JP4437065B2 - Positive resist composition and resist pattern forming method - Google Patents

Description

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

In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, pattern miniaturization has been rapidly progressing due to advances in lithography technology.
As a technique for miniaturization, the wavelength of an exposure light source is generally shortened. Specifically, conventionally, ultraviolet rays typified by g-line and i-line have been used, but now mass production of semiconductor elements using a KrF excimer laser or an ArF excimer laser has started. Further, studies have been made on F ₂ excimer lasers, EUV (extreme ultraviolet rays), electron beams, X-rays, and the like having shorter wavelengths than these excimer lasers.

In addition, as one of the resist materials that satisfy the high resolution conditions that can reproduce patterns with fine dimensions, it contains a base resin whose alkali solubility changes due to the action of acid and an acid generator that generates acid upon exposure. A chemically amplified resist composition is known. The chemically amplified resist composition includes a negative type containing an alkali-soluble resin, an acid generator and a crosslinking agent, and a positive type containing a resin whose acid solubility is increased by the action of an acid and an acid generator.
Currently, as a resist base resin used in ArF excimer laser lithography and the like, a resin (acrylic resin) having a structural unit derived from (meth) acrylic acid is mainstream because of its excellent transparency near 193 nm. It has become.
In general, a polycyclic aliphatic ring such as an adamantyl group is introduced into the base resin as a substituent of the ester portion of the (meth) acrylic acid ester in order to improve etching resistance. For example, as a base resin used in the case of a positive type, a resin having a structural unit derived from a (meth) acrylic acid ester having an acid dissociable, dissolution inhibiting group such as a 2-methyl-2-adamantyl group in the ester portion. It is used.
In addition, in order to reduce hydrophobicity, a structural unit derived from a (meth) acrylate ester having a lactone skeleton such as a γ-butyrolactone skeleton in the ester portion is introduced into the resin, or solubility in a developer In order to improve the structure, a polycyclic group containing a polar group such as a cyano group, for example, a structural unit derived from a (meth) acrylic acid ester having a cyanonorbornyl group in the ester portion is introduced. (For example, refer to Patent Document 1).
International Publication No. 04/067592 Pamphlet

However, the resist pattern formed using the resist as described above has a problem in shape. For example, a footing that remains without removing the resist at the boundary with the substrate is generated, or the line width of the line pattern is increased. There is a problem that line width roughness (hereinafter referred to as LWR) is generated. Moreover, further improvement is required for etching resistance.
This invention is made | formed in view of the said situation, Comprising: It aims at providing the positive resist composition and resist pattern formation method which can form the resist pattern excellent in the shape and the etching tolerance.

As a result of intensive studies, the present inventors have found that the above problem can be solved by using a resin having three types of structural units having a specific structure as the base resin, and completed the present invention. .
That is, the first aspect of the present invention is a positive resist composition comprising a resin component (A) whose alkali solubility is increased by the action of an acid and an acid generator component (B) which generates an acid upon exposure. And
The resin component (A) is represented by the following general formula (a0-1)

[式中、Ｒは水素原子または低級アルキル基である。]
で表される構成単位（ａ０）と、下記一般式（ａ１−１１）または（ａ１−１２）

[Wherein, R represents a hydrogen atom or a lower alkyl group. ]
A structural unit (a0) represented by the following general formula (a1-11) or (a1-12)

［式中、Ｒは水素原子または低級アルキル基であり、Ｒ^１〜Ｒ^２はそれぞれ独立して炭素数１〜４のアルキル基であり、ｔは１〜３の整数である。］
で表される構成単位からなる群から選択される少なくとも１種の構成単位（ａ１）と、下記一般式（ａ２−１）

[Wherein, R is a hydrogen atom or a lower alkyl group, R ^{1 to} R ² are each independently an alkyl group having 1 to 4 carbon atoms, and t is an integer of 1 to 3. ]
At least one structural unit (a1) selected from the group consisting of structural units represented by the following general formula (a2-1):

［式中、Ｒは水素原子または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る。］
で表される構成単位（ａ２）を有するポジ型レジスト組成物である。

[Wherein, R represents a hydrogen atom or a lower alkyl group, and R ′ represents a hydrogen atom, a lower alkyl group, or an alkoxy group having 1 to 5 carbon atoms. ]
A positive resist composition having a structural unit (a2) represented by:

  The second aspect of the present invention includes a step of forming a resist film on a substrate using the positive resist composition of the first aspect, a step of exposing the resist film, and developing the resist film. And a step of forming a resist pattern.

  In the claims and the specification, the “constituent unit” means a monomer unit constituting the polymer. In addition, “exposure” is a concept including general radiation irradiation.

  ADVANTAGE OF THE INVENTION By this invention, the positive resist composition and resist pattern formation method which can form the resist pattern excellent in the shape and the etching tolerance can be provided.

≪Positive resist composition≫
The positive resist composition of the present invention comprises a resin component (A) whose alkali solubility is increased by the action of an acid (hereinafter referred to as “component (A)”) and an acid generator component (B) which generates an acid upon exposure (hereinafter referred to as “acid generator component”). , (B) component) and a positive resist composition.
In such a positive resist composition, when acid is generated from the component (B) by exposure, the acid increases alkali solubility of the component (A). Therefore, in the formation of the resist pattern, when the resist composition applied on the substrate is selectively exposed, the alkali solubility of the exposed portion increases and alkali development can be performed.

<(A) component>
In the present invention, the component (A) is composed of the structural unit (a0) represented by the general formula (a0-1) and the structural unit represented by the general formula (a1-11) or (a1-12). It is necessary to have at least one structural unit (a1) selected from the group consisting of and a structural unit (a2) represented by the above general formula (a2-1).

・ Structural unit (a0)
In formula (a0-1), R represents a hydrogen atom or a lower alkyl group.
The lower alkyl group of R is an alkyl group having 1 to 5 carbon atoms, specifically, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group. And a lower linear or branched alkyl group such as a group, an isopentyl group and a neopentyl group.
R is preferably a hydrogen atom or a methyl group in terms of industrial availability.
Note that the hydrogen atom of R or the hydrogen atom of the lower alkyl group may be substituted with a fluorine atom.
In the structural unit (a0), the cyano group (—CN) is preferably bonded to the 9-position or the 10-position of the 2-tetracyclododecanyl group.

In the component (A), as the structural unit (a0), one type may be used alone, or two or more types may be used in combination.
In the component (A), the proportion of the structural unit (a0) is preferably 10 to 60 mol%, more preferably 10 to 40 mol%, more preferably 10 to 30 mol based on the total of all the structural units constituting the component (A). More preferred is mol%. By setting it to the lower limit value or more, the effect of the present invention becomes sufficient, and by setting it to the upper limit value or less, it is possible to balance with other structural units. Moreover, pattern collapse can be suppressed.

・ Structural unit (a1)
In the structural unit (a1), when an acid generated from the component (B) acts upon exposure, an oxygen atom bonded to the carbonyl group (—CO—) in the side chain portion and a tertiary carbon bonded to the oxygen atom The bond between the atoms is broken, and a cyclic group containing the tertiary carbon atom, that is, a group represented by the following formula (I) or (II) is dissociated. These groups are so-called acid-dissociable, dissolution-inhibiting groups that have an alkali dissolution inhibiting property that makes the entire component (A) insoluble in alkali before dissociation and change the entire component (A) to alkali-soluble after dissociation. .

In formulas (a1-11) and (a1-12), R is the same as described above.
R ^{1 and} R ² are each independently an alkyl group having 1 to 4 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group. And a linear or branched alkyl group such as a methyl group or an ethyl group is preferred industrially. In particular, it is preferable that R ^{1 to} R ² are an alkyl group having 2 or more carbon atoms because mask linearity is further improved. In view of these, R ¹ is most preferably a methyl group or an ethyl group, and R ² is most preferably an ethyl group.
t is an integer of 1 to 3, preferably 1 or 2, and most preferably 2.

  Specific examples of the structural unit (a1-11) include structural units represented by the following chemical formulas (a1-11-1) to (a1-11-4).

  Specific examples of the structural unit (a1-12) include structural units represented by the following chemical formulas (a1-12-1) to (a1-12-10).

  Among these, the structural units represented by (a1-11-1) to (a1-11-4), (a1-12-9), and (a1-12-10) are excellent in the effects of the present invention. preferable.

In the component (A), as the structural unit (a1), one type may be used alone, or two or more types may be used in combination.
In the component (A), the proportion of the structural unit (a1) is preferably 10 to 80 mol%, more preferably 20 to 60 mol%, more preferably 30 to 50, 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, a pattern can be obtained when the resist composition is used, and by setting it to the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a2)
In formula (a2-1), R is the same as described above.
R ′ is a hydrogen atom, a lower alkyl group, or an alkoxy group having 1 to 5 carbon atoms.
Examples of the lower alkyl group for R ′ include the same as the lower alkyl group for R.
The alkoxy group having 1 to 5 carbon atoms of R ′ is represented by the general formula —OR ″ [R ″ is an alkyl group having 1 to 5 carbon atoms], and R ′ is an alkyl group having 1 to 5 carbon atoms. Are the same as the lower alkyl group of R, and among them, a methyl group or an ethyl group is preferable.
R ′ is preferably a hydrogen atom in view of industrial availability.

In the present invention, since the component (A) has the structural unit (a2), the adhesion of the resist film to the substrate is improved, and the hydrophilicity with the developer is also increased, thereby improving the resist pattern shape. . Moreover, since it is a structure having a ring, it contributes to improvement of etching resistance.
In general, when the component (A) contains the structural unit (a2) represented by the general formula (a2-1), the tip of the resist pattern becomes round and the rectangularity tends to deteriorate. In (1), a rectangular resist pattern can be obtained even when the component (A) containing the structural unit (a2) is used.

  More specifically, examples of the structural unit (a2) include structural units represented by the following chemical formulas (a2-1-1) to (a2-1-6).

  Among these, the structural unit represented by the chemical formula (a2-1-1) or (a2-1-2) is excellent in the effect of the present invention and is preferable.

In the component (A), as the structural unit (a2), one type may be used alone, or two or more types may be used in combination.
The proportion of the structural unit (a2) in the component (A) is preferably 10 to 80 mol%, more preferably 20 to 60 mol%, with respect to the total of all the structural units constituting the component (A), 30 to 50 mol% is more preferable. By setting it to the lower limit value or more, the effect of the present invention becomes sufficient, and by setting it to the upper limit value or less, it is possible to balance with other structural units.

  In the present invention, the component (A) is preferably a copolymer having all of these structural units (a0) to (a2) because of excellent effects of the present invention, and particularly the structural units (a0) to ( A copolymer comprising a2) is preferred.

