JP2006003844A - Positive resist composition and method for forming resist pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a resist pattern having high resolution and low LER (line edge roughness). <P>SOLUTION: A chemically amplified positive resist composition contains a copolymer (A1) having (a1) a structural unit derived from a mono(α-lower alkyl)acrylate having an acid dissociable solubility suppressing group, (a2) a structural unit derived from a mono(α-lower alkyl) acrylate having a lactone-containing monocyclic or polycyclic group, and (a4) a structural unit derived from a poly (α-lower alkyl) acrylate comprising a precursor unit derived from an (α-lower alkyl) acrylate having a polycyclic alicyclic hydrocarbon group containing a hydroxyl group or a carboxyl group, wherein a crosslinking group expressed by general formula (I) is substituted for a hydrogen atom in the hydroxyl group or the carboxyl group and forms an intramolecular or intermolecular crosslink. In formula (I), A represents a bivalent or trivalent organic group, p represents an integer 1 to 3, and each of R<SP>1</SP>and R<SP>2</SP>independently represents a hydrogen atom or a straight or branched lower alkyl group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

With the miniaturization of semiconductor elements, development of lithography processes using, for example, an ArF excimer laser (193 nm) has been vigorously advanced. As the base resin of the chemically amplified resist for ArF excimer laser, a resin having high transparency with respect to ArF excimer laser is preferable.
For example, a resin having a structural unit derived from a (meth) acrylic acid ester having a polycyclic hydrocarbon group such as an adamantane skeleton in the ester portion has attracted attention, and many proposals have been made so far. (Patent Document 1 below).
Japanese Patent No. 2881969

  In recent years, with the rapid miniaturization of semiconductor elements, higher resolution is required. However, LER (Line Edge Roughness) has become a serious problem with the miniaturization of resist patterns.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a positive resist composition and a resist pattern forming method capable of forming a resist pattern with high resolution and low LER. .

  In order to achieve the above object, the positive resist composition of the present invention comprises a resin component (A) whose alkali solubility is changed by the action of an acid, and an acid generator component (B) which generates an acid upon exposure. Wherein the resin component (A) is a structural unit (a1) derived from a mono (α-lower alkyl) acrylate ester containing an acid dissociable, dissolution inhibiting group, a lactone-containing monocycle, or A structural unit (a2) derived from a mono (α-lower alkyl) acrylate ester having a polycyclic group, and a polycyclic alicyclic hydrocarbon group containing a hydroxyl group or a carboxyl group (α-lower alkyl) ) The hydrogen atom of the hydroxyl group or carboxyl group of the precursor unit derived from an acrylate ester is replaced with a crosslinking group represented by the following general formula (I), and crosslinked in the molecule or between the molecules. Characterized in that it contains a copolymer (A1) having a structural unit (a4) derived from are poly (alpha-lower alkyl) acrylate ester that is.

（式中、Ａは２価又は３価の有機基であり、ｐは１〜３の整数である。Ｒ^１、Ｒ^２はそれぞれ独立して、水素原子又は直鎖又は分岐状の低級アルキル基である。）

(In the formula, A is a divalent or trivalent organic group, and p is an integer of ¹ to ^3. R ¹ and R ² are each independently a hydrogen atom or a linear or branched lower alkyl group. .)

  In the resist pattern forming method of the present invention, the positive resist composition of the present invention is coated on a substrate, pre-baked, selectively exposed, subjected to PEB (post-exposure heating), and alkali-developed. Forming a resist pattern.

In the present specification, “(α-lower alkyl) acrylic acid ester” means one or both of an α-lower alkyl acrylic acid ester such as methacrylic acid ester and an acrylic acid ester. Here, the “α-lower alkyl acrylate ester” means that a hydrogen atom bonded to the α carbon atom of the acrylate ester is substituted with a lower alkyl group.
“Constituent unit” means a monomer unit constituting a polymer. In the present invention, a structure in which monomer units are cross-linked is also referred to as “structural unit”.
The “structural unit derived from (α-lower alkyl) acrylate ester” means a structural unit formed by cleavage of an ethylenic double bond of (α-lower alkyl) acrylate ester.
In the “(α-lower alkyl) acrylic acid” and “(α-lower alkyl) acrylic acid ester”, the “lower alkyl group” is preferably a straight chain having 1 to 5 carbon atoms unless otherwise specified. A branched alkyl group, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, isopentyl, neopentyl, etc. Groups are preferred.

  ADVANTAGE OF THE INVENTION According to this invention, the positive resist composition and resist pattern formation method which can form a resist pattern with high resolution and small LER are obtained.

Hereinafter, the present invention will be described in detail.
[Positive resist composition]
The positive resist composition of the present invention is a positive resist composition containing a resin component (A) whose alkali solubility is increased by the action of an acid and an acid generator component (B) which generates an acid upon exposure. A) A component contains a specific copolymer (A1).

-Copolymer (A1) (hereinafter sometimes referred to as component (A1))
The component (A1) has at least the following three structural units (a1), (a2), and (a4). The component (A1) may further have the following structural unit (a3).
(A1): A structural unit derived from a mono (α-lower alkyl) acrylic ester containing an acid dissociable, dissolution inhibiting group.
(A2): A structural unit derived from a mono (α-lower alkyl) acrylate ester having a lactone-containing monocyclic or polycyclic group.
(A4): The hydrogen atom of the hydroxyl group or carboxyl group of the precursor unit derived from an (α-lower alkyl) acrylate ester having a polycyclic alicyclic hydrocarbon group containing a hydroxyl group or a carboxyl group is A structural unit derived from a poly (α-lower alkyl) acrylate ester substituted with a crosslinking group represented by the formula (I) and crosslinked within a molecule or between molecules.
(A3): A structural unit derived from a mono (α-lower alkyl) acrylate ester having a polycyclic alicyclic hydrocarbon group containing a hydroxyl group or a carboxyl group.

（式中、Ａは２価又は３価の有機基であり、ｐは１〜３の整数である。Ｒ^１、Ｒ^２はそれぞれ独立して、水素原子又は直鎖又は分岐状の低級アルキル基である。）

(In the formula, A is a divalent or trivalent organic group, and p is an integer of ¹ to ^3. R ¹ and R ² are each independently a hydrogen atom or a linear or branched lower alkyl group. .)

Here, “mono” of mono (α-lower alkyl) acrylate means having one (α-lower alkyl) acrylate residue.
“Poly” in the poly (α-lower alkyl) acrylate ester means that it has two or more (α-lower alkyl) acrylate ester residues as is apparent from the general formula (I).
In the component (A1), both the structural unit derived from mono (α-lower alkyl) acrylate ester and the structural unit derived from poly (α-lower alkyl) acrylate ester are ethylenic diene. A polymer is formed by bonding with other adjacent structural units by cleavage of a heavy bond.

..Structural unit (a1)
The structural unit (a1) is a structural unit derived from a mono (α-lower alkyl) acrylic ester containing an acid dissociable, dissolution inhibiting group.
As the acid dissociable, dissolution inhibiting group, for example, a conventionally known one can be used and is not particularly limited.

As the structural unit (a1), for example, a structural unit derived from a mono (α-lower alkyl) acrylate ester containing a monocyclic or polycyclic group-containing acid dissociable dissolution inhibiting group, a chain acid dissociable dissolution inhibiting group Any of structural units derived from mono (α-lower alkyl) acrylic acid esters containing
The acid dissociable, dissolution inhibiting group is generally known to form a chain or cyclic tertiary alkyl ester with a side chain carboxyl group of (α-lower alkyl) acrylic acid. In particular, those containing a cyclic, monocyclic or polycyclic alicyclic hydrocarbon group, particularly preferably a polycyclic alicyclic hydrocarbon group are preferred. The hydrocarbon group is preferably saturated.

Examples of the monocyclic alicyclic hydrocarbon group include groups obtained by removing one hydrogen atom from cycloalkane and the like. Specific examples include groups in which one hydrogen atom has been removed from cyclohexane, cyclopentane, or the like.
Examples of the polycyclic alicyclic hydrocarbon group include groups in which one hydrogen atom has been removed from bicycloalkane, tricycloalkane, tetracycloalkane and the like. Specific examples include groups in which one hydrogen atom has been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Of these, an adamantyl group, a norbornyl group, and a tetracyclododecanyl group are industrially preferable.

Examples of the mono (α-lower alkyl) acrylic acid ester (monomer) containing a chain acid dissociable, dissolution inhibiting group that induces the structural unit (a1) include the following.
For example, tert-butyl (meth) acrylate, tert-amyl (meth) acrylate, tert-butyloxycarbonylmethyl (meth) acrylate, tert-amyloxycarbonylmethyl (meth) acrylate, tert-butyloxycarbonylethyl (meth) acrylate , Tert-amyloxycarbonylethyl (meth) acrylate, and the like. Of these, tert-butyl (meth) acrylate is particularly preferred.

  Specific examples of the structural unit (a1) derived from a mono (α-lower alkyl) acrylate ester (monomer) containing a monocyclic or polycyclic group-containing acid dissociable, dissolution inhibiting group include 1-methylcyclopentyl (meta ) A structural unit constituted by cleavage of ethylenic double bond of acrylate, a structural unit constituted by cleavage of ethylenic double bond of 1-ethylcyclopentyl (meth) acrylate, 1-methylcyclohexyl (meth) acrylate A structural unit constituted by cleavage of an ethylenic double bond, a structural unit constituted by cleavage of an ethylenic double bond of 1-ethylcyclohexyl (meth) acrylate, the following general formula (aI-1), ( Examples include structural units represented by aI-2) and (aI-3).

（式中、Ｒ^９は水素原子、又は直鎖又は分岐状の低級アルキル基であり、Ｒ^１０は直鎖又は分岐状の低級アルキル基である。）

(In the formula, R ⁹ is a hydrogen atom or a linear or branched lower alkyl group, and R ¹⁰ is a linear or branched lower alkyl group.)

（式中、Ｒ^９は水素原子、又は直鎖又は分岐状の低級アルキル基であり、Ｒ^２１およびＲ^２２はそれぞれ独立して直鎖又は分岐状の低級アルキル基である。）

(In the formula, R ⁹ is a hydrogen atom or a linear or branched lower alkyl group, and R ²¹ and R ²² are each independently a linear or branched lower alkyl group.)

（式中、Ｒ^９は水素原子、又は直鎖又は分岐状の低級アルキル基であり、Ｒ^２３は第３級アルキル基である。）

(Wherein R ⁹ is a hydrogen atom or a linear or branched lower alkyl group, and R ²³ is a tertiary alkyl group.)

The lower alkyl group (α-lower alkyl group) as R ⁹ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and includes a methyl group, an ethyl group, a propyl group, an isopropyl group, and n-butyl. Group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.
In general formula (aI-1), R ¹⁰ is preferably a lower linear or branched alkyl group having 1 to 5 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl. Group, pentyl group, isopentyl group, neopentyl group and the like. Among these, a methyl group and an ethyl group are preferable because they are easily available industrially.

In general formula (aI-2), R ²¹ and R ²² are each independently preferably a linear or branched lower alkyl group having 1 to 5 carbon atoms. Among them, it is industrially preferable that both R ²¹ and R ²² are methyl groups. Specifically, a structural unit derived from 2- (1-adamantyl) -2-propyl (α-lower alkyl) acrylate is used. Can be mentioned.
In the general formula (aI-3), R ²³ is a tertiary alkyl group such as a tert-butyl group or a tert-amyl group, and a case where it is a tert-butyl group is industrially preferable.
The group —COOR ²³ may be bonded to the 3 or 4 position of the tetracyclododecanyl group shown in the formula, but the bonding position cannot be specified. Similarly, the carboxyl group residue of the (α-lower alkyl) acrylate structural unit may be bonded to the position 8 or 9 shown in the formula, but the bonding position cannot be specified.

..Structural unit (a2)
The structural unit (a2) is a structural unit derived from a mono (α-lower alkyl) acrylate ester having a lactone-containing monocyclic or polycyclic group, and the ester side chain of the (α-lower alkyl) acrylate ester. Examples thereof include a structural unit in which a monocyclic group consisting of a lactone ring or a polycyclic alicyclic group having a lactone ring is bonded to the part.
At this time, the lactone ring indicates one ring containing an —O—C (O) — structure, and this is counted as the first ring. Therefore, here, in the case of only a lactone ring, it is called a monocyclic group, and when it has another ring structure, it is called a polycyclic group regardless of the structure.
Specific examples of the lactone-containing monocyclic or polycyclic group in the structural unit (a2) include a monocyclic group obtained by removing one hydrogen atom from γ-butyrolactone, and one hydrogen atom from a lactone ring-containing polycycloalkane. And a polycyclic group except for.

  Specific examples of the structural unit (a2) include structural units represented by the following general formulas (aII-1), (aII-2), and (aII-3), respectively.

（式中、Ｒ^１１、Ｒ^１２、Ｒ^１３は、それぞれ独立して水素原子、又は直鎖又は分岐状の低級アルキル基である。）

(In the formula, R ¹¹ , R ¹² and R ¹³ are each independently a hydrogen atom or a linear or branched lower alkyl group.)

（式中、Ｒ^１１は水素原子、又は直鎖又は分岐状の低級アルキル基である。）

(In the formula, R ¹¹ is a hydrogen atom or a linear or branched lower alkyl group.)

（式中、Ｒ^１１は水素原子、又は直鎖又は分岐状の低級アルキル基である。）

(In the formula, R ¹¹ is a hydrogen atom or a linear or branched lower alkyl group.)

（式中、Ｒ^１１は水素原子、又は直鎖又は分岐状の低級アルキル基である。ｍは０又は１である。）

(In the formula, R ¹¹ is a hydrogen atom or a linear or branched lower alkyl group. M is 0 or 1.)

（式中、Ｒ^１１は水素原子、又は直鎖又は分岐状の低級アルキル基である。）

(In the formula, R ¹¹ is a hydrogen atom or a linear or branched lower alkyl group.)

The lower alkyl group (α-lower alkyl group) as R ¹¹ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and includes a methyl group, an ethyl group, a propyl group, an isopropyl group, and n-butyl. Group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.

..Structural unit (a3)
The structural unit (a3) is a structural unit derived from a mono (α-lower alkyl) acrylate ester having a polycyclic alicyclic hydrocarbon group containing a hydroxyl group or a carboxyl group, and (α-lower alkyl) It is a structural unit in which a group in which at least one hydrogen atom of a polycyclic alicyclic hydrocarbon group is substituted with a hydroxyl group or a carboxyl group is bonded to an ester side chain portion of an acrylate ester.
Examples of the polycyclic alicyclic hydrocarbon group include groups in which one hydrogen atom has been removed from bicycloalkane, tricycloalkane, tetracycloalkane and the like. Specific examples include groups in which one hydrogen atom has been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Among these, an adamantyl group, a norbornyl group, and a tetracyclododecanyl group are industrially preferable, and an adamantyl group is particularly preferable.
The number of hydroxyl groups or carboxyl groups substituting for hydrogen atoms of the polycyclic alicyclic hydrocarbon group may be one or more, and the upper limit may be a substitutable number. Preferably it is 1-3. Both a hydroxyl group and a carboxyl group may be substituted on one polycyclic alicyclic hydrocarbon group.

  Specific examples of the structural unit (a3) include structural units represented by the following general formula (aIII).

（式中、Ｒ^１４は水素原子、又は直鎖又は分岐状の低級アルキル基である。ｎは１〜３の整数である。）

(In the formula, R ¹⁴ is a hydrogen atom or a linear or branched lower alkyl group. N is an integer of 1 to 3.)

The lower alkyl group (α-lower alkyl group) as R ¹⁴ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, and includes a methyl group, an ethyl group, a propyl group, an isopropyl group, and n-butyl. Group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.
Further, n in the general formula (aIII) is preferably 1, and it is preferable that one hydroxyl group is bonded to the 3-position of the adamantyl group.

..Structural unit (a4)
The structural unit (a4) is a hydrogen atom of the hydroxyl group or carboxyl group of a precursor unit derived from an (α-lower alkyl) acrylate ester having a polycyclic alicyclic hydrocarbon group containing a hydroxyl group or a carboxyl group. Is a structural unit derived from a poly (α-lower alkyl) acrylate ester substituted with a crosslinking group represented by the general formula (I) and crosslinked within or between molecules.
Here, the “precursor unit” is a monomer unit constituting the polymer and means a state before being crosslinked.

Examples of the precursor unit of the structural unit (a4) include the same units as the structural unit (a3). That is, in the structural unit (a4), the hydrogen atom of the hydroxyl group or carboxyl group of the structural unit (a3) is substituted with the crosslinking group, and another structural unit (hereinafter referred to as a structural unit of a crosslinking partner) is formed via the crosslinking group. Are also cross-linked.
The pre-crosslinking precursor unit and the cross-linking partner structural unit may be intramolecular cross-links constituting the same copolymer, and they are inter-molecular cross-links constituting different copolymers. It may be. Intermolecular crosslinking is preferred.

In the general formula (I), R ¹ and R ² are each independently a hydrogen atom or a linear or branched lower alkyl group. The lower alkyl group as R ¹ and R ² is preferably a linear or branched alkyl group having 1 to 6 carbon atoms, more preferably 1 to 5 carbon atoms, such as a methyl group, an ethyl group, a propyl group, or an isopropyl group. N-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.
More preferably, ^one of R ¹ and R ² is a hydrogen atom and the other is a methyl group.

The crosslinking group represented by the general formula (I) forms an acid dissociable group, and the acid dissociable group is dissociated by the action of an acid, whereby the effects of the present invention are obtained. In the structural unit (a4), it suffices if there is at least one acid-dissociable group, and therefore p is 1 or more, preferably 2 or 3.
In the case where A is divalent, in one structural unit (a4), one precursor unit and one structural unit of a crosslinking partner are crosslinked via a crosslinking group represented by the general formula (I). Is. In this case, when the divalent group [—O—CR ¹ R ² —] obtained by removing the organic group A from the general formula (I) is a residue B, if p is 1, the one precursor unit and One of the structural units of one crosslinking partner is bonded to the organic group A through the residue B, and the other is directly bonded to the organic group A. If p is 2, both the one precursor unit and one structural unit of the cross-linking partner are bonded to one organic group A through the residue B, respectively.
In the case where A is trivalent, one structural unit (a4) includes one precursor unit and two structural units of a crosslinking partner via a crosslinking group represented by the general formula (I). Cross-linked. In this case, if p is 1, one of the one precursor unit and two structural units of the cross-linking partner is bonded to the organic group A via the residue B, and the remaining two Is directly bonded to the organic group A. If p is 2, two of the one precursor unit and the two crosslinking partner structural units are bonded to the organic group A via the residue B, and the remaining one is directly Combined with an organic group A. When p is 3, all of the one precursor unit and the two cross-linking partner structural units are each bonded to one organic group A via the residue B.
When A is divalent, p is preferably 2, and when A is trivalent, p is preferably 3. It is particularly preferable that A is divalent and p is 2.

The structural unit of the cross-linking partner only needs to have an (α-lower alkyl) acrylic acid ester residue, and those exemplified as the structural unit (a3) can be preferably used.
The precursor unit before crosslinking and the structural unit of the crosslinking partner may have the same structure or may be different from each other, but are preferably the same. .

Specific examples of the organic group A include saturated or unsaturated aromatic or aliphatic hydrocarbon groups such as an alkylene group, a cyclohexylene group, and an arylene group (these are an ether group, a polyether group, an ester group, Oxygen atoms may be included), and saturated or unsaturated aromatic or aliphatic hydrocarbon groups which may have a different atom such as nitrogen.
More preferably, A is a linear, branched or cyclic alkylene group, alkylene ether group, cyclohexylene group or arylene group having 1 to 20 carbon atoms.

  Specific examples of the structural unit (a4) include structural units represented by the following general formula (II).

（式中、Ｒ^３〜Ｒ^８はそれぞれ独立して、水素原子、又は直鎖又は分岐状の低級アルキル基である。Ａは炭素数１〜８の直鎖状又は分岐状アルキレン基、又は炭素数４〜１０の脂環式基である。Ｘ、Ｙはそれぞれ独立して炭素数４〜１２の脂環式基であって、置換基として直鎖又は分岐状の低級アルキル基を有していてもよい。）

(In the formula, R ^{3 to} R ⁸ are each independently a hydrogen atom or a linear or branched lower alkyl group. A is a linear or branched alkylene group having 1 to 8 carbon atoms, or carbon. X and Y are each independently an alicyclic group having 4 to 12 carbon atoms, and has a linear or branched lower alkyl group as a substituent. May be.)

In the general formula (II), the lower alkyl group (α-lower alkyl group) as R ³ and R ⁴ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, such as a methyl group, an ethyl group, Examples include propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.
R ⁵ and R ⁶ are the same as R ¹ and R ² described above. R ⁷ and R ⁸ are the same as R ¹ and R ² .

  A is a linear or branched alkylene group having 1 to 8 carbon atoms or an alicyclic group having 4 to 10 carbon atoms. Specific examples of the linear or branched alkylene group as A include a methylene group, an ethylene group, an n-butane-1,4-diyl group, a propane-1,3-diyl group, and propane-1,2-diyl. Group, 2-methylpropane-1,3-diyl group, 2,2-dimethylpropane-1,3-diyl group and the like. Specific examples of the alicyclic group as A include a cycloalkane, bicycloalkane, tricycloalkane, tetracycloalkane, benzene, naphthalene, anthracene, or a hydrocarbon group in which one or more hydrogen atoms are linear or branched. Examples include groups in which two hydrogen atoms have been removed from the above-mentioned cyclic hydrocarbons substituted with. More specifically, a group obtained by removing two hydrogen atoms from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, and the like can be given. A is more preferably a linear or branched alkylene group having 1 to 4 carbon atoms.

X and Y are each independently an alicyclic group having 4 to 12 carbon atoms, and may have a linear or branched lower alkyl group as a substituent.
Specific examples of X and Y include a group in which two hydrogen atoms are removed from a bicycloalkane, tricycloalkane, tetracycloalkane or the like which may have a substituent. More specifically, a group obtained by removing two hydrogen atoms from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane, or the like can be given. Among these, a group in which two hydrogen atoms are removed from adamantane, norbornane, and tetracyclododecane is industrially preferable, and a group in which two hydrogen atoms are removed from adamantane is particularly preferable.

  As the substituent in X and Y, a linear or branched lower alkyl group having 1 to 4 carbon atoms is preferable. Although the substitution position is not particularly limited, among the carbon atoms constituting the alicyclic group as X and Y, carbon atoms other than the carbon atom bonded to the (α-lower alkyl) acrylate residue It is preferable that the substituent is bonded.

  More preferred examples of the structural unit (a4) include structural units represented by general formula (aIV) shown below.

（式中、Ｒ^３、Ｒ^４はそれぞれ独立して、水素原子、又は直鎖又は分岐状の低級アルキル基である。Ａは炭素数１〜８の直鎖状又は分岐状アルキレン基又は炭素数４〜１０の脂環式基である。Ｒ^１５、Ｒ^１６はそれぞれ独立して、直鎖又は分岐状の低級アルキル基である。）

(In the formula, R ³ and R ⁴ are each independently a hydrogen atom or a linear or branched lower alkyl group. A is a linear or branched alkylene group having 1 to 8 carbon atoms or a carbon number. 4 to 10 alicyclic groups, R ¹⁵ and R ¹⁶ are each independently a linear or branched lower alkyl group.)

In the formula (aIV), A and R ³ and R ⁴ are the same as described above.
The lower alkyl group as R ¹⁵ and R ¹⁶ is a linear or branched alkyl group having 1 to 5 carbon atoms, and includes a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert- A butyl group, a pentyl group, an isopentyl group, a neopentyl group and the like can be mentioned, and a methyl group is preferable. R ¹⁵ and R ¹⁶ may be the same as or different from each other. Preferably, both R ¹⁵ and R ¹⁶ are methyl groups.

  Among them, as the structural unit (a4), there is a structural unit in which A is a linear alkylene group having 4 carbon atoms (n-butane-1,4-diyl group) as represented by the following general formula (aV). preferable.

（式中、Ｒ^３、Ｒ^４はそれぞれ独立して、水素原子、又は直鎖又は分岐状の低級アルキル基である。Ｒ^１５、Ｒ^１６はそれぞれ独立して、直鎖又は分岐状の低級アルキル基である。）
一般式（ａＶ）において、Ｒ^３、Ｒ^４、Ｒ^１５、Ｒ^１６は前記と同じである。

(In the formula, R ³ and R ⁴ are each independently a hydrogen atom or a linear or branched lower alkyl group. R ¹⁵ and R ¹⁶ are each independently a linear or branched lower alkyl group. Group.)
In the general formula (aV), R ³ , R ⁴ , R ¹⁵ and R ¹⁶ are the same as described above.

  The copolymer (A1) having such structural units (a1), (a2), and (a4), for example, roughly has structural units (a1), (a2), and precursor units of the structural unit (a4). A copolymer (hereinafter, the copolymer before the crosslinking reaction may be referred to as a precursor polymer) is synthesized in advance, and a precursor unit is used using a crosslinking agent capable of deriving the crosslinking group represented by the general formula (I). It can form by carrying out a crosslinking reaction between. During the cross-linking reaction, all of the precursor units present in the precursor polymer may be cross-linked, or only a part may be cross-linked. When only some of the precursor units are cross-linked, in the copolymer (A1) after cross-linking, in addition to the structural unit (a4) formed by cross-linking, the non-cross-linked precursor unit is the structural unit (a3). ).

  Preferred examples of the copolymer (A1) include polymers having structural units represented by the following general formulas (III-1), (III-2), (III-3), and (III-4), Or the polymer which has a structural unit respectively represented by the following general formula (VI-1), (IV-2), (IV-3), and (IV-4) is mentioned. In these, the structural units represented by the general formulas (III-1) and (VI-1) correspond to the structural unit (a1) and are represented by the general formulas (III-2) and (VI-2). The structural unit corresponds to the structural unit (a2), the structural units represented by the general formulas (III-3) and (VI-3) correspond to the structural unit (a3), and the general formula (III-4). And the structural unit represented by (VI-4) corresponds to the structural unit (a4).

（式中、Ｒ¹⁴’、Ｒ¹⁶’、Ｒ¹⁷’、Ｒ¹⁸’は各々独立して水素原子又はメチル基を示し、好ましくはメチル基である。
Ｒ¹⁵’は炭素数１〜６の直鎖状又は分岐状のアルキル基を示し、好ましくはメチル基である。）

(Wherein R ¹⁴ ′, R ¹⁶ ′, R ¹⁷ ′ and R ¹⁸ ′ each independently represent a hydrogen atom or a methyl group, preferably a methyl group.
R ¹⁵ ′ represents a linear or branched alkyl group having 1 to 6 carbon atoms, preferably a methyl group. )

（式中、Ｒ¹⁹’、Ｒ²⁰’、Ｒ²¹’、Ｒ²²’は各々独立して水素原子又はメチル基を示し、好ましくはメチル基である。）

(In the formula, R ¹⁹ ′, R ²⁰ ′, R ²¹ ′ and R ²² ′ each independently represent a hydrogen atom or a methyl group, preferably a methyl group.)

Hereinafter, a method for synthesizing the copolymer (A1) will be described.
The component (A1) of the present invention is usually synthesized by [Method 1] or [Method 2] described in detail below, but the present invention is not limited to this method.

 [Method 1] The (A1) component of the present invention forms a structural unit (a4) after polymerization and a (meth) acrylic acid ester compound that forms the structural units (a1), (a2), and (a3) after polymerization. For example, as shown by the following general formula (II-1), a crosslinkable (meth) acrylic acid ester compound having two (meth) acrylic groups and a polymerization initiator are dissolved in an organic solvent, and suitable at an appropriate temperature. It is synthesized by maintaining the temperature for a short time and polymerizing.

（式中、Ｒ¹’は水素原子又はメチル基であり、Ｒ²’は多環の脂環式炭化水素基（好ましくは前記したＸ，Ｙと同定義）であり、Ｒ³’、Ｒ⁴’、Ｒ⁵’、Ｒ⁶’は各々独立して水素原子又は炭素数１〜６の直鎖状又は分岐状のアルキル基を表し、Ｒ⁷は炭素数１〜２０の直鎖状、分岐状または環状のアルキレン基、アルキレンエーテル基、シクロへキシレン基またはアリーレン基を表す。）

(Wherein R ¹ ′ is a hydrogen atom or a methyl group, R ² ′ is a polycyclic alicyclic hydrocarbon group (preferably defined as X and Y described above), and R ³ ′, R ⁴ ', R ⁵ ' and R ⁶ 'each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and R ⁷ is a linear or branched group having 1 to 20 carbon atoms. Or a cyclic alkylene group, an alkylene ether group, a cyclohexylene group or an arylene group.)

The organic solvent used is preferably a solvent that can dissolve both the above-mentioned (meth) acrylic acid ester compound and the resulting polymer. For example, 1,4-dioxane, acetone, tetrahydrofuran, 2-butanone, 4-methyl Examples include 2-pentanone.
The polymerization initiator to be used is not particularly limited, and examples thereof include azo compounds such as azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile), and organic peroxides such as benzoyl peroxide. Etc. are exemplified.
The polymerization conditions at this time can be appropriately set, but the polymerization temperature is usually preferably in the range of 50 to 150 ° C., and the polymerization time is preferably 1 hour to 10 hours, more preferably 4 hours. More than about.
Next, the polymer solution thus synthesized is diluted to a suitable solution viscosity with a good solvent such as tetrahydrofuran or 1,4-dioxane, and then injected into a large amount of poor solvent such as methanol or water. Precipitate. Then, the (A1) component of this invention can be obtained by filtering the deposit and fully drying.

