalent linking group having no fluorine atom, and R ¹¹ represents an organic group having a fluorine atom. ]

[Wherein, R ⁰ and R ¹ have the same meanings as those in formula (A-1), and Q ⁰² represents a divalent linking group having a fluorine atom. ] The protective film-forming material according to claim 1 or 2, wherein R ¹ is a group represented by the following formula (a-3) or formula (a-4).

[Wherein, R ¹² represents an unsubstituted alkylene group having 1 to 9 carbon atoms, and R ¹³ represents a fluorinated alkyl group having 1 to 9 carbon atoms. However, the total number of carbon atoms of R ¹² and R ¹³ is 10 or less. R ^{14 to} R ¹⁶ each independently represent a linear alkyl group having 1 to 5 carbon atoms, and at least one of R ^{14 to} R ¹⁶ is an alkyl group having a fluorine atom. ] The protective film-forming material according to any one of claims 1 to 3, wherein the alkali-soluble polymer further has a structural unit derived from a monomer represented by the following formula (A-2).

[Wherein, R ⁰ has the same meaning as in the above formula (A-1), Q ¹ represents a divalent linking group optionally having a fluorine atom, and R ² and R ³ each independently represents the number of carbon atoms. 1 to 15 alkyl groups or fluorinated alkyl groups (however, the alkyl group or fluorinated alkyl group may have an ether bond interposed therebetween, and further, a hydrogen atom or a part of the fluorine atom of the alkyl group or fluorinated alkyl group) May be substituted with a hydroxyl group), and at least one of R ² and R ³ represents a fluorinated alkyl group. ]   The material for forming a protective film according to any one of claims 1 to 4, which is used in an immersion exposure process. A resist pattern forming method using an immersion exposure process,
Providing a resist film on the substrate;
Forming a protective film on the resist film using the protective film-forming material according to any one of claims 1 to 5;
Disposing an immersion exposure liquid on at least the protective film of the substrate and selectively exposing the resist film through the immersion exposure liquid and the protective film;
A developing step of developing the resist film after exposure by removing the protective film with a developer;
A resist pattern forming method comprising: