JP2008268484A - Positive resist composition and resist pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive resist composition excellent in depth-of-focus (DOF) characteristics and a resist pattern forming method. <P>SOLUTION: The positive resist composition comprises a resin component (A) of which the solubility in an alkali developer increases by an action of an acid and an acid generator component (B) which generates an acid by exposure, wherein the resin component (A) comprises a polymer (A1) comprising a constitutional unit having in a side chain an alicyclic group having a specific substituent, and the polymer (A1) has a mass average molecular weight of 4,000-7,000. <P>COPYRIGHT: (C)2009,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 radiation 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 rapidly progressed 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 now 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 lithography characteristics such as sensitivity to these exposure light sources and resolution capable of reproducing a pattern with fine dimensions. As a resist material that satisfies such requirements, a chemically amplified resist containing a base resin whose solubility in an alkaline developer 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 that increases solubility in an alkaline developer by the action of an acid and an acid generator. When the acid is generated, the exposed portion becomes soluble in the alkaline developer.
Up to now, as the base resin of chemically amplified resist, polyhydroxystyrene (PHS), which is highly transparent to KrF excimer laser (248 nm), and a resin whose hydroxyl group is protected with an acid dissociable, dissolution inhibiting group (PHS resin) Has been used. However, since the PHS resin has an aromatic ring such as a benzene ring, the transparency to light having a wavelength shorter than 248 nm, for example, 193 nm, is not sufficient. For this reason, a chemically amplified resist having a PHS resin as a base resin component has drawbacks such as low resolution in a process using 193 nm light, for example.
Therefore, as a resist base resin currently used in ArF excimer laser lithography and the like, since it has excellent transparency near 193 nm, a resin (acrylic resin) having a structural unit derived from (meth) acrylic ester is used. Resin) is mainly used (for example, see Patent Document 1).
JP 2003-241385 A

In recent years, as the resist pattern is further miniaturized, it is required to improve various lithography characteristics as well as high resolution. As one of them, improvement of the depth of focus (DOF) characteristic is required in order to improve a process margin and the like during pattern formation.
“DOF” refers to a range of depth of focus in which a resist pattern can be formed with a dimension within which a deviation from a target dimension is within a predetermined range when exposure is performed with the same exposure amount while shifting the focus up and down. This is a range in which a faithful resist pattern can be obtained, and a larger value is more preferable.
However, the conventional resist composition has a problem that the DOF characteristics are insufficient.

  This invention is made | formed in view of the said situation, Comprising: It aims at providing the positive resist composition excellent in the depth of focus width (DOF) characteristic, and a resist pattern formation method.

The present inventors propose the following means in order to solve the above problems.
That is, the first aspect of the present invention is a positive type containing a resin component (A) whose solubility in an alkaline developer is increased by the action of an acid and an acid generator component (B) that generates an acid upon exposure. It is a resist composition, The said resin component (A) contains the polymer (A1) which has the structural unit (a0-1) represented by the following general formula (a0-1), and the said polymer ( A positive resist composition having a mass average molecular weight of A1) of 4000 to 7000.

［式（ａ０−１）中、Ｒは水素原子、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；Ｙ^１は脂肪族環式基であり；Ｚは第３級アルキル基含有基またはアルコキシアルキル基であり；ａは１〜３の整数であり、ｂは０〜２の整数であり、かつ、ａ＋ｂ＝１〜３であり；ｃ、ｄ、ｅはそれぞれ独立して０〜３の整数である。］

[In the formula (a0-1), R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; Y ¹ represents an aliphatic cyclic group; Z represents a tertiary alkyl group-containing group or an alkoxyalkyl group. A is an integer of 1 to 3, b is an integer of 0 to 2, and a + b = 1 to 3; c, d, and e are each independently an integer of 0 to 3. . ]

  Further, the second aspect of the present invention includes a step of forming a resist film on a support using the positive resist composition of the first aspect, a step of exposing the resist film, and an alkali of the resist film. A resist pattern forming method comprising a step of developing to form a resist pattern.

In the present specification and claims, the “structural unit” means a monomer unit (monomer unit) constituting a resin component (polymer, copolymer).
The “polymer” is intended to include a homopolymer composed of one kind of structural unit and a copolymer composed of a plurality of structural units.
Unless otherwise specified, the “alkyl group” includes linear, branched, and cyclic monovalent saturated hydrocarbon groups.
“Lower alkyl group” means an alkyl group having 1 to 5 carbon atoms.
The term “exposure” includes not only light irradiation but also general irradiation of radiation such as an electron beam.

  ADVANTAGE OF THE INVENTION By this invention, the positive resist composition excellent in the depth of focus width (DOF) characteristic and the resist pattern formation method can be provided.

≪Positive resist composition≫
The positive resist composition of the present invention comprises a resin component (A) whose solubility in an alkaline developer is increased by the action of an acid (hereinafter referred to as component (A)), and an acid generator component that generates an acid upon exposure. (B) (hereinafter referred to as component (B)).
In the positive resist composition of the present invention, the component (A) is insoluble in an alkali developer before exposure. When an acid is generated from the component (B) by exposure, the component (A) is generated by the action of the acid. Solubility in the entire alkaline developer is increased. 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 soluble in an alkali developer, while the unexposed portion becomes alkaline. Since it remains insoluble in the developer and does not change, alkali development can be performed.

<(A) component>
In the present invention, the component (A) contains the polymer (A1) having the structural unit (a0-1) represented by the general formula (a0-1).
In the present invention, in addition to the structural unit (a0-1), the component (A) preferably further has a structural unit (a0-2) represented by the general formula (a0-2) described later.
In the present invention, the component (A) is in addition to the structural unit (a0-1), or in addition to the structural unit (a0-1) and the structural unit (a0-2), and further has an acid dissociation property. Having at least one structural unit selected from a structural unit (a1) derived from an acrylate ester containing a dissolution inhibiting group and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group preferable.

Here, 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 lower alkyl group and a halogenated lower alkyl group.
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.
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 lower alkyl group, or a halogenated lower alkyl group, and preferably a hydrogen atom, a lower alkyl group, or a fluorinated lower alkyl group. In view of industrial availability, a hydrogen atom or a methyl group is most preferable.

・ Structural unit (a0-1)
The structural unit (a0-1) is a structural unit represented by the general formula (a0-1).
In general formula (a0-1), R represents a hydrogen atom, a lower alkyl group, or a halogenated lower alkyl group.
The lower alkyl group or halogenated lower alkyl group for R is the same as the lower alkyl group or halogenated lower alkyl group which may be bonded to the α-position of the acrylate ester. Among them, R is preferably a hydrogen atom or a methyl group.

In general formula (a0-1), Y ¹ represents 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 a polycyclic group having no aromaticity. The “aliphatic cyclic group” in the structural unit (a0-1) 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 structure of the basic ring (aliphatic ring) excluding the substituent of the “aliphatic cyclic group” is not limited to being a ring composed of carbon and hydrogen (hydrocarbon ring), but is a hydrocarbon ring. It is preferable. The “hydrocarbon ring” may be either saturated or unsaturated, but is usually preferably saturated.
The aliphatic cyclic group may be either a polycyclic group or a monocyclic group. Specific examples of the aliphatic cyclic group include a monocycloalkane, a bicycloalkane, a tricycloalkane, which may or may not be substituted with a lower alkyl group, a fluorine atom or a fluorinated alkyl group, for example. Examples include groups in which two or more hydrogen atoms have been removed from a polycycloalkane such as tetracycloalkane. Specific examples include monocycloalkanes such as cyclopentane and cyclohexane, and groups obtained by removing two or more hydrogen atoms from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
The aliphatic cyclic group in the structural unit (a0-1) is preferably a polycyclic group, and among them, a group obtained by removing two or more hydrogen atoms from adamantane is preferable.

In the general formula (a0-1), Z represents a tertiary alkyl group-containing group or an alkoxyalkyl group.
Here, in the present specification and claims, the “tertiary alkyl group” refers to an alkyl group having a tertiary carbon atom. As described above, the “alkyl group” represents a monovalent saturated hydrocarbon group, and includes a chain (straight chain or branched chain) alkyl group and an alkyl group having a cyclic structure.
The “tertiary alkyl group-containing group” refers to a group containing a tertiary alkyl group in its structure. The tertiary alkyl group-containing group may be composed only of a tertiary alkyl group, or may be composed of a tertiary alkyl group and another atom or group other than the tertiary alkyl group. .
Examples of the “atom or group other than the tertiary alkyl group” that constitutes the tertiary alkyl group-containing group together with the tertiary alkyl group include a carbonyloxy group, a carbonyl group, an alkylene group, an oxygen atom, and the like. .

Examples of the tertiary alkyl group-containing group of Z include a tertiary alkyl group-containing group having no cyclic structure, a tertiary alkyl group-containing group having a cyclic structure, and the like.
A tertiary alkyl group-containing group having no cyclic structure is a group containing a branched tertiary alkyl group as the tertiary alkyl group and having no cyclic structure in the structure.
Examples of the branched tertiary alkyl group include groups represented by the following general formula (I).

In formula (I), R ^{21 to} R ²³ are each independently a linear or branched alkyl group. 1-5 are preferable and, as for carbon number of this alkyl group, 1-3 are more preferable.
Moreover, it is preferable that the total carbon number of group represented by general formula (I) is 4-7, It is more preferable that it is 4-6, It is most preferable that it is 4-5.
Specific examples of the group represented by the general formula (I) include a tert-butyl group and a tert-amyl group, and a tert-butyl group is more preferable.

Examples of the tertiary alkyl group-containing group that does not have a cyclic structure include the above-described branched tertiary alkyl group; the above-described branched tertiary alkyl group is a linear or branched alkylene group A tertiary alkyl group-containing chain alkyl group bonded to the above; a tertiary alkyloxycarbonyl group having the branched tertiary alkyl group described above as the tertiary alkyl group; And tertiary alkyloxycarbonylalkyl groups having a branched tertiary alkyl group.
The alkylene group in the tertiary alkyl group-containing chain alkyl group is preferably an alkylene group having 1 to 5 carbon atoms, more preferably an alkylene group having 1 to 4 carbon atoms, and further preferably an alkylene group having 2 to 2 carbon atoms.
Examples of the chain-like tertiary alkyloxycarbonyl group include a group represented by the following general formula (II). ^R 21 ^{to R 23} in the formula (II) is the same as ^R 21 ^{to R 23} in general formula (I). The chain-like tertiary alkyloxycarbonyl group is preferably a tert-butyloxycarbonyl group (t-boc) or a tert-amyloxycarbonyl group.
Examples of the chain-like tertiary alkyloxycarbonylalkyl group include a group represented by the following general formula (III). ^R 21 ^{to R 23} in the formula (III) are the same as ^R 21 ^{to R 23} in general formula (I). f is an integer of 1 to 3, and 1 or 2 is preferable. As the chain-like tertiary alkyloxycarbonylalkyl group, a tert-butyloxycarbonylmethyl group and a tert-butyloxycarbonylethyl group are preferable.
Of these, the tertiary alkyl group-containing group having no cyclic structure is preferably a tertiary alkyloxycarbonyl group or a tertiary alkyloxycarbonylalkyl group, more preferably a tertiary alkyloxycarbonyl group. Most preferred is a tert-butyloxycarbonyl group.

The tertiary alkyl group-containing group having a cyclic structure is a group having a tertiary carbon atom and a cyclic structure in the structure.
In the tertiary alkyl group-containing group having a cyclic structure, the cyclic structure preferably has 4 to 12 carbon atoms, more preferably 5 to 10 carbon atoms, and more preferably 6 to 10 carbon atoms constituting the ring. Most preferred. Examples of the cyclic structure include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as monocycloalkane, bicycloalkane, tricycloalkane, and tetracycloalkane. Preferable 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 tertiary alkyl group-containing group having a cyclic structure include a group having the following group (1) or (2) as a tertiary alkyl group.
(1) A group in which a linear or branched alkyl group is bonded to a carbon atom constituting a ring of a cyclic alkyl group (cycloalkyl group), and the carbon atom is a tertiary carbon atom.
(2) A group in which an alkylene group having a tertiary carbon atom (branched alkylene group) is bonded to the carbon atom constituting the ring of the cycloalkyl group.

The linear or branched alkyl group in the group (1) preferably has 1 to 5 carbon atoms, more preferably 1 to 4 carbon atoms, and most preferably 1 to 3 carbon atoms. .
Specific examples of the group (1) include 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 1-methyl-1-cycloalkyl group, 1-ethyl-1-cycloalkyl group and the like. Can be mentioned.

In the above (2), the cycloalkyl group to which the branched alkylene group is bonded may have a substituent. Examples of the substituent include 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.
Specific examples of the group (2) include groups represented by the following general formula (IV).

In the formula (IV), R ²⁴ is a cycloalkyl group which may or may not have a substituent. Examples of the substituent that the cycloalkyl group may have include a fluorine atom, a fluorinated lower alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, and an oxygen atom (═O).
R ²⁵ and R ²⁶ are each independently a linear or branched alkyl group, and examples of the alkyl group include the same alkyl groups as R ^{21 to} R ²³ in the formula (I). It is done.

Examples of the alkoxyalkyl group for Z include groups represented by the following general formula (V).
In the formula, R ⁴¹ is a linear, branched or cyclic alkyl group.
When R ⁴¹ is linear or branched, it preferably has 1 to 5 carbon atoms, more preferably an ethyl group or a methyl group, and most preferably an ethyl group.
When R ⁴¹ is cyclic, it 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 groups excluding hydrogen atoms. Specific examples thereof 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.
^R42 is a linear or branched alkylene group. The alkylene group preferably has 1 to 5 carbon atoms, more preferably 1 to 3 carbon atoms, and still more preferably 1 to 2 carbon atoms.
As the alkoxyalkyl group for Z, a group represented by the following general formula (VI) is particularly preferable.

In the formula (VI), R ⁴¹ is the same as described above, and R ⁴³ and R ⁴⁴ each independently represents a linear or branched alkyl group or a hydrogen atom.
In R ⁴³ and R ⁴⁴ , 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 ⁴³ and R ⁴⁴ is a hydrogen atom and the other is a methyl group.

  Among these, as Z, a tertiary alkyl group-containing group is preferable, a group represented by the general formula (II) is more preferable, and a tert-butyloxycarbonyl group (t-boc) is most preferable.

In the general formula (a0-1), a is an integer of 1 to 3, b is an integer of 0 to 2, and a + b = 1 to 3.
a is preferably 1.
b is preferably 0.
a + b is preferably 1.
c is an integer of 0 to 3, preferably 0 or 1, and more preferably 0.
d is an integer of 0 to 3, preferably 0 or 1, and more preferably 0.
e is an integer of 0 to 3, preferably 0 or 1, and more preferably 0.

  As the structural unit (a0-1), a structural unit represented by general formula (a0-1-1) shown below is particularly desirable.

［式中、Ｒ，Ｚ，ｂ，ｃ，ｄ，ｅは前記と同じである。］

[Wherein R, Z, b, c, d and e are the same as described above. ]

  The monomer for deriving the structural unit (a0-1) is, for example, a compound represented by the following general formula (a0-1 ′) (an acrylate ester containing an aliphatic cyclic group having 1 to 3 alcoholic hydroxyl groups) ) Can be synthesized by protecting some or all of the hydroxyl groups with a tertiary alkyl group-containing group or an alkoxyalkyl group using a known method.

［式中、Ｒ，Ｙ^１，ａ，ｂ，ｃ，ｄ，ｅは前記と同じである。］

[Wherein, R, Y ¹ , a, b, c, d, and e are the same as described above. ]

As the structural unit (a0-1), one type of structural unit may be used alone, or two or more types of structural units may be used in combination.
The proportion of the structural unit (a0-1) in the component (A) is preferably 1 to 40 mol%, and preferably 1 to 25 mol%, based on the total of all the structural units constituting the component (A). Is more preferable, and it is further more preferable that it is 5-20 mol%. By setting it to the lower limit value or more, solubility in an organic solvent is improved. Moreover, the glass transition temperature of (A) component can be controlled low. If it is less than or equal to the upper limit value, the balance with other structural units is good.

・ Structural unit (a0-2)
The structural unit (a0-2) is a structural unit represented by the following general formula (a0-2).

［式（ａ０−２）中、Ｒは水素原子、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；Ｙ^３は脂肪族環式基であり；ｇ、ｈはそれぞれ独立して０〜３の整数であり；ｉは１〜３の整数である。］

[In the formula (a0-2), R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; Y ³ represents an aliphatic cyclic group; and g and h each independently represent an integer of 0 to 3. I is an integer of 1 to 3. ]

Examples of R in the general formula (a0-2) include the same as R in the formula (a0-1).
Examples of the aliphatic cyclic group for Y ³ include the same groups as those described above for Y ¹ in the formula (a0-1). Y ³ preferably has the same basic ring (aliphatic ring) structure as Y ¹ .
g is an integer of 0 to 3, preferably 0 or 1, and more preferably 0.
h is an integer of 0 to 3, preferably 0 or 1, and more preferably 0.
i is an integer of ˜3, preferably 1.

As the structural unit (a0-2), a structural unit represented by general formula (a0-2-1) shown below is particularly preferable. Among them, one of i — (CH ₂ ) _h —OH is It is preferably bonded to the 3-position of the 1-adamantyl group.

［式中、Ｒ，ｇ，ｈ，ｉは前記と同じである。］

[Wherein R, g, h and i are the same as described above. ]

As the structural unit (a0-2), one type of structural unit may be used alone, or two or more types of structural units may be used in combination.
The proportion of the structural unit (a0-2) in the component (A) is preferably 1 to 30 mol%, and preferably 5 to 25 mol%, based on the total of all structural units constituting the component (A). It is more preferable that the content is 10 to 20 mol%. By setting the lower limit value or more, the cross-sectional shape is highly rectangular, and a resist pattern having a good shape can be formed. If the upper limit value or less, the balance with other structural units is good.