[Method 2] In addition, the component (A1) of the present invention comprises, as an organic solvent, a (meth) acrylic acid ester compound and a polymerization initiator that form the structural units (a1), (a2), and (a3), respectively, after polymerization. A precursor polymer synthesized by dissolving and maintaining at a suitable temperature for a suitable time for polymerization is subjected to a crosslinking reaction using a crosslinkable polyvinyl ether compound that forms the structural unit (a4) after crosslinking. Can be synthesized.
The organic solvent used for the synthesis of the precursor polymer is preferably a solvent capable of dissolving both the above-mentioned (meth) acrylic acid ester compound and the obtained polymer, such as 1,4-dioxane, acetone, tetrahydrofuran, 2 -Butanone, 4-methyl-2-pentanone and the like are exemplified. The polymerization initiator used is not particularly limited. For example, azo compounds such as azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile), and organic peroxidation such as benzoyl peroxide. Examples are things.
The polymerization conditions at this time can be set as appropriate, but the polymerization temperature is preferably in the range of 50 to 150 ° C., and the reaction time is preferably 1 to 10 hours, more preferably 4 More than about hours. The precursor polymer solution thus obtained, or a crosslinking agent that separates the precursor polymer from the precursor polymer solution and then forms the structural unit (a4) after crosslinking in the precursor polymer solution dissolved in an appropriate solvent. And (A1) component of this invention are synthesize | combined by adding an acid catalyst and hold | maintaining the temperature for a suitable time at a suitable temperature, and performing a crosslinking reaction.
For separation of the precursor polymer, the precursor polymer solution is diluted to a suitable solution viscosity with a good solvent such as tetrahydrofuran or 1,4-dioxane, and then poured into a large amount of poor solvent such as methanol or water for precipitation. . Thereafter, the precipitate is filtered and sufficiently dried.
The solvent for dissolving the precursor polymer is preferably a solvent capable of dissolving the aforementioned precursor polymer, such as 1,4-dioxane, acetone, tetrahydrofuran, 2-butanone, 4-methyl-2-pentanone, and ethyl acetate. Illustrated.

  The cross-linking agent may be one that can form a cross-linked moiety in the structural unit (a4) represented by the general formula (I), and is not particularly limited. For example, a cross-linkable polyvinyl ether having two cross-linkable vinyl ether groups. Compounds can be used. Specific examples include ethylene glycol divinyl ether, triethylene glycol divinyl ether, 1,4-butanediol divinyl ether, tetramethylene glycol divinyl ether, neopentyl glycol divinyl ether, hexanediol divinyl ether, 1,4-cyclohexanediol divinyl ether. And tetraethylene glycol divinyl ether, pentaerythritol divinyl ether, cyclohexane dimethanol divinyl ether, and the like.

Although it does not specifically limit as an acid catalyst used, For example, p-toluenesulfonic acid, pyridinium-p-toluenesulfonate, a sulfuric acid etc. are illustrated.
The amount of the crosslinking agent used is determined by the amount for obtaining a preferred proportion of the structural unit (a4) when the component (A1) is used in the positive resist composition, and the amount of the acid catalyst used is the crosslinkable polyvinyl ether compound to be used. 0.001-50 mol% is preferable with respect to this.
The crosslinking reaction conditions can be appropriately set, but the reaction temperature is usually preferably in the range of 0 to 100 ° C., and the reaction time is preferably 15 minutes to 10 hours, more preferably 30 minutes or more. .
After completion of the crosslinking reaction, a basic compound such as triethylamine, tributylamine, or pyridine is added to the reaction solution to stop the reaction, and then this solution is mixed with a good solvent such as tetrahydrofuran or 1,4-dioxane. After diluting to a viscosity, it is poured into a large amount of poor solvent such as methanol or water and precipitated. Then, the (A1) component of this invention can be obtained by filtering the deposit and fully drying.
After the synthesis of the precursor polymer and / or after the cross-linking reaction, the degree of dispersion may be adjusted by performing a known purification step, if necessary.

When the component (A1) is synthesized by the [Method 1], in the component (A1) after polymerization, the structural unit (a1) is preferably 20 to 70 mol%, more preferably 30 to 60 mol%. is there. By setting it to the lower limit value or more, a good fine pattern can be obtained, and by setting the upper limit value or less, it is possible to balance with other structural units.
The structural unit (a2) is contained in an amount of 20 to 60 mol%, preferably 20 to 50 mol%. By setting the lower limit value or more, a good fine pattern can be obtained, and by setting the upper limit value or less, it is possible to balance with other structural units.
The structural unit (a3) is contained in an amount of 0 to 40 mol%, preferably 0.15 to 6 mol%. By setting it to the upper limit value or less, a good fine pattern can be obtained when used in a positive resist composition.
It is preferable that a structural unit (a4) is 5-40 mol%, More preferably, it is 10-30 mol%. By setting the lower limit value or more, it is possible to introduce a preferred proportion of the (a4) structural unit as a resist. By setting the upper limit value or less, an excessive crosslinking reaction such as gelation can be prevented and a positive resist composition can be obtained. When used, a good fine pattern can be obtained.

  When the component (A1) is synthesized by the [Method 2], in the precursor polymer before being crosslinked, the constituent unit (a1) is 20 to 70 with respect to the total of all constituent units constituting the precursor polymer. It is preferable that it is mol%, More preferably, it is 30-60 mol%. By setting it to the lower limit value or more, a good fine pattern can be obtained, and by setting the upper limit value or less, it is possible to balance with other structural units.

  The structural unit (a2) is preferably contained in an amount of 20 to 60 mol%, preferably 20 to 50 mol%, based on the total of all the structural units constituting the precursor polymer. By setting the lower limit value or more, a good fine pattern can be obtained, and by setting the upper limit value or less, it is possible to balance with other structural units.

The proportion of the precursor unit of the structural unit (a4) in the precursor polymer is preferably 5 to 40 mol%, more preferably 10 to 30 mol%. By setting the lower limit value or more, it is possible to introduce a preferred proportion of the (a4) structural unit as a resist. By setting the upper limit value or less, an excessive crosslinking reaction such as gelation can be prevented and a positive resist composition can be obtained. When used, a good fine pattern can be obtained.
In the crosslinking reaction, 0 to 98 mol%, more preferably 3 to 15 mol% of the precursor units in the precursor polymer are not crosslinked, and the structural unit (a3) is contained in the component (A1) after crosslinking. ) Is preferably present. That is, the structural unit (a3) is contained in the component (A1) in an amount of 0 to 40 mol%, preferably 0.15 to 6 mol%. By setting it to the upper limit value or less, a good fine pattern can be obtained when used in a positive resist composition.

..Other structural units The copolymer (A1) may contain other structural units in addition to the structural units (a1), (a2), (a3), and (a4). Good.
Examples of other structural units include structural units (a5) other than the structural units (a1) to (a4).

..Structural unit (a5)
The structural unit (a5) is not particularly limited as long as it is another structural unit that is not classified into the structural units (a1) to (a4). That is, any acid dissociable, dissolution inhibiting group, lactone-containing monocyclic or polycyclic group, polycyclic alicyclic hydrocarbon group containing a hydroxyl group or a carboxyl group, and any one that does not contain the crosslinking group may be used. For example, a structural unit containing a polycyclic alicyclic hydrocarbon group and derived from a (meth) acrylic acid ester is preferable. When such a structural unit is used, when used for a positive resist composition, a solution from an isolated pattern to a semi-dense pattern (a line and space pattern having a space width of 1.2 to 2 with respect to a line width of 1) is obtained. It is excellent in image properties and is preferable.

Examples of such polycyclic alicyclic hydrocarbon groups include those exemplified in the structural units (a1) and (a3), and are conventionally known as ArF positive resist materials. It can be used by appropriately selecting from a large number.
In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, and a tetracyclododecanyl group is preferable in terms of industrial availability.

  Examples of these structural units (a5) include compounds represented by the following general formulas (V) to (VII).

（式中Ｒは水素原子、又は直鎖又は分岐状の低級アルキル基である。）

(In the formula, R is a hydrogen atom or a linear or branched lower alkyl group.)

（式中Ｒは水素原子、又は直鎖又は分岐状の低級アルキル基である。）

(In the formula, R is a hydrogen atom or a linear or branched lower alkyl group.)

（式中Ｒは水素原子、又は直鎖又は分岐状の低級アルキル基である。）

(In the formula, R is a hydrogen atom or a linear or branched lower alkyl group.)

The lower alkyl group (α-lower alkyl group) as R is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, or an n-butyl group. , Isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.
The structural unit (a5) is not an essential component of the component (A1). However, when the structural unit (a5) is contained in the component (A1), the structural unit (a5) is added to the total of all structural units of the component (A1). The content of 1 to 30 mol%, preferably 10 to 20 mol%, is preferable because a good improvement effect can be obtained in the resolution of the semi-dense pattern from the isolated pattern.

1000-20000 are preferable, as for the mass mean molecular weight Mw of the precursor polymer before bridge | crosslinking of a copolymer (A1) component, More preferably, it is 1000-10000, More preferably, it is 2000-7000. By setting the mass average molecular weight below the upper limit and above the lower limit of the above range, a good fine pattern can be obtained when the (A1) component after crosslinking is used in a positive resist composition.
Further, the dispersity in the precursor polymer, that is, the ratio (Mw / Mn) of the mass average molecular weight (Mw) to the number average molecular weight (Mn) is preferably in the range of 1.2 to 3.0, and preferably 1.4 to 2.5. Furthermore, the range of 1.4 to 2.0 is preferable. By setting the dispersity below the upper limit and above the lower limit of the above range, a good fine pattern can be obtained when the (A1) component after crosslinking is used in a positive resist composition.

Moreover, 2000-30000 are preferable, as for the mass mean molecular weight Mw of the copolymer (A1) after bridge | crosslinking, More preferably, it is 5000-20000, More preferably, it is 7000-18000. By setting the mass average molecular weight below the upper limit and above the lower limit of the above range, a good fine pattern can be obtained when the component (A1) is used in a positive resist composition.
The degree of dispersion (Mw / Mn) in the component (A1) after crosslinking is preferably in the range of 1.5 to 4.0, more preferably in the range of 1.7 to 3.5, and even more preferably in the range of 1.9 to 3.0. preferable. By making the degree of dispersion not more than the upper limit of the above range, a good fine pattern can be obtained when the component (A1) is used in a positive resist composition.

  The resin component (A) may contain an appropriate resin other than the component (A1) as long as the effects of the present invention are not impaired, but 100% by mass of the component (A) is the component (A1). It is preferable.

Acid generator component (B) (hereinafter sometimes referred to as component (B))
The component (B) can be used without particular limitation from known acid generators used in conventional chemically amplified resist compositions.
Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, poly (bissulfonyl) diazomethanes, There are various known diazomethane acid generators such as diazomethane nitrobenzyl sulfonates, imino sulfonate acid generators and disulfone acid generators.

  Specific examples of the onium salt-based acid generator include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, and triphenylsulfonium trifluoromethane. Sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, tri (4-methylphenyl) sulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, dimethyl (4-hydroxynaphthyl) sulfonium trifluoromethane Sulfonate, its heptafluoropropane sulphonate or its Nafluorobutane sulfonate, trifluoromethane sulfonate of monophenyldimethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, trifluoromethane sulfonate of diphenyl monomethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, (4- Trifluoromethanesulfonate of methylphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, trifluoromethanesulfonate of (4-methoxyphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, tri (4 -Tert-bu Le) trifluoromethanesulfonate triphenylsulfonium, its like heptafluoropropane sulfonate or nonafluorobutane sulfonates.

  Specific examples of oxime sulfonate acid generators 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-dichlorobenzylcyanide, α- (benzenesulfonyloxyimino) -2,6-dichlorobenzylcyanide, α- (benzenesulfonyloxyimino) -4-methoxybenzylcyanide, 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 Pentenylacetonitrile, 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 Nthenyl 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. Of these, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile is preferred.

Among diazomethane acid generators, specific examples of bisalkyl or bisarylsulfonyldiazomethanes include bis (isopropylsulfonyl) diazomethane, bis (p-toluenesulfonyl) diazomethane, bis (1,1-dimethylethylsulfonyl) diazomethane, Examples include bis (cyclohexylsulfonyl) diazomethane, bis (2,4-dimethylphenylsulfonyl) diazomethane, and the like.
Examples of poly (bissulfonyl) diazomethanes include 1,3-bis (phenylsulfonyldiazomethylsulfonyl) propane (Compound A, decomposition point 135 ° C.), 1,4-bis (phenyl) having the following structure. Sulfonyldiazomethylsulfonyl) butane (compound B, decomposition point 147 ° C.), 1,6-bis (phenylsulfonyldiazomethylsulfonyl) hexane (compound C, melting point 132 ° C., decomposition point 145 ° C.), 1,10-bis (phenyl) Sulfonyldiazomethylsulfonyl) decane (compound D, decomposition point 147 ° C.), 1,2-bis (cyclohexylsulfonyldiazomethylsulfonyl) ethane (compound E, decomposition point 149 ° C.), 1,3-bis (cyclohexylsulfonyldiazomethylsulfonyl) ) Propane (Compound F, decomposition point 153 ° C.), , 6-bis (cyclohexylsulfonyldiazomethylsulfonyl) hexane (Compound G, melting point 109 ° C., decomposition point 122 ° C.), 1,10-bis (cyclohexylsulfonyldiazomethylsulfonyl) decane (Compound H, decomposition point 116 ° C.), etc. Can be mentioned.

  In the present invention, it is particularly preferable to use an onium salt having a fluorinated alkyl sulfonate ion as an anion as the component (B).

As the component (B), one type of acid generator may be used alone, or two or more types may be used in combination.
(B) Content of a component is 0.5-30 mass parts with respect to 100 mass parts of (A) component, Preferably it is 1-10 mass parts. If the amount is less than the above range, pattern formation may not be sufficiently performed, and if the amount exceeds the above range, a uniform solution is difficult to obtain, which may cause a decrease in storage stability.

・ Nitrogen-containing organic compounds (D)
In the positive resist composition of the present invention, a nitrogen-containing organic compound (D) (hereinafter referred to as “component (D)”) is further added as an optional component in order to improve the resist pattern shape, stability over time and the like. Can be blended.
Since a wide variety of components (D) have already been proposed, any known one may be used, but amines, particularly secondary lower aliphatic amines and tertiary lower aliphatic amines are preferred. .
Here, the lower aliphatic amine refers to an alkyl or alkyl alcohol amine having 5 or less carbon atoms, and examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, di-n-propylamine, Tri-n-propylamine, tripentylamine, diethanolamine, triethanolamine, triisopropanolamine and the like can be mentioned, and tertiary alkanolamines such as triethanolamine are particularly preferable.
These may be used alone or in combination of two or more.
(D) component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component.

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

Organic solvent The positive resist composition of the present invention can be produced by dissolving materials in an organic solvent.
Any organic solvent may be used as long as it can dissolve each component to be used to form a uniform solution, and one or two kinds of conventionally known solvents for chemically amplified resists can be used. These can be appropriately selected and used.
For example, ketones such as γ-butyrolactone, acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, dipropylene glycol Or dipropylene glycol monoacetate monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and other polyhydric alcohols and derivatives thereof, cyclic ethers such as dioxane, methyl lactate, lactic acid Ethyl (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxy Methyl propionate, esters such as ethyl ethoxypropionate can be exemplified.
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.
A mixed solvent obtained by mixing propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent is preferable. The blending ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. It is preferable to be within the range.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 2: 8 to 8: 2, more preferably 3: 7 to 7: 3.
In addition, as the organic solvent, 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.
Although the amount of the organic solvent used is not particularly limited, it is a concentration that can be applied to a substrate and the like, and is appropriately set according to the coating film thickness. In general, the solid content concentration of the resist composition is 2 to 20 mass. %, Preferably 5-15% by mass.

Other optional components In the positive resist composition of the present invention, there are further miscible additives as desired, for example, additional resins for improving the performance of the resist film, and surfactants for improving the coating properties. Further, a dissolution inhibitor, a plasticizer, a stabilizer, a colorant, an antihalation agent, a dye, and the like can be appropriately added and contained.

-Resist pattern formation method The resist pattern formation method of this invention can be performed as follows, for example.
That is, first, the positive resist composition is applied onto a substrate such as a silicon wafer with a spinner and prebaked for 40 to 120 seconds, preferably 60 to 90 seconds under a temperature condition of 80 to 150 ° C. After selectively exposing ArF excimer laser light through a desired mask pattern using, for example, an ArF exposure apparatus or the like, PEB (post-exposure heating) is performed for 40 to 120 seconds at a temperature of 80 to 150 ° C., preferably Apply for 60-90 seconds. Subsequently, this is developed using an alkaline developer, for example, an aqueous 0.1 to 10% by mass tetramethylammonium hydroxide solution. In this way, a resist pattern faithful to the mask pattern can be obtained.
An organic or inorganic antireflection film can be provided between the substrate and the coating layer of the resist composition.

The wavelength used for 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. In particular, the photoresist composition according to the present invention is effective for an ArF excimer laser.

The (A) component in the present invention has an acid dissociable, dissolution inhibiting group, and the acid dissociable, dissolution inhibiting group is dissociated by the action of an acid generated from the (B) component, thereby increasing alkali solubility.
More specifically, when the acid generated from the component (B) by exposure acts on the component (A), the acid dissociable, dissolution inhibiting group in the component (A) is dissociated, whereby the entire positive resist is alkali-insoluble to alkaline. It becomes soluble. Therefore, when a positive resist is exposed through a mask pattern in the formation of a resist pattern, or when PEB is performed in addition to exposure, the exposed portion turns alkali-soluble while the unexposed portion remains alkali-insoluble. Therefore, a positive resist pattern can be formed by alkali development.

In particular, according to the present invention, it is possible to form a resist pattern with high resolution and low LER. This is because the (A1) component has the crosslinked structural unit (a4), so that the solubility of the (A1) component itself in an alkaline developer is lowered, and the structural unit (a4) has a crosslinked site. Since the acid-dissociable group is formed, the cross-linked site is cleaved at the exposed portion, and as a result, the high solubility in an alkali developer is considered to contribute greatly. Thus, it is considered that the solubility greatly changes between the exposed area and the unexposed area, thereby increasing the contrast and improving the limit resolution and reducing the LER.
In particular, when the structural unit (a4) is intermolecularly bonded, the molecular weight of the resin component is greatly reduced due to cleavage at the cross-linked site of the structural unit (a4). It is thought that sex changes greatly.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples.

(Synthesis Example 1)
A copolymer (A1-1) represented by the following general formula was synthesized.

(1) Synthesis of Precursor Polymer Into a four-necked flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer, 2500 g of tetrahydrofuran, 320 g of 2-methyl-2-adamantyl methacrylate, 230 g of γ-butyrolactone methacrylate and 3- After putting 160 g of hydroxy-1-adamantyl methacrylate and replacing with nitrogen, the temperature was raised to 70 ° C. with stirring. While maintaining the temperature, a polymerization initiator solution in which 80 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved in 120 g of tetrahydrofuran was dropped over 15 minutes. After completion of the dropwise addition, stirring was continued for 5 hours while maintaining the temperature, and then the mixture was cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol / water mixed solution to obtain a precipitate. The precipitate was filtered, washed and dried to obtain a white solid random copolymer (precursor polymer).
(2) Identification of the white solid obtained in (1) and mass average molecular weight determined in terms of polystyrene by gel permeation chromatography (GPC); 5,600, dispersity 1.9
Monomer composition ratio by isotope carbon nuclear magnetic resonance ( ¹³ C-NMR) analysis; 2-methyl-2-adamantyl methacrylate / γ-butyrolactone methacrylate / 3-hydroxy-1-adamantyl methacrylate = 39/41/20 mol %

(3) Crosslinking 140 g of the obtained white solid, 700 g of tetrahydrofuran, and 20 mg of p-toluenesulfonic acid monohydrate were placed in a four-necked flask equipped with a nitrogen blowing tube, a refluxer, a dropping funnel and a thermometer, and stirred. The temperature was raised to 50 ° C. While maintaining the temperature, a solution prepared by dissolving 6 g of 1,4-butanediol divinyl ether in 1 g of tetrahydrofuran was dropped. After completion of dropping, the mixture was stirred for 3 hours while maintaining the temperature, and then cooled to 25 ° C. Thereafter, triethylamine was added to stop the reaction.
The obtained reaction solution was dropped into a large amount of water to obtain a precipitate. The precipitate was filtered, washed and dried to obtain a white solid random copolymer (copolymer (A1-1)).
(4) Identification of the white solid obtained in (3) / Mass average molecular weight determined in terms of polystyrene by gel permeation chromatography (GPC); 10,700, dispersity 2.9
-Crosslinking rate of hydroxyl group of 3-hydroxy-1-adamantyl methacrylate site determined by isotope hydrogen nuclear magnetic resonance ( ¹ H-NMR) analysis: 4%

(Synthesis Example 2)
A copolymer (A1-2) represented by the following general formula was synthesized.

(1) Synthesis of Precursor Polymer A 4-necked flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer was attached with 520 g of methyl ethyl ketone, 20 g of 1-cyclohexyl methacrylate, 20 g of γ-butyrolactone methacrylate and 3-hydroxy-1-adamantyl. After adding 60 g of methacrylate and replacing with nitrogen, the temperature was raised to 85 ° C. with stirring. While maintaining the temperature, 250 g of 1-cyclohexyl methacrylate, 210 g of γ-butyrolactone methacrylate, 150 g of 3-hydroxy-1-adamantyl methacrylate and 80 g of dimethyl-2,2′-azobisisobutyrate were dissolved in 1250 g of methyl ethyl ketone. The solution was added dropwise over 3 hours. After completion of the dropwise addition, the mixture was stirred for 3 hours while maintaining the temperature, and then cooled to 25 ° C. to complete the polymerization.
Thereafter, the obtained polymerization solution was dropped into a large amount of methanol to obtain a precipitate. The precipitate was filtered, washed and dried to obtain a white solid random copolymer (precursor polymer).
(2) Identification of the white solid obtained in (1) and mass average molecular weight determined in terms of polystyrene by gel permeation chromatography (GPC): 5,000, dispersity 1.7
Monomer composition ratio by isotope carbon nuclear magnetic resonance ( ¹³ C-NMR) analysis: 1-cyclohexyl methacrylate / γ-butyrolactone methacrylate / 3-hydroxy-1-adamantyl methacrylate = 35/43/22 mol%

(3) Crosslinking A white solid 130 g, tetrahydrofuran 650 g, and p-toluenesulfonic acid monohydrate 20 mg were put into a 4-neck flask equipped with a nitrogen blowing tube, a reflux condenser, a dropping funnel and a thermometer, and stirred. The temperature was raised to 50 ° C. While maintaining the temperature, a solution prepared by dissolving 8 g of 1,4-butanediol divinyl ether in 1 g of tetrahydrofuran was dropped. After completion of dropping, the mixture was stirred for 3 hours while maintaining the temperature, and then cooled to 25 ° C. Thereafter, triethylamine was added to stop the reaction.
The obtained reaction solution was dropped into a large amount of water to obtain a precipitate. This precipitate was filtered, washed and dried to obtain a white solid random copolymer (copolymer (A1-2)).
(4) Identification of the white solid obtained in (3) and mass average molecular weight determined in terms of polystyrene by gel permeation chromatography (GPC); 9,400, dispersity 2.6
-Crosslinking rate of hydroxyl group of 3-hydroxy-1-adamantyl methacrylate site determined by isotope hydrogen nuclear magnetic resonance ( ¹ H-NMR) analysis: 4%

Example 1
Using the copolymer (A1-1) obtained in Synthesis Example 1 (3), a positive resist composition was prepared with the following composition.
(A) 100 parts by mass of copolymer (A1-1) as component,
(B) 4-methylphenyldiphenylsulfonium nonafluorobutanesulfonate 3.0 parts by mass as component (D) 0.35 parts by mass of triethanolamine as component (A) to (D) are changed to PGMEA: EL = 6: 4 A positive resist composition having a solid content concentration of 10% by mass was prepared by dissolving in an organic solvent.

(Comparative Example 1)
In Example 1, instead of the copolymer (A1-1), a positive type was obtained in the same manner as in Example 1 except that 100 parts by mass of the precursor polymer obtained in (1) of Synthesis Example 1 was used. A resist composition was prepared.

(Comparative Example 2)
In Synthesis Example 1 (1), by changing the synthesis conditions, mass average molecular weight: 10,000, degree of dispersion 1.9, monomer composition ratio; 2-methyl-2-adamantyl methacrylate / γ-butyrolactone methacrylate A copolymer having no crosslinkable group was synthesized in which / 3-hydroxy-1-adamantyl methacrylate = 39/41/20 mol%.
A positive resist composition was prepared in the same manner as in Example 1 except that the obtained copolymer was used in place of the copolymer (A1-1).

(Evaluation methods)
A resist pattern was formed using the positive resist compositions obtained in Example 1 and Comparative Examples 1 and 2.
First, an organic antireflection film composition “ARC-29A” (trade name, manufactured by Brewer Science Co., Ltd.) was applied on an 8-inch silicon wafer using a spinner, and baked on a hot plate at 205 ° C. for 60 seconds. By drying, an organic antireflection film having a thickness of 77 nm was formed.
Next, the positive resist composition was applied on the antireflection film using a spinner, pre-baked (PAB) at 120 ° C. for 90 seconds on a hot plate, and dried to form a resist layer having a thickness of 300 nm. .
Next, an ArF excimer laser (193 nm) is selectively passed through a mask pattern (halftone) using an ArF exposure apparatus NSR-S302 (manufactured by Nikon Corporation; NA (numerical aperture) = 0.60, 2/3 ring zone). Irradiated.
Then, PEB treatment is performed at 120 ° C. for 90 seconds, and further paddle development is performed with a 2.38 mass% tetramethylammonium hydroxide aqueous solution at 23 ° C. for 60 seconds, followed by washing with water for 20 seconds and drying to form a resist pattern. did.
In Comparative Example 2, the pre-bake temperature was changed to 130 ° C., and the PEB temperature was changed to 130 ° C.
In this way, a 1: 1 130 nm line and space pattern was formed.

The following items were evaluated for the resist pattern formed above.
<Sensitivity>
The exposure time at which a 130 nm line and space was formed at 1: 1 was measured as sensitivity (EOP) in mJ / cm ² (energy amount).
<LER>
For a 1: 1 line and space pattern with a line width of 130 nm, 3σ, which is a measure indicating LER, was determined. A side length SEM (trade name “S-9220” manufactured by Hitachi, Ltd.) was used to measure the width of the resist pattern of the sample at 32 locations, which is three times the standard deviation (σ) calculated from the result (3σ). . This 3σ means that the smaller the value, the smaller the roughness and the uniform width resist pattern was obtained.

From the above results, it was found that Example 1 had high resolution and reduced LER.

Claims (11)

A resist composition containing a resin component (A) whose alkali solubility is changed by the action of an acid, and an acid generator component (B) that generates an acid upon exposure,
The resin component (A) has a structural unit (a1) derived from a mono (α-lower alkyl) acrylate ester containing an acid dissociable, dissolution inhibiting group, a mono (-) containing a lactone-containing monocyclic or polycyclic group ( derived from (α-lower alkyl) acrylic acid ester having structural unit (a2) derived from (α-lower alkyl) acrylic acid ester and polycyclic alicyclic hydrocarbon group containing hydroxyl group or carboxyl group The hydrogen atom of the hydroxyl group or carboxyl group of the precursor unit is represented by the following general formula (I)

(In the formula, A is a divalent or trivalent organic group, and p is an integer of ¹ to ^3. R ¹ and R ² are each independently a hydrogen atom or a linear or branched lower alkyl group. .)
A copolymer (A1) having a structural unit (a4) derived from a poly (α-lower alkyl) acrylate ester that is substituted with a crosslinking group represented by A positive resist composition characterized by the above.   The copolymer (A1) further has a structural unit (a3) derived from a mono (α-lower alkyl) acrylate ester having a polycyclic alicyclic hydrocarbon group containing a hydroxyl group or a carboxyl group. The positive resist composition according to claim 1. The structural unit (a4) is represented by the following general formula (II)

(In the formula, R ^{3 to} R ⁸ are each independently a hydrogen atom or a linear or branched lower alkyl group. A is a linear or branched alkylene group having 1 to 8 carbon atoms, or carbon. X and Y are each independently an alicyclic group having 4 to 12 carbon atoms, and has a linear or branched lower alkyl group as a substituent. May be.)
The positive resist composition according to claim 1, wherein the positive resist composition is represented by:   4. One or both of X and Y are groups obtained by removing two hydrogen atoms from adamantane, which may have a linear or branched lower alkyl group as a substituent. A positive resist composition. The structural unit (a1) is represented by the following general formula (aI)

(In the formula, R ⁹ is a hydrogen atom or a linear or branched lower alkyl group, and R ¹⁰ is a linear or branched lower alkyl group.)
The positive resist composition according to claim 1, wherein the positive resist composition is a structural unit represented by: The structural unit (a2) is represented by the following general formula (aII)

(In the formula, R ¹¹ , R ¹² and R ¹³ are each independently a hydrogen atom or a linear or branched lower alkyl group.)
The positive resist composition according to claim 1, wherein the positive resist composition is a structural unit represented by: The structural unit (a3) is represented by the following general formula (aIII)

(In the formula, R ¹⁴ is a hydrogen atom or a linear or branched lower alkyl group. N is an integer of 1 to 3.)
The positive resist composition according to claim 1, wherein the positive resist composition is a structural unit represented by: The structural unit (a4) is represented by the following general formula (aIV)

(In the formula, R ³ and R ⁴ are each independently a hydrogen atom or a linear or branched lower alkyl group. A is a linear or branched alkylene group having 1 to 8 carbon atoms or a carbon number. 4 to 10 alicyclic groups, R ¹⁵ and R ¹⁶ are each independently a linear or branched lower alkyl group.)
The positive resist composition according to claim 1, wherein the positive resist composition is a structural unit represented by: The structural unit (a4) is represented by the following general formula (aV)

(In the formula, R ³ and R ⁴ are each independently a hydrogen atom or a linear or branched lower alkyl group. R ¹⁵ and R ¹⁶ are each independently a linear or branched lower alkyl group. Group.)
The positive resist composition according to claim 8, which is represented by:   Furthermore, a nitrogen-containing organic compound is contained, The positive resist composition of any one of Claims 1-9 characterized by the above-mentioned. After apply | coating the positive resist composition as described in any one of Claims 1-10 on a board | substrate, prebaking and selectively exposing, PEB (post-exposure heating) is given and alkali image development is carried out. And forming a resist pattern.