JP2008033016A - Positive resist composition for multilayer resist and pattern forming method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive resist composition for multilayer resist used on an intermediate layer comprising a silicone-based hard mask material. <P>SOLUTION: The positive resist composition for multilayer resist used on an intermediate layer comprising a silicone-based hard mask material contains a component of which the alkali solubility increases by the action of an acid and an acid generator having a cationic moiety represented by formula (b1-4). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a positive resist composition for a multilayer resist used for forming an upper resist layer on an intermediate layer made of a silicone hard mask material, and a pattern forming method using the same.

In lithography technology, for example, a resist film made of a resist material is formed on a substrate, and the resist film is selectively exposed to radiation such as light or an electron beam through a mask on which a predetermined pattern is formed. And a development process is performed to form a resist pattern having a predetermined shape on the resist film. A resist material in which the exposed portion changes to a property that dissolves in the developer is referred to as a positive type, and a resist material that changes to a property in which the exposed portion does not dissolve in the developer is referred to as a negative type.
In recent years, in the manufacture of semiconductor elements and liquid crystal display elements, pattern miniaturization has been rapidly progressing due to advances in lithography technology.
As a technique for miniaturization, the wavelength of an exposure light source is generally shortened. Specifically, conventionally, ultraviolet rays typified by g-line and i-line have been used, but now mass production of semiconductor elements using a KrF excimer laser or an ArF excimer laser has started. In addition, studies have been made on F ₂ excimer lasers, electron beams, EUV (extreme ultraviolet rays), X-rays, and the like having shorter wavelengths than these excimer lasers.

  Resist materials are required to have lithography characteristics such as sensitivity to these exposure light sources and resolution capable of reproducing a pattern with fine dimensions. As a resist material satisfying such requirements, a chemically amplified resist containing a base resin whose alkali solubility is changed by the action of an acid and an acid generator that generates an acid upon exposure is used. For example, a positive chemically amplified resist contains, as a base resin, a resin whose alkali solubility is increased by the action of an acid and an acid generator. When a resist pattern is formed, an acid is generated from the acid generator by exposure. The exposed part becomes alkali-soluble.

Currently, as a resist base resin used in ArF excimer laser lithography and the like, a resin (acrylic resin) having a structural unit derived from (meth) acrylic acid ester in its main chain because of its excellent transparency near 193 nm ) And the like are generally used (see, for example, Patent Document 1).
The “(meth) acrylic acid ester” means one or both of an acrylic acid ester having a hydrogen atom bonded to the α-position and a methacrylic acid ester having a methyl group bonded to the α-position. “(Meth) acrylate” means one or both of an acrylate having a hydrogen atom bonded to the α-position and a methacrylate having a methyl group bonded to the α-position. “(Meth) acrylic acid” means one or both of acrylic acid having a hydrogen atom bonded to the α-position and methacrylic acid having a methyl group bonded to the α-position.

On the other hand, in recent years, miniaturization of resist patterns has further progressed, and a demand for high resolution has increased, and a resist pattern with a high aspect ratio has been demanded. As one of resist pattern forming methods corresponding to this, a three-layer resist method is known (for example, see Patent Document 2). In this method, first, a base material containing a film-forming resin is applied on a substrate, and this is heated to form an organic film, on which a resist film made of a silicone-based hard mask material is formed. After providing the (intermediate layer), an upper resist film is further provided thereon. Next, a resist pattern is formed on this upper resist film by a normal lithography technique, the pattern is transferred to the intermediate layer using the resist pattern as a mask, and then the organic film is etched using the patterned intermediate film as a mask. A pattern is formed on the top.
JP 2003-241385 A JP 2004-145262 A

  However, when a resist pattern is formed by providing an upper resist film on a resist film (intermediate layer) made of a silicone-based hard mask material using a conventional positive resist composition, the intermediate layer and the upper resist film There is a problem in that the resist pattern shape tends to be poor, such as a resist pattern spreading (footing) between the two and the cross-sectional shape of the resist pattern becomes a trailing shape and the rectangularity is lowered.

  The present invention has been made in view of the above circumstances, and a positive resist composition for a multi-layer resist that is suitably used when an upper resist layer is formed on an intermediate layer made of a silicone-based hard mask material. An object of the present invention is to provide a pattern forming method using the.

The present inventors propose the following means in order to solve the above problems.
That is, in the first aspect of the present invention, in the step of forming a lower organic film capable of dry etching on a substrate and the step of forming an intermediate layer made of a silicone-based hard mask material on the lower organic film, Used on the middle layer,
A positive resist composition for a multilayer resist comprising a base material component (A) whose alkali solubility is increased by the action of an acid and an acid generator component (B) which generates an acid upon exposure,
The acid generator component (B) is a positive resist composition for multilayer resists containing an acid generator (B1) having a cation moiety represented by the following general formula (b1-4).

  The second aspect of the present invention includes a step of forming a lower organic film capable of dry etching on a substrate, a step of forming an intermediate layer made of a silicone-based hard mask material on the lower organic film, On the intermediate layer, a step of forming an upper resist film using the positive resist composition for multilayer resist of the first aspect of the present invention to form a resist laminate, and exposing and developing the upper resist film And a step of forming a resist pattern.

In the present specification and claims, “structural unit” means a monomer unit (monomer unit) constituting a resin component (polymer).
“Exposure” is a concept that includes radiation exposure in general.
Unless otherwise specified, the “alkyl group” includes linear, branched and cyclic monovalent saturated hydrocarbon groups.
The “lower alkyl group” means an alkyl group having 1 to 5 carbon atoms.

  According to the present invention, there are provided a positive resist composition for a multilayer resist suitably used for forming an upper resist layer on an intermediate layer made of a silicone-based hard mask material, and a pattern forming method using the same.

≪Positive resist composition for multilayer resist≫
The positive resist composition for a multilayer resist according to the first aspect of the present invention comprises a step of forming a lower organic film capable of dry etching on a substrate, and an intermediate layer comprising a silicone-based hard mask material on the lower organic film The base material component (A) which is used on the intermediate layer and increases the alkali solubility by the action of an acid, and the acid generator component (B) which generates an acid upon exposure are contained.
The positive resist composition for multilayer resist of the present invention comprises a step of forming a lower organic film capable of dry etching on a substrate, and a step of forming an intermediate layer made of a silicone-based hard mask material on the lower organic film. , A pattern forming method (hereinafter referred to as “a resist layered body by forming an upper resist film on the intermediate layer” and a step of exposing and developing the upper resist film to form a resist pattern. In the “pattern formation method including a step of forming a resist laminate”), it can be suitably used as the positive resist composition for forming the upper resist film.

<(A) component>
In the positive resist composition for multilayer resist according to the first aspect of the present invention, the base component (A) (hereinafter referred to as the component (A)) whose alkali solubility is increased by the action of an acid is the action of an acid. Thus, it is possible to use a polymer material whose alkali solubility increases, and a low molecular material whose alkali solubility is increased by the action of an acid.

  In the positive resist composition for a multilayer resist of the present invention, the component (A) is preferably a resin component (A1) (hereinafter referred to as the component (A1)) whose alkali solubility is increased by the action of an acid. The component (A1) is an alkali-insoluble resin having a so-called acid dissociable dissolution inhibiting group. When an acid is generated from the component (B) by exposure during resist pattern formation, the acid dissociates the acid dissociable dissolution inhibiting group. By making it, (A) component becomes alkali-soluble. Therefore, in the formation of the resist pattern, when the resist film obtained by applying the positive resist composition on the substrate is selectively exposed, the exposed portion turns to alkali-soluble while the unexposed portion is alkali-insoluble. Since it remains unchanged, alkali development can be performed.

  Next, the component (A1) that is preferably used in the positive resist composition for multilayer resists of the present invention will be described with examples.

<(A1) component>
The component (A1) suitably used in such a positive resist composition preferably has a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group.
The component (A1) preferably further has a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group.
The component (A1) preferably further has a structural unit (a3) derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group.

Here, in the present specification and claims, the “structural unit derived from an acrylate ester” means a structural unit formed by cleavage of an ethylenic double bond of an acrylate ester.
“Acrylic acid esters” include those in which a hydrogen atom is bonded to the carbon atom at the α-position, and those in which a substituent (atom or group other than a hydrogen atom) is bonded to the carbon atom in the α-position. Include concepts.
Examples of the substituent include a halogen atom, a lower alkyl group, and a halogenated lower alkyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable.
Note that the α position (α-position carbon atom) of a structural unit derived from an acrylate ester means a carbon atom to which a carbonyl group is bonded unless otherwise specified.
In the acrylate ester, as the lower alkyl group as a substituent at the α-position, specifically, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, Examples include linear or branched lower alkyl groups such as isopentyl group and neopentyl group.
In the present invention, the α-position of the acrylate ester is preferably a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group, and a hydrogen atom, a fluorine atom, a lower alkyl group or a fluorine atom. A lower alkyl group is more preferred, and a hydrogen atom or a methyl group is particularly preferred from the viewpoint of industrial availability.

・ Structural unit (a1)
The structural unit (a1) is a structural unit derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group.
The acid dissociable, dissolution inhibiting group in the structural unit (a1) has an alkali dissolution inhibiting property that makes the entire component (A1) insoluble in alkali before dissociation, and changes the entire component (A1) to alkali-soluble after dissociation. If it is a thing, the thing proposed until now as an acid dissociable, dissolution inhibiting group of the base resin for chemically amplified resists can be used.
Generally, a group that forms a cyclic or chain tertiary alkyl ester with a carboxy group in (meth) acrylic acid or the like; an acetal-type acid dissociable, dissolution inhibiting group such as an alkoxyalkyl group is widely known. .

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

Here, “aliphatic” in the claims and the specification is a relative concept with respect to aromatics, and is defined to mean a group, a compound, or the like that does not have aromaticity.
“Aliphatic branched” means having a branched structure having no aromaticity.
The structure of the “aliphatic branched acid dissociable, dissolution inhibiting group” is not limited to a group consisting of a carbon atom and a hydrogen atom (hydrocarbon group), but is preferably a hydrocarbon group.
The “hydrocarbon group” may be either saturated or unsaturated, but is usually preferably saturated.
As the aliphatic branched acid dissociable, dissolution inhibiting group, a tertiary alkyl group having 4 to 8 carbon atoms is preferable, and specific examples include a tert-butyl group, a tert-amyl group, and a tert-heptyl group. .

The “aliphatic cyclic group” means a monocyclic group or a polycyclic group having no aromaticity.
The “aliphatic cyclic group” in the structural unit (a1) may or may not have a substituent. Examples of the substituent include a lower alkyl group having 1 to 5 carbon atoms, a fluorine atom, a fluorinated lower alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, an oxygen atom (= O), and the like.
The basic ring structure excluding the substituent of the “aliphatic cyclic group” is not limited to a group consisting of carbon and hydrogen (hydrocarbon group), but is preferably a hydrocarbon group. The “hydrocarbon group” may be either saturated or unsaturated, but is usually preferably saturated. The “aliphatic cyclic group” is preferably a polycyclic group.
Specific examples of the aliphatic cyclic group include, for example, a monocycloalkane, a bicycloalkane, a tricycloalkane, which may or may not be substituted with a lower alkyl group, a fluorine atom or a fluorinated alkyl group, Examples thereof include a group obtained by removing one or more hydrogen atoms from a polycycloalkane such as tetracycloalkane. Specific examples include monocycloalkanes such as cyclopentane and cyclohexane, and groups obtained by removing one or more hydrogen atoms from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane.
Examples of the acid dissociable, dissolution inhibiting group containing an aliphatic cyclic group include a group having a tertiary carbon atom on the ring skeleton of a cyclic alkyl group. Specifically, 2-methyl-2 -Adamantyl group, 2-ethyl-2-adamantyl group, etc. are mentioned. Alternatively, in a structural unit represented by the following general formula (a1 ″), an aliphatic cyclic group such as an adamantyl group, such as a group bonded to an oxygen atom of a carbonyloxy group (—C (O) —O—); And a group having a branched alkylene group having a tertiary carbon atom bonded thereto.

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

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

The “acetal-type acid dissociable, dissolution inhibiting group” is generally bonded to an oxygen atom by substituting a hydrogen atom at the terminal of an alkali-soluble group such as a carboxy group or a hydroxyl group. When an acid is generated by exposure, the acid acts to break the bond between the acetal acid dissociable, dissolution inhibiting group and the oxygen atom to which the acetal acid dissociable, dissolution inhibiting group is bonded.
Examples of the acetal type acid dissociable, dissolution inhibiting group include a group represented by the following general formula (p1).

［式中、Ｒ^１’，Ｒ^２’はそれぞれ独立して水素原子または低級アルキル基を表し、ｎは０〜３の整数を表し、Ｙは低級アルキル基または脂肪族環式基を表す。］

[Wherein, R ¹ ′ and R ² ′ each independently represents a hydrogen atom or a lower alkyl group, n represents an integer of 0 to 3, and Y represents a lower alkyl group or an aliphatic cyclic group. ]

In the above formula, n is preferably an integer of 0 to 2, more preferably 0 or 1, and most preferably 0.
Examples of the lower alkyl group for R ¹ ′ and R ² ′ include the same lower alkyl groups as those described above for R. A methyl group or an ethyl group is preferable, and a methyl group is most preferable.
In the present invention, it is preferable that at least one of R ¹ ′ and R ² ′ is a hydrogen atom. That is, the acid dissociable, dissolution inhibiting group (p1) is preferably a group represented by the following general formula (p1-1).

［式中、Ｒ^１’、ｎ、Ｙは上記と同様である。］

[Wherein R ¹ ′, n and Y are the same as described above. ]

Examples of the lower alkyl group for Y include the same lower alkyl groups as those described above for R.
The aliphatic cyclic group for Y can be appropriately selected from monocyclic or polycyclic aliphatic cyclic groups conventionally proposed in a number of ArF resists and the like. For example, the above “aliphatic ring” Examples thereof are the same as those in the formula group.

  Examples of the acetal type acid dissociable, dissolution inhibiting group also include a group represented by the following general formula (p2).

［式中、Ｒ^１７、Ｒ^１８はそれぞれ独立して直鎖状または分岐鎖状のアルキル基または水素原子であり、Ｒ^１９は直鎖状、分岐鎖状または環状のアルキル基である。または、Ｒ^１７およびＲ^１９がそれぞれ独立に直鎖状または分岐鎖状のアルキレン基であって、Ｒ^１７の末端とＲ^１９の末端とが結合して環を形成していてもよい。］

[Wherein, R ¹⁷ and R ¹⁸ each independently represent a linear or branched alkyl group or a hydrogen atom, and R ¹⁹ represents a linear, branched or cyclic alkyl group. Alternatively, R ¹⁷ and R ¹⁹ may be each independently a linear or branched alkylene group, and the end of R ^{17 and} the end of R ¹⁹ may be bonded to form a ring. ]

In R ¹⁷ and R ¹⁸ , the alkyl group preferably has 1 to 15 carbon atoms, may be linear or branched, and is preferably an ethyl group or a methyl group, and most preferably a methyl group. In particular, it is preferable that one of R ¹⁷ and R ¹⁸ is a hydrogen atom and the other is a methyl group.
R ¹⁹ is a linear, branched or cyclic alkyl group, preferably having 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.
When R ¹⁹ is linear or branched, it preferably has 1 to 5 carbon atoms, more preferably an ethyl group or a methyl group, and most preferably an ethyl group.
When R ¹⁹ is cyclic, it preferably has 4 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10 carbon atoms. Specifically, one or more polycycloalkanes such as monocycloalkane, bicycloalkane, tricycloalkane, and tetracycloalkane, which may or may not be substituted with a fluorine atom or a fluorinated alkyl group, are included. Examples include groups excluding hydrogen atoms. Specific examples include monocycloalkanes such as cyclopentane and cyclohexane, and groups obtained by removing one or more hydrogen atoms from polycycloalkanes such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Among them, a group obtained by removing one or more hydrogen atoms from adamantane is preferable.
In the above formula, R ¹⁷ and R ¹⁹ are each independently a linear or branched alkylene group (preferably an alkylene group having 1 to 5 carbon atoms), and the end of R ^{19 and} the end of R ¹⁷ And may be combined.
In this case, a cyclic group is formed by R ¹⁷ , R ¹⁹ , the oxygen atom to which R ¹⁹ is bonded, and the carbon atom to which the oxygen atom and R ¹⁷ are bonded. The cyclic group is preferably a 4-7 membered ring, and more preferably a 4-6 membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

  As the structural unit (a1), one or more selected from the group consisting of structural units represented by the following general formula (a1-0-1) and structural units represented by the following general formula (a1-0-2): Is preferably used.

［式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基を示し；Ｘ^１は酸解離性溶解抑制基を示す。］

[Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group; and X ¹ represents an acid dissociable, dissolution inhibiting group. ]

［式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基を示し；Ｘ^２は酸解離性溶解抑制基を示し；Ｙ^２はアルキレン基または脂肪族環式基を示す。］

[Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group; X ² represents an acid dissociable, dissolution inhibiting group; Y ² represents an alkylene group or an aliphatic cyclic group. ]

In the general formula (a1-0-1), the halogen atom, lower alkyl group or halogenated lower alkyl group of R is a halogen atom, lower alkyl group or halogenated lower group which may be bonded to the α-position of the acrylate ester. It is the same as the alkyl group.
X ¹ is not particularly limited as long as it is an acid dissociable, dissolution inhibiting group, and examples thereof include the above-described tertiary alkyl ester type acid dissociable, dissolution inhibiting group, and acetal type acid dissociable, dissolution inhibiting group. A tertiary alkyl ester type acid dissociable, dissolution inhibiting group is preferred.

In general formula (a1-0-2), R is the same as defined above.
X ² is the same as X ¹ in formula (a1-0-1).
Y ² is preferably an alkylene group having 1 to 4 carbon atoms or a divalent aliphatic cyclic group, and the aliphatic cyclic group is the above except that a group in which two or more hydrogen atoms are removed is used. The thing similar to description of an "aliphatic cyclic group" can be used.

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

［上記式中、Ｘ’は第３級アルキルエステル型酸解離性溶解抑制基を表し、Ｙは炭素数１〜５の低級アルキル基、または脂肪族環式基を表し；ｎは０〜３の整数を表し；ｍは０または１を表し；Ｒは前記と同じであり、Ｒ^１’、Ｒ^２’はそれぞれ独立して水素原子または炭素数１〜５の低級アルキル基を表す。］

[In the above formula, X ′ represents a tertiary alkyl ester type acid dissociable, dissolution inhibiting group, Y represents a lower alkyl group having 1 to 5 carbon atoms, or an aliphatic cyclic group; M represents 0 or 1; R is the same as defined above; R ¹ ′ and R ² ′ each independently represent a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms. ]

At least one of R ¹ ′ and R ² ′ is preferably a hydrogen atom, more preferably a hydrogen atom. n is preferably 0 or 1.

X ′ is the same as the tertiary alkyl ester type acid dissociable, dissolution inhibiting group exemplified in X ¹ above.
Examples of the aliphatic cyclic group for Y include the same groups as those exemplified above in the description of “aliphatic cyclic group”.

  Specific examples of the structural units represented by the general formulas (a1-1) to (a1-4) are shown below.

As the structural unit (a1), one type may be used alone, or two or more types may be used in combination.
Among these, the structural unit represented by the general formula (a1-1) is preferable, and specifically, (a1-1-1) to (a1-1-6) or (a1-1-35) to (a1- It is more preferable to use at least one selected from structural units represented by 1-41).
Furthermore, as the structural unit (a1), in particular, those represented by the following general formula (a1-1-01) including the structural units of the formulas (a1-1-1) to (a1-1-4) The following general formula (a1-1-02) including the structural units of formulas (a1-1-35) to (a1-1-41) is also preferable.

［式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基を示し、Ｒ^１１は低級アルキル基を示す。］

[Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group, and R ¹¹ represents a lower alkyl group. ]

［式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基を示し、Ｒ^１２は低級アルキル基を示す。ｈは１〜３の整数を表す。］

[Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group, and R ¹² represents a lower alkyl group. h represents an integer of 1 to 3. ]

In general formula (a1-1-01), R is the same as defined above. The lower alkyl group for R ^{11 is the same as} the lower alkyl group for R, and is preferably a methyl group or an ethyl group.

In general formula (a1-1-02), R is the same as defined above. The lower alkyl group for R ^{12 is the same as} the lower alkyl group for R, preferably a methyl group or an ethyl group, and most preferably an ethyl group. h is preferably 1 or 2, and most preferably 2.

  The proportion of the structural unit (a1) in the component (A1) is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, more preferably 25 to 50 mol%, based on all structural units constituting the component (A1). Is more preferable. By setting it to the lower limit value or more, a pattern can be easily obtained when the positive resist composition is obtained, and by setting the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a2)
In the present invention, the component (A1) preferably has a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group in addition to the structural unit (a1).
Here, the lactone-containing cyclic group refers to a cyclic group containing one ring (lactone ring) containing an —O—C (O) — structure. The lactone ring is counted as the first ring. When only the lactone ring is present, it is called a monocyclic group. When it has another ring structure, it is called a polycyclic group regardless of the structure.
When the component (A1) is used for forming a resist film, the lactone cyclic group of the structural unit (a2) increases the adhesion of the resist film to the substrate or has an affinity for a developer containing water. It is effective in raising.

As the structural unit (a2), any unit can be used without any particular limitation.
Specifically, examples of the lactone-containing monocyclic group include groups in which one hydrogen atom has been removed from γ-butyrolactone. Examples of the lactone-containing polycyclic group include groups in which one hydrogen atom has been removed from a bicycloalkane, tricycloalkane, or tetracycloalkane having a lactone ring.

  More specifically, examples of the structural unit (a2) include structural units represented by general formulas (a2-1) to (a2-5) shown below.

［式中、Ｒは水素原子、ハロゲン原子、低級アルキル基またはハロゲン化低級アルキル基であり、Ｒ’は水素原子、低級アルキル基、または炭素数１〜５のアルコキシ基であり、ｍは０または１の整数であり、Ａは炭素数１〜５のアルキレン基または酸素原子である。］

[Wherein, R is a hydrogen atom, a halogen atom, a lower alkyl group or a halogenated lower alkyl group, R ′ is a hydrogen atom, a lower alkyl group, or an alkoxy group having 1 to 5 carbon atoms, and m is 0 or 1 is an integer, and A is an alkylene group having 1 to 5 carbon atoms or an oxygen atom. ]

R in the general formulas (a2-1) to (a2-5) is the same as R in the structural unit (a1).
The lower alkyl group for R ′ is the same as the lower alkyl group for R in the structural unit (a1).
Specific examples of the alkylene group having 1 to 5 carbon atoms of A include a methylene group, an ethylene group, an n-propylene group, and an isopropylene group.
In general formulas (a2-1) to (a2-5), R ′ is preferably a hydrogen atom in view of industrial availability.
Below, the specific structural unit of the said general formula (a2-1)-(a2-5) is illustrated.

  Among these, it is preferable to use at least one selected from general formulas (a2-1) to (a2-5), and at least one selected from general formulas (a2-1) to (a2-3). It is preferable to use more than one species. Specifically, chemical formulas (a2-1-1), (a2-1-2), (a2-2-1), (a2-2-2), (a2-3-1), (a2-3) -2), at least one selected from (a2-3-9) and (a2-3-10) is preferably used.

In the component (A1), as the structural unit (a2), one type of structural unit may be used, or two or more types may be used in combination.
The proportion of the structural unit (a2) in the component (A1) is preferably 5 to 60 mol%, more preferably 10 to 50 mol%, with respect to the total of all the structural units constituting the component (A1). More preferred is mol%. By making it the lower limit value or more, the effect of containing the structural unit (a2) can be sufficiently obtained, and by making it the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a3)
In the present invention, the component (A1) is an acrylic ester containing a polar group-containing aliphatic hydrocarbon group in addition to the structural unit (a1) or in addition to the structural units (a1) and (a2). It is preferable to have a derived structural unit (a3). By having the structural unit (a3), the hydrophilicity of the component (A1) is increased, the affinity with the developer is increased, the alkali solubility in the exposed area is improved, and the resolution is improved.
Examples of the polar group include a hydroxyl group, a cyano group, a carboxy group, and a hydroxyalkyl group in which a part of hydrogen atoms of an alkyl group is substituted with a fluorine atom. A hydroxyl group is particularly preferable.
Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group having 1 to 10 carbon atoms (preferably an alkylene group) and a polycyclic aliphatic hydrocarbon group (polycyclic group). . As the polycyclic group, for example, a resin for a resist composition for ArF excimer laser can be appropriately selected from among many proposed ones.
Among them, a structural unit derived from an acrylate ester containing an aliphatic polycyclic group containing a hydroxyalkyl group in which a part of hydrogen atoms of a hydroxyl group, a cyano group, a carboxy group, or an alkyl group is substituted with a fluorine atom Is more preferable. Examples of the polycyclic group include groups in which one or more hydrogen atoms have been removed from bicycloalkane, tricycloalkane, tetracycloalkane, or the like. Specific examples include groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, or tetracyclododecane. Among these polycyclic groups, there are groups in which two or more hydrogen atoms have been removed from adamantane, groups in which two or more hydrogen atoms have been removed from norbornane, and groups in which two or more hydrogen atoms have been removed from tetracyclododecane. Industrially preferable.

  The structural unit (a3) is derived from a hydroxyethyl ester of acrylic acid 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. When the hydrocarbon group is a polycyclic group, a structural unit represented by the following formula (a3-1), a structural unit represented by (a3-2), (a3-3) The structural unit represented by is mentioned as a preferable thing.

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

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

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

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

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

In the component (A1), as the structural unit (a3), one type of structural unit may be used alone, or two or more types may be used in combination.
The proportion of the structural unit (a3) in the component (A1) is preferably 5 to 50 mol%, more preferably 5 to 40 mol%, based on all the structural units constituting the component (A1). 25 mol% is more preferable. By setting it to the lower limit value or more, the effect of containing the structural unit (a3) is sufficiently obtained, and by setting the upper limit value or less, it is possible to balance with other structural units.

・ Structural unit (a4)
The component (A1) may contain other structural units (a4) other than the structural units (a1) to (a3) as long as the effects of the present invention are not impaired.
The structural unit (a4) is not particularly limited as long as it is another structural unit that is not classified into the structural units (a1) to (a3) described above. For ArF excimer laser, for KrF excimer laser (preferably ArF excimer laser) A number of conventionally known resins can be used for resist resins such as
As the structural unit (a4), for example, a structural unit derived from an acrylate ester containing a non-acid-dissociable aliphatic polycyclic group is preferable. Examples of the polycyclic group include those exemplified in the case of the structural unit (a1), and for ArF excimer laser and KrF excimer laser (preferably for ArF excimer laser). A number of hitherto known materials can be used for the resin component of the resist composition.
In particular, at least one selected from a tricyclodecanyl group, an adamantyl group, a tetracyclododecanyl group, an isobornyl group, and a norbornyl group is preferable in terms of industrial availability. These polycyclic groups may have a linear or branched alkyl group having 1 to 5 carbon atoms as a substituent.
Specific examples of the structural unit (a4) include those represented by the following general formulas (a4-1) to (a4-5).

［式中、Ｒは前記と同じである。］

[Wherein, R is the same as defined above. ]

  When the structural unit (a4) is contained in the component (A1), the proportion of the structural unit (a4) is preferably 1 to 30 mol% with respect to the total of all the structural units constituting the component (A1). 10 to 20 mol% is more preferable.

  In the present invention, the component (A1) is a resin component (polymer) whose alkali solubility is increased by the action of an acid. Examples of suitable resin component (polymer) include the structural unit (a1), Examples of the copolymer having (a2) and (a3) include, for example, a copolymer composed of structural units (a1), (a2) and (a3), structural units (a1), ( Examples thereof include a copolymer comprising a2), (a3) and (a4).

  In the present invention, the component (A) is particularly preferably a copolymer (A1-1) containing a combination of structural units represented by the following general formula (A1-1).

［式中、Ｒは前記と同様である。Ｒ^２０は低級アルキル基である。］

[Wherein, R is the same as defined above. R ²⁰ is a lower alkyl group. ]

In formula (A1-1), R is the same as defined above, and most preferably a hydrogen atom or a methyl group.
R ²⁰ is a lower alkyl group, preferably a methyl group or an ethyl group, and most preferably a methyl group.

In the component (A), as the copolymer (A1-1), one type may be used alone, or two or more types may be used in combination.
The content of the copolymer (A1-1) in the component (A) is preferably 70% by mass or more, more preferably 80% by mass or more, and may be 100% by mass. Especially, it is most preferable that it is 100 mass%. By being above the lower limit of the range, the lithography properties are further improved when a positive resist composition is obtained.

The component (A1) can be obtained by polymerizing a monomer for deriving each structural unit by a known radical polymerization using a radical polymerization initiator such as azobisisobutyronitrile (AIBN).
Further, for the component (A1), in the polymerization, a chain transfer agent such as HS—CH ₂ —CH ₂ —CH ₂ —C (CF ₃ ) ₂ —OH is used in combination, so that the terminal A —C (CF ₃ ) ₂ —OH group may be introduced into the. As described above, a copolymer introduced with a hydroxyalkyl group in which a part of hydrogen atoms of the alkyl group is substituted with a fluorine atom reduces development defects and LER (line edge roughness: uneven unevenness of line side walls). It is effective in reducing

The mass average molecular weight (Mw) of the component (A1) (polystyrene conversion standard by gel permeation chromatography) is not particularly limited, but is preferably 2000 to 50000, more preferably 3000 to 30000, and most preferably 5000 to 20000. preferable. When it is smaller than the upper limit of this range, it has sufficient solubility in a resist solvent to be used as a resist, and when it is larger than the lower limit of this range, dry etching resistance and resist pattern cross-sectional shape are good.
Further, the dispersity (Mw / Mn) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5. In addition, Mn shows a number average molecular weight.
Further, as the component (A1), alkali-soluble resin components other than the copolymer (A1-1), for example, other polymer compounds used in conventional positive resist compositions can be used.
In the positive resist composition of the present invention, the content of the component (A1) may be adjusted according to the resist film thickness to be formed.

<(B) component>
In the positive resist composition for multilayer resists of the present invention, the acid generator component (B) that generates an acid upon exposure is an acid generator (B1) having a cation moiety represented by the general formula (b1-4). (Hereinafter referred to as the component (B1)).
When the component (B) contains the component (B1), an excellent suppression effect is obtained for footing that is likely to occur when an upper resist layer is formed on an intermediate layer made of a silicone hard mask material. In a pattern forming method including a step of forming a resist laminate, good lithography characteristics can be obtained when a resist composition is used for forming an upper resist film. Further, by using the component (B1) in combination with the structural unit (a1), line width roughness (LWR) can be reduced.
The component (B1) has good solubility in general resist solvents such as PGME, PGMEA, and EL. Moreover, it can mix | blend much in the resist composition used for the pattern formation method including the process of forming a resist laminated body. This is considered to be due to high transparency (inhibition of light absorption) with respect to the exposure wavelength band (particularly the wavelength band of ArF excimer laser).

  For example, a compound represented by the following general formula (b1-40) can be used as the acid generator (B1).

前記一般式（ｂ１−４０）中、Ｘ⁻はアニオンである。Ｘ⁻のアニオン部は特に制限されず、オニウム塩系酸発生剤のアニオン部として知られているものを適宜用いることができる。例えば、一般式「Ｒ^１４ＳＯ_３ ⁻（Ｒ^１４は、直鎖、分岐若しくは環状のアルキル基又はハロゲン化アルキル基を表す。）」で表されるアニオンを用いることができる。

In the general formula (b1-40), X ⁻ represents an anion. The anion moiety of X ⁻ is not particularly limited, and any known anion moiety of the onium salt acid generator can be used as appropriate. For example, an anion represented by the general formula “R ¹⁴ SO ₃ ^— (R ¹⁴ represents a linear, branched or cyclic alkyl group or halogenated alkyl group)” can be used.

In the general formula “R ¹⁴ SO ₃ ⁻ ”, R ¹⁴ represents a linear, branched or cyclic alkyl group or a halogenated alkyl group.
The linear or branched alkyl group as R ¹⁴ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.
The cyclic alkyl group as R ¹⁴ preferably has 4 to 15 carbon atoms, more preferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbon atoms.
R ¹⁴ is preferably a halogenated alkyl group. That is, in the general formula (b1-40), X ⁻ is preferably a halogenated alkyl sulfonate ion. An alkyl halide is one in which part or all of the hydrogen atoms in the alkyl are substituted with halogen atoms. Here, examples of the halogenated alkyl include those in which a halogen atom is substituted for the same as the “alkyl group” in R ⁴¹ , R ⁴² and R ⁴³ . Examples of the halogen atom to be substituted include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. In the halogenated alkyl, it is desirable that 50 to 100% of the total number of hydrogen atoms is substituted with halogen atoms, and it is more preferable that all are substituted.
Here, the halogenated alkyl group is preferably a fluorinated alkyl group. The fluorinated alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms. The fluorination rate of the fluorinated alkyl group (ratio of the number of fluorine atoms substituted by fluorination to the total number of hydrogen atoms in the alkyl group before fluorination, the same shall apply hereinafter) is preferably 10 to 100%. More preferably, it is 50 to 100%, and in particular, those in which all hydrogen atoms are substituted with fluorine atoms are preferred because the strength of the acid becomes strong.

In the general formula (b1-40), X ⁻ may be an anion represented by the following general formula (b-3), an anion represented by the following general formula (b-4), or the like.

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

In the general formula (b-3), X ″ is a linear or branched alkylene group in which at least one hydrogen atom is substituted with a fluorine atom, and the alkylene group preferably has 2 to 2 carbon atoms. 6, more preferably 3 to 5 carbon atoms, most preferably 3 carbon atoms.
In the general formula (b-4), Y ″ and Z ″ each independently represent a linear or branched alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and the carbon of the alkyl group The number is preferably 1 to 10, more preferably 1 to 7 carbon atoms, and most preferably 1 to 3 carbon atoms.
The number of carbon atoms of the X ″ alkylene group or the number of carbon atoms of the Y ″ and Z ″ alkyl groups is preferably as small as possible because the solubility in a resist solvent is good within the above-mentioned range of carbon numbers.
In addition, in the alkylene group of X ″ or the alkyl group of Y ″ and Z ″, the strength of the acid increases as the number of hydrogen atoms substituted with fluorine atoms increases, and high-energy light or electron beam of 200 nm or less The fluorination rate of the alkylene group or alkyl group is preferably 70 to 100%, more preferably 90 to 100%, and most preferably all hydrogen atoms are fluorine atoms. A substituted perfluoroalkylene group or a perfluoroalkyl group.

  Preferred specific examples of the compound represented by the general formula (b1-40) are shown below.

  Among these, the compound represented by the chemical formula (b1-41) is preferable.

  The compound represented by the general formula (b1-40) includes, for example, a compound represented by the following general formula (b1-0-41) and a compound represented by the following general formula (b1-0-42). And a catalyst such as copper (II) benzoate in a solvent such as chlorobenzene and iodobenzene at 80 to 130 ° C., more preferably at 100 to 120 ° C., for 0.5 to 3 hours, more preferably 1 It can be obtained by reacting for ˜2 hours.

［式中、Ｘ⁻は、上記（ｂ１−４０）式中のＸ⁻と同様である。］

Wherein, X ^- is, X in the above (b1-40) expression ^- is the same as. ]

(B) A component can be used 1 type or in mixture of 2 or more types.
In the positive resist composition for a multilayer resist of the present invention, the content of the component (B1) in the entire component (B) is preferably 40% by mass or more, more preferably 70% by mass or more, and 100 It may be mass%. Most preferably, it is 100 mass%. By being at least the lower limit of the range, the resist pattern shape is good. In particular, when a resist pattern is formed using a resist composition for forming an upper resist film when forming a multilayer resist laminate, the lithography properties are improved. When forming a multilayer resist laminate, it is preferable because matching with the lower layer film of the resist is good, and resist pattern tailing and the like can be suppressed.
Moreover, in the positive resist composition for multilayer resists of this invention, it is preferable that content of (B1) component is 1-30 mass parts with respect to 100 mass parts of said (A) component, 5-20 It is particularly preferably part by mass, and most preferably 7 to 18 parts by mass. By being at least the lower limit of the range, the lithography properties are improved particularly when a resist pattern is formed using the resist composition for forming an upper resist film. On the other hand, when it is not more than the upper limit value, the storage stability is good.

In the component (B), an acid generator (B2) other than the component (B1) (hereinafter referred to as the component (B2)) may be used in combination with the component (B1).
The component (B2) is not particularly limited as long as it is other than the component (B1), and those that have been proposed as acid generators for chemically amplified resists can be used.
Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, and poly (bissulfonyl) diazomethanes. There are various known diazomethane acid generators, nitrobenzyl sulfonate acid generators, imino sulfonate acid generators, disulfone acid generators, and the like.

  As the onium salt acid generator, for example, an acid generator represented by the following general formula (b-0) can be preferably used.

[Wherein R ⁵¹ represents a linear, branched or cyclic alkyl group, or a linear, branched or cyclic fluorinated alkyl group; R ⁵² represents a hydrogen atom, a hydroxyl group, a halogen atom, linear or A branched alkyl group, a linear or branched halogenated alkyl group, or a linear or branched alkoxy group; R ⁵³ is an optionally substituted aryl group; u "Is an integer from 1 to 3.]

In General Formula (b-0), R ⁵¹ represents a linear, branched, or cyclic alkyl group, or a linear, branched, or cyclic fluorinated alkyl group.
The linear or branched alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.
The cyclic alkyl group preferably has 4 to 12 carbon atoms, more preferably 5 to 10 carbon atoms, and most preferably 6 to 10 carbon atoms.
The fluorinated alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms. The fluorination rate of the fluorinated alkyl group (ratio of the number of substituted fluorine atoms to the total number of hydrogen atoms in the alkyl group) is preferably 10 to 100%, more preferably 50 to 100%. Those in which all hydrogen atoms are substituted with fluorine atoms are preferred because the strength of the acid is increased.
R ⁵¹ is most preferably a linear alkyl group or a fluorinated alkyl group.

R ⁵² represents a hydrogen atom, a hydroxyl group, a halogen atom, a linear or branched alkyl group, a linear or branched alkyl halide group, or a linear or branched alkoxy group.
In R ⁵² , examples of the halogen atom include a fluorine atom, a bromine atom, a chlorine atom, and an iodine atom, and a fluorine atom is preferable.
In R ⁵² , the alkyl group is linear or branched, and the carbon number thereof is preferably 1 to 5, particularly 1 to 4, and more preferably 1 to 3.
In R ⁵² , the halogenated alkyl group is a group in which part or all of the hydrogen atoms in the alkyl group are substituted with halogen atoms. Examples of the alkyl group herein are the same as the “alkyl group” in R ⁵² . Examples of the halogen atom to be substituted include the same as those described above for the “halogen atom”. In the halogenated alkyl group, it is desirable that 50 to 100% of the total number of hydrogen atoms are substituted with halogen atoms, and it is more preferable that all are substituted.
In R ⁵² , the alkoxy group is linear or branched, and the carbon number thereof is preferably 1 to 5, particularly 1 to 4, and more preferably 1 to 3.
Among these, R ⁵² is preferably a hydrogen atom.

R ⁵³ is an aryl group which may have a substituent, and examples of the structure of the basic ring (matrix ring) excluding the substituent include a naphthyl group, a phenyl group, an anthracenyl group, and the like. From the viewpoint of absorption of exposure light such as ArF excimer laser, a phenyl group is desirable.
Examples of the substituent include a hydroxyl group and a lower alkyl group (straight or branched chain, preferably having 5 or less carbon atoms, particularly preferably a methyl group).
As the aryl group for R ^53, an aryl group having no substituent is more preferable.
u ″ is an integer of 1 to 3, preferably 2 or 3, and particularly preferably 3.

  Preferable examples of the acid generator represented by the general formula (b-0) include the following.

  The acid generator represented by general formula (b-0) can be used alone or in combination of two or more.

  As other onium salt-based acid generators represented by the general formula (b-0), for example, compounds represented by the following general formula (b-1) or (b-2) are also preferably used. It is done.

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

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

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

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

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

  Specific examples of the onium salt acid generators represented by the formulas (b-1) and (b-2) include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate, bis (4-tert-butylphenyl) iodonium. Trifluoromethanesulfonate or nonafluorobutanesulfonate, triphenylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate, tri (4-methylphenyl) sulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or the same Nonafluorobutanesulfonate, dimethyl (4-hydroxynaphthyl) sulfonium trifluoromethanesulfonate, its heptaful Lopropanesulfonate or its nonafluorobutanesulfonate, trifluoromethanesulfonate of monophenyldimethylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, trifluoromethanesulfonate of diphenylmonomethylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate (4-methylphenyl) diphenylsulfonium trifluoromethanesulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate, (4-methoxyphenyl) diphenylsulfonium trifluoromethanesulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate , Trifluoromethanesulfonate of tri (4-tert-butyl) phenylsulfonium, its heptafluoropropanesulfonate or its nonafluorobutanesulfonate, trifluoromethanesulfonate of diphenyl (1- (4-methoxy) naphthyl) sulfonium, its heptafluoropropane Sulfonate or its nonafluorobutane sulfonate, di (1-naphthyl) phenylsulfonium trifluoromethane sulfonate, its heptafluoropropane sulfonate or its nonafluorobutane sulfonate. In addition, onium salts in which the anion portion of these onium salts is replaced with methanesulfonate, n-propanesulfonate, n-butanesulfonate, or n-octanesulfonate can also be used.

  In addition, in the general formula (b-1) or (b-2), an onium salt-based acid generator in which the anion moiety is replaced with the anion moiety represented by the general formula (b-3) or (b-4). Can also be used (the cation moiety is the same as (b-1) or (b-2)).

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

［式（Ｂ−１）中、Ｒ^３１、Ｒ^３２はそれぞれ独立に有機基を表す。］

[In formula (B-1), R ³¹ and R ³² each independently represents an organic group. ]

The organic groups of R ³¹ and R ³² are groups containing carbon atoms, and atoms other than carbon atoms (for example, hydrogen atoms, oxygen atoms, nitrogen atoms, sulfur atoms, halogen atoms (fluorine atoms, chlorine atoms, etc.), etc.) You may have.
As the organic group for R ³¹ , a linear, branched, or cyclic alkyl group or aryl group is preferable. These alkyl groups and aryl groups may have a substituent. There is no restriction | limiting in particular as this substituent, For example, a fluorine atom, a C1-C6 linear, branched or cyclic alkyl group etc. are mentioned. Here, “having a substituent” means that part or all of the hydrogen atoms of the alkyl group or aryl group are substituted with a substituent.
As an alkyl group, C1-C20 is preferable, C1-C10 is more preferable, C1-C8 is more preferable, C1-C6 is especially preferable, and C1-C4 is the most preferable. As the alkyl group, a partially or completely halogenated alkyl group (hereinafter sometimes referred to as a halogenated alkyl group) is particularly preferable. The partially halogenated alkyl group means an alkyl group in which a part of hydrogen atoms is substituted with a halogen atom, and the fully halogenated alkyl group means that all of the hydrogen atoms are halogen atoms. Means an alkyl group substituted with Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable. That is, the halogenated alkyl group is preferably a fluorinated alkyl group.
The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the aryl group, a partially or completely halogenated aryl group is particularly preferable. The partially halogenated aryl group means an aryl group in which a part of hydrogen atoms is substituted with a halogen atom, and the fully halogenated aryl group means that all of the hydrogen atoms are halogen atoms. Means an aryl group substituted with.
R ³¹ is particularly preferably an alkyl group having 1 to 4 carbon atoms or a fluorinated alkyl group having 1 to 4 carbon atoms which has no substituent.

As the organic group for R ³² , a linear, branched, or cyclic alkyl group, aryl group, or cyano group is preferable. As the alkyl group and aryl group for R ^32, the same alkyl groups and aryl groups as those described above for R ³¹ can be used.
R ³² is particularly preferably a cyano group, an alkyl group having 1 to 8 carbon atoms having no substituent, or a fluorinated alkyl group having 1 to 8 carbon atoms.

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

［式（Ｂ−２）中、Ｒ^３３は、シアノ基、置換基を有さないアルキル基またはハロゲン化アルキル基である。Ｒ^３４はアリール基である。Ｒ^３５は置換基を有さないアルキル基またはハロゲン化アルキル基である。］

[In Formula (B-2), R ³³ represents a cyano group, an alkyl group having no substituent, or a halogenated alkyl group. R ³⁴ is an aryl group. R ³⁵ represents an alkyl group having no substituent or a halogenated alkyl group. ]

［式（Ｂ−３）中、Ｒ^３６はシアノ基、置換基を有さないアルキル基またはハロゲン化アルキル基である。Ｒ^３７は２または３価の芳香族炭化水素基である。Ｒ^３８は置換基を有さないアルキル基またはハロゲン化アルキル基である。ｐ”は２または３である。］

[In Formula (B-3), R ³⁶ represents a cyano group, an alkyl group having no substituent, or a halogenated alkyl group. R ³⁷ is a divalent or trivalent aromatic hydrocarbon group. ^R38 is an alkyl group having no substituent or a halogenated alkyl group. p ″ is 2 or 3.]

In the general formula (B-2), the alkyl group or halogenated alkyl group having no substituent of R ³³ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and carbon atoms. Numbers 1 to 6 are most preferable.
R ³³ is preferably a halogenated alkyl group, more preferably a fluorinated alkyl group.
The fluorinated alkyl group for R ³³ is preferably such that the hydrogen atom of the alkyl group is 50% or more fluorinated, more preferably 70% or more, and still more preferably 90% or more.

As the aryl group of R ³⁴ , one hydrogen atom is removed from an aromatic hydrocarbon ring such as a phenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, an anthracyl group, or a phenanthryl group. And heteroaryl groups in which some of the carbon atoms constituting the ring of these groups are substituted with heteroatoms such as oxygen, sulfur, and nitrogen atoms. Among these, a fluorenyl group is preferable.
The aryl group of R ³⁴ may have a substituent such as an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. The alkyl group or halogenated alkyl group in the substituent preferably has 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. The halogenated alkyl group is preferably a fluorinated alkyl group.

The alkyl group or halogenated alkyl group having no substituent for R ³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbon atoms.
R ³⁵ is preferably a halogenated alkyl group, more preferably a fluorinated alkyl group, and most preferably a partially fluorinated alkyl group.
The fluorinated alkyl group in R ³⁵ preferably has 50% or more of the hydrogen atom of the alkyl group, more preferably 70% or more, and even more preferably 90% or more fluorinated. This is preferable because the strength of the acid is increased. Most preferred is a fully fluorinated alkyl group in which a hydrogen atom is 100% fluorine-substituted.

In the general formula (B-3), the alkyl group or halogenated alkyl group having no substituent for R ³⁶ is the same as the alkyl group or halogenated alkyl group having no substituent for R ^33. Is mentioned.
Examples of the divalent or trivalent aromatic hydrocarbon group for R ³⁷ include groups obtained by further removing one or two hydrogen atoms from the aryl group for R ³⁴ .
Examples of the alkyl group or halogenated alkyl group having no substituent of R ³⁸ include the same alkyl groups or halogenated alkyl groups having no substituent as R ³⁵ described above.
p ″ is preferably 2.

Specific examples of the oxime sulfonate acid generator include α- (p-toluenesulfonyloxyimino) -benzyl cyanide, α- (p-chlorobenzenesulfonyloxyimino) -benzyl cyanide, α- (4-nitrobenzenesulfonyloxy). Imino) -benzylcyanide, α- (4-nitro-2-trifluoromethylbenzenesulfonyloxyimino) -benzylcyanide, α- (benzenesulfonyloxyimino) -4-chlorobenzylcyanide, α- (benzenesulfonyl) Oxyimino) -2,4-dichlorobenzyl cyanide, α- (benzenesulfonyloxyimino) -2,6-dichlorobenzyl cyanide, α- (benzenesulfonyloxyimino) -4-methoxybenzyl cyanide, α- ( 2-Chlorobenzenesulfonyloxyimino) 4-methoxybenzylcyanide, α- (benzenesulfonyloxyimino) -thien-2-ylacetonitrile, α- (4-dodecylbenzenesulfonyloxyimino) -benzylcyanide, α-[(p-toluenesulfonyloxyimino) -4-methoxyphenyl] acetonitrile, α-[(dodecylbenzenesulfonyloxyimino) -4-methoxyphenyl] acetonitrile, α- (tosyloxyimino) -4-thienyl cyanide, α- (methylsulfonyloxyimino) -1-cyclo Pentenyl acetonitrile, α- (methylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (methylsulfonyloxyimino) -1-cycloheptenylacetonitrile, α- (methylsulfonyloxyimino) -1-cyclooctene Acetonitrile, α- (trifluoromethylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -cyclohexylacetonitrile, α- (ethylsulfonyloxyimino) -ethylacetonitrile, α- (propyl Sulfonyloxyimino) -propylacetonitrile, α- (cyclohexylsulfonyloxyimino) -cyclopentylacetonitrile, α- (cyclohexylsulfonyloxyimino) -cyclohexylacetonitrile, α- (cyclohexylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- ( Ethylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- (isopropylsulfonyloxyimino) -1-cyclope N-tenyl acetonitrile, α- (n-butylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- (ethylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (isopropylsulfonyloxyimino) -1-cyclohexenylacetonitrile , Α- (n-butylsulfonyloxyimino) -1-cyclohexenylacetonitrile, α- (methylsulfonyloxyimino) -phenylacetonitrile, α- (methylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (trifluoro Methylsulfonyloxyimino) -phenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) -p-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -p- Butoxy phenylacetonitrile, alpha-(propylsulfonyl oxyimino)-p-methylphenyl acetonitrile, alpha-like (methylsulfonyloxyimino)-p-bromophenyl acetonitrile.
Further, an oxime sulfonate-based acid generator disclosed in JP-A-9-208554 (paragraphs [0012] to [0014] [chemical formula 18] to [chemical formula 19]), WO2004 / 074242A2 (pages 65 to 85). The oxime sulfonate acid generators disclosed in Examples 1 to 40) of No. 1 can also be suitably used.
Moreover, the following can be illustrated as a suitable thing.

  Of the above exemplified compounds, the following four compounds are 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.
Further, diazomethane acid generators disclosed in JP-A-11-035551, JP-A-11-035552, and JP-A-11-035573 can also be suitably used.
Examples of poly (bissulfonyl) diazomethanes include 1,3-bis (phenylsulfonyldiazomethylsulfonyl) propane and 1,4-bis (phenylsulfonyldiazo) disclosed in JP-A-11-322707. Methylsulfonyl) butane, 1,6-bis (phenylsulfonyldiazomethylsulfonyl) hexane, 1,10-bis (phenylsulfonyldiazomethylsulfonyl) decane, 1,2-bis (cyclohexylsulfonyldiazomethylsulfonyl) ethane, 1,3 -Bis (cyclohexylsulfonyldiazomethylsulfonyl) propane, 1,6-bis (cyclohexylsulfonyldiazomethylsulfonyl) hexane, 1,10-bis (cyclohexylsulfonyldiazomethylsulfonyl) decane, etc. Door can be.

  As the component (B2), one type of acid generator may be used alone, or two or more types may be used in combination.

  The content of the component (B) in the positive resist composition for multilayer resists of the present invention is 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass with respect to 100 parts by mass of the component (A). 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.

<(D) component>
In the positive resist composition for multilayer resists of the present invention, a nitrogen-containing organic compound (D) (hereinafter referred to as the (D) component) is further added as an optional component in order to improve the resist pattern shape, the stability over time. It is preferable to contain.
Since a wide variety of components (D) have already been proposed, any known one may be used. Among them, aliphatic amines, particularly secondary aliphatic amines and tertiary aliphatic amines are used. preferable. Here, “aliphatic” in the claims and the specification is a relative concept with respect to aromatics, and is defined to mean a group, a compound, or the like that does not have aromaticity. “Aliphatic cyclic group” means a monocyclic group or polycyclic group having no aromaticity.
Examples of the aliphatic amine include an amine (alkyl amine or alkyl alcohol amine) or a cyclic amine in which at least one hydrogen atom of ammonia NH ₃ is substituted with an alkyl group or hydroxyalkyl group having 12 or less carbon atoms.
Specific examples of alkylamines and alkyl alcohol amines include monoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine; diethylamine, di-n-propylamine, di- -Dialkylamines such as 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-dodecylamine, and the like; diethanolamine, triethanolamine, diisopropanolamine Triisopropanolamine, di -n- octanol amines, alkyl alcohol amines tri -n- octanol amine. Among these, a trialkylamine having 5 to 10 carbon atoms is more preferable, tri-n-pentylamine and tri-n-octylamine are particularly preferable, and tri-n-pentylamine is most preferable.
Examples of the cyclic amine include heterocyclic compounds containing a nitrogen atom as a hetero atom. The heterocyclic compound may be monocyclic (aliphatic monocyclic amine) or polycyclic (aliphatic polycyclic amine).
Specific examples of the aliphatic monocyclic amine include piperidine and piperazine.
As the aliphatic polycyclic amine, those having 6 to 10 carbon atoms are preferable. Specifically, 1,5-diazabicyclo [4.3.0] -5-nonene, 1,8-diazabicyclo [5. 4.0] -7-undecene, hexamethylenetetramine, 1,4-diazabicyclo [2.2.2] octane, and the like.
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.

<Optional component>
The positive resist composition for multi-layer resists of the present invention includes an organic carboxylic acid and a phosphorus oxoacid as optional components for the purpose of preventing sensitivity deterioration and improving the resist pattern shape and stability with time. And at least one compound (E) selected from the group consisting of derivatives thereof and derivatives thereof (hereinafter, referred to as component (E)) can be contained.
As the organic carboxylic acid, for example, acetic acid, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, salicylic acid and the like are suitable.
Examples of phosphorus oxo acids and derivatives thereof include phosphoric acid, phosphonic acid, phosphinic acid and the like, and among these, phosphonic acid is particularly preferable.
Examples of the oxo acid derivative of phosphorus include esters in which the hydrogen atom of the oxo acid is substituted with a hydrocarbon group, and the hydrocarbon group includes an alkyl group having 1 to 5 carbon atoms and 6 to 6 carbon atoms. 15 aryl groups and the like.
Examples of phosphoric acid derivatives include phosphoric acid esters such as di-n-butyl phosphate and diphenyl phosphate.
Examples of phosphonic acid derivatives include phosphonic acid esters such as phosphonic acid dimethyl ester, phosphonic acid-di-n-butyl ester, phenylphosphonic acid, phosphonic acid diphenyl ester, and phosphonic acid dibenzyl ester.
Examples of the phosphinic acid derivatives include phosphinic acid esters such as phenylphosphinic acid.
(E) A component may be used individually by 1 type and may use 2 or more types together.
As the component (E), an organic carboxylic acid is preferable, and salicylic acid is particularly preferable.
(E) A component is used in the ratio of 0.01-5.0 mass parts per 100 mass parts of (A) component.

  The positive resist composition for multilayer resists of the present invention further contains miscible additives as desired, for example, additional resins for improving the performance of the resist film, surfactants for improving coatability, and dissolution. An inhibitor, a plasticizer, a stabilizer, a colorant, an antihalation agent, a dye, and the like can be appropriately added and contained.

The positive resist composition for multilayer resist of the present invention can be produced by dissolving the material in an organic solvent (hereinafter sometimes referred to as (S) component).
As the component (S), 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, lactones such as γ-butyrolactone;
Ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl-n-amyl ketone, methyl isoamyl ketone, 2-heptanone;
Polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol;
Compounds having an ester bond such as ethylene glycol monoacetate, diethylene glycol monoacetate, propylene glycol monoacetate, dipropylene glycol monoacetate, monomethyl ether, monoethyl ether, monopropyl of the polyhydric alcohols or the compound having an ester bond Derivatives of polyhydric alcohols such as ethers, monoalkyl ethers such as monobutyl ether or compounds having an ether bond such as monophenyl ether [in these, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME) Is preferred];
Cyclic ethers such as dioxane and esters such as methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate;
Examples include aromatic organic solvents such as anisole, ethyl benzyl ether, cresyl methyl ether, diphenyl ether, dibenzyl ether, phenetol, butyl phenyl ether, ethylbenzene, diethylbenzene, amylbenzene, isopropylbenzene, toluene, xylene, cymene, and mesitylene. be able to.
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.
Among these, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), ethyl lactate (EL), and γ-butyrolactone are preferable.
Moreover, the mixed solvent which mixed PGMEA and the polar solvent is preferable. The mixing ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, but is preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. It is preferable to be within the range.
More specifically, when EL is blended as a polar solvent, the mass ratio of PGMEA: EL is preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. Moreover, when mix | blending PGME as a polar solvent, the mass ratio of PGMEA: PGME becomes like this. Preferably it is 1: 9-9: 1, More preferably, it is 2: 8-8: 2, More preferably, it is 3: 7-7: 3.
In addition, as the component (S), 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.
Furthermore, as the component (S), a mixed solvent of the above-described mixed solvent of PGMEA and PGME and γ-butyrolactone is also preferable.
The amount of component (S) used is not particularly limited, but it is a concentration that can be applied to a substrate or the like, and is appropriately set according to the coating film thickness. -20% by mass, preferably 5-15% by mass.

As described above, the positive resist composition for a multilayer resist of the present invention has an excellent inhibitory effect on footing that is likely to occur when an upper resist layer is formed on an intermediate layer made of a silicone hard mask material. In the pattern forming method including the step of forming a resist laminate, it can be suitably used as a positive resist composition for forming an upper resist film, and good lithography characteristics can be obtained.
The reason for this is that the acid generator (B1) having a cation moiety represented by the general formula (b1-4) used in the present invention has a light wavelength in an exposure wavelength band (particularly the wavelength band of an ArF excimer laser). It is mentioned that absorption is effectively suppressed and the solubility in an organic solvent (resist solvent) used to dissolve various components of the resist is excellent. Therefore, it is considered that the positive resist composition for multilayer resists of the present invention is suppressed in light absorption by the blending of the component (B1) and the transparency of the resist composition is increased.
Further, it is considered that the component (B1) has good dispersibility in the resist film and is more uniformly distributed in the resist film than the conventional acid generator. For this reason, it is presumed that the acid generated from the component (B1) by exposure can diffuse more uniformly in the resist film than when a conventional acid generator is used.
In the present invention, the base component (A) having the structural unit (a1) and the acid generator (the component (B1)) are used in combination on the intermediate layer made of a silicone hard mask material. It is presumed that both the effect of suppressing the footing that easily occurs to form the upper resist layer and the effect of reducing the LWR can be obtained.
For the above reasons, the positive resist composition for multilayer resist of the present invention can be suitably used as a positive resist composition for forming an upper resist film in a pattern forming method including a step of forming a resist laminate. It is estimated that good lithography characteristics can be obtained.
According to the positive resist composition for a multilayer resist of the present invention, for example, line width roughness (LWR), resist pattern shape (particularly surface roughness of the resist pattern), mask error factor (MEF), exposure margin (EL margin) A resist pattern having good lithography characteristics such as
Note that MEF is a parameter that indicates how faithfully a mask pattern of different size can be reproduced when the mask size (line width and space width) is changed with the same exposure amount and a fixed pitch. The closer the MEF value is to 1, the better the mask reproducibility.
The EL margin is a parameter indicating the amount of change in the pattern size that accompanies a change in exposure amount. The larger the value, the smaller the amount of change.

≪Pattern formation method≫
The pattern forming method of the second aspect of the present invention includes a step of forming a lower organic film capable of dry etching on a substrate, and a step of forming an intermediate layer made of a silicone-based hard mask material on the lower organic film. A step of forming an upper layer resist film on the intermediate layer using the positive resist composition for multilayer resist of the first aspect of the present invention to form a resist laminate, and exposing the upper layer resist film. And developing to form a resist pattern.
The pattern forming method of the second aspect of the present invention can be performed, for example, as follows.

(Step of forming the lower organic film)
In the pattern forming method of the present invention, first, a resist composition or a resin solution for forming a lower organic film is applied on a substrate such as a silicon wafer with a spinner or the like, preferably 200 to 300 ° C., 30 Baking is performed under heating conditions for ˜300 seconds, preferably 60 to 180 seconds, to form a lower organic film.

  The lower organic film is an organic film that can be etched by a conventional dry etching method. This organic film is desirably insoluble in an alkaline developer used for development after exposure. By using such a lower organic film, first, a resist pattern is formed by performing selective exposure and alkali development of the upper resist film by lithography, and then using the resist pattern as a mask, for example, an oxide with a halogen-based gas. After the pattern is transferred to the intermediate layer using etching or the like, the lower layer organic film is dry-etched using the intermediate layer pattern as a mask, whereby the upper layer resist film and the intermediate layer resist pattern are transferred to the lower layer organic film. As a result, a pattern with a high aspect ratio can be formed without causing pattern collapse.

  The organic film material for forming the lower organic film does not necessarily require sensitivity to an electron beam or light like the upper resist film. In the manufacture of semiconductor elements and liquid crystal display elements, resists and resins that are generally used may be used.

Moreover, since it is necessary to transfer the upper resist pattern and the intermediate layer pattern to the lower organic film, the lower organic film is preferably a material that can be etched by oxygen plasma.
As such a material, it is easy to perform etching with oxygen plasma, and at the same time has strong resistance to fluorocarbon gas used for etching a silicon substrate or the like in a later process. Those having as a main component at least one selected from the group consisting of polyimides are preferably used.
Among these, a novolak resin and an acrylic resin having an alicyclic site or an aromatic ring in the side chain are preferably used because they are inexpensive and widely used and have excellent dry etching resistance in the subsequent steps.

As the novolak resin, those generally used in positive resist compositions can be used, and i-line and g-line positive resists containing novolak resin as a main component can also be used.
The novolac resin is, for example, a resin obtained by addition condensation of an aromatic compound having a phenolic hydroxyl group (hereinafter simply referred to as “phenols”) and an aldehyde under an acid catalyst.

  Examples of phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-butylphenol, m-butylphenol, p-butylphenol, 2, 3 -Xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol , P-phenylphenol, resorcinol, hydroquinone, hydroquinone monomethyl ether, pyrogallol, phloroglicinol, hydroxydiphenyl, bisphenol A, gallic acid, gallic acid ester, α-naphthol, β-naphthol and the like.

Examples of aldehydes include formaldehyde, furfural, benzaldehyde, nitrobenzaldehyde, and acetaldehyde.
The catalyst for the addition condensation reaction is not particularly limited. For example, hydrochloric acid, nitric acid, sulfuric acid, formic acid, oxalic acid, acetic acid and the like are used as the acid catalyst.
The novolak resin has a mass average molecular weight of 3000 to 10000, preferably 6000 to 9000, more preferably 7000 to 8000. If the mass average molecular weight is less than 3000, it may sublime when baked at a high temperature. If the mass average molecular weight exceeds 10,000, dry etching tends to be difficult, which is not preferable.

  As the novolak resin that can be used in the present invention, a commercially available one can be used, and in particular, the mass average molecular weight (Mw) is 5000 to 50000, preferably 8000 to 30000, and the molecular weight is 500 or less, preferably A novolak resin having a content of low nuclei of 200 or less in the gel permeation chromatography method is 1% by mass or less, preferably 0.8% by mass or less. The content of the low nucleus is preferably as small as possible, and is desirably 0% by mass.

The “low molecular weight having a molecular weight of 500 or less” is detected as a low molecular fraction having a molecular weight of 500 or less when analyzed by GPC using polystyrene as a standard. “Low molecular weight less than 500 molecular weight” includes monomers that have not been polymerized and those that have a low degree of polymerization, such as those in which 2 to 5 molecules of phenols are condensed with aldehydes, depending on the molecular weight. .
The content (mass%) of the low nuclei having a molecular weight of 500 or less is graphed by taking the analysis result by the GPC method with the fraction number on the horizontal axis and the concentration on the vertical axis, and the molecular weight of 500 or less with respect to the area under the entire curve. It is measured by determining the percentage (%) of the area under the curve of the low molecular fraction.

When the Mw of the novolak resin is 50000 or less, excellent embedding characteristics with respect to a substrate having fine irregularities are excellent, and when the Mw is 5000 or more, etching resistance to a fluorocarbon-based gas is excellent, which is preferable. .
In addition, when the content of the low-nuclear substance having a molecular weight of 500 or less is 1% by mass or less, the embedding characteristic with respect to the substrate having fine unevenness is improved. Although the reason why the embedding property is improved by reducing the content of the low nuclei is not clear, it is presumed that the degree of dispersion becomes small.

  As the acrylic resin, those generally used for positive resist compositions can be used. For example, a structural unit derived from a polymerizable compound having an ether bond and a polymerizable compound having a carboxyl group can be used. Mention may be made of acrylic resins containing derived structural units.

  Examples of the polymerizable compound having an ether bond include 2-methoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxy polyethylene glycol (meta And (meth) acrylic acid derivatives having an ether bond and an ester bond such as acrylate, methoxypolypropylene glycol (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate. These compounds can be used alone or in combination of two or more.

  Examples of the polymerizable compound having a carboxyl group include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; 2-methacryloyloxyethyl succinic acid, and 2-methacryloyloxyethyl. Examples include maleic acid, 2-methacryloyloxyethyl phthalic acid, 2-methacryloyloxyethyl hexahydrophthalic acid and other compounds having a carboxyl group and an ester bond, and acrylic acid and methacrylic acid are preferred. These compounds can be used alone or in combination of two or more.

  The soluble polyimide is a polyimide that can be made liquid by the organic solvent as described above.

  The lower organic film can be formed, for example, by applying a solution of a base material as described above onto a substrate according to a conventional method.

  The thickness of the lower organic film is preferably 50 to 500 nm, more preferably 100 to 400 nm. By setting the thickness of the lower organic film within this range, it is possible to form a resist pattern with a high aspect ratio and to obtain sufficient etching resistance during substrate etching.

(Step of forming the intermediate layer)
Next, a hard mask forming composition is applied onto the lower organic film with a spinner or the like, prebaked at a temperature of 70 to 130 ° C. for 40 to 180 seconds, preferably 60 to 90 seconds, and then 200 to 200- The intermediate layer is formed by baking at 250 ° C. for 60 to 120 seconds.

  There is no particular limitation on the material and forming method of the intermediate layer made of the silicone-based hard mask material, but since the matching with the positive resist composition for multilayer resist of the first aspect of the present invention is good, A hard mask forming composition containing a sun resin is preferably used. For example, the silsesquioxane resin suitably used here includes phenyl silsesquioxane / hydrogen silsesquioxane / methyl silsesquioxane / methyl silsesquioxane propionate copolymer, phenyl silsesquioxane, Mention may be made of copolymers such as sun / hydrogen silsesquioxane copolymers.

  The hard mask forming composition used in the step of forming the resist laminate is simply applied by a conventional spin coating method onto a substrate such as a silicon wafer having an organic film as a base material, and a desired hard mask. Can be formed. In the conventional resist process, considering that it is necessary to form an oxide film on a base material by vapor deposition and to apply a resist film thereon, the process is greatly simplified.

  The composition for forming a hard mask is dissolved in an appropriate solvent when used and used as a solution. As the solvent used in this case, the same solvent as the component (S) described above can be used.

  If desired, the hard mask forming composition may further include compatible additives such as sensitizers, additional resins, plasticizers, stabilizers or developed images to make them more visible. A commonly used colorant or the like can be added.

  An intermediate | middle layer can be formed by apply | coating the solution of the composition for hard mask formation mentioned above on the lower layer organic film mentioned above according to a conventional method, for example.

  The thickness of the intermediate layer is preferably 10 to 100 nm, more preferably 20 to 80 nm. By setting the thickness of the intermediate layer within this range, there are effects that a resist pattern can be formed with high resolution and sufficient resistance to dry etching can be obtained.

(Step of forming a resist laminate)
Next, on the intermediate layer formed as described above, a solution of the positive resist composition for multilayer resist (resist composition for forming the upper resist layer) of the first aspect of the present invention is applied with a spinner or the like. Then, pre-baking is performed for 40 to 120 seconds, preferably 60 to 90 seconds under a temperature condition of 80 to 150 ° C. to form an upper resist film, and a resist laminate in which a three-layer resist is laminated on the substrate is obtained.

  The thickness of the upper resist film is preferably 30 to 200 nm, more preferably 50 to 180 nm, and most preferably 70 to 150 nm. By setting the thickness of the upper resist film within this range, sufficient transparency is imparted to radiation in a shorter wavelength region than i-line, such as KrF excimer laser (248 nm) and ArF excimer laser (193 nm). In addition, the resist pattern can be formed with high resolution, and sufficient resistance to dry etching can be obtained.

  The total thickness of the resist laminate composed of the upper resist film, the intermediate layer, and the lower organic film is preferably 1 μm as a total from the balance of throughput considering the target aspect ratio and the time required for dry etching of the lower organic film. Hereinafter, it is more preferably 0.7 μm or less, and most preferably 0.5 μm or less. The total lower limit value is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.15 μm or more.

(Process for forming resist pattern)
A KrF excimer laser (248 nm), an ArF excimer laser (193 nm), or the like is selectively exposed to the upper resist film of the resist laminate. As this exposure, a commonly used exposure method can be used, and an immersion exposure (immersion lithography) method can also be adopted.

  Subsequently, PEB (post-exposure heating) is applied for 30 to 120 seconds, preferably 60 to 90 seconds, under a temperature condition of 80 to 150 ° C. Subsequently, this is developed using an alkali developer, for example, an aqueous solution of 0.1 to 10% by mass of tetramethylammonium hydroxide. In this manner, a resist pattern (upper layer resist pattern) faithful to the mask pattern can be formed on the upper layer resist film.

  In the pattern forming method of the present invention, the resist pattern can be used as a mask pattern to transfer and form a pattern (intermediate layer pattern) on the intermediate layer. For the formation of the intermediate layer pattern, the upper layer resist pattern is used as a mask, and the intermediate layer etchant (a gas capable of etching the intermediate layer), for example, when the intermediate layer is a silicon-based film, is oxide-etched with a halogen-based gas. In addition, these etchants and etching conditions can be performed by a well-known method.

Furthermore, a pattern (lower layer pattern) faithful to the mask pattern can be obtained by dry etching the lower organic layer using the resist pattern and this intermediate layer pattern as a mask pattern.
Known dry etching methods include chemical etching such as downflow etching and chemical dry etching; physical etching such as sputter etching and ion beam etching; and chemical and physical etching such as RIE (reactive ion etching). The method can be used.
The most common dry etching is parallel plate RIE. In this method, first, a resist laminate is put in a chamber of an RIE apparatus, and a necessary etching gas is introduced. When a high frequency voltage is applied to the holder of the resist laminate placed in parallel with the upper electrode in the chamber, the gas is turned into plasma. In the plasma, there are charged particles such as positive and negative ions and electrons, and neutral active species. When these etching species are adsorbed on the lower resist layer, a chemical reaction occurs, the reaction product is detached from the surface and exhausted to the outside, and etching proceeds.
Examples of the etching gas include oxygen and sulfur dioxide. Etching with oxygen plasma is preferably used because it has a high resolution and is widely used.

  A fine pattern can also be formed on the substrate by etching the substrate using the lower layer pattern thus obtained as a mask. As an etching method at this time, an etching method using a halogen-based gas can be preferably used. The pattern obtained as described above can be used, for example, for manufacturing a semiconductor or the like.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Example 1, Comparative Examples 1 and 2)
<Resin component (A)>
The polymer (A) -1 as the component (A) used in Examples and Comparative Examples is shown below.
Polymer (A) -1 was synthesized by the following procedure. That is, PGMEA was put in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer under a nitrogen atmosphere, and the temperature of the hot water bath was raised to 80 ° C. while stirring.
Next, 2,2′-azobisisobutyronitrile (AIBN), PGMEA, and a monomer (2-methyl-2-adamantyl methacrylate) for deriving each structural unit of the polymer (A) -1 as a polymerization initiator / Α-methacryloyloxy γ-butyrolactone / 3-hydroxy-1-adamantyl acrylate = 3/5/2 (molar ratio)) is used for 6 hours at a constant rate using a dropping device. Was dropped into the flask, and then kept at 80 ° C. for 1 hour. Thereafter, the reaction solution was returned to room temperature.
Next, the obtained reaction solution was dropped into about 30 times amount of methanol with stirring to obtain a colorless precipitate. The resulting precipitate was filtered off, and the precipitate was washed in about 30 times the amount of methanol used for the monomer used for the polymerization. And this precipitate was separated by filtration and it dried at 50 degreeC under pressure reduction for about 40 hours, and the polymer (A) -1 was obtained.
In addition, the mass average molecular weight (Mw) and dispersity (Mw / Mn) of the following polymer (A) -1 were written together. The mass average molecular weight (Mw) and dispersity (Mw / Mn) were determined on a polystyrene conversion basis by gel permeation chromatography (GPC).
The composition ratio was calculated by carbon NMR. In the chemical formula, the number attached to the lower right of the structural unit indicates the ratio (mol%) of each structural unit in the polymer.

（Ｍｗ：１００００、Ｍｗ／Ｍｎ：２．０）

(Mw: 10000, Mw / Mn: 2.0)

<Preparation of positive resist composition solution>
Each component shown in Table 1 was mixed and dissolved to prepare a positive resist composition solution.

Each abbreviation in Table 1 has the following meaning. Moreover, the numerical value in [] is a compounding quantity (mass part).
(B) -1: An acid generator represented by the following chemical formula (b1-41).

(B) -2: Di (1-naphthyl) phenylsulfonium nonafluorobutanesulfonate.
(B) -3: (4-methylphenyl) diphenylsulfonium nonafluorobutanesulfonate.
(D) -1: tri-n-pentylamine.
(E) -1: salicylic acid.
(S) -1: γ-butyrolactone.
(S) -2: Mixed solvent of PGMEA / PGME = 6/4 (mass ratio).

<Evaluation of lithography properties>
A resist pattern was formed using the obtained positive resist composition solution, and the following lithography characteristics were evaluated.

[Resist pattern formation]
A resist laminate was manufactured by the following procedure, and a resist pattern was formed using the resist laminate.
First, a base material solution containing a novolak resin was applied onto an 8-inch silicon wafer using a spinner, and soft-baked at 230 ° C. for 90 seconds to form a lower organic film having a thickness of 270 nm.
Next, on the lower layer, a hard mask forming composition (phenylsilsesquioxane / hydrogen silsesquioxane / methylsilsesquioxane / methylsilsesquioxane propionate copolymer was mixed with PGMEA and EL (mass (6/4) (solid content concentration: 2.5% by mass)) was applied using a spinner and soft-baked at 90 ° C. for 90 seconds, followed by baking at 250 ° C. for 90 seconds. As a result, a hard mask layer (intermediate layer) having a thickness of 30 nm was formed.
Next, the positive resist composition solutions of Example 1 and Comparative Examples 1 and 2 were applied to the intermediate layer using a spinner and pre-baked on a hot plate at 110 ° C. for 60 seconds. By performing (PAB) treatment and drying, a positive resist layer (upper resist film) having a film thickness of 150 nm was formed, and a resist laminate in which a three-layer resist layer was laminated on the substrate was obtained.

Next, an ArF excimer laser (193 nm) was selectively irradiated through the mask pattern by an ArF exposure apparatus NSR-S302 (manufactured by Nikon; NA (numerical aperture) = 0.60, 2/3 annular illumination). . Then, a post-exposure heating (PEB) treatment was performed at each temperature shown in Table 2 under conditions of 60 seconds, and further a condition of 30 seconds with a 2.38 mass% tetramethylammonium hydroxide (TMAH) aqueous solution at 23 ° C. And then rinsed with pure water for 30 seconds and shaken and dried to form a line-and-space (1: 1) resist pattern (L / S pattern) with a line width of 120 nm and pitch The optimum exposure amount (sensitivity: Eop, mJ / cm ² ) at which a 240 nm L / S pattern was formed was determined.

[Line width roughness (LWR)]
In the line width of the L / S pattern having a line width of 120 nm and a pitch of 240 nm formed by the Eop, a side length SEM (manufactured by Hitachi, Ltd., trade name: S-9220) was used to measure five locations in the longitudinal direction of the line, From the result, a triple value (3 s) of the standard deviation (s) was calculated as a scale indicating LWR. The results are shown in Table 2.
Note that the smaller the value of 3s, the smaller the roughness of the line width, which means that a resist pattern with a more uniform width was obtained.

From the results in Table 2, it was confirmed that Example 1 according to the present invention had a smaller LWR value and a resist pattern with a more uniform width than that of Comparative Example 1.
Further, in Comparative Example 1, the cross section of the L / S pattern is a skirt shape, and footing occurs between the intermediate layer and the upper resist film, whereas in Example 1 according to the present invention, The cross-sectional shape of the L / S pattern was rectangular.
Further, in Comparative Example 2, the cross section of the L / S pattern was a skirt shape, and footing occurred between the intermediate layer and the upper resist film. Regarding LWR, footing was intense, so it was not necessary to evaluate it.
From the above results, Example 1 according to the present invention can reduce LWR and has an effect of suppressing footing that is likely to occur when an upper resist layer is formed on an intermediate layer made of a silicone-based hard mask material. It was confirmed that it was excellent.

Claims (7)

In the step of forming a lower organic film capable of dry etching on a substrate and the step of forming an intermediate layer made of a silicone-based hard mask material on the lower organic film, used on the intermediate layer,
A positive resist composition for a multilayer resist comprising a base material component (A) whose alkali solubility is increased by the action of an acid and an acid generator component (B) which generates an acid upon exposure,
The acid generator component (B) contains an acid generator (B1) having a cation moiety represented by the following general formula (b1-4), and a positive resist composition for multilayer resists.

  The positive resist composition for a multilayer resist according to claim 1, wherein the substrate component (A) is a resin component (A1) whose alkali solubility is increased by the action of an acid.   The positive resist composition for a multilayer resist according to claim 2, wherein the resin component (A1) has a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group.   The positive resist composition for multilayer resist according to claim 3, wherein the resin component (A1) further comprises a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group.   The positive resist composition for a multilayer resist according to claim 3 or 4, wherein the resin component (A1) further comprises a structural unit (a3) derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group.   Furthermore, the positive resist composition for multilayer resists as described in any one of Claims 1-5 containing a nitrogen-containing organic compound (D).   The process of forming the lower layer organic film which can be dry-etched on a board | substrate, the process of forming the intermediate | middle layer which consists of a silicone type hard mask material on this lower layer organic film, On this intermediate | middle layer, Claim 1-6 Forming an upper resist film using the positive resist composition for multilayer resist according to any one of the above to form a resist laminate, exposing the upper resist film, and developing to form a resist pattern A pattern forming method comprising the steps of: