JP2006349800A - Positive resist composition and method for forming resist pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive resist composition for forming a resist pattern with excellent resolution, and to provide a method for forming a resist pattern. <P>SOLUTION: The positive resist composition contains a resin component (A) the alkali solubility of which is increased by an effect of an acid and an acid generator component (B) which generates an acid by exposure, wherein the resin component (A) is a mixture of a copolymer (A1) having a structural unit (a1) derived from an acrylic acid ester having a cyclic acid-dissociative solubility-inhibiting group and a copolymer (A1') having a structural unit (a1') derived from an acrylic acid ester having a branched chain acid-dissociative solubility-inhibiting group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

In lithography technology, for example, a resist film made of a resist material is formed on a substrate, and the resist film is selectively exposed to light such as light or an electron beam through a mask on which a predetermined pattern is formed. And a development process is performed to form a resist pattern having a predetermined shape on the resist film. A resist material in which the exposed portion changes to a property that dissolves in the developer is referred to as a positive type, and a resist material that changes to a property in which the exposed portion does not dissolve in the developer is referred to as a negative type.
In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, pattern miniaturization has been rapidly progressing due to advances in lithography technology.
As a technique for miniaturization, the wavelength of an exposure light source is generally shortened. Specifically, conventionally, ultraviolet rays typified by g-line and i-line have been used, but at present, mass production of semiconductor elements using a KrF excimer laser or an ArF excimer laser has started. In addition, studies have been made on F ₂ excimer lasers, electron beams, EUV (extreme ultraviolet rays), X-rays, and the like having shorter wavelengths than these excimer lasers.

Resist materials are required to have a sensitivity to these exposure light sources and a resolving power capable of reproducing a pattern with fine dimensions. As a resist material satisfying such requirements, a chemically amplified resist composition containing a base resin whose alkali solubility is changed by the action of an acid and an acid generator that generates an acid upon exposure is used. For example, a positive chemically amplified resist contains, as a base resin, a resin whose alkali solubility is increased by the action of an acid and an acid generator. When a resist pattern is formed, an acid is generated from the acid generator by exposure. The exposed part becomes alkali-soluble.
At present, as a base resin of a chemically amplified resist, for example, when an ArF excimer laser (198 nm) is used as an exposure light source, a resin having a structural unit derived from a (meth) acrylic ester having high transparency with respect to the ArF excimer laser (Acrylic resin) is generally used. As such an acrylic resin, for example, in the case of a positive type, a resin having a cyclic acid dissociable, dissolution inhibiting group in consideration of dry etching resistance, for example, a carboxy group of (meth) acrylic acid is 2-alkyl- Resins having a structural unit derived from a (meth) acrylic acid tertiary ester compound protected with a tertiary aliphatic polycyclic group such as a 2-adamantyl group are mainly used (for example, Patent Document 1). reference).
Japanese Patent No. 2881969

Currently, in order to cope with the miniaturization of semiconductor elements as described above, further improvement in resolution is required for resist materials.
However, conventional resists that use a resin having a cyclic acid dissociable, dissolution inhibiting group as described above as a base resin have a limit in improving the resolution. For example, a resist pattern faithful to the mask pattern can be reproduced sufficiently. There are problems such as being unable to do so.
This invention is made | formed in view of the said situation, Comprising: It aims at providing the positive resist composition and resist pattern formation method which can form the resist pattern excellent in resolving power.

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by using two kinds of copolymers each having an acid dissociable, dissolution inhibiting group having a specific structure. Was completed.
That is, the first aspect of the present invention is a positive resist composition containing a resin component (A) whose alkali solubility is increased by the action of an acid and an acid generator component (B) which generates an acid upon exposure. There,
The resin component (A) is a copolymer (A1) having a structural unit (a1) derived from an acrylate ester containing a cyclic acid dissociable, dissolution inhibiting group, and a branched acid dissociable, dissolution inhibiting group. And a copolymer (A1 ′) having a structural unit (a1 ′) derived from an acrylate ester containing a positive resist composition.
The second aspect of the present invention includes a step of forming a resist film on a substrate using the positive resist composition of the first aspect, a step of exposing the resist film, and developing the resist film. A resist pattern forming method including a step of forming a resist pattern.

In the present specification and claims, the “structural unit” means a monomer unit (monomer unit) constituting a resin component (polymer compound).
“Exposure” is a concept that includes general irradiation of radiation.

  According to the positive resist composition and the resist pattern forming method of the present invention, a resist pattern having excellent resolution can be formed.

≪Positive resist composition≫
The positive resist composition of the present invention comprises a resin component (A) whose alkali solubility is increased by the action of an acid (hereinafter referred to as “component (A)”) and an acid generator component (which generates an acid upon irradiation with radiation) ( B) (hereinafter referred to as component (B)).
In the positive resist composition of the present invention, the component (A) is alkali-insoluble before exposure, and when an acid generated from the component (B) acts upon exposure, the acid dissociable, dissolution inhibiting group dissociates. As a result, the alkali solubility of the entire component (A) is increased and the alkali-insoluble is changed to alkali-soluble. Therefore, when a resist film obtained by using a positive resist composition is selectively exposed in the formation of a resist pattern, the exposed portion turns alkali-soluble, while the unexposed portion remains alkali-insoluble. Therefore, alkali development can be performed.

<(A) component>
In the present invention, the component (A) includes a copolymer (A1) having a structural unit (a1) derived from an acrylate ester containing a cyclic acid dissociable dissolution inhibiting group, and a branched acid dissociable dissolution. It is a mixture with a copolymer (A1 ′) having a structural unit (a1 ′) derived from an acrylate ester containing an inhibitor group.

In the present specification and claims, the “structural unit derived from an acrylate ester” means a structural unit formed by cleavage of an ethylenic double bond of an acrylate ester.
“Acrylic acid esters” include those in which a hydrogen atom is bonded to the carbon atom at the α-position, and those in which a substituent (atom or group other than a hydrogen atom) is bonded to the carbon atom in the α-position. Include concepts. Examples of the substituent include a halogen atom, a lower alkyl group, and a halogenated lower alkyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable.
The α-position (α-position carbon atom) of a structural unit derived from an acrylate ester is a carbon atom to which a carbonyl group is bonded unless otherwise specified.
The “alkyl group” includes linear, branched and cyclic monovalent saturated hydrocarbon groups unless otherwise specified.
The “lower alkyl group” is an alkyl group having 1 to 5 carbon atoms.
In the acrylate ester, as the lower alkyl group as a substituent at the α-position, specifically, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, Examples include lower linear or branched alkyl groups such as isopentyl group and neopentyl group.
In the present invention, the α-position of the acrylate ester is preferably a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group, and a hydrogen atom, a fluorine atom, a lower alkyl group or a fluorine atom. A lower alkyl group is more preferable, and a hydrogen atom or a methyl group is most preferable in terms of industrial availability.

[Copolymer (A1)]
・ Structural unit (a1)
The acid dissociable, dissolution inhibiting group in the structural unit (a1) has an alkali dissolution inhibiting property that makes the entire copolymer (A1) insoluble in alkali before dissociation, and the entire copolymer (A1) is alkalinized after dissociation. It changes to solubility.
In the structural unit (a1), the acid dissociable, dissolution inhibiting group is not particularly limited as long as it is cyclic. Can be used.
Here, the “cyclic acid dissociable, dissolution inhibiting group” means an acid dissociable, dissolution inhibiting group having a cyclic group in its structure.
Examples of the cyclic acid dissociable, dissolution inhibiting group include a group forming a cyclic tertiary alkyl ester with a carboxy group of (meth) acrylic acid, or a group forming a cyclic alkoxyalkyl ester. The “(meth) acrylic acid ester” means one or both of an acrylic acid ester having a hydrogen atom bonded to the α-position and a methacrylic acid ester having a methyl group bonded to the α-position.

Here, the “tertiary alkyl ester” is an ester formed by replacing a hydrogen atom of a carboxy group with an alkyl group having a tertiary carbon atom, and the carbonyloxy group (—C ( A structure in which the tertiary carbon atom of the alkyl group is bonded to the oxygen atom at the terminal of O) -O-). In this tertiary alkyl ester, when an acid acts, the bond is broken between the oxygen atom at the terminal of the carbonyloxy group and the tertiary carbon atom.
The alkyl group may have a substituent.
Hereinafter, a group that is acid dissociable by constituting a carboxy group and a tertiary alkyl ester is referred to as a “tertiary alkyl ester type acid dissociable, dissolution inhibiting group” for convenience.
In addition, the “alkoxyalkyl ester” is an ester formed by substituting a hydrogen atom of a carboxy group with an alkoxyalkyl group, and oxygen at the terminal of the carbonyloxy group (—C (O) —O—). A structure in which the alkoxyalkyl group is bonded to an atom is shown. In this alkoxyalkyl ester, when an acid acts, the bond is cut between the oxygen atom at the terminal of the carbonyloxy group and the alkoxyalkyl group.

  As the structural unit (a1), one type selected from the group consisting of structural units represented by general formula (a1-0-1) shown below and structural units represented by general formula (a1-0-2) shown below. It is preferable to use the above.

（式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基を示し；Ｘ^１は環状の酸解離性溶解抑制基を示す。）

(In the formula, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group; X ¹ represents a cyclic acid dissociable, dissolution inhibiting group.)

（式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基を示し；Ｘ^２は環状の酸解離性溶解抑制基を示し；Ｙ^２はアルキレン基または脂肪族環式基を示す。）

Wherein R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group; X ² represents a cyclic acid dissociable, dissolution inhibiting group; Y ² represents an alkylene group or an aliphatic cyclic group. Show.)

In general formula (a1-0-1), R is the same as that mentioned as being bonded to the α-position of the acrylate ester.
X ¹ is not particularly limited as long as it is a cyclic acid dissociable, dissolution inhibiting group, and examples thereof include a cyclic alkoxyalkyl group, a cyclic tertiary alkyl ester type acid dissociable, dissolution inhibiting group, and the like. A cyclic tertiary alkyl ester type acid dissociable, dissolution inhibiting group is preferred. Examples of the cyclic tertiary alkyl ester type acid dissociable, dissolution inhibiting group include acid dissociable, dissolution inhibiting groups containing an aliphatic cyclic group.
Here, “aliphatic” in the claims and the specification is a relative concept with respect to aromatics, and is defined to mean a group, a compound, or the like that does not have aromaticity. The “aliphatic cyclic group” means a monocyclic group or polycyclic group having no aromaticity.
The “aliphatic cyclic group” in the structural unit (a1) may or may not have a substituent. Examples of the substituent include a lower alkyl group having 1 to 5 carbon atoms, a fluorine atom, a fluorinated lower alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, an oxygen atom (= O), and the like.
The basic ring structure excluding the substituent of the “aliphatic cyclic group” is not limited to a group consisting of carbon and hydrogen (hydrocarbon group), but is preferably a hydrocarbon group. The “hydrocarbon group” may be either saturated or unsaturated, but is usually preferably saturated. A polycyclic group is preferred.
Specific examples of such aliphatic cyclic groups include, for example, monocycloalkanes, bicycloalkanes, trialkyls which may or may not be substituted with a lower alkyl group, a fluorine atom or a fluorinated alkyl group. Examples include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as cycloalkane or tetracycloalkane. Specific examples include monocycloalkanes such as cyclopentane and cyclohexane, and groups obtained by removing one or more hydrogen atoms from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.

  Examples of the acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group include a group having a tertiary carbon atom on the ring skeleton of the aliphatic cyclic group. Specifically, 2-methyl- A 2-adamantyl group, a 2-ethyl-2-adamantyl group, and the like can be given. Alternatively, as a structural unit represented by the following general formula, a group having an aliphatic cyclic group such as an adamantyl group and a branched alkylene group having a tertiary carbon atom bonded thereto can be given.

［式中、Ｒは上記と同じであり、Ｒ^１５、Ｒ^１６はアルキル基（直鎖、分岐鎖状のいずれでもよく、好ましくは炭素数１〜５である）を示す。］

[Wherein, R is the same as described above, and R ¹⁵ and R ¹⁶ represent an alkyl group (which may be linear or branched, and preferably has 1 to 5 carbon atoms). ]

  Further, the cyclic alkoxyalkyl group is preferably a group represented by the following general formula.

（式中、Ｒ^２１、Ｒ^２２はそれぞれ独立してアルキル基または水素原子であり、Ｒ^２３は環状のアルキル基であるか、またはＲ^２１およびＲ^２３がアルキレン基であって、Ｒ^２１の末端の炭素原子とＲ^２３の末端の炭素原子とが結合して環を形成していてもよい。）

^(Wherein, R ^{21, R 22} are each independently an alkyl group or a hydrogen ^atom, or ^{R 23} is a cyclic alkyl group, or a ^{R 21} and ^{R 23} is an alkylene ^group, terminal of ^{R 21} And a carbon atom at the terminal of R ²³ may be bonded to form a ring.)

In R ²¹ and R ²² , the alkyl group preferably has 1 to 15 carbon atoms, may be linear or branched, and is preferably an ethyl group or a methyl group, and most preferably a methyl group. In particular, it is preferable that one of R ²¹ and R ²² is a hydrogen atom and the other is a methyl group.
The cyclic alkyl group for R ²³ preferably has 4 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10 carbon atoms. Specifically, one or more polycycloalkanes such as monocycloalkane, bicycloalkane, tricycloalkane, and tetracycloalkane, which may or may not be substituted with a fluorine atom or a fluorinated alkyl group, are included. Examples include a group excluding a hydrogen atom. Specific examples include monocycloalkanes such as cyclopentane and cyclohexane, and groups obtained by removing one or more hydrogen atoms from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Among them, a group obtained by removing one or more hydrogen atoms from adamantane is preferable.
In the above formula, R ²¹ and R ²³ are each independently an alkylene group having 1 to 5 carbon atoms, and the end of R ²³ may be bonded to the end of R ²¹ .
In this case, a cyclic group is formed by R ²¹ , R ²³ , the oxygen atom to which R ²³ is bonded, and the carbon atom to which the oxygen atom and R ²¹ are bonded. The cyclic group is preferably a 4- to 7-membered ring, and more preferably a 4- to 6-membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

In general formula (a1-0-2), R is the same as defined above. X ² is the same as X ¹ in formula (a1-0-1).
Y ² is an alkylene group having 1 to 4 carbon atoms or a divalent aliphatic cyclic group. As the aliphatic cyclic group, those similar to the description of the “aliphatic cyclic group” can be used except that a group in which two or more hydrogen atoms are removed is used.

  More specifically, examples of the structural unit (a1) include structural units represented by the following general formulas (a1-1) to (a1-4).

［上記式中、Ｘ’は環状の第３級アルキルエステル型酸解離性溶解抑制基を表し、Ｙは脂肪族環式基を表し；ｎは０または１〜３の整数を表し；ｍは０または１を表し；Ｒは前記と同じであり、Ｒ^１’、Ｒ^２’はそれぞれ独立して水素原子または炭素数１〜５の低級アルキル基を表す。］

[Wherein, X ′ represents a cyclic tertiary alkyl ester-type acid dissociable, dissolution inhibiting group, Y represents an aliphatic cyclic group; n represents 0 or an integer of 1 to 3; Or represents 1; R is as defined above, and R ¹ ′ and R ² ′ each independently represent a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms. ]

In the R ¹ ′ and R ² ′, at least one is preferably a hydrogen atom, and more preferably both are hydrogen atoms. n is preferably 0 or 1.

X ′ is the same as the cyclic tertiary alkyl ester type acid dissociable, dissolution inhibiting group exemplified in X ¹ above.
Examples of the aliphatic cyclic group for Y include the same groups as those exemplified above in the description of “aliphatic cyclic group”.

  Specific examples of the structural units represented by the general formulas (a1-1) to (a1-4) are shown below.

As the structural unit (a1), one type may be used alone, or two or more types may be used in combination. Among these, the structural unit represented by General Formula (a1-1) is preferable, and specifically, (a1-1-1) to (a1-1-6) or (a1-1-35) to (a1- It is more preferable to use at least one selected from structural units represented by 1-41).
Furthermore, as the structural unit (a1), in particular, those represented by the following general formula (a1-1-01) including the structural units of the formulas (a1-1-1) to (a1-1-4) And the following general formula (a1-1-02) including the structural units of the formulas (a1-1-36), (a1-1-38), (a1-1-39) and (a1-1-41) preferable.

（式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基を示し、Ｒ^１１は低級アルキル基を示す。）

(In the formula, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group, and R ¹¹ represents a lower alkyl group.)

（式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基を示し、Ｒ^１２は低級アルキル基を示す。ｈは１〜３の整数を表す）

(In the formula, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group, R ¹² represents a lower alkyl group, and h represents an integer of 1 to 3).

In general formula (a1-1-01), R is the same as defined above.
The lower alkyl group for R ^{11 is the same as} the lower alkyl group for R, and is preferably a methyl group or an ethyl group.

In general formula (a1-1-02), R is the same as defined above.
The lower alkyl group for R ^{12 is the same as} the lower alkyl group for R, preferably a methyl group or an ethyl group, and most preferably an ethyl group.
h is preferably 1 or 2, and most preferably 2.

  In the copolymer (A1), the proportion of the structural unit (a1) is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, based on all the structural units constituting the copolymer (A1). -50 mol% is more preferable, and 30-50 mol% is most preferable. By setting it to the lower limit value or more, a pattern can be obtained when the resist composition is used, and by setting it to the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a2)
The copolymer (A1) preferably has a structural unit (a2) derived from an acrylate ester having a lactone-containing monocyclic or polycyclic group in addition to the structural unit (a1).
When the lactone-containing monocyclic or polycyclic group of the structural unit (a2) is used for forming a resist film, the copolymer (A1) can be used to increase the adhesion of the resist film to the substrate, It is effective in increasing hydrophilicity.
Here, the lactone-containing monocyclic or polycyclic group refers to a cyclic group containing one ring (lactone ring) containing an —O—C (O) — structure. The lactone ring is counted as the first ring, and when it is only the lactone ring, it is called a monocyclic group, and when it has another ring structure, it is called a polycyclic group regardless of the structure.

As the structural unit (a2), any structural unit can be used without particular limitation as long as it has both such a lactone structure (—O—C (O) —) and a cyclic group.
Specifically, examples of the lactone-containing monocyclic group include groups in which one hydrogen atom has been removed from γ-butyrolactone. Examples of the lactone-containing polycyclic group include groups in which one hydrogen atom has been removed from a bicycloalkane, tricycloalkane, or tetracycloalkane having a lactone ring. In particular, a group obtained by removing one hydrogen atom from a lactone-containing tricycloalkane having the following structural formula is advantageous in that it is easily available industrially.

  More specifically, examples of the structural unit (a2) include structural units represented by general formulas (a2-1) to (a2-5) shown below.

［式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基であり、Ｒ’は水素原子、低級アルキル基、または炭素数１〜５のアルコキシ基であり、ｍは０または１の整数である。］

[Wherein, R is a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group, R ′ is a hydrogen atom, a lower alkyl group, or an alkoxy group having 1 to 5 carbon atoms, and m is 0 or It is an integer of 1. ]

In general formulas (a2-1) to (a2-5), R is the same as described above.
The lower alkyl group for R ′ is the same as the lower alkyl group for R in the structural unit (a1).
In general formulas (a2-1) to (a2-5), R ′ is preferably a hydrogen atom in view of industrial availability.
Among these, it is preferable to use at least one selected from general formulas (a2-1) to (a2-5), and at least one selected from general formulas (a2-1) to (a2-3). It is preferable to use more than one species.
Below, the specific structural unit of the said general formula (a2-1)-(a2-5) is illustrated.

  Among these, chemical formula (a2-1-1), (a2-1-2), (a2-2-1), (a2-2-2), (a2-3-1), (a2-3-) 2) It is preferable to use at least one selected from (a2-3-9) and (a2-3-10).

In the copolymer (A1), as the structural unit (a2), one type may be used alone, or two or more types may be used in combination.
5-60 mol% is preferable with respect to the sum total of all the structural units which comprise a copolymer (A1), and the ratio of the structural unit (a2) in a copolymer (A1) is 10-50 mol% more. Preferably, 20-50 mol% is more preferable. By making it the lower limit value or more, the effect of containing the structural unit (a2) can be sufficiently obtained, and by making it the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a3)
The copolymer (A1) is derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group in addition to the structural unit (a1) or in addition to the structural units (a1) and (a2). It is preferable to have the structural unit (a3). By having the structural unit (a3), the hydrophilicity of the copolymer (A1) is increased, the affinity with the developer is increased, the alkali solubility in the exposed area is improved, and the resolution is improved.
Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, and a hydroxyalkyl group in which a part of hydrogen atoms of an alkyl group is substituted with a fluorine atom. A hydroxyl group is particularly preferable.
Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group having 1 to 10 carbon atoms (preferably an alkylene group) and a polycyclic aliphatic hydrocarbon group (polycyclic group). . As the polycyclic group, for example, a resin for a resist composition for ArF excimer laser can be appropriately selected from among many proposed ones.
Among them, an aliphatic polycyclic group containing a hydroxyalkyl group in which a part of hydrogen atoms of a hydroxyl group, a cyano group, a carboxy group, or an alkyl group is substituted with a fluorine atom, and (α-lower alkyl) acrylic A structural unit derived from an acid ester is more preferred. Examples of the polycyclic group include groups in which one or more hydrogen atoms have been removed from bicycloalkane, tricycloalkane, tetracycloalkane, or the like. Specific examples include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane. Such a polycyclic group can be appropriately selected and used from among many proposed polymers (resin components) for resist compositions for ArF excimer lasers. Among these polycyclic groups, there are groups in which two or more hydrogen atoms have been removed from adamantane, groups in which two or more hydrogen atoms have been removed from norbornane, and groups in which two or more hydrogen atoms have been removed from tetracyclododecane. Industrially preferable.

  The structural unit (a3) is derived from a hydroxyethyl ester of acrylic acid when the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a linear or branched hydrocarbon group having 1 to 10 carbon atoms. When the hydrocarbon group is a polycyclic group, a structural unit represented by the following formula (a3-1), a structural unit represented by (a3-2), (a3-3) The structural unit represented by is mentioned as a preferable thing.

（式中、Ｒは前記に同じであり、ｊは１〜３の整数であり、ｋは１〜３の整数であり、ｔ’は１〜３の整数であり、ｌは１〜５の整数であり、ｓは１〜３の整数である。）

(Wherein R is the same as above, j is an integer of 1 to 3, k is an integer of 1 to 3, t 'is an integer of 1 to 3, and l is an integer of 1 to 5) And s is an integer of 1 to 3.)

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When j is 2, it is preferable that the hydroxyl group is bonded to the 3rd and 5th positions of the adamantyl group. When j is 1, it is preferable that the hydroxyl group is bonded to the 3-position of the adamantyl group.
j is preferably 1, and a hydroxyl group bonded to the 3rd position of the adamantyl group is particularly preferred.

  In formula (a3-2), k is preferably 1. The cyano group is preferably bonded to the 5th or 6th position of the norbornyl group.

  In formula (a3-3), t ′ is preferably 1. l is preferably 1. s is preferably 1. In these, a 2-norbornyl group or a 3-norbornyl group is preferably bonded to the terminal of the carboxy group of (α-lower alkyl) acrylic acid. The fluorinated alkyl alcohol is preferably bonded to the 5th or 6th position of the norbornyl group.

As the structural unit (a3), one type may be used alone, or two or more types may be used in combination.
In the copolymer (A1), the proportion of the structural unit (a3) is preferably 5 to 50% by mole, and 5 to 40% by mole with respect to all the structural units constituting the copolymer (A1). More preferably, 5-25 mol% is further more preferable.

・ Structural unit (a4)
The copolymer (A1) may contain other structural units (a4) other than the structural units (a1) to (a3) as long as the effects of the present invention are not impaired.
The structural unit (a4) is not particularly limited as long as it is another structural unit not classified into the structural units (a1) to (a3) described above, and is for ArF excimer laser, for KrF excimer laser (preferably ArF excimer laser). A number of conventionally known resins can be used for resist resins such as
As the structural unit (a4), for example, a structural unit derived from an acrylate ester containing a non-acid-dissociable aliphatic polycyclic group is preferable. Examples of the polycyclic group include those exemplified in the case of the structural unit (a1), and for ArF excimer laser and KrF excimer laser (preferably for ArF excimer laser). A number of hitherto known materials can be used as the resin component of the resist composition.
In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, a tetracyclododecanyl group, an isobornyl group, and a norbornyl group is preferable in terms of industrial availability. These polycyclic groups may be substituted with a linear or branched alkyl group having 1 to 5 carbon atoms.
Specific examples of the structural unit (a4) include those represented by the following general formulas (a4-1) to (a4-5).

（式中、Ｒは前記と同じである。）

(In the formula, R is as defined above.)

  The structural unit (a4) is not an essential component of the copolymer (A1), but when it is contained in the copolymer (A1), the total of all the structural units constituting the copolymer (A1). The structural unit (a4) is preferably contained in an amount of 1 to 30 mol%, preferably 10 to 20 mol%.

The copolymer (A1) can be obtained by polymerizing a monomer for deriving each structural unit by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN). it can.
In the copolymerization (A1), a chain transfer agent such as HS—CH ₂ —CH ₂ —CH ₂ —C (CF ₃ ) ₂ —OH is used in combination in the above polymerization. it may be introduced -C _{(CF 3)} 2 -OH group at the terminal. As described above, a copolymer introduced with a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group is substituted with a fluorine atom reduces development defects and LER (line edge roughness: uneven unevenness of line side walls). It is effective in reducing

The mass average molecular weight (Mw) (polystyrene conversion standard by gel permeation chromatography) of the copolymer (A1) is not particularly limited, but is preferably 2000 to 50000, more preferably 3000 to 30000, and more preferably 5000 to 20000. Is most preferred. When it is smaller than the upper limit of this range, it has sufficient solubility in a resist solvent to be used as a resist, and the dry etching resistance and resist pattern cross-sectional shape that are larger than the lower limit of this range are good.
Further, the dispersity (Mw / Mn) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

  In the component (A), as the copolymer (A1), one type of copolymer may be contained alone, or two or more types may be used in combination.

[Copolymer (A1 ′)]
・ Structural unit (a1 ′)
The acid dissociable, dissolution inhibiting group in the structural unit (a1 ′) has an alkali dissolution inhibiting property that makes the entire copolymer (A1 ′) insoluble to alkali before dissociation, and this copolymer (A1 ′) after dissociation. The whole is changed to alkali-soluble.
In the structural unit (a1 ′), the acid dissociable, dissolution inhibiting group is not particularly limited as long as it is branched, and has been proposed as an acid dissociable, dissolution inhibiting group for base resins for chemically amplified resists. You can use what you have.
In the present invention, the “branched acid dissociable, dissolution inhibiting group” means an acid dissociable, dissolution inhibiting group having a branched carbon chain in its structure and having no cyclic group.
Examples of the branched acid dissociable, dissolution inhibiting group include a chain tertiary alkyl group, a chain tertiary alkoxycarbonyl group, a chain tertiary alkoxycarbonylalkyl group, and a branched alkoxyalkyl group. .
Examples of the chain tertiary alkyl group include a tert-butyl group, a tert-amyl group, a diethylmethyl group, and a tert-heptyl group.
Examples of the chain-like tertiary alkoxycarbonyl group include a tert-butyloxycarbonyl group and a tert-amyloxycarbonyl group.
Examples of the chain-like tertiary alkoxycarbonylalkyl group include a tert-butyloxycarbonylmethyl group and a tert-amyloxycarbonylmethyl group.
Examples of the branched alkoxyalkyl group include 1-isopropoxyethyl group and 1-ethoxyethyl group.

Examples of the structural unit (a1 ′) include those obtained by replacing the cyclic acid dissociable, dissolution inhibiting group in the structural unit (a1) with the branched acid dissociable, dissolution inhibiting group as described above.
As the structural unit (a1 ′), a structural unit having a chain-like tertiary alkyl group as the acid dissociable, dissolution inhibiting group is preferable, and in particular, the structural unit represented by the following general formula (a1′-1) is Since it is excellent in the effect of invention, it is preferable.

［式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基を表し；Ｒ^６１〜Ｒ^６３はそれぞれ独立して炭素数１〜４のアルキル基である。］

[Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group; R ^{61 to} R ⁶³ each independently represents an alkyl group having 1 to 4 carbon atoms. ]

R in the formula is the same as described above.
R ^{61 to} R ⁶³ are each independently an alkyl group having 1 to 4 carbon atoms, and may be linear or branched. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group.
In the present invention, R ^{61 to} R ⁶³ are preferably a methyl group or an ethyl group because the effects of the present invention are excellent. Of these, at least one of R ^{61 to} R ⁶³ is preferably an ethyl group, and in particular, one of R ^{61 to} R ⁶³ is preferably an ethyl group, and the other two are preferably methyl groups.

  In the copolymer (A1 ′), the proportion of the structural unit (a1 ′) is preferably from 10 to 80 mol%, more preferably from 20 to 70 mol%, based on all the structural units constituting the copolymer (A1 ′). Preferably, 25 to 50 mol% is more preferable, and 30 to 45 mol% is most preferable. By setting it to the lower limit value or more, a pattern can be obtained when the resist composition is used, and by setting it to the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a2 ′)
The copolymer (A1 ′) preferably has a structural unit (a2 ′) derived from an acrylate ester having a lactone-containing monocyclic or polycyclic group in addition to the structural unit (a1).
As the structural unit (a2 ′), those similar to the structural unit (a2) of the copolymer (A1) described above can be mentioned.
In the copolymer (A1 ′), as the structural unit (a2 ′), one type of structural unit may be used alone, or two or more types may be used in combination.
The proportion of the structural unit (a2 ′) in the copolymer (A1 ′) is preferably from 5 to 60 mol%, preferably from 10 to 50 mol, based on the total of all the structural units constituting the copolymer (A1 ′). % Is more preferable, 20 to 50 mol% is further preferable, and 25 to 45 mol% is most preferable. By setting it to the lower limit value or more, the effect of containing the structural unit (a2 ′) can be sufficiently obtained, and by setting the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a3 ′)
The copolymer (A1 ′) is an acrylic resin containing a polar group-containing aliphatic hydrocarbon group in addition to the structural unit (a1 ′) or in addition to the structural units (a1 ′) and (a2 ′). It is preferable to have a structural unit (a3 ′) derived from an acid ester.
As the structural unit (a3 ′), the same structural units as the structural unit (a3) of the copolymer (A1) described above can be used.
As the structural unit (a3 ′), one type may be used alone, or two or more types may be used in combination.
In the copolymer (A1 ′), the proportion of the structural unit (a3 ′) is preferably 5 to 50 mol% with respect to all the structural units constituting the copolymer (A1 ′), and 5 to 40 More preferably, mol% is more preferable, and 5-25 mol% is further more preferable.

・ Structural unit (a4 ′)
The copolymer (A1 ′) may contain other structural units (a4 ′) other than the structural units (a1 ′) to (a3 ′) as long as the effects of the present invention are not impaired.
As the structural unit (a4 ′), the same structural units as the structural unit (a4) of the copolymer (A1) described above can be used.
The structural unit (a4 ′) is not an essential component of the copolymer (A1 ′), but when it is contained in the copolymer (A1 ′), all components constituting the copolymer (A1 ′) are included. The structural unit (a4 ′) is contained in an amount of 1 to 30 mol%, preferably 10 to 20 mol%, based on the total of the units.

The copolymer (A1 ′) is obtained by polymerizing a monomer for deriving each structural unit by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN). Can do.
For the copolymer (A1 ′), a chain transfer agent such as HS—CH ₂ —CH ₂ —CH ₂ —C (CF ₃ ) ₂ —OH is used in combination in the above polymerization. May introduce a —C (CF ₃ ) ₂ —OH group at the terminal. As described above, a copolymer introduced with a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group is substituted with a fluorine atom reduces development defects and LER (line edge roughness: uneven unevenness of line side walls). It is effective in reducing

Although Mw of a copolymer (A1 ') is not specifically limited, 2000-50000 are preferable, 3000-30000 are more preferable, 5000-20000 are the most preferable. When it is smaller than the upper limit of this range, it has sufficient solubility in a resist solvent to be used as a resist, and the dry etching resistance and resist pattern cross-sectional shape that are larger than the lower limit of this range are good.
Further, Mw / Mn is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

  In the component (A), as the copolymer (A1 ′), one type of copolymer may be contained alone, or two or more types may be used in combination.

  In the component (A), since the mixing ratio (mass ratio) of the copolymer (A1) and the copolymer (A1 ′) is excellent in the effect of the present invention, the copolymer (A1): copolymer ( A1 ′) is preferably within the range of 9: 1 to 1: 9, more preferably 9: 1 to 2: 8, more preferably 9: 1 to 5: 5, and 9: 1 to 7: 3. Further preferred. By setting it as the said range, a pattern film film reduction can be suppressed. Further, the resist pattern shape is improved.

<(B) component>
The component (B) is not particularly limited, and those that have been proposed as acid generators for chemically amplified resists can be used. Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, poly (bissulfonyl) diazomethanes, and the like. There are various known diazomethane acid generators, nitrobenzyl sulfonate acid generators, imino sulfonate acid generators, disulfone acid generators, and the like.

  Examples of the onium salt acid generator include compounds represented by the following general formula (b-1) or (b-2).

［式中、Ｒ^１”〜Ｒ^３”，Ｒ^５”〜Ｒ^６”は、それぞれ独立に、アリール基またはアルキル基を表し；Ｒ^４”は、直鎖、分岐または環状のアルキル基またはフッ素化アルキル基を表し；Ｒ^１”〜Ｒ^３”のうち少なくとも１つはアリール基を表し、Ｒ^５”〜Ｒ^６”のうち少なくとも１つはアリール基を表す。］

[Wherein, R ¹ ″ to R ³ ″ and R ⁵ ″ to R ⁶ ″ each independently represents an aryl group or an alkyl group; R ⁴ ″ represents a linear, branched or cyclic alkyl group or fluorinated group. Represents an alkyl group; at least one of R ¹ ″ to R ³ ″ represents an aryl group, and at least one of R ⁵ ″ to R ⁶ ″ represents an aryl group.]

In formula (b-1), R ¹ ″ to R ³ ″ each independently represents an aryl group or an alkyl group. At least one of R ¹ ″ to R ³ ″ represents an aryl group. Of R ¹ ″ to R ³ ″, two or more are preferably aryl groups, and most preferably all R ¹ ″ to R ³ ″ are aryl groups.
The aryl group for R ¹ ″ to R ³ ″ is not particularly limited, and is, for example, an aryl group having 6 to 20 carbon atoms, in which part or all of the hydrogen atoms are alkyl groups, alkoxy groups It may or may not be substituted with a group, a halogen atom or the like. The aryl group is preferably an aryl group having 6 to 10 carbon atoms because it can be synthesized at a low cost. Specific examples include a phenyl group and a naphthyl group.
The alkyl group that may be substituted for the hydrogen atom of the aryl group is preferably an alkyl group having 1 to 5 carbon atoms, and is a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group. Is most preferred.
The alkoxy group that may be substituted for the hydrogen atom of the aryl group is preferably an alkoxy group having 1 to 5 carbon atoms, and most preferably a methoxy group or an ethoxy group.
The halogen atom that may be substituted for the hydrogen atom of the aryl group is preferably a fluorine atom.
The alkyl group for R 1 ^{"~R 3",} is not particularly limited, for example, a straight, include alkyl groups such as branched or cyclic. It is preferable that it is C1-C5 from the point which is excellent in resolution. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, and a decanyl group. A methyl group is preferable because it is excellent in resolution and can be synthesized at low cost.
Among these, it is most preferable that all of R ¹ ″ to R ³ ″ are phenyl groups.

R ⁴ ″ represents a linear, branched or cyclic alkyl group or a fluorinated alkyl group.
The linear alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.
The cyclic alkyl group is a cyclic group as indicated by R ¹ ″ and preferably has 4 to 15 carbon atoms, more preferably 4 to 10 carbon atoms, and more preferably 6 carbon atoms. Most preferably, it is -10.
The fluorinated alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms. Also. The fluorination rate of the fluorinated alkyl group (ratio of fluorine atoms in the alkyl group) is preferably 10 to 100%, more preferably 50 to 100%, and particularly those in which all hydrogen atoms are substituted with fluorine atoms. Since the strength of the acid is increased, it is preferable.
R ⁴ ″ is most preferably a linear or cyclic alkyl group or a fluorinated alkyl group.

In formula (b-2), R ⁵ ″ to R ⁶ ″ each independently represents an aryl group or an alkyl group. At least one of R ⁵ ″ to R ⁶ ″ represents an aryl group. Of R ⁵ ″ to R ⁶ ″, two or more are preferably aryl groups, and most preferably R ⁵ ″ to R ⁶ ″ are all aryl groups.
As the aryl group for R ⁵ ″ to R ⁶ ″, the same as the aryl groups for R ¹ ″ to R ³ ″ can be used.
Examples of the alkyl group for R ⁵ ″ to R ⁶ ″ include the same as the alkyl group for R ¹ ″ to R ³ ″.
Among these, it is most preferable that all of R ⁵ ″ to R ⁶ ″ are phenyl groups.
"As ^{R 4} in the formula (b-1)" ^{R 4} in the In the formula (b-2) include the same as.

  Specific examples of the onium salt-based acid generator include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, and triphenylsulfonium trifluoromethane. Sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, tri (4-methylphenyl) sulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, dimethyl (4-hydroxynaphthyl) sulfonium trifluoromethane Sulfonate, its heptafluoropropane sulphonate or its Nafluorobutane sulfonate, trifluoromethane sulfonate of monophenyldimethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, trifluoromethane sulfonate of diphenyl monomethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, (4- Trifluoromethanesulfonate of methylphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, trifluoromethanesulfonate of (4-methoxyphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, tri (4 -Tert-bu E) phenylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate, diphenyl (1- (4-methoxy) naphthyl) sulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate Is mentioned. In addition, onium salts in which the anion portion of these onium salts is replaced with methanesulfonate, n-propanesulfonate, n-butanesulfonate, or n-octanesulfonate can also be used.

  Moreover, what replaced the anion part by the anion part represented by the following general formula (b-3) or (b-4) in the said general formula (b-1) or (b-2) can also be used. (The cation moiety is the same as (b-1) or (b-2)).

［式中、Ｘ”は、少なくとも１つの水素原子がフッ素原子で置換された炭素数２〜６のアルキレン基を表し；Ｙ”、Ｚ”は、それぞれ独立に、少なくとも１つの水素原子がフッ素原子で置換された炭素数１〜１０のアルキル基を表す。］

[Wherein X ″ represents an alkylene group having 2 to 6 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom; Y ″ and Z ″ each independently represent at least one hydrogen atom as a fluorine atom; Represents an alkyl group having 1 to 10 carbon atoms and substituted with

X ″ is a linear or branched alkylene group in which at least one hydrogen atom is substituted with a fluorine atom, and the alkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms, Preferably it is C3.
Y ″ and Z ″ are each independently a linear or branched alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and the alkyl group has 1 to 10 carbon atoms, preferably It is C1-C7, More preferably, it is C1-C3.
The carbon number of the alkylene group of X ″ or the carbon number of the alkyl group of Y ″ and Z ″ is preferably as small as possible because the solubility in the resist solvent is good within the above carbon number range.
In addition, in the alkylene group of X ″ or the alkyl group of Y ″ and Z ″, as the number of hydrogen atoms substituted with fluorine atoms increases, the strength of the acid increases, and high-energy light or electron beam of 200 nm or less The ratio of fluorine atoms in the alkylene group or alkyl group, that is, the fluorination rate is preferably 70 to 100%, more preferably 90 to 100%, and most preferably all. Are a perfluoroalkylene group or a perfluoroalkyl group in which a hydrogen atom is substituted with a fluorine atom.

  In the present invention, the oxime sulfonate-based acid generator is a compound having at least one group represented by the following general formula (B-1), and has a property of generating an acid upon irradiation with radiation. . Such oxime sulfonate acid generators are frequently used for chemically amplified resist compositions, and can be arbitrarily selected and used.

（式（Ｂ−１）中、Ｒ^２１、Ｒ^２２はそれぞれ独立に有機基を表す。）

(In formula (B-1), R ²¹ and R ²² each independently represents an organic group.)

In the present invention, the organic group is a group containing a carbon atom, and has an atom other than a carbon atom (for example, a hydrogen atom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom (fluorine atom, chlorine atom, etc.)). It may be.
The organic group for R ²¹ is preferably a linear, branched or cyclic alkyl group or aryl group. These alkyl groups and aryl groups may have a substituent. There is no restriction | limiting in particular as this substituent, For example, a fluorine atom, a C1-C6 linear, branched or cyclic alkyl group etc. are mentioned. Here, “having a substituent” means that part or all of the hydrogen atoms of the alkyl group or aryl group are substituted with a substituent.
As an alkyl group, C1-C20 is preferable, C1-C10 is more preferable, C1-C8 is more preferable, C1-C6 is especially preferable, and C1-C4 is the most preferable. As the alkyl group, a partially or completely halogenated alkyl group (hereinafter sometimes referred to as a halogenated alkyl group) is particularly preferable. The partially halogenated alkyl group means an alkyl group in which a part of hydrogen atoms is substituted with a halogen atom, and the fully halogenated alkyl group means that all of the hydrogen atoms are halogen atoms. Means an alkyl group substituted with Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable. That is, the halogenated alkyl group is preferably a fluorinated alkyl group.
The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the aryl group, a partially or completely halogenated aryl group is particularly preferable. The partially halogenated aryl group means an aryl group in which a part of hydrogen atoms is substituted with a halogen atom, and the fully halogenated aryl group means that all of the hydrogen atoms are halogen atoms. Means an aryl group substituted with.
R ²¹ is particularly preferably an alkyl group having 1 to 4 carbon atoms having no substituent or a fluorinated alkyl group having 1 to 4 carbon atoms.

As the organic group for R ²² , a linear, branched, or cyclic alkyl group, aryl group, or cyano group is preferable. As the alkyl group and aryl group for R ^22, the same alkyl groups and aryl groups as those described above for R ²¹ can be used.
R ²² is particularly preferably a cyano group, an alkyl group having 1 to 8 carbon atoms having no substituent, or a fluorinated alkyl group having 1 to 8 carbon atoms.

  More preferable examples of the oxime sulfonate-based acid generator include compounds represented by the following general formula (B-2) or (B-3).

［式（Ｂ−２）中、Ｒ^３１は、シアノ基、置換基を有さないアルキル基またはハロゲン化アルキル基である。Ｒ^３２はアリール基である。Ｒ^３３は置換基を有さないアルキル基またはハロゲン化アルキル基である。］

[In Formula (B-2), R ³¹ represents a cyano group, an alkyl group having no substituent, or a halogenated alkyl group. R ³² is an aryl group. R ³³ is an alkyl group having no substituent or a halogenated alkyl group. ]

［式（Ｂ−３）中、Ｒ^３４はシアノ基、置換基を有さないアルキル基またはハロゲン化アルキル基である。Ｒ^３５は２または３価の芳香族炭化水素基である。Ｒ^３６は置換基を有さないアルキル基またはハロゲン化アルキル基である。ｐは２または３である。］

[In the formula (B-3), R ³⁴ represents a cyano group, an alkyl group having no substituent, or a halogenated alkyl group. R ³⁵ is a divalent or trivalent aromatic hydrocarbon group. R ³⁶ is an alkyl group having no substituent or a halogenated alkyl group. p is 2 or 3. ]

In the general formula (B-2), the alkyl group or halogenated alkyl group having no substituent for R ³¹ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and more preferably carbon atoms. Numbers 1 to 6 are most preferable.
R ³¹ is preferably a halogenated alkyl group, more preferably a fluorinated alkyl group.
The fluorinated alkyl group for R ³¹ is preferably fluorinated by 50% or more of the hydrogen atom of the alkyl group, more preferably 70% or more, and even more preferably 90% or more.

As the aryl group of R ³² , one hydrogen atom is removed from an aromatic hydrocarbon ring such as a phenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, an anthracyl group, a phenanthryl group, or the like. And a heteroaryl group in which a part of carbon atoms constituting the ring of these groups is substituted with a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom. Among these, a fluorenyl group is preferable.
The aryl group represented by R ³² may have a substituent such as an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. The alkyl group or halogenated alkyl group in the substituent preferably has 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. The halogenated alkyl group is preferably a fluorinated alkyl group.

The alkyl group or halogenated alkyl group having no substituent for R ³³ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbon atoms.
R ³³ is preferably a halogenated alkyl group, more preferably a fluorinated alkyl group, and most preferably a partially fluorinated alkyl group.
The fluorinated alkyl group in R ³³ preferably has 50% or more of the hydrogen atom of the alkyl group, more preferably 70% or more, and even more preferably 90% or more. This is preferable because the strength of the acid is increased. Most preferably, it is a fully fluorinated alkyl group in which a hydrogen atom is 100% fluorine-substituted.

In the general formula (B-3), the alkyl group or halogenated alkyl group having no substituent for R ³⁴ is the same as the alkyl group or halogenated alkyl group having no substituent for R ^31. Is mentioned.
Examples of the divalent or trivalent aromatic hydrocarbon group for R ³⁵ include groups obtained by further removing one or two hydrogen atoms from the aryl group for R ³² .
Examples of the alkyl group or halogenated alkyl group having no substituent for R ³⁶ include the same alkyl groups or halogenated alkyl groups as those having no substituent for R ³³ .
p is preferably 2.

Specific examples of the oxime sulfonate acid generator include α- (p-toluenesulfonyloxyimino) -benzyl cyanide, α- (p-chlorobenzenesulfonyloxyimino) -benzyl cyanide, α- (4-nitrobenzenesulfonyloxy). Imino) -benzylcyanide, α- (4-nitro-2-trifluoromethylbenzenesulfonyloxyimino) -benzylcyanide, α- (benzenesulfonyloxyimino) -4-chlorobenzylcyanide, α- (benzenesulfonyl) Oxyimino) -2,4-dichlorobenzyl cyanide, α- (benzenesulfonyloxyimino) -2,6-dichlorobenzyl cyanide, α- (benzenesulfonyloxyimino) -4-methoxybenzyl cyanide, α- ( 2-Chlorobenzenesulfonyloxyimino) 4-methoxybenzylcyanide, α- (benzenesulfonyloxyimino) -thien-2-ylacetonitrile, α- (4-dodecylbenzenesulfonyloxyimino) -benzylcyanide, α-[(p-toluenesulfonyloxyimino) -4-methoxyphenyl] acetonitrile, α-[(dodecylbenzenesulfonyloxyimino) -4-methoxyphenyl] acetonitrile, α- (tosyloxyimino) -4-thienyl cyanide, α- (methylsulfonyloxyimino) -1-cyclo Pentenyl acetonitrile, α- (methylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (methylsulfonyloxyimino) -1-cycloheptenylacetonitrile, α- (methylsulfonyloxyimino) -1-cyclooctene Acetonitrile, α- (trifluoromethylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -cyclohexylacetonitrile, α- (ethylsulfonyloxyimino) -ethylacetonitrile, α- (propyl Sulfonyloxyimino) -propylacetonitrile, α- (cyclohexylsulfonyloxyimino) -cyclopentylacetonitrile, α- (cyclohexylsulfonyloxyimino) -cyclohexylacetonitrile, α- (cyclohexylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- ( Ethylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- (isopropylsulfonyloxyimino) -1-cyclope N-tenyl acetonitrile, α- (n-butylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- (ethylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (isopropylsulfonyloxyimino) -1-cyclohexenylacetonitrile , Α- (n-butylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (methylsulfonyloxyimino) -phenylacetonitrile, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (trifluoro Methylsulfonyloxyimino) -phenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -p- Butoxy phenylacetonitrile, alpha-(propylsulfonyl oxyimino)-p-methylphenyl acetonitrile, alpha-like (methylsulfonyloxyimino)-p-bromophenyl acetonitrile.
Moreover, the compound represented by the following chemical formula is mentioned.

  Moreover, the example of a preferable compound is shown below among the compounds represented by the said general formula (B-2) or (B-3).

  Of the above exemplified compounds, the following four compounds are preferred.

Among diazomethane acid generators, specific examples of bisalkyl or bisarylsulfonyldiazomethanes include bis (isopropylsulfonyl) diazomethane, bis (p-toluenesulfonyl) diazomethane, bis (1,1-dimethylethylsulfonyl) diazomethane, Examples include bis (cyclohexylsulfonyl) diazomethane, bis (2,4-dimethylphenylsulfonyl) diazomethane, and the like.
Examples of poly (bissulfonyl) diazomethanes include 1,3-bis (phenylsulfonyldiazomethylsulfonyl) propane (when A = 3) and 1,4-bis (phenylsulfonyldiazo) having the following structure. Methylsulfonyl) butane (when A = 4), 1,6-bis (phenylsulfonyldiazomethylsulfonyl) hexane (when A = 6), 1,10-bis (phenylsulfonyldiazomethylsulfonyl) decane (A = 10) 1), 1,2-bis (cyclohexylsulfonyldiazomethylsulfonyl) ethane (when B = 2), 1,3-bis (cyclohexylsulfonyldiazomethylsulfonyl) propane (when B = 3), 1,6- Bis (cyclohexylsulfonyldiazomethylsulfonyl) hexane (when B = 6) (For B = 10) 1,10-bis (cyclohexyl diazomethylsulfonyl) decane and the like.

(B) As a component, these acid generators may be used individually by 1 type, and may be used in combination of 2 or more type. In the present invention, an onium salt having a fluorinated alkyl sulfonate ion as an anion is particularly preferable.
Content of (B) component in the positive resist composition of this invention is 0.5-30 mass parts with respect to 100 mass parts of (A) component, Preferably it is 1-10 mass parts. By setting it within the above range, pattern formation is sufficiently performed. Moreover, since a uniform solution is obtained and storage stability becomes favorable, it is preferable.

<Optional component>
In the positive resist composition of the present invention, a nitrogen-containing organic compound (D) (hereinafter referred to as “component (D)”) is further added as an optional component in order to improve the resist pattern shape, stability over time and the like. Can be blended.
Since a wide variety of components (D) have been proposed, any known one may be used, but aliphatic amines, particularly secondary aliphatic amines and tertiary aliphatic amines are preferred. .
Examples of the aliphatic amine include amines (alkyl amines or alkyl alcohol amines) in which at least one hydrogen atom of ammonia NH ₃ is substituted with an alkyl group or hydroxyalkyl group having 12 or less carbon atoms. Specific examples thereof include monoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine; diethylamine, di-n-propylamine, di-n-heptylamine, Dialkylamines such as di-n-octylamine and dicyclohexylamine; trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine, tri-n-pentylamine, tri-n-heptyl Trialkylamines such as amine, tri-n-octylamine, tri-n-nonylamine, tri-n-decanylamine, tri-n-dodecylamine; diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, di-n -Ok Noruamin, alkyl alcohol amines such as tri -n- octanol amine. Among these, alkyl alcohol amines and trialkyl amines are preferable, and alkyl alcohol amines are most preferable. Of the alkyl alcohol amines, triethanolamine and triisopropanolamine are most preferred.
These may be used alone or in combination of two or more.
(D) component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component.

In addition, the positive resist composition of the present invention includes an organic carboxylic acid as an optional component for the purpose of preventing sensitivity deterioration due to the blending of the component (D), and improving the resist pattern shape, retention stability, and the like. Acid or phosphorus oxo acid or its derivative (E) (hereinafter referred to as component (E)) can be contained. In addition, (D) component and (E) component can also be used together, and any 1 type can also be used.
As the organic carboxylic acid, for example, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid and the like are suitable.
Phosphorus oxoacids or derivatives thereof include phosphoric acid, phosphoric acid di-n-butyl ester, phosphoric acid diphenyl ester and other phosphoric acid or derivatives thereof such as phosphonic acid, phosphonic acid dimethyl ester, phosphonic acid- Like phosphonic acids such as di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester, phosphonic acid dibenzyl ester and their esters, phosphinic acids such as phosphinic acid, phenylphosphinic acid and their esters Among these, phosphonic acid is particularly preferable.
(E) A component is used in the ratio of 0.01-5.0 mass parts per 100 mass parts of (A) component.

  The positive resist composition of the present invention may further contain miscible additives as desired, for example, an additional resin for improving the performance of the resist film, a surfactant for improving coating properties, a dissolution inhibitor, Plasticizers, stabilizers, colorants, antihalation agents, dyes, and the like can be added and contained as appropriate.

The positive resist composition of the present invention can be produced by dissolving the material in an organic solvent (hereinafter sometimes referred to as (S) component).
As the component (S), any component can be used as long as it can dissolve each component to be used to form a uniform solution, and any one of conventionally known solvents for chemically amplified resists can be used. Two or more types can be appropriately selected and used.
For example, lactones such as γ-butyrolactone, ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate Polyhydric alcohols such as dipropylene glycol or dipropylene glycol monoacetate monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and derivatives thereof, cyclic ethers such as dioxane, Methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, pyruvate Le, methyl methoxypropionate, esters such as ethyl ethoxypropionate can be exemplified.
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.
A mixed solvent obtained by mixing propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent is preferable. The blending ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. It is preferable to be within the range.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. When propylene glycol monomethyl ether (PGME) is blended as a polar solvent, the mass ratio of PGMEA: PGME is preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2, and even 7: It is preferable that it is 3-5: 5.
In addition, as the component (S), a mixed solvent of at least one selected from PGMEA and EL and γ-butyrolactone is also preferable. In this case, the mixing ratio of the former and the latter is preferably 70:30 to 95: 5.
The amount of the component (S) used is not particularly limited, but is a concentration that can be applied to a substrate or the like, and is appropriately set according to the coating film thickness. In general, the solid content concentration of the resist composition is 2 -20% by mass, preferably 5-15% by mass.

The positive resist composition of the present invention has an excellent resolution. The reason is not clear, but, for example, in a process using an ArF excimer laser, a conventional resist resin generally has a polycyclic group such as an adamantyl group in order to have sufficient dry etching resistance. Those having an acid dissociable, dissolution inhibiting group (protecting group) containing an aliphatic polycyclic group have been used. However, since such a protective group is bulky, it is considered that a leaving product generated after the protective group is dissociated is likely to remain in the resist film. Such a desorbed material acts as a plasticizer in the resist film and softens the resist film, thereby making it difficult to control acid diffusion by extending the diffusion length of the acid generated in the resist film. This is thought to have hindered the improvement of resolution.
On the other hand, the branched acid dissociable, dissolution inhibiting group in the copolymer (A1 ′) is easily gasified after desorption. For example, when it is baked (PEB) after exposure, it is gasified to be outside the resist film. It is considered that it is released and hardly remains in the resist film. In this process, the gasified acid dissociable, dissolution inhibiting group moves in the resist film in the vertical direction, that is, from the substrate side to the resist film surface direction, and accordingly, acid diffusion is promoted in the vertical direction. The lateral direction is considered to be suppressed.
The copolymer (A1) having a cyclic acid dissociable, dissolution inhibiting group improves the strength of the resist film in the unexposed area, improves the dry etching resistance, and improves the shape of the resist pattern. This is considered to contribute to the improvement of resolution.
Therefore, in the positive resist composition of the present invention using both the copolymer (A1 ′) and the copolymer (A1), a resist having excellent dry etching resistance as a resist material and excellent resolution. It is thought that a pattern can be formed.

Whether the positive resist composition of the present invention is excellent in resolving power can be confirmed, for example, by evaluating MEF (mask error factor).
The MEF is a parameter indicating how faithfully a mask pattern having a different line width or aperture can be reproduced with the same exposure amount, and is a value obtained by the following equation. The MEF is preferably closer to 1.
MEF = | CD _x -CD _y | / | MD _x -MD _y |
In the above formula, MD _x and MD _y are different mask pattern sizes (nm), and CD _x and CD _y are resist pattern sizes (nm) formed using the mask patterns, respectively.

  The present invention also has advantages such as a wide depth of focus (DOF) and a large exposure margin. This is thought to be due to the improved controllability of acid diffusion, as described above.

≪Resist pattern formation method≫
The resist pattern forming method of the present invention can be performed, for example, as follows.
That is, first, the positive resist composition is applied onto a substrate such as a silicon wafer with a spinner and prebaked for 40 to 120 seconds, preferably 60 to 90 seconds under a temperature condition of 80 to 150 ° C. After selectively exposing ArF excimer laser light through a desired mask pattern using, for example, an ArF exposure apparatus or the like, PEB (post-exposure heating) is performed for 40 to 120 seconds at a temperature of 80 to 150 ° C., preferably Apply for 60-90 seconds. Subsequently, this is developed using an alkaline developer, for example, an aqueous 0.1 to 10% by mass tetramethylammonium hydroxide solution. In this way, a resist pattern faithful to the mask pattern can be obtained.
An organic or inorganic antireflection film can be provided between the substrate and the coating layer of the resist composition.
The wavelength used for exposure is not particularly limited, and ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray Or the like. The positive resist composition according to the present invention is particularly effective for an ArF excimer laser.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited by these examples.
[Synthesis example]
Synthesis of Resin (A) -1 To a 4-necked flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer, 320 g of tetrahydrofuran, 31.2 g of tert-amyl methacrylate, 34.0 g of γ-butyrolactone methacrylate and 3 After putting 23.6 g of -hydroxy-1-adamantyl methacrylate and replacing with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution prepared by dissolving 11.5 g of a polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) in 17 g of tetrahydrofuran was added dropwise over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. This precipitate was filtered, washed and dried to obtain Resin (A) -1. The mass average molecular weight (Mw) determined by gel permeation chromatography (GPC) in terms of polystyrene was 10500, and the degree of dispersion was (Mw / Mn) 1.55.
As a result of measurement by carbon NMR ( ¹³ C-NMR), the composition ratio was n: m: l = 40: 40: 20 (molar ratio).

Synthesis of Resin (A) -2 In a four-necked flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer, 320 g of tetrahydrofuran, 34.1 g of diethylmethyl methacrylate, 34.0 g of γ-butyrolactone methacrylate and 3- After putting 23.6 g of hydroxy-1-adamantyl methacrylate and replacing with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution prepared by dissolving 11.5 g of a polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) in 17 g of tetrahydrofuran was added dropwise over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. The precipitate was filtered, washed and dried to obtain Resin (A) -2.

Synthesis of Resin (A) -3 In a four-necked flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer, 330 g of tetrahydrofuran, 36.9 g of tert heptyl methacrylate, 34.0 g of γ-butyrolactone methacrylate and 3- After putting 23.6 g of hydroxy-1-adamantyl methacrylate and replacing with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution prepared by dissolving 11.5 g of a polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) in 17 g of tetrahydrofuran was added dropwise over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. The precipitate was filtered, washed and dried to obtain Resin (A) -3.

Synthesis of Resin (A) -4 To a 4-neck flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer, 300 g of tetrahydrofuran, 31.2 g of tert-amyl methacrylate, 31.2 g of γ-butyrolactone acrylate and 3 After putting 23.6 g of -hydroxy-1-adamantyl methacrylate and replacing with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution prepared by dissolving 11.5 g of a polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) in 17 g of tetrahydrofuran was added dropwise over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. The precipitate was filtered, washed and dried to obtain Resin (A) -4.

-Synthesis of Resin (A) -5 To a 4-neck flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer, 300 g of tetrahydrofuran, 39.1 g of tert-amyl methacrylate, 25.5 g of γ-butyrolactone methacrylate and 3 After putting 22.2 g of hydroxy-1-adamantyl acrylate and replacing with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution prepared by dissolving 11.5 g of a polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) in 17 g of tetrahydrofuran was added dropwise over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. The precipitate was filtered, washed and dried to obtain Resin (A) -5.

-Synthesis of Resin (A) -6 To a 4-neck flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer, 300 g of tetrahydrofuran, 31.2 g of tert-amyl methacrylate, 31.2 g of γ-butyrolactone acrylate and 3 After putting 22.2 g of hydroxy-1-adamantyl acrylate and replacing with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution prepared by dissolving 11.5 g of a polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) in 17 g of tetrahydrofuran was added dropwise over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. The precipitate was filtered, washed and dried to obtain Resin (A) -6.

-Synthesis | combination of resin (A) -7 340g of tetrahydrofuran, 39.3g of 1-ethyl- 1-cyclohexyl methacrylate, and (gamma) -butyrolactone methacrylate 34 were added to the 4-neck flask equipped with the nitrogen blowing tube, the reflux condenser, the dropping funnel, and the thermometer. 0.0 g and 33.6 g of 3-hydroxy-1-adamantyl methacrylate were added, and after the atmosphere was replaced with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution prepared by dissolving 11.5 g of a polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) in 17 g of tetrahydrofuran was added dropwise over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. The precipitate was filtered, washed and dried to obtain Resin (A) -7.

Synthesis of Resin (A) -8 Tetrahydrofuran 330 g, 2-methyl-2-adamantyl methacrylate 35.1 g, 5-acryloyloxy-to a 4-neck flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer After putting 46.8 g of 2,6-norbornanecarbolactone and 11.8 g of 3-hydroxy-1-adamantyl methacrylate and replacing with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution prepared by dissolving 11.5 g of a polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) in 17 g of tetrahydrofuran was added dropwise over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. The precipitate was filtered, washed and dried to obtain Resin (A) -8.

-Synthesis of Resin (A) -9 Tetrahydrofuran 400g, 2-ethyl-2-adamantyl methacrylate 49.7g, 5-acryloyloxy- in a 4-neck flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer After putting 41.6 g of 2,6-norbornanecarbolactone and 23.6 g of 3-hydroxy-1-adamantyl methacrylate and replacing with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution prepared by dissolving 11.5 g of a polymerization initiator V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) in 17 g of tetrahydrofuran was added dropwise over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. This precipitate was filtered off, washed and dried to obtain Resin (A) -9.

-Examples 1-7, Comparative Examples 1-2
Each component shown in Table 1 was mixed and dissolved to prepare a positive resist composition solution.

Each abbreviation in Table 1 has the following meaning. Moreover, the numerical value in [] of Table 1 is a compounding quantity (mass part).
(B) -1: 4-methylphenyldiphenylsulfonium nonafluoro-n-butanesulfonate.
(B) -2: Compound having the following chemical formula

(B) -3: Compound of the following chemical formula

(D) -1: Triethanolamine.
(S) -1: Mixed solvent of PGMEA / propylene glycol monomethyl ether = 6/4 (mass ratio).
(S) -2: Mixed solvent of PGMEA / EL = 8/2 (mass ratio).
(S) -3: PGMEA / cyclohexanone = 6/4 (mass ratio) mixed solvent.

The following evaluation was performed using the obtained positive resist composition solution.
-Depth of focus (DOF) evaluation An organic antireflective coating composition "ARC-29" (trade name, manufactured by Brewer Science) was applied onto an 8-inch silicon wafer using a spinner, and 205 ° C on a hot plate. By baking for 60 seconds and drying, an organic antireflection film having a film thickness of 77 nm was formed. A positive resist composition solution is applied onto the antireflection film using a spinner, prebaked on a hot plate at the PAB temperature shown in Table 2 for 60 seconds, and dried to form a resist film having a thickness of 250 nm. Formed.
Next, an ArF excimer laser (193 nm) was passed through a mask pattern (6% halftone) with an ArF exposure apparatus NSR-S306 (manufactured by Nikon; NA (numerical aperture) = 0.78, σ = 0.90). Selectively irradiated.
Then, PEB treatment was performed at the PEB temperature shown in Table 2 for 60 seconds, and further developed at 23 ° C. using a 2.38 mass% tetramethylammonium hydroxide aqueous solution for 60 seconds, then washed with water for 20 seconds and dried. Thus, a hole pattern (print / mask / pitch = 110 nm / 130 nm / 220 nm) having a diameter of 110 nm was formed.
At an optimum exposure dose EOP (mJ / cm ² ) at which a hole pattern with a diameter of 110 nm is formed, the focal point is appropriately shifted up and down, and the depth of focus at which the hole pattern can be obtained within the range of the dimensional change rate of 110 nm ± 10%. The width (μm) of (DOF) was determined. The results are shown in Table 2.

Mask error factor (MEF) evaluation A hole pattern was formed in the same manner as above except that the mask pattern size was changed to 130 nm (pitch 220 nm) or 150 nm (pitch 227.5 nm) at the EOP. From this, the value of MEF (mask error factor) was determined.
MEF = | CD150-CD130 | / | MD150-MD130 |
In the above formula, CD150 and CD130 are the dimensions (diameter (nm)) of hole patterns formed using mask patterns of 150 nm and 130 nm, respectively, and MD150 and MD130 are the diameters (nm) of holes of the mask pattern, respectively. MD150 = 150 and MD130 = 130. MEF is a parameter that indicates how faithfully a mask pattern with different dimensions can be reproduced with the same exposure amount. The closer this MEF value is to 1, the higher the reproducibility of the mask pattern and the better the resolution. is there. The results are shown in Table 2 below.

As described above, any one of the copolymers (A) -1 to (A) -6 corresponding to the copolymer (A1 ′) and the copolymer (A) -8 corresponding to the copolymer (A1) In Examples 1 to 7 used in a mixture, MEF was closer to 1 than in Comparative Examples, and in particular, Examples 5 to 7 had particularly good MEF. From this, it was confirmed that the positive resist compositions of Examples 1 to 7 have high resolution. Moreover, the positive resist compositions of Examples 1 to 7 all had a larger DOF than the comparative examples.
On the other hand, Comparative Examples 1 and 2 using only one or two of the copolymers (A) -7 to (A) -9 corresponding to the copolymer (A1) had a large MEF. Moreover, DOF was also smaller than the Example.

Claims (9)

A positive resist composition comprising a resin component (A) whose alkali solubility is increased by the action of an acid and an acid generator component (B) which generates an acid upon exposure,
The resin component (A) is a copolymer (A1) having a structural unit (a1) derived from an acrylate ester containing a cyclic acid dissociable, dissolution inhibiting group, and a branched acid dissociable, dissolution inhibiting group. A positive resist composition comprising a copolymer (A1 ′) having a structural unit (a1 ′) derived from an acrylate ester containing The structural unit (a1 ′) is represented by the following general formula (a1′-1)

[Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group; R ^{61 to} R ⁶³ each independently represents an alkyl group having 1 to 4 carbon atoms. ]
The positive resist composition of Claim 1 represented by these.   The positive resist composition according to claim 1 or 2, wherein a mixing ratio (mass ratio) of the copolymer (A1) and the copolymer (A1 ') is within a range of 9: 1 to 1: 9.   The positive resist according to claim 1, wherein the copolymer (A1) has a structural unit (a2) derived from an acrylate ester having a lactone-containing monocyclic or polycyclic group. Composition.   The positive resist according to claim 1, wherein the copolymer (A1) has a structural unit (a3) derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group. Composition.   6. The positive electrode according to claim 1, wherein the copolymer (A1 ′) has a structural unit (a2 ′) derived from an acrylate ester having a lactone-containing monocyclic or polycyclic group. Type resist composition.   The positive electrode according to any one of claims 1 to 6, wherein the copolymer (A1 ') has a structural unit (a3') derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group. Type resist composition.   Furthermore, the positive resist composition as described in any one of Claims 1-7 containing a nitrogen-containing organic compound (D). A step of forming a resist film on a substrate using the positive resist composition according to claim 1, a step of exposing the resist film, and developing the resist film to form a resist pattern A resist pattern forming method including the step of: