JP2005128572A - Positive resist composition and method for forming resist pattern using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive resist composition which ensures small surface roughness and line edge roughness during etching and has excellent resolution and a wide focal-depth range, and to provide a method for forming a resist pattern. <P>SOLUTION: The positive resist composition contains a resin (A), an acid generating agent (B) and an organic solvent (C). The resin ingredient (A) has both of a structural unit derived from a methacrylate ester and a structural unit derived from an acrylate ester, and has a structural unit containing a polycyclic group-containing acid-dissociating dissolution-inhibiting group and derived from a (meth)acrylate ester, a structural unit containing a lactone-containing monocyclic or polycyclic group and derived from a (meth)acrylate ester, and a structural unit containing a hydroxyl group-containing polycyclic group and derived from a (meth)acrylate ester, and further contains a structural unit (a4) containing a polycyclic group excluding the above acid-dissociating dissolution-inhibiting group, the above lactone-containing monocyclic group or polycyclic group and the above hydroxyl group-containing polycyclic group, and derived from a (meth)acrylate ester. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a positive resist composition, and more particularly to a chemically amplified positive resist composition for wavelengths of 200 nm or less, particularly for ArF excimer lasers.

Conventionally, as the base resin component of the chemically amplified resist, polyhydroxystyrene having high transparency to KrF excimer laser (248 nm) and those obtained by protecting the hydroxyl group with an acid dissociable, dissolution inhibiting group have been used.
However, today, the miniaturization of semiconductor elements is further advanced, and development of a process using an ArF excimer laser (193 nm) is being energetically advanced.
In a process using an ArF excimer laser as a light source, a resin having a benzene ring such as polyhydroxystyrene described above has insufficient transparency with respect to an ArF excimer laser (193 nm).
Therefore, it is derived from a (meth) acrylic acid ester having a benzene ring and having a polycyclic hydrocarbon group such as an adamantane skeleton in the ester portion, which has no benzene ring and has excellent dry etching resistance. Resin having a structural unit as a main chain has attracted attention, and many proposals have been made so far [Patent Document 1 (Patent No. 2881969), Patent Document 2 (JP-A-5-346668), Patent Literature 3 (JP-A-7-234511), Patent Document 4 (JP-A-9-73173), Patent Document 5 (JP-A-9-90637), Patent Document 6 (JP-A-10-161313), Patent Document 7 (Japanese Patent Laid-Open No. 10-319595) and Patent Document 8 (Japanese Patent Laid-Open No. 11-12326)].

By the way, with the diversification of the film to be etched in recent years, various etching gases have been used, and as a result, a new problem has arisen that surface roughness occurs in the resist film after etching.
Unlike the conventional dry etching resistance, this surface roughness appears as distortion around the hole pattern in the contact hole pattern in the film etched using the resist pattern as a mask, and the line edge roughness in the line and space pattern. Appears as Note that the line edge roughness is uneven unevenness of the line side wall.

In addition to the above surface roughness, there is another problem that line edge roughness occurs in the resist pattern after development.
The line edge roughness causes distortion around the hole in the hole resist pattern, and uneven unevenness on the side wall in the line and space pattern.
In recent years, the design rules required in the manufacture of semiconductor elements have become narrower, and resolutions of 150 nm or less or around 100 nm are required. Therefore, an improvement in resolution is desired.
Furthermore, in addition to such an improvement in resolution, it is desired to widen the depth of focus width characteristic.
Japanese Patent No. 2881969 JP-A-5-346668 JP-A-7-234511 JP-A-9-73173 JP-A-9-90637 JP-A-10-161313 JP 10-319595 A Japanese Patent Laid-Open No. 11-12326

However, conventional resist compositions are insufficient to solve these problems, and improvements have been desired.
Therefore, an object of the present invention is to provide a chemically amplified positive resist composition having little surface roughness and line edge roughness during etching, excellent resolution, and wide depth of focus, and a resist pattern forming method using the same Is to provide.

As a result of careful examination in view of the above circumstances, the present inventors, as a base resin component, have both a structural unit derived from a methacrylic acid ester and a structural unit derived from an acrylate ester. It was found that the above-mentioned problems can be solved by using it, and the present invention was completed.
That is, the positive resist composition of the present invention has a polycyclic group-containing acid dissociable, dissolution inhibiting group in the ester side chain portion, and a structural unit derived from (meth) acrylic acid ester in the main chain. A positive resist composition comprising a resin component (A) whose alkali solubility is increased by the action of an acid, an acid generator component (B) that generates acid upon exposure, and an organic solvent (C),
The component (A) has both a structural unit derived from a methacrylic acid ester and a structural unit derived from an acrylate ester,
The component (A) is
A structural unit containing a polycyclic group-containing acid dissociable, dissolution inhibiting group and derived from a (meth) acrylic acid ester,
A structural unit containing a lactone-containing monocyclic or polycyclic group and derived from a (meth) acrylic ester, and
Containing a hydroxyl group-containing polycyclic group and having a structural unit derived from a (meth) acrylic acid ester, and
The component (A) is
And a polycyclic group other than the polycyclic group-containing acid dissociable dissolution inhibiting group, the lactone-containing monocyclic or polycyclic group, the hydroxyl group-containing polycyclic group, and a (meth) acrylic acid ester. It includes a derived structural unit (a4).
“(Meth) acrylic acid” refers to one or both of methacrylic acid and acrylic acid. The “structural unit” refers to a monomer unit constituting the polymer.
Moreover, the method for forming the resist pattern of the present invention comprises applying the positive resist composition of the present invention on a substrate, pre-baking, selectively exposing, then applying PEB (post-exposure heating), A resist pattern is formed by alkali development.

  In the positive resist composition and resist pattern forming method of the present invention, a chemically amplified type that can reduce surface roughness and line edge roughness during etching, has excellent resolution, has a wide focal depth range, and can reduce defects. And a resist pattern forming method using the same.

Hereinafter, the present invention will be described in detail.
In the component (A), when the acid generated from the component (B) acts upon exposure, the polycyclic group-containing acid dissociable, dissolution inhibiting group having excellent etching resistance is dissociated, and the entire component (A) Changes from alkali-insoluble to alkali-soluble.
For this reason, when the resist pattern is exposed through the mask pattern, the alkali solubility in the exposed portion is increased and alkali development can be performed.

In addition, in the component (A), “having both a methacrylic ester structural unit and an acrylate structural unit” means that the component (A) includes a methacrylic ester structural unit and an acrylate structural unit. If it has, the form will not be specifically limited, For example, the said (A) component is,
-Copolymer (A1): a copolymer containing a methacrylic ester structural unit and an acrylate structural unit,
May be included,
Mixed resin (A2): a mixed resin of a polymer containing at least a methacrylic ester structural unit and a polymer containing at least an acrylate structural unit,
May be included. One or both of these polymers constituting the mixed resin (A2) may correspond to the copolymer (A1).
In addition, in the component (A), other resin components can be blended within a range not impairing the effects of the present invention. In the present invention, the component (A) includes the copolymer (A1) and the above-described component. What consists of any one or both of mixed resin (A2) is preferable.
Moreover, in the copolymer (A1) and the mixed resin (A2), two or more different types can be used in combination.
And the methacrylic acid ester structural unit and the acrylic acid ester structural unit in the component (A) are the methacrylic acid ester structural unit with respect to the total number of moles of the methacrylic acid ester structural unit and the acrylate structural unit. It is preferable to use 10 to 85 mol%, preferably 20 to 80 mol%, and 15 to 90 mol%, preferably 20 to 80 mol% of the acrylic ester structural unit.
When there are too many methacrylic ester structural units, the effect of improving the surface roughness is reduced, and when there are too many acrylate structural units, the resolution may be lowered.

Moreover, (A) component consists of the combination of the monomer unit which has a several different function, for example, However, The said methacrylic ester structural unit and the said acrylate ester structural unit are any monomer units which comprise (A) component May be included.
For example, the component (A) is preferably
A structural unit containing a polycyclic group-containing acid dissociable, dissolution inhibiting group and derived from a (meth) acrylic acid ester (hereinafter sometimes referred to as a first structural unit),
A structural unit containing a lactone-containing monocyclic or polycyclic group and derived from a (meth) acrylic acid ester (hereinafter sometimes referred to as a second structural unit),
A structural unit containing a hydroxyl group-containing polycyclic group and derived from a (meth) acrylic acid ester (hereinafter sometimes referred to as a third structural unit),
And so on. In this case, the first structural unit is indispensable, and may be two kinds of the first structural unit and the second structural unit or the third structural unit, but includes all of the first to third structural units. However, it is preferable from the viewpoint of etching resistance, resolution, adhesion between the resist film and the substrate, and further, those composed of these three kinds of structural units are preferable.
Furthermore, the component (A) is the following structural unit (hereinafter sometimes referred to as a fourth structural unit or structural unit (a4)).
-The polycyclic group-containing acid dissociable dissolution inhibiting group of the first structural unit, the lactone-containing monocyclic or polycyclic group of the second structural unit, and the hydroxyl group-containing polycyclic group of the third structural unit A structural unit containing a polycyclic group other than and derived from a (meth) acrylic ester,
In particular, it is excellent in resolution 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), which is preferable.
Therefore, the combination of the first structural unit to the fourth structural unit can be appropriately adjusted according to required characteristics.

And (A) component is
A polycyclic group-containing acid dissociable, dissolution inhibiting group, and an acrylic ester structural unit (a1);
It preferably contains a polycyclic group-containing acid dissociable, dissolution inhibiting group and one or both of the structural units (a1 ′) derived from methacrylic acid esters.
Preferably, the structural unit includes a polycyclic group-containing acid dissociable, dissolution inhibiting group, and includes both the structural unit (a1) and the structural unit (a1 ′) as a structural unit derived from a (meth) acrylic acid ester. As a result, the effect of improving the resolution can be obtained.
When both are included, the molar ratio of the structural unit (a1): the structural unit (a1 ′) is 0 because the polymer having the structural unit (a1) and the polymer having the structural unit (a1 ′) are excellent in compatibility. .4: 2.5, preferably 0.6: 1.5.

The component (A) contains a lactone-containing monocyclic or polycyclic group and is derived from an acrylate ester (a2);
It preferably contains a lactone-containing monocyclic or polycyclic group and contains one or both of the structural unit (a2 ′) derived from a methacrylic acid ester.
Preferably, it includes a lactone-containing monocyclic or polycyclic group and includes both the structural unit (a2) and the structural unit (a2 ′) as a structural unit derived from a (meth) acrylic acid ester. is there.
When both are included, since the compatibility of the polymer having the structural unit (a2) and the polymer having the structural unit (a2 ′) is excellent, the molar ratio of the structural unit (a2): the structural unit (a2 ′) is 0. It is 2 to 5.0, preferably 0.6 to 1.5.

Furthermore, the structural unit (a3) in which the component (A) includes a hydroxyl group-containing polycyclic group and is derived from an acrylate ester,
It is preferable that it contains one or both of the structural unit (a3 ′) derived from a methacrylic acid ester and containing a hydroxyl group-containing polycyclic group.
Preferably, it is a case containing both the structural unit (a3) and the structural unit (a3 ′) as a structural unit containing a hydroxyl group-containing polycyclic group and derived from a (meth) acrylic acid ester.
When both are included, since the compatibility of the polymer having the structural unit (a3) and the polymer having the structural unit (a3 ′) is excellent, the molar ratio of the structural unit (a3): the structural unit (a3 ′) is 0. It is 2 to 5.0, preferably 0.6 to 1.5.

  A set of the structural units (a1) and (a1 ′), a set of the structural units (a2) and (a2 ′), and a set of the structural units (a3) and (a3 ′), Of the three pairs of combinations, two or more pairs are preferably included, and all three pairs are more preferably included.

In the structural units (a1) and (a1 ′), examples of the polycyclic group include groups in which one hydrogen element is removed from bicycloalkane, tricycloalkane, teracycloalkane, 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.
Such a polycyclic group can be appropriately selected and used from among many proposed ArF resists.
Of these, an adamantyl group, a norbornyl group, and a tetracyclododecanyl group are industrially preferable.
The acid dissociable, dissolution inhibiting group has an alkali dissolution inhibiting property that makes the entire component (A) insoluble before exposure, and dissociates after the exposure by the action of an acid generated from the component (B), Anything can be used without particular limitation as long as the entire component (A) is changed to alkali-soluble.
In general, those that form a cyclic or chain tertiary alkyl ester with a carboxyl group of (meth) acrylic acid are widely known.

  The structural units (a1) and (a1 ′) are not particularly limited as long as they have such a function, but one or both of the structural units (a1) and (a1 ′) (preferably both) ), The polycyclic group-containing acid dissociable, dissolution inhibiting group is selected from the following general formula (I), (II) or (III): It is preferable because of its excellent resistance.

（式中、Ｒ^１は低級アルキル基である。）

(In the formula, R ¹ is a lower alkyl group.)

（式中、Ｒ^２及びＲ^３は、それぞれ独立に、低級アルキル基である。）

(In the formula, R ² and R ³ are each independently a lower alkyl group.)

（式中、Ｒ^４は第３級アルキル基である。）

(In the formula, R ⁴ is a tertiary alkyl group.)

  Specifically, at least one of structural units (a1) and (a1 ′) or both (preferably both) is selected from the following general formula (I ′), (II ′) or (III ′): A seed is preferred.

（式中、Ｒは水素原子又はメチル基、Ｒ^１は低級アルキル基であり、Ｒが水素原子のとき構成単位（ａ１）となり、メチル基のとき構成単位（ａ１'）となる。）

(In the formula, R is a hydrogen atom or a methyl group, R ¹ is a lower alkyl group, and when R is a hydrogen atom, it is a structural unit (a1), and when R is a methyl group, it is a structural unit (a1 ′).)

（式中、Ｒは水素原子又はメチル基、Ｒ^２及びＲ^３はそれぞれ独立して低級アルキル基であり、Ｒが水素原子のとき構成単位（ａ１）となり、メチル基のとき構成単位（ａ１'）となる。）

(In the formula, R is a hydrogen atom or a methyl group, R ² and R ³ are each independently a lower alkyl group. When R is a hydrogen atom, it is a structural unit (a1), and when R is a methyl group, a structural unit (a1 ′ )

（式中、Ｒは水素原子又はメチル基、Ｒ^４は第３級アルキル基であり、Ｒが水素原子のとき構成単位（ａ１）となり、メチル基のとき構成単位（ａ１'）となる。）

(In the formula, R is a hydrogen atom or a methyl group, R ⁴ is a tertiary alkyl group, and when R is a hydrogen atom, it is a structural unit (a1), and when R is a methyl group, it is a structural unit (a1 ′).)

In the structural unit represented by the general formula (I ′), the carbon atom adjacent to the oxygen atom (—O—) of the ester portion of (meth) acrylic acid is a tertiary group on a ring skeleton such as an adamantyl group. This is the case when it becomes an alkyl group.
In the general formulas (I) and (I ′), R is a hydrogen atom or a methyl group.
R ¹ is preferably a lower 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, an n-butyl group, an isobutyl group, or a tert-butyl group. , A pentyl group, an isopentyl group, a neopentyl group, and the like. Among them, an alkyl group having 2 or more carbon atoms, preferably 2 to 5 carbon atoms is preferable, and in this case, acid dissociation tends to be higher than in the case of a methyl group. Among these, a methyl group is preferred industrially.

In the structural unit represented by the general formula (II ′), the carbon atom adjacent to the oxygen atom (—O—) of the ester portion of (meth) acrylic acid is a tertiary alkyl group, Furthermore, there is a case where a ring skeleton such as an adamantyl group is present.
In the general formulas (II) and (II ′), R is the same as in the general formulas (I) and (I ′).
R ² and R ³ each independently preferably represent a lower alkyl group having 1 to 5 carbon atoms. Such groups tend to be more acid dissociable than 2-methyl-2-adamantyl groups.
Specifically, R ² and R ³ each independently include the same lower linear or branched alkyl group as R ¹ described above. Among them, the case where R ² and R ³ are both methyl groups is industrially preferable.

The structural unit represented by the general formula (III ′) is not a (meth) acrylic ester part, but a carbon atom adjacent to an oxygen atom (—O—) of another ester is a tertiary alkyl group, This is a case where a (meth) acrylic acid ester and the ester are linked by a ring skeleton such as a tetracyclododecanyl group.
In the general formulas (III) and (III ′), R is the same as in the general formulas (I ′) and (II ′).
R ⁴ is a tertiary alkyl group such as a tert-butyl group or a tert-amyl group, and the case where it is a tert-butyl group is industrially preferred.

Among these, it is particularly preferable to use one or both (preferably both) of the structural units represented by the general formulas (I ′) and (II ′), and R ¹ is a methyl group, R ² and R ^3. Is preferably a methyl group because of excellent resolution.

In the structural units (a2) and (a2 ′), the lactone functional group is effective for increasing the adhesion between the resist film and the substrate and increasing the hydrophilicity with the developer.
The structural units (a2) and (a2 ′) are not particularly limited as long as they have both such a lactone functional group and a monocyclic or polycyclic group.
For example, examples of the lactone-containing monocyclic group include groups obtained by removing one hydrogen atom from γ-butyrolactone.
Examples of the lactone-containing polycyclic group include groups obtained by removing one hydrogen atom from a lactone-containing bicycloalkane having the following structural formula.

In one or both (preferably both) of the structural unit (a2) and the structural unit (a2 ′), the lactone-containing monocyclic or polycyclic group is represented by the following general formula (IV) or (V )
It is preferable that it is at least one selected from.

  More specifically, the structural units (a2) and (a2 ′) are derived from (meth) acrylic acid ester containing a lactone-containing monocycloalkyl group or bicycloalkyl group represented by the following structural formula, for example. Structural units.

（式中、Ｒは上記の場合と同様である。）

(In the formula, R is the same as described above.)

（式中、Ｒは上記の場合と同様である。）

(In the formula, R is the same as described above.)

（式中、Ｒは上記の場合と同様である。）

(In the formula, R is the same as described above.)

  Among these, γ-butyrolactone ester or norbornane lactone ester of (meth) acrylic acid having an ester bond at the α carbon is particularly preferred because it is easily available on the industry.

Since the hydroxyl groups constituting the structural units (a3) and (a3 ′) are polar groups, the use of these increases the hydrophilicity of the whole component (A) with the developer, and increases the alkali solubility in the exposed area. improves. Therefore, the structural units (a3) and (a3 ′) contribute to the improvement of resolution.
In the structural units (a3) and (a3 ′), the polycyclic group is appropriately selected from a large number of polycyclic groups similar to those exemplified in the description of the structural units (a1) and (a1 ′). Can be used.
These structural units (a3) and (a3 ′) are not particularly limited as long as they are a hydroxyl group-containing polycyclic group. Specifically, a hydroxyl group-containing adamantyl group and the like are preferably used.
Furthermore, it is preferable that this hydroxyl group-containing adamantyl group is represented by the following general formula (VI) because it has the effect of increasing dry etching resistance and increasing the perpendicularity of the pattern cross-sectional shape.

  Specifically, it is preferable that one or both (preferably both) of the structural units (a3) and (a3 ′) are structural units represented by the following general formula (VI ′).

（式中、Ｒは上記の場合と同様である。）

(In the formula, R is the same as described above.)

The total of the structural unit (a1) and the structural unit (a1 ′) is 30 to 60 mol%, preferably 30 to 50 mol% with respect to the total of the structural units constituting the component (A). And excellent in resolution.
The total of the structural unit (a2) and the structural unit (a2 ′) is 20 to 60 mol%, preferably 20 to 50 mol%, based on the total of the structural units constituting the component (A). And excellent in resolution.
The total of the structural unit (a3) and the structural unit (a3 ′) is 1 to 50 mol%, preferably 20 to 40 mol%, based on the total of the structural units constituting the component (A). The resist pattern shape is excellent and preferable.

Furthermore, as the copolymer (A1), the following copolymer (a) is excellent in resolution and preferable.
Copolymer (A): A copolymer comprising the structural unit (a1 ′), the structural unit (a2 ′), and the structural unit (a3).
In addition, in this copolymer (a), from the viewpoint of resolution, resist pattern shape, etc., the structural unit (a1 ′) with respect to the total of these structural units (a1 ′), (a2 ′), and (a3). Is 30 to 60 mol%, preferably 30 to 50 mol%, the structural unit (a2 ′) is 20 to 60 mol%, preferably 20 to 50 mol%, and the structural unit (a3) is 1 to 50 mol%, Preferably it is 20-40 mol%.

Further, as the mixed resin (A2), the following copolymers (b)
Copolymer (b): 30-60 mol% of the structural unit (a1), 20-60 mol% of the structural unit (a2) and 1-50 mol% of the structural unit (a3), preferably 5-40 mol % Copolymer.
And the following copolymer (c)
Copolymer (C): 30-60 mol% of the structural unit (a1 ′), 20-60 mol% of the structural unit (a2 ′), and 1-50 mol% of the structural unit (a3 ′), preferably 5 A copolymer consisting of ˜40 mol%.
Is preferable because it can improve the etching resistance (surface roughness) and the resolution in a well-balanced manner.
In this mixed resin, the mass ratio of the copolymer (b) to the copolymer (c) is preferably 80:20 to 20:80.

In the copolymers (b) and (c), whether or not the structural unit (a3) and the structural unit (a3 ′) are blended may be arbitrary.
However, when one or both (preferably both) of the structural unit (a3) and the structural unit (a3 ′) are blended, the hydroxyl group is a polar group as described above. This is preferable because the solubility is increased, the alkali solubility in the exposed area is improved, and the resolution is improved.

  In addition, as the mixed resin (A2), the mixed resin of the copolymer (b) and the copolymer (b) also has a good balance between etching resistance (surface roughness) and resolution. It can improve and is preferable.

In this mixed resin, the mass ratio of the copolymer (A) to the copolymer (B) is preferably 80:20 to 20:80.
In the copolymer (b), whether or not the structural unit (a3) is blended is arbitrary as described above, but when the structural unit (a3) is blended, it contributes to an improvement in resolution. preferable.
Further, as the copolymer (A1), the following copolymer (d) is also preferable because it has excellent resolution and little surface roughness during etching.
Copolymer (d): The above-mentioned constitution (a1 ′) is 30 to 60 mol%, preferably 30 to 50 mol%, the constitutional unit (a2) is 20 to 60 mol%, preferably 20 to 50 mol%, and A copolymer comprising 1 to 50 mol%, preferably 20 to 40 mol% of the structural unit (a3).

  In addition, as described above, the component (A) may further include “the polycyclic group-containing acid dissociable, dissolution inhibiting group, the lactone-containing monocyclic or polycyclic group, the hydroxyl group-containing, as the fourth structural unit. It is preferable that a polycyclic group other than a polycyclic group is included and a structural unit derived from a (meth) acrylic ester [structural unit (a4)].

The meaning of “other than the polycyclic group-containing acid dissociable dissolution inhibiting group, the lactone-containing monocyclic or polycyclic group, the hydroxyl group-containing polycyclic group” means the polycyclic group of the structural unit (a4). The group includes a polycyclic group-containing acid dissociable, dissolution inhibiting group of the first structural unit, a lactone-containing monocyclic or polycyclic group of the second structural unit, and a hydroxyl group-containing polycyclic of the third structural unit. In other words, the structural unit (a4) is a polycyclic group-containing acid dissociable, dissolution inhibiting group of the first structural unit, a lactone-containing monocycle of the second structural unit, or This means that neither the polycyclic group nor the hydroxyl group-containing polycyclic group of the third structural unit is retained.
Such a polycyclic group is not particularly limited as long as it is selected so that it does not overlap with the first to third structural units in one component (A). For example, polycyclic groups similar to those exemplified for the structural units (a1) and (a1) ′ can be used, and many conventionally known ArF positive resist materials can be used. It is.
In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, and a tetracyclododecanyl group is preferable in terms of industrial availability.

As the structural unit (a4), one or both of a unit derived from an acrylate ester and a unit derived from a methacrylic acid ester may be contained in one component (A).
Specifically, it may be a unit constituting the copolymer (A1) as described above, or may be one or more of constituent units of one or more resins constituting the mixed resin (A2). However, it is preferable that it is contained as one unit of a copolymer with the said 1st structural unit thru | or 3rd structural unit from the point of the effect.

  Examples of these structural units (a4) are shown in the following [Chemical Formula 14] to [Chemical Formula 16].

（式中Ｒは水素原子又はメチル基である）

(Wherein R is a hydrogen atom or a methyl group)

（式中Ｒは水素原子又はメチル基である）

(Wherein R is a hydrogen atom or a methyl group)

（式中Ｒは水素原子又はメチル基である）

(Wherein R is a hydrogen atom or a methyl group)

  When the structural unit (a4) is 1 to 25 mol%, preferably 10 to 20 mol%, based on the total of the structural units constituting the component (A), the resolution of the semi-dense pattern from the isolated pattern Excellent and preferable.

When the structural unit (a4) is included, if the copolymer (A1) is the following copolymer (e), in addition to the effects of the above (a4) unit, surface roughness during etching, Since line edge roughness is also improved, it is preferable. .
Copolymer (e): A copolymer comprising the structural unit (a1 ′), the structural unit (a2), the structural unit (a3), and the structural unit (a4).
In addition, in this copolymer (e), from the viewpoint of resolution, resist pattern shape, etc., the structural unit (a1 ′), (a2), (a3), and (a4) are composed of structural units ( a1 ′) is 30 to 60 mol%, preferably 30 to 50 mol%, the structural unit (a2) is 20 to 60 mol%, preferably 20 to 50 mol%, and the structural unit (a3) is 1 to 30 mol%. %, Preferably 10 to 20 mol%, and the structural unit (a4) is 1 to 25 mol%, preferably 10 to 20 mol%.

Moreover, it is preferable from the point which can improve the resolution of an isolated space pattern (trench) that the said mixed resin (A2) is a mixed resin of the said copolymer (d) and a copolymer (e).
In this mixed resin, the mass ratio of the copolymer (d) to the copolymer (e) is preferably 80:20 to 20:80.

In the copolymers (d) and (e), whether or not the structural unit (a3) and the structural unit (a3 ′) are blended may be arbitrary.
However, when one or both (preferably both) of the structural unit (a3) and the structural unit (a3 ′) are blended, the hydroxyl group is a polar group as described above. This is preferable because the solubility is increased, the alkali solubility in the exposed area is improved, and the resolution is improved.

  The weight average molecular weight of the copolymer (A1) constituting the component (A) or the polymer constituting the mixed resin (A2) is not particularly limited, but is preferably 5000 to 30000, more preferably 8000 to 20000. Is done. If it is larger than this range, the solubility in the resist solvent is deteriorated, and if it is smaller, the resist pattern cross-sectional shape may be deteriorated.

  The polymer constituting the copolymer (A1) or the mixed resin (A2) uses a radical polymerization initiator such as azobisisobutyronitrile (AIBN) for the corresponding (meth) acrylic acid ester monomer. It can be easily produced by known radical polymerization or the like.

  Moreover, as an acid generator component (B), arbitrary things can be suitably selected from the well-known things as an acid generator in a conventional chemically amplified resist.

  Examples of the acid generator include diphenyliodonium trifluoromethanesulfonate, (4-methoxyphenyl) phenyliodonium trifluoromethanesulfonate, bis (p-tert-butylphenyl) iodonium trifluoromethanesulfonate, triphenylsulfonium trifluoromethanesulfonate, (4 -Methoxyphenyl) diphenylsulfonium trifluoromethanesulfonate, (4-methylphenyl) diphenylsulfonium nonafluorobutanesulfonate, (p-tert-butylphenyl) diphenylsulfonium trifluoromethanesulfonate, diphenyliodonium nonafluorobutanesulfonate, bis (p-tert- Butylphenyl) iodonium nonafluorobutanesulfonate, And the like onium salts, such as Li-phenyl nonafluorobutanesulfonate. Of these, onium salts having a fluorinated alkyl sulfonate ion as an anion are preferable.

This (B) component may be used independently and may be used in combination of 2 or more type.
The compounding quantity 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 0.5 parts by mass, pattern formation is not sufficiently performed. If the amount exceeds 30 parts by mass, a uniform solution is difficult to obtain, which may cause a decrease in storage stability.

Further, the positive resist composition of the present invention is produced by dissolving the component (A), the component (B), and an optional component (D) described later, preferably in an organic solvent (C).
The organic solvent (C) is not particularly limited as long as it can dissolve the component (A) and the component (B) to form a uniform solution. 1 type or 2 types or more can be appropriately selected and used.
For example, 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, dipropylene glycol, or dipropylene Polyhydric alcohols such as 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, methyl acetate , Ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethoxypropionate Esters such as phosphate ethyl and the like. These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.

In particular, a mixed solvent of propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent having a hydroxy group or lactone such as propylene glycol monomethyl ether (PGME), ethyl lactate (EL), or γ-butyrolactone is a positive resist composition. Is preferable because the storage stability of is improved.
When blending EL, the mass ratio of PGMEA: EL is preferably 6: 4 to 4: 6.
When blending PGME, the mass ratio of PGMEA: PGME is 8: 2 to 2: 8, preferably 8: 2 to 5: 5.
In particular, a mixed solvent of PGMEA and PGME is preferable because the storage stability of the positive resist composition is improved when the component (A) containing all of the first to fourth structural units is used.
In addition, as the organic solvent (C), a mixed solvent of at least one selected from PGMEA and ethyl lactate 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.

Further, in the positive resist composition of the present invention, a secondary lower aliphatic amine or tertiary lower fat is further added as an optional component (D) in order to improve the resist pattern shape, the aging stability and the like. Group amines can be included.
Here, the lower aliphatic amine means an alkyl or alkyl alcohol amine having 5 or less carbon atoms. Examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, di-n-propylamine, Examples include -n-propylamine, triventylamine, diethanolamine, triethanolamine and the like, and alkanolamines such as triethanolamine are particularly preferable.
These may be used alone or in combination of two or more.
These amines are usually used in the range of 0.01 to 0.2% by mass with respect to the component (A).

  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 and the like can be added and contained.

Moreover, the pattern formation method of this invention can be performed as follows, for example.
That is, first, the positive resist composition of the present invention is applied onto a substrate such as a silicon wafer with a spinner or the like, and prebaked at a temperature of 80 to 150 ° C. for 40 to 120 seconds, preferably 60 to 90 seconds. Then, after selectively exposing ArF excimer laser light through a desired mask pattern, for example, with an ArF exposure apparatus or the like, PEB (post-exposure heating) is performed for 40 to 120 seconds under a temperature condition of 80 to 150 ° C. Preferably, it is applied for 60 to 90 seconds. Subsequently, this is developed using an alkali developer, for example, an aqueous solution of 0.1 to 10% by mass of tetramethylammonium hydroxide. 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.

Further, the positive resist composition of the present invention is particularly useful for ArF excimer laser, but shorter wavelength F ₂ laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), electron beam, X-ray, soft It is also effective for radiation such as X-rays.

With such a configuration, in the present invention, a chemically amplified positive resist composition having little surface roughness and line edge roughness during etching, excellent resolution, and a wide focal depth range can be obtained.
The effect is not clear, but is presumed as follows.
That is, it is presumed that a structural unit derived from a methacrylic ester is excellent in lithography properties such as resolution and depth of focus, but tends to have a large surface roughness.
On the other hand, a structural unit derived from an acrylate ester has a great effect of improving surface roughness, but it is presumed that lithography properties such as resolution tend to be insufficient.
In addition, the present inventors found for the first time that the structural unit derived from an acrylate ester will contribute to the improvement of surface roughness, which is an effect that has not been known so far.
Therefore, by using a base resin (component (A)) that combines a structural unit derived from a methacrylic acid ester and a unit derived from an acrylic acid ester, the disadvantages of both are compensated, and the advantages of both are provided. It is thought that it will be obtained.
In addition, in the positive resist composition of the present invention, in addition to the effects considered from the characteristics of these two structural units, a defect reduction effect can be further obtained. Here, the defect means, for example, a scum or a general defect of the resist pattern detected when the surface defect observation apparatus (trade name “KLA”) manufactured by KLA Tencor Co., Ltd. is observed from directly above the resist pattern after development. It is.

  Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 (test example)
Hereinafter, the (A) component, the (B) component, and the (D) component shown in [Chemical Formula 17] were uniformly dissolved in the (C) component to produce a positive resist composition.
Component (A): 50 parts by mass (x = 40 mol%, y = 30 mol%, z = 30 mol) of an acrylic ester copolymer (mass average molecular weight 14000) composed of the following structural units x, y and z %)When,

  50 parts by mass (p = 40 mol%, q = 40 mol%, l = 20 mol%) of a methacrylic acid ester copolymer composed of structural units p, q, and l shown in the following [Chemical Formula 18] (mass) Mixed resin with an average molecular weight of 10,000).

-(B) component: 3 mass parts of triphenylsulfonimnonafluorobutanesulfonate.
Component (C): Mixed solvent of 450 parts by mass of propylene glycol monomethyl ether acetate and 300 parts by mass of ethyl lactate.
-(D) component: 0.2 mass part of triethanolamine.

Subsequently, this positive resist composition was applied onto a silicon wafer using a spinner, pre-baked on a hot plate at 120 ° C. for 90 seconds, and dried to form a resist layer having a thickness of 400 nm.
Subsequently, ArF excimer laser (193 nm) was selectively irradiated through the mask pattern by an ArF exposure apparatus MICRO STEP (NA (numerical aperture) = 0.60, σ = 0.75 manufactured by ISI).
Then, PEB treatment was performed at 110 ° C. for 90 seconds, and further paddle development was performed at 23 ° C. with a 2.38 mass% tetramethylammonium hydroxide aqueous solution for 60 seconds, followed by washing with water for 20 seconds and drying.

As a result, a 130 nm line and space pattern (1: 1) was formed in a good shape, and the depth of focus was 700 nm.
Further, when 3σ, which is a scale indicating the line edge roughness of the line and space pattern, was obtained, it was 6.3 nm.
In addition, 3σ is a triple value of the standard deviation (σ) calculated from the result of measuring the width of the resist pattern of the sample at 32 locations with a side length SEM (trade name “S-9220” manufactured by Hitachi, Ltd.). (3σ). This 3σ means that the smaller the value, the smaller the roughness and the uniform width resist pattern was obtained.
Furthermore, regarding the defect, when the resist hole pattern having a diameter of 250 nm was observed with a surface defect observation apparatus KLA2132 manufactured by KLA Tencor, the number of defects was zero.

Furthermore, in order to evaluate surface roughness after etching, an unpatterned resist film (a positive resist composition applied to a substrate and exposed without passing through a mask pattern) is prepared and etched under the following conditions: did.
Etching condition gas: mixed gas of tetrafluoromethane 30 sccm, trifluoromethane 30 sccm, helium 100 sccm Pressure: 0.3 Torr
RF (Ratio Frequency): Frequency 400kHz-Output 600W
Temperature: 20 ° C
Time: 2 minutes Etching apparatus: TCE-7612X (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.)
Note that the reason why the evaluation was made with the unpatterned resist film is that surface roughness is easier to measure in that case.

  The surface after etching was quantified with an AFM (Atomic Force Microscope), and Rms (root mean square roughness), which is a measure showing surface roughness, was 2.5 nm.

Example 2 (Test example)
(A) Except having changed the component as follows, the positive resist composition was manufactured similarly to Example 1, and pattern formation was performed.
Component (A): In the acrylate copolymer used in Example 1, the structural units y and z were changed to 50 mol% and 20 mol%, respectively, and the structural unit x was changed to the following structural unit m And a polymer (mass average molecular weight 15000) blended with 30 mol%,
The mixed resin with the polymer (mass average molecular weight 10,000) which changed the structural unit q into the structural unit n shown to the following [Chemical Formula 19] in the methacrylic ester copolymer used in Example 1. The proportions of the structural units p, n, and l were the same as the structural units p, q, and l used in Example 1, respectively.

As a result, a 130 nm line and space pattern (1: 1) was formed in a good shape, and the depth of focus was 700 nm. Further, when 3σ was determined, it was 5.8 nm.
Further, when defects were observed in the same manner as in Example 1, the number of defects was zero.
Further, when the surface roughness was evaluated in the same manner as in Example 1, Rms was 2.2 nm.

Example 3 (Test example)
(A) Except having changed the component as follows, the positive resist composition was manufactured similarly to Example 1, and pattern formation was performed.
Component (A): 50 parts by mass of the acrylic ester copolymer (mass average molecular weight 14000) used in Example 1,
Acrylic acid ester / methacrylic acid ester copolymer (in the methacrylic acid ester copolymer used in Example 1, the structural unit 1 is changed to an acrylic acid ester derivative corresponding to the same mol%) (mass average molecular weight) 10000) mixed resin with 50 parts by mass.

As a result, a 130 nm line and space pattern (1: 1) was formed in a good shape, and the depth of focus was 600 nm. Further, when 3σ was determined, it was 5.9 nm.
Further, when defects were observed in the same manner as in Example 1, the number of defects was zero.
Further, when the surface roughness was evaluated in the same manner as in Example 1, Rms was 2.0 nm.

Example 4 (Test Example)
(A) Except having changed the component as follows, the positive resist composition was manufactured similarly to Example 1, and pattern formation was performed.
Component (A): Acrylic acid ester / methacrylic acid ester copolymer (In Example 1, the acrylic acid ester copolymer was not used, and the structural unit 1 in the methacrylic acid ester copolymer used in Example 1 was replaced by (Changed to an acrylate ester corresponding to the same mol%) (mass average molecular weight 10,000) 100 parts by mass.

As a result, a 130 nm line and space pattern (1: 1) was formed in a good shape, and the depth of focus was 800 nm. Further, when 3σ was determined, it was 6.8 nm.
Further, when defects were observed in the same manner as in Example 1, the number of defects was zero.
Further, when the surface roughness was evaluated in the same manner as in Example 1, Rms was 2.5 nm.

Comparative Example 1
(A) Except having changed the component as follows, the positive resist composition was manufactured similarly to Example 1, and pattern formation was performed.
-(A) component: Only 100 mass parts of methacrylate ester copolymers used in Example 1.

As a result, a 130 nm line and space pattern (1: 1) was formed in a good shape, but the depth of focus was 500 nm. Further, when 3σ was determined, it was 14.0 nm.
Further, when defects were observed in the same manner as in Example 1, the number of defects was zero.
Further, when the surface roughness was evaluated in the same manner as in Example 1, Rms was 12.8 nm.

Comparative Example 2
(A) Except having changed the component as follows, the positive resist composition was manufactured similarly to Example 1, and pattern formation was performed.
-(A) component: Only 100 mass parts of acrylic ester copolymers used in Example 1.

As a result, a 130 nm line and space pattern (1: 1) was formed in a good shape, but the depth of focus was 200 nm. Moreover, 3σ was 3.7 nm.
Further, when defects were observed in the same manner as in Example 1, the number of defects was 500.
Further, when the surface roughness was evaluated in the same manner as in Example 1, Rms was 1.1 nm.

From these results, in the examples according to the present invention, the shape of the line and space pattern was good, the depth of focus was large, the line edge roughness was small, and no defects were observed at all.
On the other hand, in Comparative Example 1 using the base resin consisting only of the methacrylic ester constituent unit, the line edge roughness and the surface roughness are large, and the comparison using the base resin consisting only of the acrylic ester constituent unit is performed. In Example 2, the depth of focus range was small, and many defects were observed.

Example 5
The following components (A), (B), (D), and additives were uniformly dissolved in component (C) to produce a positive resist composition.

Component (A): Acrylic acid / methacrylic acid ester copolymer (x = 35 mol%, y = 40 mol%, z =) consisting of structural units x, y, z, and p shown in the following [Chemical Formula 20] 15 mol%, p = 10 mol%) (mass average molecular weight 10,000, dispersity 1.80) 100 parts by mass.

-Component (B): 3.5 parts by mass of triphenylsulfonimnonafluorobutanesulfonate.
-(D) component: 0.3 mass part of triethanolamine.
Additive: 0.1 part by mass of fluorine / silicone surfactant R08 (Dainippon Ink & Chemicals).
Component (C): Mixed solvent of 450 parts by mass of PGMEA, 300 parts by mass of PGMA and 25 parts by mass of γ-butyrolactone.

On the other hand, an organic antireflection film AR-19 (manufactured by Shipley Co., Ltd.) (film thickness: 82 nm) was provided on the silicon wafer, and the positive resist composition was applied onto the silicon wafer using a spinner.
Next, a resist layer having a thickness of 330 nm was formed by drying for 90 seconds on a hot plate under the condition of 95 ° C. (pre-bake).
Furthermore, using ArF exposure apparatus S302 (NA = 0.60 manufactured by Nikon Corporation), ArF excimer laser (193 nm) was selectively irradiated through a mask, then subjected to PEB treatment at 95 ° C. for 90 seconds, and then to 23 ° C. Then, paddle development was carried out with an aqueous 2.38 mass% tetramethylammonium hydroxide solution for 30 seconds, followed by washing with water for 20 seconds and drying.
An isolated line pattern of 100 nm formed by such an operation was formed in a good shape, its sensitivity was 23 mJ / cm ² , and its depth of focus was 450 nm. The limit resolution of the isolated line pattern was 60 nm.
In addition, a 130 nm line and space pattern (a semi-dense pattern in which the total of the resist pattern width and the space pattern width is 340 nm) was formed in a good shape by the same operation, and the depth of focus was 1000 nm.
Further, when 3σ was determined, it was 5.0 nm.

Further, in the same manner as in Example 1, Rms (root mean square surface roughness) was determined for evaluation of surface roughness after etching, and it was 2.5 nm.
Also. The positive resist composition of this example had good foreign matter aging even when stored at room temperature for 60 days.

Example 6
In Example 5, a positive resist composition was produced in the same manner as in Example 5 except that the component (C) was changed to a mixed solvent of 750 parts by mass of PGMEA and 25 parts by mass of γ-butyrolactone.
When pattern formation was performed under the same lithography conditions as in Example 5, the same lithography characteristics as in Example 5 were obtained except that the sensitivity was 22 mJ / cm ² .
The positive resist composition of this example had good foreign matter aging even when stored at room temperature for 30 days.

  From the results of Examples 5 and 6, by using the resin having the fourth structural unit, in addition to the effects such as the above-mentioned surface roughness, the positive resist composition is further excellent in the resolution of isolated patterns and semi-dense patterns. It became clear that things could be obtained.

Example 7 (test example)
The following components (A), (B), (D), and additives were uniformly dissolved in component (C) to produce a positive resist composition.
Component (A): 100 parts by weight (x = 30 mol%, y) of acrylic acid / methacrylic acid ester copolymer (mass average molecular weight 11000, dispersity 1.9) represented by the following structural formula = 50 mol%, z = 20 mol%).

Component (B): (p-methylphenyl) diphenylsulfonimnonafluorobutanesulfonate 3.5 parts by weight
Component (C): Mixed solvent of 450 parts by weight of propylene glycol monomethyl ether acetate (PGMEA), 300 parts by weight of propylene glycol monomethyl ether (PGME) and 25 parts by weight of γ-butyrolactone.
-(D) component: Triethanolamine 0.3 weight part.
Additive: 0.1 part by weight of fluorine / silicone surfactant R08 (manufactured by Dainippon Ink & Chemicals, Inc.)

Next, an organic antireflection film AR-19 (manufactured by Shipley) is provided on the silicon wafer with a film thickness of 82 nm, and the resist solution is applied onto the silicon wafer using a spinner on the antireflection film, A resist layer having a thickness of 340 nm was formed by drying at 105 ° C. (pre-bake) for 90 seconds.
Next, ArF excimer laser (193 nm) was selectively irradiated through the mask with an ArF exposure apparatus NSR-S302 (NA = 0.60 manufactured by Nikon), and then subjected to PEB treatment at 100 ° C. for 90 seconds, and then 23 ° C. Paddle development with 2.38 wt% tetramethylammonium hydroxide aqueous solution for 30 seconds, followed by washing with water for 20 seconds and drying.
As a result, a 130 nm line and space pattern (1: 1) was formed in a good shape, and the depth of focus was 800 nm.
Further, when 3σ, which is a scale indicating the LER of the line and space pattern, was obtained, it was 6.0 nm.
Further, in the same manner as in Example 1, Rms (root mean square surface roughness) was determined for evaluation of surface roughness after etching, and it was 2.5 nm.
Further, the resist solution had good foreign matter aging even when stored at room temperature for 30 days.

Example 8
In Example 7, 50 parts by weight of the quaternary acrylic acid / methacrylic acid ester copolymer used in Example 5 was used instead of 50 parts by weight of the acrylic acid / methacrylic acid ester copolymer used in Example 7. Then, a positive resist composition was produced in the same manner as in Example 7 except that the component (A) was used, and a pattern was formed in the same manner as in Example 7.
As a result, an isolated line pattern of 100 nm formed by such an operation was formed in a good shape, its sensitivity was 23 mJ / cm 2, and its depth of focus was 450 nm. The limit resolution of the isolated line pattern was 75 nm.
Further, a 130 nm line and space pattern (a semi-dense pattern in which the total of the resist pattern width and the space pattern width is 340 nm) was formed in a good shape by the same operation, and the depth of focus was 1000 nm.
Further, 3σ, which is a scale indicating the LER of the line and space pattern, was found to be 5.3 nm.
Further, in the same manner as in Example 1, Rms (root mean square surface roughness) was determined for evaluation of surface roughness after etching, and it was 2.5 nm.
Further, the resist solution had good foreign matter aging even when stored at room temperature for 30 days.

From the results of Examples 7 and 8, in Example 7 using a resin having three structural units, an effect such as reduction in surface roughness was obtained, and an example using a resin having a fourth structural unit. In No. 8, in addition to the effects such as surface roughness described above, a positive resist composition having an excellent resolution of isolated patterns and semi-dense patterns was obtained. In Examples 7 and 8, since a mixed solvent of PGMEA and a polar solvent was used, the temporal stability was good.

Claims (23)

Resin component that has a polycyclic group-containing acid dissociable, dissolution inhibiting group in the ester side chain and has a structural unit derived from (meth) acrylic acid ester in the main chain, which increases alkali solubility by the action of acid. A positive resist composition comprising (A), an acid generator component (B) that generates an acid upon exposure, and an organic solvent (C),
The component (A) has both a structural unit derived from a methacrylic acid ester and a structural unit derived from an acrylate ester,
The component (A) is
A structural unit containing a polycyclic group-containing acid dissociable, dissolution inhibiting group and derived from a (meth) acrylic acid ester,
A structural unit containing a lactone-containing monocyclic or polycyclic group and derived from a (meth) acrylic ester, and
Containing a hydroxyl group-containing polycyclic group and having a structural unit derived from a (meth) acrylic acid ester, and
The component (A) is
And a polycyclic group other than the polycyclic group-containing acid dissociable dissolution inhibiting group, the lactone-containing monocyclic or polycyclic group, the hydroxyl group-containing polycyclic group, and a (meth) acrylic acid ester. A positive resist composition comprising a derived structural unit (a4).   The positive resist composition according to claim 1, wherein the component (A) includes a copolymer (A1) having a structural unit derived from a methacrylic acid ester and a structural unit derived from an acrylate ester. .   The component (A) includes a mixed resin (A2) of a polymer having a unit derived from at least a methacrylic ester and a polymer having a unit derived from at least an acrylate ester. A positive resist composition. The component (A) is
A structural unit (a1) containing a polycyclic group-containing acid dissociable, dissolution inhibiting group and derived from an acrylate ester;
4. The positive electrode according to claim 1, comprising a polycyclic group-containing acid dissociable, dissolution inhibiting group and having one or both of the structural units (a1 ′) derived from a methacrylic acid ester. 5. Type resist composition. The component (A) is
A structural unit (a2) containing a lactone-containing monocyclic or polycyclic group and derived from an acrylate ester;
The positive resist according to any one of claims 1 to 4, comprising a lactone-containing monocyclic or polycyclic group and having one or both of the structural units (a2 ') derived from a methacrylic acid ester. Composition. The component (A) is
A structural unit (a3) containing a hydroxyl group-containing polycyclic group and derived from an acrylate ester;
The positive resist composition according to any one of claims 1 to 5, which comprises one or both of a structural unit (a3 ′) containing a hydroxyl group-containing polycyclic group and derived from a methacrylic acid ester. In one or both of the structural unit (a1) and the structural unit (a1 ′),
The polycyclic group-containing acid dissociable, dissolution inhibiting group is at least one selected from the following general formula (I), (II), or (III): The positive resist composition as described.

(In the formula, R ¹ is a lower alkyl group.)

(In the formula, R ² and R ³ are each independently a lower alkyl group.)

(In the formula, R ⁴ is a tertiary alkyl group.) In one or both of the structural unit (a2) and the structural unit (a2 ′),
The positive resist composition according to claim 5, wherein the lactone-containing monocyclic or polycyclic group is at least one selected from the following general formula (IV) or (V). Stuff.

In one or both of the structural unit (a3) and the structural unit (a3 ′),
The positive resist composition according to claim 6, wherein the hydroxyl group-containing polycyclic group is a hydroxyl group-containing adamantyl group. The positive resist composition according to claim 9, wherein the hydroxyl group-containing adamantyl group is represented by the following general formula (VI).

In the positive resist composition according to any one of claims 4 to 10,
A positive resist composition, wherein the total of the structural unit (a1) and the structural unit (a1 ′) is 30 to 60 mol% with respect to the total of the structural units constituting the component (A). In the positive resist composition according to any one of claims 5 to 11,
A positive resist composition, wherein the total of the structural unit (a2) and the structural unit (a2 ′) is 20 to 60 mol% with respect to the total of the structural units constituting the component (A). In the positive resist composition according to any one of claims 6 to 12,
The positive resist composition, wherein the total of the structural unit (a3) and the structural unit (a3 ′) is 1 to 50 mol% with respect to the total of the structural units constituting the component (A). The positive resist composition according to any one of claims 6 to 13, wherein the copolymer (A1) is a copolymer (d) below.
Copolymer (d): A copolymer comprising 30 to 60 mol% of the structural unit (a1 ′), 20 to 60 mol% of the structural unit (a2), and 1 to 50 mol% of the structural unit (a3).
A positive resist composition.   The polycyclic group contained in the structural unit (a4) is at least one selected from a tricyclodecanyl group, an adamantyl group, and a tetracyclododecanyl group. The positive resist composition according to one item.   The positive resist according to claim 1, wherein the proportion of the structural unit (a4) is 1 to 25 mol% with respect to the total of the structural units constituting the component (A). Composition. In the positive resist composition according to any one of claims 6 to 16,
The copolymer (A1) is the following copolymer (e)
Copolymer (e): 30-60 mol% of the structural unit (a1 ′), 20-60 mol% of the structural unit (a2), 1-30 mol% of the structural unit (a3), and structural unit (a4) A copolymer comprising 1 to 25 mol%.
A positive resist composition. In the positive resist composition according to any one of claims 6 to 17,
A positive resist composition, wherein the mixed resin (A2) is a mixed resin of the copolymer (d) according to claim 14 and the copolymer (e) according to claim 17.   The positive resist composition according to claim 1, wherein the component (B) is an onium salt having a fluorinated alkyl sulfonate ion as an anion.   The positive resist composition according to claim 1, wherein the organic solvent (C) is a mixed solvent of propylene glycol monomethyl ether acetate and a polar solvent.   21. The positive resist composition according to claim 20, wherein the polar solvent is one or more selected from propylene glycol monomethyl ether, ethyl lactate, and [gamma] -butyrolactone.   The positive resist composition according to any one of claims 1 to 21, wherein a secondary or tertiary lower aliphatic amine (D) is further added in an amount of 0.01 to 0.00 with respect to the component (A). A positive resist composition containing 2% by mass. The positive resist composition according to any one of claims 1 to 22 is applied on a substrate, pre-baked, selectively exposed, subjected to PEB (post-exposure heating), and alkali-developed. And forming a resist pattern.