-Other structural units In addition to the structural units (a0), (a1) and (a2), the polymer compound (A1) is further composed of structural units (a0), (a You may have the other structural unit which is not classified into a1) and (a2). Examples of the structural unit include the following structural units (a1 ′), (a2 ′), (a3), and (a4).
Structural unit (a1 ′): a structural unit derived from an (α-lower alkyl) acrylate ester having an acid dissociable, dissolution inhibiting group, not classified into the structural unit (a1).
Structural unit (a2 ′): a structural unit derived from an (α-lower alkyl) acrylate ester having a lactone-containing monocyclic or polycyclic group, which is not classified into the structural unit (a2).
Structural unit (a3): a structural unit derived from an (α-lower alkyl) acrylate ester containing a polar group-containing aliphatic hydrocarbon group, which is not classified into the structural unit (a0).
Structural unit (a4): a structural unit not classified as any of the structural units described above.

In the present invention, “(α-lower alkyl) acrylate ester” means one or both of an acrylate ester and an α-lower alkyl acrylate ester such as a methacrylate ester. “(Meth) acrylic acid ester” means one or both of acrylic acid ester and methacrylic acid ester.
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.
The lower alkyl group as the substituent at the α-position of “(α-lower alkyl) acrylic acid ester” is the same as the lower alkyl group for R in the structural units (a0) to (a2).

The structural unit (a1 ′) is a structural unit derived from an (α-lower alkyl) acrylate ester having an acid dissociable, dissolution inhibiting group (excluding the structural unit (a1) above).
The structural unit (a1 ′) is not particularly limited as long as it is not classified as the structural unit (a1). Until now, it has been proposed as a structural unit having an acid dissociable, dissolution inhibiting group in a base resin for a chemically amplified resist. Can be used.
The acid dissociable, dissolution inhibiting group in such a structural unit is generally a group that forms a cyclic or chain tertiary alkyl ester with a carboxy group of (meth) acrylic acid, or a cyclic or chain alkoxy group. Groups that form alkyl esters are widely known. “(Meth) acrylic acid ester” means one or both of acrylic acid ester and methacrylic acid ester.

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

  The structural unit (a1 ′) is 1 selected from the group consisting of a structural unit represented by the following general formula (a1-0-1) and a structural unit represented by the following general formula (a1-0-2). It is preferable to use more than one species.

（式中、Ｒは水素原子または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。ただし、Ｘ^１としては、上記式（Ｉ）または（ＩＩ）で表される基を除く。）

(In the formula, R represents a hydrogen atom or a lower alkyl group; X ¹ represents an acid dissociable, dissolution inhibiting group. However, X ¹ excludes the group represented by the above formula (I) or (II). .)

（式中、Ｒは水素原子または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は脂肪族環式基を示す。）

(In the formula, R represents a hydrogen atom or a lower alkyl group; X ² represents an acid dissociable, dissolution inhibiting group; Y ² represents an aliphatic cyclic group.)

In general formula (a1-0-1), R is the same as described above.
X ¹ is not particularly limited as long as it is an acid dissociable, dissolution inhibiting group, and examples thereof include an alkoxyalkyl group, a tertiary alkyl ester type acid dissociable, dissolution inhibiting group, and the like. Acid dissociable, dissolution inhibiting groups are preferred. 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.

The term “aliphatic” in the present specification and claims is a relative concept with respect to aromatics, and is defined to mean groups, compounds, etc. that do not have aromaticity.
The “aliphatic cyclic group” means a monocyclic group or a polycyclic group having no aromaticity.
At this time, the “aliphatic cyclic group” may or may not have a substituent. Examples of the substituent include a lower alkyl group having 1 to 5 carbon atoms, a fluorine atom, a fluorinated lower alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, an oxygen atom (= O), and the like.
The basic ring structure excluding the substituent of the “aliphatic cyclic group” is not limited to a group consisting of carbon and hydrogen (hydrocarbon group), but is preferably a hydrocarbon group. The “hydrocarbon group” may be either saturated or unsaturated, but is usually preferably saturated. A polycyclic group is preferred.
Specific examples of such aliphatic cyclic groups include, for example, monocycloalkanes, bicycloalkanes, tricycloalkanes, tetraalkyls which may or may not be substituted with a fluorine atom or a fluorinated alkyl group. Examples thereof include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as cycloalkane. 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.

Specific examples of the aliphatic branched acid dissociable, dissolution inhibiting group include a tert-butyl group and a tert-amyl group.
The acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group includes a tertiary carbon atom on the ring skeleton of the same aliphatic cyclic group as the monovalent aliphatic cyclic group shown above. a group having a (where a is ^{X 1,} except a group represented by the formula (I) or (II).). Examples of the structural unit represented by the following general formula include a group having an aliphatic cyclic group such as an adamantyl group and a branched alkylene group having a tertiary carbon atom bonded thereto.

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

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

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

（式中、Ｒ^２１、Ｒ^２２はそれぞれ独立してアルキル基または水素原子であり、Ｒ^２３はアルキル基又はシクロアルキル基である。または、Ｒ^２１とＲ^２３の末端が結合して環を形成していてもよい。）

(In the formula, R ²¹ and R ²² are each independently an alkyl group or a hydrogen atom, and R ²³ is an alkyl group or a cycloalkyl group. Alternatively, the ends of R ²¹ and R ²³ are combined to form a ring. You may do it.)

In R ²¹ and R ²² , the alkyl group preferably has 1 to 15 carbon atoms, may be linear or branched, and is preferably an ethyl group or a methyl group, and most preferably a methyl group. In particular, it is preferable that one of R ²¹ and R ²² is a hydrogen atom and the other is a methyl group.
R ²³ is an alkyl group or a cycloalkyl group, preferably having 1 to 15 carbon atoms, and may be linear, branched or cyclic. When R ²³ 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 ²³ 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 a group excluding a hydrogen atom. Specific examples include monocycloalkanes such as cyclopentane and cyclohexane, and groups obtained by removing one or more hydrogen atoms from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Among them, a group obtained by removing one or more hydrogen atoms from adamantane is preferable.
In the above formula, R ²¹ and R ²³ are each independently an alkylene group having 1 to 5 carbon atoms, and the end of R ^{23 and} the end of R ²¹ may be bonded to each other. In this case, a cyclic group is formed by R ²¹ , R ²³ , the oxygen atom to which R ²³ is bonded, and the carbon atom to which the oxygen atom and R ²¹ are bonded. The cyclic group is preferably a 4-7 membered ring, and more preferably a 4-6 membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

In general formula (a1-0-2), R is the same as defined above.
Examples of X ² include the same as X ¹ described above. However, X ² may contain a group represented by the above formula (I) or (II).
Y ² is a divalent aliphatic cyclic group, and an aliphatic cyclic group similar to the divalent one among the above “aliphatic cyclic groups” can be used.

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

［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または１〜３の整数を表し；ｍは０または１を表し；Ｒは前記と同じであり、Ｒ^１’、Ｒ^２’はそれぞれ独立して水素原子または炭素数１〜５の低級アルキル基を表す。ただし、式（ａ１−１）におけるＸとしては、上記式（Ｉ）または（ＩＩ）で表される基を除く。］

[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. However, X in the formula (a1-1) excludes the group represented by the above formula (I) or (II). ]

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

X ′ is the same as the 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 explanation 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.
The structural unit (a1 ′) is not an essential component of the component (A), but when it is contained in the component (A), the structural unit is based on the total of all the structural units constituting the component (A). (A1 ′) is preferably contained in an amount of 1 to 30 mol%, preferably 5 to 20 mol%.

The structural unit (a2 ′) is a structural unit derived from an (α-lower alkyl) acrylate ester having a lactone-containing monocyclic or polycyclic group that is not classified as the structural unit (a2). The structural unit (a2 ′) is effective in increasing the adhesion of the resist film to the substrate and increasing the hydrophilicity with the developer.
Here, the lactone-containing monocyclic or polycyclic group refers to a cyclic group containing one ring (lactone ring) containing an —O—C (O) — structure. The lactone ring is counted as the first ring. 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.

  The structural unit (a2 ′) is not particularly limited as long as it is not classified as the structural unit (a2), and any structural unit can be used. For example, examples of the lactone-containing polycyclic group include groups in which one or more hydrogen atoms have been removed from a bicycloalkane, tricycloalkane, or tetracycloalkane having a lactone ring. In particular, a group obtained by removing one hydrogen atom from a lactone-containing tricycloalkane having the following structural formula is advantageous in that it is easily available industrially.

  More specifically, examples of the structural unit (a2 ′) include structural units represented by general formulas (a2-2) to (a2-5) shown below.

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

[Wherein, R is a hydrogen atom or a 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. ]

In general formulas (a2-2) to (a2-5), the lower alkyl group for R and R ′ is the same as the lower alkyl group for R and R ′ in the structural unit (a2).
Specific examples of the structural units represented by the general formulas (a2-2) to (a2-5) are shown below.

  Among these, the structural unit represented by the general formula (a2-2) or (a2-3) is preferable, and specifically, the chemical formulas (a2-2-1), (a2-2-2), (a2 -3-1), the structural unit represented by (a2-3-2), (a2-3-9) or (a2-3-10) is preferable.

As the structural unit (a2 ′), one type may be used alone, or two or more types may be used in combination.
The structural unit (a2 ′) is not an essential component of the component (A). However, when the structural unit (a2 ′) is contained in the component (A), the structural unit is based on the total of all the structural units constituting the component (A). It is preferable to contain (a2 ′) in an amount of 1 to 30 mol%, preferably 5 to 20 mol%.

The structural unit (a3) is a structural unit derived from an (α-lower alkyl) acrylate ester containing a polar group-containing aliphatic hydrocarbon group, which is not classified as the structural unit (a0). By having 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.
Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, and a hydroxyalkyl group in which a part of hydrogen atoms of an alkyl group is substituted with a fluorine atom. A hydroxyl group is particularly preferable.
Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group having 1 to 10 carbon atoms (preferably an alkylene group) and a polycyclic aliphatic hydrocarbon group (polycyclic group). . As the polycyclic group, for example, a resin for a resist composition for ArF excimer laser can be appropriately selected from among many proposed ones.
Among them, an aliphatic polycyclic group containing a hydroxyalkyl group in which a part of hydrogen atoms of a hydroxyl group, a cyano group, a carboxy group, or an alkyl group is substituted with a fluorine atom, and (α-lower alkyl) acrylic A structural unit derived from an acid ester is more preferred. Examples of the polycyclic group include groups in which one or more hydrogen atoms have been removed from bicycloalkane, tricycloalkane, tetracycloalkane, or the like. Specific examples include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane. Such a polycyclic group can be appropriately selected and used from among many proposed polymers (resin components) for resist compositions for ArF excimer lasers. Among these polycyclic groups, there are groups in which two or more hydrogen atoms have been removed from adamantane, groups in which two or more hydrogen atoms have been removed from norbornane, and groups in which two or more hydrogen atoms have been removed from tetracyclododecane. Industrially preferable.

  As the structural unit (a3), 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, (α-lower alkyl) acrylic acid A structural unit derived from hydroxyethyl ester is preferred, and when the hydrocarbon group is a polycyclic group, a structural unit represented by the following formula (a3-1), a structural unit represented by (a3-2) The structural unit represented by (a3-3) is preferable.

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

(Wherein R is the same as above, j is an integer of 1 to 3, k is an integer of 1 to 3, t ′ is an integer of 1 to 3, and l is an integer of 1 to 5) And s is an integer of 1 to 3.)

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

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

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

As the structural unit (a3), one type may be used alone, or two or more types may be used in combination.
The structural unit (a3) is not an essential component of the component (A). However, when the structural unit (a3) is contained in the component (A), the structural unit (A) is included in the total of all the structural units constituting the component (A) ( It is preferable that a3) is contained in an amount of 1 to 30 mol%, preferably 5 to 20 mol%.

The structural unit (a4) is particularly limited as long as it is not classified into any of the structural units (a0), (a1), (a2), (a1 ′), (a2 ′), and (a3). There are many known materials that are conventionally used as resist resins for ArF excimer laser and KrF positive excimer laser (preferably for ArF excimer laser).
As the structural unit (a4), for example, a structural unit derived from an (α-lower alkyl) acrylate ester containing an acid non-dissociable, aliphatic polycyclic group containing no polar group is preferable. Examples of the polycyclic group include those similar to those exemplified in the case of the structural unit (a1), and for ArF excimer laser and KrF positive excimer laser (preferably for ArF excimer laser). A number of hitherto known materials can be used for the resin component of the resist composition.
In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, a tetracyclododecanyl group, an isobornyl group, and a norbornyl group is preferable in terms of industrial availability. These polycyclic groups may be substituted with a linear or branched alkyl group having 1 to 5 carbon atoms.
Specific examples of the structural unit (a4) include those represented by the following general formulas (a4-1) to (a4-5).

（式中、Ｒは前記と同じである。）

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

As the structural unit (a4), one type may be used alone, or two or more types may be used in combination.
The structural unit (a4) is not an essential component of the component (A). However, when the structural unit (a4) is contained in the component (A), the structural unit (A) is included in the total of all the structural units constituting the component (A). It is preferable to contain a4) in an amount of 1 to 30 mol%, preferably 10 to 20 mol%.

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 group. As described above, a copolymer into which a hydroxyalkyl group in which a part of hydrogen atoms of an alkyl group is substituted with a fluorine atom is introduced has reduced development defects and LER (line edge roughness: uneven unevenness of line side walls). It is effective in reducing

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

  The proportion of the component (A) in the positive resist composition can be appropriately adjusted depending on the intended resist film thickness.

<(B) component>
The component (B) is not particularly limited, and any component that has been proposed as an acid generator for a chemically amplified positive resist 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.

  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.

  An oxime sulfonate acid generator represented by the following chemical formula can also be used.

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. 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.

The positive resist composition of the present invention is produced by dissolving the above components (A) and (B) and various optional components described below in an organic solvent (hereinafter sometimes referred to as component (C)). Can do.
As the component (C), any organic solvent may be used as long as it can dissolve each component to be used to form a uniform solution, and any conventionally known solvent for chemical amplification resists can be used. One or two or more can be appropriately selected and used.
For example, lactones such as γ-butyrolactone, ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate Polyhydric alcohols such as dipropylene glycol or dipropylene glycol monoacetate monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and derivatives thereof, cyclic ethers such as dioxane, Methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, pyruvate Le, methyl methoxypropionate, esters such as ethyl ethoxypropionate can be exemplified.
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.
A mixed solvent obtained by mixing propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent is preferable. The 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: 9: 1, more preferably 2: 8 to 8: A range of 2 is preferable.
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.
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.
(C) Although the usage-amount of a component is not specifically limited, Although it is a density | concentration which can be apply | coated to a board | substrate etc. and is suitably set according to a coating film thickness, generally the solid content concentration 2-2 of a resist composition. It is used so that it may become in the range of 20 mass%, Preferably 5-15 mass%.

In order to improve the resist pattern shape, the stability over time, etc., the positive resist composition is further mixed with a nitrogen-containing organic compound (D) (hereinafter referred to as (D) component) as an optional component. Can do.
Since a wide variety of components (D) have already been proposed, any known one may be used. For example, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, monoalkylamines such as n-decylamine; dialkylamines such as diethylamine, di-n-propylamine, di-n-heptylamine, di-n-octylamine, dicyclohexylamine; trimethylamine, triethylamine, tri-n-propylamine, Tri-n-butylamine, tri-n-hexylamine, tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine, tri-n-decanylamine, tri-n- Trialkylamines such as dodecylamine; diethanolamine, trieta Ruamin, diisopropanolamine, triisopropanolamine, di -n- octanol amine, alkyl alcohol amines tri -n- octanol amine is Ageraru. Among these, secondary aliphatic amines and tertiary aliphatic amines are preferable, and tertiary alkanolamines such as triethanolamine or triisopropanolamine 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.

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

  The positive resist composition of the present invention further contains miscible additives as desired, for example, additional resins for improving the performance of the resist film, surfactants for improving coating properties, dissolution inhibitors, Plasticizers, stabilizers, colorants, antihalation agents, dyes, and the like can be added and contained as appropriate.

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

According to the present invention described above, a positive resist composition and a resist pattern forming method capable of forming a resist pattern having excellent shape and etching resistance can be provided. The reason why such an effect is obtained is not clear, but the etching resistance is improved because the structural unit (a0) has a polycyclostructure having a high carbon density called a tetracyclododecane skeleton. By bonding to the terminal of the cyclododecane skeleton, that is, at a position away from the polymer main chain, and the cyano group is directed toward the outside of the polymer main chain, the effect of having the cyano group is exerted strongly. It is thought that the shape and the shape are improved by improving the tilting and LWR.
The positive resist composition of the present invention further comprises a resist pattern corresponding to a different mask dimension on the reticle when exposed under the same mask linearity [the same exposure condition (the mask dimension on the reticle is different but the exposure amount is the same)]. It also has excellent characteristics that can be accurately reproduced.

Examples of the present invention will be described below, but the scope of the present invention is not limited to these examples. In the following synthesis examples 1 and 2, the following conditions were used for the analysis by gas chromatography and the measurement of mass average molecular weight (Mw) and dispersity (Mw / Mn) by GPC.
<Gas chromatography analysis conditions>
Column: TC-1 0.25 mm, 30 m, 0.25 μm manufactured by GC Sciences
Carrier gas: Helium Detector: FID
Inlet temperature: 250 ° C
Detector temperature: 280 ° C
Column tank temperature: Initial temperature 100 ° C. (hold for 5 minutes)
Temperature increase rate 10 ℃ / min
Final temperature 280 ℃
Injection volume: 0.2 μL
<GPC analysis conditions>
Column: Tosoh TSK-GEL G2000H _XL
7.8 mm (ID) x 300 mm (L) x 2 Mobile phase: TH1F 1 mL / min Detector: RI
Column bath temperature: 40 ° C
Injection volume: 50 μL (0.1% THF solution)

[Synthesis Example 1] <Tetracyclo [6.2.1 ^3,6 . 0 ^2,7 ] Dodeca-9-ene-4-carbonitrile methacrylate reaction, amount of methacrylic acid to CN group of polycyclic olefin: 6.0 equivalents>
A tetracyclo [6.2.1 ^3,6 . 0 ^2,7 ] dodec-9-ene-4-carbonitrile (hereinafter abbreviated as CNCp2) 10.0 g (54.1 mmol), methacrylic acid 27.9 g (324.3 mmol, 6 equivalents to the CNC group of CNCp2) ), 3.16 g of BF ₃ · Et ₂ O complex (22.3 mmol, 0.4 mol equivalent to substrate), 10 mg of p-methoxyphenol as a polymerization inhibitor, 0.21 g of biphenyl (GC analysis internal standard), as a solvent Ethyl acetate (33 mL) was charged, and the reaction was performed for 3 hours while maintaining the system temperature at 80 ° C.
As a result of analyzing the reaction solution after 3 hours by gas chromatography, it was found that the conversion was 99.2 mol%, and the target 10- (or 9-) cyanotetracyclo [6.2.1 ^3,6 . The yield of 0 ^2,7 ] dodecan-4-yl methacrylate (hereinafter abbreviated as CNCp2MA) was 68.0 mol%. Moreover, the by-product amount of methacrylic anhydride in the reaction solution was 19.8 mol% with respect to CNCp2MA. During the reaction, no polymer precipitation was observed, and a uniform liquid phase was maintained.
After returning the reaction solution to room temperature, 33 mL of water was added to deactivate the catalyst. To this, 47 mL of ethyl acetate was added and washed 4 times with 33 mL of 10% Na ₂ CO ₃ solution to neutralize excess methacrylic acid and remove it to the aqueous phase. Thereafter, the organic phase was washed with 16 mL of water three times, 10 mg of p-methoxyphenol was added, and the solvent was distilled off with a rotary evaporator. Next, the by-product methacrylic anhydride was decomposed. To the oil obtained as described above, 33 mL of methyl ethyl ketone and 44 mL of 10% aqueous Na ₂ CO ₃ solution were added, and the mixture was vigorously stirred so that the two phases were well mixed at room temperature. After 4 hours, gas chromatographic analysis confirmed that methacrylic anhydride was below the detection limit, and then 47 mL of ethyl acetate was added to separate the two phases. The organic phase was washed 3 times with 16 mL of water, 5 mg of p-methoxyphenol was added, and the solvent was sufficiently distilled off with a rotary evaporator to obtain CNCp2MA.
The structure of CNCp2MA is shown below.

[Synthesis Example 2] Synthesis of Resin 1 10.9 g of CNCp2MA synthesized in Synthesis Example 1, 18.7 g of 2-methyl-2-adamantyl methacrylate, and 13.6 g of γ-butyrolactone methacrylate were dissolved in 200 ml of tetrahydrofuran. 1.64 g of isobutyronitrile was added. After refluxing for 6 hours, the reaction solution was added dropwise to 1 L of n-heptane. The precipitated resin was separated by filtration and dried under reduced pressure to obtain a white powder resin. This is Resin 1. The weight average molecular weight (Mw) was 7000, the dispersity (Mw / Mn) was 1.7, and p: q: r = 40: 40: 20 (molar ratio). Resin 1 is a mixture of compounds in which a cyano group is bonded to the 9th or 10th position of the tetracyclododecanyl group.

[Synthesis Example 3] Synthesis of Resin 2 10.9 g of CNCp2MA synthesized in Synthesis Example 1, 15.7 g of 1-ethyl-1-cyclohexyl methacrylate and 13.6 g of γ-butyrolactone methacrylate were dissolved in 200 ml of tetrahydrofuran. 1.64 g of isobutyronitrile was added. After refluxing for 6 hours, the reaction solution was added dropwise to 1 L of n-heptane. The precipitated resin was separated by filtration and dried under reduced pressure to obtain a white powder resin. This is Resin 2. The weight average molecular weight (Mw) was 7000, the dispersity (Mw / Mn) was 1.7, and p: q: r = 40: 40: 20 (molar ratio). Resin 2 is a mixture of compounds in which a cyano group is bonded to the 9th or 10th position of the tetracyclododecanyl group.

[Synthesis Example 4] Synthesis of Resin 3 5.4 g of CNCp2MA synthesized in Synthesis Example 1, 18.7 g of 2-methyl-2-adamantyl methacrylate, and 17.0 g of γ-butyrolactone methacrylate were dissolved in 200 ml of tetrahydrofuran. 1.64 g of isobutyronitrile was added. After refluxing for 6 hours, the reaction solution was added dropwise to 1 L of n-heptane. The precipitated resin was separated by filtration and dried under reduced pressure to obtain a white powder resin. This is designated as resin 3. The weight average molecular weight (Mw) was 7000, the dispersity (Mw / Mn) was 1.7, and p: q: r = 40: 50: 10 (molar ratio). Resin 3 is a mixture of compounds in which a cyano group is bonded to the 9th or 10th position of the tetracyclododecanyl group.

Example 1
Component (A) below: 100 parts by mass of resin 1, Component (B): 3.5 parts by mass of triphenylsulfonium nonafluorobutane sulfonate, and component (D): 0.35 parts by mass of triethanolamine, propylene glycol monomethyl ether A positive resist composition was prepared by dissolving in 1150 parts by mass of a mixed solvent of acetate / ethyl lactate = 8/2.

Example 2
A positive resist composition was prepared in the same manner as in Example 1 except that the resin 2 was used as the component (A).

Comparative Example 1
Comparative resin 1 represented by the following formula as component (A) (mass average molecular weight (Mw) = 7000, dispersity (Mw / Mn) = 1.7, p: q: r = 40: 40: 20 (molar ratio) )) Was used, and a positive resist composition was prepared in the same manner as in Example 1. Comparative resin 1 is a mixture of compounds in which a cyano group is bonded to the 5-position or 6-position of a 2-norbornyl group.

Comparative Example 2
Comparative resin 2 represented by the following formula as component (A) (mass average molecular weight (Mw) = 7000, dispersity (Mw / Mn) = 1.7, p: q: r = 40: 40: 20 (molar ratio) )) Was used, and a positive resist composition was prepared in the same manner as in Example 1.

<Evaluation>
The following evaluations were performed using the positive resist compositions prepared in Examples 1 and 2 and Comparative Examples 1 and 2. Table 1 shows the pre-bake (PAB) temperature and post-exposure heating (PEB) temperature used in the following evaluation.

[Evaluation of footing]
Using the positive resist compositions prepared in Example 1 and Comparative Examples 1 and 2, a resist pattern was formed as follows and footing was evaluated.
First, an organic antireflection film composition “ARC-29A” (trade name, manufactured by Brewer Science Co., Ltd.) was applied onto an 8-inch silicon wafer using a spinner, and baked on a hot plate at 215 ° C. for 60 seconds. By drying, an organic antireflection film having a thickness of 77 nm was formed.
Then, the positive resist composition obtained above is applied onto the antireflection film using a spinner, and prebaked (PAB) for 90 seconds at the PAB temperature shown in Table 1 on a hot plate, and then dried. As a result, a resist film having a thickness of 250 nm was formed.
Subsequently, ArF excimer laser (193 nm) was selectively irradiated through the mask pattern by an ArF exposure apparatus NSR-S302 (manufactured by Nikon Corporation; NA (numerical aperture) = 0.60, 2/3 ring zone).
Then, a post-exposure heating (PEB) treatment for 90 seconds was performed at the PEB temperature shown in Table 1, followed by paddle development with an aqueous 2.38 mass% tetramethylammonium hydroxide (TMAH) solution at 23 ° C. for 30 seconds, and then 20 Washed with water for 2 seconds and dried.
When the exposure amount Eop at which a line and space (L / S) pattern (pitch 240 nm) having a line width of 120 nm was formed by such an operation was measured in units of mJ / cm ² (energy amount), Example 1 was 28. 0.0 mJ / cm ² , Comparative Example 1 was 27.0 mJ / cm ² , and Comparative Example 2 was 22.0 mJ / cm ² .
When the cross-sectional shape of the resist pattern at this time was observed with an SEM photograph, the resist pattern of Example 1 had no footing and high rectangularity. On the other hand, footing was slightly observed in the resist patterns of Comparative Examples 1 and 2.

[Evaluation of etching resistance]
Using the positive resist compositions prepared in Example 1 and Comparative Example 1, the etching resistance was evaluated as follows.
8 inch silicon at a pressure of 300 mTorr and a temperature of 20 ° C. using a mixed gas of tetrafluoromethane (CF ₄ ), trifluoromethane (CHF ₃ ) and helium (flow rate (ml / min) ratio 40: 40: 120) as an etching gas. By applying the positive resist composition obtained above on a wafer using a spinner on a wafer, performing a pre-bake (PAB) treatment for 90 seconds at a PAB temperature shown in Table 1 on a hot plate, and drying, A resist film having a thickness of 450 nm was formed. After pre-baking, an ArF excimer laser (193 nm) was exposed without passing through a mask pattern by an ArF exposure apparatus NSR-S302 (manufactured by Nikon; NA (numerical aperture) = 0.60, 2/3 ring zone), and the above The resist film subjected to PEB treatment (hereinafter referred to as unpatterned resist film) is processed for 90 seconds at an output of 700 W with an etching apparatus (trade name “TCE-7612X” manufactured by Tokyo Ohka Kogyo Co., Ltd.). Then, after dry etching, the resist film surface was observed with an AFM (atomic force microscope: di NanoScope IV / D5000 manufactured by Veeco Instrument Inc.).
As a result, the resist film surface of Example 1 had no surface roughness and was highly smooth. On the other hand, in Comparative Example 1, the surface roughness was severe. The reason why the surface roughness was evaluated using the unpatterned resist film is that the surface roughness is easier to measure than in the case of the patterned resist film.
Further, when the film thickness of the resist film of Example 1 was compared with the film thickness of the resist film of Comparative Example 1, the film thickness of the resist film of Example 1 was the same as that of the resist film of Comparative Example 1. It was 91% of the reduction amount. Here, the “film reduction amount” is a value obtained by subtracting the film thickness after etching from the film thickness of the resist film before etching.

[Evaluation of LWR]
Using the positive resist compositions prepared in Examples 1 and 2 and Comparative Example 1, LWR was evaluated as follows.
A 90 nm L / S pattern was formed in the same manner as in the above [Evaluation of footing] except that the ArF exposure apparatus NSR-S306 (manufactured by Nikon; NA (numerical aperture) = 0.78, 2/3 ring zone) was used. Formed. Then, the line width was measured at five locations in the line direction by a side length SEM (manufactured by Hitachi, Ltd., trade name: S-9220), and the triple value (3σ) of the standard deviation (σ) was obtained from the result. Calculated as a measure of LWR. The smaller this 3σ value, the smaller the roughness of the line width, which means that a resist pattern with a more uniform width was obtained.
As a result, the value of 3σ was 7.4 nm in Example 1, 7.0 nm in Example 2, and 8.6 nm in Comparative Example 1.

[Evaluation of mask linearity]
Using the positive resist compositions prepared in Examples 1 and 2 and Comparative Example 1, mask linearity was evaluated as follows.
In the exposure amount (Eop) obtained in the above [Evaluation of LWR], the size of the mask (L / S pattern, 1: 1) is changed from 90 nm to 200 nm, and a resist pattern is formed in the same manner as described above. The size of the resist pattern to be measured was measured.
As a result, each of Examples 1 and 2 and Comparative Example 1 had good mask linearity, and resist patterns corresponding to different mask dimensions could be accurately reproduced. In particular, Example 2 was excellent in mask linearity.

As is clear from the above results, the resist patterns having excellent shapes with no footing and reduced LWR were formed by the positive resist compositions of Examples 1 and 2. Moreover, the etching resistance was also high. Furthermore, it was excellent in mask linearity.
On the other hand, the resist patterns obtained using the positive resist compositions of Comparative Examples 1 and 2 had poor shapes such as footing and large LWR. Further, the etching resistance was low, the surface roughness was remarkable, and the film was greatly reduced.

Further, after preparing a positive resist composition with the same composition as in Example 1 using Resin 3 of Synthesis Example 4, the resist pattern was evaluated in the same manner and evaluated. As a result, the mask linearity was superior to that of Comparative Example 1, and the LWR value was also excellent at 7.4 nm. Moreover, footing was also suppressed.

Claims (6)

A positive resist composition comprising a resin component (A) whose alkali solubility is increased by the action of an acid, and an acid generator component (B) that generates an acid upon exposure,
The resin component (A) is represented by the following general formula (a0-1)

[Wherein, R represents a hydrogen atom or a lower alkyl group. ]
A structural unit (a0) represented by the following general formula (a1-11) or (a1-12)

[Wherein, R is a hydrogen atom or a lower alkyl group, R ^{1 to} R ² are each independently an alkyl group having 1 to 4 carbon atoms, and t is an integer of 1 to 3. ]
At least one structural unit (a1) selected from the group consisting of structural units represented by the following general formula (a2-1):

[Wherein, R represents a hydrogen atom or a lower alkyl group, and R ′ represents a hydrogen atom, a lower alkyl group, or an alkoxy group having 1 to 5 carbon atoms. ]
A positive resist composition having a structural unit (a2) represented by:   The positive resist composition according to claim 1, wherein the proportion of the structural unit (a0) is 10 to 60 mol% with respect to the total of all the structural units constituting the resin component (A).   The positive resist composition according to claim 1 or 2, wherein the proportion of the structural unit (a1) is 10 to 80 mol% with respect to the total of all the structural units constituting the resin component (A).   The ratio of the said structural unit (a2) is 10-80 mol% with respect to the sum total of all the structural units which comprise the said resin component (A), The positive resist of any one of Claims 1-3 Composition.   The positive resist composition according to claim 1, comprising a nitrogen-containing organic compound (D). A step of forming a resist film on a substrate using the positive resist composition according to claim 1, a step of exposing the resist film, and developing the resist film to form a resist pattern Forming a resist pattern.