JP2006106265A - Positive resist composition and method for forming resist pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive resist composition for forming a resist pattern with high sensitivity and to provide a method for forming a resist pattern. <P>SOLUTION: The positive resist composition contains: a resin component (A) which has an alkali-soluble structural unit (a1) and a structural unit (a2) having an acid dissociable dissolution inhibiting group, and the alkali solubility of which is enhanced by the effect of an acid; and an acid generator component (B) which generates an acid upon exposure. The structural unit (a2) has an acid dissociable dissolution inhibiting group (II) expressed by formula (II), and the acid generator component (B) contains an onium salt-based acid generator (B-1) having a sulfonic acid ion expressed by formula (B-1) as an anion. In the formulae, R<SP>1</SP>represents an alkyl group; R<SP>2</SP>represents an alkyl group or a hydrogen atom; X represents an aliphatic cyclic group, an aromatic cyclic hydrocarbon group or an alkyl group, wherein the end of the alkyl group of R<SP>1</SP>may be bonded with the end of the alkyl group of X to form a cyclic group; and R<SP>10</SP>represents an alkyl group or a cycloalkyl group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, miniaturization has rapidly progressed due to advances in lithography technology. As a technique for miniaturization, the wavelength of an exposure light source is generally shortened. Specifically, in the past, ultraviolet rays typified by g-line and i-line were used, but now KrF excimer laser (248 nm) is the center of mass production, and ArF excimer laser (193 nm) is mass-produced. It has begun to be introduced. Research is also being conducted on lithography technology using an F ₂ excimer laser (157 nm), EUV (extreme ultraviolet light), EB (electron beam) or the like as a light source (radiation source).
Such a resist for a short wavelength light source is required to have high resolution capable of reproducing a pattern with a fine dimension and high sensitivity to such a short wavelength light source. As one of the resists satisfying such conditions, a chemically amplified resist containing a base resin and an acid generator that generates an acid upon exposure is known. The chemically amplified resist includes an alkali in an exposed portion. There are a positive type in which the solubility is increased and a negative type in which the alkali solubility in the exposed portion is reduced.

So far, as the acid generator for chemically amplified resists, onium salt acid generators using fluorinated alkyl sulfonate ions as anions (acids), such as triphenylsulfonium nonafluorobutanesulfonate (TPS-PFBS), are the most common. It is generally used, and other acids are not used so much because of acidity.
In addition, as a base resin of a chemically amplified resist, for example, in the case of a positive type, generally, a resin in which a hydroxyl group of polyhydroxystyrene is protected with an acid dissociable, dissolution inhibiting group, or an acid dissociable, dissolution inhibiting group at an ester portion ( Resins having structural units derived from (meth) acrylic acid esters are used. Examples of the acid dissociable, dissolution inhibiting group of the base resin include chain ether groups such as 1-ethoxyethyl group, so-called acetal groups such as cyclic ether groups such as tetrahydropyranyl group, tert-butyl group, 2-alkyl-2 -Tertiary alkyl groups such as adamantyl group and tertiary alkoxycarbonyl groups such as tert-butoxycarbonyl group are mainly used (for example, see Patent Documents 1 and 2).
JP-A-8-262721 JP 2002-341538 A

However, further refinement is required, and further improvement in sensitivity is demanded as the wavelength of the exposure light source is shortened. For example, in a lithography process using a short wavelength light source such as an electron beam, a conventional chemically amplified resist composition has insufficient sensitivity.
This invention is made | formed in view of the said situation, Comprising: It aims at providing the positive resist composition and resist pattern formation method which can form a resist pattern with high sensitivity.

As a result of intensive studies, the present inventors have used a combination of a resin component having an acetal group having a specific structure as an acid dissociable, dissolution inhibiting group and an onium salt-based acid generator having an alkyl sulfonate ion as an anion. The inventors have found that the above problems can be solved, and have completed the present invention.
That is, the first aspect of the present invention is a resin component having an alkali-soluble structural unit (a1) and a structural unit (a2) having an acid dissociable, dissolution inhibiting group, and having increased alkali solubility by the action of an acid. A positive resist composition comprising (A) and an acid generator component (B) that generates an acid upon exposure,
The structural unit (a2) is represented by 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）を有し、
前記酸発生剤成分（Ｂ）が、下記一般式（Ｂ−１）

[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 Is an alkylene group having 1 to 5 carbon atoms, the end of X may be bonded to the end of R ¹ , and R ² represents an alkyl group having 1 to 5 carbon atoms or a hydrogen atom. ]
Having an acid dissociable, dissolution inhibiting group (II) represented by
The acid generator component (B) is represented by the following general formula (B-1)

［式中、Ｒ^１０はアルキル基またはシクロアルキル基を表す。］
で表されるスルホン酸イオンをアニオンとするオニウム塩系酸発生剤（Ｂ−１）を含有することを特徴とするポジ型レジスト組成物である。
また、本発明の第二の態様は、第一の態様のポジ型レジスト組成物を用いて基板上にレジスト膜を形成する工程、前記レジスト膜を露光する工程、前記レジスト膜を現像してレジストパターンを形成する工程を含むレジストパターン形成方法である

[Wherein, R ¹⁰ represents an alkyl group or a cycloalkyl group. ]
A positive resist composition comprising an onium salt acid generator (B-1) having a sulfonate ion represented by
The second aspect of the present invention includes a step of forming a resist film on a substrate using the positive resist composition of the first aspect, a step of exposing the resist film, and developing the resist film to form a resist. A method for forming a resist pattern including a step of forming a pattern

  In the present invention, “structural unit” means a monomer unit constituting a polymer. In addition, “exposure” is a concept that includes irradiation of radiation in general, and includes drawing of an electron beam and irradiation through a mask.

  According to the present invention, a positive resist composition and a resist pattern forming method capable of forming a resist pattern with high sensitivity 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, if exposure is performed through a mask pattern in the formation of a resist pattern, or if post-exposure heating (PEB) is performed in addition to exposure, the exposed area turns into alkali-soluble while the unexposed area remains insoluble in alkali. A positive resist pattern can be formed by alkali development.

[(A) component]
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.

Examples of the structural unit (a1) include the following structural unit (a11), the following structural unit (a12), and a structural unit derived from (meth) acrylic acid. Among these, the structural unit (a11) and the structural unit (a12) are preferably used because they have high dry etching resistance, are easily available, and are inexpensive.
“(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.

  The structural unit (a11) is a structural unit represented by the general formula (I).

［式中、Ｒは水素原子またはメチル基を表す。］

[Wherein, R represents a hydrogen atom or a methyl group. ]

In formula (I), R is a hydrogen atom or a methyl group, and is preferably a hydrogen atom. When R is a hydrogen atom, the protection rate of the hydroxyl group can be improved, and the contrast can be improved. Further, the dissolution rate after development can be increased.
The position of the hydroxyl group may be any of the o-position, the m-position, and the p-position, but the p-position is preferred because it is readily available and inexpensive.

The structural unit (a12) is a structural unit derived from an aliphatic polycyclic group-containing (meth) acrylic acid ester having an alcoholic hydroxyl group. Here, “structural unit derived from (meth) acrylic acid ester” means a structural unit formed by cleavage of the ethylenic double bond of (meth) acrylic acid ester.
Such a structural unit (a12) has lower solubility in an alkaline developer than the structural unit (a11). Therefore, when the component (A) has the structural unit (a12), the component (A) in a state where the acid dissociable, dissolution inhibiting group is dissociated is more than when the structural unit (a1) has only the structural unit (a11). Has low solubility in an alkaline developer. 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. Further, since it contains an aliphatic polycyclic group, it is expected to improve etching resistance and reduce film loss after etching.

  Examples of the polycyclic group constituting the aliphatic polycyclic group having an alcoholic hydroxyl group include a group in which one hydrogen atom is removed from bicycloalkane, tricycloalkane, teracycloalkane, or 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.

As the structural unit (a12), in particular, a structural unit derived from an adamantyl group-containing (meth) acrylic acid ester having at least one alcoholic hydroxyl group represented by the following general formula (IV) is preferably used. it can.
Among the structural units (a12) represented by the following general formula (IV), the structural units represented by the following general formula (IVa) are most preferable.

（式中、Ｒは水素原子又はメチル基、ｘは１〜３の整数である。）

(In the formula, R is a hydrogen atom or a methyl group, and x is an integer of 1 to 3.)

  Among the structural units (a12), a structural unit derived from an acrylate ester has higher solubility in an alkaline developer than a structural unit derived from a methacrylic acid ester. Therefore, when a structural unit derived from an acrylate ester is used as the structural unit (a12), the proportion of the structural unit (a2) having an acid dissociable, dissolution inhibiting group is higher than when a structural unit derived from a methacrylic acid ester is used. And the contrast can be improved. Therefore, it is more preferable to use a structural unit derived from an acrylate ester having an alcoholic hydroxyl group as the structural unit (a12) in order to improve resolution while suppressing development defects. It is preferable that 80 mol% or more of the structural unit (a12) is a structural unit derived from an acrylate ester having an alcoholic hydroxyl group, and 100 mol% is more preferable.

  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.

As the structural unit (a2), for example, a structural unit in which the hydroxyl group (phenolic hydroxyl group) of the structural unit (a11) is protected with an acid dissociable, dissolution inhibiting group (hereinafter referred to as structural unit (a21)), the above structural unit A structural unit in which the alcoholic hydroxyl group of the unit (a12) is protected with an acid dissociable, dissolution inhibiting group (hereinafter referred to as structural unit (a22)), and the carboxy group of the structural unit derived from (meth) acrylic acid is acid dissociated. And a structural unit protected with a soluble dissolution inhibiting group.
Here, “the hydroxyl group is protected by an acid dissociable, dissolution inhibiting group” means that the hydrogen atom of the hydroxyl group is substituted with an acid dissociable, dissolution inhibiting group. Further, “the carboxy group is protected by an acid dissociable, dissolution inhibiting group” means that the hydrogen atom of the carboxy group is substituted with an acid dissociable, dissolution inhibiting group.

  In the present invention, the structural unit (a2) needs to have the acid dissociable, dissolution inhibiting group (II) represented by the general formula (II) as the acid dissociable, dissolution inhibiting group. By using a combination of the component (A) having the structural unit (a2) having the acid dissociable, dissolution inhibiting group (II) and the onium salt acid generator (B-1) described later, a positive resist composition is used. High sensitivity is achieved.

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 said structural unit (a22), 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 the same groups as 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、Ｒ^１は炭素数１〜５のアルキル基を表し、Ｙは脂肪族環式基または芳香族炭化水素基または炭素数１〜５のアルキル基を表す。］

[Wherein, R ¹ represents an alkyl group having 1 to 5 carbon atoms, and Y represents an aliphatic cyclic group, an aromatic hydrocarbon group, or 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 or aromatic hydrocarbon group of Y or an alkyl group having 1 to 5 carbon atoms, the aliphatic cyclic group of X in the general formula (II), the aromatic hydrocarbon group, or the carbon number It is the same as the alkyl group of 1-5.

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. The group in which Y is an aliphatic polycyclic group is a 1-cyclohexyloxyethyl group and a 1- (1-adamantyl) oxyethyl group represented by the following formula (II-a). Examples of the group in which Y is an aromatic 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 component (A) may have, as the structural unit (a2), a structural unit having an acid dissociable, dissolution inhibiting group other than the acid dissociable, dissolution inhibiting group (II) as necessary.
As the acid dissociable, dissolution inhibiting group other than the acid dissociable, dissolution inhibiting group (II), 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. For example, a chain tertiary alkyl group such as a tert-butyl group and a tert-amyl group; a 1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a 1-methyl-1-cyclohexyl group, 1-ethyl-1-cyclohexyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 2-propyl-2-adamantyl group, 2- (1-adamantyl) -2-propyl group, 8 -Methyl-8-tricyclo [5.2.1.0 ^2,6 ] decanyl group, 8-ethyl-8-tricyclo [5.2.1.0 ^2,6 ] decanyl group, 8-methyl-8-teto Rashikuro [4.4.0.1 ^2,5 .1 ^7,10] dodecanyl group, fats such as 8-ethyl-8-tetracyclo [4.4.0.1 ^2,5 .1 ^7,10] dodecanyl group And tertiary alkyl groups having a ring structure.

  In the component (A), the proportion of the structural unit (a2) is preferably from 5 to 45 mol%, more preferably from 15 to 40 mol%, based on all the structural units constituting the component (A). . Thereby, it is possible to sufficiently ensure alkali insolubility in the unexposed portion of the resist film when forming the resist pattern.

In the component (A), it is preferable that at least one of the structural units (a1) and (a2) contains a polycyclic group. When at least one of the structural units (a1) and (a2) contains a polycyclic group, the sensitivity is further improved. In addition, by having a polycyclic group, an improvement in dry etching resistance of a resist film obtained using the positive resist composition is expected.
Here, “at least one of the structural units (a1) and (a2) has a polycyclic group” means a polycyclic group in the structure of at least one of the structural units (a1) and (a2). It means that the group exists in an organic chemical bond state.
The polycyclic group may further have an alkali-soluble functional group such as a hydroxyl group or a carboxy group, or a lower alkyl group such as a methyl group, an ethyl group or a propyl group, or a group in the acid dissociable, dissolution inhibiting group. It may be included in some. Specific examples include the structural unit (a12) and the structural unit (a21) described above.

Examples of the polycyclic group contained in at least one of the structural units (a1) and (a2) include an aliphatic polycyclic group and an aromatic polycyclic group. By having an aliphatic polycyclic group, high resolution can be obtained. Further, the resist pattern has a rectangular shape with a good cross-sectional shape. In addition, by having an aromatic polycyclic group, sensitivity is improved, throughput is high, and productivity can be improved. Among these, an aliphatic polycyclic group is preferable because the line edge roughness of the resist pattern and the rectangular shape of the cross-sectional shape are improved.
Examples of the aliphatic polycyclic group include those exemplified as the aliphatic polycyclic group in X above. Examples of the aromatic polycyclic group include those similar to those exemplified as the aromatic polycyclic hydrocarbon group in X above.

  In addition to the structural units (a1) and (a2), the component (A) may further include a structural unit (a3) represented by the following general formula (III). In the present invention, the structural unit (a3) is not essential, but if it is contained, the alkali solubility can be controlled by the content thereof. For example, the content of the structural unit (a3) can be increased by increasing the content of the component (A). When the alkali solubility is lowered, the film loss of the resist film after development can be reduced. This also has the advantage that the line edge roughness can be reduced and a good isolated line can be obtained.

［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). % Is more preferable. When the structural unit (a3) is more than the above range, the alkali solubility tends to be low, the line edge roughness is increased, and a good isolated line tends not to be obtained.

  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. In particular, the mass average molecular weight in a state where all the acid dissociable, dissolution inhibiting groups are dissociated is preferably 2000 to 30000, and more preferably 4000 to 20000. By making the mass average molecular weight in the state where all of the acid dissociable, dissolution inhibiting groups are dissociated to 30000 or less, sufficient solubility in a resist solvent can be secured, and by making it 2000 or more, the dry etching resistance of the resulting resist pattern can be ensured. Improves film loss. Further, within the above range, the film loss after etching is reduced as the mass average molecular weight is larger.

For example, the component (A) is obtained by polymerizing a monomer corresponding to the structural unit (a1), and then protecting a part of the polar group of the structural unit (a1) with an acid dissociable, dissolution inhibiting group by a known method. It can be produced by the method of forming the structural unit (a2).
Alternatively, a monomer corresponding to the structural unit (a2) is prepared, this monomer is polymerized by a conventional method, and then the acid dissociable, dissolution inhibiting group is dissociated by hydrolysis to form the structural unit (a1). If it exists, it can manufacture also by the method of protecting the polar group of a structural unit (a1) with an acid dissociable, dissolution inhibiting group by a well-known method, and making it a structural unit (a2).

  In the present invention, particularly preferable component (A) includes, for example, the following polymer (A1) and polymer (A2). By using the following polymer (A1) or polymer (A2) as the component (A), the dry etching resistance necessary for the resist process can be ensured, and the film loss during dry etching is reduced. A resolution resist pattern can be obtained, and the occurrence of pattern defects (development defects) in the resist pattern after development can be suppressed.

・ Polymer (A1)
The polymer (A1) is a polymer having the structural unit (a11) and the structural unit (a21).
In the polymer (A1), the structural unit (a11) and the structural unit (a21) not protected by the acid dissociable, dissolution inhibiting group may be the same or different. That is, R in the structural unit (a11) and R in the structural unit (a21) may be the same or different. From the viewpoint of controlling alkali solubility, it is preferable that both R in the structural unit (a11) and R in the structural unit (a21) are hydrogen atoms.
The polymer (A1) may have a structural unit other than the structural unit (a11) and the structural unit (a21), for example, the structural unit (a3).

In the polymer (A1), the proportion of the structural unit (a11) is preferably 50 to 95 mol% of the structural unit (a11) with respect to the total of all the structural units constituting the polymer (A1). -85 mol% is more preferable, and 55-75 mol% is the most preferable.
Moreover, 5-50 mol% is preferable with respect to the sum total of all the structural units which comprise a polymer (A1), and the ratio of a structural unit (a21) has more preferable 10-45 mol%, 15-45 mol%. Is more preferable. In particular, when it does not have a structural unit (a3), 20-45 mol% is more preferable, and when it has a structural unit (a3), 10-20 mol% is more preferable.
By setting the content ratio to be equal to or higher than the lower limit value of the above range, good contrast can be obtained, and by making the content ratio equal to or lower than the upper limit value of the above range, an effect of preventing development defects can be obtained.

As a polymer (A1), 1 type may be used independently and 2 or more types may be mixed and used.
In the case of using a mixture of two or more kinds as the polymer (A1), a polymer having the structural unit (a11) and the structural unit (a21) and not having the structural unit (a3), and a structural Any two or more selected from the group consisting of a polymer having the unit (a11), the structural unit (a21) and the structural unit (a3) can be combined. That is, those having different mass average molecular weights of those polymers and those having different proportions of the respective structural units can be arbitrarily mixed and used. Such a mixture includes a polymer having the structural unit (a11) and the structural unit (a21) and not having the structural unit (a3), the structural unit (a11), the structural unit (a21), and the structural unit ( and a mixture with a polymer having a3). By using such a mixture as the polymer (A1), the formed resist pattern has a good rectangular shape and an excellent isolated line can be obtained.

The polymer (A1) preferably has a mass average molecular weight (in terms of polystyrene, the same shall apply hereinafter) in a state where all of the acid dissociable, dissolution inhibiting groups are dissociated, and more preferably 5000 to 20000. By setting the mass average molecular weight to 30000 or less, the solubility in a resist solvent can be improved, and by setting the mass average molecular weight to 2000 or more, the dry etching resistance of the resulting resist pattern is improved and film loss is improved. Also, a good resist pattern shape can be obtained.
The polymer (A1) has a dispersity (Mw / Mn ratio) in a state in which all of the acid dissociable, dissolution inhibiting groups are dissociated (a value obtained by dividing the mass average molecular weight by the number average molecular weight. The same shall apply hereinafter). Monodispersion having a small degree of dispersion is preferable because of excellent resolution. Specifically, 2.0 or less is preferable, and 1.5 or less is more preferable.

For example, the polymer (A1) is obtained by polymerizing a monomer corresponding to the structural unit (a11), and then converting a part of the hydrogen atoms of the hydroxyl group of the structural unit (a11) with an acid dissociable, dissolution inhibiting group by a known method. It can be produced by a method of protecting the structural unit (a21).
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).

・ Polymer (A2)
The polymer (A2) 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).
That is, the polymer (A2) has the structural unit (a11) and the structural unit (a12) as the structural unit (a1), and at least the structural unit (a21) and the structural unit (a22) as the structural unit (a2). Have one.

When the polymer (A2) has the structural unit (a21), in the polymer (A2), the structural unit (a11) and the structural unit (a21) that is not protected by the acid dissociable, dissolution inhibiting group are: It may be the same or different. That is, R in the structural unit (a11) and R in the structural unit (a21) may be the same or different. From the viewpoint of controlling alkali solubility, it is preferable that both R in the structural unit (a11) and R in the structural unit (a21) are hydrogen atoms.
Further, when the polymer (A2) has the structural unit (a22), the structural unit (a21) and the structural unit (a22) not protected by the acid dissociable, dissolution inhibiting group are the same or different. Also good. That is, 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. The structure of the aliphatic polycyclic group contained 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 (A2), particularly, the acid dissociable, dissolution inhibiting group is a group in which Y in the general formula (II-1) is an alkyl group having 1 to 5 carbon atoms, that is, a 1-alkoxyalkyl group. Is preferred.

In the polymer (A2), the total of the structural unit (a21) and the structural unit (a22) with respect to the total of the structural unit (a11), the structural unit (a12), the structural unit (a21), and the structural unit (a22). The ratio, that is, the ratio of protecting the hydroxyl group in the polymer (A2) (ratio in which the hydrogen atom of the hydroxyl group is substituted with an acid dissociable, dissolution inhibiting group) is preferably 10 to 35 mol%, and 20 to 30 mol%. It is more preferable that
By making the protection ratio of the hydroxyl group below the upper limit of the above range, 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.

  The polymer (A2) is not particularly limited as long as it contains either the structural unit (a21) or the structural unit (a22). In particular, it is preferable to have only the structural unit (a22) or have both the structural unit (a12) and the structural unit (a22).

  In the polymer (A2), the molar ratio of the total of the structural unit (a11) and the structural unit (a12) to the total of the structural unit (a21) and the structural unit (a22) is 95: 5-75: It is preferable to be within the range of 25, and a more preferable range is 82:18 to 78:22. By setting it in the above range, sufficient solubility in a developer can be secured.

  Moreover, in the polymer (A2), the total of the structural unit (a11), the structural unit (a12), the structural unit (a21), and the structural unit (a22) is the total structural unit constituting the polymer (A2). It is preferable that it is 90 mol% or more of the total. When it is less than 90 mol%, the resolution tends to deteriorate. The total of the structural unit (a11), the structural unit (a12), the structural unit (a21), and the structural unit (a22) is more preferably 95 mol% or more, and may be 100 mol%.

In addition to the structural unit (a11), the structural unit (a12), the structural unit (a21), and the structural unit (a22), the polymer (A2) is further composed of the structural unit (a3) in the same manner as the polymer (A1). You may have.
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 further improved dry etching resistance can be obtained.
When the structural unit (a3) is included, the proportion of the structural unit (a3) in the polymer (A2) is 0.5 to 10 mol% of the total of all the structural units constituting the polymer (A2). 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 (A2) preferably has a mass average molecular weight of 2000 or more and 8500 or less, more preferably 4500 or more and 8500 or less, in a state where all of the acid dissociable, dissolution inhibiting groups are dissociated. When the mass average molecular weight is 8500 or less, the dry etching resistance of the resulting resist pattern is improved, and 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. Further, the mass average molecular weight of the polymer (A2) is preferably 8600 or more and 20000 or less, more preferably 9000 or more and 15000 or less, from the protection ratio of the acid dissociable, dissolution inhibiting group described above.
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.
The polymer (A2) is preferably excellent in resolution when it is monodispersed with a small degree of dispersion (Mw / Mn ratio) in a state where the acid dissociable, dissolution inhibiting group is dissociated. Specifically, the dispersity is preferably 2.0 or less, and more preferably 1.7 or less.

For example, the polymer (A2) is obtained 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 positive resist composition of the present invention, the component (A) may be either the polymer (A1) or the copolymer (A2), or a mixture thereof.

  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.

[Component (B)]
The present invention is characterized in that the component (B) contains an onium salt acid generator (B-1) having a sulfonate ion represented by the following general formula (B-1) as an anion.

In formula (B-1), R ¹⁰ represents an alkyl group or a cycloalkyl group.
Examples of the alkyl group for R ¹⁰ include linear or branched alkyl groups having 1 to 10 carbon atoms.
Examples of the cycloalkyl group represented by R ¹⁰ include cycloalkyl groups having 3 to 10 carbon atoms such as a cyclopentyl group and a cyclohexyl group, and preferably 3 to 6 carbon atoms.

  As an onium salt type acid generator (B-1), what is necessary is just to use the sulfonate ion represented by general formula (B-1) as an anion, As a cation which comprises onium salt with this anion, The cation of a known acid generator proposed in a conventional chemically amplified resist composition is not particularly limited. Examples of such cations include sulfonium ions and iodonium ions.

  In the present invention, the onium salt-based acid generator (B-1) preferably contains an onium salt represented by the following general formula (B-11) because of excellent effects of the present invention.

［式中、Ｒ^１１〜Ｒ^１３はそれぞれ独立にアリール基またはアルキル基を表し、ｑは１〜１０の整数である。］

[In formula, R < ¹¹ > -R < ¹³ > represents an aryl group or an alkyl group each independently, and q is an integer of 1-10. ]

In formula (B-11), R ^{11 to} R ¹³ each independently represents an aryl group or an alkyl group, and at least one of R ^{11 to} R ¹³ is preferably an aryl group, and two or more are aryl groups. It is more preferable that all of R ^{11 to} R ¹³ are aryl groups.
The aryl group of R ¹¹ to R ^13, not particularly limited, for example, an aryl group having 6 to 20 carbon atoms, an alkyl group, a phenyl group which may not be substituted with a halogen atom or the like And a naphthyl group. An aryl group having 6 to 10 carbon atoms is preferable because it can be synthesized at low cost.
The alkyl group of R ¹¹ to R ^13, 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 ^{11 to} R ¹³ are phenyl groups.

q is an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 4 to 8, and most preferably 4 or 8 from the viewpoint of easy industrial synthesis.
In addition, the alkyl group represented by C _q H _{2q + 1} may be linear or branched, and is preferably a linear alkyl group such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, An n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, and the like can be given.

  The onium salt acid generator (B-1) may be used alone or in combination of two or more.

  In this embodiment, the component (B) further contains a known acid generator (hereinafter sometimes referred to as other acid generator (B-2)) that has been used in conventional chemically amplified resist compositions. However, for the effect of the present invention, the proportion of the onium salt acid generator (B-1) in the component (B) is 50 to 100% by mass of the whole component (B). Is preferable, 80-100 mass% is more preferable, and it is most preferable that it is 100 mass%.

  Other acid generators (B-2) include onium salt acid generators such as iodonium salts and sulfonium salts (excluding the onium salt acid generator (B-1)), oxime sulfonates, and the like. Acid generators, diazomethane acid generators such as bisalkyl or bisarylsulfonyldiazomethanes, poly (bissulfonyl) diazomethanes, nitrobenzyl sulfonate acid generators, iminosulfonate acid generators, disulfone acid generators, etc. Many things are known.

  Specific examples of onium salt-based acid generators other than the onium salt-based acid generator (B1) in the other acid generators (B2) include diphenyliodonium trifluoromethanesulfonate, nonafluorobutanesulfonate, and triphenylsulfonium. Trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, dimethyl (4-hydroxynaphthyl) sulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, monophenyldimethylsulfonium trifluorone methanesulfonate , Its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, diphenyl monomethyl Sulfonium trifluoromethanesulfonate, heptafluoropropane sulfonate or nonafluorobutane sulfonate, (4-methoxyphenyl) trifluoromethanesulfonate diphenylsulfonium, its like heptafluoropropane sulfonate or nonafluorobutane sulfonates.

  Specific examples of the oxime sulfonate acid generator include α- (p-toluenesulfonyloxyimino) -benzyl cyanide, α- (p-chlorobenzenesulfonyloxyimino) -benzyl cyanide, α- (4-nitrobenzenesulfonyl). Oxyimino) -benzylcyanide, α- (4-nitro-2-trifluoromethylbenzenesulfonyloxyimino) -benzylcyanide, α- (benzenesulfonyloxyimino) -4-chlorobenzylcyanide, α- (benzene Sulfonyloxyimino) -2,4-dichlorobenzylcyanide, α- (benzenesulfonyloxyimino) -2,6-dichlorobenzylcyanide, α- (benzenesulfonyloxyimino) -4-methoxybenzylcyanide, α- (2-Chlorobenzenesulfonyloxyimi ) -4-methoxybenzylcyanide, α- (benzenesulfonyloxyimino) -thien-2-ylacetonitrile, α- (4-dodecylbenzenesulfonyloxyimino) -benzylcyanide, α-[(p-toluenesulfonyloxy) Imino) -4-methoxyphenyl] acetonitrile, α-[(dodecylbenzenesulfonyloxyimino) -4-methoxyphenyl] acetonitrile, α- (tosyloxyimino) -4-thienyl cyanide, α- (methylsulfonyloxyimino) -1 -Cyclopentenylacetonitrile, α- (methylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (methylsulfonyloxyimino) -1-cycloheptenylacetonitrile, α- (methylsulfonyloxyimino) -1-cycloo Tenenyl 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-cycl Lopentenylacetonitrile, 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)- - methoxyphenyl acetonitrile, alpha-(propylsulfonyl oxyimino)-p-methylphenyl acetonitrile, alpha-like (methylsulfonyloxyimino)-p-bromophenyl acetonitrile. Of these, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile is preferred.

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

  As another acid generator (B-2), these may be used individually by 1 type and may be used in combination of 2 or more type.

As for content of (B) component, 0.1-60 mass parts is preferable with respect to 100 mass parts of (A) component, and 0.5-30 mass parts is more preferable. 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.
In the present invention, even if the content of the component (B) is 10 parts by mass or more with respect to 100 parts by mass of the component (A), the resolution and pattern shape are not adversely affected. ) Component can be blended at a high concentration, which is expected to further increase the sensitivity of the positive resist composition. In general, the blending amount of the component (B) in the resist composition is less than about 10 parts by mass with respect to 100 parts by mass of the component (A) in consideration of the effect on the resolution and pattern shape. It is said that.

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

<(D) component>
In the positive resist composition of the present invention, a nitrogen-containing organic compound (D) (hereinafter referred to as “component (D)”) is further added as an optional component in order to improve the resist pattern shape, stability 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, secondary lower aliphatic amines and tertiary lower aliphatic amines are particularly 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.

<(E) component>
Further, for the purpose of preventing the sensitivity deterioration due to the blending of the component (D) and improving the resist pattern shape, the stability of standing, etc., an organic carboxylic acid or an oxo acid of phosphorus or a derivative thereof (E ) (Hereinafter referred to as component (E)). 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.

<Other optional components>
If desired, the positive resist composition of the present invention may further contain miscible additives such as an additional resin for improving the performance of the resist film, a surfactant for improving coatability, and a dissolution inhibitor. In addition, plasticizers, stabilizers, colorants, antihalation agents, and the like can be added as appropriate.

≪Resist pattern formation method≫
Using the positive resist composition of the present invention, a resist pattern can be formed by, for example, the following resist pattern forming method.
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. For example, the exposure is selectively performed by an electron beam drawing apparatus or the like. That is, after exposing through a mask pattern or drawing by directly irradiating an electron beam without passing through a mask pattern, PEB (post-exposure heating) is performed at a temperature of 70 to 150 ° C. for 40 to 500 seconds, preferably Apply for 60-400 seconds. Subsequently, this is developed using an alkaline developer, for example, an aqueous 0.1 to 10% by mass tetramethylammonium hydroxide solution. In this way, a resist pattern faithful to the mask pattern can be obtained.
An organic or inorganic antireflection film can be provided between the substrate and the coating layer of the resist composition.
The wavelength used for the exposure is not particularly limited, and ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray, etc. Can be done using radiation. In particular, the positive resist composition according to the present invention is effective for EB and EUV, particularly EB.

  As described above, according to the positive resist composition and the resist pattern forming method of the present invention, a resist pattern with excellent sensitivity can be formed.

Example 1
100 parts by mass of a resin represented by the following formula (1) (resin in which 45 mol% of hydroxyl groups of polyhydroxystyrene (PHS) (Mw 8000) are protected with ethoxyethyl) and 6 parts by mass of triphenylsulfonium-n-butane Sulfonate (TPS-NBS), 0.8 parts by mass of trioctylamine, 0.32 parts by mass of salicylic acid, and 0.06 parts by mass of XR-104 (manufactured by Dainippon Ink and Chemicals) A positive resist composition solution was prepared by dissolving in 900 parts by mass of a mixed solvent of monomethyl ether acetate (PM) / ethyl lactate (EL) / propylene glycol monomethyl ether (PE) = 30/20/50.

［式中、Ｒは水素原子であり、ｍ：ｌ＝５５：４５（モル比）である］

[Wherein R is a hydrogen atom, and m: l = 55: 45 (molar ratio)]

The obtained positive resist composition solution was uniformly applied on an 8-inch silicon substrate subjected to hexamethyldisilazane treatment at a film thickness of 300 nm, and baked at 100 ° C. for 90 seconds to form a film. The substrate was drawn with an electron beam drawing machine (Hitachi HL-800D, 70 kV acceleration voltage), baked at 110 ° C. for 90 seconds, and 2.38% tetramethylammonium hydroxide (TMAH) aqueous solution for 60 seconds. After developing, rinsing with pure water for 30 seconds, performing shake-off drying, heating was performed at 100 ° C. for 60 seconds to form a line-and-space 1: 1 (LS) resist pattern.
When the obtained resist pattern was observed by SEM, the optimum exposure (sensitivity) at 300 nm LS was 19 μC / cm ² .

Comparative Example 1
In Example 1 above, instead of 6 parts by mass of TPS-NBS, 8.43 parts by mass of triphenylsulfonium nonafluorobutanesulfonate (TPS-PFBS, equimolar to TPS-NBS of Example 1) was used. Prepared a positive resist composition solution in the same manner as in Example 1, formed a resist pattern under the same conditions as in Example 1, and evaluated it. The optimum exposure (sensitivity) at 300 nm LS was 25 μC. / Cm ² .

Example 2
In Example 1, 22% of the hydroxyl groups of the resin represented by the following formula (2) (styrene / hydroxystyrene copolymer (= 10/90 (molar ratio), Mw 8000)) is used as 1-adamant. A positive resist composition solution was prepared in the same manner as in Example 1 except that the resin was changed to a resin protected with a xylethyl group, and a resist pattern was formed under the same conditions as in Example 1 and evaluated. However, the optimum exposure (sensitivity) at 300 nm LS was 10 μC / cm ² .

［式中、Ｒは水素原子であり、ｍ：ｌ：ｎ＝７０：１０：２０（モル比）である］

[Wherein R is a hydrogen atom, and m: l: n = 70: 10: 20 (molar ratio)]

Comparative Example 2
In Example 2, instead of 6 parts by mass of TPS-NBS, 8.43 parts by mass of triphenylsulfonium nonafluorobutane sulfonate (TPS-PFBS, equimolar to TPS-NBS of Example 1) was used. When a positive resist composition solution was prepared in the same manner as in Example 1, a resist pattern was formed under the same conditions as in Example 1, and the evaluation was performed, the optimum exposure amount (sensitivity) at 300 nm LS was 16 μC / cm ² .

Example 3
In Example 1, the resin used was 28% of the hydroxyl groups of the resin represented by the following formula (3) (hydroxystyrene / 3-hydroxy-1-adamantyl acrylate copolymer (= 80/20, Mw8000). A positive resist composition solution was prepared in the same manner as in Example 1 except that the resin was changed to (resin protected with ethoxyethyl group), a resist pattern was formed under the same conditions as in Example 1, and the evaluation was performed. However, the optimum exposure (sensitivity) at 300 nm LS was 14 μC / cm ² .

［式中、Ｒは水素原子であり、ｍ：ｌ：ｎ：ｏ＝５５．２：１６．６：２４．８：３．４（モル比）である］

[Wherein, R is a hydrogen atom, and m: l: n: o = 55.2: 16.6: 24.8: 3.4 (molar ratio)]

Comparative Example 3
In Example 3, instead of 6 parts by mass of TPS-NBS, 8.43 parts by mass of triphenylsulfonium nonafluorobutanesulfonate (TPS-PFBS, equimolar to TPS-NBS of Example 1) was used. A positive resist composition solution was prepared in the same manner as in Example 1, a resist pattern was formed under the same conditions as in Example 1, and the evaluation was performed. The optimum exposure (sensitivity) at 300 nm LS was 27 μC / cm ² .

  The results of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1.

Comparing Example 1 and Comparative Example 1, in Example 1, the optimum exposure amount (sensitivity) at 300 nm LS was improved by 24%.
Comparing Example 2 and Comparative Example 2, in Example 2, the optimum exposure amount (sensitivity) at 300 nm LS was improved by 38%.
When Example 3 was compared with Comparative Example 3, in Example 3, the optimum exposure amount (sensitivity) at 300 nm LS was improved by 48%.

Claims (17)

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 (a2) is represented by 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. ]
Having an acid dissociable, dissolution inhibiting group (II) represented by
The acid generator component (B) is represented by the following general formula (B-1)

[Wherein, R ¹⁰ represents an alkyl group or a cycloalkyl group. ]
A positive resist composition comprising an onium salt-based acid generator (B-1) having a sulfonate ion represented by an anion as an anion. The onium salt acid generator (B-1) is represented by the following general formula (B-11).

[In formula, R < ¹¹ > -R < ¹³ > represents an aryl group or an alkyl group each independently, and q is an integer of 1-10. ]
The positive resist composition according to claim 1, comprising an onium salt represented by the formula: The acid dissociable, dissolution inhibiting group (II) is represented by the following general formula (II-1)

[Wherein, R ¹ represents an alkyl group having 1 to 5 carbon atoms, and Y represents an aliphatic cyclic group or 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 claim 1, wherein at least one of the structural units (a1) and (a2) contains a polycyclic group. The structural unit (a1) is represented by the following general formula (I):

[Wherein, R represents a hydrogen atom or a methyl group. ]
The positive resist composition as described in any one of Claims 1-4 containing the structural unit (a11) represented by these.   The said structural unit (a1) contains the structural unit (a12) induced | guided | derived from the aliphatic polycyclic group containing (meth) acrylic acid ester which has an alcoholic hydroxyl group. A positive resist composition.   The positive resist composition according to claim 6, wherein the structural unit (a12) is a structural unit derived from an adamantyl group-containing (meth) acrylic acid ester having an alcoholic hydroxyl group. The resin component (A) is further represented by the following general formula (III)

[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. ]
The positive resist composition as described in any one of Claims 1-7 which has a structural unit (a3) represented by these.   The resin component (A) is a polymer (A1) having the structural unit (a11) and a structural unit (a21) in which the hydroxyl group of the structural unit (a11) is protected by an acid dissociable, dissolution inhibiting group. The positive resist composition according to any one of claims 5 to 8.   The positive resist composition according to claim 9, wherein the proportion of the structural unit (a21) in the polymer (A1) is 5 to 35 mol% with respect to all the structural units constituting the polymer (A1).   The positive resist composition according to claim 9 or 10, wherein the polymer (A1) further comprises the structural unit (a3).   The resin component (A) includes the structural unit (a11), the structural unit (a12), and a structural unit (a21) in which the hydroxyl groups of the structural unit (a11) are protected by an acid dissociable, dissolution inhibiting group. It is a polymer (A2) which has at least one of the structural unit (a22) formed by protecting the alcoholic hydroxyl group of the structural unit (a12) with an acid dissociable, dissolution inhibiting group. The positive resist composition as described in 1. above.   In the polymer (A2), the structural unit (a21) and the structural unit (a11), the structural unit (a12), the structural unit (a21), and the structural unit (a22) with respect to the total of the structural unit (a22) The positive resist composition according to claim 12, wherein the total ratio of a22) is 10 to 35 mol%.   In the polymer (A2), the molar ratio of the total of the structural unit (a11) and the structural unit (a21) to the total of the structural unit (a12) and the structural unit (a22) is 95: 5-75. The positive resist composition according to claim 12 or 13, wherein: 25.   The positive resist composition according to any one of claims 12 to 14, wherein the acid dissociable, dissolution inhibiting group is a 1-alkoxyalkyl group.   Furthermore, the positive resist composition as described in any one of Claims 1-15 containing a nitrogen-containing organic compound (D). A step of forming a resist film on a substrate using the positive resist composition according to any one of claims 1 to 16, a step of exposing the resist film, and developing the resist film to form a resist pattern A resist pattern forming method including the step of: