JP2006162796A - Positive resist composition and method for forming resist pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive resist composition excellent in dimension controlling property and to provide a method for forming a resist pattern. <P>SOLUTION: The positive resist composition contains: a resin component (A) which has a structural unit (a11) derived from (α-methyl)hydroxyl styrene, a structural unit (a12) derived from a (α-lower alkyl) acrylic acid ester having an alcoholic hydroxyl group, and a structural unit (a21) derived by substituting an acid-dissociable dissolution inhibiting group for a hydrogen atom of the hydroxyl group in the structural unit (a11), and/or a structural unit (a22) derived by substituting an acid-dissociable dissolution inhibiting group for a hydrogen atom of the alcoholic hydroxyl group in the structural unit (a12), and which has an acid-dissociable dissolution inhibiting group containing an acid-dissociable dissolution inhibiting group (II) expressed by general formula (II) and a specified chain acid-dissociable dissolution inhibiting group (III); and an acid generator component (B) which generates acid by exposure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

In the photolithography technique, for example, a resist film made of a resist composition is formed on a substrate, and the resist film is irradiated with radiation such as light or an electron beam through a photomask in which a predetermined pattern is formed. A step of forming a resist pattern having a predetermined shape on the resist film is performed by performing selective exposure and developing. A resist composition in which the exposed portion changes to a property that dissolves in the developer is referred to as a positive type, and a resist composition that changes to a property in which the exposed portion does not dissolve in the developer is referred to as a negative type.
In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, miniaturization has rapidly progressed due to advances in lithography technology. As a means for miniaturization, the wavelength of exposure light is generally shortened. Specifically, conventionally, ultraviolet rays typified by g-line and i-line have been used, but now KrF is used. Excimer laser (248 nm) has been introduced, and ArF excimer laser (193 nm) has begun to be introduced. In addition, studies have been conducted on shorter wavelength F ₂ excimer lasers (157 nm), EUV (extreme ultraviolet rays), electron beams, X-rays, and the like. The exposure with an electron beam or EUV is usually performed by exposure through a desired mask pattern or direct drawing in a vacuum.

Further, in order to reproduce a pattern with a fine dimension, a resist material having high resolution is required. As such a resist material, a chemically amplified resist composition containing a base resin and an acid generator that generates an acid upon exposure is used. For example, a positive chemically amplified resist contains a resin component whose alkali solubility is increased by the action of an acid and an acid generator component that generates an acid upon exposure. When acid is generated from the above, the exposed part becomes alkali-soluble.
As a resin component of a positive resist composition, a resin in which a part of hydroxyl groups of a polyhydroxystyrene resin is generally protected with an acid dissociable, dissolution inhibiting group, or a part of carboxy groups in an acrylic resin is acid dissociated. Resins protected with a soluble dissolution inhibiting group are used. Examples of the acid dissociable, dissolution inhibiting group include so-called acetal groups such as chain ether groups typified by 1-ethoxyethyl groups or cyclic ether groups typified by tetrahydropyranyl groups, and tert-butyl groups. Tertiary alkyl groups, tertiary alkoxycarbonyl groups represented by tert-butoxycarbonyl groups, and the like are mainly used (see, for example, Patent Document 1).
JP 2002-341538 A

  However, when the resist material as described above is used, the target pattern can be obtained within the same substrate surface even under the same exposure conditions, particularly when exposure in vacuum, for example, direct drawing of electron beams is performed. There is a problem that the difference between the dimension and the pattern dimension to be formed is large and the dimensional controllability is poor.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a positive resist composition and a resist pattern forming method excellent in dimensional controllability.

The first aspect of the present invention that solves the above-mentioned problems includes an alkali-soluble structural unit (a1) and a structural unit (a2) having an acid dissociable, dissolution inhibiting group, and increases alkali solubility by the action of an acid. A positive resist composition comprising a resin component (A) to be generated and an acid generator component (B) that generates an acid upon exposure,
The structural unit (a1) is a structural unit (a11) derived from (α-methyl) hydroxystyrene, and a structural unit (a12) derived from an (α-lower alkyl) acrylic acid ester having an alcoholic hydroxyl group; Have
In the structural unit (a2), the hydrogen atom of the hydroxyl group of the structural unit (a11) is substituted with an acid dissociable, dissolution inhibiting group, and / or the alcoholic hydroxyl group of the structural unit (a12). It has a structural unit (a22) in which a hydrogen atom is substituted with an acid dissociable, dissolution inhibiting group, and the acid dissociable, dissolution inhibiting group has the following general formula (II)

［式中、Ｘは脂肪族環式基、芳香族環式炭化水素基または炭素数１〜５のアルキル基を表し、Ｒ^１は炭素数１〜５のアルキル基を表し、もしくはＸおよびＲ^１がそれぞれ独立に炭素数１〜５のアルキレン基であってＸの末端とＲ^１の末端とが結合していてもよく、Ｒ^２は炭素数１〜５のアルキル基または水素原子を表す。］
で表される酸解離性溶解抑制基（ＩＩ）と、鎖状第３級アルコキシカルボニル基、鎖状第３級アルキル基、および鎖状第３級アルコキシカルボニルアルキル基からなる群から選択される少なくとも１種である酸解離性溶解抑制基（ＩＩＩ）とを含むことを特徴とするポジ型レジスト組成物である。

[Wherein, X represents an aliphatic cyclic group, an aromatic cyclic hydrocarbon group, or an alkyl group having 1 to 5 carbon atoms, R ¹ represents an alkyl group having 1 to 5 carbon atoms, or X and R ¹ Each independently represents an alkylene group having 1 to 5 carbon atoms, and the end of X and the end of R ¹ may be bonded to each other, and R ² represents an alkyl group having 1 to 5 carbon atoms or a hydrogen atom. ]
At least selected from the group consisting of an acid dissociable, dissolution inhibiting group (II) represented by: a chain tertiary alkoxycarbonyl group, a chain tertiary alkyl group, and a chain tertiary alkoxycarbonylalkyl group A positive resist composition comprising an acid dissociable, dissolution inhibiting group (III) as one type.

  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 selectively exposing the resist film, This is a resist pattern forming method including a step of forming a resist pattern by alkali development.

In the present specification and claims, the “constituent unit” means a monomer unit constituting the polymer.
“Exposure” is a concept that includes general irradiation of radiation, and includes irradiation of an electron beam.

  According to the present invention, a positive resist composition and a resist pattern forming method excellent in dimensional controllability can be provided.

<Positive resist composition>
The positive resist composition of the present invention comprises an alkali-soluble constituent unit (a1) and a constituent unit (a2) having an acid dissociable, dissolution inhibiting group, and a resin component (in which alkali solubility is increased by the action of an acid ( A) (hereinafter also referred to as component (A)) and an acid generator component (B) that generates acid upon exposure (hereinafter also referred to as component (B)).
In the component (A), when an acid generated from the component (B) acts upon exposure, the acid dissociable, dissolution inhibiting group is dissociated, thereby changing the entire component (A) from alkali-insoluble to alkali-soluble.
Therefore, when the resist pattern is selectively exposed through or not through the mask pattern, or when post-exposure heating (PEB) is performed in addition to the exposure, the exposed portion turns into alkali-soluble while the unexposed portion becomes Since it remains insoluble in alkali and does not change, a positive resist pattern can be formed by alkali development.

[(A) component]
・ Structural unit (a1)
In the component (A), the alkali-soluble structural unit (a1) is a polar group such as a hydroxyl group or a carboxy group in the structural unit, and the monomer for deriving the structural unit becomes an alkali such as an alkali developer. A structural unit that is soluble.
In the present invention, the structural unit (a1) needs to have the following structural unit (a11) and structural unit (a12).

The structural unit (a11) is a structural unit derived from (α-methyl) hydroxystyrene.
Here, (α-methyl) hydroxystyrene means one or both of hydroxystyrene and α-methylhydroxystyrene. “Α-methylhydroxystyrene” means a hydrogen atom bonded to an α carbon atom of hydroxystyrene substituted with a methyl group. The “structural unit derived from (α-methyl) styrene” means a structural unit formed by cleavage of an ethylenic double bond of (α-methyl) styrene.
Examples of the structural unit (a11) include structural units represented by the following general formula (I).

［式中、Ｒは水素原子又はメチル基であり、ｍは１〜３の整数である。］

[In formula, R is a hydrogen atom or a methyl group, and m is an integer of 1-3. ]

In general formula (I), R is a hydrogen atom or a methyl group, and is preferably a hydrogen atom.
m is an integer of 1 to 3, and preferably 1.
When m is 1, the position of the hydroxyl group may be any of the o-position, m-position, and p-position, but the p-position is preferred because it is readily available and inexpensive. Furthermore, when m is 2 or 3, arbitrary substitution positions can be combined.

The structural unit (a12) is a structural unit derived from an (α-lower alkyl) acrylate ester having an alcoholic hydroxyl group.
Such a structural unit (a12) has lower solubility in an alkaline developer than the structural unit (a11). Therefore, the solubility of the component (A) in the alkali developer in the state where the acid dissociable, dissolution inhibiting group is dissociated is lower than when the component (A) has only the structural unit (a11) as the structural unit (a1). Become. For this reason, sufficient insolubility with respect to an alkaline developer is obtained even if the proportion of the structural unit (a2) having an acid dissociable, dissolution inhibiting group is smaller than when the structural unit (a1) has only the structural unit (a11). And film loss after development can be reduced.
Therefore, the structural unit (a12) is not limited as long as it has such an action, as long as it is a structural unit derived from an (α-lower alkyl) acrylate ester having an alcoholic hydroxyl group.

  Here, “(α-lower alkyl) acrylic acid ester” means one or both of α-lower alkyl acrylic acid ester such as methacrylic acid ester and acrylic acid ester. The “α-lower alkyl acrylate ester” means that a hydrogen atom bonded to the α carbon atom of the acrylate ester is substituted with a lower alkyl group. 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 bonded to the α carbon atom of the α-lower alkyl acrylate ester is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, such as a methyl group, an ethyl group, a propyl group, or an isopropyl group. , N-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. Industrially, a methyl group is preferable.

The structural unit (a12) is preferably a structural unit derived from an aliphatic polycyclic group-containing (α-lower alkyl) acrylate ester having an alcoholic hydroxyl group. Since such a structural unit contains an aliphatic polycyclic group, improvement in etching resistance and reduction in film loss after etching are expected. Also, the resolution is excellent. “Aliphatic” means a group, compound, or the like that does not have aromaticity, as will be described later.
Examples of the polycyclic group constituting the aliphatic polycyclic group having an alcoholic hydroxyl group include groups in which one hydrogen atom has been removed from bicycloalkane, tricycloalkane, tetracycloalkane, and the like. Specific examples include groups in which one hydrogen atom has been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Such a polycyclic group can be appropriately selected and used from among many proposed ArF resists and the like. Of these, an adamantyl group, a norbornyl group, and a tetracyclododecanyl group are industrially preferable.

The structural unit (a12) is particularly preferably a structural unit derived from an adamantyl group-containing (α-lower alkyl) acrylate ester having an alcoholic hydroxyl group, as represented by the following general formula (IV).
As the structural unit represented by the general formula (IV), the structural unit represented by the following general formula (IVa) is most preferable.

［式中、Ｒは水素原子又は低級アルキル基であり、ｘは１〜３の整数である。］

[Wherein, R is a hydrogen atom or a lower alkyl group, and x is an integer of 1 to 3. ]

  In the present invention, the structural unit (a1) may have a structural unit other than the structural unit (a11) and the structural unit (a12). Examples of the structural unit include a structural unit derived from (meth) acrylic acid. “(Meth) acrylic acid” means one or both of methacrylic acid and acrylic acid. Further, the “structural unit derived from (meth) acrylic acid” means a structural unit constituted by cleavage of an ethylenic double bond of (meth) acrylic acid.

  In the component (A), the proportion of the structural unit (a1) is preferably 50 to 95 mol%, more preferably 60 to 85 mol%, based on all the structural units constituting the component (A). . Thereby, moderate alkali solubility is obtained.

・ Structural unit (a2)
The structural unit (a2) is a structural unit having an acid dissociable, dissolution inhibiting group.
In the present invention, it is necessary to have an acid dissociable, dissolution inhibiting group (II) and an acid dissociable, dissolution inhibiting group (III) as acid dissociable, dissolution inhibiting groups.

The acid dissociable, dissolution inhibiting group (II) is a group represented by the above general formula (II).
In formula (II), X represents an aliphatic cyclic group, an aromatic cyclic hydrocarbon group, or an alkyl group having 1 to 5 carbon atoms.
Here, “aliphatic” is a relative concept with respect to aromatics, and is defined to mean groups, compounds, and the like that do not have aromaticity. “Aliphatic cyclic group” means a monocyclic group or a polycyclic group having no aromaticity. In this case, “aliphatic cyclic group” means a group consisting of carbon and hydrogen (carbonized). Although it is not limited to being a hydrogen group, it is preferably a hydrocarbon group. The “hydrocarbon group” may be either saturated or unsaturated, but is usually preferably saturated. A polycyclic group is preferred.
Such an aliphatic cyclic group can be used, for example, by appropriately selecting from a large number of proposals in conventional ArF resists. Specific examples of the aliphatic cyclic group include an aliphatic monocyclic group having 5 to 7 carbon atoms and an aliphatic polycyclic group having 10 to 16 carbon atoms. Examples of the aliphatic monocyclic group having 5 to 7 carbon atoms include groups in which one hydrogen atom has been removed from a monocycloalkane. Specifically, one hydrogen atom has been removed from cyclopentane, cyclohexane and the like. Group. Examples of the aliphatic polycyclic group having 10 to 16 carbon atoms include groups in which one hydrogen atom has been removed from bicycloalkane, tricycloalkane, tetracycloalkane and the like. Specifically, adamantane, norbornane, Examples include groups in which one hydrogen atom has been removed from a polycycloalkane such as isobornane, tricyclodecane, and tetracyclododecane. Among these, an adamantyl group, a norbornyl group, and a tetracyclododecanyl group are industrially preferable, and an adamantyl group is particularly preferable.
Examples of the aromatic cyclic hydrocarbon group for X include aromatic polycyclic groups having 10 to 16 carbon atoms. Specific examples include groups in which one hydrogen atom has been removed from naphthalene, anthracene, phenanthrene, pyrene, and the like. Specific examples include 1-naphthyl group, 2-naphthyl group, 1-anthracenyl group, 2-anthracenyl group, 1-phenanthryl group, 2-phenanthryl group, 3-phenanthryl group, 1-pyrenyl group, and the like. A naphthyl group is particularly preferred industrially.
The alkyl group of X may be linear or branched. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. Industrially, a methyl group or an ethyl group is preferable, and a methyl group is particularly preferable.
X is preferably an aliphatic polycyclic group. When X is an aliphatic polycyclic group, the line edge roughness of the resist pattern and the rectangular shape of the cross-sectional shape are improved. Moreover, etching resistance is also improved.
Moreover, when a structural unit (a2) contains the structural unit (a22) mentioned later, it is preferable that X is a C1-C5 alkyl group at the point of the ease of a synthesis | combination.

In the formula (II), R ¹ represents an alkyl group having 1 to 5 carbon atoms, and may be linear or branched. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. Industrially, a methyl group or an ethyl group is preferable, and a methyl group is particularly preferable.
R ² represents an alkyl group having 1 to 5 carbon atoms or a hydrogen atom. Examples of the alkyl group include those similar to the alkyl group for R ¹ . R ² is preferably a hydrogen atom industrially.

In Formula (II), X and R ¹ may each independently be an alkylene group having 1 to 5 carbon atoms, and the end of X and the end of R ¹ may be bonded.
In this case, in the formula (II), a cyclic group is formed by R ¹ , X, the oxygen atom to which X is bonded, and the carbon atom to which the oxygen atom and R ¹ are bonded. The cyclic group is preferably a 4- to 7-membered ring, and more preferably a 4- to 6-membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

  As the acid dissociable, dissolution inhibiting group (II), in particular, the acid dissociable, dissolution inhibiting group represented by the following general formula (II-1) is excellent in the effect of the present invention and is preferable.

［式中、Ｙは脂肪族環式基、芳香族環式炭化水素基、または炭素数１〜５のアルキル基を表し、Ｒ^１は炭素数１〜５のアルキル基を表す。］

[Wherein, Y represents an aliphatic cyclic group, an aromatic cyclic hydrocarbon group, or an alkyl group having 1 to 5 carbon atoms, and R ¹ represents an alkyl group having 1 to 5 carbon atoms. ]

Alkyl group of 1 to 5 carbon atoms for R ¹ is the same as ^{R 1} in the general formula (II).
In addition, as the aliphatic cyclic group, aromatic cyclic hydrocarbon group or alkyl group having 1 to 5 carbon atoms of Y, the aliphatic cyclic group or aromatic cyclic hydrocarbon of X in the above general formula (II) It is the same as the group or the alkyl group having 1 to 5 carbon atoms.

Specific examples of the acid dissociable, dissolution inhibiting group represented by formula (II-1) include, for example, when Y is a group that is an alkyl group, that is, a 1-alkoxyalkyl group, a 1-methoxyethyl group, 1- Ethoxyethyl group, 1-iso-propoxyethyl group, 1-n-butoxyethyl group, 1-tert-butoxyethyl group, methoxymethyl group, ethoxymethyl group, iso-propoxymethyl group, n-butoxymethyl group, tert- Examples include butoxymethyl group. Examples of the group in which Y is an aliphatic cyclic group include 1-cyclohexyloxyethyl group, 1- (2-adamantyl) oxymethyl group, and 1- (1-adamantyl) represented by the following formula (II-a). ) An oxyethyl group. Examples of the group in which Y is an aromatic cyclic hydrocarbon group include a 1- (2-naphthyl) oxyethyl group represented by the following formula (II-b).
Among these, a 1-ethoxyethyl group or a 1- (1-adamantyl) oxyethyl group is particularly preferable.

The acid dissociable, dissolution inhibiting group (III) is at least one selected from the group consisting of a chain tertiary alkoxycarbonyl group, a chain tertiary alkyl group, and a chain tertiary alkoxycarbonylalkyl group. .
The chain tertiary alkoxy group and / or chain tertiary alkyl group contained in the acid dissociable, dissolution inhibiting group (III) preferably has 4 to 10 carbon atoms, and more preferably 4 to 8 carbon atoms. Moreover, as the total carbon number of acid dissociable, dissolution inhibiting group (III), 4-10 are preferable and 4-8 are more preferable.
Examples of the chain tertiary alkoxycarbonyl group include a tert-butoxycarbonyl group and a tert-amyloxycarbonyl group.
Examples of the chain tertiary alkyl group include a tert-butyl group and a tert-amyl group.
Examples of the chain-like tertiary alkoxycarbonylalkyl group include a tert-butoxycarbonylmethyl group and a tert-amyloxycarbonylmethyl group.
Among these, a chain-like tertiary alkoxycarbonyl group is preferable, and among them, a tert-butoxycarbonyl group is most preferable because the resist pattern shape is good.

Moreover, the structural unit (a2) may have a structural unit having an acid dissociable, dissolution inhibiting group other than the acid dissociable, dissolution inhibiting groups (II) and (III) as necessary.
As acid dissociable, dissolution inhibiting groups other than acid dissociable, dissolution inhibiting groups (II) and (III), conventionally known acid dissociable, dissolution inhibiting groups can be used. As the conventionally known acid dissociable dissolution inhibiting groups, those proposed as acid dissociable dissolution inhibiting groups in chemically amplified KrF positive resist compositions and ArF positive resist compositions may be appropriately used. On the ring, such as 1-methylcyclopentyl group, 1-ethylcyclopentyl group, 1-methylcyclohexyl group, 1-ethylcyclohexyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, etc. And monocyclic or polycyclic aliphatic hydrocarbon groups containing a tertiary carbon atom.

  Examples of the structural unit (a2) include the structural unit (a21) in which the hydrogen atom of the hydroxyl group of the structural unit (a11) is substituted with an acid dissociable, dissolution inhibiting group, and the alcoholic hydroxyl group of the structural unit (a12). Structural unit (a22) in which a hydrogen atom is substituted with an acid dissociable, dissolution inhibiting group, and a structural unit in which a hydrogen atom of a carboxy group in a structural unit derived from (meth) acrylic acid is substituted with an acid dissociable, dissolution inhibiting group Examples include units. Among these, it is preferable to have the structural unit (a21) and / or the structural unit (a22).

  In the component (A), the proportion of the structural unit (a2) is preferably from 5 to 45 mol%, more preferably from 10 to 45 mol%, based on all the structural units constituting the component (A). 40 mol% is more preferable. Thereby, it is possible to sufficiently ensure alkali insolubility in the unexposed portion of the resist film when forming the resist pattern.

  In addition, in the component (A), the total of the structural unit (a11) and the structural unit (a21) (hydroxystyrene-based structural unit) and the total of the structural unit (a12) and the structural unit (a22) ((α-lower alkyl) The ratio (molar ratio) to (acrylic ester structural unit) is preferably in the range of 95: 5 to 50:50, more preferably in the range of 95: 5 to 60:40. 85:15 to 70:30 is more preferable, but more preferable. By being within the above range, sufficient solubility in a developer can be secured.

In addition to the structural units (a1) and (a2), the component (A) may further have a structural unit (a3) derived from (α-methyl) styrene.
In the present invention, the structural unit (a3) is not essential, but if it is contained, advantages such as an improved depth of focus and improved dry etching resistance can be obtained.

  Here, “(α-methyl) styrene” means one or both of styrene and α-methylstyrene. “Α-methylstyrene” means that a hydrogen atom bonded to the α carbon atom of styrene is substituted with a methyl group. The “structural unit derived from (α-methyl) styrene” means a structural unit formed by cleavage of an ethylenic double bond of (α-methyl) styrene. In (α-methyl) styrene, the hydrogen atom of the phenyl group may be substituted with a substituent such as an alkyl group having 1 to 5 carbon atoms.

  Examples of the structural unit (a3) include structural units represented by the following general formula (III).

［式中、Ｒは水素原子またはメチル基を表し、Ｒ^３は炭素数１〜５のアルキル基を表し、ｎは０または１〜３の整数を表す。］

[Wherein, R represents a hydrogen atom or a methyl group, R ³ represents an alkyl group having 1 to 5 carbon atoms, and n represents an integer of 0 or 1 to 3. ]

In Formula (III), R ³ is a linear or branched alkyl group having 1 to 5 carbon atoms, and is 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. Industrially, a methyl group or an ethyl group is preferable.
n is 0 or an integer of 1 to 3. Of these, n is preferably 0 or 1, and is particularly preferably 0 industrially.
In addition, when n is 1 to ³ , the substitution position of R ³ may be any of the o-position, m-position and p-position, and when n is 2 or 3, any substitution The positions can be combined.

  When the component (A) has the structural unit (a3), the proportion of the structural unit (a3) is preferably 0.5 to 25 mol%, preferably 3 to 20 mol, based on all the structural units constituting the component (A). If the structural unit (a3) in which% is more preferable is more than the above range, the solubility in the developer tends to deteriorate.

The weight average molecular weight of component (A) (polystyrene conversion by gel permeation chromatography (GPC), the same shall apply hereinafter) is preferably from 3500 to 33000, more preferably from 5500 to 23000.
By setting the mass average molecular weight to 33000 or less, sufficient solubility in the resist solvent can be secured, and by setting it to 3500 or more, the dry etching resistance of the resulting resist pattern is improved and film loss is improved. Further, within the above range, the film loss after etching is reduced as the mass average molecular weight is larger.
Further, the smaller the degree of dispersion (Mw / Mn (number average molecular weight)) of the component (A), the better the resolution, and the better. The dispersity is preferably 2.0 or less, and more preferably 1.7 or less.

In the present invention, the component (A) is a copolymer (hereinafter referred to as the structural unit (a11), the structural unit (a12), the structural unit (a21) and / or the structural unit (a22). And a copolymer (A-1)). Thereby, good resolution is obtained and development defects are reduced. Also, a good depth of focus can be obtained.
The copolymer (A-1) may further have the structural unit (a3).

For example, the copolymer (A-1) is obtained by polymerizing a monomer corresponding to the structural unit (a11) and a monomer corresponding to the structural unit (a12), and then hydroxyl groups of the structural unit (a11) and the structural unit (a12). Can be produced by a method of substituting a part of the hydrogen atoms with an acid dissociable, dissolution inhibiting group into a structural unit (a21) and / or a structural unit (a22) by a known method.
Alternatively, a monomer corresponding to the structural unit (a21) and a monomer corresponding to the structural unit (a22) are prepared, and after these monomers are polymerized by a conventional method, the acid dissociable, dissolution inhibiting group is dissociated by hydrolysis. To the structural unit (a11) and the structural unit (a12), and if necessary, the hydrogen atom of the hydroxyl group of the structural unit (a11) and / or the structural unit (a12) may be replaced with an acid dissociable, dissolution inhibiting group by a known method. It can also be produced by a method of substituting the structural unit (a21) and / or the structural unit (a22).

  In the present invention, in particular, the component (A) has the structural unit (a1) and the structural unit (a2), and the acid dissociable dissolution inhibiting group (II) is used as the acid dissociable dissolution inhibiting group. A polymer (A1) having the acid dissociable, dissolution inhibiting group (III), the structural unit (a1) and the structural unit (a2), and having an acid dissociable, dissolution inhibiting group It is preferable to contain the polymer (A2) having the acid dissociable, dissolution inhibiting group (III) and not having the acid dissociable, dissolution inhibiting group (II). By using such a mixture as the component (A), it is possible to obtain an excellent isolated line pattern having a good resist pattern shape and a rectangular shape. In addition, it is easier to contain the acid dissociable, dissolution inhibiting group (II) and the acid dissociable, dissolution inhibiting group (III) in different polymers and use them as a mixed resin, than in the same polymer. Can be prepared.

In the present invention, it is particularly preferable that the component (A) is such that the polymer (A1) is the following polymer (A12) and the polymer (A2) is the following polymer (A21).
Polymer (A12): the structural unit (a11), the structural unit (a12), the structural unit (a21) and / or the structural unit (a22), and an acid dissociable, dissolution inhibiting group Polymer having acid dissociable, dissolution inhibiting group (II) and not having acid dissociable, dissolution inhibiting group (III) Polymer (A21): Having structural unit (a11) and structural unit (a21) And having no structural unit (a12) or structural unit (a22), having an acid dissociable, dissolution inhibiting group (III) as an acid dissociable, dissolution inhibiting group, and the above acid dissociable, dissolution inhibiting group ( II) Polymer without

The polymer (A12) is a polymer having the structural unit (a11), the structural unit (a12), and at least one of the structural unit (a21) and the structural unit (a22).
The structural unit (a21) and the structural unit (a22) are not particularly limited as long as one of them is included. In particular, it is preferable to contain only the structural unit (a21) or to contain both the structural units (a21) and (a22).

In the polymer (A12), the structural unit (a11) may be the same as the structural unit (a21) in a state where the acid dissociable, dissolution inhibiting group is dissociated, that is, in a state where the acid dissociable, dissolution inhibiting group is substituted with a hydrogen atom. May be different. For example, the groups bonded to the α-position carbon atom of hydroxystyrene may be the same (both are hydrogen atoms or methyl groups) or may be different (one is a hydrogen atom and the other is a methyl group). In terms of alkali solubility control, both are preferably hydrogen atoms.
When the polymer (A12) has the structural unit (a22), the structural unit (a12) and the acid dissociable, dissolution inhibiting group are dissociated, that is, the acid dissociable, dissolution inhibiting group is replaced with a hydrogen atom. The structural unit (a22) may be the same or different. For example, the structural unit (a21) and the structural unit (a22) may be a structural unit derived from an acrylate ester or a structural unit derived from a methacrylic acid ester, and contain an alcoholic hydroxyl group. The structure of the aliphatic polycyclic group may be the same or different. In terms of alkali solubility control, both the structural unit (a12) and the structural unit (a22) are preferably structural units derived from an acrylate ester.

  In the polymer (A12), the acid dissociable, dissolution inhibiting group (II) is preferably a group in which Y in the formula (II-1) is an alkyl group, that is, a 1-alkoxyalkyl group.

  In the polymer (A12), the ratio of the total of the structural unit (a21) and the structural unit (a22) to the total of the structural unit (a11), the structural unit (a12), the structural unit (a21), and the structural unit (a22), That is, the protection ratio of the hydroxyl group in the copolymer (A-1) (ratio in which the hydrogen atom of the hydroxyl group is substituted with an acid dissociable, dissolution inhibiting group) is preferably 10 to 40 mol%, and preferably 15 to 35. More preferably, mol% is more preferable, and 20-30 mol% is further more preferable. By setting it to the upper limit of the above range or less, pattern defects (development defects) of the resist pattern after development can be effectively prevented. On the other hand, when the protection ratio of the hydroxyl group is not less than the lower limit of the above range, the etching resistance is improved and the film loss is reduced. In addition, degradation of resolution performance can be suppressed. Further, the higher the hydroxyl group protection ratio, the more the film loss after development can be reduced.

  In the polymer (A12), the total of the structural unit (a11) and the structural unit (a21) (hydroxystyrene-based structural unit) and the total of the structural unit (a12) and the structural unit (a22) ((α-lower) The ratio (molar ratio) to (alkyl) acrylic ester-based structural unit) is preferably in the range of 95: 5 to 50:50, and more preferably in the range of 95: 5 to 60:40. Preferably, 85:15 to 70:30 is more preferably within the above range, so that sufficient solubility in the developer can be secured.

  In the polymer (A12), the total of the structural unit (a11), the structural unit (a12), the structural unit (a21) and / or the structural unit (a22) is the polymer (A12). It is preferably 90 mol% or more, more preferably 95 mol% or more, and may be 100 mol% with respect to the total of all the constituent units to be constituted. When it is 90 mol% or more, the resolution is good.

The polymer (A12) may further have a structural unit (a3) in addition to the structural unit (a11), the structural unit (a12), the structural unit (a21), and the structural unit (a22).
When the structural unit (a3) is included, the proportion of the structural unit (a3) in the polymer (A12) is 0.5 to 10 mol% of the total of all the structural units constituting the polymer (A12). Preferably, 2 to 5 mol% is more preferable. When the structural unit (a3) is more than the above range, the solubility in the developer tends to deteriorate.

The polymer (A12) has a mass average molecular weight (Mw) of preferably 5000 or more and 20000 or less, and more preferably 4500 or more and 15000 or less. The resistance to dry etching of the resist pattern from which the mass average molecular weight is obtained is improved, and the film loss is improved. Moreover, generation | occurrence | production of a microbridge can be prevented. Moreover, heat resistance is favorable in this mass mean molecular weight being 2000 or more.
The microbridge here is a kind of development defect, for example, a defect in a line-and-space pattern in which a portion close to the surface of an adjacent resist pattern is connected by a resist and is in a bridged state. Microbridges are more likely to occur as the mass average molecular weight is higher and the post-exposure heating (PEB) temperature is higher.
Moreover, it is excellent in the resolution property that it is a monodispersed thing with a small dispersion degree (Mw / Mn ratio) of a polymer (A12). Specifically, the dispersity is preferably 2.0 or less, and more preferably 1.7 or less.

  As a polymer (A12), 1 type may be used independently and 2 or more types may be mixed and used.

The polymer (A12) is obtained, for example, by copolymerizing a monomer corresponding to the structural unit (a11) and a monomer corresponding to the structural unit (a12), and then the structural unit (a11) and / or the structural unit (a12). It can be produced by a method in which a part of the hydrogen atom of the hydroxyl group is protected with an acid dissociable, dissolution inhibiting group by a known method to form the structural unit (a21) and / or the structural unit (a22).
Alternatively, it can be produced by preparing monomers corresponding to the structural units (a11), (a12), (a21) and (a22) and copolymerizing them by a conventional method.

  In the polymer (A21), the proportion of the structural unit (a11) is based on the total of all the structural units constituting the polymer (A21) in terms of resolution, balance with the structural unit (a21), and the like. 30 to 70 mol% is preferable, 35 to 60 mol% is more preferable, and 40 to 55 mol% is most preferable.

  Moreover, it is preferable that the ratio of a structural unit (a21) in a polymer (A21) is 30-50 mol% with respect to the sum total of all the structural units which comprise a polymer (A21), and 35-45 mol. % Is more preferable. By setting the content ratio to be equal to or higher than the lower limit of the above range, an excellent exposure amount margin can be obtained, and the resolution, in particular, the resolution of an isolated line pattern is improved. Moreover, by making it below the upper limit of said range, a balance with a structural unit (a11) becomes favorable.

It is preferable that the mass average molecular weights of a polymer (A21) are 2000-30000, and 5000-20000 are more preferable.
By making the mass average molecular weight 30000 or less, solubility in a resist solvent can be improved, and by making it 2000 or more, a good resist pattern shape can be obtained.
Moreover, as a dispersion degree of a polymer (A21), it is excellent in the resolution property that it is monodispersion with a small dispersion degree, and preferable. Specifically, it is preferably 2.0 or less, and more preferably 1.7 or less.

  As the polymer (A21), one type may be used alone, or two or more types may be mixed and used.

For example, the polymer (A21) is obtained by polymerizing a monomer corresponding to the structural unit (a11), and then converting some of the hydrogen atoms of the hydroxyl group of the structural unit (a11) to an acid dissociable, dissolution inhibiting group ( It can be produced by a method in which the structural unit (a21) is protected with an acid dissociable, dissolution inhibiting group (including III).
Alternatively, a monomer corresponding to the structural unit (a21) is prepared in advance, polymerized by a conventional method, and then a part of the hydrogen atom of the hydroxyl group protected with an acid dissociable, dissolution inhibiting group is converted into a hydrogen atom by hydrolysis. It can manufacture also by the method of changing to and using as a structural unit (a11).

In the component (A), the content ratio (mass ratio) of the polymer (A12) and the polymer (A21) is preferably in the range of 10/90 to 90/10, and 20/80 to 80 / 20 is more preferable, and 20/80 to 70/30 is more preferable. By making the ratio within this range, the effect of the present invention becomes particularly excellent.
Further, the total amount of the polymer (A12) and the polymer (A21) in the component (A) is preferably 50 to 100% by mass and more preferably 70 to 100% by mass for the effect of the present invention. . Most preferably, 100% by mass, that is, the component (A) is preferably a mixed resin of the polymer (A12) and the polymer (A21).

  In the positive resist composition of the present invention, the content of the component (A) may be adjusted according to the resist film thickness to be formed.

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

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

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

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

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

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

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

  Specific examples of the onium salt-based acid generator include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, bis (4-tert-butylphenyl) iodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, and triphenylsulfonium trifluoromethane. Sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, tri (4-methylphenyl) sulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, dimethyl (4-hydroxynaphthyl) sulfonium trifluoromethane Sulfonate, its heptafluoropropane sulphonate or its Nafluorobutane sulfonate, trifluoromethane sulfonate of monophenyldimethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, trifluoromethane sulfonate of diphenyl monomethylsulfonium, heptafluoropropane sulfonate or nonafluorobutane sulfonate thereof, (4- Trifluoromethanesulfonate of methylphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, trifluoromethanesulfonate of (4-methoxyphenyl) diphenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, tri (4 -Tert-bu E) phenylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate, diphenyl (1- (6-methoxy) naphthyl) sulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate Is mentioned. In addition, onium salts in which the anion portion of these onium salts is replaced with methanesulfonate, n-propanesulfonate, n-butanesulfonate, or n-octanesulfonate can also be used.

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

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

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

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

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

（式（Ｂ−１）中、Ｒ^２１、Ｒ^２２はそれぞれ独立に有機基を表す。）

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

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

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

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

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

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

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

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

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

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

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

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

Specific examples of 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.
Moreover, the compound represented by the following chemical formula is mentioned.

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

  Among the above exemplified compounds, the following three compounds are preferable.

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) and 1,4-bis (phenylsulfonyldiazomethylsulfonyl) having the following structure. Butane (compound B), 1,6-bis (phenylsulfonyldiazomethylsulfonyl) hexane (compound C), 1,10-bis (phenylsulfonyldiazomethylsulfonyl) decane (compound D), 1,2-bis (cyclohexylsulfonyl) Diazomethylsulfonyl) ethane (compound E), 1,3-bis (cyclohexylsulfonyldiazomethylsulfonyl) propane (compound F), 1,6-bis (cyclohexylsulfonyldiazomethylsulfonyl) hexane (compound G), 1,10- Bis (cyclohex Le diazomethylsulfonyl) decane (compound H) and the like.

  Among them, the component (B) preferably contains at least one selected from the group consisting of an onium salt acid generator having a fluorinated alkyl sulfonate ion as an anion and an oxime sulfonate acid generator. It is more preferable to contain both an onium salt-based acid generator and an oxime sulfonate-based acid generator having an alkylsulfonate ion as an anion. Thereby, high resolution can be achieved.

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

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

In the positive resist composition of the present invention, a nitrogen-containing organic compound (D) (hereinafter referred to as “component (D)”) is further added as an optional component in order to improve the resist pattern shape, stability over time and the like. Can be blended.
Since a wide variety of components (D) have already been proposed, any known one may be used. 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, a secondary aliphatic amine and a tertiary aliphatic amine are particularly preferable, a trialkylamine having 5 to 10 carbon atoms is more preferable, and tri-n-octylamine is most 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 may further contain miscible additives as desired, for example, an additional resin for improving the performance of the resist film, a surfactant for improving coating properties, a dissolution inhibitor, Plasticizers, stabilizers, colorants, antihalation agents, dyes, and the like can be added and contained as appropriate.

As described above, the positive resist composition of the present invention is excellent in dimensional controllability. This is because the positive resist composition of the present invention can form a resist film whose performance is not easily changed in vacuum, that is, a resist film having high stability in vacuum. That is, conventionally, in the production of a photomask, exposure of a resist film is usually performed by direct writing with an electron beam in a vacuum (for example, 1 × 10 ⁻⁷ to 1 × 10 ⁻⁵ Pa). However, in exposure by direct drawing of an electron beam, it takes a long time (for example, about 12 to 24 hours) from the start to the end of drawing as the pattern becomes finer. Therefore, even within the same substrate surface, the time from exposure to post-exposure heating (PEB) and development differs between the first exposed portion and the last exposed portion. Conventionally, since the resist film has low stability in vacuum and the performance change over time is large, there is a difference in resist performance, and the pattern size of the first exposed part and the last exposed part of the pattern are different. It is presumed that the dimensional controllability was lowered as a result of the difference in pattern dimensions. On the other hand, the positive resist composition of the present invention is considered to have good dimensional controllability because of high stability in vacuum and small change in performance over time.
Furthermore, the positive resist composition of the present invention is not easily affected by the substrate, and a rectangular pattern can be formed on any substrate, for example, on a silicon substrate or an antireflection film.

<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. Further, for example, an electron beam or other far ultraviolet rays are selectively exposed with or without a desired mask pattern by an electron beam drawing apparatus or the like. That is, after exposing through a mask pattern or drawing by direct irradiation with an electron beam without passing through a mask pattern, PEB (post-exposure heating) is performed for 40 to 120 seconds under a temperature condition of 80 to 150 ° C., preferably Apply for 60-90 seconds. Next, this is developed using an alkali developer, for example, an aqueous solution of 0.1 to 10% by mass of tetramethylammonium hydroxide (TMAH). 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 of the electron beam or other far ultraviolet rays used for exposure is not particularly limited, and ArF excimer laser, KrF excimer laser, F ₂ laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), electron beam, X-ray, It can be performed using radiation such as soft X-rays.
Since the positive resist composition of the present invention has high stability under vacuum, it can be suitably used for resist pattern formation including an exposure step under vacuum, and for EUV (extreme ultraviolet) or electron beam use. Particularly preferred for an electron beam.

Examples of the present invention will be described below, but the scope of the present invention is not limited to these examples.
Examples 1-4, Comparative Example 1, Examples 5-8, Comparative Example 2
100 parts by mass of component (A) shown in Table 1 below, 8 parts by mass of α- (methyloxyimino) -p-methoxyphenylacetonitrile as component (B), and 0.96 parts by mass of trimethyl as component (D) -N-octylamine, 0.364 parts by weight of salicylic acid as component (E), and 0.05 parts by weight of surfactant “XR-08” (trade name, manufactured by Dainippon Ink & Chemicals, Inc.) A positive resist composition solution was prepared by dissolving in 1150 parts by mass of propylene glycol monomethyl ether acetate.

The obtained positive resist composition solution was uniformly applied on an 8-inch silicon substrate subjected to hexamethyldisilazane treatment so as to have the resist film thickness shown in Table 1 below, and baked at 110 ° C. for 90 seconds. The film was formed by performing the treatment (PAB). The substrate was drawn with an electron beam drawing machine (Hitachi HL-800D, 70 kV acceleration voltage) and then baked (PEB) at 110 ° C. for 90 seconds, with a 2.38 mass% TMAH aqueous solution. After developing at 23 ° C. for 60 seconds, rinsing with pure water for 30 seconds, performing shake-off drying, post-baking treatment is performed at 100 ° C. for 60 seconds, and a line and space with a line width of 200 nm (line width / space width = A resist pattern (hereinafter, referred to as a 200 nm resist pattern) targeting 1/1) was formed.
The obtained resist pattern was observed with a scanning electron microscope (SEM), and the limit resolution (nm) at the optimum exposure amount at which a 200 nm resist pattern was formed was determined. The results are shown in Table 2 as “resolution”.

Further, the positive resist composition solution obtained above was applied on an 8-inch silicon substrate so as to have a resist film thickness of 300 nm, and was subjected to PAB at 110 ° C. for 90 seconds to form a film. In the electron beam drawing apparatus (Hitachi HL-800D, 70 kV acceleration voltage), the drawing is performed at the same exposure amount every 2 hours after being drawn for 24 hours at maximum, and then 23 ° C. with 2.38 mass% TMAH aqueous solution. The film was developed for 60 seconds, rinsed with pure water for 30 seconds, shaken and dried, and then post-baked at 100 ° C. for 60 seconds. As a result, a plurality of 200 nm resist patterns having different times of leaving in the drawing apparatus were formed on the same substrate. The pressure in the drawing apparatus was 1.8 × 10 ⁻⁵ Pa.
With respect to the obtained resist pattern of 200 nm, the dimensional change was calculated as follows. The results are shown in Table 2.
Dimensional change amount (nm) = line width having the largest change amount−200 nm (of the formed resist pattern, the value obtained by subtracting 200 nm from the line width of the thickest part of the line pattern and 200 nm from the line width of the thinnest part) The value with the larger absolute value)
In Table 2, a value of + indicates that the pattern is thick, and a value of-indicates that the pattern is thin.

