WO2024070672A1

WO2024070672A1 - Resist composition and method for forming resist pattern

Info

Publication number: WO2024070672A1
Application number: PCT/JP2023/033241
Authority: WO
Inventors: 誠藤村
Original assignee: 日本ゼオン株式会社
Priority date: 2022-09-30
Filing date: 2023-09-12
Publication date: 2024-04-04

Abstract

This resist composition contains a crosslinking agent that reacts with ionizing radiation or non-ionizing radiation having a wavelength of 300 nm or less, a solvent, a polymer A, and a polymer B, the surface free energy of the polymer A being greater than the surface energy of the polymer B, and the difference between the surface free energy of the polymer A and the surface free energy of the polymer B being 3 mJ/m2 or more.

Description

Resist composition and method for forming resist pattern

The present invention relates to a resist composition and a method for forming a resist pattern.

Traditionally, in fields such as semiconductor manufacturing, resist compositions containing polymers and solvents have been used to form fine patterns by irradiation with ionizing radiation such as electron beams and extreme ultraviolet (EUV) rays, or non-ionizing radiation including short-wavelength light such as ultraviolet rays.

In order to increase the sensitivity of the resulting resist and to increase the strength of the resulting resist pattern, attempts have been made to incorporate a crosslinking agent into the resist composition (see, for example, Patent Documents 1 to 4).

Japanese Patent Application Laid-Open No. 56-019044 Japanese Patent Application Laid-Open No. 56-088134 JP 2000-321791 A JP 2004-279694 A

Here, in recent years, resist compositions are required to have a wide tolerance for the amount of exposure in the exposure process, in other words, a wide exposure margin. In addition, resist patterns formed using the resist compositions are required to suppress the occurrence of top loss, that is, the height of a line pattern consisting of a portion not exposed in the exposure process (unexposed portion) being significantly reduced after the development process. Furthermore, when forming a resist pattern, it is required to suppress the occurrence of residues (hereinafter also referred to as "resist residues") that are unintentionally left in the space portion of the resist pattern.
However, the conventional resist compositions described above have room for further improvement in terms of achieving all of the following: an increase in exposure margin, suppression of the occurrence of top loss, and reduction in the amount of resist residue.

The present invention aims to provide a resist composition and a method for forming a resist pattern that can effectively achieve all of the following: expanding the exposure margin, suppressing the occurrence of top loss, and reducing the amount of resist residue.

The present inventors conducted extensive research with the aim of solving the above problems. As a result, they discovered that the above problems could be solved by blending a crosslinking agent that reacts with ionizing radiation or non-ionizing radiation with a wavelength of 300 nm or less and two specific types of polymers into a resist composition, and thus completed the present invention.

That is, an object of the present invention is to advantageously solve the above-mentioned problems, and the present invention provides: [1] a resist composition comprising a crosslinking agent that reacts with ionizing radiation or non-ionizing radiation having a wavelength of 300 nm or less, a solvent, a polymer A, and a polymer B, wherein the surface free energy of the polymer A is greater than the surface free energy of the polymer B, and the difference between the surface free energy of the polymer A and the surface free energy of the polymer B is 3 mJ/ ^m2 or more.
The above resist composition can effectively achieve all of the following: an increase in exposure margin, suppression of the occurrence of top loss, and a reduction in the amount of resist residue.
In this specification, the "surface free energy" can be measured by the method described in the examples of this specification.

[2] In the resist composition according to the above [1], when the content of the polymer A in the resist composition is A (parts by mass), the content of the polymer is B (parts by mass), and the content of the crosslinking agent is C (parts by mass), the resist composition satisfies the following relational formula (x):
A ≧ (B + C) ... (x)
It is preferable that the following conditions are satisfied: (In formula (x), B>0 and C>0.)
A resist composition that satisfies the above relational expression (x) can further reduce the amount of resist residue in the resist pattern.

[3] In the resist composition according to the above [1] or [2], at least one of the polymer A and the polymer B is preferably a main chain cleavage type.
If at least one of the polymer A and the polymer B is of the main chain cleavage type, a better effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue can be obtained.

[4] In the resist composition according to any one of the above [1] to [3], at least one of the polymer A and the polymer B is represented by the following formula (I):

[In formula (I), R ¹ is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group, or a halogenated alkyl group, R ² is an organic group having hydrogen atoms or 0 to 20 fluorine atoms, and R ³ and R ⁴ are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from each other.]
In this way, when the resist composition contains at least one of the polymer A having the monomer unit (I) or the polymer B having the monomer unit (I), a more favorable effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue can be obtained.

[5] In the resist composition according to any one of the above [1] to [4], the polymer A is represented by the following formula (II):

[In formula (II), L is a divalent linking group having a fluorine atom, Ar is an aromatic ring group which may have a substituent, ^R5 is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group or a halogenated alkyl group, and ^R6 and ^R7 are a hydrogen atom, a halogen atom, an unsubstituted alkyl group or an alkyl group substituted with a halogen atom, and may be the same or different from each other.] and a monomer unit (II) represented by the following formula (III):

and a monomer unit (III) represented by the following formula (III): (wherein R ⁸ , R ¹¹ , and R ¹² are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from each other; R ⁹ is hydrogen atoms, halogen atoms, carboxyl groups, halogenated carboxyl groups, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms; R ¹⁰ is hydrogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms; p and q are integers of 0 to 5, and p+q=5).
In this way, when the polymer A has the monomer unit (II) and the monomer unit (III), a better effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue can be obtained.

[6] In the resist composition according to any one of the above [1] to [5], the polymer B is represented by the following formula (IV):

[In formula (IV), R ¹³ is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group, or a halogenated alkyl group, R ¹⁴ is an organic group having hydrogen atoms or 0 to 20 fluorine atoms, and R ¹⁵ and R ¹⁶ are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from each other.] and the following formula (V):

[In formula (V), R ¹⁷ , R ²⁰ , and R ²¹ are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from each other, R ¹⁸ is hydrogen atoms, halogen atoms, carboxyl groups, halogenated carboxyl groups, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, R ¹⁹ is hydrogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, r and s are integers of 0 to 5, and r+s=5.], and copolymer B is preferably a copolymer having the monomer unit (V) represented by the following formula (V).
In this way, when the polymer B is a copolymer B having the monomer unit (IV) and the monomer unit (V), a better effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue can be obtained.

[7] In the resist composition according to any one of the above [1] to [6], it is preferable that the crosslinking agent has an unsaturated bond.
If a crosslinking agent has an unsaturated bond, it is possible to obtain a better effect of expanding the exposure margin, suppressing the occurrence of top loss, and reducing the amount of resist residue.

[8] In the resist composition according to the above [7], it is preferable that the crosslinking agent has from 1 to 10 unsaturated bonds.
If the crosslinking agent has 1 or more and 10 or less unsaturated bonds, it is possible to obtain a better effect of expanding the exposure margin, a better effect of suppressing the occurrence of top loss, and a better effect of reducing the amount of resist residue.

[9] In the resist composition according to the above [7] or [8], the unsaturated bond contained in the crosslinking agent is preferably an unsaturated bond contained in a vinyl group, a (meth)acrylate group, or an allyl group.
If the crosslinking agent has a functional group containing the specific unsaturated bond, it is possible to obtain a better effect of expanding the exposure margin, a better effect of suppressing the occurrence of top loss, and a better effect of reducing the amount of resist residue.

[10] In the resist composition according to any one of the above [1] to [9], the crosslinking agent is preferably contained in an amount of 1 part by mass or more and 50 parts by mass or less relative to a total of 100 parts by mass of the polymer A and the polymer B.
If the resist composition contains a crosslinking agent within the above range, it is possible to obtain an even better effect of expanding the exposure margin, suppressing the occurrence of top loss, and reducing the amount of resist residue.

The present invention also relates to [11] a method for forming a resist pattern, comprising: a resist film forming step of coating a substrate with a resist composition comprising a crosslinking agent that reacts with ionizing radiation or non-ionizing radiation having a wavelength of 300 nm or less, a solvent, a polymer A, and a polymer B to obtain a coating layer, and removing the solvent from the coating layer to form a resist film; and an exposure step of exposing the resist film formed in the resist film forming step to ionizing radiation or non-ionizing radiation having a wavelength of 300 nm or less as exposure light, thereby forming a latent image pattern while progressing a crosslinking reaction by the crosslinking agent.
According to the method for forming a resist pattern in which the crosslinking reaction by a crosslinking agent and the formation of a latent image pattern proceed in parallel in the exposure step, the exposure margin in the exposure step is wider, and in the obtained resist pattern, the occurrence of top loss is suppressed and the amount of resist residue can be reduced.

[12] The method for forming a resist pattern according to [11] above further comprises a developing step of developing the exposed resist film, and the developing is preferably carried out using an alcohol.
If the method further includes a step of developing the resist film with alcohol, the amount of resist residue can be further reduced.

The present invention provides a resist composition and a method for forming a resist pattern that can form a resist pattern with a wide exposure margin, suppressed top loss, and reduced amounts of resist residue.

Hereinafter, an embodiment of the present invention will be described in detail.
The resist composition and method for forming a resist pattern of the present invention are not particularly limited and can be suitably used, for example, when forming a resist pattern in the manufacturing process of a printed circuit board such as a build-up board, a semiconductor, a photomask, a mold, etc. The resist composition of the present invention can be suitably used in the method for forming a resist pattern of the present invention. Furthermore, the resist composition of the present invention can be suitably used as a positive resist composition.

(Resist Composition)
The resist composition of the present invention contains a crosslinking agent that reacts with ionizing radiation or non-ionizing radiation having a wavelength of 300 nm or less, a polymer A, a polymer B, and a solvent, and further contains known additives that can be blended into the resist composition. In the resist composition of the present invention, the surface free energy of the polymer A is greater than the surface free energy of the polymer B, and the difference between the surface free energy of the polymer A and the surface free energy of the polymer B is 3 mJ/ ^m2 or more. According to such a resist composition, the exposure margin of the formed resist film is wide, and the occurrence of top loss is suppressed in the obtained resist pattern, and the amount of resist residue is reduced. The reason why these effects are obtained is not clear, but it is presumed to be as follows.

By using a resist composition in which the surface free energy of polymer A is greater than the surface free energy of polymer B and the difference between the surface free energy of polymer A and the surface free energy of polymer B is 3 mJ/m ^or greater, polymer B, which has a smaller surface free energy, can be favorably unevenly distributed on the surface of the resist film.
In addition, a crosslinking agent having a property that can proceed with a crosslinking reaction triggered by ionizing radiation or non-ionizing radiation with a wavelength of 300 nm or less, i.e., radiation that can be used as exposure light in the exposure step, does not crosslink before the exposure step, but starts the crosslinking reaction by being given a trigger, i.e., exposure light, in the exposure step. On the other hand, in the exposure step, the formation of a latent image pattern proceeds by irradiating the resist film with exposure light. Specifically, when forming a latent image pattern, a difference in solubility in a solvent of the polymer constituting the resist film is formed between the exposed and non-exposed parts of the resist film. That is, as a result of the formation of a latent image pattern, a portion of the polymer that is relatively poorly soluble in a solvent (hereinafter, "poorly soluble portion A") and a portion of the polymer that is relatively easily soluble in a solvent (hereinafter, "easy-to-dissolve portion B") are generated. In the portion with a relatively small amount of exposure in the exposure step (i.e., the boundary portion between the exposed and non-exposed parts of the resist film), it may be difficult to generate a sufficient difference in solubility between the poorly soluble portion A and the easy-to-dissolve portion B. In this case, if the resist film contains the above-mentioned predetermined crosslinking agent in addition to the polymer, the poor solubility of the poorly soluble portion A can be increased by the reaction between the crosslinking agents themselves and the reaction between the crosslinking agent and the polymer constituting the poorly soluble portion A. This effectively promotes the formation of a difference in solubility between the poorly soluble portion A and the soluble portion B, even when the amount of exposure in the exposure step is relatively small.
Furthermore, as described above, it is believed that the synergistic effect of the favorable uneven distribution of the polymer on the surface of the resist film and the favorable promotion of the formation of a difference in solubility between the poorly soluble portion A and the easily soluble portion B by the crosslinking agent can effectively achieve all of the following: an increase in exposure margin, suppression of the occurrence of top loss, and reduction in the amount of resist residue.

Here, the difference between the surface free energy of polymer A and the surface free energy of polymer B (i.e., "surface free energy of polymer A" - "surface free energy of polymer B") must be 3 mJ / m ² or more as described above, preferably 4 mJ / m ² or more, more preferably 5.5 mJ / m ² or more, even more preferably 6 mJ / m ² or more, particularly preferably 6.5 mJ / m ² or more, preferably 12 mJ / m ² or less, more preferably 11 mJ / m ² or less, and even more preferably 10 mJ / m ² or less. If the difference between the surface free energy of polymer A and the surface free energy of polymer B is within the above range, the occurrence of top loss can be further suppressed, and the amount of resist residue can be further reduced.

<Crosslinking Agent>
As the crosslinking agent, a crosslinking agent that reacts with ionizing radiation or non-ionizing radiation having a wavelength of 300 nm or less is used. More specifically, as the crosslinking agent, a crosslinking agent that can be used is one that, when a film made of the crosslinking agent is irradiated with a predetermined radiation to be crosslinked and then immersed for 1 minute in a solvent capable of dissolving the crosslinking agent, reduces the film thickness by less than 50% based on the film thickness before immersion.

In addition to satisfying the essential attribute of proceeding with a crosslinking reaction triggered by irradiation with ionizing radiation or non-ionizing radiation with a wavelength of 300 nm or less, it is preferable that the crosslinking agent has the property of not proceeding with a crosslinking reaction during a drying process (which usually involves heating) for removing the solvent when forming a resist film.

In order to obtain a better effect of expanding the exposure margin, suppressing the occurrence of top loss, and reducing the amount of resist residue, it is preferable to use a compound having an unsaturated bond, more specifically a carbon-carbon unsaturated bond, in its molecular structure as the crosslinking agent. Furthermore, in order to further enhance each of the above effects, the number of unsaturated bonds contained in the molecular structure of the crosslinking agent is preferably 1 or more, more preferably 2 or more, and is preferably 10 or less, and more preferably 8 or less.

Furthermore, it is preferable that the unsaturated bond possessed by the crosslinking agent is an unsaturated bond contained in a vinyl group, a (meth)acrylate group, or an allyl group. By blending a crosslinking agent having a functional group containing such a specific unsaturated bond, it is possible to obtain an even better effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue. The crosslinking agent may have only one of a vinyl group, a (meth)acrylate group, and an allyl group, or may have a plurality of groups. The number of these functional groups that the crosslinking agent may contain is preferably 1 or more, more preferably 2 or more, and is preferably 10 or less, and more preferably 8 or less.

Cross-linking agents that can be used include, but are not limited to, compounds having a vinyl group, compounds having an allyl group, acrylate compounds, methacrylate compounds, and isocyanurate compounds.

The above-mentioned compounds having a vinyl group and compounds having an allyl group include, for example, alkene compounds such as ethylene, propene, 1-butene, 2-butene, iso-butene, 1-pentene, 1-hexene, and 1-octene; cyano group-containing unsaturated hydrocarbon compounds such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-cyanoethylacrylonitrile; monovinyl ether compounds such as vinyl ethyl ether, vinyl butyl ether, vinyl phenyl ether, vinyl 2-chloroethyl ether, 3,4-dihydro-2H-pyran, 2,3-dihydrofuran, 1,4-dioxene, ethylene glycol monovinyl ether, diethylene glycol monovinyl ether, and isopropenyl methyl ether; divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, and polyethylene glycol divinyl ether. divinyl ether compounds having an aliphatic skeleton such as propylene glycol divinyl ether, dipropylene glycol divinyl ether, tripropylene glycol divinyl ether, polypropylene glycol divinyl ether, butanediol divinyl ether, neopentyl glycol divinyl ether, hexanediol divinyl ether, nonanediol divinyl ether, trimethylolpropane divinyl ether, ethylene oxide-added trimethylolpropane divinyl ether, pentaerythritol divinyl ether, and ethylene oxide-added pentaerythritol divinyl ether; trivinyl ether compounds having an aliphatic skeleton such as trimethylolpropane trivinyl ether and ethylene oxide-added trimethylolpropane trivinyl ether; pentaerythritol tetravinyl ether, ethylene oxide-added pentaerythritol tetravinyl ether, and ditrimethylolpropane tetravinyl ether. polyfunctional vinyl ether compounds having an aliphatic skeleton such as tetravinyl ether compounds having an aliphatic skeleton such as dipentaerythritol hexavinyl ether; polyfunctional vinyl ether compounds having an alicyclic skeleton such as 1,4-cyclohexanediol divinyl ether and 1,4-cyclohexanedimethanol divinyl ether; polyfunctional vinyl ether compounds having an aromatic skeleton such as hydroquinone divinyl ether; vinyl ester compounds such as vinyl acetate, vinyl butyrate, isopropenyl acetate, vinyl caprate, and vinyl benzoate; unsaturated alcohols such as allyl alcohol and cinnamic alcohol; conjugated diene compounds such as 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 1,3-cycloheptadiene, 1,3-cyclooctadiene, 2,5-dimethyl-2,4-hexadiene, and chloroprene; styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4,6-trimethylstyrene, 2,5-dimethyl-2,4-hexadiene, and 2,5-dimethyl-2,4-hexadiene; Aromatic vinyl compounds such as styrene, 4-butylstyrene, 4-phenylstyrene, 4-fluorostyrene, 2,3,4,5,6-pentafluorostyrene, 4-chlorostyrene, 4-bromostyrene, 4-iodostyrene, 4-hydroxystyrene, 4-aminostyrene, 4-carboxystyrene, 4-acetoxystyrene, 4-cyanomethylstyrene, 4-chloromethylstyrene, 4-methoxystyrene, 4-nitrostyrene, sodium 4-styrenesulfonate, 4-styrenesulfonic acid chloride, 4-vinylphenylboronic acid, α-methylstyrene, trans-β-methylstyrene, 2-methyl-1-phenylpropene, 1-phenyl-1-cyclohexene, β-bromostyrene, sodium β-styrenesulfonate, 2-vinylpyridine, 4-vinylpyridine, 2-iso-propenylnaphthalene, and 1-vinylimidazole; allylbenzene, triallyl cyanurate, diallyl phthalate, and triallyl isocyanurate.

Examples of the acrylate compound include monofunctional acrylate compounds, difunctional acrylate compounds, and trifunctional or higher polyfunctional acrylate compounds.

Examples of monofunctional acrylate compounds include alkyl acrylates such as acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, tert-pentyl acrylate, neopentyl acrylate, hexyl acrylate, octyl acrylate, dodecyl acrylate, and stearyl acrylate, benzyl acrylate, and alkoxy acrylate. butylphenol (butylphenol, octylphenol, nonylphenol, dodecylphenol, etc.), acrylates of ethylene oxide adducts, isobornyl acrylate, cyclohexyl acrylate, tricyclodecane monomethylol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, hydroxypentyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate , 2-hydroxy-3-butoxypropyl acrylate, 2-hydroxy-3-methoxypropyl acrylate, diethylene glycol monoacrylate, diethylene glycol monoethyl ether acrylate, triethylene glycol monoacrylate, triethylene glycol monoethyl ether acrylate, tetraethylene glycol monoacrylate, tetraethylene glycol monoethyl ether acrylate, polyethylene glycol monoacrylate, polyethylene glycol monoethyl ether acrylate, dipropylene glycol monoacrylate, polypropylene glycol monoacrylate, glycerin monoacrylate, acryloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, 2-acryloyloxypropyl phthalate, β-carboxyethyl acrylate, acrylic acid dimer, ω-carboxy-polycaprolactone monoacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, N-vinylpyrrolidone, N-vinylformamide, acryloylmorpholine, and the like.

Bifunctional acrylate compounds include ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, butylene glycol diacrylate, pentyl glycol diacrylate, neopentyl glycol diacrylate, hydroxypivalyl hydroxypivalate diacrylate, hydroxypivalyl hydroxypivalate dicaprolactonate diacrylate, 1,6-hexanediol diacrylate, 1,2-hexanedi diacrylate, 1,5-hexanediol diacrylate, 2,5-hexanediol diacrylate, 1,7-heptanediol diacrylate, 1,8-octanediol diacrylate, 1,2-octanediol diacrylate, 1,9-nonanediol diacrylate, 1,2-decanediol diacrylate, 1,10-decanediol diacrylate, 1,12-dodecanediol diacrylate, 1,2-dodecanediol diacrylate, 1,14-tetradecanediol diacrylate, 1,2-tetradecanediol diacrylate, 1,16-hexadecanediol diacrylate, 1,2-hexadecanediol diacrylate, 2-methyl-2,4-pentanediol diacrylate, 3-methyl-1,5 -pentanediol diacrylate, 2-methyl-2-propyl-1,3-propanediol diacrylate, 2,4-dimethyl-2,4-pentanediol diacrylate, 2,2-diethyl-1,3-propanediol diacrylate, 2,2,4-trimethyl-1,3-pentanediol diacrylate, dimethylol octane diacrylate, 2-ethyl-1,3-hexanediol diacrylate, 2,5-dimethyl-2,5-hexanediol diacrylate, 2-methyl-1,8-octanediol diacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, 2,4-diethyl-1,5-pentanediol diacrylate, 2,4-diethyl-1,5-pentanediol diacrylate tricyclodeca Examples of the dialkyl dimethylol diacrylate include tricyclodecane dimethylol dicaprolactonate diacrylate, bisphenol A tetraethylene oxide adduct diacrylate, bisphenol F tetraethylene oxide adduct diacrylate, bisphenol S tetraethylene oxide adduct diacrylate, water-added bisphenol A tetraethylene oxide adduct diacrylate, water-added bisphenol F tetraethylene oxide adduct diacrylate, water-added bisphenol A diacrylate, water-added bisphenol F diacrylate, bisphenol A tetraethylene oxide adduct dicaprolactonate diacrylate, and bisphenol F tetraethylene oxide adduct dicaprolactonate diacrylate.

Examples of polyfunctional acrylate compounds include glycerin triacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane tricaprolactonate triacrylate, trimethylolethane triacrylate, trimethylolhexane triacrylate, trimethyloloctane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol tetracaprolactonate tetraacrylate, diglycerin tetraacrylate, and ditrimethylolpropane tetraacrylate. acrylate, ditrimethylolpropane tetracaprolactonate tetraacrylate, ditrimethylolethane tetraacrylate, ditrimethylolbutane tetraacrylate, ditrimethylolhexane tetraacrylate, ditrimethyloloctane tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tripentaerythritol hexaacrylate, tripentaerythritol heptaacrylate, tripentaerythritol octaacrylate, and tripentaerythritol polyalkylene oxide heptaacrylate.
Other examples include polyfunctional acrylate compounds such as urethane acrylate and polyester acrylate.

Methacrylate compounds include, for example, monofunctional methacrylate compounds, difunctional methacrylate compounds, and trifunctional or higher polyfunctional methacrylate compounds.

Examples of monofunctional methacrylate compounds include methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, tert-pentyl methacrylate, neopentyl methacrylate, hexyl methacrylate, octyl methacrylate, dodecyl methacrylate, stearyl methacrylate and other alkyl methacrylates, benzyl methacrylate, and alkylphenols. (butylphenol, octylphenol, nonylphenol, dodecylphenol, etc.), methacrylates of ethylene oxide adducts, isobornyl methacrylate, cyclohexyl methacrylate, tricyclodecane monomethylol methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, hydroxypentyl methacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, 2-hydroxy-3-butoxypropyl methacrylate, acrylate, 2-hydroxy-3-methoxypropyl methacrylate, diethylene glycol monomethacrylate, diethylene glycol monoethyl ether methacrylate, triethylene glycol monomethacrylate, triethylene glycol monoethyl ether amethacrylate, tetraethylene glycol monomethacrylate, tetraethylene glycol monoethyl ether methacrylate, polyethylene glycol monomethacrylate, polyethylene glycol monoethyl ether methacrylate, dipropylene glycol monomethacrylate, dipropylene glycol monoethyl ether methacrylate, polypropylene glycol monomethacrylate, polypropylene glycol monoethyl ether methacrylate, glycerin monomethacrylate, acryloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, 2-acryloyloxypropyl phthalate, β-carboxyethyl methacrylate, acrylic acid dimer, ω-carboxy-polycaprolactone monomethacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, N-vinylpyrrolidone, N-vinylformamide, acryloylmorpholine, etc.

Bifunctional methacrylate compounds include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, butylene glycol dimethacrylate, pentyl glycol dimethacrylate, neopentyl glycol dimethacrylate, hydroxypivalyl hydroxypivalate dimethacrylate, hydroxypivalyl hydroxypivalate dicaprolactonate dimethacrylate, 1,6-hexanediol dimethacrylate, 1,2-hexanediol dimethacrylate, acrylate, 1,5-hexanediol dimethacrylate, 2,5-hexanediol dimethacrylate, 1,7-heptanediol dimethacrylate, 1,8-octanediol dimethacrylate, 1,2-octanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,2-decanediol dimethacrylate, 1,10-decanediol dimethacrylate, 1,12-dodecanediol dimethacrylate, 1,2-dodecanediol dimethacrylate, 1,14-tetradecanediol dimethacrylate, 1,2-tetradecanediol dimethacrylate, 1,16-hexadecanediol dimethacrylate, 1,2-hexadecanediol dimethacrylate, 2-methyl-2,4-pentanediol dimethacrylate, 3-methyl-1,5-pentanediol dimethacrylate, 2-Methyl-2-propyl-1,3-propanediol dimethacrylate, 2,4-dimethyl-2,4-pentanediol dimethacrylate, 2,2-diethyl-1,3-propanediol dimethacrylate, 2,2,4-trimethyl-1,3-pentanediol dimethacrylate, dimethylol octane dimethacrylate, 2-ethyl-1,3-hexanediol dimethacrylate, 2,5-dimethyl-2,5-hexanediol dimethacrylate, 2-methyl-1,8-octanediol dimethacrylate, 2-butyl-2-ethyl-1,3-propanediol dimethacrylate, 2,4-diethyl-1,5-pentanediol dimethacrylate, 1,2-decanediol dimethacrylate, 2-methyl-2,4-pentane dimethacrylate, 2,4-diethyl-1,5-pentanediol dimethacrylate Examples of the acrylate include tricyclodecane dimethylol dimethacrylate, tricyclodecane dimethylol dicaprolactonate dimethacrylate, bisphenol A tetraethylene oxide adduct dimethacrylate, bisphenol F tetraethylene oxide adduct dimethacrylate, bisphenol S tetraethylene oxide adduct dimethacrylate, water-added bisphenol A tetraethylene oxide adduct dimethacrylate, water-added bisphenol F tetraethylene oxide adduct dimethacrylate, water-added bisphenol A dimethacrylate, water-added bisphenol F dimethacrylate, bisphenol A tetraethylene oxide adduct dicaprolactonate dimethacrylate, and bisphenol F tetraethylene oxide adduct dicaprolactonate dimethacrylate.

Multifunctional methacrylate compounds include glycerin trimethacrylate, trimethylolpropane trimethacrylate, ethoxylated trimethylolpropane trimethacrylate, trimethylolpropane tricaprolactonate trimethacrylate, trimethylolethane trimethacrylate, trimethylolhexane trimethacrylate, trimethyloloctane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, pentaerythritol tetracaprolactonate tetramethacrylate, diglycerin tetramethacrylate, ditrimethylolpropane tetramethacrylate, acrylate, ditrimethylolpropane tetracaprolactonate tetramethacrylate, ditrimethylolethane tetramethacrylate, ditrimethylolbutane tetramethacrylate, ditrimethylolhexane tetramethacrylate, ditrimethyloloctane tetramethacrylate, dipentaerythritol pentamethacrylate, dipentaerythritol hexamethacrylate, tripentaerythritol hexamethacrylate, tripentaerythritol heptamethacrylate, tripentaerythritol octamethacrylate, tripentaerythritol polyalkylene oxide heptamethacrylate, etc. Other methacrylates such as urethane methacrylate and polyester methacrylate can also be used.

Furthermore, examples of isocyanurate compounds that can be used as crosslinking agents include polyfunctional (meth)acryloyl group-containing isocyanurates such as tri(acryloyloxyethyl)isocyanurate, tri(methacryloyloxyethyl)isocyanurate, alkylene oxide-added tri(acryloyloxyethyl)isocyanurate, and alkylene oxide-added tri(methacryloyloxyethyl)isocyanurate; and polyfunctional allyl group-containing isocyanurates such as triallyl isocyanurate.

Specific examples of crosslinking agents that can be suitably used herein include the following: polyethylene glycol diacrylate (manufactured by Toagosei Co., Ltd., product name: "Aronix (registered trademark) M-240"), trimethylolpropane PO-modified triacrylate (manufactured by Toagosei Co., Ltd., product name: "Aronix (registered trademark) M-321"), ethoxylated trimethylolpropane triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: "NK Ester A-TMPT-3EO"), trimethylolpropane triacrylate (manufactured by Toagosei Co., Ltd., product name: "Aronix (registered trademark) M-309"), triethylene glycol divinyl Examples of the isocyanuric acid modified ethylene oxide diacrylate and isocyanuric acid modified ethylene oxide triacrylate include aryl ether (manufactured by Nippon Carbide Industries Co., Ltd., product name "TEGDVE"), a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (manufactured by Toagosei Co., Ltd., product name "ARONIX (registered trademark) M-403"), a mixture of isocyanuric acid ethylene oxide modified diacrylate and isocyanuric acid ethylene oxide modified triacrylate (manufactured by Toagosei Co., Ltd., product name "ARONIX (registered trademark) M-315"), and triallyl isocyanurate (manufactured by Mitsubishi Chemical Corporation, product name "TAIC").
The crosslinking agent may be used alone or in combination of two or more kinds.

The content of the crosslinking agent is preferably 1 mass part or more, more preferably 2 mass parts or more, even more preferably 3 mass parts or more, particularly preferably 4 mass parts or more, preferably 50 mass parts or less, more preferably 35 mass parts or less, even more preferably 30 mass parts or less, particularly preferably 20 mass parts or less, relative to 100 mass parts of the total of polymer A and polymer B described below. If the content of the crosslinking agent is within the above range, a better effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue can be obtained. Furthermore, if the content of the crosslinking agent is within the above range, the obtained resist pattern can have a higher resolution.

The content of the crosslinking agent can be further optimized according to the functionality of the crosslinking agent. For example, when the crosslinking agent is bifunctional, the content of the crosslinking agent is preferably 5 parts by mass or more and 50 parts by mass or less, with the total of the polymer A and the polymer B being 100 parts by mass. When the crosslinking agent is trifunctional, the content of the crosslinking agent is preferably 4 parts by mass or more and 40 parts by mass or less, with respect to the total of the polymer A and the polymer B being 100 parts by mass. Furthermore, when the crosslinking agent is pentafunctional, the content of the crosslinking agent is preferably 3 parts by mass or more and 30 parts by mass or less, with respect to the total of the polymer A and the polymer B being 100 parts by mass. If the content of the crosslinking agent with a predetermined functionality is within the above range, a better effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue can be obtained. Furthermore, if the content of the crosslinking agent with a predetermined functionality is within the above range, the obtained resist pattern can be made high-resolution.

<Polymer A>
The polymer A contained in the resist composition of the present invention is not particularly limited as long as the surface free energy is 3 mJ / m ² or more higher than the surface energy of the polymer B. From the viewpoint of obtaining a good exposure margin expansion effect, a top loss occurrence suppression effect, and an effect of reducing the amount of resist residue, it is preferable that the polymer A is a main chain scission type polymer. In this specification, the term "main chain scission type" refers to a polymer in which the main chain is scissed and the molecular weight is reduced by irradiation of exposure light such as ionizing radiation such as an electron beam or non-ionizing radiation with a wavelength of 300 nm or less. Such a polymer is not particularly limited, and for example, those described in JP-B-8-3636, JP-A-2020-134683, WO 2019/150966, and WO 2020/066806 can be used.

From the viewpoint of obtaining a better effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue, the polymer A is preferably a compound represented by the following formula (I):

[In formula (I), R ¹ is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group, or a halogenated alkyl group, R ² is an organic group having hydrogen atoms or 0 to 20 fluorine atoms, and R ³ and R ⁴ are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from each other.]

[Monomer unit (I)]
Here, the monomer unit (I) is represented by the following formula (a):

(In the formula (a), R ¹ to R ⁴ are the same as those in the formula (I)).

Examples of halogen atoms which may constitute R ¹ , R ³ and R ⁴ in formula (I) and formula (a) include a chlorine atom, a fluorine atom, a bromine atom and an iodine atom.

Examples of the alkylsulfonyl group which may constitute R ¹ in formula (I) and formula (a) include a methylsulfonyl group, an ethylsulfonyl group, and the like.

Examples of the alkoxy group which may constitute R ¹ in formula (I) and formula (a) include a methoxy group, an ethoxy group, and a propoxy group.

Examples of the acyl group which may constitute R ¹ in formula (I) and formula (a) include a formyl group, an acetyl group, and a propionyl group.

Examples of the alkyl ester group which may constitute R ¹ in formula (I) and formula (a) include a methyl ester group, an ethyl ester group, and the like.

Examples of halogenated alkyl groups which may constitute R ¹ in formula (I) and formula (a) include halogenated methyl groups having 1 to 3 halogen atoms.

The organic group having 0 to 20 fluorine atoms that can constitute ^R2 in formula (I) and formula (a) may have an aromatic ring or may be chain-like. Here, chain-like includes straight chain and branched chain. Examples of such organic groups include fluoroalkyl groups, fluoroalkoxyalkyl groups, and fluoroalkoxyalkenyl groups such as fluoroethoxyvinyl groups.

Examples of the unsubstituted alkyl group which can constitute R ³ and R ⁴ in formula (I) and formula (a) include unsubstituted alkyl groups having 1 to 10 carbon atoms.

Examples of the alkyl group substituted with a halogen atom which may constitute ^R3 and ^R4 in formula (I) and formula (a) include groups having a structure in which some or all of the hydrogen atoms in an alkyl group are substituted with the above-mentioned halogen atoms.

Here, the monomer (a) is not particularly limited, and examples thereof include α-chloroacrylic acid fluoroesters such as 2,2,2-trifluoroethyl α-chloroacrylate, 2,2,3,3,3-pentafluoropropyl α-chloroacrylate, 3,3,4,4,4-pentafluorobutyl α-chloroacrylate, 1H-1-(trifluoromethyl)trifluoroethyl α-chloroacrylate, 1H,1H,3H-hexafluorobutyl α-chloroacrylate, 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl α-chloroacrylate, and 2,2,3,3,4,4,4-heptafluorobutyl α-chloroacrylate. alkyl esters; α-chloroacrylic acid fluoroalkoxyalkyl esters such as α-chloroacrylic acid pentafluoroethoxymethyl ester and α-chloroacrylic acid pentafluoroethoxyethyl ester; α-chloroacrylic acid fluoroalkoxyalkenyl esters such as α-chloroacrylic acid pentafluoroethoxyvinyl ester; α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl, α-chloroacrylic acid-1-phenyl-2,2,2-trifluoroethyl, α-chloroacrylic acid-1-phenyl-2,2,3,3,3-pentafluoropropyl, etc.

When polymer A has monomer unit (I), polymer A may have any monomer unit other than monomer unit (I).

From the viewpoint of obtaining a better effect of expanding the exposure margin, suppressing the occurrence of top loss, and reducing the amount of resist residue, it is preferable that the polymer A is a compound represented by the following formula (II):

[In formula (III), R ⁸ , R ¹¹ , and R ¹² are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from each other, R ⁹ is hydrogen atoms, halogen atoms, carboxyl groups, halogenated carboxyl groups, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, R ¹⁰ is hydrogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and p and q are integers of 0 to 5, and p+q=5.]

When copolymer A has monomer unit (II) and monomer unit (III), copolymer A may have any monomer unit other than monomer unit (II) and monomer unit (III), but the total proportion of monomer unit (II) and monomer unit (III) in all monomer units constituting copolymer A is preferably 90 mol% or more, and more preferably 100 mol% (i.e., copolymer A has only monomer unit (II) and monomer unit (III)).

The above-mentioned copolymer A may be, for example, a random copolymer, a block copolymer, an alternating copolymer, or the like, so long as it has the monomer unit (II) and the monomer unit (III), but is preferably an alternating copolymer. In this specification, an alternating copolymer is, for example, a copolymer in which the above-mentioned monomer unit (II) and monomer unit (III) are alternately bonded. In other words, when shown diagrammatically, the individual monomer units are bonded as "(II)-(III)-(II)-(III)-".

Since copolymer A contains monomer units (II) and (III), when it is irradiated with exposure light, the main chain is cut and the molecular weight is reduced.

[Monomer unit (II)]
Here, the monomer unit (II) is represented by the following formula (b):

In the formula (b), L, Ar, and R ⁵ to R ⁷ are the same as those in the formula (II).

Examples of divalent linking groups having fluorine atoms that may constitute L in formula (II) and formula (b) include divalent chain alkyl groups having 1 to 5 carbon atoms and having fluorine atoms.

The aromatic ring group which may have a substituent and which may constitute Ar in formula (II) and formula (b) includes an aromatic hydrocarbon ring group which may have a substituent, and an aromatic heterocyclic group which may have a substituent.

Aromatic hydrocarbon ring groups include, but are not limited to, a benzene ring group, a biphenyl ring group, a naphthalene ring group, an azulene ring group, an anthracene ring group, a phenanthrene ring group, a pyrene ring group, a chrysene ring group, a naphthacene ring group, a triphenylene ring group, an o-terphenyl ring group, an m-terphenyl ring group, a p-terphenyl ring group, an acenaphthene ring group, a coronene ring group, a fluorene ring group, a fluoranthene ring group, a pentacene ring group, a perylene ring group, a pentaphene ring group, a picene ring group, a pyranthrene ring group, and the like.

Aromatic heterocyclic groups include, but are not limited to, a furan ring group, a thiophene ring group, a pyridine ring group, a pyridazine ring group, a pyrimidine ring group, a pyrazine ring group, a triazine ring group, an oxadiazole ring group, a triazole ring group, an imidazole ring group, a pyrazole ring group, a thiazole ring group, an indole ring group, a benzimidazole ring group, a benzothiazole ring group, a benzoxazole ring group, a quinoxaline ring group, a quinazoline ring group, a phthalazine ring group, a benzofuran ring group, a dibenzofuran ring group, a benzothiophene ring group, a dibenzothiophene ring group, a carbazole ring group, and the like.

The substituents that Ar may have include, but are not limited to, alkyl groups, fluorine atoms, and fluoroalkyl groups. Examples of the alkyl groups that Ar may have as substituents include linear alkyl groups having 1 to 6 carbon atoms, such as methyl groups, ethyl groups, propyl groups, n-butyl groups, and isobutyl groups. Examples of the fluoroalkyl groups that Ar may have as substituents include fluoroalkyl groups having 1 to 5 carbon atoms, such as trifluoromethyl groups, trifluoroethyl groups, and pentafluoropropyl groups.

From the viewpoint of sufficiently improving the sensitivity to ionizing radiation, etc., Ar in formula (II) and formula (b) is preferably an aromatic hydrocarbon ring group which may have a substituent, more preferably an unsubstituted aromatic hydrocarbon ring group, and even more preferably a benzene ring group (phenyl group).

Examples of halogen atoms which may constitute ^R5 in formula (II) and formula (b) include the same atoms as the halogen atoms which may constitute ^R1 in formula (I) and formula (a).

Alkylsulfonyl groups which may constitute ^R5 in formula (II) and formula (b) include the same groups as the alkylsulfonyl groups which may constitute ^R1 in formula (I) and formula (a).

Alkoxy groups which may constitute ^R5 in formula (II) and formula (b) include the same groups as the alkoxy groups which may constitute ^R1 in formula (I) and formula (a).

Examples of acyl groups which may constitute ^R5 in formulae (II) and (b) include the same acyl groups as those which may constitute ^R1 in formulae (I) and (a).

Alkyl ester groups which may constitute ^R5 in formula (II) and formula (b) include the same groups as the alkyl ester groups which may constitute ^R1 in formula (I) and formula (a).

Examples of halogenated alkyl groups which may constitute ^R5 in formula (II) and formula (b) include the same groups as the halogenated alkyl groups which may constitute ^R1 in formula (I) and formula (a).

Examples of halogen atoms which may constitute R ⁶ and R ⁷ in formulae (II) and (b) include the same atoms as the halogen atoms which may constitute R ¹ in formulae (I) and (a).

The unsubstituted alkyl groups which may constitute ^R6 and ^R7 in formula (II) and formula (b) include the same groups as the unsubstituted alkyl groups which may constitute ^R3 and ^R4 in formula (I) and formula (a).

Examples of alkyl groups substituted with halogen atoms which may constitute ^R6 and ^R7 in formula (II) and formula (b) include the same groups as the alkyl groups substituted with halogen atoms which may constitute ^R3 and ^R4 in formula (I) and formula (a).

In order to sufficiently improve the sensitivity to ionizing radiation, etc., the monomer (b) represented by formula (b) is preferably α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) and α-chloroacrylic acid-1-(4-methoxyphenyl)-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPhOMe), and more preferably α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl. In other words, it is preferable for the copolymer A to have at least one of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and α-chloroacrylic acid-1-(4-methoxyphenyl)-1-trifluoromethyl-2,2,2-trifluoroethyl units, and more preferably α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units.

The proportion of monomer units (II) in copolymer A is not particularly limited, and can be, for example, 30 mol % or more and 70 mol % or less, assuming that the total monomer units in copolymer A are 100 mol %.

[Monomer unit (III)]
The monomer unit (III) is represented by the following formula (c):

In the formula (c), R ⁸ to R ¹² , p and q are the same as those in the formula (III).

Examples of halogen atoms that may constitute R ⁸ , R ¹¹ and R ¹² in formula (III) and formula (c) include the same atoms as the halogen atoms that may constitute R ¹ in formula (I) and formula (a).

Examples of the alkyl group that can constitute the unsubstituted alkyl group that can constitute ^R8 , ^R11 , and ^R12 in formula (III) and formula (c) include the same groups as the unsubstituted alkyl groups that can constitute ^R3 and ^R4 in formula (I) and formula (a). Among them, the unsubstituted alkyl group that can constitute ^R8 is preferably a methyl group or an ethyl group.

Examples of the alkyl group substituted with a halogen atom which may constitute ^R8 , ^R11 , and ^R12 in formula (III) and formula (c) include the same groups as the alkyl group substituted with a halogen atom which may constitute ^R3 and ^R4 in formula (I) and formula (a).

Examples of halogen atoms that may constitute ^R9 in formula (III) and formula (c) include the same atoms as the halogen atoms that may constitute ^R1 in formula (I) and formula (a). Among them, the halogen atom is preferably a fluorine atom.

Examples of halogenated carboxyl groups which may constitute R ⁹ in formula (III) and formula (c) include a chlorocarboxyl group (-C(=O)-Cl), a fluorinated carboxyl group (-C(=O)-F), a brominated carboxyl group (-C(=O)-Br), and the like.

Examples of the unsubstituted alkyl group that may constitute ^R9 in formula (III) and formula (c) include the same groups as the unsubstituted alkyl groups that may constitute ^R3 and ^R4 in formula (I) and formula (a).

Examples of the alkyl group substituted with a halogen atom which may constitute ^R9 in formula (III) and formula (c) include the same groups as the alkyl groups substituted with a halogen atom which may constitute ^R3 and ^R4 in formula (I) and formula (a).

Examples of the unsubstituted alkyl group which may constitute ^R10 in formula (III) and formula (c) include the same groups as the unsubstituted alkyl groups which may constitute ^R3 and ^R4 in formula (I) and formula (a).

Examples of the alkyl group substituted with a halogen atom which may constitute ^R10 in formula (III) and formula (c) include the same groups as the alkyl groups substituted with a halogen atom which may constitute ^R3 and ^R4 in formula (I) and formula (a).

In formula (III) and formula (c), when p is 2 or more, each R ⁹ may be the same as or different from each other. When q is 2 or more, each R ¹⁰ may be the same as or different from each other.

From the viewpoints of easiness in preparation of Copolymer A and improvement in severability of the main chain upon irradiation with ionizing radiation or the like, R ⁸ in formula (III) and formula (c) is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group.

In addition, from the viewpoint of facilitating the preparation of copolymer A and improving the severability of the main chain when irradiated with ionizing radiation or the like, it is preferable that p in formula (III) and formula (c) is 0 or 1.

Furthermore, when p in formula (III) and formula (c) is any one of 1 to 5, R ⁹ in formula (III) and formula (c) is preferably an alkyl group having 1 to 5 carbon atoms, and more preferably a methyl group.

The monomer (c) represented by formula (c) is not particularly limited, and examples thereof include α-methylstyrene (AMS) and its derivatives, such as the following monomers (c-1) to (c-12).

In addition, from the viewpoint of ease of preparation of copolymer A and improving the severability of the main chain when irradiated with ionizing radiation, etc., α-methylstyrene (c-1) is preferred as monomer (c). In other words, copolymer A preferably has α-methylstyrene units.

The proportion of monomer units (I) in copolymer A is not particularly limited, and can be 30 mol % or more and 70 mol % or less, assuming that the total monomer units in copolymer A are 100 mol %.

<Properties of Polymer A>
[Surface free energy]
The surface free energy of polymer A is preferably 28 mJ/ ^m2 or more, more preferably 29 mJ/ ^m2 or more, and even more preferably 30 mJ/ ^m2 or more, and is preferably 35 mJ/ ^m2 or less, more preferably 34 mJ/ ^m2 or less, and even more preferably 33 mJ/ ^m2 or less.
The surface free energy of the polymer A can be adjusted by the types and ratio of the monomer units constituting the polymer A.

[Weight average molecular weight]
The weight average molecular weight (Mw) of the polymer A is preferably 100,000 or more, more preferably 125,000 or more, preferably 150,000 or more, more preferably 600,000 or less, and more preferably 500,000 or less. If the weight average molecular weight of the polymer A is the above lower limit or more, the occurrence of top loss can be further suppressed, and a resist pattern with further improved contrast can be formed. In addition, if the weight average molecular weight of the polymer A is the above upper limit or less, the resist composition can be easily prepared.

[Number average molecular weight]
The number average molecular weight (Mn) of the polymer A is preferably 100,000 or more, more preferably 110,000 or more, and is preferably 300,000 or less, and more preferably 200,000 or less. If the number average molecular weight of the polymer A is equal to or more than the lower limit, the occurrence of top loss can be further suppressed, and a resist pattern with further improved contrast can be formed. If the number average molecular weight of the polymer A is equal to or less than the upper limit, the resist composition can be more easily prepared.

[Molecular weight distribution]
The molecular weight distribution of polymer A is preferably 1.20 or more, more preferably 1.25 or more, and even more preferably 1.30 or more, and is preferably 2.00 or less, more preferably 1.80 or less, and even more preferably 1.60 or less.
In this specification, the "molecular weight distribution" can be determined by calculating the ratio of the weight average molecular weight to the number average molecular weight (Mw/Mn). The "weight average molecular weight" and the "number average molecular weight" can be measured using gel permeation chromatography in terms of standard polystyrene.

[Method for preparing polymer A]
There is no particular limitation on the method for preparing the polymer A. Hereinafter, a method for preparing the copolymer A having the above-mentioned monomer unit (II) and monomer unit (III) as the polymer A will be specifically described, but the polymer A used in the resist composition of the present invention and the method for preparing the same are not limited to those shown below.

The copolymer A having the monomer unit (II) and the monomer unit (III) can be prepared by polymerizing a monomer composition containing the above-mentioned monomer (b), monomer (c), and any monomer copolymerizable with these monomers, and then recovering the obtained copolymer A and optionally purifying it.
The weight average molecular weight, number average molecular weight and molecular weight distribution of the copolymer A can be adjusted by changing the polymerization conditions and purification conditions. Specifically, for example, the weight average molecular weight and number average molecular weight can be increased by shortening the polymerization time. Furthermore, the molecular weight distribution can be narrowed by performing purification.

- Polymerization of monomer composition -
The monomer composition used in the preparation of copolymer A may be a mixture of monomer components including monomer (b) and monomer (c), an optional polymerization initiator, and an optional additive. The polymerization of the monomer composition may be carried out using a known method. Among them, it is preferable to use cyclopentanone, water, or the like as the solvent. It is also preferable to use, for example, azobisisobutyronitrile, or the like as the polymerization initiator.

The polymer obtained by polymerizing the monomer composition can be recovered by adding a good solvent such as tetrahydrofuran to a solution containing the polymer, without any particular limitations, and then dripping the solution with the good solvent into a poor solvent such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, or hexane to solidify the polymer.

- Purification of polymer -
The purification method used for purifying the obtained polymer is not particularly limited, and examples thereof include known purification methods such as reprecipitation and column chromatography. Among them, the reprecipitation method is preferably used as the purification method.
The purification of the polymer may be repeated several times.

The purification of the polymer by the reprecipitation method is preferably carried out, for example, by dissolving the obtained polymer in a good solvent such as tetrahydrofuran, and then dripping the obtained solution into a mixed solvent of a good solvent such as tetrahydrofuran and a poor solvent such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, hexane, etc., to precipitate a part of the polymer. In this way, by purifying by dripping a solution of the polymer into a mixed solvent of a good solvent and a poor solvent, the molecular weight distribution, number average molecular weight, and weight average molecular weight of the obtained copolymer A can be easily adjusted by changing the type and mixing ratio of the good solvent and poor solvent. Specifically, for example, the molecular weight of the copolymer A precipitated in the mixed solvent can be increased by increasing the proportion of the good solvent in the mixed solvent.

When purifying a polymer by the reprecipitation method, the polymer precipitated in a mixed solvent of a good solvent and a poor solvent may be used as copolymer A as long as it satisfies the desired properties, or the polymer that did not precipitate in the mixed solvent (i.e., the polymer that is dissolved in the mixed solvent) may be used. Here, the polymer that did not precipitate in the mixed solvent can be recovered from the mixed solvent using a known method such as concentration to dryness.

<Polymer B>
There are no particular limitations on polymer B contained in the resist composition of the present invention, so long as its surface free energy is at least 3 mJ/ ^m2 lower than the surface free energy of polymer A. From the viewpoint of obtaining a favorable effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue, polymer B is preferably a main chain cleavage type polymer.

From the viewpoint of obtaining a better effect of expanding the exposure margin, an effect of suppressing the occurrence of top loss, and an effect of reducing the amount of resist residue, the polymer B is preferably a polymer represented by the following formula (I):

[In formula (I), R ¹ is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group, or a halogenated alkyl group, R ² is an organic group having hydrogen atoms or 0 to 20 fluorine atoms, and R ³ and R ⁴ are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from each other.]
The monomer unit (I) that the polymer B may have is the same as the monomer unit (I) that the polymer A may have. In addition, the monomer that may form the monomer unit (I) that the polymer B may have is the same as the monomer (a) that is described above, and therefore the description thereof will be omitted here.

In addition, when polymer B has monomer unit (I), polymer B may have any monomer unit other than monomer unit (I).

From the viewpoint of obtaining a better effect of expanding the exposure margin, suppressing the occurrence of top loss, and reducing the amount of resist residue, it is preferable that the polymer B is a polymer represented by the following formula (IV):

[In formula (V), R ¹⁷ , R ²⁰ , and R ²¹ are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from each other, R ¹⁸ is hydrogen atoms, halogen atoms, carboxyl groups, halogenated carboxyl groups, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, R ¹⁹ is hydrogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, r and s are integers of 0 to 5, and r+s=5.].
In this specification, the monomer unit (IV) is different from the above-mentioned monomer unit (II), that is, the monomer unit (IV) does not include the monomer unit (II).

When copolymer B has monomer unit (IV) and monomer unit (V), copolymer B may have any monomer unit other than monomer unit (IV) and monomer unit (V), but the proportion of monomer unit (IV) and monomer unit (V) in the total monomer units constituting copolymer B is preferably 70 mol% or more, and more preferably 100 mol% (i.e., copolymer B has only monomer unit (IV) and monomer unit (V)). An example of an arbitrary monomer unit other than monomer unit (IV) and monomer unit (V) that copolymer B may have is the above-mentioned monomer unit (II).

The copolymer B may be, for example, a random copolymer, a block copolymer, an alternating copolymer, or a ternary alternating copolymer, as long as it has the monomer unit (IV) and the monomer unit (V), but is preferably an alternating copolymer or a ternary alternating copolymer. In this specification, a ternary alternating copolymer is, for example, an alternating copolymer having the above-mentioned monomer unit (II) in addition to the monomer unit (IV) and the monomer unit (V), in which the monomer unit (IV) or the monomer unit (V) is copolymerized between the monomer units (II). In other words, when shown diagrammatically, the individual monomer units are bonded as "-(II)-(IV)-(V)-(IV)-(II)".

Since copolymer B contains monomer units (IV) and (V), when it is irradiated with exposure light, the main chain is cut and the molecular weight is reduced.

[Monomer unit (IV)]
The monomer unit (IV) has the following formula (d):

In the formula (d), R ¹³ to R ¹⁶ are the same as R ¹³ to R ¹⁶ in the formula (IV).

Here, examples of halogen atoms that can constitute R ¹³ in formula (IV) and formula (d) include the same atoms as those that can constitute R ¹ in formula (I) and formula (a). Among them, the halogen atom that can constitute R ¹³ is preferably a chlorine atom.

Examples of the alkylsulfonyl group which may constitute R ¹³ in formula (IV) and formula (d) include the same groups as the alkylsulfonyl groups which may constitute R ¹ in formula (I) and formula (a).

Examples of alkoxy groups which may constitute R ¹³ in formulae (IV) and (d) include the same alkoxy groups as those which may constitute R ¹ in formulae (I) and (a).

Examples of acyl groups which may constitute R ¹³ in formulae (IV) and (d) include the same acyl groups as those which may constitute R ¹ in formulae (I) and (a).

Examples of alkyl ester groups which may constitute R ¹³ in formula (IV) and formula (d) include the same alkyl ester groups as may constitute R ¹ in formula (I) and formula (a).

Examples of halogenated alkyl groups which may constitute R ¹³ in formula (IV) and formula (d) include the same groups as the halogenated alkyl groups which may constitute R ¹ in formula (I) and formula (a).

The organic group having 0 to 20 fluorine atoms that can constitute R ¹⁴ in formula (IV) and formula (d) can be exemplified by the same groups as the organic group having 0 to 20 fluorine atoms that can constitute R ² in formula (I) and formula (a), but preferably does not have an aromatic ring, and more preferably is chain-like. The carbon number of R ¹⁴ is preferably 2 to 10, more preferably 5 or less. If the carbon number of R ¹⁴ is the above lower limit or more, the solubility in the developer can be sufficiently improved. In addition, if the carbon number of R ¹⁴ is the above upper limit or less, the clarity of the resist pattern can be sufficiently guaranteed.

Specifically, R ¹⁴ in formula (IV) and formula (d) is preferably a fluoroalkyl group, a fluoroalkoxyalkyl group, or a fluoroalkoxyalkenyl group, and more preferably a fluoroalkyl group. When R ¹⁴ is the above-mentioned group, the scission property of the main chain of polymer B when irradiated with ionizing radiation or the like can be sufficiently improved.

Examples of the fluoroalkyl group include a 2,2,3,3,3-pentafluoropropyl group (having 5 fluorine atoms and 3 carbon atoms), a 3,3,4,4,4-pentafluorobutyl group (having 5 fluorine atoms and 4 carbon atoms), a 1H-1-(trifluoromethyl)trifluoroethyl group (having 6 fluorine atoms and 3 carbon atoms), a 1H,1H,3H-hexafluorobutyl group (having 6 fluorine atoms and 4 carbon atoms), a 2,2,3,3,4,4,4-heptafluorobutyl group (having 7 fluorine atoms and 4 carbon atoms), and a 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl group (having 7 fluorine atoms and 3 carbon atoms). Among these, a 2,2,3,3,3-pentafluoropropyl group (having 5 fluorine atoms and 3 carbon atoms) or a 2,2,3,3,4,4,4-heptafluorobutyl group (having 7 fluorine atoms and 4 carbon atoms) is preferred, and a 2,2,3,3,3-pentafluoropropyl group (having 5 fluorine atoms and 3 carbon atoms) is more preferred.
Examples of the fluoroalkoxyalkyl group include a fluoroethoxymethyl group and a fluoroethoxyethyl group.
Furthermore, examples of the fluoroalkoxyalkenyl group include a fluoroethoxyvinyl group.

Examples of halogen atoms which may constitute R ¹⁵ and R ¹⁶ in formulae (IV) and (d) include the same atoms as the halogen atoms which may constitute R ¹ in formulae (I) and (a).

Examples of the unsubstituted alkyl groups which may constitute R ¹⁵ and R ¹⁶ in formula (IV) and formula (d) include the same groups as the unsubstituted alkyl groups which may constitute R ³ and R ⁴ in formula (I) and formula (a).

Examples of the alkyl group substituted with a halogen atom which may constitute R ¹⁵ and R ¹⁶ in formula (IV) and formula (d) include the same groups as the alkyl group substituted with a halogen atom which may constitute R ³ and R ⁴ in formula (I) and formula (a).

Examples of the monomer (d) include α-chloroacrylic acid fluoroalkyl esters such as α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl, α-chloroacrylic acid 3,3,4,4,4-pentafluorobutyl, α-chloroacrylic acid 1H-1-(trifluoromethyl)trifluoroethyl, α-chloroacrylic acid 1H,1H,3H-hexafluorobutyl, α-chloroacrylic acid 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl, and α-chloroacrylic acid 2,2,3,3,4,4,4-heptafluorobutyl; α-chloroacrylic acid fluoroalkoxyalkyl esters such as α-chloroacrylic acid pentafluoroethoxymethyl ester and α-chloroacrylic acid pentafluoroethoxyethyl ester; and α-chloroacrylic acid fluoroalkoxyalkenyl esters such as α-chloroacrylic acid pentafluoroethoxyvinyl ester.

Among these, α-chloroacrylic acid fluoroalkyl esters are preferred from the viewpoint of improving sensitivity to ionizing radiation, etc.

The proportion of monomer units (IV) in copolymer B is not particularly limited, and can be, for example, 30 mol % or more and 70 mol % or less, assuming that the total monomer units in copolymer B are 100 mol %.

[Monomer unit (V)]
The monomer unit (V) has the following formula (e):

In the formula (e), R ¹⁷ to R ²¹ , r and s are the same as those in the formula (V).

Examples of halogen atoms which may constitute R ¹⁷ , R ²⁰ and R ²¹ in formula (V) and formula (e) include the same atoms as the halogen atoms which may constitute R ¹ in formula (I) and formula (a).

Examples of the unsubstituted alkyl group which may constitute ^R17 , ^R20 , and ^R21 in formula (V) and formula (e) include the same groups as the unsubstituted alkyl groups which may constitute ^R3 and R4 in formula (I) and formula (a). Among them, the unsubstituted alkyl group which may constitute ^R17 in formula (V) and formula (e) is preferably a methyl group or an ethyl group.

Examples of the alkyl group substituted with a halogen atom which may constitute R ¹⁷ , R ²⁰ , and R ²¹ in formula (V) and formula (e) include the same groups as the alkyl group substituted with a halogen atom which may constitute R ³ and R ⁴ in formula (I) and formula (a).

Examples of halogen atoms which may constitute R ¹⁸ in formula (V) and formula (e) include the same atoms as the halogen atoms which may constitute R ¹ in formula (I) and formula (a).

Examples of halogenated carboxyl groups which may constitute R ¹⁸ in formula (V) and formula (e) include the same groups as the halogenated carboxyl groups which may constitute R ⁹ in formula (III) and formula (c).

Examples of the unsubstituted alkyl group which may constitute ^R18 in formula (V) and formula (e) include the same groups as the unsubstituted alkyl groups which may constitute ^R3 and ^R4 in formula (I) and formula (a).

Examples of the alkyl group substituted with a halogen atom which may constitute ^R18 in formula (V) and formula (e) include the same groups as the alkyl groups substituted with a halogen atom which may constitute ^R3 and ^R4 in formula (I) and formula (a).

Examples of the unsubstituted alkyl group which may constitute ^R19 in formula (V) and formula (e) include the same groups as the unsubstituted alkyl groups which may constitute ^R3 and ^R4 in formula (I) and formula (a).

Examples of the alkyl group substituted with a halogen atom which may constitute ^R19 in formula (V) and formula (e) include the same groups as the alkyl groups substituted with a halogen atom which may constitute ^R3 and ^R4 in formula (I) and formula (a).

In formula (V) and formula (e), when r is 2 or more, each R ¹⁸ may be the same as or different from each other. When s is 2 or more, each R ¹⁹ may be the same as or different from each other.

From the viewpoint of improving the ease of preparation of copolymer B, in formula (V) and formula (e), R ¹⁸ and/or R ¹⁹ are all preferably a hydrogen atom or an unsubstituted alkyl group, more preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms, and further preferably a hydrogen atom.

The monomer (e) represented by formula (e) is not particularly limited, and examples thereof include the following monomers (e-1) to (e-11) such as α-methylstyrene (AMS) and its derivatives (e.g., 4-fluoro-α-methylstyrene: 4FAMS).

In addition, from the viewpoint of ease of preparation of copolymer B and improving the severability of the main chain when irradiated with ionizing radiation or the like, α-methylstyrene (e-1) or 4-fluoro-α-methylstyrene (e-2) is preferred as monomer (e), and α-methylstyrene is more preferred. In other words, polymer B preferably has α-methylstyrene units or 4-fluoro-α-methylstyrene units.

The proportion of monomer units (V) in copolymer B is not particularly limited, and can be, for example, 30 mol% to 70 mol% or less, assuming that the total monomer units in copolymer B are 100 mol%.

<Properties of Polymer B>
[Surface free energy]
The surface free energy of polymer B is preferably 18 mJ/ ^m2 or more, more preferably 19 mJ/m2 or ^more , and even more preferably 20 mJ/m2 or ^more , and is preferably 27 mJ/ ^m2 or less, more preferably 26 mJ/ ^m2 or less, and even more preferably 25 mJ/ ^m2 or less.
The surface free energy of the polymer B can be adjusted by the types and ratio of the monomer units constituting the polymer B.

[Weight average molecular weight]
The weight average molecular weight (Mw) of the polymer B is preferably 10000 or more, more preferably 17000 or more, even more preferably 25000 or more, and preferably 250000 or less, more preferably 180000 or less, and even more preferably 50000 or less. If the weight average molecular weight of the copolymer B is the above lower limit or more, it is possible to suppress the solubility of the resist film in the developer from excessively increasing at a low irradiation dose. In addition, if the weight average molecular weight of the polymer B is the above upper limit or less, it is possible to easily prepare a resist composition.

[Number average molecular weight]
The number average molecular weight (Mn) of polymer B is preferably 7000 or more, more preferably 10000 or more, and preferably 150000 or less. When the number average molecular weight of polymer B is the above lower limit or more, it is possible to further suppress excessive increase in the solubility of the resist film in the developer at a low irradiation dose. In addition, when the number average molecular weight of polymer B is the above upper limit or less, it is possible to more easily prepare the resist composition.

[Molecular weight distribution]
The molecular weight distribution (Mw/Mn) of polymer B is preferably 1.10 or more, more preferably 1.20 or more, and preferably 1.70 or less, and more preferably 1.65 or less. When the molecular weight distribution of polymer B is the above lower limit or more, polymer B can be easily prepared. When the molecular weight distribution of polymer B is the above upper limit or less, the contrast of the obtained resist pattern can be further increased.

[Proportion of Polymer B]
The content of polymer B in the resist composition is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 49% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, when the total of polymer A and polymer B contained in the resist composition is taken as 100% by mass. If the content of polymer B in the resist composition is the above lower limit or more, the sensitivity to ionizing radiation and the like can be improved. Furthermore, if the content of polymer B in the resist composition is the above upper limit or less, the effect of reducing the amount of resist residue is further enhanced.

[Method for preparing polymer B]
There is no particular limitation on the method for preparing the polymer B. Hereinafter, a method for preparing the copolymer B having the above-mentioned monomer unit (IV) and monomer unit (V) as the polymer B will be specifically described, but the polymer B used in the resist composition of the present invention and the method for preparing the same are not limited to those shown below.

The copolymer B having the monomer unit (IV) and the monomer unit (V) can be prepared by polymerizing a monomer composition containing the above-mentioned monomer (d), monomer (e), and any monomer copolymerizable with these monomers, and then recovering the resulting copolymer and optionally purifying it. Here, the polymerization method and purification method are not particularly limited, and can be the same as the method described in the above section "Method of preparing polymer A."

<Solvent>
The solvent used in the resist composition of the present invention is not particularly limited as long as it is a solvent capable of dissolving the above-mentioned polymer A and polymer B, and any known solvent can be used. Among them, from the viewpoint of improving the coatability of the resist composition, it is preferable to use anisole, propylene glycol monomethyl ether acetate (PGMEA), cyclopentanone, cyclohexanone, or isoamyl acetate as the solvent. The solvent may be used alone or in combination of two or more kinds.

<Other ingredients>
In addition to the above-mentioned essential components, the resist composition of the present invention may further contain any known additives that can be blended into resist compositions. The amount of additives blended is not particularly limited, and an appropriate amount can be added depending on the application.

[Ratio of Polymer A, Polymer B and Crosslinking Agent]
There are no particular limitations on the total proportion of polymer A and polymer B in the resist composition. However, when the content of polymer A in the resist composition is A (parts by mass), the content of polymer B is B (parts by mass), and the content of crosslinking agent is C (parts by mass), the resist composition can satisfy the following relationship (x):
A ≧ (B + C) ... (x)
(However, in formula (x), B>0 and C>0.)
A resist composition that satisfies the above relational expression (x) can achieve an even better effect of expanding the exposure margin, suppressing the occurrence of top loss, and reducing the amount of resist residue.

<Preparation of Resist Composition>
The resist composition can be prepared by mixing the above-mentioned predetermined crosslinking agent, polymer A, polymer B, a solvent, and additives that can be added optionally. The mixing method is not particularly limited, and the components may be mixed by a known method. The resist composition may also be prepared by mixing each component and then filtering the mixture.

[Filtration]
Here, the method of filtering the mixture is not particularly limited, and for example, the mixture can be filtered using a filter. The filter is not particularly limited, and examples thereof include fluorocarbon, cellulose, nylon, polyester, and hydrocarbon filtration membranes. Among them, from the viewpoint of effectively preventing impurities such as metals from metal piping, etc., which may be used when preparing the polymer A and the polymer B, from being mixed into the resist composition, the material constituting the filter is preferably polyfluorocarbon such as polyethylene, polypropylene, polytetrafluoroethylene, Teflon (registered trademark), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), nylon, and a composite membrane of polyethylene and nylon. For example, the filter disclosed in U.S. Pat. No. 6,103,122 may be used. In addition, the filter may be commercially available as Zeta Plus (registered trademark) 40Q manufactured by CUNO Incorporated. Furthermore, the filter may contain a strong cationic or weak cationic ion exchange resin.
Here, the average particle size of the ion exchange resin is not particularly limited, but is preferably 2 μm or more and 10 μm or less. Examples of the cation exchange resin include sulfonated phenol-formaldehyde condensates, sulfonated phenol-benzaldehyde condensates, sulfonated styrene-divinylbenzene copolymers, sulfonated methacrylic acid-divinylbenzene copolymers, and other types of sulfonic acid or carboxylic acid group-containing polymers. The cation exchange resin is provided with H ⁺ counterions, NH ₄ ⁺ counterions, or alkali metal counterions, such as K ⁺ and Na ⁺ counterions. The cation exchange resin preferably has a hydrogen counterion. Examples of such cation exchange resins include Microlite® PrCH from Purolite, which is a sulfonated styrene-divinylbenzene copolymer having an H ⁺ counterion. Such cation exchange resins are commercially available as AMBERLYST® from Rohm and Haas.

The pore size of the filter is preferably 0.001 μm or more and 1 μm or less. If the pore size of the filter is within the above range, it is possible to sufficiently prevent impurities such as metals from being mixed into the resist composition.

(Method of forming a resist pattern)
The method for forming a resist pattern of the present invention includes a resist film forming step of coating a substrate with a resist composition containing a crosslinking agent that reacts with ionizing radiation or nonionizing radiation having a wavelength of 300 nm or less, a solvent, a polymer A, and a polymer B to obtain a coating layer, and removing the solvent from the coating layer to form a resist film, and an exposure step of exposing the resist film formed in the resist film forming step to ionizing radiation or nonionizing radiation having a wavelength of 300 nm or less as exposure light to form a latent image pattern while promoting a crosslinking reaction by the crosslinking agent. Furthermore, the method for forming a resist pattern of the present invention may further include a step of developing the latent image pattern obtained in the exposure step (developing step), a step of heating the resist film between the exposure step and the development step (post-exposure bake step), and/or a step of washing and removing the developer after the development step (rinsing step). Each step will be described below.

(Resist film forming process)
The resist film forming process includes a step (coating step) of applying a specific resist composition onto a workpiece, such as a substrate, to be processed using the resist pattern to obtain a coating layer, and then a step (drying step) of removing the solvent from the obtained coating layer to form a resist film.

<Coating process>
The workpiece to which the predetermined resist composition is applied in the coating step is not particularly limited, and examples of the workpiece include a semiconductor substrate used in the manufacture of semiconductor devices, a substrate having an insulating layer and a copper foil provided on the insulating layer, and a mask blank having a light-shielding layer formed on a substrate, which are used in the manufacture of printed circuit boards, etc. The method for applying the resist composition is not particularly limited, and any known method can be used.
As the predetermined resist composition to be applied onto the workpiece, the above-mentioned resist composition of the present invention can be suitably used.

<Drying process>
The method for removing the solvent from the coating layer is not particularly limited, and any drying method commonly used in forming a resist film can be used. However, it is preferable to form a resist film by heating (pre-baking) the resist composition.
Here, the temperature at which the coating layer is dried (drying temperature) is preferably 100° C. or higher, more preferably 110° C. or higher, from the viewpoint of adhesion between the resist film formed through the drying process and the workpiece, and is preferably 250° C. or lower, more preferably 200° C. or lower, from the viewpoint of reducing the thermal influence on the workpiece and the resist film. The time at which the coating layer is dried (drying time) is preferably more than 10 seconds, more preferably 30 seconds or higher, and even more preferably 1 minute or higher, from the viewpoint of sufficiently improving the adhesion between the resist film formed by carrying out the drying process in a lower temperature range and the workpiece, and is preferably 60 minutes or lower, more preferably 30 minutes or lower, from the viewpoint of reducing the change in the molecular weight of the polymer A and the polymer B in the resist film before and after the drying process.

(Exposure process)
In the exposure step, a desired pattern is drawn by irradiating predetermined locations of the resist film formed in the resist film formation step with exposure light, which is ionizing radiation or non-ionizing radiation with a wavelength of 300 nm or less. Irradiation with exposure light creates poorly soluble parts A and easily soluble parts B in the resist film to form a latent image pattern. In addition, in the exposure step, a latent image pattern is formed while a crosslinking reaction by a crosslinking agent is allowed to proceed. In particular, when at least one of the polymer A and the polymer B constituting the resist film is a main chain scission type, in the exposure step, the crosslinking reaction and the main chain scission reaction of the polymer A and/or the polymer B proceed in parallel. In this case, it is more advantageous in terms of expanding the exposure margin.

Here, ionizing radiation is radiation that has enough energy to ionize atoms or molecules. In contrast, non-ionizing radiation is radiation that does not have enough energy to ionize atoms or molecules.

Examples of ionizing radiation include electron beams, extreme ultraviolet rays, gamma rays, X-rays, alpha rays, heavy particle beams, proton beams, beta rays, and ion beams. Among these, electron beams or extreme ultraviolet rays are preferred as ionizing radiation, and electron beams are more preferred. The wavelength of extreme ultraviolet rays is not particularly limited and can be, for example, 1 nm or more and 30 nm or less, and is preferably 13.5 nm.

Non-ionizing radiation with a wavelength of 300 nm or less includes, for example, far ultraviolet rays excluding extreme ultraviolet rays (wavelength: 40 nm or more and 200 nm or less), near ultraviolet rays (wavelength: more than 200 nm and 300 nm or less). Among these, KrF excimer laser rays (wavelength: 248 nm) and ArF excimer laser rays (wavelength: 193 nm) are preferred.

The amount of irradiation in the exposure step is not particularly limited, but is usually 10 mJ/cm ² or more and 3000 mJ/cm ² or less, and when an electron beam (EB) is used, it is usually 0.1 μC/cm ² or more and 1000 μC/cm ² or less. In addition, for example, as an exposure device for carrying out the exposure step, a known exposure device such as an electron beam drawing device or a laser drawing device can be used.

(Post-exposure bake process)
In the method for forming a resist pattern of the present invention, from the viewpoint of mitigating the effects of standing waves due to exposure and suppressing the occurrence of unevenness in the resist pattern, a post-exposure bake step of heating the resist film after the exposure step can be optionally carried out.
The heating temperature is not particularly limited, but from the viewpoint of sufficiently suppressing the occurrence of unevenness in the resist pattern, it is preferably 80° C. or higher, and more preferably 100° C. or higher, and from the viewpoint of suppressing the generation of gas due to decomposition of the resist film by heat, it is preferably 160° C. or lower, and more preferably 140° C. or lower.
Furthermore, the time for which the resist film is heated in the post-exposure bake step (heating time) is not particularly limited, but from the viewpoint of sufficiently suppressing the occurrence of unevenness in the resist pattern, it is preferably 30 seconds or more, and more preferably 1 minute or more, and from the viewpoint of production efficiency, it is preferably 20 minutes or less, and more preferably 10 minutes or less.

The method for heating the resist film in the post-exposure bake step is not particularly limited, and examples include a method of heating the resist film on a hot plate, a method of heating the resist film in an oven, and a method of blowing hot air onto the resist film.

(Developing process)
In the developing step, the latent image pattern of the resist film that has been subjected to the exposure step or post-exposure bake step is developed to form a developed film on the workpiece.
Here, the development of the resist film can be carried out, for example, by contacting the resist film with a developer. The method of contacting the resist film with the developer is not particularly limited, and known methods such as immersing the resist film in the developer or applying the developer to the resist film can be used.
The developer can be appropriately selected depending on the properties of the above-mentioned polymer A and polymer B. As the developer, it is preferable to select a developer that does not dissolve the resist film before the exposure step is performed, but can dissolve the easily soluble portion B of the resist film that has been subjected to the exposure step or the post-exposure bake step. The developer is not particularly limited, and examples thereof include hydrofluorocarbons such as 1,1,1,2,3,4,4,5,5,5-decafluoropentane (CF ₃ CFHCFHCF ₂ CF ₃ ), 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane, 1,1,1,2,2,3,4,5,5,5-decafluoropentane, 1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,3,4,4-nonafluorohexane; 2,2-dichloro-1,1,1-trifluoroethane, 1,1-dichloro-1-fluoroethane, and 1,1-dichloro-2,2,3,3,3-pentafluoropropane (CF ₃ CF ₂ CHCl ₂ hydrochlorofluorocarbons such as 1,3-dichloro-1,1,2,2,3-pentafluoropropane (CCIF ₂ CF ₂ CHClF) and the like; hydrofluoroethers such as methyl nonafluorobutyl ether (CF ₃ CF ₂ CF ₂ CF ₂ OCH ₃₎ , methyl nonafluoroisobutyl ether, ethyl nonafluorobutyl ether (CF ₃ CF ₂ CF ₂ CF ₂ OC ₂ H ₅ ), ethyl nonafluoroisobutyl ether, perfluorohexyl methyl ether (CF ₃ CF ₂ CF(OCH ₃ )C ₃ F ₇ ) and the like; and CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , C ₄ F ₁₀ , C ₅ F ₁₂ , C ₆ F ₁₂ , C ₆ F _{14 .} Fluorine-based solvents such as perfluorocarbons such as C ₇ F ₁₄ , C ₇ F ₁₆ , C ₈ F ₁₈ , and C ₉ F ₂₀ ; alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, and 3-pentanol; acetates having an alkyl group such as amyl acetate and hexyl acetate; mixtures of fluorine-based solvents and alcohols; mixtures of fluorine-based solvents and acetates having an alkyl group; mixtures of alcohols and acetates having an alkyl group; mixtures of fluorine-based solvents, alcohols, and acetates having an alkyl group; and the like can be used. Among these, it is preferable to use alcohols such as 2-butanol and isopropyl alcohol as the developer, since the contrast of the resist pattern can be further increased. In addition, the developer may be used alone or in a mixture of two or more kinds at any ratio.

(Rinse process)
In the method for forming a resist pattern of the present invention, a step of removing the developer may be carried out after the development step. The developer may be removed, for example, by using a rinse solution.
The rinse liquid is not particularly limited as long as it does not dissolve the resist pattern, and a solution containing water or a general organic solvent can be used. When selecting a rinse liquid, it is preferable to select a rinse liquid that is easily mixed with the developer.

The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.
Various measurements and evaluations in the examples and comparative examples were carried out according to the following methods.

<Attributes of crosslinking agent>
The judgment of whether the crosslinking agent satisfies the attribute of "reacting with ionizing radiation or nonionizing radiation having a wavelength of 300 nm or less" was carried out according to the following method. A crosslinking agent solution (concentration: 10% by mass, solvent: isoamyl acetate) was applied onto a silicon wafer, the solvent was evaporated, and a test piece in a state in which it would not flow even when left standing was prepared. The thickness of this test piece was measured and designated as ^T1 . After irradiating this test piece with 400 uC/ ^cm2 of a 50 keV electron beam, it was immersed in the same type of solvent as that used in preparing the crosslinking agent solution at room temperature (23°C) for 1 minute and dried. The thickness ^T2 of the dried test piece was measured, and if the value of ^T2 / ^T1 x 100% was 50% or more, the crosslinking agent was judged to "react with ionizing radiation or nonionizing radiation having a wavelength of 300 nm or less".
The results of evaluation of the various crosslinking agents used in the examples are shown in Table 1.

<Proportion of Monomer Units in Copolymer>
For the copolymers A1, B1 and B2 prepared in the Preparation Examples, the proportions of monomer units in the copolymers were calculated by ¹ H-NMR.
Specifically, the copolymer obtained in each Preparation Example was dissolved in chloroform-d, 99.8% (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) to a concentration of 10% by mass, and the resulting solution was measured using a nuclear magnetic resonance apparatus (manufactured by JEOL, 400 mHz), and the proportion of monomer units in the copolymer was calculated from the measurement results.

<Weight average molecular weight, number average molecular weight and molecular weight distribution>
For the copolymers A1, B1 and B2 prepared in Preparation Examples, the weight average molecular weight (Mw) and number average molecular weight (Mn) were measured by gel permeation chromatography, and the molecular weight distribution (Mw/Mn) was measured.
Specifically, the weight average molecular weight (Mw) and number average molecular weight (Mn) of copolymer A1 and copolymer B1 were determined in terms of standard polystyrene using a gel permeation chromatograph (HLC-8220, manufactured by Tosoh Corporation) and tetrahydrofuran as a developing solvent, and the molecular weight distribution (Mw/Mn) was calculated.

<Surface free energy>
The surface free energy was measured using the copolymers A1, B1 and B2 prepared in Preparation Examples.
Specifically, first, copolymer A1, copolymer B1, and copolymer B2 were each dissolved in isoamyl acetate as a solvent to prepare a positive resist composition with a concentration of 3% by mass. Next, using a spin coater (MS-A150, manufactured by Mikasa Co., Ltd.), the positive resist composition was applied to a silicon wafer with a diameter of 4 inches to a thickness of 50 nm. Next, the applied positive resist composition was heated on a hot plate at a temperature of 170° C. for 1 minute to form a film (resist film) on the silicon wafer. For the obtained film (resist film), the contact angles of two types of solvents (water and diiodomethane) with known surface tension, polar term (p), and dispersion force term (d) were measured under the following conditions using a contact angle meter (Drop Master 700, manufactured by Kyowa Interface Science Co., Ltd.), and the surface free energy was evaluated by the Owens-Wendt (extended Fowkes equation) method, and the surface free energy of the film (resist film) was calculated.
<Conditions for measuring contact angle>
Needle: Metal needle 22G (water), Teflon (registered trademark) coated 22G (diiodomethane)
Waiting time: 1000ms
Volume: 1.8 μL
Liquid recognition: water 50dat, diiodomethane 100dat
Temperature: 23°C

<γ value>
The γ value was measured using the positive resist compositions obtained in the examples and comparative examples.
Specifically, a positive resist composition was applied to a silicon wafer having a diameter of 4 inches to a thickness of 50 nm using a spin coater (MS-A150, manufactured by Mikasa). The applied positive resist composition was heated on a hot plate at a temperature of 140° C. for 1 minute to form a resist film on the silicon wafer (resist film forming process). Then, using an electron beam lithography device (ELS-S50, manufactured by Elionix), a plurality of patterns (dimensions 500 μm×500 μm) with different amounts of electron beam irradiation were drawn on the resist film, and the exposed resist film was heated on a hot plate at 100° C. for 1 minute. The heated resist film was subjected to a development process at a temperature of 23° C. for 1 minute using isopropyl alcohol as a developer. The developer was then removed by nitrogen blowing.
The dose of the electron beam was varied in increments of 4 μC/cm ² within a range of 4 μC/cm ² to 200 μC/cm ^2. Next, the thickness of the resist film in the written portion was measured with an optical film thickness meter (Lambda Ace, manufactured by SCREEN Semiconductor Solutions), and a sensitivity curve was created showing the relationship between the common logarithm of the total dose of the electron beam and the remaining film ratio of the resist film after development (= film thickness of the resist film after development/film thickness of the resist film formed on the silicon wafer).
The sensitivity curve obtained (horizontal axis: common logarithm of the total dose of electron beam, vertical axis: residual film ratio of resist film (0≦remaining film ratio≦1.00)) was fitted to a quadratic function in the range of residual film ratio of 0.30 to 0.80, and a straight line (an approximation line of the slope of the sensitivity curve) connecting the point of residual film ratio 0 and the point of residual film ratio 0.50 on the obtained quadratic function (a function of residual film ratio and common logarithm of total dose) was created. In addition, the total dose of electron beam E _th (μC/cm ² ) when the residual film ratio of the obtained straight line (a function of residual film ratio and common logarithm of total dose) was 0 was determined. Note that the smaller the value of E _th , the higher the sensitivity, indicating that polymer A and polymer B as positive resists can be cut well with a smaller dose.
The γ value was calculated using the following formula. In the formula, E ₀ is the logarithm of the total irradiation amount obtained when fitting the sensitivity curve to a quadratic function in the range of the residual film ratio of 0.30 to 0.80, and substituting the residual film ratio of 0 for the obtained quadratic function (a function of the residual film ratio and the common logarithm of the total irradiation amount). In addition, E ₁ is the logarithm of the total irradiation amount obtained when creating a straight line (an approximation line of the slope of the sensitivity curve) connecting the point of the residual film ratio of 0 and the point of the residual film ratio of 0.50 on the obtained quadratic function, and substituting the residual film ratio of 1.00 for the obtained straight line (a function of the residual film ratio and the common logarithm of the total irradiation amount). The formula below represents the slope of the straight line between the residual film ratios of 0 and 1.00. The larger the γ value, the larger the slope of the sensitivity curve, indicating that a pattern with high clarity can be formed well.

<Residual film ratio (half pitch (hp): 25 nm)>
Using a spin coater (MS-A150, manufactured by Mikasa), the positive resist compositions obtained in the examples and comparative examples were applied onto a 4-inch silicon wafer to a thickness of 50 nm. The applied resist composition was then heated on a hot plate at a temperature of 140° C. for 1 minute to form a positive resist film on the silicon wafer. Then, using an electron beam lithography device (ELS-S50, manufactured by Elionix), a line and space 1:1 pattern (i.e., half pitch 25 nm) with a line width of 25 nm was electron-beam lithography at the optimum exposure dose (E _op ) to obtain an electron-beam lithography-processed wafer. The optimum exposure dose was appropriately set, with a value approximately twice that of E _th as a guide.
The electron beam written wafer was immersed in isopropyl alcohol (IPA) as a resist developer at 23° C. for 1 minute to perform a development process. The developer was then removed by nitrogen blowing to form a line and space pattern (half pitch: 25 nm). The pattern portion was then cleaved and observed at a magnification of 100,000 times using a scanning electron microscope (manufactured by JEOL Ltd., JMS-7800F PRIME), and the maximum height (Tmax) of the resist pattern after development and the initial thickness T ₀ of the resist film were measured. Then, the "residual film ratio (half pitch (hp): 25 nm)" was calculated using the following formula and evaluated based on the following criteria. The results are shown in Table 1. The higher this residual film ratio (half pitch (hp): 25 nm), the less the resist pattern top is reduced, which means that the occurrence of top loss is suppressed.
Residual film rate (%)=(Tmax/T ₀ )×100
AA: Over 98.5% A: Over 97.5% and up to 98.5% B: Over 96% and up to 97.5% C: Up to 96%

<Exposure Margin>
The line and space patterns with a half pitch (hp) of 25 nm formed in the examples and comparative examples were evaluated according to the following criteria for the range of electron beam irradiation dose that allowed the formation of a resist pattern with a half pitch (hp) of 25 nm, without taking into account the quality of the pattern. The results are shown in Table 1.
AA: The range of electron beam irradiation amount is 80 μC/ ^cm2 or more. A: The range of electron beam irradiation amount is 50 μC/ ^cm2 or more and less than 80 μC/ ^cm2. B: The range of electron beam irradiation amount is 30 μC/ ^cm2 or more and less than 50 μC/ ^cm2.

<Resist Residue>
The resist residue was evaluated using the positive resist compositions obtained in the examples and comparative examples. Specifically, the resist pattern formed in the evaluation of the above-mentioned <remaining film ratio> was observed at a magnification of 100,000 times using a scanning electron microscope (SEM), and the extent to which the residue remained in the resist pattern was evaluated according to the following criteria. The results are shown in Table 1. The residue remaining in the resist pattern can be confirmed in the SEM image as a high-luminance "dot" or the like compared to the line pattern area where no residue is attached. The smaller the residue in the resist pattern, the higher the contrast of the resist pattern.
A: No residue was observed in the hp25 nm resist pattern.
B: There is a very small amount of residue in the hp 25 nm resist pattern, but it is within the acceptable range.
C: A large amount of residue was observed in the hp 25 nm resist pattern, which is outside the allowable range.

(Preparation Example 1)
<Preparation of Copolymer A1>
[Preparation of an aqueous solution of semi-hardened beef tallow fatty acid potassium soap with a solid content of 18%]
100g of ion-exchanged water was prepared, heated to 70°C while stirring, and 8.40g of potassium hydroxide (49% aqueous solution) was added. Next, 19.6g of beef tallow 45° hydrogenated fatty acid HFA (NOF Corp.) was added at a rate of 1.28g/min, and then 0.126g of potassium silicate was added. The mixture was stirred at 80°C for 2 hours or more to obtain an aqueous solution of semi-hydrogenated beef tallow fatty acid potassium soap with a solid content of 18%.
[Synthesis of Polymer]
Into a glass ampoule containing a stirrer, 3 g of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) as monomer (b) and 1.066 g of α-methylstyrene as monomer (c) were added. In addition, to the same ampoule, 6.771 g of ion-exchanged water was added to 0.5463 g of the aqueous solution of the semi-hardened beef tallow fatty acid potassium soap with a solid content of 18% prepared as described above to prepare a monomer composition, and the ampoule was sealed and pressurized and depressurized with nitrogen gas 10 times to remove oxygen from the system.
The system was then heated to 75° C. and polymerization reaction was carried out for 1 hour. Next, 10 g of tetrahydrofuran (THF) was added to the system, and the resulting solution was dropped into 100 g of a mixed solvent of THF and methanol (MeOH) [THF:MeOH (mass ratio) 30:70] to precipitate a polymer. Thereafter, the precipitated polymer was collected by filtration to obtain a polymer.
[Purification of Polymer]
Next, the obtained polymer was dissolved in 10 g of THF, and the obtained solution was dropped into 100 g of a mixed solvent of THF and MeOH (THF:MeOH (mass ratio) 34:66) to precipitate a white coagulant. Thereafter, the solution containing the precipitated coagulant was filtered with a Kiriyama funnel to obtain a white copolymer A1 as polymer A. The obtained copolymer A1 contained 54 mol% of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units and 46 mol% of α-methylstyrene units. In addition, this copolymer A1 had a weight average molecular weight (Mw) of 382253, a number average molecular weight (Mn) of 259380, a molecular weight distribution (Mw/Mn) of 1.474, and a surface free energy of 31 mJ/ ^m2 .

(Preparation Example 2)
<Preparation of Copolymer B1>
[Synthesis of Polymer]
A monomer composition containing 3 g of 2,2,3,3,3-pentafluoropropyl α-chloroacrylate (ACAPFP) as monomer (d), 3.476 g of α-methylstyrene as monomer (e), 0.0005 g of azobisisobutyronitrile as a polymerization initiator, and 1.6205 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and substituted with nitrogen, and the mixture was stirred in a constant temperature bath at 78° C. for 2 hours under a nitrogen atmosphere.
After that, the temperature was returned to room temperature, and the glass container was opened to the atmosphere, and then 10 g of THF was added to the obtained solution. The solution to which THF was added was then dropped into 100 g of MeOH as a solvent to precipitate a polymer. The solution containing the precipitated polymer was then filtered using a Kiriyama funnel to obtain a polymer.
[Purification of Polymer]
Next, the obtained polymer was dissolved in 100 g of THF, and the obtained solution was dropped into 100 g of a mixed solvent of THF and MeOH [THF:MeOH (mass ratio) 20:80] to precipitate a white coagulant. Thereafter, the solution containing the precipitated coagulant was filtered with a Kiriyama funnel to obtain a white copolymer B1 as polymer B. The obtained copolymer B1 contained 50 mol% each of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl units and α-methylstyrene units. In addition, this copolymer B1 had a weight average molecular weight (Mw) of 49556, a number average molecular weight (Mn) of 35806, a molecular weight distribution (Mw/Mn) of 1.384, and a surface free energy of 24.2 mJ/m ² .

(Preparation Example 3)
<Preparation of Copolymer B2>
Monomer composition X1 containing 0.7207 g of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl (ACAFPh) as monomer (b), 2.0711 g of α-chloroacrylic acid 2,2,3,3,3-pentafluoropropyl (ACAPFP) as monomer (d), 3.0000 g of α-methylstyrene as monomer (e) (corresponding to about 2.34 equivalents when the total of ACAFPh and ACAPFP is taken as 1 equivalent), 0.0048 g of azobisisobutyronitrile as a polymerization initiator, and 1.4491 g of cyclopentanone as a solvent was placed in a glass container, the glass container was sealed and replaced with nitrogen, and the mixture was stirred in a constant temperature bath at 78° C. under a nitrogen atmosphere for 6 hours.
Then, the temperature was returned to room temperature, and the glass container was opened to the atmosphere, and 10 g of THF was added to the obtained solution. The solution to which THF had been added was then dropped into 100 g of MeOH as a solvent to precipitate a polymer. The solution containing the precipitated polymer was then filtered through a Kiriyama funnel to obtain a white coagulated product (copolymer B2). The obtained copolymer B2 contained 10 mol% of α-chloroacrylic acid-1-phenyl-1-trifluoromethyl-2,2,2-trifluoroethyl units, 40 mol% of α-chloroacrylic acid-2,2,3,3,3-pentafluoropropyl units, and 50 mol% of α-methylstyrene units. In addition, this copolymer B2 had a weight average molecular weight (Mw) of 53546, a number average molecular weight (Mn) of 30129, a molecular weight distribution (Mw/Mn) of 1.777, and a surface free energy of 26.1 mJ/m ² .

Example 1
<Preparation of Resist Composition>
As the polymer A, 80 parts of the copolymer A1 prepared as above, as the polymer B, 20 parts of the copolymer B1 prepared as above, 10 parts of polyethylene glycol diacrylate (manufactured by Toa Gosei Co., Ltd., product name "Anilox (registered trademark) M-240") as the crosslinking agent C1, and 5000 parts of isoamyl acetate as the solvent were mixed to obtain a mixed solution. The obtained mixed solution was filtered through a membrane filter with a pore size of 20 nm to prepare a resist composition. The difference in surface free energy between the polymer A and the polymer B was 3 mJ/ ^m2 or more.
<Formation of Resist Pattern>
-Resist film formation process-
Using a spin coater (MS-A150, manufactured by Mikasa Co., Ltd.), the resist composition prepared as described above was applied to a 4-inch silicon wafer to a thickness of 30 nm to form 5000 coating layers (coating step). In order to remove the solvent from the formed coating layer, the coating layer was heated and dried on a hot plate at a temperature of 140° C. for 1 minute (pre-baking step) to form a positive resist film on the silicon wafer (drying step).
-Exposure process-
Next, the resist film was exposed to an electron beam lithography system (ELS-S50, manufactured by Elionix) at an acceleration voltage of 50 kV and an electron beam dose of 10 to 600 μC/cm ² to write a line and space pattern with a half pitch (hp) of 25 nm.
-Development process-
Thereafter, a development process was carried out at 23° C. for 1 minute using isopropyl alcohol as a developer, and then the developer was removed by nitrogen blowing to form a resist pattern.
-evaluation-
The resist pattern thus formed was then observed under a scanning electron microscope (SEM) (magnification: 100,000 times) to evaluate the remaining film ratio, exposure margin, and resist residue. The results are shown in Table 1.

(Examples 2 to 6)
In preparing the resist composition, the mass ratio of polymer A, polymer B, and crosslinking agent in the resist composition (polymer A1:polymer B1:crosslinking agent C1) was changed to 80:20:20 (Example 2), 80:20:30 (Example 3), 90:10:20 (Example 4), 70:30:20 (Example 5), and 70:30:40 (Example 6). Otherwise, the resist composition was prepared in the same manner as in Example 1, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 7)
In preparing the resist composition, trimethylolpropane PO modified triacrylate (manufactured by Toagosei Co., Ltd., product name: "Aronix (registered trademark) M-321") was used as crosslinking agent C2 instead of crosslinking agent C1. In addition, the mass ratio of polymer A, polymer B, and crosslinking agent in the resist composition (polymer A1:polymer B1:crosslinking agent C2) was changed to 80:20:10. Except for this, a resist composition was prepared in the same manner as in Example 1, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 8)
In preparing the resist composition, a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (manufactured by Toagosei Co., Ltd., product name: "Aronix (registered trademark) M-403") was used as crosslinking agent C3 instead of crosslinking agent C1. In addition, the mass ratio of polymer A, polymer B, and crosslinking agent in the resist composition (polymer A:polymer B:crosslinking agent C3) was changed to 80:20:10. A resist composition was prepared in the same manner as in Example 1, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

Example 9
In preparing the resist composition, a mixture of isocyanuric acid ethylene oxide modified diacrylate and isocyanuric acid ethylene oxide modified triacrylate (manufactured by Toagosei Co., Ltd., product name: "Aronix (registered trademark) M-315") was used as crosslinking agent C4 instead of crosslinking agent C1. In addition, the mass ratio of polymer A, polymer B, and crosslinking agent in the resist composition (polymer A:polymer B:crosslinking agent C4) was changed to 80:20:10. A resist composition was prepared in the same manner as in Example 1, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

Example 10
In preparing the resist composition, triallyl isocyanurate (Mitsubishi Chemical Corporation, product name: "TAIC") was used as crosslinking agent C5 instead of crosslinking agent C1. In addition, the mass ratio of polymer A, polymer B, and crosslinking agent in the resist composition (polymer A:polymer B:crosslinking agent C5) was changed to 80:20:10. A resist composition was prepared in the same manner as in Example 1 except for this, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 11)
In preparing the resist composition, copolymer B2 was used instead of copolymer B1 as polymer B. Except for this, a resist composition was prepared in the same manner as in Example 1, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

Example 12
In preparing the resist composition, copolymer B2 was used instead of copolymer B1 as polymer B. Except for this, a resist composition was prepared in the same manner as in Example 10, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
In preparing the resist composition, polymer B and a crosslinking agent were not blended. Except for this, a resist composition was prepared in the same manner as in Example 1, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
In preparing the resist composition, Copolymer A and a crosslinking agent were not blended. Except for this, a resist composition was prepared in the same manner as in Example 1, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
In preparing the resist composition, copolymer A and a crosslinking agent were not blended. In addition, polymer B2 was used instead of polymer B1 as polymer B. Except for this, a resist composition was prepared in the same manner as in Example 1, a resist pattern was formed, and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

In Table 1,
"A1" represents copolymer A1;
"B1" indicates copolymer B1;
"B2" indicates copolymer B2;
"C1" represents polyethylene glycol diacrylate;
"C2" represents trimethylolpropane PO modified triacrylate;
"C3" represents a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate;
"C4" represents a mixture of isocyanuric acid ethylene oxide modified diacrylate and isocyanuric acid ethylene oxide modified triacrylate;
"C5" represents triallyl isocyanurate;
"PAB" indicates a pre-bake step,
"SFE(A)" indicates the surface free energy of copolymer A,
"SFE(B)" indicates the surface free energy of copolymer B,
"PEB" refers to a post-exposure bake step;
"IPA" refers to isopropyl alcohol.

The results shown in Table 1 show that in Examples 1 to 12, which used resist compositions containing a crosslinker that reacts with ionizing radiation or non-ionizing radiation with a wavelength of 300 nm or less, polymer A, and polymer B (the difference in surface free energy between polymer A and polymer B is 3 mJ/ ^m2 or more), the exposure margin of the resist film was wide, and the obtained resist patterns suppressed the occurrence of top loss and had a reduced amount of resist residue.
On the other hand, in Comparative Example 1 in which polymer B and a crosslinking agent were not blended, and Comparative Examples 2 and 3 in which polymer A and a crosslinking agent were not blended, it was found that it was not possible to effectively achieve all of the effects of expanding the exposure margin of the resist film, suppressing the occurrence of top loss, and reducing the amount of resist residue.

Claims

a crosslinking agent that reacts with ionizing radiation or non-ionizing radiation having a wavelength of 300 nm or less;
A solvent;
Polymer A,
and a polymer B,
A resist composition, wherein the surface free energy of the polymer A is larger than the surface free energy of the polymer B, and the difference between the surface free energy of the polymer A and the surface free energy of the polymer B is 3 mJ/ m2 or more.
When the content of the polymer A in the resist composition is A (parts by mass), the content of the polymer is B (parts by mass), and the content of the crosslinking agent is C (parts by mass), the following relationship (x):
A ≧ (B + C) ... (x)
(In the formula (x), B>0 and C>0.)
The resist composition according to claim 1 , which satisfies the above formula (1).
The resist composition according to claim 1, wherein at least one of the polymer A and the polymer B is a main chain cleavage type.
At least one of the polymer A and the polymer B is represented by the following formula (I):

[In formula (I), R 1 is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group, or a halogenated alkyl group; R 2 is a hydrogen atom or an organic group having 0 to 20 fluorine atoms; R 3 and R 4 are a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other.]
2. The resist composition according to claim 1, which has a monomer unit (I) represented by the following formula:
The polymer A is represented by the following formula (II):

[In formula (II), L is a divalent linking group having a fluorine atom, Ar is an aromatic ring group which may have a substituent, R5 is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group or a halogenated alkyl group, and R6 and R7 are a hydrogen atom, a halogen atom, an unsubstituted alkyl group or an alkyl group substituted with a halogen atom, and may be the same or different from each other.]
A monomer unit (II) represented by
The following formula (III):

[In formula (III), R 8 , R 11 , and R 12 are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from one another; R 9 is hydrogen atoms, halogen atoms, carboxyl groups, halogenated carboxyl groups, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms; R 10 is hydrogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms; p and q are integers of 0 to 5, and p+q=5.]
2. The resist composition according to claim 1, wherein the monomer unit (III) is a copolymer A having the monomer unit (III) represented by the following formula:
The polymer B is represented by the following formula (IV):

[In formula (IV), R 13 is a halogen atom, a cyano group, an alkylsulfonyl group, an alkoxy group, a nitro group, an acyl group, an alkyl ester group, or a halogenated alkyl group; R 14 is a hydrogen atom or an organic group having 0 to 20 fluorine atoms; R 15 and R 16 are a hydrogen atom, a halogen atom, an unsubstituted alkyl group, or an alkyl group substituted with a halogen atom, and may be the same or different from each other.]
A monomer unit (IV) represented by
The following formula (V):

[In formula (V), R 17 , R 20 , and R 21 are hydrogen atoms, halogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms, and may be the same or different from each other; R 18 is hydrogen atoms, halogen atoms, carboxyl groups, halogenated carboxyl groups, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms; R 19 is hydrogen atoms, unsubstituted alkyl groups, or alkyl groups substituted with halogen atoms; r and s are integers of 0 to 5, and r+s=5.]
and a monomer unit (V) represented by the following formula (1):
The resist composition according to claim 1, wherein the crosslinking agent has an unsaturated bond.
The resist composition according to claim 7, wherein the crosslinking agent has 1 to 10 unsaturated bonds.
The resist composition according to claim 7 or 8, wherein the unsaturated bond possessed by the crosslinking agent is an unsaturated bond contained in a vinyl group, a (meth)acrylate group, or an allyl group.
The resist composition according to claim 1, comprising the crosslinking agent in an amount of 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of the total of the polymer A and the polymer B.
a resist film forming step of coating a resist composition containing a crosslinking agent that reacts with ionizing radiation or non-ionizing radiation having a wavelength of 300 nm or less, a solvent, a polymer A, and a polymer B onto a substrate to obtain a coating layer, and removing the solvent from the coating layer to form a resist film;
an exposure step of exposing the resist film formed in the resist film forming step to ionizing radiation or non-ionizing radiation having a wavelength of 300 nm or less as exposure light, thereby forming a latent image pattern while progressing a crosslinking reaction by the crosslinking agent.
The method for forming a resist pattern according to claim 11, further comprising a developing step of developing the exposed resist film, the developing being carried out using alcohol.