JP4409366B2 - Positive resist composition and resist pattern forming method - Google Patents

Description

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

In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, 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, conventionally, 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 (hereinafter referred to as PAG) that generates acid upon exposure is known. There are a positive type in which the alkali solubility in the exposed area increases and a negative type in which the alkali solubility in the exposed area decreases.

Up to now, as the base resin for chemically amplified resist, polyhydroxystyrene (PHS), which is highly transparent to KrF excimer laser (248 nm), and a resin whose hydroxyl group is protected with an acid dissociable, dissolution inhibiting group (PHS resin) Has been used. However, since the PHS resin has an aromatic ring such as a benzene ring, the transparency to light having a wavelength shorter than 248 nm, for example, 193 nm, is not sufficient. Therefore, a chemically amplified resist having a PHS-based resin as a base resin component has drawbacks such as low resolution in a process using 193 nm light, for example.
Therefore, as a resist base resin currently used in ArF excimer laser lithography and the like, since it has excellent transparency near 193 nm, a resin (acrylic resin) having a structural unit derived from (meth) acrylic ester is used. Resin) is mainly used.

However, the acrylic resin tends to be inferior in etching resistance due to its structure as compared with the conventional base resin such as the PHS resin. Therefore, for example, when dry etching is performed after the resist pattern is formed, there is a problem that the surface of the resist film is roughened.
In general, the etching resistance of acrylic resins is improved by using a polycyclic alicyclic group such as an adamantyl group as a substituent of the ester portion of (meth) acrylic acid ester (see, for example, Patent Document 1).
However, changes in substituents greatly affect lithography properties such as resolution, so it is very difficult to optimize them to suit resists, and etching resistance due to such changes in substituents There is a limit to the improvement.

On the other hand, as a base resin that can be used for ArF excimer laser lithography or the like, a resin whose main chain is composed of structural units having a cyclic structure, for example, a monocyclic structural unit whose main chain is derived from maleic anhydride, norbornene Resins composed of cyclic structural units such as structural units derived from polycyclic olefins have been proposed (see, for example, Patent Document 2).
However, although a resist using such a main chain ring type resin is excellent in etching resistance, the resulting resist pattern has a poor shape compared to the case of using an acrylic resin. For example, the resist pattern has a T-top shape. And the resist pattern side wall is tapered and roughness occurs. In addition, lithography properties such as resolution and depth of focus are not sufficient.
Therefore, there is a demand for a positive resist composition that can form a resist pattern that is excellent in resolution, shape, and etching resistance.
Japanese Patent No. 2881969 JP 2000-235263 A

  The present invention has been made in view of the above circumstances, and provides a positive resist composition and a resist pattern forming method capable of forming a resist pattern having high resolution and excellent shape and etching resistance. For the purpose.

［式（ａ−１）中、Ｒ ^１ は炭素数２以上のアルキル基であり、ｓは０または１であり、ｔは１〜３の整数である。］

［式（ａ−２）中、Ｒ ^２ 、Ｒ ^３ は、それぞれ独立に、水素原子または低級アルキル基であり、ｓは０または１である。］

［式（ａ−３）中、Ｒ ^４ はアルカリ可溶性基を有する有機基であり、ｓは０または１である。］
また、本発明のレジストパターン形成方法は、上記本発明のポジ型レジスト組成物を支持体上に塗布し、選択的に露光し、次いで現像してレジストパターンを形成することを特徴とする。 As a result of intensive studies, the present inventors have found that the above problems can be solved by using a mixture of two specific polymers as the base resin of the positive resist composition, and have completed the present invention. .
That is, the positive resist composition of the present invention comprises a resin (A) having an acid dissociable, dissolution inhibiting group and increased alkali solubility by the action of an acid, and a compound (B) that generates an acid upon irradiation with radiation. Wherein the resin (A) is a structural unit derived from a main chain cyclic polymer (A1) and (meth) acrylic acid ester and / or (meth) acrylic acid ( a ') Ri mixture der polymer with (A2) consisting only,
The main chain cyclic polymer (A1) is a structural unit (a1) represented by the following general formula (a-1), a structural unit (a2) represented by the following general formula (a-2), and the following general Having a structural unit (a3) represented by the formula (a-3);
The polymer (A2) is a structural unit (a′1) derived from a (meth) acrylic acid ester having an acid dissociable, dissolution inhibiting group, or a structural unit derived from a (meth) acrylic acid ester having a lactone ring. It has a structural unit (a′3) derived from (a′2) and a (meth) acrylic acid ester containing a polar group-containing aliphatic hydrocarbon group .

[In Formula (a-1), R ¹ is an alkyl group having 2 or more carbon atoms, s is 0 or 1, and t is an integer of 1 to 3. ]

[In Formula (a-2), R ² and R ³ each independently represent a hydrogen atom or a lower alkyl group, and s is 0 or 1. ]

[In formula (a-3), R ⁴ is an organic group having an alkali-soluble group, and s is 0 or 1. ]
The resist pattern forming method of the present invention is characterized in that the positive resist composition of the present invention is applied onto a support, selectively exposed, and then developed to form a resist pattern.

In the present invention, “structural unit” means a monomer unit constituting a polymer. “(Meth) acrylic acid ester” means one or both of methacrylic acid ester and acrylic acid ester. “(Meth) acrylic acid” means one or both of methacrylic acid and acrylic acid. The “structural unit derived from (meth) acrylic acid ester and / or (meth) acrylic acid” means that the ethylenic double bond of (meth) acrylic acid ester and / or (meth) acrylic acid is cleaved. Means a structural unit.
In addition, “exposure” is a concept including general radiation irradiation.

  The present invention provides a positive resist composition that can form a resist pattern having high resolution and excellent shape and etching resistance.

Hereinafter, the present invention will be described in more detail.
The positive resist composition of the present invention has a resin (A) (hereinafter referred to as component (A)) having an acid dissociable, dissolution inhibiting group and increased alkali solubility by the action of an acid, and radiation irradiation (exposure). And a compound that generates an acid (hereinafter referred to as component (B)).
Since the component (A) has an acid dissociable, dissolution inhibiting group, it is insoluble in alkali before exposure. When an acid generated from the component (B) is acted upon by exposure, the acid dissociable, dissolution inhibiting group is dissociated. (A) The alkali solubility of the whole component increases. Therefore, in the formation of a resist pattern, when selective exposure is performed on the resist or post-exposure heating (PEB) is performed in addition to exposure, the exposed portion turns into alkali-soluble while the unexposed portion is alkali-insoluble. Thus, a positive resist pattern can be formed by alkali development.

Component (A) Component (A) is derived from main chain cyclic polymer (A1) (hereinafter sometimes referred to as polymer (A1)) and (meth) acrylic acid ester and / or (meth) acrylic acid. And a polymer (A2) consisting only of the structural unit (a ′).

In the present invention, it is necessary that at least one of the polymer (A1) and the polymer (A2) has an acid dissociable, dissolution inhibiting group. In particular, it is preferable that both the polymer (A1) and the polymer (A2) have an acid dissociable, dissolution inhibiting group because of excellent resist pattern shape, resolution, and the like. Of these, it is preferable that both polymers have an acid dissociable, dissolution inhibiting group having the same structure, since the above effects are further excellent. This is because the acid dissociable, dissolution inhibiting group is the same as the acid dissociable, dissolution inhibiting group of the structural unit (a1) in the polymer (A1), so that in the lithography step, the acid dissociable, dissolution inhibiting group of each polymer. Can be dissociated under substantially the same conditions.
Similarly, it is preferable that at least one of the polymer (A1) and the polymer (A2) has a structural unit having a lactone ring because of good resolution, adhesion to a substrate, and the like. In particular, it is preferable that both the polymer (A1) and the polymer (A2) have a structural unit having a lactone ring because this effect is excellent. Of these, it is preferable that both polymers have a lactone ring having the same structure, since the above effect is further improved and the lithography properties such as the depth of focus are also excellent. This is because the structure of the lactone ring of the structural unit (a2) in the polymer (A1) is the same as the structure of the lactone ring of the structural unit (a′2) in the polymer (A2). The difference between the properties of the polymer (A1) and the polymer (A2), for example, the glass transition temperature (Tg) and the affinity for the developer is reduced, and the lithography conditions (baking temperature, etc.) for each polymer alone. It is presumed that the optimal condition of

Hereinafter, each polymer will be described in detail.
[Polymer (A1)]
In the present invention, the “main chain cyclic polymer” means that the constituent unit constituting the polymer has a monocyclic or polycyclic ring structure, and preferably at least one on the ring of the ring structure, preferably Means that two or more carbon atoms have structural units constituting the main chain (hereinafter referred to as main chain cyclic structural units). By containing the polymer (A1) having such a structure, Excellent etching resistance. This is presumably because the carbon density is increased by having the main chain cyclic structural unit.

As the main chain cyclic structural unit, structural units represented by the following general formula, such as structural units (a1) to (a3) described later, that is, bicyclo [2.2.1] -2-heptene (norbornene), Tetracyclo [4.4.0.1 ^2.5 . 1. ^7.10 ] structural units derived from polycyclic olefins (hereinafter referred to as polycycloolefins) such as 3-dedecene, and the anhydride-containing structural units of dicarboxylic acids mentioned in the structural unit (a4) described later. Can be mentioned. Among these, it is preferable to have a structural unit derived from a polycycloolefin in the main chain because the etching resistance when used as a resist is particularly excellent.

［式中、ｓは０または１である。］

[Wherein s is 0 or 1; ]

  The polymer (A1) has, in addition to the main chain cyclic structural unit, structural units derived from (meth) acrylic acid esters and / or (meth) acrylic acid esters mentioned in the later-described polymer (A2). However, for the effect of the present invention, in the polymer (A1), the main chain cyclic structural unit is contained in an amount of 50 to 100 mol% with respect to all the structural units constituting the polymer (A1). It is preferable that it is 80-100 mol%.

・ Structural unit (a1)
The polymer (A1) preferably has a structural unit (a1) represented by the following general formula (a-1) because the resolution is improved.

［式（ａ−１）中、Ｒ^１は炭素数２以上のアルキル基であり、ｓは０または１であり、ｔは１〜３の整数である。］

[In Formula (a-1), R ¹ is an alkyl group having 2 or more carbon atoms, s is 0 or 1, and t is an integer of 1 to 3. ]

In the structural unit derived from polycycloolefin, the structural unit (a1) represented by the general formula (a-1) is the 5-position (when s = 0) or the 8-position (s = 1) on the ring. In this case, 1-alkyl (R ¹ in formula (a-1); 2 or more carbon atoms) -1-cycloalkyl (5 to 8 carbon atoms) oxycarbonyl group as a substituent.
The reason why the resolution is improved is that the 1-alkyl-1-cycloalkyl group portion of this substituent is an acid dissociable, dissolution inhibiting group, and the 1-alkyl alkyl group has 2 or more carbon atoms. Therefore, for example, it is presumed that the acid dissociable, dissolution inhibiting group is easily dissociated as compared with the case where the alkyl group is a methyl group, thereby improving the resolution.
Further, by having a cycloalkyl group which is a monocyclic alicyclic group, for example, the polymer (A1) has a lower hydrophobicity than when the acid dissociable, dissolution inhibiting group contains a polycyclic group such as adamantyl. When the polymer (A1) is used as a resist composition, the affinity between the resist film obtained using the resist composition and the alkali developer increases, and the resist pattern obtained It is estimated that the resolution is improved.
Further, the etching resistance of the resist pattern is improved as compared with the case where the acid dissociable, dissolution inhibiting group has a structure that does not contain a ring such as a chain tertiary alkyl group.

In formula (a-1), R ¹ is an alkyl group having 2 or more carbon atoms, which may be linear or branched, and is preferably a lower alkyl group having 2 to 5 carbon atoms, such as an ethyl group, a propyl group, an isopropyl group, Examples include n-butyl group, isobutyl group, pentyl group, isopentyl group, neopentyl group and the like. Preferably it is an ethyl group.
s is 0 or 1, and is preferably 0 in view of industrial availability.
t is an integer of 1 to 3, and is preferably 2 in view of easy synthesis and industrial availability.
In the present invention, it is particularly preferable that R ¹ in the formula (a-1) is an ethyl group and t is 2. That is, it is preferable to have a 1-ethyl-1-cyclohexyl group as the acid dissociable, dissolution inhibiting group because the above effect is particularly excellent.

As the structural unit (a1), one type may be used alone, or two or more types may be used in combination.
10-80 mol% is preferable with respect to the sum total of all the structural units of the polymer for resist compositions of this invention, and the ratio of a structural unit (a1) in a polymer (A1) is 30-60 mol% more. preferable. By setting it to the lower limit value or more, a pattern can be obtained when the resist composition is used, and by setting it to the upper limit value or less, it is possible to balance with other structural units.

  The monomer for deriving the structural unit (a1) is, for example, (meth) acrylic acid-1-alkyl (2 or more carbon atoms) -1-cycloalkyl (carbon number) as described in JP-A No. 2000-235263. 5-8) It can be synthesized by reacting an ester with cyclopentadiene or dicyclopentadiene by a Diels-Alder reaction which is a known reaction.

・ Structural unit (a2)
In addition to the structural unit (a1), the polymer (A1) preferably further has a structural unit (a2) represented by the following general formula (a-2).
When the polymer (A1) has the structural unit (a2), the resolution is further improved. This is because the structural unit (a2) increases the hydrophilicity of the entire polymer (A1), and when the polymer (A1) is used as a resist composition, a resist film and an alkaline developer obtained using the resist composition are used. This is presumed to be due to increased affinity.

［式（ａ−２）中、Ｒ^２、Ｒ^３は、それぞれ独立に、水素原子または低級アルキル基であり、ｓは０または１である。］

[In Formula (a-2), R ² and R ³ each independently represent a hydrogen atom or a lower alkyl group, and s is 0 or 1. ]

In the structural unit derived from polycycloolefin, the structural unit (a2) represented by the general formula (a-2) is a 5-position (when s = 0) or an 8-position (s = 1) on the ring. A group obtained by removing one hydrogen atom from butyrolactone having the groups R ² and R ³ .
In formula (a-2), s is the same as s in formula (a-1).
R ² and R ³ are each independently a hydrogen atom or a lower alkyl group, and a hydrogen atom is preferable in view of industrial availability.
The lower alkyl group for R ² and R ³ may be linear or branched and is preferably an alkyl group having 1 to 5 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, or an isobutyl group. , A pentyl group, an isopentyl group, a neopentyl group, and the like.

As the structural unit (a2), one type may be used alone, or two or more types may be used in combination.
In the polymer (A1), the proportion of the structural unit (a2) is preferably 10 to 80 mol%, more preferably 30 to 60 mol%, based on the total of all the structural units of the polymer (A1). By setting it to the lower limit value or more, the effect of improving the resolution is excellent, and by setting the upper limit value or less, it is possible to balance with other structural units.

  In the polymer (A1), the total of the structural units (a1) and (a2) is preferably 20 to 90 mol% based on the total of all the structural units of the polymer (A1), 80 mol% is more preferable.

・ Structural unit (a3)
The polymer (A1) preferably further has a structural unit (a3) represented by the following general formula (a-3) in addition to the structural units (a1) and (a2).

［式（ａ−３）中、Ｒ^４はアルカリ可溶性基を有する有機基であり、ｓは０または１である。］

[In formula (a-3), R ⁴ is an organic group having an alkali-soluble group, and s is 0 or 1. ]

In formula (a-3), s is the same as s in formula (a-1).
R ⁴ is an organic group having an alkali-soluble group.

Examples of the alkali-soluble group in R ⁴ include a group having a pKa comparable to that of a phenolic hydroxyl group, and a group having an alkali-soluble group such as an alcoholic hydroxyl group or a carboxyl group. That is, it is a group having a small pKa (not particularly limited, but preferably a group having a pKa in the range of 6 to 12, for example).
By having an alkali-soluble group, an appropriate acidity can be imparted to the polymer (A1), which increases the hydrophilicity of the entire polymer (A1) and, like the structural unit (a2), resolves. It is presumed that it contributes to the performance improvement effect. In addition, by having the structural unit (a3), the adhesion to the substrate when the resist is formed is improved, and for example, pattern collapse when a line and space pattern is formed can be reduced.

More specifically, R ⁴ includes, for example, an alcoholic hydroxyl group whose bonding position is not particularly limited; a hydroxyalkyl group in which the α-position carbon atom of the alcoholic hydroxyl group is substituted with an electron-withdrawing group; a carboxyl group, and the like. . Of these, a hydroxyalkyl group in which the α-position carbon atom of the alcoholic hydroxyl group is substituted with an electron-withdrawing group or a carboxyl group is preferable.
In the hydroxyalkyl group in which the α-position carbon atom of the alcoholic hydroxyl group is substituted with an electron-withdrawing group, examples of the electron-withdrawing group include a halogen atom or a halogenated alkyl group.
Examples of the halogen atom include a fluorine atom and a chlorine atom, and a fluorine atom is preferable.
In the halogenated alkyl group, the halogen is the same as the halogen atom. The alkyl group is preferably a lower alkyl group having, for example, about 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group, and most preferably a methyl group. Specific examples include a trifluoromethyl group, a difluoromethyl group, a monofluoromethyl group, a perfluoroethyl group, and the like, and a trifluoromethyl group is particularly preferable.
The number of electron-withdrawing groups is 1 or 2, preferably 2.

More specifically and preferably, the hydroxyalkyl group in which the α-position carbon atom of the alcoholic hydroxyl group is substituted with an electron-withdrawing group has a —CR ³¹ R ³² OH group, and R ³¹ and R ³² are: Each independently represents an alkyl group, a halogen atom, or a halogenated alkyl group, and at least one of them can be represented as an electron-withdrawing group selected from a halogen atom or a halogenated alkyl group.
The halogen atom or halogenated alkyl group here is the same as described above, and examples of the alkyl group include lower alkyl groups such as a methyl group, an ethyl group, and a propyl group.
Among these, those in which the electron-withdrawing group is a fluorine atom or a fluorinated alkyl group are preferable, and those in which R ³¹ and R ³² are both fluorinated alkyl groups are particularly preferable.

As R ⁴ , a group represented by the following general formula (a-4) is particularly preferable because the shape of the resulting resist pattern is excellent with reduced roughness and the like.

In formula (a-4), p is an integer of 1 to 5, more preferably an integer of 1 to 3, and most preferably 1.
M and n are each independently an integer of 1 to 5, more preferably an integer of 1 to 3, and particularly those in which m and n are 1 are excellent in synthesis and effect. It is preferable.

As the structural unit (a3), one type may be used alone, or two or more types may be used in combination.
In the polymer (A1) of the present invention, the proportion of the structural unit (a3) is preferably from 5 to 40 mol%, more preferably from 10 to 30 mol%, based on the total of all the structural units of the polymer (A1). . By setting it to the lower limit value or more, the effect of improving the resolution and adhesion to the substrate is excellent, and by setting the upper limit value or less, it is possible to balance with other structural units.

・ Other structural units (a4)
The polymer (A1) may contain a structural unit (a4) other than the structural units (a1) to (a3) as long as the effects of the present invention are not impaired.
As the structural unit (a4), other structural units not classified into the above structural units (a1) to (a3), which are copolymerizable with monomers derived from the structural units (a1) to (a3) There is no particular limitation as long as it is a derived structural unit.
As the structural unit (a4), a structural unit derived from a known compound having an ethylenic double bond can be arbitrarily used depending on the purpose.

  More specifically, as the structural unit (a4), for example, a structural unit (a ′) derived from a (meth) acrylic acid ester and / or a (meth) acrylic acid ester mentioned in the polymer (A2) described later, Examples include a dicarboxylic acid anhydride-containing structural unit, a structural unit derived from a polycycloolefin having no substituent, and a structural unit derived from a polycycloolefin having a polycyclic alicyclic group as a substituent. .

  The acid anhydride-containing structural unit of dicarboxylic acid refers to a structural unit having a —C (O) —O—C (O) — structure. Examples of such include structural units containing monocyclic or polycyclic cyclic acid anhydrides, and more specifically, monocyclic or polycyclic compounds represented by the following [Chemical Formula 6]. Examples thereof include units derived from maleic anhydride and units derived from itaconic acid shown in the following [Chemical Formula 7].

As structural units derived from polycycloolefin, bicyclo [2.2.1] -2-heptene (norbornene), tetracyclo [4.4.0.1 ^2.5 . 1. ^7.10 ] -3-dodecene and the like.
Examples of the substituent on the ring include a tricyclodecanyl group, an adamantyl group, and a tetracyclododecanyl group.

In the polymer (A1), the combination and ratio of the structural units such as the structural units (a1) to (a4) can be appropriately adjusted depending on required characteristics. In consideration of lithography properties such as the shape of the resist pattern to be obtained, etching resistance, and resolution, it is preferable to have structural units (a1) and (a2), and further have structural units (a1) to (a3). It is preferable.
When the polymer (A1) is a binary polymer containing the structural unit (a1) and the structural unit (a2) and not containing the structural unit (a3) (however, the structural unit (a4) may be included) The proportion (molar ratio) of each structural unit is 10 in the structural unit (a1) relative to all the structural units constituting the polymer (A1) in that the effects of the present invention and the control in the synthesis of the polymer are easy. It is preferably ˜80 mol%, more preferably 30 to 60 mol%, the structural unit (a2) is preferably 10 to 80 mol%, and more preferably 30 to 60 mol%. .
In the case where the polymer (A1) is a ternary polymer containing the structural unit (a3) in addition to the structural unit (a1) and the structural unit (a2) (however, the structural unit (a4) may be included). The proportion (molar ratio) of each constitutional unit is preferably 10 to 80 mol%, and preferably 30 to 60 mol%, of the constitutional unit (a1) with respect to all the constitutional units constituting the polymer (A1). More preferably, the structural unit (a2) is preferably 10 to 80 mol%, more preferably 30 to 60 mol%, and the structural unit (a3) is preferably 5 to 40 mol%. 10 to 30 mol% is more preferable. As a result, the etching resistance and the resist pattern shape are excellent, and the lithography properties such as resolution are also excellent.

  A preferred specific example of the polymer (A1) is a polymer (A11) represented by the following general formula (a-11). This polymer (A11) is excellent in etching resistance and resist pattern shape, is excellent in lithography properties such as resolution, is excellent in adhesion to the substrate, and does not easily cause pattern collapse.

  The polymer (A1) can be obtained, for example, by polymerizing a monomer related to each structural unit by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN). .

The polymer (A1) has a mass average molecular weight (polystyrene equivalent mass average molecular weight by gel permeation chromatography, the same shall apply hereinafter) of preferably 15,000 or less, and more preferably 10,000 or less. When the mass average molecular weight is 15000 or less, there are advantages such as excellent etching resistance, resist pattern swelling during development, and pattern collapse.
The lower limit is not particularly limited, but is preferably 3000 or more and more preferably 5000 or more in consideration of resolution, solubility in an organic solvent, and the like.

  A polymer (A1) can be comprised from 1 type, or 2 or more types of polymers.

[Polymer (A2)]
The polymer (A2) consists only of the structural unit (a ′) derived from (meth) acrylic acid ester and / or (meth) acrylic acid.
Here, the “structural unit (a ′) derived from (meth) acrylic acid ester and / or (meth) acrylic acid” means that in the following general formula, R is a hydrogen atom and X is a monovalent organic group. A structural unit derived from an acrylate ester, a structural unit derived from a methacrylic acid ester in which R is a methyl group and X is a monovalent organic group, and acrylic acid in which R and X are hydrogen atoms And one or more structural units selected from the group consisting of structural units derived from methacrylic acid wherein R is a methyl group and X is a hydrogen atom.
Further, “consisting only of the structural unit (a ′)” means that the main chain of the polymer (A2) is composed of only the structural unit (a ′) and does not include other structural units. .

［式中、Ｒは水素原子またはメチル基であり、Ｘは水素原子または１価の有機基である］

[Wherein, R is a hydrogen atom or a methyl group, and X is a hydrogen atom or a monovalent organic group]

  In the above formula, the monovalent organic group in X is not particularly limited. For example, in the structural units mentioned in the structural units (a′1) to (a′4) described later, the (meth) acrylic acid ester Examples include a group bonded to an ester side chain (an acid dissociable, dissolution inhibiting group, a group having a lactone ring, a polar group-containing aliphatic hydrocarbon group, a polycyclic aliphatic hydrocarbon group, and the like).

・ Structural unit (a'1)
The structural unit (a ′) preferably has a structural unit (a′1) derived from a (meth) acrylic acid ester containing an acid dissociable, dissolution inhibiting group.
The acid dissociable, dissolution inhibiting group in the structural unit (a′1) is not particularly limited. In general, those that form a cyclic or chain tertiary alkyl ester with a carboxyl group of (meth) acrylic acid are widely known, but particularly excellent in dry etching resistance and resist pattern formation. Therefore, a monocyclic or polycyclic alicyclic group-containing acid dissociable, dissolution inhibiting group is preferably used.
Examples of the monocyclic alicyclic group include groups in which one hydrogen atom has been removed from a monocycloalkane such as cyclohexane or cyclopentane.
Examples of the polycyclic alicyclic group include groups in which one or two hydrogen atoms have been removed from a polycycloalkane such as bicycloalkane, tricycloalkane, and tetracycloalkane. Specifically, adamantane , Groups obtained by removing one or two hydrogen atoms from a polycycloalkane such as norbornane, isobornane, tricyclodecane, and tetracyclododecane.
Such a monocyclic or polycyclic alicyclic group can be appropriately selected and used from among many proposed resin components of resist compositions for ArF excimer lasers, for example.
Among these, a cyclohexyl group, a cyclopentyl group, an adamantyl group, a norbornyl group, and a tetracyclododecanyl group are preferable from the viewpoint of easy industrial availability.

  More specifically, the structural unit (a′1) has a monocyclic alicyclic group-containing acid dissociable, dissolution inhibiting group such as a structural unit represented by the following general formula (a-5) (meth) A structural unit derived from an acrylate ester, a polycyclic alicyclic group-containing acid dissociable, dissolution inhibiting group such as a structural unit represented by the following general formulas (I), (II), and (III) (meta ) Constituent units derived from acrylic acid esters.

［式（ａ−５）中、Ｒは水素原子またはメチル基であり、Ｒ^１は炭素数２以上のアルキル基であり、ｔは１〜３の整数である。］

[In Formula (a-5), R is a hydrogen atom or a methyl group, R ¹ is an alkyl group having 2 or more carbon atoms, and t is an integer of 1 to 3. ]

［式（Ｉ）中、Ｒは水素原子又はメチル基、Ｒ^１１は低級アルキル基である。］

[In the formula (I), R is a hydrogen atom or a methyl group, and R ¹¹ is a lower alkyl group. ]

［式（ＩＩ）中、Ｒは水素原子又はメチル基、Ｒ^２及びＲ^３はそれぞれ独立に低級アルキル基である。］

[In Formula (II), R is a hydrogen atom or a methyl group, and R ² and R ³ are each independently a lower alkyl group. ]

［式（ＩＩＩ）中、Ｒは水素原子又はメチル基、Ｒ^４は第３級アルキル基である。］

[In Formula (III), R is a hydrogen atom or a methyl group, and R ⁴ is a tertiary alkyl group. ]

In formula (a-5), R ¹ is preferably a lower linear or branched alkyl group having 1 to 5 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl. Group, pentyl group, isopentyl group, neopentyl group and the like. Among them, an alkyl group having 2 or more carbon atoms, preferably 2 to 5 carbon atoms is preferable, and in this case, acid dissociation tends to be higher than in the case of a methyl group. Industrially, a methyl group and an ethyl group are preferable.

In the formula (I), R ¹¹ is preferably a lower linear or branched alkyl group having 1 to 5 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, Examples thereof include a pentyl group, an isopentyl group, and a neopentyl group. Among them, an alkyl group having 2 or more carbon atoms, preferably 2 to 5 carbon atoms is preferable, and in this case, acid dissociation tends to be higher than in the case of a methyl group. Industrially, a methyl group and an ethyl group are preferable.

R ² and R ³ are each independently preferably a lower alkyl group having 1 to 5 carbon atoms. Such groups tend to be more acid dissociable than 2-methyl-2-adamantyl groups.
More specifically, R ² and R ³ are preferably each independently a lower linear or branched alkyl group similar to R ¹ . Among them, it is industrially preferable that both R ² and R ³ are methyl groups, and specifically, a structural unit derived from 2- (1-adamantyl) -2-propyl (meth) acrylate may be mentioned. it can.

R ⁴ is a tertiary alkyl group such as a tert-butyl group or a tert-amyl group, and a case where it is a tert-butyl group is industrially preferable.
In addition, the group —COOR ⁴ may be bonded to the 3 or 4 position of the tetracyclododecanyl group shown in the formula, but since these isomers are mixed, the bonding position cannot be specified. Similarly, the carboxyl group residue of (meth) acrylic acid ester is bonded to the position 8 or 9 shown in the formula, but the bonding position cannot be specified.

Among these, in particular, when the polymer (A1) is a polymer having the structural unit (a1), the structural unit represented by the formula (a-5) is particularly excellent in resolution and further has a depth of focus. It is preferable because it has excellent lithography properties such as the above. At this time, ^R 1, t of structural units represented by the formula (a-5) is more preferably the same as ^R 1, t the structural unit (a1).

  The structural unit (a′1) is 20 to 60 mol%, preferably 30 to 50 mol%, based on the total of all the structural units of the polymer (A2). By setting it to the lower limit value or more, a pattern can be obtained when the resist composition is used, and by setting it to the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a'2)
In the polymer (A2), the structural unit (a ′) further includes a structural unit (a′2) derived from a (meth) acrylic acid ester having a lactone ring in addition to the structural unit (a′1). It is preferable. As a result, the adhesion between the resist film and the substrate is enhanced, and even in a fine resist pattern, pattern collapse, film peeling, and the like are unlikely to occur. Further, the hydrophilicity of the polymer (A2) is increased, the affinity with the developer is increased, the alkali solubility in the exposed area is improved, and the resolution is improved.
Examples of the structural unit (a′2) include a structural unit in which a monocyclic group consisting of a lactone ring or a polycyclic alicyclic group having a lactone ring is bonded to the ester side chain portion of the (meth) acrylic acid ester. . At this time, the lactone ring indicates one ring containing an —O—C (O) — structure, and this is counted as the first ring. Therefore, here, in the case of only a lactone ring, it is called a monocyclic group, and when it has another ring structure, it is called a polycyclic group regardless of the structure.
Specific examples of the structural unit (a′2) include a monocyclic group obtained by removing one hydrogen atom from γ-butyrolactone, and a polycyclic group obtained by removing one hydrogen atom from a lactone ring-containing bicycloalkane. And cyclic groups.
Specifically, for example, a structural unit derived from a (meth) acrylic acid ester having a monocyclic group composed of a monocyclic lactone ring, such as a structural unit represented by the following general formula (a-6) And structural units derived from (meth) acrylic acid esters having a polycyclic alicyclic group having a lactone ring, such as structural units represented by formulas (IV) to (VII).

［式（ａ−６）中、Ｒは水素原子またはメチル基であり、Ｒ^２、Ｒ^３は、それぞれ独立に、水素原子または低級アルキル基である。］

[In formula (a-6), R represents a hydrogen atom or a methyl group, and R ² and R ³ each independently represent a hydrogen atom or a lower alkyl group. ]

（式中、Ｒは前記に同じであり、ｍは０又は１である。）

(In the formula, R is the same as above, and m is 0 or 1.)

（式中、Ｒは前記に同じである。）

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

（式中、Ｒは前記に同じである。）

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

Among these, in particular, when the polymer (A1) is a polymer having the structural unit (a2), the structural unit represented by the formula (a-6) is particularly excellent in resolution, and further has a depth of focus. It is preferable because it has excellent lithography properties such as the above. At this time, the formula (a-6) ^R 2 of structural units represented by, ^{R 3} is more preferably the same as ^R 2, ^{R 3} of the structural unit (a2).

  The structural unit (a′2) is preferably contained in an amount of 20 to 60 mol%, particularly 20 to 50 mol%, based on the total of all the structural units constituting the polymer (A2).

・ Structural unit (a'3)
In the polymer (A2), the structural unit (a ′) is a polar group-containing fat in addition to the structural unit (a′1) or in addition to the structural unit (a′1) and the structural unit (a′2). It is preferable to have a structural unit (a′3) derived from a (meth) acrylic acid ester containing a group hydrocarbon group. Thereby, the hydrophilicity of the polymer (A2) is increased, the affinity with the developer is increased, the alkali solubility in the exposed portion is improved, and the resolution is improved.
Examples of the polar group include a hydroxyl group and a cyano group, and a hydroxyl group is particularly preferable.
Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group (alkylene group) having 1 to 10 carbon atoms and a polycyclic aliphatic hydrocarbon group (polycyclic group). The polycyclic group can be appropriately selected from a large number of polycyclic groups similar to those exemplified in the structural unit (a′1).

  As the structural unit (a′3), when the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a linear or branched hydrocarbon group having 1 to 10 carbon atoms, hydroxy of (meth) acrylic acid A structural unit derived from an ethyl ester is preferred, and when the hydrocarbon group is a polycyclic group, structural units represented by the following [Chemical Formula 18] and [Chemical Formula 19] are preferred.

（式中、Ｒは前記に同じであり、ｎは１〜３の整数である。）

(In the formula, R is the same as above, and n is an integer of 1 to 3.)

  Among these, those in which n is 1 and the hydroxyl group is bonded to the 3-position of the adamantyl group are preferable.

（式中、Ｒは前記に同じであり、ｋは１〜３の整数である。）

(In the formula, R is the same as described above, and k is an integer of 1 to 3.)

  Among these, those in which k is 1 are preferable. These exist as a mixture of isomers (a mixture of compounds in which the cyano group is bonded to the 4-position or 5-position of the norbornanyl group).

  The structural unit (a′3) is contained in an amount of 10 to 50 mol%, preferably 20 to 40 mol%, based on the total of all the structural units constituting the polymer (A2).

<Structural unit (a′4), (a′5)>
The polymer (A2) is a structural unit derived from a (meth) acrylic ester containing a polycyclic aliphatic hydrocarbon group other than the structural units (a′1) to (a′3) ( a′4) or a structural unit (a′5) derived from (meth) acrylic acid may be included.
Here, “other than the structural units (a′1) to (a′3)” means that they do not overlap with these, and a polycyclic aliphatic hydrocarbon group (hereinafter simply referred to as a polycyclic group). Include a number of polycyclic groups similar to those in the structural units (a′1) to (a′3). In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, and a tetracyclododecanyl group is preferable in terms of industrial availability.
Specific examples of the structural unit (a′4) include those having the following structures (IX) to (XI).

（式中、Ｒは前記に同じである。）

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

（式中、Ｒは前記に同じである。）

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

（式中、Ｒは前記に同じである。）

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

The structural unit (a′4) is preferably contained in an amount of 1 to 25 mol%, more preferably 10 to 20 mol%, based on the total of all the structural units constituting the polymer (A2).
The structural unit (a′5) is preferably contained in an amount of 1 to 25 mol%, more preferably 10 to 20 mol%, based on the total of all the structural units constituting the polymer (A2).

  In the polymer (A2), the combination and ratio of the structural units such as the structural units (a′1) to (a′4) can be appropriately adjusted depending on required properties. In view of the shape, resolution, etc. of the resist pattern to be obtained, it is preferable to have the structural unit (a′1), the structural unit (a′2), and / or the structural unit (a′3). It is preferable to have all the units (a′1) to (a′3).

  A preferred specific example of the polymer (A2) is a polymer (A21) represented by the following general formula (a-21). This polymer (A21) is excellent in lithographic properties such as resolution and depth of focus, and the resulting resist pattern shape is also excellent in rectangularity, and the polymer (A1) and They are preferably used in combination.

［式（ａ−２１）中、Ｒは水素原子またはメチル基である。］

[In the formula (a-21), R represents a hydrogen atom or a methyl group. ]

  The polymer (A2) can be obtained, for example, by polymerizing a monomer related to each structural unit by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN). .

The polymer (A2) has a mass average molecular weight (polystyrene equivalent mass average molecular weight by gel permeation chromatography, the same shall apply hereinafter) of preferably 15,000 or less, and more preferably 10,000 or less. When the mass average molecular weight is 15000 or less, there are advantages such as excellent etching resistance, resist pattern swelling during development, and pattern collapse.
The lower limit is not particularly limited, but is preferably 3000 or more and more preferably 5000 or more in consideration of resolution, solubility in an organic solvent, and the like.

  A polymer (A2) can be comprised from 1 type, or 2 or more types of polymers.

  In the component (A), the mixing ratio (mass ratio) of the polymer (A1) and the polymer (A2) is not particularly limited. However, the higher the ratio of the polymer (A1), the better the etching resistance. The higher the ratio of the polymer (A2), the better the resist pattern shape tends to be, and it may be appropriately determined according to the performance to be obtained. In particular, for the effect of the present invention, it is preferably within a range of 1: 9 to 9: 1, more preferably within a range of 50:50 to 20:80, and 40:60 to 20: Most preferably, it is within the range of 80.

(B) component (B) A component is what is called an acid generator. In the present invention, the component (B) can be used without particular limitation from known acid generators used in conventional chemically amplified resist compositions.
Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, poly (bissulfonyl) diazomethanes, There are various known diazomethane acid generators such as diazomethane nitrobenzyl sulfonates, imino sulfonate acid generators and disulfone acid generators.

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

  Specific examples of the oxime sulfonate acid generator include α- (methylsulfonyloxyimino) -phenylacetonitrile, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (trifluoromethylsulfonyloxyimino)- Phenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (propylsulfonyloxyimino) -p-methylphenylacetonitrile, α- (methylsulfonyloxyimino) -p-bromophenylacetonitrile and the like can be mentioned. Of these, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile is preferred.

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

In the present invention, from the viewpoint of reactivity with the component (A), it is preferable to use an onium salt having a fluorinated alkyl sulfonate ion as the anion as the component (B).
As the component (B), one type of acid generator may be used alone, or two or more types may be used in combination.
(B) Content of a component is 0.5-30 mass parts with respect to 100 mass parts of (A) component, Preferably it is 1-10 mass parts. If the amount is less than the above range, pattern formation may not be sufficiently performed, and if the amount exceeds the above range, a uniform solution is difficult to obtain, which may cause a decrease in storage stability.

Component (D) The positive resist composition of the present invention further contains a nitrogen-containing organic compound (D) (hereinafter, (D ) Component)).
Since a wide variety of components (D) have already been proposed, any known one may be used, but amines, particularly secondary lower aliphatic amines and tertiary lower aliphatic amines are preferred. .
Here, the lower aliphatic amine means an alkyl or alkyl alcohol amine having 5 or less carbon atoms. Examples of the secondary and tertiary amines include trimethylamine, diethylamine, triethylamine, and di-n-propylamine. , Tri-n-propylamine, tripentylamine, diethanolamine, triethanolamine, triisopropanolamine and the like, and tertiary alkanolamines such as triethanolamine are particularly preferable.
These may be used alone or in combination of two or more.
(D) component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component.

Component (E) In addition, for the purpose of preventing sensitivity deterioration due to the blending with the component (D) and improving the resist pattern shape, retention stability, etc., an organic carboxylic acid or phosphorus oxoacid is further included as an optional component. Or its derivative (E) (henceforth (E) component) 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.

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

Organic solvent The positive resist composition of the present invention can be produced by dissolving the material in an organic solvent.
Any organic solvent may be used as long as it can dissolve each component to be used to form a uniform solution, and one or two kinds of conventionally known solvents for chemically amplified resists can be used. These can be appropriately selected and used.
For example, ketones such as γ-butyrolactone, acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, dipropylene glycol Or dipropylene glycol monoacetate monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether and other polyhydric alcohols and derivatives thereof, cyclic ethers such as dioxane, methyl lactate, lactic acid Ethyl (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxy Methyl propionate, esters such as ethyl ethoxypropionate can be exemplified.
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.
Further, a mixed solvent obtained by mixing propylene glycol monomethyl ether acetate (PGMEA) and a polar solvent is preferable, but the blending ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent. However, it is preferably within a range of 1: 9 to 9: 1, more preferably 2: 8 to 8: 2.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 2: 8 to 8: 2, more preferably 3: 7 to 7: 3.
In addition, as the organic solvent, a mixed solvent of at least one selected from PGMEA and EL and γ-butyrolactone is also preferable. In this case, the mixing ratio of the former and the latter is preferably 70:30 to 95: 5.
Although the amount of the organic solvent used is not particularly limited, it is a concentration that can be applied to a support such as a substrate, and is appropriately set according to the coating film thickness. It is used in a range of 2 to 20% by mass, preferably 5 to 15% by mass.

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

The support is not particularly limited, and a conventionally known one can be used. Examples thereof include a substrate for electronic parts and a substrate on which a predetermined wiring pattern is formed.
Examples of the substrate include a silicon wafer, a metal substrate such as copper, chromium, iron, and aluminum, and a glass substrate.
As a material for the wiring pattern, for example, copper, solder, chrome, aluminum, nickel, gold or the like can be used.

The wavelength used for exposure (irradiation of radiation) is not particularly limited. ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, It can be performed using radiation such as soft X-rays. The positive resist composition according to the present invention is particularly effective for an ArF excimer laser.

As described above, the resist pattern obtained by using the positive resist composition of the present invention has high etching resistance, the shape of the resist pattern is high, the pattern sidewall has high perpendicularity, and line edge roughness is reduced. High and excellent.
In particular, when both the polymer (A1) and the polymer (A2) have an acid dissociable, dissolution inhibiting group having the same structure (for example, the polymer (A1) has a structural unit (a1) and the polymer (A2) Is excellent in lithography characteristics such as resolution, linearity, depth of focus, exposure margin, and the like. This effect is obtained when both the polymer (A1) and the polymer (A2) have a lactone ring having the same structure (for example, the polymer (A1) has a structural unit (a2), and the polymer (A2) (When it has a structural unit represented by the formula (a-6)).

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

The monomer components used in this synthesis example are shown below.

 Synthesis Example 1 is described in J. Org. Photopolym. Sci. Technol. , Vol. 15, No. 4, 2002 (619). The method was used as a reference. Synthesis Example 2 is a general radical polymerization reaction.

Synthesis example 1
25.6 g of NBECH, 24.0 g of NBGBL and 11.0 g of NBFOH were dissolved in 75 ml of dichloromethane, and a catalyst prepared from 4.3 g of silver borofluoride and 2.0 g of allyl palladium chloride dimer was added dropwise thereto. . Stirring was performed for 24 hours to obtain a crude polymerization solution. The polymerization solution was purified by reprecipitation with n-heptane twice, and the precipitated resin was separated by filtration and dried under reduced pressure to obtain a white resin. This resin is referred to as a polymer 1 (the following general formula (1)). As a result of GPC (gel permeation chromatography) measurement, polymer 1 had a molecular weight (Mw) of 14300 and a dispersity (Mw / Mn) of 1.7. Moreover, as a result of measuring a carbon 13 nuclear magnetic resonance spectrum ( ¹³ C-NMR), the composition ratio was p: q: r = 40: 40: 20 (molar ratio).

Synthesis example 2
15.5 g of ECHMA, 13.6 g of GBLMA and 9.5 g of ADOHMA were dissolved in 200 ml of tetrahydrofuran (THF), and 1.64 g of azobisisobutyronitrile (AIBN) was added. After refluxing for 12 hours, the reaction solution was added dropwise to 2 L of n-heptane. The precipitated resin was separated by filtration and dried under reduced pressure to obtain a white powder resin. This resin is referred to as a polymer 2 (the following general formula (2)). As a result of the GPC measurement, the molecular weight (Mw) of the polymer 2 was 12000, and the degree of dispersion (Mw / Mn) was 1.8. Moreover, as a result of measuring a carbon 13 nuclear magnetic resonance spectrum ( ¹³ C-NMR), the composition ratio was p: q: r = 40: 40: 20 (molar ratio).

Example 1
As component (A), 25 parts by mass of polymer 1 obtained in Synthesis Example 1 and 75 parts by mass of polymer 2 obtained in Synthesis Example 2, and as component (B) diphenyl (4-methylphenyl) 2.0 parts by mass of sulfonium nonafluorobutane sulfonate and 0.8 parts by mass of tri- (4-tert-butylphenyl) sulfonium nonafluorobutane sulfonate, 0.25 part by mass of triethanolamine as component (D), -Dissolved in 25 parts by mass of butyrolactone and 1100 parts by mass of a mixed solvent of propylene glycol monomethyl ether acetate / ethyl lactate = 6/4 to prepare a positive resist composition.

Example 2
A positive resist composition was prepared in the same manner as in Example 1 except that 50 parts by mass of polymer 1 and 50 parts by mass of polymer 2 were used as the component (A).

Comparative Example 1
A positive resist composition was prepared in the same manner as in Example 1 except that 100 parts by mass of the polymer 2 was used as the component (A).

<Evaluation of positive resist composition>
Using the positive resist compositions prepared in Examples 1 and 2 and Comparative Example 1, a resist pattern was formed as follows, and the shape and lithography characteristics thereof were evaluated and the etching resistance was evaluated.
First, an organic antireflection film composition “ARC-29A” (trade name, manufactured by Brewer Science Co., Ltd.) was applied onto an 8-inch silicon wafer using a spinner, and baked on a hot plate at 215 ° C. for 60 seconds. By drying, an organic antireflection film having a thickness of 77 nm was formed.
Then, the positive resist composition obtained above was applied onto an antireflection film using a spinner, pre-baked (PAB) at 100 ° C. for 90 seconds on a hot plate, and dried to have a film thickness of 250 nm. A resist film was formed.
Subsequently, ArF excimer laser (193 nm) was selectively irradiated through the mask pattern by an ArF exposure apparatus NSR-S302 (manufactured by Nikon Corporation; NA (numerical aperture) = 0.60, 2/3 ring zone).
Then, PEB treatment was performed under conditions of 110 ° C. for 90 seconds, and further paddle development was performed for 30 seconds with a 2.38 mass% tetramethylammonium hydroxide (TMAH) aqueous solution at 23 ° C., followed by washing with water for 20 seconds and drying.

[Evaluation of shape and lithography characteristics]
-Example of a line and space pattern By such operation, the exposure amount Eop by which a line and space (L / S) pattern (pitch 240 nm) with a line width of 120 nm was formed was measured in units of mJ / cm ² (energy amount). where, in example 1 19mJ / cm ^2, example 2 20 mJ / cm ^2, Comparative example 1 was 19mJ / cm ^2.
Moreover, when the cross-sectional shape of the resist pattern at that time was observed with an SEM photograph, all the positive resist compositions had a very high rectangularity with high verticality of the pattern side wall and excellent surface smoothness. The L / S pattern was resolved.
In addition, the limit resolution of the L / S pattern when exposed at the exposure amount Eop was 110 nm.

  Further, at the exposure amount Eop, the depth of focus is shifted up and down, a resist pattern is formed in the same manner as described above, and a 120 nm L / S pattern is obtained within a range of ± 10% of the set dimension (132 nm to 108 nm). The depth of focus was determined. As a result, the depth of focus was the same for both the example and the comparative example.

  The exposure amount margin that can be formed within an error range of ± 10% for the 120 nm L / S pattern is 10.2% in Example 1, 9.8% in Example 2, and 9.1 in Comparative Example 1. %Met.

Example of isolated space pattern (trench pattern) In the same manner as described above, when the exposure amount Eop ′ for forming an isolated space pattern (pitch 1430 nm) having a space width of 130 nm was measured in units of mJ / cm ² (energy amount), Example 1 was 26 mJ / cm ² , Example 2 was 27 mJ / cm ² , and Comparative Example 1 was 29 mJ / cm ² .
Moreover, when the cross-sectional shape of the resist pattern at that time was observed with an SEM photograph, all the positive resist compositions had a very high rectangularity with high verticality of the pattern side wall and excellent surface smoothness. The isolated space pattern was resolved.
In addition, the limit resolution of the isolated space pattern when exposed at the exposure amount Eop ′ was 110 nm.

  In Eop ′, an isolated space pattern (pitch: 2200 nm) having a space width of 200 nm was formed in the same manner as described above, and the MEF value at 140 nm to 130 nm was determined in the same manner as described above. As a result, MEF (200 nm-130 nm) was 1.47 in Example 1, 1.48 in Example 2, and 1.48 in Comparative Example 1, and was almost equivalent.

  Further, the depth of focus of the isolated space pattern of 130 nm formed with the exposure amount Eop ′ was the same in both the example and the comparative example.

[Evaluation of etching resistance]
Further, a resist film was formed in the same manner as described above, and the etching resistance of the resist film was evaluated. That is, a mixed gas of tetrafluoromethane (CF ₄ ), trifluoromethane (CHF ₃ ) and helium (flow rate (ml / min) ratio 75: 45: 150) is used as an etching gas at a pressure of 300 mTorr and a temperature of 20 ° C. A resist composition is applied to the film, pre-baked, exposed without passing through a mask pattern, and subjected to PEB to form a resist film (hereinafter referred to as an unpatterned resist film) as an etching apparatus (manufactured by Tokyo Ohka Kogyo Co., Ltd., product) After performing dry etching by treating with RF (Ratio Frequency): frequency 400 kHz and output 1100 W for 90 seconds using the name “TCE-7612X”, the resist surface was subjected to AFM (atomic force microscope: di NanoScope IV manufactured by Veeco Instrument Inc.). / D500 ) Was observed in Example 1 and Example 2 had no surface roughness was achieved, a high smoothness. On the other hand, Comparative Example 1, the surface roughness was terrible.
The reason why the etching resistance and the surface roughness were evaluated using an unpatterned resist film is that the surface roughness was easier to measure than in the case of a patterned resist film.

As is clear from the above results, the resist patterns obtained using the positive resist compositions of Examples 1 and 2 had no surface roughness and high etching resistance. Moreover, the shape was also excellent with high rectangularity. In particular, the positive resist composition of Example 1 gave good results with good balance in all items. In addition, the lithography properties such as resolution, linearity, depth of focus, and exposure margin are almost the same as those in Comparative Example 1. In particular, the linearity in the isolated space pattern and the exposure margin in the line and space pattern are compared. It was superior to Example 1.
On the other hand, although the resist pattern obtained using the positive resist composition of Comparative Example 1 was excellent in shape and lithography characteristics, the etching resistance was very poor.

Claims (13)

A positive resist composition comprising a resin (A) having an acid dissociable, dissolution inhibiting group and increased in alkali solubility by the action of an acid, and a compound (B) that generates an acid upon irradiation with radiation,
Polymer (A2) in which the resin (A) is composed only of a main chain cyclic polymer (A1) and a structural unit (a ′) derived from (meth) acrylic acid ester and / or (meth) acrylic acid mixture der with is,
The main chain cyclic polymer (A1) is a structural unit (a1) represented by the following general formula (a-1), a structural unit (a2) represented by the following general formula (a-2), and the following general Having a structural unit (a3) represented by the formula (a-3);
The polymer (A2) is a structural unit (a′1) derived from a (meth) acrylic acid ester having an acid dissociable, dissolution inhibiting group, or a structural unit derived from a (meth) acrylic acid ester having a lactone ring. A positive resist composition comprising a structural unit (a′3) derived from (a′2) and a (meth) acrylic ester containing a polar group-containing aliphatic hydrocarbon group .

[In Formula (a-1), R ¹ is an alkyl group having 2 or more carbon atoms, s is 0 or 1, and t is an integer of 1 to 3. ]

[In Formula (a-2), R ² and R ³ each independently represent a hydrogen atom or a lower alkyl group, and s is 0 or 1. ]

[In formula (a-3), R ⁴ is an organic group having an alkali-soluble group, and s is 0 or 1. ]   The positive resist composition according to claim 1, wherein the polymers (A1) and (A2) have acid dissociable, dissolution inhibiting groups having the same structure.   The positive resist composition according to claim 1 or 2, wherein the polymers (A1) and (A2) have a lactone ring having the same structure. The positive resist composition according to any one of claims 1 to 3, wherein R ¹ in the formula (a-1) is an ethyl group and t is 2. R ⁴ in the general formula (a-3) is at least one hydroxyalkyl group having from 3 to 15 carbon atoms which hydrogen atoms are substituted by fluorine atoms or any one of claims 1 to 4 is a carboxyl group, The positive resist composition as described in 1. above. The positive resist composition according to claim 5, wherein R ⁴ in the general formula (a-3) is a group represented by the following general formula (a-4).

[In Formula (a-4), p is an integer of 1 to 5, and m and n are each independently an integer of 1 to 5. ] The structural unit (a'1) The positive resist composition according to any one of claims 1 to 6 is a structural unit represented by the following general formula (a-5).

[In Formula (a-5), R is a hydrogen atom or a methyl group, R ¹ is an alkyl group having 2 or more carbon atoms, and t is an integer of 1 to 3. ] The structural unit (a'2) The positive resist composition according to any one of claims 1-7 which is a structural unit represented by the following general formula (a-6).

[In formula (a-6), R represents a hydrogen atom or a methyl group, and R ² and R ³ each independently represent a hydrogen atom or a lower alkyl group. ] The positive resist according to any one of claims 1 to 8 , wherein a mass ratio of the main chain cyclic polymer (A1) to the polymer (A2) is in the range of 1: 9 to 9: 1. Composition. The resin (A) is a mixture of a polymer (A11) represented by the following general formula (a-11) and a polymer (A21) represented by the following general formula (a-21): the positive resist composition according to any one of 1-9.

[In the formula (a-21), R represents a hydrogen atom or a methyl group. ] The compounds generating an acid by irradiation of the radiation (B) The positive resist composition according to any one of claims 1 to 10 fluorinated alkyl sulfonic acid ion is an onium salt with anions. Further positive resist composition according to any one of claims 1 to 11, comprising a nitrogen-containing organic compound. A resist pattern forming method in which the positive resist composition according to any one of claims 1 to 12 is applied on a support, selectively exposed, and then developed to form a resist pattern.