［式中、ａ^１：ｂ^１：ｃ^１：ｄ^１（モル比）＝５８：１７：２２：３（モル比）であり、Ｅｖは１−エトキシエチル基を表す。Ｍｗ＝１２０００、Ｍｗ／Ｍｎ＝１．７］

[Wherein, a ¹ : b ¹ : c ¹ : d ¹ (molar ratio) = 58: 17: 22: 3 (molar ratio), and Ev represents a 1-ethoxyethyl group. Mw = 12000, Mw / Mn = 1.7]

［式中、ａ^２：ｂ^２：ｃ^２：ｄ^２（モル比）＝５７：１７：２３：３であり、Ｅｖは１−エトキシエチル基を表す。Ｍｗ＝１００００、Ｍｗ／Ｍｎ＝１．５］

[Wherein, a ² : b ² : c ² : d ² (molar ratio) = 57: 17: 23: 3, and Ev represents a 1-ethoxyethyl group. Mw = 10000, Mw / Mn = 1.5]

［式中、ｍ：ｎ（モル比）＝５６：４４である。Ｍｗ＝１２４００、Ｍｗ／Ｍｎ＝１．２］

[Wherein, m: n (molar ratio) = 56: 44. Mw = 12400, Mw / Mn = 1.2]

As shown in the above results, in each of Examples 1 to 7, the resolution was 70 nm and the dimensional change was small. In Example 8, the resolution was sufficiently high as 80 nm, and the dimensional change was very small. From this, it was confirmed that the dimensional controllability of the positive resist compositions of Examples 1 to 8 was excellent in stability in vacuum. Among them, Examples 2 to 4 and Examples 6 to 8 in which the resin 1 or the resin 2 and the resin 5 are used in a ratio within the range of 20/80 to 70/30 (mass ratio) have particularly good results. Met.
On the other hand, although the positive resist compositions of Comparative Examples 1 and 2 had high resolution, the dimensional change was large and the stability in vacuum was low.

Claims (9)

A resin component (A) having an alkali-soluble structural unit (a1) and a structural unit (a2) having an acid dissociable, dissolution inhibiting group, and increased in alkali solubility by the action of an acid, and generates an acid upon exposure. A positive resist composition comprising an acid generator component (B),
The structural unit (a1) is a structural unit (a11) derived from (α-methyl) hydroxystyrene, and a structural unit (a12) derived from an (α-lower alkyl) acrylic acid ester having an alcoholic hydroxyl group; Have
In the structural unit (a2), the hydrogen atom of the hydroxyl group of the structural unit (a11) is substituted with an acid dissociable, dissolution inhibiting group, and / or the alcoholic hydroxyl group of the structural unit (a12). It has a structural unit (a22) in which a hydrogen atom is substituted with an acid dissociable, dissolution inhibiting group, and the acid dissociable, dissolution inhibiting group has the following general formula (II)

[Wherein, X represents an aliphatic cyclic group, an aromatic cyclic hydrocarbon group, or an alkyl group having 1 to 5 carbon atoms, R ¹ represents an alkyl group having 1 to 5 carbon atoms, or X and R ¹ Each independently represents an alkylene group having 1 to 5 carbon atoms, and the end of X and the end of R ¹ may be bonded to each other, and R ² represents an alkyl group having 1 to 5 carbon atoms or a hydrogen atom. ]
At least selected from the group consisting of an acid dissociable, dissolution inhibiting group (II) represented by: a chain tertiary alkoxycarbonyl group, a chain tertiary alkyl group, and a chain tertiary alkoxycarbonylalkyl group A positive resist composition comprising one type of acid dissociable, dissolution inhibiting group (III).   The positive resist composition according to claim 1, wherein the structural unit (a12) is a structural unit derived from an aliphatic polycyclic group-containing (α-lower alkyl) acrylate ester having an alcoholic hydroxyl group. The acid dissociable, dissolution inhibiting group (II) is represented by the following general formula (II-1)

[Wherein, Y represents an aliphatic cyclic group, an aromatic cyclic hydrocarbon group, or an alkyl group having 1 to 5 carbon atoms, and R ¹ represents an alkyl group having 1 to 5 carbon atoms. ]
The positive resist composition according to claim 1, which is an acid dissociable, dissolution inhibiting group represented by the formula:   The positive resist composition according to any one of claims 1 to 3, wherein the acid dissociable, dissolution inhibiting group (III) is a chain-like tertiary alkoxycarbonyl group. The resin component (A) has the structural unit (a11), the structural unit (a12), the structural unit (a21) and / or the structural unit (a22), and has an acid dissociable dissolution A polymer (A1) having the acid dissociable, dissolution inhibiting group (II) as an inhibiting group and not having the acid dissociable, dissolution inhibiting group (III);
It has the structural unit (a11) and the structural unit (a21), does not have the structural unit (a12) and the structural unit (a22), and the acid dissociable dissolution inhibiting group as an acid dissociable dissolution inhibiting group The positive resist composition according to any one of claims 1 to 4, comprising a polymer (A2) having (III) and not having the acid dissociable, dissolution inhibiting group (II).   The positive resist composition according to claim 5, wherein the content ratio (mass ratio) of the polymer (A1) and the polymer (A2) is in the range of 10/90 to 90/10.   The positive resist composition according to claim 5 or 6, wherein a proportion of the structural unit (a21) with respect to a total of all the structural units constituting the polymer (A2) is 30 to 50 mol%.   Furthermore, the positive resist composition as described in any one of Claims 1-7 containing a nitrogen-containing organic compound (D). A step of forming a resist film on a substrate using the positive resist composition according to claim 1, a step of selectively exposing the resist film, and alkali developing the resist film. A resist pattern forming method including a step of forming a resist pattern.