JP2013083973A - Photoresist composition and method for forming resist pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoresist composition excellent in MEEF (mask error enhancement factor), CDU (critical dimension uniformity) and resolution, and to provide a method for forming a resist pattern using the photoresist composition.SOLUTION: The photoresist composition comprises: [A] a polymer having a (meth)acrylate unit (I) having a norbornane ring with a sulfolactone ring in a side chain and having a weight average molecular weight of 3,000 or more and 8,000 or less; and [B] an acid generator. It is preferable that the polymer [A] further contains a structural unit (II) having an acid dissociable group.

Description

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

  In the field of microfabrication for manufacturing integrated circuit elements, etc., irradiation (exposure) of short wavelength radiation represented by KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), etc. is performed in order to obtain a higher degree of integration. The lithography technology used is being developed. Resist materials suitable for these exposure light sources are required to have high sensitivity, high resolution, etc., and usually contain chemical components containing an acid-dissociable group and an acid generator that generates acid upon irradiation with radiation. An amplification type photoresist composition is used (see Japanese Patent Laid-Open No. 59-45439). Further, in recent years when further miniaturization of devices has progressed, techniques using X-rays, electron beams (EB), extreme ultraviolet rays (EUV), etc., which are shorter wavelengths than excimer lasers are also being studied. .

  However, when a finer resist pattern is formed using a conventional photoresist composition, it is appropriate that the acid diffusion distance (hereinafter also referred to as “diffusion length”) in the resist film is somewhat short. However, this diffusion length is inadequate, or MEEF (Mask Error Enhancement Factor), CDU (Critical Dimension Uniformity), Depth Of Focus (DOF), which are indicators of mask error tolerance. )), The present situation is that the lithography properties such as resolution cannot be sufficiently satisfied.

  In view of such circumstances, a photoresist composition for forming a finer resist pattern is desired not only to improve basic characteristics such as sensitivity, but also to improve MEEF, CDU, resolution and the like.

JP 59-45439 A

  The present invention has been made based on the above circumstances, and its object is to provide a MEEF, a CDU, a photoresist composition excellent in resolution, and a method of forming a resist pattern using this photoresist composition. It is to be.

（式（１）中、Ｒ^１は、水素原子、フッ素原子、メチル基又はトリフルオロメチル基である。Ｒ^２は、酸素原子、硫黄原子、炭素数１以上５以下の２価の鎖状炭化水素基又はこれらを組み合わせてなる基である。Ｒ^３は、１価の有機基である。ａは、０〜２の整数である。但し、ａが２である場合、複数のＲ^３は同一でも異なっていてもよい。） The invention made to solve the above problems is
[A] A polymer having a structural unit (I) represented by the following formula (1) and having a weight average molecular weight of 3,000 or more and 8,000 or less (hereinafter also referred to as “[A] polymer”). And [B] an acid generator,
Is a photoresist composition containing

(In Formula (1), R ¹ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ² is an oxygen atom, a sulfur atom, or a divalent chain carbon atom having 1 to 5 carbon atoms. R ³ is a monovalent organic group, a is an integer of 0 to 2, provided that when a is 2, a plurality of R ³ are the same. But it may be different.)

  The photoresist composition of the present invention contains a [B] acid generator, and an acid is generated from the [B] acid generator by exposure. In the photoresist composition, the [A] polymer has the structural unit (I) having the specific structure containing a sultone group having high interaction with the acid, and the weight average molecular weight is 3,000. Since it is 8,000 or less, the diffusion length of the acid can be shortened, that is, acid diffusion can be suppressed. As a result, the photoresist composition is excellent in resolution, MEEF and CDU.

  [A] The polymer preferably further has a structural unit (II) containing an acid dissociable group. [A] The polymer further includes a structural unit (II) containing an acid-dissociable group together with a structural unit (I) that can shorten the diffusion length of the acid generated from the acid generator [B] The acid dissociable group of II) is easily dissociated by the action of an acid. As a result, the photoresist composition is excellent in resolution, MEEF and CDU.

  [A] The polymer preferably further has a structural unit (III) containing at least one group selected from the group consisting of a lactone group and a cyclic carbonate group. [A] When the polymer further has the structural unit (III), the resist film formed from the photoresist can improve the adhesion to a substrate or the like.

  [A] The content of the structural unit (I) in the polymer is preferably 5 mol% or more and 20 mol% or less. In the photoresist composition, the [A] polymer has the structural unit (I) at the specific content, whereby the acid diffusion length can be controlled within an appropriate range. Therefore, the said photoresist composition is further excellent in resolution, MEEF, and CDU.

  [B] The acid generator preferably has an alicyclic structure having 8 to 30 carbon atoms. [B] Since the acid generator has a bulky structure including an alicyclic structure, it is possible to further suppress diffusion of an acid generated by exposure. The photoresist composition containing such a [B] acid generator together with the [A] polymer can further improve the resolution, MEEF and CDU.

  The photoresist composition preferably further contains a [C] water-repellent polymer additive containing a fluorine atom (hereinafter also referred to as “[C] water-repellent polymer additive”). Since the photoresist composition further contains a [C] water-repellent polymer additive and the formed resist film surface is excellent in water repellency, it can be suitably used for immersion exposure.

The resist pattern forming method of the present invention comprises:
(1) A step of forming a resist film using the photoresist composition of the present invention,
(2) a step of exposing the resist film; and (3) a step of developing the exposed resist film.

  According to the resist pattern forming method, by using the photoresist composition, the resolution can be sufficiently satisfied, and a resist pattern excellent in MEEF and CDU can be formed. Therefore, a fine pattern can be formed with high accuracy and stability by a pattern forming method using the photoresist composition with respect to radiation such as KrF excimer laser or ArF excimer laser. The photoresist composition and the pattern forming method using the photoresist composition can be suitably used for manufacturing semiconductor devices that are expected to be further miniaturized in the future.

  Further, “radiation” is a concept including visible light, ultraviolet light, far ultraviolet light, X-rays, charged particle beams, EUV, and the like. “Organic group” refers to a group containing at least one carbon atom.

  According to the photoresist composition of the present invention and the pattern forming method using the same, a pattern excellent in resolution, MEEF and CDU can be formed. Therefore, a fine pattern can be formed with high accuracy and stability by a pattern forming method using radiation such as KrF excimer laser or ArF excimer laser as exposure light and using the photoresist composition. Therefore, the said photoresist composition and the pattern formation method using the same can be used suitably for the semiconductor device manufacture from which refinement | miniaturization is anticipated further from now on.

<Photoresist composition>
The photoresist composition of the present invention contains a [A] polymer and a [B] acid generator. The photoresist composition preferably contains [C] a water-repellent polymer additive, [D] an acid diffusion controller, and [E] a solvent. Furthermore, the said photoresist composition may contain another arbitrary component, unless the effect of this invention is impaired. Hereinafter, each component will be described in detail.

<[A] polymer>
[A] The polymer has the structural unit (I) represented by the above formula (1) and has a weight average molecular weight of 3,000 or more and 8,000 or less. [A] The polymer has the structural unit (I) having the above specific structure containing a highly polar sultone group, and has a weight average molecular weight of 3,000 or more and 8,000 or less, and [B] acid generation. Has high interaction with acids generated from the body. As a result, the photoresist composition can suppress acid diffusion and is excellent in resolution, MEEF, and CDU.

  [A] The polymer contains at least one group selected from the group consisting of a structural unit (II) containing an acid dissociable group, a lactone group and a cyclic carbonate group in addition to the structural unit (I). It preferably has a structural unit (III). Moreover, the [A] polymer may contain other structural units other than the said structural unit, unless the effect of this invention is prevented. In addition, the [A] polymer may have each structural unit individually by 1 type, and may have 2 or more types. Hereinafter, each structural unit will be described in detail.

[Structural unit (I)]
The structural unit (I) is represented by the above formula (1). In said formula (1), R < ¹ > is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R ² is an oxygen atom, a sulfur atom, a divalent chain hydrocarbon group having 1 to 5 carbon atoms, or a combination of these. R ³ is a monovalent organic group. a is an integer of 0-2. However, when a is 2, several R < ³ > may be same or different.

Examples of the divalent chain hydrocarbon group having 1 to 5 carbon atoms represented by R ² include a methylene group, an ethanediyl group, a propanediyl group, and a butanediyl group. Among these, a methylene group and an ethanediyl group are preferable, and a methylene group is more preferable. In addition, description of the number of atoms, such as C1-C5, may be described as C1-C5 below.

The group formed by combining these represented by ^{R 2,} for example, _{-CH 2 -O-CH 2 -,} - CH 2 -S-CH 2 -, - CH 2 -CH 2 -O-CH 2 -CH _2- , —CH ₂ —CH ₂ —S—CH ₂ —CH ₂ — and the like. Of these, —CH ₂ —O—CH ₂ — and —CH ₂ —S—CH ₂ — are preferred.

R ² is preferably a C 1-5 divalent chain hydrocarbon group, more preferably a methylene group or ethanediyl group, and even more preferably a methylene group.

Examples of the monovalent organic group represented by R ³ include a linear or branched hydrocarbon group having 1 to 10 carbon atoms and an alicyclic group having 4 to 20 carbon atoms.

  Examples of the linear or branched hydrocarbon group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, an n-butyl group, an i-butyl group, a t-butyl group, an n-pentyl group, An n-hexyl group, an i-hexyl group, etc. are mentioned. Among these, a methyl group, an ethyl group, and a propyl group are preferable, and a methyl group and an ethyl group are more preferable.

  Examples of the alicyclic group having 4 to 20 carbon atoms include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, and the like.

As said R < ³ >, a C1-C10 linear or branched hydrocarbon group is preferable, a methyl group, an ethyl group, a propyl group, and a butyl group are more preferable, and a methyl group and an ethyl group are further more preferable.

  As a, 0 or 1 is preferable, and 0 is more preferable.

  Specific examples of the structural unit (I) include structural units represented by the following formulas (1-1) to (1-12).

  Among these, the structural units represented by the above formulas (1-1) to (1-3) are preferable, and the structural unit represented by the formula (1-2) is more preferable.

Examples of the monomer that gives the structural unit (I) include compounds represented by the following formulas. R ¹ has the same meaning as the above formula (1).

  [A] The content of the structural unit (I) in the polymer is preferably 1 mol% or more and 40 mol% or less, more preferably 3 mol% or more and 30 mol% or less, and further more preferably 5 mol% or more and 20 mol% or less. Preferably, it is 7 mol% or more and 18 mol% or less. By making the content rate of structural unit (I) into the said range, the said photoresist composition can suppress the spreading | diffusion of an acid more, and is excellent in MEEF etc.

[Structural unit (II)]
The structural unit (II) is a structural unit having an acid dissociable group. Although it will not specifically limit if it is a structural unit which has the group dissociated by the effect | action of the acid generate | occur | produced from a [B] acid generator by exposure, It is preferable that it is a structural unit represented by following formula (2).

In the formula (2), R ⁴ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ^{5 to} R ⁷ are each independently a linear or branched alkyl group having 1 to 10 carbon atoms, an alicyclic group having 4 to 20 carbon atoms, or an aromatic group having 6 to 20 carbon atoms. However, R ⁵ and R ⁶ may form a divalent alicyclic group having 4 to 20 carbon atoms together with the carbon atom bonded to each other.

Examples of the linear or branched alkyl group having 1 to 10 carbon atoms represented by R ^{5 to} R ⁷ include a methyl group, an ethyl group, a 1-butyl group, an i-butyl group, a sec-butyl group, tert-butyl group, n-pentyl group, i-pentyl group, n-hexyl group, i-hexyl group, n-heptyl group, i-heptyl group, n-octyl group, i-octyl group, n-nonyl group, Examples include i-nonyl group, n-decyl group, i-decyl group and the like.

Examples of the alicyclic group having 4 to 20 carbon atoms represented by R ^{5 to} R ⁷ include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a norbornyl group, an adamantyl group, and the like.

Examples of the aromatic group having 6 to 20 carbon atoms represented by R ^{5 to} R ⁷ include a phenyl group and a naphthyl group.

Examples of the divalent alicyclic hydrocarbon group having 4 to 20 carbon atoms which may be formed together with the carbon atom in which R ⁵ and R ⁶ are bonded to each other include, for example, a cyclobutanediyl group and a cyclopentanediyl group , Cyclohexanediyl group, dicyclopentanediyl group, norbornylene group, tricyclodecanediyl group, tetracyclododecadiyl group, adamantanediyl group, and the like in a form in which two hydrogen atoms are removed.

  Examples of the structural unit (II) include structural units represented by the following formulas (2-1) to (2-21).

In said formula, R < ⁴ > is synonymous with the said Formula (2).

  Among these, the structural units represented by the above formulas (2-1) to (2-17) are preferable.

  Examples of the monomer that gives structural unit (II) include a monomer containing an acid-dissociable group having a monocyclic alicyclic group such as 1-alkyl-cycloalkyl ester, and 2-alkyl-2-dicyclohexane. And monomers containing an acid-dissociable group having a polycyclic alicyclic group such as an alkyl ester.

  [A] The content of the structural unit (II) in the polymer is preferably 10 mol% or more and 80 mol% or less, more preferably 20 mol% or more and 75 mol% or less, and further more preferably 30 mol% or more and 70 mol% or less. preferable. By making the content rate of structural unit (II) into the said range, the lithography performance of the resist pattern obtained improves more.

[Structural unit (III)]
The structural unit (III) is a structural unit containing at least one group selected from the group consisting of a lactone group and a cyclic carbonate group. [A] When a polymer contains structural unit (III), the adhesiveness of the resist film obtained from the said photoresist composition can be improved.

  Examples of the structural unit (III) include a structural unit represented by the following formula.

In the above formula, R ⁸ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

  As a monomer which gives structural unit (III), the compound etc. which are represented by a following formula are mentioned, for example.

  [A] The content of the structural unit (III) in the polymer is preferably 10 mol% to 80 mol%, more preferably 15 mol% to 70 mol%, and still more preferably 20 mol% to 60 mol%. . By making the content rate of structural unit (III) into the said range, the resist film obtained from the said photoresist composition can improve the adhesiveness to a board | substrate etc.

  [A] The polymer may include, for example, a structural unit (IV) having a hydrophilic functional group as another structural unit in addition to the structural units (I) to (III). [A] When the polymer contains the structural unit (IV) having a hydrophilic functional group, the lithography performance of the resist pattern can be further improved.

  Examples of the structural unit (IV) include a structural unit represented by the following formula.

In the above formula, R ⁹ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

  [A] The content of the structural unit (IV) in the polymer is preferably 0 mol% to 30 mol%, more preferably 5 mol% to 20 mol%.

<[A] Polymer Synthesis Method>
[A] The polymer can be produced, for example, by polymerizing a monomer corresponding to each predetermined structural unit in a suitable solvent using a radical polymerization initiator. For example, a method of dropping a solution containing a monomer and a radical initiator into a reaction solvent or a solution containing the monomer to cause a polymerization reaction, a solution containing the monomer, and a solution containing the radical initiator Separately, a method of dropping a reaction solvent or a monomer-containing solution into a polymerization reaction, a plurality of types of solutions containing each monomer, and a solution containing a radical initiator, It is preferable to synthesize by a method such as a method of dropping it into a reaction solvent or a solution containing a monomer to cause a polymerization reaction.

  What is necessary is just to determine the reaction temperature in these methods suitably with initiator seed | species. Usually, it is 30 to 180 ° C, preferably 40 to 160 ° C, and more preferably 50 to 140 ° C. The dropping time varies depending on the reaction temperature, the type of initiator, the monomer to be reacted, etc., but is usually 30 minutes to 8 hours, preferably 45 minutes to 6 hours, and more preferably 1 hour to 5 hours. . Further, the total reaction time including the dropping time varies depending on the conditions similarly to the dropping time, but is usually 30 minutes to 10 hours, preferably 45 minutes to 9 hours, and more preferably 1 hour to 8 hours.

  Examples of the radical initiator used in the polymerization include azobisisobutyronitrile (AIBN), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2 -Cyclopropylpropionitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylpropionitrile) and the like. These initiators can be used alone or in admixture of two or more.

  The polymerization solvent is not limited as long as it is a solvent other than a solvent that inhibits polymerization (nitrobenzene having a polymerization inhibiting effect, mercapto compound having a chain transfer effect, etc.) and can dissolve the monomer. Examples of the polymerization solvent include alcohol solvents, ketone solvents, amide solvents, ester / lactone solvents, nitrile solvents, and mixed solvents thereof. These solvents can be used alone or in combination of two or more.

  The polymer obtained by the polymerization reaction is preferably recovered by a reprecipitation method. That is, after completion of the polymerization reaction, the polymer is recovered as a powder by introducing the polymerization solution into a reprecipitation solvent. As the reprecipitation solvent, alcohols or alkanes can be used alone or in admixture of two or more. In addition to the reprecipitation method, the polymer can be recovered by removing low-molecular components such as monomers and oligomers by a liquid separation operation, a column operation, an ultrafiltration operation, or the like.

  [A] The weight average molecular weight (Mw) in terms of polystyrene by gel permeation chromatography (GPC) of the polymer is preferably 3,000 or more and 8,000 or less, more preferably 3,500 or more and 7,500 or less, and 4,000. More preferably, it is 7,000 or less. In addition, by making Mw of [A] polymer into the said specific range, the lithography performance which used MEEF, CDU, etc. of the said photoresist composition as a parameter | index can be improved.

  [A] The ratio (Mw / Mn) of Mw to the number average molecular weight (Mn) in terms of polystyrene by GPC of the polymer is usually from 1 to 5, preferably from 1 to 3, and preferably from 1 to 2.5. Is more preferable. By setting Mw / Mn in such a range, the photoresist film has excellent resolution performance.

  In addition, Mw and Mn of this specification use a GPC column (Tosoh, G2000HXL, G3000HXL, G4000HXL), flow rate of 1.0 ml / min, elution solvent tetrahydrofuran, column temperature of 40 ° C. It is a value measured by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard under conditions.

<[B] Acid generator>
[B] The acid generator is a compound that generates an acid upon irradiation with radiation that has passed through a mask in an exposure process, which is one process of resist pattern formation. As the form of inclusion of the [B] acid generator in the photoresist composition, even in an embodiment of a compound as described later (hereinafter, this embodiment is also referred to as “[B] acid generator”), as a part of the polymer It may be a built-in embodiment or both of these embodiments.

  [B] Examples of the acid generator include onium salt compounds, sulfonimide compounds, halogen-containing compounds, diazoketone compounds, and the like. Of these, onium salt compounds are preferred.

  Examples of the onium salt compound include sulfonium salts (including tetrahydrothiophenium salts), iodonium salts, phosphonium salts, diazonium salts, pyridinium salts, and the like. Of these, sulfonium salts (including tetrahydrothiophenium salts) and iodonium salts are preferred.

  Examples of the sulfonium salt include triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoro-n-butanesulfonate, triphenylsulfonium perfluoro-n-octanesulfonate, triphenylsulfonium 2-bicyclo [2.2.1] hept- 2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-cyclohexylphenyldiphenylsulfonium perfluoro- n-octanesulfonate, 4-cyclohexylphenyldiphenylsulfonium 2-bicyclo [2.2.1] hept- -Yl-1,1,2,2-tetrafluoroethanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium trifluoromethanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium par Fluoro-n-octanesulfonate, 4-methanesulfonylphenyldiphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium 4- (1 -Adamantanecarbonyloxy) -1,1,2,2-tetrafluorobutanesulfonate, triphenylsulfonium 1,1,2,2-tetrafluoro-6- (1-adamantane carbonate) Carboxymethyl) - hexane-1-sulfonate, and the like. Of these, triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoro-n-butanesulfonate, triphenylsulfonium 4- (1-adamantanecarbonyloxy) -1,1,2,2-tetrafluorobutanesulfonate and triphenylsulfonium Phenylsulfonium 1,1,2,2-tetrafluoro-6- (1-adamantanecarbonyloxy) -hexane-1-sulfonate is preferred, and triphenylsulfonium 1,1,2,2-tetrafluoro-6- (1 -Adamantanecarbonyloxy) -hexane-1-sulfonate is more preferred.

  Examples of the tetrahydrothiophenium salt include 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nona. Fluoro-n-butanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium perfluoro-n-octanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophene Nitro 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (6-n-butoxynaphthalen-2-yl) tetrahydrothiophenium trifluoromethane Sulfonate, 1- (6-n-butoxynaphthalene-2 Yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, 1- (6-n-butoxynaphthalen-2-yl) tetrahydrothiophenium perfluoro-n-octanesulfonate, 1- (6-n-butoxynaphthalene- 2-yl) tetrahydrothiophenium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) ) Tetrahydrothiophenium trifluoromethanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydro Thiophenium perfluoro-n-octance Phonates, 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, etc. Can be mentioned. Of these tetrahydrothiophenium salts, 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium nonafluoro-n-butanesulfonate, 1- (4-n-butoxynaphthalen-1-yl) Tetrahydrothiophenium perfluoro-n-octane sulfonate and 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium nonafluoro-n-butane sulfonate are preferred.

  Examples of the iodonium salt include diphenyliodonium trifluoromethanesulfonate, diphenyliodonium nonafluoro-n-butanesulfonate, diphenyliodonium perfluoro-n-octanesulfonate, diphenyliodonium 2-bicyclo [2.2.1] hept-2-yl- 1,1,2,2-tetrafluoroethanesulfonate, bis (4-t-butylphenyl) iodonium trifluoromethanesulfonate, bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate, bis (4-t -Butylphenyl) iodonium perfluoro-n-octanesulfonate, bis (4-t-butylphenyl) iodonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetra Le Oro ethanesulfonate. Of these iodonium salts, bis (4-t-butylphenyl) iodonium nonafluoro-n-butanesulfonate is preferred.

  [B] The acid generator is preferably a compound having an alicyclic structure having 8 to 30 carbon atoms. [B] Since the acid generator has a bulky structure having an alicyclic structure, the diffusion of the acid generated by exposure can be further suppressed. The photoresist composition containing such a [B] acid generator together with the [A] polymer can further improve the resolution, MEEF and CDU.

  The [B] acid generator having an alicyclic structure having 8 or more carbon atoms is preferably a compound represented by the following formula (3).

In the above formula (3), X ⁺ is an onium cation. R ¹⁰ is a monovalent organic group containing an alicyclic structure having 8 to 30 carbon atoms. R ¹¹ and R ¹² are a hydrogen atom, a fluorine atom, or a chain hydrocarbon group having 1 to 20 carbon atoms. However, one part or all part of the hydrogen atom which the said chain hydrocarbon group has may be substituted by the fluorine atom. At least one of R ¹¹ and R ¹² is a fluorine atom or a perfluoroalkyl group.

Examples of the monovalent organic group containing an alicyclic structure having 8 to 30 carbon atoms represented by R ¹⁰ include an alicyclic group having 8 to 30 carbon atoms; —CO—O— and —O—CO—O. _{-, - O -, - SO} 2 -, - CO-NH -, - SO 2 NH -, - O-CO- and at least one selected from the group consisting of a chain-like hydrocarbon group having 1 to 20 carbon atoms And a group formed by combining the above group and an alicyclic group having 8 to 30 carbon atoms.

  Examples of the alicyclic group having 8 to 30 carbon atoms include a cyclooctyl group, a cyclodecyl group, a cyclododecyl group, a cyclopentadecyl group, a cyclononadecyl group, an adamantyl group, a diamantyl group, and the like.

Examples of the chain hydrocarbon group having 1 to 20 carbon atoms represented by R ¹¹ and R ¹² include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Of these, a methyl group, an ethyl group, and a propyl group are preferable.

As the R ¹¹ and R ^12, a fluorine atom, a trifluoromethyl group and perfluoroethyl group are preferable.

  Examples of the [B] acid generator represented by the above formula (3) include triphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1 among the sulfonium salts exemplified above. 2,2-tetrafluoroethanesulfonate, 4-cyclohexylphenyldiphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, 4-methanesulfonylphenyl Diphenylsulfonium 2-bicyclo [2.2.1] hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate, triphenylsulfonium 4- (1-adamantanecarbonyloxy) -1,1,2, 2-tetrafluorobutanesulfonate, triphenylsulfonium 1,1,2,2-tetrafluoro-6 (1-adamantanecarbonyloxy) - hexane-1-sulfonate, and the like. Of these, triphenylsulfonium 4- (1-adamantanecarbonyloxy) -1,1,2,2-tetrafluorobutanesulfonate and triphenylsulfonium 1,1,2,2-tetrafluoro-6- (1- Adamantanecarbonyloxy) -hexane-1-sulfonate is preferred, and triphenylsulfonium 1,1,2,2-tetrafluoro-6- (1-adamantanecarbonyloxy) -hexane-1-sulfonate is more preferred.

  These [B] acid generators may be used alone or in combination of two or more. [B] The amount used when the acid generator is an “agent” is, from the viewpoint of ensuring the sensitivity and developability of the resist film formed from the photoresist composition, [A] 100 parts by mass of the polymer. On the other hand, it is preferably 0.01 parts by mass or more and 35 parts by mass or less, and more preferably 0.1 parts by mass or more and 30 parts by mass or less.

<[C] Water-repellent polymer additive>
The photoresist composition preferably contains a water-repellent polymer additive containing [C] fluorine atom. When the photoresist composition contains the [C] water-repellent polymer additive, when the resist film is formed, the distribution of the resist film depends on the water-repellent characteristics of the fluorine atom-containing polymer in the film. Since it tends to be unevenly distributed in the vicinity of the surface, it is possible to suppress the elution of the acid generator, the acid diffusion control agent, and the like during the immersion exposure into the immersion medium. In addition, the forward contact angle between the resist film and the immersion medium can be controlled within a desired range due to the water-repellent characteristics of the [C] water-repellent polymer additive, and the occurrence of bubble defects can be suppressed. Furthermore, the receding contact angle between the resist film and the immersion medium is increased, and high-speed scanning exposure is possible without leaving water droplets. Thus, when the said photoresist composition contains a [C] water-repellent polymer additive, the resist film suitable for an immersion exposure method can be formed.

  The [C] water-repellent polymer additive must have a higher fluorine atom content (% by mass) than the [A] polymer. [C] The water-repellent polymer additive has a higher fluorine atom content than [A] polymer, so that the degree of the above-mentioned uneven distribution becomes higher, and the resulting resist film has water repellency and elution suppression properties, etc. Improved characteristics.

  The [C] water-repellent polymer additive in the present invention is formed by polymerizing one or more monomers containing fluorine atoms in the structure.

  As a monomer that gives a polymer containing a fluorine atom in its structure, a monomer containing a fluorine atom in the main chain, a monomer containing a fluorine atom in the side chain, and a fluorine atom in the main chain and the side chain Monomer.

  Examples of monomers that give a polymer containing a fluorine atom in the main chain include α-fluoroacrylate compounds, α-trifluoromethyl acrylate compounds, β-fluoroacrylate compounds, β-trifluoromethyl acrylate compounds, α, β- Examples thereof include a fluoroacrylate compound, an α, β-trifluoromethyl acrylate compound, a compound in which hydrogen at one or more vinyl sites is substituted with fluorine or a trifluoromethyl group, and the like.

  As the monomer that gives a polymer containing a fluorine atom in the side chain, for example, the side chain of an alicyclic olefin compound such as norbornene is fluorine or a fluoroalkyl group or a derivative thereof, a fluoroalkyl group of acrylic acid or methacrylic acid, Examples of the ester compound of the derivative include a fluorine atom or a fluoroalkyl group in which the side chain of one or more olefins (site not including a double bond) or a derivative thereof is used.

  Examples of the monomer that gives a polymer containing fluorine atoms in the main chain and the side chain include α-fluoroacrylic acid, β-fluoroacrylic acid, α, β-fluoroacrylic acid, α-trifluoromethylacrylic acid, Ester compounds of fluoroalkyl groups such as β-trifluoromethylacrylic acid and α, β-trifluoromethylacrylic acid and derivatives thereof, and hydrogen in one or more kinds of vinyl sites are substituted with fluorine atoms or trifluoromethyl groups A compound in which the side chain of a compound is substituted with a fluorine atom or a fluoroalkyl group or a derivative thereof, and hydrogen bonded to a double bond of one or more alicyclic olefin compounds is substituted with a fluorine atom or a trifluoromethyl group. And the side chain is a fluoroalkyl group or a derivative thereof. In addition, this alicyclic olefin compound shows the compound in which a part of ring is a double bond.

  [C] The structural unit possessed by the water-repellent polymer additive includes a structural unit represented by the following formula (hereinafter also referred to as “structural unit (V)”).

In the above formula, R ¹³ is hydrogen, a methyl group or a trifluoromethyl group. Q is a linking group. R ¹⁴ is a linear or branched alkyl group having 1 to 6 carbon atoms containing at least one fluorine atom, or a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms or a derivative thereof. .

  Examples of the linking group represented by Q include a single bond, an oxygen atom, a sulfur atom, a carbonyloxy group, an oxycarbonyl group, an amide group, a sulfonylamide group, and a urethane group.

  Examples of the monomer that gives the structural unit (V) include 2- [1- (ethoxycarbonyl) -1,1-difluorobutyl] (meth) acrylic acid ester, trifluoromethyl (meth) acrylic acid ester, 2, 2,2-trifluoroethyl (meth) acrylic acid ester, perfluoroethyl (meth) acrylic acid ester, perfluoro n-propyl (meth) acrylic acid ester, perfluoro i-propyl (meth) acrylic acid ester, perfluoro n-butyl (meth) acrylic acid ester, perfluoro i-butyl (meth) acrylic acid ester, perfluoro t-butyl (meth) acrylic acid ester, 2- (1,1,1,3,3,3-hexa Fluoropropyl) (meth) acrylic acid ester, 1- (2,2,3,3,4,4,5,5-octaful Lopentyl) (meth) acrylic acid ester, perfluorocyclohexylmethyl (meth) acrylic acid ester, 1- (2,2,3,3,3-pentafluoropropyl) (meth) acrylic acid ester, 1- (3,3 , 4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl) (meth) acrylic acid ester, 1- (5-trifluoro) Methyl-3,3,4,4,5,6,6,6-octafluorohexyl) (meth) acrylic acid ester and the like.

  [C] The water-repellent polymer additive may contain only one type of structural unit (V), or may contain two or more types. [C] The content ratio of the structural unit (V) in the water-repellent polymer additive is usually 5 mol% or more, preferably 10 mol% or more, more preferably 15 mol% or more. By making the content rate of a structural unit (V) into the said specific range, a more preferable receding contact angle can be achieved and elution of an acid generator etc. from a resist film can be suppressed efficiently.

  [C] In addition to the structural unit (V), the water-repellent polymer additive is selected from the group consisting of a structural unit having an acid-dissociable group, a lactone group, and a cyclic carbonate group in order to control the dissolution rate in a developer, for example. One or more kinds of other structural units such as a structural unit containing at least one selected group and a structural unit containing a hydrophilic functional group such as a hydroxyl group and a carboxyl group can be contained.

  As the other structural unit having an acid dissociable group, a structural unit similar to the structural unit exemplified in the structural unit (II) can be applied. As the structural unit containing at least one group selected from the group consisting of the lactone group and the cyclic carbonate group, the same structural unit as the structural unit exemplified in the structural unit (III) can be applied. As the structural unit containing the hydrophilic functional group, a structural unit similar to the structural unit exemplified in the structural unit (IV) can be applied.

  The content of other structural units is usually 80 mol% or less, preferably 75 mol% or less, more preferably 70 mol, when the total structural unit in [C] water-repellent polymer additive is 100 mol%. % Or less.

  [C] The Mw of the water-repellent polymer additive is preferably 1,000 to 100,000, more preferably 2,000 to 50,000, and particularly preferably 3,000 to 30,000. By setting the Mw of the fluorine atom-containing polymer within the specific range, a more preferable receding contact angle can be achieved, and elution of the acid generator and the like from the resist film can be efficiently suppressed. The ratio (Mw / Mn) between Mw and Mn of the fluorine atom-containing polymer is usually 1 to 3, and preferably 1 to 2.5.

  As a content rate of the [C] water-repellent polymer additive in the said radiation sensitive composition, 0-50 mass parts is preferable with respect to 100 mass parts of [A] polymers, and 0-20 mass parts is more preferable. 0.5-10 parts by mass is particularly preferred, and 1-8 parts by mass is most preferred. By making the content rate of the said [C] water-repellent polymer additive in the said photoresist composition into the said range, the water repellency and elution suppression property of the resist film surface obtained can be improved more.

<[C] Method for synthesizing water-repellent polymer additive>
The [C] water-repellent polymer additive can be synthesized, for example, by polymerizing monomers corresponding to predetermined respective structural units in a suitable solvent using a radical polymerization initiator.

  Examples of the radical polymerization initiator and solvent used for the polymerization include the same solvents as those mentioned in the method for synthesizing [A] polymer.

  As reaction temperature in the said superposition | polymerization, 40 to 150 degreeC and 50 to 120 degreeC are preferable normally. The reaction time is usually preferably 1 hour to 48 hours and 1 hour to 24 hours.

<[D] Acid diffusion controller>
[D] The acid diffusion controller is a component that controls the diffusion phenomenon in the resist film of the acid generated from the [B] acid generator by exposure and suppresses an undesirable chemical reaction in the unexposed area. When the photoresist composition contains the [D] acid diffusion controller, the storage stability of the resulting photoresist composition is further improved, and the resolution as a resist is further improved. In addition, it is possible to suppress a change in the line width of the resist pattern due to a change in the holding time from exposure to development processing, and a composition having extremely excellent process stability can be obtained. The content of the [D] acid diffusion controller in the photoresist composition of the present invention may be a free compound (hereinafter also referred to as “[D] acid diffusion controller” as appropriate). It may be a form incorporated as part of the coalescence or both forms.

  [D] Examples of the acid diffusion controller include amine compounds, amide group-containing compounds, urea compounds, nitrogen-containing heterocyclic compounds, and the like.

  Examples of the amine compound include mono (cyclo) alkylamines; di (cyclo) alkylamines; tri (cyclo) alkylamines; substituted alkylanilines or derivatives thereof; ethylenediamine, N, N, N ′, N′-tetra Methylethylenediamine, tetramethylenediamine, hexamethylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, 4,4′-diaminobenzophenone, 4,4′-diaminodiphenylamine, 2,2-bis (4 -Aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2- (4-aminophenyl) -2- (3-hydroxyphenyl) propane, 2- (4-amino) Phenyl) -2- (4-hydroxyphenyl) propane, 1, -Bis (1- (4-aminophenyl) -1-methylethyl) benzene, 1,3-bis (1- (4-aminophenyl) -1-methylethyl) benzene, bis (2-dimethylaminoethyl) ether Bis (2-diethylaminoethyl) ether, 1- (2-hydroxyethyl) -2-imidazolidinone, 2-quinoxalinol, N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine, N, N, N ′, N ″ N ″ -pentamethyldiethylenetriamine, triethanolamine and the like can be mentioned.

  Examples of amide group-containing compounds include Nt-butoxycarbonyl group-containing amino compounds, formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, propionamide, Examples thereof include benzamide, pyrrolidone, N-methylpyrrolidone, N-acetyl-1-adamantylamine, and isocyanuric acid tris (2-hydroxyethyl).

  Examples of urea compounds include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, tri-n-butylthiourea and the like. Is mentioned.

  Examples of the nitrogen-containing heterocyclic compound include imidazoles; pyridines; piperazines; pyrazine, pyrazole, pyridazine, quinosaline, purine, pyrrolidine, piperidine, 4-hydroxy-N-amyloxycarbonylpiperidine, piperidineethanol, 3-piperidino- 1,2-propanediol, morpholine, 4-methylmorpholine, 1- (4-morpholinyl) ethanol, 4-acetylmorpholine, 3- (N-morpholino) -1,2-propanediol, 1,4-dimethylpiperazine, Examples include 1,4-diazabicyclo [2.2.2] octane and Nt-amyloxycarbonyl-4-hydroxypiperidine. Of these, Nt-amyloxycarbonyl-4-hydroxypiperidine is preferred.

  Further, as the [D] acid diffusion control agent, a photodisintegratable base that is exposed to light and generates a weak acid by exposure can also be used. The photodegradable base generates an acid in the exposed portion to increase the insolubility of the [A] polymer in the developer, and as a result, suppresses the roughness of the exposed portion surface after development. On the other hand, in the unexposed area, a high acid capturing function by anions is exhibited and functions as a quencher, and the acid diffused from the exposed area is captured. That is, since it functions as a quencher only in the unexposed area, the contrast of the deprotection reaction is improved, and as a result, the resolution can be further improved. As an example of the photodegradable base, there is an onium salt compound that is decomposed by exposure and loses acid diffusion controllability. Examples of the onium salt compound include a sulfonium salt compound represented by the following formula (D1) and an iodonium salt compound represented by the following formula (D2).

In the formula (D1) and Formula ^(D2), independently R 15 ^{to R 19} are each a hydrogen atom, an alkyl group, an alkoxy group, a hydroxyl group, a halogen atom or _-SO 2 -R ^C. R ^C is an alkyl group, a cycloalkyl group, an alkoxy group or an aryl group. Z ⁻ is OH ⁻ , R ²⁰ —COO ⁻ , R ^D —SO ₂ —N ^— —R ²⁰ , R ²⁰ —SO ₃ ^— or an anion represented by the following formula (D3). R ²⁰ is a linear or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an alkaryl group having 7 to 30 carbon atoms. Some or all of the hydrogen atoms of the alkyl group, cycloalkyl group, aryl group and alkaryl group may be substituted. ^RD is a C1-C10 linear or branched alkyl group or a C3-C20 cycloalkyl group which may have a substituent. Some or all of the hydrogen atoms of the alkyl group and cycloalkyl group may be substituted with fluorine atoms. However, when Z ⁻ is R ²⁰ —SO ₃ ^— , a fluorine atom is not bonded to a carbon atom to which SO ₃ ^— is bonded.

In said formula (D3), R < ²¹ > is a C1-C12 linear or branched alkyl group by which some or all of a hydrogen atom may be substituted by the fluorine atom, or C1-C12 These are linear or branched alkoxy groups. u is an integer of 0-2.

  The content of the [D] acid diffusion controller in the photoresist composition used in the pattern forming method is preferably less than 20 parts by mass and more preferably less than 10 parts by mass with respect to 100 parts by mass of the [A] polymer. preferable. [D] By setting the content of the acid diffusion control agent in the specific range, the sensitivity as a resist is easily maintained. These [D] acid diffusion inhibitors may be used alone or in combination of two or more.

<[E] solvent>
The photoresist composition usually contains a solvent. Examples of the solvent include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydrocarbon solvents, and mixed solvents thereof.

Examples of alcohol solvents include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, tert-butanol, n-pentanol, i-pentanol, 2-methylbutanol, sec-pentanol, tert-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, 3-heptanol, n-octanol, 2-ethylhexanol , Sec-octanol, n-nonyl alcohol, 2,6-dimethyl-4-heptanol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadeci Monoalcohol solvents such as alcohol, furfuryl alcohol, phenol, cyclohexanol, methylcyclohexanol, 3,3,5-trimethylcyclohexanol, benzyl alcohol, diacetone alcohol;
Ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 2,4-heptanediol, 2 -Polyhydric alcohol solvents such as ethyl-1,3-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethylbutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol Monomethyl ether, dipropylene glycol monoethyl ether, polyhydric alcohol partial ether solvents such as dipropylene glycol monopropyl ether.

  Examples of ether solvents include diethyl ether, dipropyl ether, dibutyl ether, diphenyl ether and the like.

  Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, diethyl ketone, methyl-i-butyl ketone, methyl-n-pentyl ketone, ethyl-n-butyl ketone, methyl-n- Examples include ketone solvents such as hexyl ketone, di-i-butyl ketone, trimethylnonanone, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone, acetophenone, and the like. .

  Examples of the amide solvents include N, N′-dimethylimidazolidinone, N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropionamide, N-methylpyrrolidone and the like can be mentioned.

  Examples of ester solvents include diethyl carbonate, propylene carbonate, methyl acetate, ethyl acetate, γ-butyrolactone, γ-valerolactone, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, sec sec -Butyl, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methyl pentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, n-nonyl acetate, acetoacetic acid Methyl, ethyl acetoacetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol acetate Non-n-butyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, glycol diacetate Methoxytriglycol acetate, ethyl propionate, n-butyl propionate, i-amyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate, Examples include diethyl malonate, dimethyl phthalate, and diethyl phthalate.

Examples of hydrocarbon solvents include n-pentane, i-pentane, n-hexane, i-hexane, n-heptane, i-heptane, 2,2,4-trimethylpentane, n-octane, i-octane, and cyclohexane. , Aliphatic hydrocarbon solvents such as methylcyclohexane;
Fragrances such as benzene, toluene, xylene, mesitylene, ethylbenzene, trimethylbenzene, methylethylbenzene, n-propylbenzene, i-propylbenzene, diethylbenzene, i-butylbenzene, triethylbenzene, di-i-propylbenzene, n-amylnaphthalene Group hydrocarbon solvents and the like.

  Of these, propylene glycol monomethyl ether acetate and cyclohexanone are preferred. These solvents may be used alone or in combination of two or more.

<Other optional components>
The photoresist composition can contain a surfactant, an alicyclic skeleton-containing compound, a sensitizer, and the like as other optional components. In addition, the said photoresist composition may contain only 1 type of said other arbitrary components, respectively, and may contain 2 or more types.

[Surfactant]
The surfactant has an effect of improving applicability, striation, developability and the like of the photoresist composition used in the pattern forming method.

[Alicyclic skeleton-containing compound]
The alicyclic skeleton-containing compound has the effect of improving the dry etching resistance, pattern shape, adhesion to the substrate, and the like of the photoresist composition used in the pattern forming method.

[Sensitizer]
The sensitizer exhibits the effect of increasing the amount of acid generated from the [B] acid generator, and has the effect of improving the “apparent sensitivity” of the photoresist composition used in the pattern forming method. .

<Method for preparing photoresist composition>
The photoresist composition contains, for example, [A] polymer, [B] acid generator, [C] water-repellent polymer additive, [D] acid diffusion controller and other optional components in [E] solvent. It can be prepared by mixing at a predetermined ratio. Moreover, the said photoresist composition can be prepared and used in the state melt | dissolved or disperse | distributed to the appropriate [E] solvent.

<Method for forming resist pattern>
The method for forming a resist pattern of the present invention includes
(1) a step of forming a resist film using the photoresist composition (hereinafter also referred to as “step (1)”),
(2) a step of exposing the resist film (hereinafter also referred to as “step (2)”); and (3) a step of developing the exposed resist film (hereinafter also referred to as “step (3)”).
Have Hereinafter, each process is explained in full detail.

  According to the resist pattern forming method, it is possible to form a resist pattern that sufficiently satisfies the resolution and is excellent in MEEF and CDU by using the photoresist composition. Therefore, even with radiation such as KrF excimer laser, ArF excimer laser, EUV, etc., it is possible to form a fine pattern from the photoresist composition with high accuracy and stability, and further miniaturization is expected in the future. It can be suitably used for manufacturing semiconductor devices.

[Step (1)]
In this step, the photoresist composition or a solution of the photoresist composition obtained by dissolving the photoresist composition in a solvent is applied to a silicon wafer, silicon dioxide, by coating means such as spin coating, cast coating, and roll coating. In the photoresist composition, it is applied on a substrate such as a wafer coated with an antireflection film so as to have a predetermined film thickness, and in some cases, it is usually pre-baked (PB) at a temperature of about 70 ° C. to 160 ° C. The solvent is volatilized to form a resist film.

[Step (2)]
In this step, the resist film formed in the step (1) is exposed by irradiation with radiation (in some cases through an immersion medium such as water). At this time, radiation is irradiated through a mask having a predetermined pattern. The radiation is appropriately selected from visible light, ultraviolet light, far ultraviolet light, X-rays, charged particle beams, EUV, etc. according to the line width of the target pattern. Among these, far ultraviolet rays represented by ArF excimer laser (wavelength 193 nm) and KrF excimer laser (wavelength 248 nm) are preferable, and light sources capable of forming finer patterns such as EUV (extreme ultraviolet ray, wavelength 13.5 nm) are preferred. Even if it exists, it can be used conveniently. Subsequently, it is preferable to perform post-exposure baking (PEB). This PEB makes it possible to smoothly proceed with elimination of the acid dissociable group of the [A] polymer. The heating condition of PEB can be appropriately selected depending on the composition of the photoresist composition, but is usually about 50 ° C to 180 ° C.

[Step (3)]
In this step, a resist pattern is formed by developing the exposed resist film with a developer. After development, it is common to wash with water, an organic solvent or the like and dry. As a developing solution, there are a case where an alkaline aqueous solution is used and a case where an organic solvent is used. In general, when an alkaline aqueous solution is used, the exposed portion is dissolved in the developer, and the resulting resist pattern is a positive type. Moreover, when using an organic solvent, a low exposure part and an unexposed part melt | dissolve in a developing solution, and the resist pattern obtained becomes a negative type.
Examples of the alkaline aqueous solution include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, Ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo- [5.4.0] -7-undecene, 1,5-diazabicyclo- [4. 3.0] -5 aqueous solution in which at least one alkaline compound such as 5-nonene is dissolved. Among these, a TMAH aqueous solution is preferable.

  Examples of the organic solvent include alcohol solvents, ether solvents, ketone organic solvents, amide solvents, ester organic solvents, and hydrocarbon solvents. Examples of these organic solvents include the same solvents as those exemplified as the [E] solvent contained in the photoresist composition.

  Of these, ester solvents, ketone solvents and ether solvents are preferable, ester solvents and ether solvents are more preferable, and ester solvents are more preferable. Specifically, anisole, n-butyl acetate, isopropyl acetate, i-pentyl acetate, methyl ethyl ketone, methyl-n-butyl ketone and methyl-n-pentyl ketone are preferred, and anisole, n-butyl acetate, and methyl-n-pentyl are preferred. Ketones are more preferred, anisole and n-butyl acetate are more preferred, and n-butyl acetate is particularly preferred. These organic solvents may be used alone or in combination of two or more.

  In the case of performing immersion exposure, before the step (2), in order to protect the direct contact between the immersion liquid and the resist film, an immersion liquid insoluble immersion protective film is formed on the resist film. It may be provided. As the protective film for immersion, a solvent-peeling protective film that peels off with a solvent before the step (3) (see, for example, JP-A-2006-227632), a developer that peels off simultaneously with the development in the step (3) Any of peelable protective films (for example, see WO2005-069096, WO2006-035790, etc.) may be used.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The ¹³ C-NMR analysis was measured using JNM-EX270 (manufactured by JEOL).

  The structures of monomers used in the synthesis of [A] polymer, polymer for comparative example corresponding to [A] polymer, and [C] water-repellent polymer additive described later are shown below.

<[A] Synthesis of polymer>
[Synthesis Example 1]
22.45 g (25 mol%) of the above compound (M-1) giving structural unit (II) and 30.01 g (25 mol%) of compound (M-2), compound (M-3) giving structural unit (III) ) 29.81 g (35 mol%) and 17.73 g (15 mol%) of the compound (M-5) which gives the structural unit (I) were dissolved in 200 g of 2-butanone, and 3.76 g of AIBN (5 mol%) ) Was added to prepare a monomer solution. A 1,000 mL three-necked flask charged with 100 g of 2-butanone was purged with nitrogen for 30 minutes. After purging with nitrogen, the reaction vessel was heated to 80 ° C. with stirring, and the monomer solution was added to the flask using a dropping funnel. It was added dropwise over time. The polymerization start was carried out for 6 hours with the start of dropping as the polymerization start time. After completion of the polymerization, the polymerization solution was cooled with water to 30 ° C. or less, poured into 2,000 g of methanol, and the precipitated white powder was separated by filtration. The filtered white powder was dispersed in 400 g of methanol and washed in the form of a slurry, followed by filtration, followed by filtration twice, followed by vacuum drying at 50 ° C. for 17 hours to obtain a white powder copolymer (A- 1) was obtained. Mw of (A-1) is 6,870, Mw / Mn = 1.47, and as a result of ¹³ C-NMR analysis, compound (M-1), compound (M-2), compound (M-3) ) And the content of each structural unit derived from the compound (M-5) was 24.7: 25.7: 34.4: 15.2 (mol%).

[Synthesis Example 2]
22.45 g (25 mol%) of the above compound (M-1) giving structural unit (II) and 30.01 g (25 mol%) of compound (M-2), compound (M-3) giving structural unit (III) ) 29.81 g (35 mol%) and 17.73 g (15 mol%) of the compound (M-5) giving the structural unit (I) were dissolved in 200 g of 2-butanone, and 7.51 g of AIBN (10 mol%) was dissolved. ) Was added to prepare a monomer solution. A 1,000 mL three-necked flask charged with 100 g of 2-butanone was purged with nitrogen for 30 minutes. After purging with nitrogen, the reaction vessel was heated to 80 ° C. with stirring, and the monomer solution was added to the flask using a dropping funnel. It was added dropwise over time. The polymerization start was carried out for 6 hours with the start of dropping as the polymerization start time. After completion of the polymerization, the polymerization solution was cooled with water to 30 ° C. or less, poured into 2,000 g of methanol, and the precipitated white powder was separated by filtration. The filtered white powder was dispersed in 400 g of methanol and washed in the form of a slurry, followed by filtration, followed by filtration twice, followed by vacuum drying at 50 ° C. for 17 hours to obtain a white powder copolymer (A- 2) was obtained. Mw of (A-2) is 5,020, Mw / Mn = 1.31, and as a result of ¹³ C-NMR analysis, compound (M-1), compound (M-2), compound (M-3) ) And the content of each structural unit derived from the compound (M-5) was 24.7: 25.8: 34.2: 15.3 (mol%).

[Synthesis Example 3]
22.45 g (25 mol%) of the above compound (M-1) giving structural unit (II) and 30.01 g (25 mol%) of compound (M-2), compound (M-3) giving structural unit (III) ) 29.81 g (35 mol%) and 17.73 g (15 mol%) of the compound (M-5) giving the structural unit (I) were dissolved in 200 g of 2-butanone, and 13.52 g of AIBN (18 mol%) ) Was added to prepare a monomer solution. A 1,000 mL three-necked flask charged with 100 g of 2-butanone was purged with nitrogen for 30 minutes. After purging with nitrogen, the reaction vessel was heated to 80 ° C. with stirring, and the monomer solution was added to the flask using a dropping funnel. It was added dropwise over time. The polymerization start was carried out for 6 hours with the start of dropping as the polymerization start time. After completion of the polymerization, the polymerization solution was cooled with water to 30 ° C. or less, poured into 2,000 g of methanol, and the precipitated white powder was separated by filtration. The filtered white powder was dispersed in 400 g of methanol and washed in the form of a slurry, followed by filtration, followed by filtration twice, followed by vacuum drying at 50 ° C. for 17 hours to obtain a white powder copolymer (A- 3) was obtained. Mw of (A-3) is 3,570 and Mw / Mn = 1.24. As a result of ¹³ C-NMR analysis, compound (M-1), compound (M-2), compound (M-3) ) And the content of each structural unit derived from the compound (M-5) was 24.6: 25.8: 34.4: 15.2 (mol%).

[Synthesis Examples 4 to 8]
Polymers (a-1) to (a-5) were obtained in the same manner as in Synthesis Example 1 except that the types and amounts of monomers listed in Table 1 were used. In addition, Table 1 shows the content of each structural unit, Mw, Mw / Mn ratio, and yield (%) of each polymer obtained.

<Synthesis of [C] water-repellent polymer additive>
[Synthesis Example 9]
37.41 g (40 mol%) of the above compound (M-7) and 62.59 g (60 mol%) of the compound (M-8) were dissolved in 100 g of 2-butanone, and 4.79 g (7 mol%) of AIBN was added. A monomer solution was prepared. A 1,000 mL three-necked flask charged with 100 g of 2-butanone was purged with nitrogen for 30 minutes. After purging with nitrogen, the reaction vessel was heated to 80 ° C. with stirring, and the monomer solution was added to the flask using a dropping funnel. It was added dropwise over time. The polymerization start was carried out for 6 hours with the start of dropping as the polymerization start time. After completion of the polymerization, the polymerization solution was cooled with water and cooled to 30 ° C. or lower. The polymerization solution was concentrated under reduced pressure using an evaporator until the weight of the polymerization solution reached 150 g. Thereafter, the concentrated solution was poured into a mixed solution of 760 g of methanol and 40 g of water to precipitate a slime-like white solid. The liquid part was removed by decantation, and the recovered solid was vacuum dried at 50 ° C. for 17 hours to obtain a white powder copolymer (C-1) (47 g, yield 47%). Mw of (C-1) is 3,700 and Mw / Mn is 1.40. As a result of ¹³ C-NMR analysis, the content of each structural unit of compound (M-7) and compound (M-8) is 42.5: 57.5 (mol%).

<Preparation of photoresist composition>
[Example 1]
[A] 100 parts by mass of copolymer (A-1) as a polymer, [B] 9 parts by mass of (B-1) as an acid generator, [C] (C- as a water-repellent polymer additive 1) 3 parts by mass, (D-1) 2.5 parts by mass as an acid diffusion controller, (E-1) 1770 parts by mass, (E-2) 760 parts by mass and (E -3) 200 parts by mass was added, and each component was mixed to obtain a uniform solution. Then, the positive photoresist composition I was prepared by filtering using a membrane filter having a pore size of 200 nm (solid content concentration: about 4%).

[Examples 2-6 and Comparative Examples 1-7]
Photoresist compositions II to VI and i to vii were prepared in the same manner as in Example 1 except that the types and amounts of each component shown in Table 2 were used. In Table 2, “-” indicates that the corresponding component was not used.

  The [B] acid generator, [D] acid diffusion controller, [E] solvent, and additives used in the preparation of each Example and Comparative Example are as follows.

<[B] Acid generator>
B-1: Triphenylsulfonium 1,1,2,2-tetrafluoro-6- (1-adamantanecarbonyloxy) hexane-1-sulfonate (compound represented by the following formula (B-1))

([D] acid diffusion controller)
D-1: Triphenylsulfonium salicylate (compound represented by the following formula (D-1))

([E] solvent)
E-1: Propylene glycol monomethyl ether acetate E-2: Cyclohexanone E-3: γ-butyrolactone

[Examples 7 to 9 and Comparative Examples 8 to 12]
<Formation of resist pattern 1>
Photoresist compositions I to III and iv obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were applied on a 12-inch silicon wafer on which a lower antireflection film (ARC66, manufactured by Nissan Chemical Co., Ltd.) was formed. Then, PB was performed for 60 seconds at the temperature shown in Table 3 to form a resist film having a thickness of 100 nm. Next, this resist film was exposed through a mask pattern using an ArF excimer laser immersion exposure apparatus (NSR S610C, manufactured by NIKON) under the conditions of NA = 1.3, ratio = 0.800, and annular. After the exposure, PEB was performed for 60 seconds at the temperature shown in Table 3. Thereafter, the resist film was developed with a 2.38 mass% tetramethylammonium hydroxide aqueous solution, washed with water, and dried to form a positive resist pattern.
The resist pattern formed as described above was evaluated by the following evaluation method 1. The results are shown in Table 3.

[Examples 10 to 12 and Comparative Examples 13 and 14]
<Formation of resist pattern 2>
Photoresist compositions IV to VI and vi and vii obtained in Examples 4 to 6 and Comparative Examples 6 and 7 were applied on a 12-inch silicon wafer on which a lower antireflection film (ARC66, manufactured by Nissan Chemical Co., Ltd.) was formed. Then, PB was performed for 60 seconds at the temperature shown in Table 3 to form a resist film having a thickness of 100 nm. Next, the upper layer film-forming composition described in Example 1 of WO2008 / 047678 was spin-coated on the formed resist film, and the upper layer film having a thickness of 90 nm was formed by heating at 90 ° C. for 60 seconds. . This resist film was exposed through a mask pattern using an ArF excimer laser immersion exposure apparatus (NSR S610C, manufactured by NIKON) under the conditions of NA = 1.3, ratio = 0.800, and annular. After the exposure, PEB was performed for 60 seconds at the temperature shown in Table 3. Thereafter, the resist film was developed with a 2.38 mass% tetramethylammonium hydroxide aqueous solution, washed with water, and dried to form a positive resist pattern.
The resist pattern formed as described above was evaluated by the following evaluation method 1. The results are shown in Table 3.

<Evaluation method 1>
[MEEF]
The portion of the pattern after reduction projection exposed through the mask pattern for pattern formation of 65 nm holes and 95 nm pitches formed an exposure amount for forming a hole with a diameter of 55 nm as the optimum exposure amount (Eop). Next, using the mask patterns having the hole diameters of 63 nm, 64 nm, 65 nm, 66 nm, and 67 nm at the optimum exposure amount, respectively, a hole pattern is formed, and the hole diameter formed in the resist film is measured by a length measurement SEM ( Measured by Hitachi, Ltd. (CG4000). At this time, the slope of the straight line when the size (nm) of the mask pattern was plotted on the horizontal axis and the hole diameter (nm) formed in the resist film using each mask pattern was plotted on the vertical axis was calculated as MEEF. When MEEF was 3.5 or less, it was evaluated as good.

[CDU (nm)]
A total of 30 hole patterns with a diameter of 55 nm formed by the Eop were measured, and the value of 3σ of the average deviation of the 30 measured values was defined as CDU (nm). When CDU was 4.5 nm or less, it was evaluated as good.

[Resolution (nm)]
When the pattern after reduction projection is exposed through a mask pattern having a 65 nm hole and 95 nm pitch at an exposure amount equal to or less than Eop, the minimum dimension (nm) of the hole pattern obtained with the decrease in the exposure amount is defined as resolution. did. When the resolution was 50 nm or less, it was evaluated as good.

  As is clear from the results shown in Table 3, it was found that the resist pattern formed from the photoresist composition was excellent in MEEF, CDU and resolution. In this example, ArF is used as the exposure light source. However, even when a short wavelength radiation such as EUV is used, the obtained fine pattern has similar resist characteristics and has an equivalent evaluation. The result is considered to be obtained.

[Examples 13 to 15 and Comparative Examples 15 to 19]
Photoresist compositions I to III and iv obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were applied on a 12-inch silicon wafer on which a lower antireflection film (ARC66, manufactured by Nissan Chemical Co., Ltd.) was formed. Then, PB was performed for 60 seconds at the temperature shown in Table 4 to form a resist film having a thickness of 100 nm. Next, an ArF excimer laser immersion exposure apparatus (NSR S610C, manufactured by Nikon) was used for this resist film, and reduced projection was performed under the conditions of NA = 1.3, iNA = 1.27, ratio = 0.800, and Crosspore. The subsequent pattern was exposed through a mask pattern having 58 nm holes and 86 nm pitch. After the exposure, PEB was performed at the temperature shown in Table 4 for 60 seconds. Thereafter, paddle development with butyl acetate (30 seconds) was performed, followed by drying to form a negative resist pattern.
The resist pattern formed as described above was evaluated by the following evaluation method 2. The results are shown in Table 4. Note that “-” in Table 4 indicates that a 43 nm hole pattern could not be formed.

<Evaluation method 2>
[MEEF]
The exposure amount at which the portion after the reduced projection pattern was exposed through the mask pattern for forming the pattern of 58 nm holes and 86 nm pitch formed 43 nm holes was determined as the optimum exposure amount (Eop). Next, at the above Eop, a hole pattern with a pitch of 86 nm was formed using a mask pattern having a hole pattern size after reduced projection of 59 nm, 58.5 nm, 57.5 nm, and 57 nm, respectively, and formed on the resist film. The hole size was measured with a length measurement SEM (Hitachi, CG4000). At this time, the size (nm) of the hole pattern after reduced projection exposure is plotted on the horizontal axis, and the size of the hole pattern (nm) formed on the resist film on the substrate after reduced projection exposure is plotted on the vertical axis. The slope was calculated as MEEF. The case where MEEF was 6.0 or less was judged as “good”.

[CDU (nm)]
The hole pattern diameter of 43 nm formed by Eop was measured at 30 arbitrary points, and the 3σ value of the average deviation of the measured values was defined as CDU (nm). The case where CDU was 5.0 nm or less was judged as “good”.

[Resolution]
The minimum dimension (nm) of the hole pattern obtained with an increase in the exposure amount when the pattern after reduction projection exposure is exposed through a mask pattern having a pitch of 58 nm and 86 nm pitch with an exposure amount equal to or greater than Eop. It was. The case where the resolution was 35 nm or less was judged as “good”.

[DOF (μm)]
The DOF was defined as the depth of focus (μm) so that the hole size formed by the Eop was within ± 10% of 43 nm. A case where the DOF was 0.20 μm or more was judged as “good”.

  As is clear from the results shown in Table 4, it was found that the negative resist pattern formed from the photoresist composition using an organic solvent is excellent in MEEF, CDU, resolution and DOF.

  The photoresist composition and the resist pattern forming method of the present invention can form a resist pattern excellent in MEEF, CDU, DOF and resolution. Therefore, a fine pattern can be formed with high accuracy and stability by a pattern forming method using the photoresist composition with respect to radiation such as KrF excimer laser or ArF excimer laser. The photoresist composition and the pattern forming method using the photoresist composition can be suitably used for manufacturing semiconductor devices that are expected to be further miniaturized in the future.

Claims (7)

[A] a polymer having a structural unit (I) represented by the following formula (1) and having a weight average molecular weight of 3,000 to 8,000, and [B] an acid generator,
Containing a photoresist composition.

(In Formula (1), R ¹ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ² is an oxygen atom, a sulfur atom, or a divalent chain carbon atom having 1 to 5 carbon atoms. R ³ is a monovalent organic group, a is an integer of 0 to 2, provided that when a is 2, a plurality of R ³ are the same. But it may be different.)   [A] The photoresist composition according to claim 1, wherein the polymer further has a structural unit (II) containing an acid dissociable group.   [A] The photoresist composition according to claim 1 or 2, wherein the polymer further comprises a structural unit (III) containing at least one group selected from the group consisting of a lactone group and a cyclic carbonate group.   [A] The photoresist composition according to claim 1, wherein the content of the structural unit (I) in the polymer is 5 mol% or more and 20 mol% or less.   [B] The photoresist composition according to any one of claims 1 to 4, wherein the acid generator has an alicyclic structure having 8 to 30 carbon atoms.   [C] The photoresist composition according to any one of claims 1 to 5, further comprising a water-repellent polymer additive containing a fluorine atom. (1) A step of forming a resist film using the photoresist composition according to any one of claims 1 to 6,
(2) A resist pattern forming method comprising: exposing the resist film; and (3) developing the exposed resist film.