・ Structural unit (a1)
The structural unit (a1) is a structural unit derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group.
The acid dissociable, dissolution inhibiting group in the structural unit (a1) has an alkali dissolution inhibiting property that makes the entire component (A) insoluble in an alkali developer before dissociation, and dissociates with an acid. This increases the solubility of the entire component in an alkaline developer, and those that have been proposed as acid dissociable, dissolution inhibiting groups for base resins for chemically amplified resists can be used. Generally, a group that forms a cyclic or chain tertiary alkyl ester with a carboxy group in (meth) acrylic acid or the like; an acetal-type acid dissociable, dissolution inhibiting group such as an alkoxyalkyl group is widely known. . 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 a chain or cyclic alkyl group, and the carbonyloxy group (—C (O)). A structure in which the tertiary carbon atom of the chain or cyclic alkyl group is bonded to the terminal oxygen atom of -O-). In this tertiary alkyl ester, when an acid acts, a bond is cut between an oxygen atom and a tertiary carbon atom.
The chain or cyclic 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.
Examples of the tertiary alkyl ester type acid dissociable, dissolution inhibiting group include an aliphatic branched acid dissociable, dissolution inhibiting group and an acid dissociable, dissolution inhibiting group 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.
“Aliphatic branched” means having a branched structure having no aromaticity. The structure of the “aliphatic branched acid dissociable, dissolution inhibiting 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.
As the aliphatic branched acid dissociable, dissolution inhibiting group, a tertiary alkyl group having 4 to 8 carbon atoms is preferable, and specific examples include a tert-butyl group, a tert-pentyl group, and a tert-heptyl group. .

The “aliphatic cyclic group” means a monocyclic group or a 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. The “aliphatic cyclic group” is preferably a polycyclic group.
Examples of the aliphatic cyclic group include monocycloalkanes, bicycloalkanes, tricycloalkanes, tetracycloalkanes that may or may not be substituted with a lower alkyl group, a fluorine atom or a fluorinated alkyl group. And groups obtained by removing one or more hydrogen atoms from a polycycloalkane. More 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 a cyclic alkyl group. Specifically, 2-methyl-2 -Adamantyl group, 2-ethyl-2-adamantyl group, etc. are mentioned. Alternatively, in the structural units represented by the following general formulas (a1 ″ -1) to (a1 ″ -6), an adamantyl group such as a group bonded to an oxygen atom of a carbonyloxy group (—C (O) —O—) An aliphatic cyclic group such as a cyclohexyl group, a cyclopentyl group, a norbornyl group, a tricyclodecanyl group, or a tetracyclododecanyl group, and a branched alkylene group having a tertiary carbon atom bonded thereto. Groups.

［式中、Ｒは上記と同じであり、Ｒ^１５、Ｒ^１６はアルキル基（直鎖状、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). ]

The “acetal-type acid dissociable, dissolution inhibiting group” is generally bonded to an oxygen atom by substituting a hydrogen atom at the terminal of an alkali-soluble group such as a carboxy group or a hydroxyl group. When an acid is generated by exposure, the acid acts to break the bond between the acetal acid dissociable, dissolution inhibiting group and the oxygen atom to which the acetal acid dissociable, dissolution inhibiting group is bonded.
Examples of the acetal type acid dissociable, dissolution inhibiting group include a group represented by the following general formula (p1).

［式中、Ｒ^１’，Ｒ^２’はそれぞれ独立して水素原子または低級アルキル基を表し、ｎは０〜３の整数を表し、Ｙは低級アルキル基または脂肪族環式基を表す。］

[Wherein, R ¹ ′ and R ² ′ each independently represents a hydrogen atom or a lower alkyl group, n represents an integer of 0 to 3, and Y represents a lower alkyl group or an aliphatic cyclic group. ]

In the above formula, n is preferably an integer of 0 to 2, more preferably 0 or 1, and most preferably 0.
Examples of the lower alkyl group for R ¹ ′ and R ² ′ include the same lower alkyl groups as those described above for R. A methyl group or an ethyl group is preferable, and a methyl group is most preferable.
In the present invention, it is preferable that at least one of R ¹ ′ and R ² ′ is a hydrogen atom. That is, the acid dissociable, dissolution inhibiting group (p1) is preferably a group represented by the following general formula (p1-1).

［式中、Ｒ^１’、ｎ、Ｙは上記と同様である。］

[Wherein R ¹ ′, n and Y are the same as described above. ]

Examples of the lower alkyl group for Y include the same lower alkyl groups as those described above for R.
The aliphatic cyclic group for Y can be appropriately selected from monocyclic or polycyclic aliphatic cyclic groups conventionally proposed in a number of ArF resists and the like. For example, the above “aliphatic ring” Examples thereof are the same as those in the formula group.

  Examples of the acetal type acid dissociable, dissolution inhibiting group also include a group represented by the following general formula (p2).

［式中、Ｒ^１７、Ｒ^１８はそれぞれ独立して直鎖状または分岐鎖状のアルキル基または水素原子であり、Ｒ^１９は直鎖状、分岐鎖状または環状のアルキル基である。または、Ｒ^１７およびＲ^１９がそれぞれ独立に直鎖状または分岐鎖状のアルキレン基であって、Ｒ^１７の末端とＲ^１９の末端とが結合して環を形成していてもよい。］

[Wherein, R ¹⁷ and R ¹⁸ each independently represent a linear or branched alkyl group or a hydrogen atom, and R ¹⁹ represents a linear, branched or cyclic alkyl group. Alternatively, R ¹⁷ and R ¹⁹ may be each independently a linear or branched alkylene group, and the end of R ^{17 and} the end of R ¹⁹ may be bonded to form a ring. ]

In R ¹⁷ and R ¹⁸ , 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 ¹⁷ and R ¹⁸ is a hydrogen atom and the other is a methyl group.
R ¹⁹ is a linear, branched or cyclic alkyl group, preferably having 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.
When R ¹⁹ is linear or branched, it preferably has 1 to 5 carbon atoms, more preferably an ethyl group or a methyl group, and most preferably an ethyl group.
When R ¹⁹ is cyclic, it 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 groups excluding hydrogen atoms. Specific examples thereof 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 ¹⁷ and R ¹⁹ are each independently a linear or branched alkylene group (preferably an alkylene group having 1 to 5 carbon atoms), and the end of R ^{19 and} the end of R ¹⁷ And may be combined.
In this case, a cyclic group is formed by R ¹⁷ , R ¹⁹ , the oxygen atom to which R ¹⁹ is bonded, and the carbon atom to which the oxygen atom and R ¹⁷ are bonded. The cyclic group is preferably a 4-7 membered ring, and more preferably a 4-6 membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

  As the structural unit (a1), one or more selected from the group consisting of structural units represented by the following general formula (a1-0-1) and structural units represented by the following general formula (a1-0-2): Is preferably used.

［式中、Ｒは水素原子、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は酸解離性溶解抑制基を示す。］

[Wherein, R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; and X ¹ represents an acid dissociable, dissolution inhibiting group. ]

［式中、Ｒは水素原子、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 lower alkyl group or a halogenated lower alkyl group; X ² represents an acid dissociable, dissolution inhibiting group; Y ² represents an alkylene group or an aliphatic cyclic group. ]

In general formula (a1-0-1), the lower alkyl group or halogenated lower alkyl group for R is the same as the lower alkyl group or halogenated lower alkyl group that may be bonded to the α-position of the acrylate ester. .
X ¹ is not particularly limited as long as it is an acid dissociable, dissolution inhibiting group, and examples thereof include the above-described tertiary alkyl ester type acid dissociable, dissolution inhibiting group and acetal type acid dissociable, dissolution inhibiting group. And tertiary alkyl ester type acid dissociable, dissolution inhibiting groups are preferred.

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 preferably an alkylene group having 1 to 4 carbon atoms or a divalent aliphatic cyclic group, except that a group in which two or more hydrogen atoms are removed is used as the aliphatic cyclic group. The same as described for the “aliphatic cyclic group” can be 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は炭素数１〜５の低級アルキル基、または脂肪族環式基を表し；ｎは０〜３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。］

[In the above formula, X ′ represents a tertiary alkyl ester type acid dissociable, dissolution inhibiting group, Y represents a lower alkyl group having 1 to 5 carbon atoms, or an aliphatic cyclic group; M represents 0 or 1; R is the same as defined above; R ¹ ′ and R ² ′ each independently represent a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms. ]

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

X ′ is the same as the 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) and (a1-1-35) to (a1- It is more preferable to use at least one selected from the group consisting of 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) The following general formula (a1-1-02) including the structural units of formulas (a1-1-35) to (a1-1-41) is also preferable.

（式中、Ｒは水素原子、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 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、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 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 component (A), the proportion of the structural unit (a1) is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, more preferably 25 to 50 mol%, based on all structural units constituting the component (A). Is more preferable. By setting it to the lower limit value or more, a pattern can be easily 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 structural unit (a2) is a structural unit derived from an acrylate ester containing a lactone-containing cyclic group.
Here, the lactone-containing cyclic 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. When only the lactone ring is present, it is called a monocyclic group. When it has another ring structure, it is called a polycyclic group regardless of the structure.
When the lactone cyclic group of the structural unit (a2) is used for forming a resist film, the lactone cyclic group increases the adhesion of the resist film to the substrate or has an affinity for a developer containing water. It is effective in raising.

As the structural unit (a2), any unit can be used without any particular limitation.
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.

  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、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の整数であり、Ａは炭素数１〜５のアルキレン基または酸素原子である。］

[Wherein, R is a hydrogen 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 an integer of 0 or 1. And A is an alkylene group having 1 to 5 carbon atoms or an oxygen atom. ]

R in the general formulas (a2-1) to (a2-5) is the same as R in the structural unit (a1).
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.
Specific examples of the alkylene group having 1 to 5 carbon atoms of A include a methylene group, an ethylene group, an n-propylene group, and an isopropylene group.
Below, the specific structural unit of the said general formula (a2-1)-(a2-5) is illustrated.

In the component (A), as the structural unit (a2), one type of structural unit may be used alone, or two or more types may be used in combination.
As the structural unit (a2), it is preferable to use at least one selected from the group consisting of the general formulas (a2-1) to (a2-5), and the general formulas (a2-1) to (a2-3) More preferably, at least one selected from the group consisting of: Among them, chemical formulas (a2-1-1), (a2-1-2), (a2-2-1), (a2-2-2), (a2-3-1), (a2-3-2) ), (A2-3-9) and (a2-3-10), it is preferable to use at least one selected from the group consisting of.

  The proportion of the structural unit (a2) in the component (A) is preferably from 5 to 60 mol%, more preferably from 10 to 50 mol%, more preferably from 20 to 50 mol based on the total of all structural units constituting the component (A). More preferred is mol%. 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 it to the upper limit value or less, it is possible to balance with other structural units.

-Other structural unit (A) component is a structural unit other than the said structural unit (a0-1), (a0-2), (a1), and (a2) in the range which does not impair the effect of this invention. May be included.
Other structural units are not particularly limited as long as they are other structural units not classified into the above structural units (a0-1), (a0-2), (a1), and (a2). ArF Many conventionally known ones can be used as resist resins for excimer lasers, KrF excimer lasers (preferably for ArF excimer lasers), and the like.
Examples of other structural units include the structural units (a3) to (a4) shown below.

・ Structural unit (a3)
The structural unit (a3) is derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group, and does not include the structural unit represented by the general formula (a0-1) or (a0-2). It is a structural unit.
When the component (A) has the structural unit (a3), the hydrophilicity of the component (A) is increased, the affinity with the developer is increased, the alkali solubility in the exposed area is improved, and the resolution is improved. Contributes to improvement.
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). It is done.
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. The polycyclic group preferably has 7 to 30 carbon atoms.
Among them, a structural unit derived from an acrylate ester containing 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 Is more preferable. Examples of the polycyclic group include groups in which two or more hydrogen atoms have been removed from bicycloalkane, tricycloalkane, tetracycloalkane and the like. Specific examples include groups in which two or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. 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 the following formula (a3-2), or the like is preferable. It is mentioned as a thing.

（式中、Ｒは前記と同じであり、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, k is an integer of 1 to 3, t ′ is an integer of 1 to 3, l is an integer of 1 to 5, and s is an integer of 1 to 3. .)

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

  In formula (a3-2), 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 acrylic acid. The fluorinated alkyl alcohol is preferably bonded to the 5th or 6th position of the norbornyl group.

  When the structural unit (a3) is contained in the component (A), the proportion of the structural unit (a3) is preferably 1 to 30 mol% with respect to the total of all the structural units constituting the component (A). 30 mol% is more preferable and 10-20 mol% is further more preferable.

・ Structural unit (a4)
The structural unit (a4) is a structural unit derived from an acrylate ester containing a non-acid-dissociable aliphatic polycyclic group.
Examples of the polycyclic group in the structural unit (a4) include those similar to those exemplified in the case of the structural unit (a1). For ArF excimer lasers and KrF excimer lasers (preferably A number of hitherto known materials can be used as the resin component of a resist composition such as ArF excimer laser).
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 have a linear or branched alkyl group having 1 to 5 carbon atoms as a substituent.
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.)

  When the structural unit (a4) is contained in the component (A), the proportion of the structural unit (a4) is preferably 1 to 30 mol% with respect to the total of all the structural units constituting the component (A). 20 mol% is more preferable.

In the present invention, the component (A) is a resin component containing a polymer (A1) having at least the structural unit (a0-1) represented by the general formula (a0-1). Moreover, the mass mean molecular weight of the said polymer (A1) is 4000-7000.
As the component (A), one type of polymer may be used alone, or two or more types may be used in combination.

[Polymer (A1)]
The polymer (A1) is a polymer (A1) having at least the structural unit (a0-1). Specifically, the polymer (A1) has a copolymer (A1-1) having a structural unit (a0-1) and a structural unit (a0-2); a structural unit (a0-1), And the polymer (A1-2) etc. which do not have a structural unit (a0-2) are mentioned, The said copolymer (A1-1) is preferable.
Examples of the copolymer (A1-1) include terpolymers composed of the structural units (a0-1), (a0-2), and (a1); the structural units (a0-1), ( Examples thereof include quaternary copolymers composed of a0-2), (a1) and (a2).
Examples of the polymer (A1-2) include a copolymer composed of the structural units (a0-1) and (a1); and 3 composed of the structural units (a0-1), (a1), and (a2). An original copolymer etc. can be illustrated.

  In the present invention, the polymer (A1) is particularly preferably a copolymer (A1-11) having four structural units in the combination represented by the following general formula (A1-11).

［式（Ａ１−１１）中、Ｒ，Ｒ^２１〜Ｒ^２３，ｅは上記と同様であり、複数のＲは相互に同じであっても異なっていてもよく、Ｒ^１０は低級アルキル基である。］

[In the formula (A1-11), R, R ^{21 to} R ²³ and e are the same as described above, and a plurality of R may be the same or different from each other, and R ¹⁰ is a lower alkyl group. . ]

In formula (A1-11), examples of the lower alkyl group for R ¹⁰ include the same lower alkyl groups as those described above for R ¹⁰ . R ¹⁰ is preferably a methyl group or an ethyl group, and most preferably an ethyl group.

In the polymer (A1), the proportion of the structural unit (a0-1) is preferably 1 to 40 mol%, and preferably 1 to 25 mol%, based on the total of all the structural units constituting the polymer (A1). It is more preferable that it is 5-20 mol%.
The proportion of the structural unit (a0-2) is preferably 1 to 30 mol%, more preferably 5 to 25 mol%, based on the total of all the structural units constituting the polymer (A1). More preferably, it is 10-20 mol%.
The proportion of the structural unit (a1) is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, still more preferably 25 to 50 mol%, based on the total of all structural units constituting the polymer (A1). .
The proportion of the structural unit (a2) is preferably from 5 to 60 mol%, more preferably from 10 to 50 mol%, still more preferably from 20 to 50 mol%, based on the total of all structural units constituting the polymer (A1). .
The proportion of the structural unit (a3) is preferably 1 to 30 mol%, more preferably 5 to 30 mol%, and more preferably 10 to 20 mol% with respect to the total of all the structural units constituting the polymer (A1). Is more preferable.
1-30 mol% is preferable with respect to the sum total of all the structural units which comprise a polymer (A1), and, as for the ratio of a structural unit (a4), 10-20 mol% is more preferable.

In the component (A), the polymer (A1) may be used alone or in combination of two or more.
The proportion of the polymer (A1) in the component (A) is preferably 50% by mass or more, more preferably 60% by mass or more, particularly preferably 70% by mass or more, and 100% by mass. Most preferably. When the ratio of the polymer (A1) is at least the lower limit value, the depth of focus (DOF) characteristics are further improved.

The mass average molecular weight of the polymer (A1) is 4000 to 7000, preferably 4500 to 7000, and more preferably 5000 to 7000.
When the mass average molecular weight of the polymer (A1) is 4000 to 7000, the depth of focus (DOF) characteristics are excellent. Moreover, when it is below the upper limit of this range, the solubility with respect to an alkali developing solution will become favorable, and when it is more than the lower limit of this range, dry etching resistance and resist pattern cross-sectional shape will be favorable.
In the present specification and claims, “mass average molecular weight” refers to a value in terms of polystyrene conversion by gel permeation chromatography (GPC).
In addition, the dispersity (Mw / Mn) of the polymer (A1) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5. In addition, Mn shows a number average molecular weight.

Moreover, as a suitable thing of (A) component, at least 1 type of the copolymer (A1-1) which has both a structural unit (a0-1) and a structural unit (a0-2) as mentioned above is included. It may be contained, or may be a mixture of a polymer (A1) having at least the structural unit (a0-1) and a polymer having at least the structural unit (a0-2).
In the case of the latter mixture, the component (A) includes, for example, the copolymer (A1-1) and the structural unit (a0-2) and the structural unit (a0-1). What contains the polymer (A2) which does not carry out is mentioned as a suitable thing.

[Polymer (A2)]
Examples of the polymer (A2) include a copolymer comprising the structural unit (a0-2) and any one or more of the structural units (a1) to (a4) described above. Specific examples include a copolymer composed of the structural units (a0-2) and (a1), a copolymer composed of the structural units (a0-2), (a1) and (a2), and the like.
As such a copolymer, for example, a copolymer composed of three structural units excluding the structural unit corresponding to the structural unit (a0-1) in the general formula (A1-11); The copolymer represented by -11) is preferable.

［式（Ａ２−１１）中、Ｒは上記と同様であり、複数のＲは相互に同じであっても異なっていてもよく、Ｒ^２０は低級アルキル基である。］

[In formula (A2-11), R is as defined above, and the plurality of R may be the same as or different from each other, and R ²⁰ represents a lower alkyl group. ]

In formula (A2-11), examples of the lower alkyl group for R ²⁰ include the same lower alkyl groups for R. R ²⁰ is preferably a methyl group or an ethyl group, and most preferably a methyl group.

In the polymer (A2), the proportion of the structural unit (a0-2) is preferably 1 to 30 mol%, and preferably 5 to 25 mol% with respect to the total of all the structural units constituting the polymer (A2). It is more preferable that it is 10-20 mol%.
The proportion of the structural unit (a1) is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, still more preferably 25 to 50 mol%, based on the total of all structural units constituting the polymer (A2). .
The proportion of the structural unit (a2) is preferably from 5 to 60 mol%, more preferably from 10 to 50 mol%, still more preferably from 20 to 50 mol%, based on the total of all structural units constituting the polymer (A2). .
The proportion of the structural unit (a3) is preferably 5 to 50 mol%, more preferably 5 to 40 mol%, and more preferably 5 to 25 mol% with respect to the total of all the structural units constituting the polymer (A2). Is more preferable.
1-30 mol% is preferable with respect to the sum total of all the structural units which comprise a polymer (A2), and, as for the ratio of a structural unit (a4), 10-20 mol% is more preferable.

  In the component (A), the polymer (A2) may be used alone or in combination of two or more.

The mass average molecular weight (Mw) of the polymer (A2) (polystyrene conversion standard by gel permeation chromatography) is preferably 2000 to 50000, more preferably 3000 to 30000, and most preferably 5000 to 20000. If it is below the upper limit of this range, it has sufficient solubility in a resist solvent to be used as a resist, and if it is above the lower limit of this range, dry etching resistance and resist pattern cross-sectional shape are good.
Further, the dispersity (Mw / Mn) of the polymer (A2) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

  In the present invention, when the component (A) contains the polymer (A1) and the polymer (A2), the mixing ratio of the polymer (A1) and the polymer (A2) is (A1 ) :( A2) = 9: 1 to 1: 9 is preferable, 9: 1 to 2: 8 is more preferable, 8: 2 to 5: 5 is particularly preferable, and 8: 2 Most preferably it is ~ 6: 4. By setting the mixing ratio within the above range, a positive resist composition having excellent DOF characteristics can be easily obtained. Moreover, it becomes easy to form a resist pattern with good lithography characteristics.

The component (A) 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).
In addition, the component (A) is used in combination with a chain transfer agent such as, for example, HS—CH ₂ —CH ₂ —CH ₂ —C (CF ₃ ) ₂ —OH at the time of the polymerization. A —C (CF ₃ ) ₂ —OH group may be introduced into the. 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

(A) The mass average molecular weight (Mw) of the whole component (polystyrene conversion standard by gel permeation chromatography) is preferably 2000 to 50000, more preferably 3000 to 30000, and most preferably 5000 to 20000. If it is below the upper limit of this range, it has sufficient solubility in a resist solvent to be used as a resist, and if it is above the lower limit of this range, dry etching resistance and resist pattern cross-sectional shape are good.
Moreover, 1.0-5.0 are preferable, as for the dispersity (Mw / Mn) of the whole (A) component, 1.0-3.0 are more preferable, and 1.2-2.5 are the most preferable.
In the present invention, the content of the component (A) in the positive resist composition may be adjusted according to the resist film thickness to be formed.

<(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, and poly (bissulfonyl) diazomethanes. There are various known diazomethane acid generators, nitrobenzyl sulfonate acid generators, imino sulfonate acid generators, disulfone acid generators, and the like.

  As the onium salt acid generator, for example, a compound represented by the following general formula (b-1) or (b-2) can be used.

［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；式（ｂ−１）におけるＲ^１”〜Ｒ^３”のうち、いずれか２つが相互に結合して式中のイオウ原子と共に環を形成してもよく；Ｒ^４”は、直鎖状、分岐鎖状もしく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; among R ¹ ″ to R ³ ″ in formula (b-1), Any two may be bonded together to form a ring with the sulfur atom in the formula; R ⁴ ″ represents a linear, branched or cyclic alkyl group or a fluorinated alkyl group; R ¹ At least one of “˜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. In addition, any two of R ¹ ″ to R ³ ″ in formula (b-1) may be bonded to each other to form a ring together with the sulfur atom in the formula.
Further, 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 of 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, a hydroxyl group 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.
As the alkoxy group that may be substituted for the hydrogen atom of the aryl group, an alkoxy group having 1 to 5 carbon atoms is preferable, and a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, Most preferred is a tert-butoxy 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, linear C1-10, branched or cyclic alkyl group, and the like. 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, R ¹ ″ to R ³ ″ are most preferably a phenyl group or a naphthyl group, respectively.

When any two of R ¹ ″ to R ³ ″ in the formula (b-1) are bonded to each other to form a ring together with the sulfur atom in the formula, a 3 to 10 membered ring including the sulfur atom is formed. It is preferable that a 5- to 7-membered ring is formed. When any two of R ¹ ″ to R ³ ″ in formula (b-1) are bonded to each other to form a ring together with the sulfur atom in the formula, the remaining one may be an aryl group preferable. Examples of the aryl group include the same aryl groups as those described above for R ¹ ″ to R ³ ″.

R ⁴ ″ represents a linear, branched or cyclic alkyl group or a fluorinated alkyl group.
The linear or branched 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 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. 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%. Particularly, all the hydrogen atoms are substituted with fluorine atoms. A fluorinated alkyl group (perfluoroalkyl group) is preferable because the strength of the acid is increased.
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. It is preferable that all of R ⁵ ″ to R ⁶ ″ are 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.
As the alkyl group for R ⁵ ″ to R ⁶ ″, the same as the alkyl groups for R ¹ ″ to R ³ ″ can be used.
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 acid generators represented by the formulas (b-1) and (b-2) include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, bis (4-tert-butylphenyl) iodonium. Trifluoromethane sulfonate or nonafluorobutane sulfonate; triphenylsulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate; tri (4-methylphenyl) sulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its Nonafluorobutanesulfonate; dimethyl (4-hydroxynaphthyl) sulfonium trifluoromethanesulfonate, its heptaful Lopropane sulfonate or its nonafluorobutane sulfonate; trifluoromethane sulfonate of monophenyldimethylsulfonium, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate; trifluoromethane sulfonate of diphenyl monomethylsulfonium, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate (4-methylphenyl) diphenylsulfonium trifluoromethanesulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate; (4-methoxyphenyl) diphenylsulfonium trifluoromethanesulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate; Trifluoromethanesulfonate of tri (4-tert-butyl) phenylsulfonium, its heptafluoropropane sulfonate or its nonafluorobutanesulfonate; trifluoromethanesulfonate of diphenyl (1- (4-methoxy) naphthyl) sulfonium, its heptafluoropropane Sulfonate or its nonafluorobutane sulfonate; trifluoromethane sulfonate of di (1-naphthyl) phenylsulfonium, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate; 1-phenyltetrahydrothiophenium trifluoromethane sulfonate, its heptafluoropropane sulfonate Or nonafluorobutanesulfonate thereof; 1- (4-methylphenyl) ) Tetrahydrothiophenium trifluoromethanesulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate; 1- (3,5-dimethyl-4-hydroxyphenyl) tetrahydrothiophenium trifluoromethanesulfonate, its heptafluoropropane sulfonate 1- (4-methoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate; 1- (4-ethoxynaphthalene-1- Yl) tetrahydrothiophenium trifluoromethanesulfonate, its heptafluoropropanesulfonate or its nonaflu 1- (4-n-butoxynaphthalen-1-yl) tetrahydrothiophenium trifluoromethanesulfonate, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate; 1-phenyltetrahydrothiopyranium trifluoromethanesulfonate , Its heptafluoropropane sulfonate or its nonafluorobutane sulfonate; 1- (4-hydroxyphenyl) tetrahydrothiopyranium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate; 1- (3,5-dimethyl -4-Hydroxyphenyl) tetrahydrothiopyranium trifluoromethanesulfonate, its heptafluoropropanes Honeto or nonafluorobutanesulfonate; 1- (4-methylphenyl) trifluoromethanesulfonate tetrahydrothiophenium Pila chloride, heptafluoropropane sulfonate or its nonafluorobutane sulfonate, and the like.
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.

  In addition, in the general formula (b-1) or (b-2), an onium salt-based acid generator in which the anion moiety is replaced with an anion moiety represented by the following general formula (b-3) or (b-4). 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, Most preferably, it has 3 carbon atoms.
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, Has 1 to 7 carbon atoms, more preferably 1 to 3 carbon atoms.
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 ″, the strength of the acid increases as the number of hydrogen atoms substituted with fluorine atoms 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.

  Moreover, the sulfonium salt which has a cation part represented by the following general formula (b-5) or (b-6) can also be used as an onium salt type | system | group acid generator.

［式中、Ｒ^４１”〜Ｒ^４６”はそれぞれ独立してアルキル基、アセチル基、アルコキシ基、カルボキシ基、水酸基またはヒドロキシアルキル基であり；ｎ_１〜ｎ_５はそれぞれ独立して０〜３の整数であり、ｎ_６は０〜２の整数である。］

[Wherein, R ⁴¹ ″ and R ⁴⁶ ″ each independently represents an alkyl group, an acetyl group, an alkoxy group, a carboxy group, a hydroxyl group or a hydroxyalkyl group; n _{1 to} n ₅ each independently represents 0 to 3; it is an integer, _{n 6} is an integer of 0-2. ]

In R ⁴¹ ″ to R ⁴⁶ ″, the alkyl group is preferably an alkyl group having 1 to 5 carbon atoms, more preferably a linear or branched alkyl group, and a methyl group, an ethyl group, a propyl group, or an isopropyl group. , N-butyl group, or tert-butyl group is particularly preferable.
The alkoxy group is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a linear or branched alkoxy group, and particularly preferably a methoxy group or an ethoxy group.
The hydroxyalkyl group is preferably a group in which one or more hydrogen atoms in the alkyl group are substituted with a hydroxy group, and examples thereof include a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group.
When the symbols n _{1 to} n ₆ attached to R ⁴¹ ″ to R ⁴⁶ ″ are integers of 2 or more, the plurality of R ⁴¹ ″ to R ⁴⁶ ″ may be the same or different.
n ₁ is preferably 0 to 2, more preferably 0 or 1, and still more preferably 0.
n ₂ and n ₃ are preferably each independently 0 or 1, more preferably 0.
n ₄ is preferably 0 to 2, more preferably 0 or 1.
n ₅ is preferably 0 or 1, more preferably 0.
n ₆ is preferably 0 or 1, more preferably 1.

The anion part of the sulfonium salt having a cation part represented by the formula (b-5) or (b-6) is not particularly limited, and is the same as the anion part of the onium salt acid generators proposed so far. It may be a thing. Examples of the anion moiety include an anion moiety (R ⁵¹ SO ₃ ⁻ ) of the onium salt acid generator represented by the above general formula (b-0), the above general formula (b-1) or (b-2). Fluorinated alkyl sulfonate ions such as an anion moiety (R ^{4 ″} SO ₃ ⁻ ) of an onium salt acid generator represented by formula; an anion moiety represented by the above general formula (b-3) or (b-4) Among these, a fluorinated alkyl sulfonate ion is preferable, a fluorinated alkyl sulfonate ion having 1 to 4 carbon atoms is more preferable, and a linear perfluoroalkyl sulfonate ion having 1 to 4 carbon atoms. Specific examples include trifluoromethyl sulfonate ion, heptafluoro-n-propyl sulfonate ion, nonafluoro-n-butyl sulfonate ion, and the like. I can get lost.

  In this specification, the oxime sulfonate 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. is there. Such oxime sulfonate-based acid generators are frequently used for chemically amplified resist compositions, and can be arbitrarily selected and used.

（式（Ｂ−１）中、Ｒ^３１、Ｒ^３２はそれぞれ独立に有機基を表す。）

(In formula (B-1), R ³¹ and R ³² each independently represents an organic group.)

The organic groups of R ³¹ and R ³² are groups containing carbon atoms, and atoms other than carbon atoms (for example, hydrogen atoms, oxygen atoms, nitrogen atoms, sulfur atoms, halogen atoms (fluorine atoms, chlorine atoms, etc.), etc.) You may have.
As the organic group for R ^31, a linear, branched, or cyclic alkyl group or aryl group is preferable. 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 ³¹ is particularly preferably an alkyl group having 1 to 4 carbon atoms or a fluorinated alkyl group having 1 to 4 carbon atoms which has no substituent.

As the organic group for R ^32, a linear, branched, or cyclic alkyl group, aryl group, or cyano group is preferable. As the alkyl group and aryl group for R ^32, the same alkyl groups and aryl groups as those described above for R ³¹ can be used.
R ³² 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^３３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^３４はアリール基である。Ｒ^３５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 ³³ represents a cyano group, an alkyl group having no substituent, or a halogenated alkyl group. R ³⁴ is an aryl group. R ³⁵ represents an alkyl group having no substituent or a halogenated alkyl group. ]

［式（Ｂ−３）中、Ｒ^３６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^３７は２または３価の芳香族炭化水素基である。Ｒ^３８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 Formula (B-3), R ³⁶ represents a cyano group, an alkyl group having no substituent, or a halogenated alkyl group. R ³⁷ is a divalent or trivalent aromatic hydrocarbon group. ^R38 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 of R ³³ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and carbon atoms. Numbers 1 to 6 are most preferable.
R ³³ is preferably a halogenated alkyl group, more preferably a fluorinated alkyl group.
The fluorinated alkyl group for R ³³ is preferably such that the hydrogen atom of the alkyl group is 50% or more fluorinated, more preferably 70% or more fluorinated, and 90% or more fluorinated. Particularly preferred.

As the aryl group of R ³⁴ , 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 anthryl group, or a phenanthryl group. 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 of R ³⁴ 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 ³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbon atoms.
R ³⁵ is preferably a halogenated alkyl group, more preferably a fluorinated alkyl group.
The fluorinated alkyl group for R ³⁵ is preferably such that the hydrogen atom of the alkyl group is 50% or more fluorinated, more preferably 70% or more fluorinated, and 90% or more fluorinated. Particularly preferred is the strength of the acid generated. Most preferred 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 ³⁶ is the same as the alkyl group or halogenated alkyl group having no substituent for R ^33. Is mentioned.
Examples of the divalent or trivalent aromatic hydrocarbon group for R ³⁷ include groups obtained by further removing one or two hydrogen atoms from the aryl group for R ³⁴ .
Examples of the alkyl group or halogenated alkyl group having no substituent of R ³⁸ include the same alkyl groups or halogenated alkyl groups having no substituent as R ³⁵ described above.
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.
Further, an oxime sulfonate-based acid generator disclosed in JP-A-9-208554 (paragraphs [0012] to [0014] [chemical formula 18] to [chemical formula 19]), pamphlet of International Publication No. 04/074242, An oxime sulfonate-based acid generator disclosed in Examples 1 to 40) on pages 65 to 85 can also be suitably used.
Moreover, the following can be illustrated as a suitable thing.

  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.
Further, diazomethane acid generators disclosed in JP-A-11-035551, JP-A-11-035552, and JP-A-11-035573 can also be suitably used.
Examples of poly (bissulfonyl) diazomethanes include 1,3-bis (phenylsulfonyldiazomethylsulfonyl) propane and 1,4-bis (phenylsulfonyldiazo) disclosed in JP-A-11-322707. Methylsulfonyl) butane, 1,6-bis (phenylsulfonyldiazomethylsulfonyl) hexane, 1,10-bis (phenylsulfonyldiazomethylsulfonyl) decane, 1,2-bis (cyclohexylsulfonyldiazomethylsulfonyl) ethane, 1,3 -Bis (cyclohexylsulfonyldiazomethylsulfonyl) propane, 1,6-bis (cyclohexylsulfonyldiazomethylsulfonyl) hexane, 1,10-bis (cyclohexylsulfonyldiazomethylsulfonyl) decane, etc. Door can be.

(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, among them, an onium salt having an anion moiety represented by the general formula (b-3) or (b-4) as a component (B) and an onium salt having a fluorinated alkyl sulfonate ion as an anion. It is preferable to use at least one acid generator selected.
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 1-20 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.

<(D) 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 with time, and the like. It is preferable to contain.
Since a wide variety of components (D) have already been proposed, any known one may be used. Among them, aliphatic amines, particularly secondary aliphatic amines and tertiary aliphatic amines are used. preferable. 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. “Aliphatic cyclic group” means a monocyclic group or polycyclic group having no aromaticity. An aliphatic amine is an amine having one or more aliphatic groups, and the aliphatic groups preferably have 1 to 12 carbon atoms.
Examples of the aliphatic amine include an amine (alkyl amine or alkyl alcohol amine) or a cyclic amine 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 of alkylamines and alkyl alcohol amines include monoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine; diethylamine, di-n-propylamine, di- -Dialkylamines such as n-heptylamine, di-n-octylamine, dicyclohexylamine; trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-pentylamine, tri-n-hexylamine , Tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine, tri-n-decanylamine, tri-n-dodecylamine, and the like; diethanolamine, triethanolamine, diisopropanolamine Triisopropanolamine, di -n- octanol amines, alkyl alcohol amines tri -n- octanol amine. Among these, a trialkylamine having 5 to 10 carbon atoms is more preferable, and tri-n-pentylamine and tri-n-octylamine are most preferable.
Examples of the cyclic amine include heterocyclic compounds containing a nitrogen atom as a hetero atom. The heterocyclic compound may be monocyclic (aliphatic monocyclic amine) or polycyclic (aliphatic polycyclic amine).
Specific examples of the aliphatic monocyclic amine include piperidine and piperazine.
As the aliphatic polycyclic amine, those having 6 to 10 carbon atoms are preferable. Specifically, 1,5-diazabicyclo [4.3.0] -5-nonene, 1,8-diazabicyclo [5. 4.0] -7-undecene, hexamethylenetetramine, 1,4-diazabicyclo [2.2.2] octane, and the like.
These may be used alone or in combination of two or more.
In the present invention, it is particularly preferable to use a trialkylamine having 5 to 10 carbon atoms as the component (D).
(D) component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component.

<Optional component>
[(E) component]
The positive resist composition of the present invention includes, as optional components, organic carboxylic acids, phosphorus oxoacids and derivatives thereof for the purpose of preventing sensitivity deterioration, improving the resist pattern shape, retention stability over time, etc. At least one compound (E) selected from the group consisting of (hereinafter referred to as component (E)) can be contained.
As the organic carboxylic acid, for example, acetic acid, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid and the like are suitable.
Examples of phosphorus oxo acids and derivatives thereof include phosphoric acid, phosphonic acid, phosphinic acid and the like, and among these, phosphonic acid is particularly preferable.
Examples of the oxo acid derivative of phosphorus include esters in which the hydrogen atom of the oxo acid is substituted with a hydrocarbon group, and the hydrocarbon group includes an alkyl group having 1 to 5 carbon atoms and 6 to 6 carbon atoms. 15 aryl groups and the like.
Examples of phosphoric acid derivatives include phosphoric acid esters such as di-n-butyl phosphate and diphenyl phosphate.
Examples of phosphonic acid derivatives include phosphonic acid esters such as phosphonic acid dimethyl ester, phosphonic acid-di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester, and phosphonic acid dibenzyl ester.
Examples of the phosphinic acid derivatives include phosphinic acid esters such as phenylphosphinic acid.
(E) A component may be used individually by 1 type and may use 2 or more types together.
As the component (E), an organic carboxylic acid is preferable, and salicylic 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.

[(S) component]
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-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone; many such as ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol Monohydric alcohols: compounds having an ester bond such as ethylene glycol monoacetate, diethylene glycol monoacetate, propylene glycol monoacetate or dipropylene glycol monoacetate, monomethyl ether, monoethyl of the polyhydric alcohols or the compound having an ester bond Ether alkyl such as ether, monopropyl ether, monobutyl ether or monophenyl ether Derivatives of polyhydric alcohols such as compounds having a propylene glycol monomethyl ether acetate (PGMEA) or propylene glycol monomethyl ether (PGME) among these]; cyclic ethers such as dioxane, methyl lactate, Esters such as ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate; anisole, ethyl benzyl ether, cresyl methyl ether, diphenyl ether, Aromatic organics such as dibenzyl ether, phenetol, butyl phenyl ether, ethylbenzene, diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymene, mesitylene A solvent etc. can be mentioned.
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.
Of these, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), and EL are preferable.
Moreover, the mixed solvent which mixed PGMEA and the polar solvent is also preferable. The mixing ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, but is 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. Moreover, when mix | blending PGME as a polar solvent, the mass ratio of PGMEA: PGME becomes like this. Preferably it is 1: 9-9: 1, More preferably, it is 2: 8-8: 2, More preferably, it is 3: 7-7: 3.
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 component (S) used is not particularly limited, but it is a concentration that can be applied to a substrate or the like, and is appropriately set according to the coating film thickness. -20% by mass, preferably 5-15% by mass.

The positive resist composition of the present invention has an effect of excellent depth of focus (DOF) characteristics. The reason is not clear, but is presumed as follows.
Conventionally, in positive resist compositions used for ArF excimer laser lithography, etc., for the purpose of increasing affinity with a developer and improving alkali solubility in exposed areas, it contains polar groups. There is an aliphatic hydrocarbon group, for example, a resin having a structural unit having a structure of “—Y ¹ (aliphatic cyclic group) -OH”. In a resin having a structural unit having a structure of “—Y ¹ —OH”, a hydrogen bond based on “—OH” is formed between the resins, and the interaction between the resins is strengthened, so that the glass transition temperature is increased. . Moreover, when this hydrogen bond is formed with resin, the diffusibility of the acid generator contained in a resist composition will fall easily. On the other hand, in forming a resist pattern, the focus is shifted and the intensity of light or the like is weakened, so that the diffusibility of the acid generator is lowered.
When the diffusibility of the acid generator is lowered, for example, in the case of forming a hole pattern, there arises a problem that the hole size is reduced.
On the other hand, the polymer (A1) used in the present invention has a structural unit (a0-1) having a structure of “—Y ¹ — (CH ₂ ) _e —O—Z”. Z in the “—Y ¹ — (CH ₂ ) _e —O—Z” is a tertiary alkyl group-containing group or an alkoxyalkyl group, and when Z is a hydrogen atom, the hydrogen bond formed between the resins is It is thought that it is hardly formed. In addition, the polymer (A1) used in the present invention has a mass average molecular weight of 4000 to 7000, which is lower than the conventional one of about 10,000. Therefore, since the polymer (A1) used in the present invention has a relatively weak interaction between the polymers, the glass transition temperature is lower than the conventional one, and the diffusibility of the acid generator is not lowered. it is conceivable that.
Therefore, by using the polymer (A1) according to the present invention, the diffusibility of the acid generator is good even under the condition that the intensity of light or the like is weakened by shifting the focus, so that the depth of focus (DOF) It is presumed that the effect of excellent characteristics can be obtained.
Such an effect is particularly prominent in an isolated (Iso) resist pattern.

  In addition, the positive resist composition of the present invention has an effect that the solubility in an alkali developer is good. Due to this effect, the generation of precipitates (foreign matter) on the resist pattern surface is suppressed. The reason for this is that the polymer (A1) used in the present invention has a mass average molecular weight of 4000 to 7000, which is lower than the conventional one, so that the resist film containing the polymer (A1) is dissolved in an alkaline developer. Presumably due to increased speed.

Further, in the present invention, an effect that various lithography characteristics such as a mask error factor (MEF) are good is also obtained.
Here, “MEF” means masks of different sizes when the mask size (line width in a line and space pattern or hole diameter in a contact hole pattern) is changed with the same exposure amount and a fixed pitch. This parameter indicates how faithfully the pattern can be reproduced (mask reproducibility).
In the present invention, good lithography characteristics can be obtained even when the amount of the acid generator used is small.

≪Resist pattern formation method≫
The resist pattern forming method of the present invention comprises a step of forming a resist film on a support using the positive resist composition of the present invention, a step of exposing the resist film, and an alkali developing of the resist film to form a resist. It is a method including the process of forming a pattern.
The resist pattern forming method of the present invention can be performed, for example, as follows.
That is, first, the positive resist composition is coated on a support with a spinner or the like, and pre-baked (post-apply bake (PAB)) for 40 to 120 seconds, preferably 60 to 90, under a temperature condition of 80 to 150 ° C. For example, ArF excimer laser light is selectively exposed through a desired mask pattern using an ArF exposure apparatus or the like, and then subjected to PEB (post-exposure heating) at a temperature of 80 to 150 ° C. for 40 to 120. Second, preferably 60-90 seconds. Subsequently, this is developed with an alkali developer, for example, an aqueous solution of 0.1 to 10% by mass of tetramethylammonium hydroxide, preferably rinsed with pure water and dried. In some cases, a baking process (post-bake) may be performed after the development process. In this way, a resist pattern faithful to the mask pattern can be obtained.

The support is not particularly limited, and a conventionally known one can be used, and examples thereof include a substrate for electronic components and a substrate on which a predetermined wiring pattern is formed. More specifically, a silicon substrate, a metal substrate such as copper, chromium, iron, and aluminum, a glass substrate, and the like can be given. As a material for the wiring pattern, for example, copper, aluminum, nickel, gold or the like can be used.
In addition, the support may be a substrate in which an inorganic and / or organic film is provided on the above-described substrate. An inorganic antireflection film (inorganic BARC) is an example of the inorganic film. Examples of the organic film include an organic antireflection film (organic BARC).

The wavelength used for the 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, etc. Can be done using radiation. The positive resist composition is particularly effective for KrF excimer laser, ArF excimer laser, EB or EUV, and among them, it is effective for ArF excimer laser.

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

<Resin component (A)>
The copolymers (A1) -1 to (A1) -3 and the copolymer (A2) -1 of the component (A) used in Examples and Comparative Examples are monomers (1) to ( Using 6), they were synthesized according to the synthesis examples shown below.

[Synthesis example]
The copolymer (A1) -1 will be described as an example. PGMEA is placed in a four-necked flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer under a nitrogen atmosphere, and the temperature of the hot water bath is set to 80 with stirring. Raised to ° C.
Next, as a polymerization initiator, V-601 (trade name, manufactured by Wako Pure Chemical Industries, Ltd.), PGMEA, and a monomer (monomer (3) / monomer (5) derived from each constituent unit of copolymer (A1) -1 ) / Monomer (2) / monomer (1) = 4/4/1/1 (molar ratio)) is added into the flask over 6 hours at a constant rate using a dropping device. The solution was added dropwise, and then kept at 80 ° C. for 1 hour. Thereafter, the reaction solution was returned to room temperature.
Subsequently, the obtained reaction solution was added dropwise to about 30 times amount of methanol with stirring to obtain a colorless precipitate. The resulting precipitate was filtered off, and the precipitate was washed in about 30 times the amount of methanol used for the monomer used for the polymerization. And this precipitate was separated by filtration and it dried at 50 degreeC under pressure reduction for about 40 hours, and obtained copolymer (A1) -1.
Further, the synthesis of the copolymer (A1) -2, the copolymer (A1) -3, and the copolymer (A2) -1 is carried out by the method of synthesizing the copolymer (A1) -1. The monomer was synthesized by the same method as the method for synthesizing the copolymer (A1) -1, except that the monomer for deriving the structural unit was used at a predetermined molar ratio.

In the above synthesis example, the obtained copolymers (A1) -1 to (A1) -3 and copolymer (A2) -1 are shown below.
Copolymers (A1) -1 to (A1) -3 are represented by the following chemical formula (A1), have a common structural unit, and have different mass average molecular weights. The following chemical formula (A2) represents the copolymer (A2) -1.

The weight average molecular weight (Mw) and dispersity (Mw / Mn) of the copolymers (A1) -1 to (A1) -3 and the copolymer (A2) -1 are polystyrene measured by gel permeation chromatography (GPC). Calculated on a conversion basis.
Moreover, the code | symbol attached | subjected to the lower right of the structural unit () in the chemical formula of the said copolymer shows the ratio (mol%) of each structural unit in a copolymer. The proportion (mol%) of each structural unit in the copolymer was calculated by carbon NMR.
Table 1 shows the ratio (mol%) of each structural unit in the copolymer, the mass average molecular weight (Mw) and the dispersity (Mw / Mn) of each copolymer.

<Examples 1-6, Comparative Examples 1-2>
The components shown in Table 2 below were mixed and dissolved to prepare a positive resist composition.

  Each abbreviation in Table 2 has the following meaning. Moreover, the numerical value in [] is a compounding quantity (mass part).

(B) -1: a compound represented by the following formula (B) -1.

(B) -2: Triphenylsulfonium heptafluoro-n-propanesulfonate.
(B) -3: Triphenylsulfonium trifluoromethanesulfonate.
(D) -1: tri-n-pentylamine.
(S) -1: PGMEA / PGME = 6/4 mixed solvent.

  The following lithography characteristics were evaluated using the obtained positive resist composition. The results are shown in Table 3. In addition, the weight average molecular weight of the copolymer (polymer (A1)) corresponding to the chemical formula (A1) is also shown in Table 3.

[Resist pattern formation]
By applying an organic antireflection film composition “ARC29” (trade name, manufactured by Brewer Science Co., Ltd.) onto an 8-inch silicon wafer using a spinner, baking on a hot plate at 205 ° C. for 60 seconds and drying. An organic antireflection film having a thickness of 77 nm was formed.
On the organic antireflection film, the positive resist compositions of Examples 1 to 6 and Comparative Examples 1 and 2 were applied using a spinner, and prebaked (PAB) treatment at 120 ° C. for 60 seconds on a hot plate. Then, a resist film with a film thickness of 150 nm was formed by drying.
Next, an ArF excimer laser (193 nm) was applied to the resist film with a mask pattern (6% half) using an ArF exposure apparatus NSR-S306C (manufactured by Nikon Corporation; NA (numerical aperture) = 0.78, σ = 0.90). Tones).
The film was then subjected to post-exposure heating (PEB) treatment at 95 ° C. for 60 seconds, followed by development with an aqueous 2.38 mass% tetramethylammonium hydroxide (TMAH) solution at 23 ° C. for 30 seconds, and then pure water for 30 seconds. The sample was rinsed with water and shaken and dried.

  According to the above [resist pattern formation], a dense hole pattern (mask / pitch / print = 130 nm / 200 nm / 80 nm) having a diameter of 80 nm was formed in any of the examples.

[Sensitivity evaluation]
In the above [resist pattern formation], an optimum exposure amount (unit: mJ / cm ² (energy amount per unit area)) when a dense hole pattern having a diameter of 80 nm is formed was determined, and the value was defined as Eop. Are shown in Table 3.

[Evaluation of depth of focus (DOF)]
In the above Eop, the focus is shifted up and down by 50 nm in a range of −300 to 300 nm, a resist pattern is formed in the same manner as in the above [Registration pattern formation], and the depth of focus in the obtained isolated hole pattern (μm) Asked. The results are shown in Table 3.

  As is clear from the results in Table 3, it was confirmed that Examples 1 to 6 according to the present invention had a wider depth of focus and excellent DOF characteristics than Comparative Examples 1 and 2.

  In addition, Examples 3 to 4 according to the present invention were confirmed to have the same sensitivity as Comparative Example 1 with a small amount of acid generator, and to have DOF characteristics comparable to Examples 1 and 2.

[Evaluation of solubility in alkaline developer]
The state of each Dense hole pattern surface formed in the above [resist pattern formation] was observed with a scanning electron microscope (SEM), and the solubility in an alkaline developer was evaluated based on the following evaluation criteria. The results are shown in Table 4. In addition, Table 4 shows the mass average molecular weight of the polymer (A1) used.
(Evaluation criteria)
A: No precipitates (foreign matter) were observed on the hole pattern surface.
○: Slight deposits (foreign matter) were observed on the hole pattern surface.
X: Many precipitates (foreign matter) were observed on the hole pattern surface.

  From the results of Table 4, it was confirmed that Examples 3 to 4 according to the present invention have good solubility in an alkaline developer.

Claims (8)

A positive resist composition comprising a resin component (A) whose solubility in an alkaline developer is increased by the action of an acid, and an acid generator component (B) that generates an acid upon exposure,
The resin component (A) contains a polymer (A1) having a structural unit (a0-1) represented by the following general formula (a0-1), and the mass average molecular weight of the polymer (A1) is A positive resist composition, wherein the positive resist composition is 4000 to 7000.

[In the formula (a0-1), R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; Y ¹ represents an aliphatic cyclic group; Z represents a tertiary alkyl group-containing group or an alkoxyalkyl group. A is an integer of 1 to 3, b is an integer of 0 to 2, and a + b = 1 to 3; c, d, and e are each independently an integer of 0 to 3. . ] The positive resist composition according to claim 1, wherein the resin component (A) further has a structural unit (a0-2) represented by the following general formula (a0-2).

[In the formula (a0-2), R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; Y ³ represents an aliphatic cyclic group; and g and h each independently represent an integer of 0 to 3. I is an integer of 1 to 3. ]   The resin component (A) has a copolymer (A1-1) having the structural unit (a0-1) and the structural unit (a0-2), and the structural unit (a0-2). And the positive resist composition of Claim 2 containing the polymer (A2) which does not have the said structural unit (a0-1).   The ratio of the said structural unit (a0-1) in the said resin component (A) is 1-40 mol% with respect to the sum total of all the structural units which comprise the said resin component (A). The positive resist composition according to any one of the above.   The positive resist composition according to claim 1, wherein the resin component (A) further has a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group. .   The positive resist composition according to claim 1, wherein the resin component (A) further has a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group.   Furthermore, the positive resist composition as described in any one of Claims 1-6 containing a nitrogen-containing organic compound (D).   A step of forming a resist film on a support using the positive resist composition according to any one of claims 1 to 7, a step of exposing the resist film, and an alkali developing of the resist film to form a resist A resist pattern forming method comprising a step of forming a pattern.