JP6668825B2 - Radiation-sensitive resin composition and method for forming resist pattern - Google Patents

Description

  The present invention relates to a radiation-sensitive resin composition and a method for forming a resist pattern.

  2. Description of the Related Art A resist pattern forming method by photolithography is used for forming various electronic devices such as a semiconductor device and a liquid crystal device. In this method of forming a resist pattern, for example, a radiation-sensitive resin composition for forming a resist pattern on a substrate is used. The radiation-sensitive resin composition generates an acid in the exposed portion by irradiation with radiation such as far ultraviolet rays such as ArF excimer laser light, electromagnetic waves such as extreme ultraviolet rays (Extreme Ultraviolet: EUV), and charged particle beams such as electron beams. Then, the catalytic action of the acid causes a difference in the dissolution rate of the exposed part and the unexposed part in the developing solution to form a resist pattern on the substrate.

  Such a radiation-sensitive resin composition not only has high resolution of a resist pattern to be formed and is excellent not only in rectangular shape in cross-sectional shape but also in Line Width Roughness (LWR) performance, development defect suppressing property and the like. It is required that a high-precision pattern having an excellent depth of focus and a high yield can be obtained. In response to this requirement, various studies have been made on the structure of the polymer contained in the radiation-sensitive resin composition, and by having a lactone structure such as a butyrolactone structure or a norbornane lactone structure, the resist pattern can be adhered to the substrate. It is known that these properties can be improved while improving the performance (see JP-A-11-212265, JP-A-2003-5375 and JP-A-2008-83370).

  However, at present, when the resist pattern is miniaturized to a line width of 45 nm or less, the required level of the performance is further increased, and the conventional radiation-sensitive resin composition cannot satisfy these requirements. Not done. Also, recently, in order to further enhance the above-mentioned LWR performance and the like, it is also required to have excellent film shrinkage suppression during post-exposure bake (PEB). Further, the resist pattern is required to have high performance such as MEEF (Mask Error Enhancement Factor) performance.

JP-A-11-212265 JP 2003-5375 A JP 2008-83370 A

  The present invention has been made on the basis of the above circumstances, and has LWR performance, resolution, rectangularity of a cross-sectional shape, depth of focus, MEEF performance, development defect suppression property, and film shrinkage suppression property (hereinafter, referred to as “film shrinkage property”). It is an object of the present invention to provide a radiation-sensitive resin composition having excellent lithography performance) and a method for forming a resist pattern using the same.

（式（１）中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４は、それぞれ独立して、水素原子、フッ素原子、メチル基又はトリフルオロメチル基である。Ｒ^５及びＲ^６は、それぞれ独立して、水素原子又は炭素数１〜２０の１価の有機基である。Ｌは、炭素数２〜８のアルキレン鎖であって、上記アルキレン鎖が有する水素原子の一部又は全部を置換基で置換した基又は上記アルキレン鎖の炭素−炭素間に硫黄原子若しくは窒素原子を含む基である。）
The radiation-sensitive resin composition according to one embodiment of the present invention (hereinafter, also referred to as “radiation-sensitive resin composition (I)”) made to solve the above problem is represented by the following formula (1). A first polymer having a structural unit (hereinafter, also referred to as “structural unit (I)”) (hereinafter, also referred to as “[A] polymer”), a radiation-sensitive acid generator (hereinafter, referred to as “[B] acid generating ) And a solvent (hereinafter, also referred to as “[C] solvent”).

(In the formula (1), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ⁵ and R ⁶ are each independently And is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, L is an alkylene chain having 2 to 8 carbon atoms, and a part or all of the hydrogen atoms of the alkylene chain is a substituent. Or a group containing a sulfur atom or a nitrogen atom between carbon and carbon of the alkylene chain.)

  According to another aspect of the present invention, there is provided a resist pattern forming method for forming a resist film, exposing the resist film, and developing the exposed resist film. And the resist film is formed of the radiation-sensitive resin composition (I).

（式（１’）中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４は、それぞれ独立して、水素原子、フッ素原子、メチル基又はトリフルオロメチル基である。Ｒ^５及びＲ^６は、それぞれ独立して、水素原子又は炭素数１〜２０の１価の有機基である。Ｌ’は、炭素数２〜８のアルキレン鎖、上記アルキレン鎖が有する水素原子の一部又は全部を置換基で置換した基又は上記アルキレン鎖の炭素−炭素間に硫黄原子、窒素原子若しくは酸素原子を含む基である。）
A method for forming a resist pattern according to another embodiment of the present invention, which has been made to solve the above problems, includes a step of forming a resist film, a step of exposing the resist film, and a step of exposing the exposed resist film to an organic solvent. A resist pattern forming method in which the resist film is formed with a radiation-sensitive resin composition (hereinafter, also referred to as “radiation-sensitive resin composition (II)”). In addition, the radiation-sensitive resin composition (II) has a polymer having a structural unit represented by the following formula (1 ′) (hereinafter, also referred to as a structural unit (I ′)) (hereinafter referred to as “[A ′] polymer”). ), A radiation-sensitive acid generator, and a solvent.

(In the formula (1 ′), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ⁵ and R ⁶ are each Independently, it is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, and L ′ is an alkylene chain having 2 to 8 carbon atoms, or a part or all of the hydrogen atoms of the alkylene chain is a substituent. A substituted group or a group containing a sulfur atom, a nitrogen atom or an oxygen atom between carbon and carbon of the alkylene chain.)

  Here, the “organic group” refers to a group containing at least one carbon atom. The “hydrocarbon group” includes a chain hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. This “hydrocarbon group” may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. The term “chain hydrocarbon group” refers to a hydrocarbon group that does not include a cyclic structure but includes only a chain structure, and includes both a linear hydrocarbon group and a branched hydrocarbon group. “Alicyclic hydrocarbon group” refers to a hydrocarbon group containing only an alicyclic structure as a ring structure and not containing an aromatic ring structure, and includes a monocyclic alicyclic hydrocarbon group and a polycyclic alicyclic group. Contains both hydrocarbon groups. However, it is not necessary to be composed of only the alicyclic structure, and a part thereof may include a chain structure. “Aromatic hydrocarbon group” refers to a hydrocarbon group containing an aromatic ring structure as a ring structure. However, it is not necessary to be composed of only an aromatic ring structure, and a part thereof may include a chain structure or an alicyclic structure. "Number of ring members" refers to the number of atoms constituting an aromatic ring structure, an aromatic heterocyclic structure, an alicyclic structure, and an aliphatic heterocyclic structure. Means the number of atoms to perform.

  According to the radiation-sensitive resin composition and the method for forming a resist pattern of the present invention, a resist pattern having excellent LWR performance, resolution, rectangular cross-sectional shape, depth of focus, MEEF performance, development defect suppression properties, and film shrinkage suppression properties Can be formed. Therefore, the radiation-sensitive resin composition and the method for forming a resist pattern can be suitably used for the manufacture of semiconductor devices, which are expected to be further miniaturized in the future.

<Radiation-sensitive resin composition (I)>
The radiation-sensitive resin composition (I) according to one embodiment of the present invention contains a polymer [A], an acid generator [B], and a solvent [C]. The radiation-sensitive resin composition (I) is preferably [D] an acid diffusion controller as a suitable component, or a polymer having a higher fluorine atom content than the [A] polymer (hereinafter, also referred to as “[E] polymer”). And [A] a second polymer having a lower fluorine atom content than the polymer and having an acid dissociable group (hereinafter, also referred to as “[F] polymer”) and [G] a localization accelerator. And other optional components may be contained as long as the effects of the present invention are not impaired.

  The radiation-sensitive resin composition (I) may contain only a base polymer as a polymer component, or may contain a water-repellent polymer additive in addition to the base polymer. The “base polymer” refers to a polymer that is a main component of a resist film formed from the radiation-sensitive resin composition (I), and is preferably 50% by mass based on the entire polymer constituting the resist film. It refers to a polymer occupying the above. “Main component” refers to the component with the highest content. The “water-repellent polymer additive” is a polymer that tends to be unevenly distributed on the surface layer of a formed resist film by being contained in the radiation-sensitive resin composition (I). A polymer having a higher hydrophobicity than the polymer serving as the base polymer tends to be unevenly distributed on the surface layer of the resist film, and can function as a water-repellent polymer additive.

  The radiation-sensitive resin composition (I) can contain a water-repellent polymer additive, thereby suppressing elution of an acid generator and the like from the resist film, and have a high dynamic contact angle on the surface of the formed resist film. , The surface of the resist film can exhibit excellent drainage characteristics. Accordingly, in the immersion exposure process, high-speed scan exposure can be performed without having to separately form an upper layer film for shielding the resist film surface from the immersion medium.

  When the radiation-sensitive resin composition (I) contains a water-repellent polymer additive, the lower limit of the content of the water-repellent polymer additive is 0.1 part by mass with respect to 100 parts by mass of the base polymer. Is preferably 0.3 part by mass, more preferably 0.5 part by mass. The upper limit of the content of the water-repellent polymer additive is preferably 20 parts by mass, more preferably 15 parts by mass, and still more preferably 10 parts by mass. The lower limit of the content of the base polymer in the radiation-sensitive resin composition (I) is preferably 70% by mass, more preferably 80% by mass, based on the total solid content in the radiation-sensitive resin composition (I). preferable.

  The water-repellent polymer additive is preferably a polymer having a fluorine atom, and more preferably the fluorine atom content is larger than the fluorine atom content of the base polymer. When the fluorine atom content of the water-repellent polymer additive is larger than the fluorine atom content of the base polymer, in the formed resist film, the tendency of the water-repellent polymer additive to be unevenly distributed on its surface layer is increased. In addition, characteristics due to the hydrophobicity of the water-repellent polymer additive, such as high water-repellency of the resist film surface, are more effectively exhibited.

The lower limit of the fluorine atom content of the polymer constituting the water-repellent polymer additive is preferably 3% by mass, more preferably 6% by mass, still more preferably 10% by mass, and particularly preferably 15% by mass. The fluorine atom content (% by mass) can be calculated from the structure of the polymer obtained by ¹³ C-NMR measurement.

  As an embodiment of the polymer component in the radiation-sensitive resin composition (I), (1) when the polymer (A) is contained as the base polymer, (2) the polymer (A) as the base polymer and When another [A] polymer as a water-repellent polymer additive is contained, (3) a [A] polymer as a base polymer and an [E] polymer as a water-repellent polymer additive are contained. In such a case, (4) a case where the composition contains a polymer [F] as a base polymer and a polymer [A] as a water-repellent polymer additive is exemplified. Hereinafter, each component will be described.

<[A] polymer>
[A] The polymer is a polymer having the structural unit (I). The radiation-sensitive resin composition (I) is characterized in that the polymer (A) has the structural unit (I), so that the LWR performance, the resolution, the rectangular shape of the cross-sectional shape, the depth of focus, the MEEF performance, and the development defect suppressing property are obtained. In addition, a resist pattern having excellent film shrinkage suppression properties can be formed. Although the reason why the radiation-sensitive resin composition (I) has the above-described structure to achieve the above-mentioned effects is not necessarily clear, it can be inferred, for example, as follows. That is, the alkylene chain of L (hereinafter also referred to as “group (L)”) becomes bulky by having a substituent as in the above formula (1), and the main chain of the polymer [A] is The rigidity is high. Further, since the alkylene chain of L contains a sulfur atom or a nitrogen atom having a moderately high basicity, the interaction between the acid generated from the acid generator [B] in the resist film and the polymer [A] is prevented. Moderately large. As a result, the polymer [A] can appropriately reduce the diffusion length of the acid generated from the acid generator [B], and the solubility in a developer is improved. Therefore, it is considered that the lithography performance of the radiation-sensitive resin composition (I) can be improved.

  The polymer [A] as the base polymer in the radiation-sensitive resin composition (I) (hereinafter also referred to as “[A1] polymer”) contains an acid-dissociable group in addition to the structural unit (I). It preferably has a structural unit (II) and a structural unit (III) containing a polar group, and may have a structural unit other than the structural units (I) to (III).

  The polymer (A) (hereinafter also referred to as “[A2] polymer)” as a water-repellent polymer additive in the radiation-sensitive resin composition (I) includes the above structural unit in addition to the structural unit (I). (II), and may have a structural unit (IV) containing a fluorine atom, which is a structural unit other than the structural unit (III) and the structural unit (I). It may have a structural unit other than (IV).

  [A] The polymer may have one or more of the above structural units. Hereinafter, each structural unit will be described.

[Structural unit (I)]
The structural unit (I) is a structural unit represented by the following formula (1).

In the above formula (1), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ⁵ and R ⁶ are each independently a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. L is an alkylene chain having 2 to 8 carbon atoms, a group in which part or all of the hydrogen atoms of the alkylene chain is substituted with a substituent, or a sulfur atom or a nitrogen atom between carbon and carbon of the alkylene chain. It is a group containing.

As R ¹ , R ² , R ³ and R ⁴ , a hydrogen atom and a methyl group are preferable, and a hydrogen atom is more preferable, from the viewpoint of copolymerizability of a monomer giving the structural unit (I).

Examples of the monovalent organic group having 1 to 20 carbon atoms represented by R ⁵ and R ⁶ include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a carbon-carbon bond or a bond of the hydrocarbon group. A group (a) containing a divalent hetero atom-containing group at the terminal on the side, a group obtained by substituting a part or all of the hydrogen atoms contained in the hydrocarbon group and the group (a) with a monovalent hetero atom-containing group, or the like. No.

  Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent linear hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a carbon number having 1 to 20 carbon atoms. And 6-20 monovalent aromatic hydrocarbon groups.

Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a sec-butyl group, an alkyl group such as a t-butyl group;
Alkenyl groups such as an ethenyl group, a propenyl group and a butenyl group;
Alkynyl groups such as an ethynyl group, a propynyl group and a butynyl group are exemplified.

Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include cycloalkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group, cyclodecyl group and cyclododecyl group;
Cycloalkenyl groups such as cyclobutenyl group, cyclopentenyl group, cyclohexenyl group, cyclooctenyl group and cyclodecenyl group;
Polycyclic alicyclic groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, a bicyclo [2.2.2] octanyl group, a tetracyclododecyl group, a tricyclo [3.3.1.1 ^3,7 ] decanyl group A saturated hydrocarbon group;
Examples include a polycyclic alicyclic unsaturated hydrocarbon group such as a norbornenyl group, a bicyclo [2.2.2] octenyl group, a tricyclodecenyl group, and a tetracyclododecenyl group.

Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group;
And aralkyl groups such as benzyl group, phenethyl group, phenylpropyl group and naphthylmethyl group.

As the bivalent hetero atom-containing group, for example -O -, - CO -, - S -, - CS -, - SO 2 -, - NR'-, group formed by combining two or more of these Is mentioned. R ′ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms.

  Examples of the monovalent hetero atom-containing group include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, a hydroxy group, a carboxy group, a cyano group, an amino group, a sulfanyl group (—SH), and the like. .

Examples of the monovalent organic group represented by R ⁵ and R ⁶ include an acid dissociable group. The acid dissociable group is a group that dissociates with an acid generated from the acid generator [B] upon exposure to produce a polar group such as a carboxyl group. Preferably, at least one of R ⁵ and R ⁶ is an acid dissociable group. When at least one of R ⁵ and R ⁶ is an acid dissociable group, the solubility of the polymer [A] can be more appropriately adjusted, and as a result, the depth of focus of the radiation-sensitive resin composition (I) can be adjusted. , LWR performance and the like can be further improved.

  Examples of the acid dissociable group include a group represented by the following formula (a-1).

In the above formula (a-1), ^RA2 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ^A3 and R ^A4 are each independently a monovalent linear hydrocarbon group having 1 to 20 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or these groups are It represents an alicyclic structure having 3 to 20 ring members which is combined with a carbon atom to which they are bonded.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by ^{R A2,} for example a methyl group, an ethyl group, a propyl group, an isopropyl group, n- butyl group, isobutyl group, sec- butyl group, n- Alkyl groups such as pentyl group and n-hexyl group;
Alkenyl groups such as an ethenyl group, a propenyl group and a butenyl group;
A chain hydrocarbon group such as an alkynyl group such as an ethynyl group, a propynyl group, and a butynyl group;
Cycloalkyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group, cyclodecyl group and cyclododecyl group;
Cycloalkenyl groups such as cyclobutenyl group, cyclopentenyl group, cyclohexenyl group, cyclooctenyl group and cyclodecenyl group;
Polycyclic alicyclic groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, a bicyclo [2.2.2] octanyl group, a tetracyclododecyl group, a tricyclo [3.3.1.1 ^3,7 ] decanyl group A saturated hydrocarbon group;
An alicyclic hydrocarbon group such as a polycyclic alicyclic unsaturated hydrocarbon group such as a norbornenyl group, a bicyclo [2.2.2] octenyl group, a tricyclodecenyl group, and a tetracyclododecenyl group;
Aryl groups such as phenyl, tolyl, xylyl, naphthyl and anthryl groups;
And aromatic hydrocarbon groups such as aralkyl groups such as benzyl group, phenethyl group and naphthylmethyl group.

As R ^A2 , an alkyl group, a cycloalkyl group, a polycyclic alicyclic saturated hydrocarbon group and a phenyl group are preferable, and a methyl group, an ethyl group, an isopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, and an adamantyl group are preferred. Is more preferred.

Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms represented by R ^A3 and R ^A4 include the same groups as the chain hydrocarbon groups exemplified as the monovalent hydrocarbon group of R ^A2. And the like.

Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by R ^A3 and R ^A4 include the same as the alicyclic hydrocarbon group exemplified as the monovalent hydrocarbon group of R ^A2. And the like.

Examples of the alicyclic structure having 3 to 20 ring members in which the groups of R ^A3 and R ^A4 are combined with each other and formed with a carbon atom to which they are bonded include, for example, a cyclopropane structure, a cyclobutane structure, a cyclopentane structure, a cyclohexane structure, and a cyclohexane structure. Cycloalkane structures such as octane structure and cyclodecane structure;
Examples include a polycyclic alicyclic saturated hydrocarbon structure such as a norbornane structure, an adamantane structure, a tricyclodecane structure, and a tetracyclododecane structure.

As R ^A3 and R ^A4 , an alkyl group is preferable, and a methyl group and an ethyl group are more preferable. Further, as R ^A3 and R ^A4 , an alicyclic structure composed of R ^A3 and R ^A4 combined with each other and a carbon atom to which they are bonded is preferable, and such alicyclic structures include cyclopentane structure and cyclohexane. The structure, cyclooctane structure and adamantane structure are preferred.

  As the group represented by the formula (a-1), specifically, groups represented by the following formulas (a-1-a) to (a-1-d) (hereinafter referred to as “group (I-1) -A) to (I-1-d)).

In the above formulas (a-1-a) to (a-1-d), R ^{A2 to} R ^A4 have the same meaning as in the above formula (a-1). n _a is an integer of 1 to 4.

As the _{n a,} preferably 1, 2 and 4, more preferably 1.

  Specific examples of the groups (I-1-a) to (I-1-d) "include groups represented by the following formulas.

  In the above formula, each * is a bond.

The monovalent organic group represented by R ⁵ and R ^6, it is also preferable that at least one of R ⁵ and R ⁶ is a group containing a polar group. When at least one of R ⁵ and R ^{6 is} a group containing a polar group, the solubility of the polymer (A) can be more appropriately adjusted, and as a result, the lithography of the radiation-sensitive resin composition (I) can be performed. The performance can be further improved.

  Examples of the polar group in the group containing a polar group include a lactone structure-containing group, a cyclic carbonate structure-containing group, a sultone structure-containing group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. And the like.

  Examples of the lactone structure-containing group include a group represented by the following formula.

  In the above formula, each * is a bond.

  Examples of the cyclic carbonate structure-containing group include a group represented by the following formula.

  In the above formula, each * is a bond.

  Examples of the sultone structure-containing group include a group represented by the following formula.

  In the above formula, each * is a bond.

  Examples of the group containing a phenolic hydroxyl group include, for example, groups represented by the following formulas (f-1) to (f-5) (hereinafter, also referred to as “groups (III-1) to (III-5)”). ).

  In the above formulas (f-1) to (f-5), each * represents a bond.

  Of these, groups (III-1) and (III-2) are preferred, and group (III-1) is more preferred.

  Examples of the group containing an alcoholic hydroxyl group, a cyano group, a nitro group, and a sulfonamide group include, for example, groups represented by the following formulas.

  In the above formula, each * is a bond.

(Group (L))
The group (L) is an alkylene chain having 2 to 8 carbon atoms, a group in which part or all of the hydrogen atoms of the alkylene chain is substituted with a substituent, or a sulfur atom or a carbon atom between the carbon atoms of the alkylene chain or It is a group containing a nitrogen atom.

  Examples of the substituent that replaces a hydrogen atom of the alkylene chain represented by L include a fluorine atom, a nitro group, and a monovalent group having 1 to 10 carbon atoms that replace one of the hydrogen atoms of the alkylene chain. And a divalent organic group having 1 to 10 carbon atoms as a substituent for substituting two hydrogen atoms of the alkylene chain with one group.

Examples of the organic group having 1 to 10 carbon atoms include the organic groups having 1 to 10 carbon atoms among the groups exemplified as the monovalent organic groups having 1 to 20 carbon atoms represented by R ⁵ and R ⁶ , Among the groups obtained by removing one hydrogen atom from the groups exemplified as monovalent organic groups having 1 to 20 carbon atoms represented by ⁵ and R ⁶ , divalent organic groups having 1 to 10 carbon atoms and the like can be mentioned. . When the substituent is a divalent organic group having 1 to 10 carbon atoms, one of the hydrogen atoms of the alkylene chain is substituted by one bond of the divalent organic group, and Is replaced by the other bond.

The substituent that substitutes for the hydrogen atom of the alkylene chain represented by L includes a [B] interaction between the acid generated from the acid generator and the [A] polymer in a more appropriate manner to control the depth of focus. And from the viewpoint of improving the LWR performance and the like, a fluorine atom, a nitro group, a monovalent chain hydrocarbon group, a carbon-carbon of the chain hydrocarbon group or a divalent hetero atom-containing group at the terminal of the bond side. Monovalent group, monovalent group containing a divalent heteroatom-containing group at the carbon-carbon end of the alicyclic hydrocarbon group or at the end of the bond side, a divalent chain hydrocarbon group and a chain carbon atom A divalent group containing a divalent heteroatom-containing group at the carbon-carbon end of the hydrogen group or at the end of the bond is preferably an alkyl group, -CO- at the end of the alkyl group between the carbon and carbon or at the end of the bond. , _-SO 2 -, - _SO 2 O-group containing a carbon alicyclic hydrocarbon group - carbon-carbon or A group containing -COO- at the terminal of the bond side and a group containing -O-, -CO-, -COO- between carbon-carbon of the alkylene group or at the terminal of the bond side are more preferable, and a fluorine atom, a nitro group , alkyl group, carbon atoms in the alkyl group - group and carbon alkylene group containing - _- -SO 2 at the terminal carbon-carbon or a bond side groups containing O- at the end of the carbon-carbon or a bond side is more preferable.

The sulfur atoms contained in the carbon-carbon, for example -S- sulfur atom, -SO _- - alkylene chain carbons represented by L, _- SO 2 -, - sulfur atom contained in SO 2 NH-, etc., etc. Is mentioned.

As the sulfur atom contained between the carbon and carbon of the alkylene chain represented by L, the interaction between the acid generated from the [B] acid generator in the resist film and the [A] polymer can be more appropriately determined. adjusted, from the viewpoint of improving the lithographic performance, sulfur atoms -S-, -SO- and -SO ₂ - sulfur atom contained in the preferred.

Examples of the nitrogen atoms contained in the carbon-carbon, such as ^-NR 7 - - carbon of the alkylene chain represented by L, - NO -, - NHCO -, - SO 2 NH -, - N + R 8 R 9 - , etc. And the like. R ⁷ is a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. R ⁸ and R ⁹ are each independently a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms, or a group having 3 to 3 ring members together with a nitrogen atom to which these groups are combined and bonded to each other. It may comprise 20 ring structures.

Examples of the monovalent organic group having 1 to 10 carbon atoms represented by R ⁸ and R ⁹ include the groups exemplified as the monovalent organic group having 1 to 20 carbon atoms represented by R ⁵ and R ^6. And an organic group having 1 to 10 carbon atoms.

Examples of the ring structure having 3 to 20 ring members formed together with the nitrogen atom to which R ⁸ and R ⁹ are bonded include, for example, an azacyclopropane structure, an azacyclobutane structure, an azacyclopentane structure (pyrrolidine structure), and an azacyclohexane structure (piperidine Monocyclic azacycloalkane structure such as azacycloheptane structure, azacyclooctane structure, and azacyclodecane structure;
Azabicyclo [2.2.1] heptane structure, azabicyclo [2.2.2] octane structure, azabicyclo [4.4.0] decane structure, azatricyclo [3.3.1.1 ^3,7 ] decane structure, etc. Polycyclic azacycloalkane structure;
Azaoxacycloalkane structures such as an azaoxacyclopropane structure, an azaoxacyclohexane structure (including a morpholine structure), and an azaoxacyclooctane structure;
Monocyclic azacycloalkene structures such as azacyclopropene structure, azacyclobutene structure, azacyclopentene structure, azacyclohexene structure, azacycloheptene structure, azacyclooctene structure, and azacyclodecene structure;
Examples include polycyclic azacycloalkene structures such as an azabicyclo [2.2.1] heptene structure, an azabicyclo [2.2.2] octene structure, and an azabicyclo [4.4.0] decene structure.

  The chain length of the group (L) is preferably an integer of 2 to 5 and more preferably an integer of 2 to 4 from the viewpoint of the polymerizability of the monomer giving the structural unit (I).

  Examples of the group containing a sulfur atom or a nitrogen atom between carbon and carbon of the alkylene chain include a group represented by the following formula (L).

In the above formula (L), X is a sulfur atom or - a divalent linking group containing a sulfur atom or a nitrogen atom linked to at least one - _{(CH 2) m} - and - _{(CH 2) n.} However, X does not include an alkylene chain. m and n are each independently an integer of 1 to 8. However, m and n satisfy 2 ≦ m + n ≦ 8.

  Examples of the divalent linking group containing a sulfur atom represented by X include -S-, a group exemplified as a group constituting a sulfur atom contained between carbon and carbon of the alkylene chain represented by L. Similar groups and the like can be mentioned.

Among them, from the viewpoint of more appropriately adjusting the interaction between the acid generated from the [B] acid generator in the resist film and the [A] polymer, and improving the lithography performance, -S-,- SO- and -SO ₂ - are preferred.

  Examples of the divalent linking group containing a nitrogen atom represented by X include the same groups as the groups exemplified as the group constituting the nitrogen atom contained between carbon and carbon of the alkylene chain represented by L Is mentioned.

Among them, from the viewpoint of more appropriately adjusting the interaction between the acid generated from the acid generator [B] in the resist film and the polymer [A] and improving the lithography performance, -NR ⁷ -and -N ⁺ R ⁸ R ⁹ - it is preferred.

  The above m and n are integers of 1 to 3 and preferably satisfy 2 ≦ m + n ≦ 4, more preferably 1 or 2 and more preferably satisfy 2 ≦ m + n ≦ 3.

  Examples of the structural unit (I) include structural units represented by the following formulas (A-1) to (A-36) (hereinafter, also referred to as “structural units (I-1) to (I-36)”) and the like. Is mentioned.

  As the structural unit (I), the structural units (I-1) to (I-12), (I-15) to (I-17), (I-20) to (I-23), and (I-25) ) To (I-32) and (I-34) to (I-36).

  [A1] The lower limit of the content of the structural unit (I) in the polymer is preferably 1 mol%, more preferably 3 mol%, and more preferably 8 mol%, based on all the structural units constituting the polymer [A1]. Is more preferable, and 20 mol% is particularly preferable. The upper limit of the content ratio of the structural unit (I) is preferably 90 mol%, more preferably 70 mol%, further preferably 50 mol%, and particularly preferably 40 mol%. [A2] The lower limit of the content of the structural unit (I) in the polymer is preferably 1 mol%, more preferably 5 mol%, and more preferably 10 mol%, based on all the structural units constituting the polymer [A2]. Is more preferable, and 50 mol% is particularly preferable. The upper limit of the content ratio of the structural unit (I) is preferably 95 mol%, more preferably 90 mol%, further preferably 85 mol%, and particularly preferably 80 mol%. [A] The lithography performance of the radiation-sensitive resin composition (I) can be improved by setting the content of the structural unit (I) of the polymer in the above range.

  [A1] The content ratio of the structural unit (I) of the polymer may be 100 mol% with respect to all the structural units constituting the polymer [A1]. [A1] By setting the content of the structural unit (I) of the polymer in the above range, the [A1] polymer can be made uniform, and the lithographic performance of the radiation-sensitive resin composition (I) can be improved. It can be further improved.

  Examples of the monomer providing the structural unit (I) include a compound represented by the following formula (i) (hereinafter, also referred to as “compound (i)”).

In the above formula (i), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and L have the same meanings as in the above formula (1).

The compound (i) is represented, for example, by the following formula (i ′) wherein R ³ is R ¹ , R ⁴ is R ² , R ⁶ is R ⁵ , and L is —CH ₂ C (CN) ₂ CH ₂ —. Compound (hereinafter, also referred to as “compound (i ′)”) can be synthesized simply and in good yield according to the following scheme.

In the above scheme, R ¹ , R ² , R ⁵ and L have the same meanings as in the above formula (1).

  By reacting the compound represented by the formula (i'-a) with the compound represented by the formula (i'-b) in a solvent such as tetrahydrofuran in the presence of a base such as calcium carbonate, The compound (i ') is produced. This product can be isolated by purification by washing with a solvent, column chromatography, recrystallization, distillation, or the like.

[Structural unit (II)]
The structural unit (II) contains an acid-dissociable group (however, excluding those corresponding to the structural unit (I)). Examples of the structural unit (II) include structural units represented by the following formulas (a-1) and (a-2) (hereinafter, also referred to as “structural units (II-1) and (II-2)”). preferable. In the following formulas (a-1) and (a-2), the groups represented by -CR ^A2 R ^A3 R ^A4 and -CR ^A6 R ^A7 R ^A8 are acid dissociable groups.

In the above formula (a-1), R ^A1 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. ^RA2 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R ^A3 and R ^A4 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or 3 to 20 ring members formed by combining these groups together with a carbon atom to which they are bonded. Represents a ring structure.
In the formula (a-2), ^RA5 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. ^RA6 is a hydrogen atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a monovalent oxyhydrocarbon group having 1 to 20 carbon atoms. ^RA7 and ^RA8 are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms or a monovalent oxyhydrocarbon group having 1 to 20 carbon atoms. L ^A is a single bond, -O -, - COO- or -CONH-.

  Here, the “number of ring members” refers to the number of atoms constituting a ring having an alicyclic structure and an aliphatic heterocyclic structure, and in the case of a polycyclic alicyclic structure and a polycyclic aliphatic heterocyclic structure, the number of atoms. Refers to the number of atoms constituting a ring.

Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by R ^A2 , R ^A3 , R ^A4 , R ^A6 , R ^A7, and R ^A8 include the monovalent hydrocarbon represented by R ^2. Examples of the group include the same groups as those exemplified above.

As R ^A2 , an alkyl group, a cycloalkyl group and an aryl group are more preferred, and a methyl group, an ethyl group, a propyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, an adamantyl group and a phenyl group are even more preferred.

Examples of the ring structure having 3 to 20 ring members in which the groups of R ^A3 and R ^A4 are combined with each other and formed together with the carbon atom to which they are bonded include, for example, cyclopropane structure, cyclobutane structure, cyclopentane structure, cyclohexane structure, cyclooctane Structure, cycloalkane structure such as cyclodecane structure;
Alicyclic unsaturated hydrocarbon structures such as cyclopentene structure and cyclopentadiene structure;
An alicyclic structure such as a polycyclic alicyclic hydrocarbon structure such as a norbornane structure, an adamantane structure, a tricyclodecane structure, or a tetracyclododecane structure;
Groups in which two of the hydrogen atoms of the carbon atoms forming the ring of these alicyclic structures are combined with each other to form an aromatic hydrocarbon group together with the carbon atoms to which they are bonded, and the like. .

As R ^A3 and R ^A4 , an alkyl group, a cycloalkane structure formed by combining these groups, a norbornane structure and an adamantane structure are preferable, and a methyl group, an ethyl group, a cyclopentane structure, a cyclohexane structure and an adamantane structure are preferable. More preferred.

Examples of the monovalent oxyhydrocarbon group having 1 to 20 carbon atoms represented by R ^A6 , R ^A7 and R ^A8 include, for example, one of 1 to 20 carbon atoms represented by R ^A2 , R ^A6 , R ^A7 and R ^A8. Examples of the monovalent hydrocarbon group include those having an oxygen atom between carbon and carbon.

As R ^A6 , R ^A7, and R ^A8 , a chain hydrocarbon group and an alicyclic hydrocarbon group containing an oxygen atom are preferable.

As the ^{L A,} a single bond and -COO- is more preferably a single bond.

As R ^A1 , a hydrogen atom and a methyl group are preferable, and a methyl group is more preferable, from the viewpoint of copolymerizability of a monomer giving the structural unit (II).
As R ^A5 , a hydrogen atom and a methyl group are preferable, and a hydrogen atom is more preferable, from the viewpoint of copolymerizability of a monomer giving the structural unit (II).

  As the structural unit (II), for example, structural units represented by the following formulas (a-1-a) to (a-1-d) and (a-2-a) (hereinafter, referred to as “structural unit (II-1) -A) to (II-1-d) or (II-2-a) ").

In the above formulas (a-1-a) to (a-1-d), R ^{A1 to} R ^A4 have the same meaning as in the above formula (a-1). n _a is an integer of 1 to 4. In the formula ^(a-2-a), R A5 ~R A8 is as defined in the above formula (a-2).

The n _a, preferably 1, 2 and 4, more preferably 1.

  Examples of the structural unit (II) include a structural unit represented by the following formula.

In the above formula, ^RA1 has the same ^{meaning as} in the above formula (a-1).

  Examples of the structural unit (II-2) include a structural unit represented by the following formula.

In the above formula, ^RA5 has the same ^{meaning as} in the above formula (a-2).

  As the structural unit (II), the structural units (II-1-b) and (II-1-d) are preferable.

  [A1] When the polymer has the structural unit (II), the lower limit of the content ratio of the structural unit (II) to all the structural units constituting the polymer [A1] is preferably 10 mol%, and 20 mol% is preferable. More preferably, 25 mol% is still more preferable, and 30 mol% is particularly preferable. On the other hand, the upper limit of the content ratio is preferably 80 mol%, more preferably 75 mol%, and still more preferably 70 mol%. [A2] The lower limit of the content of the structural unit (II) with respect to all the structural units constituting the polymer is preferably 5 mol%, more preferably 15 mol%, further preferably 20 mol%, and particularly preferably 25 mol%. preferable. On the other hand, the upper limit of the content ratio is preferably 95 mol%, more preferably 92 mol%, further preferably 86 mol%, and particularly preferably 80 mol%. [A] By dissolving the exposed and unexposed portions of the radiation-sensitive resin composition (I) in a developer by setting the content of the structural unit (II) to the above range with respect to all the structural units constituting the polymer. Contrast can be sufficiently ensured, and as a result, lithography performance can be further improved.

[Structural unit (III)]
The structural unit (III) is a structural unit containing a polar group (however, excluding those corresponding to the structural unit (I)). [A] The polymer has an appropriate polarity by further having the structural unit (III). As a result, the radiation-sensitive resin composition (I) can form a pattern having a more excellent rectangular shape in cross-sectional shape.

  Examples of the structural unit (III) include a structural unit represented by the following formula.

In the above formula, R ^L1 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ^y is a group containing a polar group. Examples of the group containing a polar group include the same groups as the groups containing a polar group exemplified for R ⁵ and R ⁶ .

The above ^RL1 is preferably a hydrogen atom or a methyl group, more preferably a methyl group, from the viewpoint of copolymerizability of a monomer giving the structural unit (III).

  Examples of the structural unit (III) include a structural unit containing a norbornane lactone structure, a structural unit containing an oxanorbornane lactone structure, a structural unit containing a γ-butyrolactone structure, a structural unit containing an ethylene carbonate structure, and a norbornane sultone structure. A structural unit containing a hydroxyadamantane structure and a structural unit containing a phenol group are preferable, and a structural unit derived from norbornanelactone-yl (meth) acrylate and a structural unit derived from oxanorbornanelactone-yl (meth) acrylate A structural unit derived from cyano-substituted norbornane lactone-yl (meth) acrylate, a structural unit derived from butyrolactone-3-yl (meth) acrylate, and a structural unit derived from ethylene carbonate-ylmethyl (meth) acrylate Structural units, norbornane sultone - yl (meth) structural units derived from structural units and vinyl phenol derived from structural units derived from acrylate are more preferred.

  [A] When the polymer has the structural unit (III), the lower limit of the content ratio of the structural unit (III) to all the structural units constituting the polymer [A] is preferably 1 mol%, and more preferably 10 mol%. More preferably, 20 mol% is further preferable, and 25 mol% is particularly preferable. On the other hand, the upper limit of the content ratio is preferably 75 mol%, more preferably 70 mol%, further preferably 65 mol%, and particularly preferably 60 mol%. When the content is in the above range, the adhesion of the resist pattern formed from the radiation-sensitive resin composition (I) to the substrate can be further improved. If the content is less than the lower limit, the adhesion of the resist pattern formed from the radiation-sensitive resin composition (I) to the substrate may be reduced. If the content exceeds the upper limit, the pattern-forming property of the radiation-sensitive resin composition (I) may be reduced.

[Structural unit (IV)]
The structural unit (IV) is a structural unit other than the structural unit (I) and includes a fluorine atom. [A] The polymer can have a fluorine atom content adjusted by further having the structural unit (IV) in addition to the structural unit (I). As a result, the radiation-sensitive resin composition (I) is obtained. The dynamic contact angle of the surface of the resist film formed from the film can be improved.

  As the structural unit (IV), a structural unit represented by the following formula (ff1) (hereinafter, also referred to as “structural unit (IVa)”) and a structural unit represented by the following formula (ff2) (hereinafter, “structure”) Unit (IVb) ”) and combinations thereof. The structural unit (IV) may have one or more structural units (IVa) and (IVb), respectively.

[Structural unit (IVa)]
The structural unit (IVa) is a structural unit represented by the following formula (ff1). [A] The polymer can adjust the fluorine atom content by having the structural unit (IVa).

In the above formula (ff1), R ^F1 is a hydrogen atom, a methyl group or a trifluoromethyl group. L ^F1 represents a single bond, an oxygen atom, a sulfur _{atom, -CO-O -, - SO} 2 -O-NH -, - is CO-NH- or -O-CO-NH-. R ^F2 is a monovalent fluorinated chain hydrocarbon group having 1 to 6 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 4 to 20 carbon atoms.

R ^F1 is preferably a hydrogen atom or a methyl group, and more preferably a methyl group, from the viewpoint of copolymerizability of a monomer giving the structural unit (IVa).

As the _{^{L F1, -CO-O -,}} - SO 2 -O-NH -, - CO-NH- and -O-CO-NH- are preferred, -CO-O-it is more preferred.

Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 6 carbon atoms represented by R ^F2 include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a perfluoroethyl group, 2,3,3,3-pentafluoropropyl group, 1,1,1,3,3,3-hexafluoropropyl group, perfluoro n-propyl group, perfluoro i-propyl group, perfluoro n-butyl group , A perfluoro i-butyl group, a perfluoro t-butyl group, a 2,2,3,3,4,4,5,5-octafluoropentyl group, a perfluorohexyl group and the like.

Examples of the monovalent fluorinated alicyclic hydrocarbon group having 4 to 20 carbon atoms represented by R ^F2 include a monofluorocyclopentyl group, a difluorocyclopentyl group, a perfluorocyclopentyl group, a monofluorocyclohexyl group, and a difluorocyclopentyl group. , Perfluorocyclohexylmethyl group, fluoronorbornyl group, fluoroadamantyl group, fluorobornyl group, fluoroisobornyl group, fluorotricyclodecyl group, fluorotetracyclodecyl group and the like.

Among the above, R ^F2 is preferably a fluorinated chain hydrocarbon group, such as a 2,2,2-trifluoroethyl group and a 1,1,1,3,3,3-hexafluoro-2-propyl group. Groups are more preferred.

  [A2] When the polymer contains the structural unit (IVa), the lower limit of the content ratio of the structural unit (IVa) to all the structural units constituting the polymer [A2] is more preferably 3 mol%, and more preferably 5 mol%. Mole% is more preferred. On the other hand, the upper limit of the content ratio is preferably 90 mol%, more preferably 70 mol%, and still more preferably 50 mol%. [A] The polymer can exhibit a higher dynamic contact angle on the resist film surface during immersion exposure by setting the content of the structural unit (IVa) in the above range.

[Structural unit (IVb)]
The structural unit (IVb) is a structural unit represented by the following formula (ff2). [A] By having the structural unit (IVb), the polymer can adjust the fluorine atom content and change the water repellency and hydrophilicity before and after alkali development.

In the above formula (ff2), R ^F3 is a hydrogen atom, a methyl group or a trifluoromethyl group. R ^F4 is a single bond, (u + 1) -valent hydrocarbon group or an oxygen atom at the terminal of ^{R F5} side of the hydrocarbon group having 1 to 20 carbon atoms, a sulfur ^{atom, -NR FF1} -, carbonyl group, -CO- It has a structure in which O- or -CO-NH- is bonded. R ^FF1 is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. R ^F5 is a single bond or a divalent organic group having 1 to 20 carbon atoms. ^LF2 is a single bond or a divalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms. L ^F3 represents an oxygen ^atom, -NR FF2 -, - it is a CO-O- ^{* f} or _-SO 2 -O- ^{* f.} R ^FF2 is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * ^F shows the site ^| part which couple ^| bonds with ^RF6 . ^RF6 is a hydrogen atom or a monovalent organic group having 1 to 30 carbon atoms. u is an integer of 1 to 3. However, when u is 1, R ^F4 may be a single bond. When u is 2 or 3, a plurality of R ^F5 , L ^F2 , L ^F3 and R ^F6 may be the same or different. When L ^F2 is a single bond, R ^F6 is a group containing a fluorine atom.

R ^F3 is preferably a hydrogen atom or a methyl group, and more preferably a methyl group, from the viewpoint of copolymerizability of the monomer giving the structural unit (IVb).

Examples of the (u + 1) -valent hydrocarbon group having 1 to 20 carbon atoms represented by R ^F4 include u hydrogen atoms from the monovalent hydrocarbon group exemplified as R ^A2 in the formula (a-1). And the like excluding.

  As u, 1 and 2 are preferable, and 1 is more preferable.

As the above R ^F4 , when u is 1, a single bond and a divalent hydrocarbon group are preferable, a single bond and an alkanediyl group are more preferable, and a single bond and an alkanediyl group having 1 to 4 carbon atoms are further preferable. A single bond, a methanediyl group and a propanediyl group are particularly preferred.

As the divalent organic group having 1 to 20 carbon atoms represented by R ^F5 , for example, one of the monovalent organic groups having 1 to 20 carbon atoms exemplified as R ^A2 in the formula (a-1) may be used. And the like, excluding the hydrogen atom.

R ^F5 is preferably a group having a single bond and a lactone structure, more preferably a group having a single bond and a polycyclic lactone structure, and more preferably a group having a single bond and a norbornane lactone structure.

The divalent chain fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by L ^F2, such as fluoro methane diyl group, difluoromethane diyl group, fluoro-ethanediyl group, difluoroethane diyl group, tetrafluoroethane diyl Fluorinated alkanediyl groups such as a group, hexafluoropropanediyl group, octafluorobutanediyl group;
And fluorinated alkenediyl groups such as a fluoroethenediyl group and a difluoroethenediyl group. Among these, a fluorinated alkanediyl group is preferred, and a difluoromethanediyl group is more preferred.

As the ^{L F3,} oxygen atom, preferably -CO-O- ^{* f} and ^{_{-SO 2 -O- * f, -CO-}} O- * f is more preferable.

The monovalent organic group represented by R ^22, for example, an acid-dissociable group, a hydrocarbon group or the like of an alkali dissociable group or a substituent 1 to 30 carbon atoms which may have a like.

  Examples of the structural unit (IVb) include structural units represented by the following formulas (ff2-1) to (ff2-3).

In the above formulas (ff2-1) to (ff2b-3), R ^{F4 ′} is a divalent linear, branched or cyclic, saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms. R ^F3 , L ^F2 , R ^F6 and u have the same meaning as in the above formula (ff2). When u is 2 or 3, a plurality of L ^F2 and R ^F6 may be the same or different.

  When the polymer [A2] contains the structural unit (IVb), the lower limit of the content ratio of the structural unit (IVb) to all the structural units constituting the polymer [A2] is preferably 5 mol%. The upper limit of the content ratio of the structural unit (IVb) is preferably 80 mol%, more preferably 60 mol%, and still more preferably 40 mol%. [A] By adjusting the content of the structural unit (IVb) in the polymer in the above range, the surface of the resist film formed from the radiation-sensitive resin composition (I) has a reduced dynamic contact angle in alkali development. Can be further improved.

[Other structural units]
[A] The polymer may have a structural unit other than the structural units (I) to (IV). Examples of the other structural unit include a structural unit containing a non-dissociable alicyclic hydrocarbon group. The upper limit of the content ratio of the other structural units is preferably 20 mol%, more preferably 10 mol%, based on all the structural units constituting the polymer [A].

  The radiation-sensitive resin composition (I) may contain one or more [A] polymers.

<[A] Method for synthesizing polymer>
[A] The polymer can be synthesized, for example, by polymerizing a monomer giving each structural unit in a suitable solvent using a radical polymerization initiator or the like.

Examples of the radical polymerization initiator include azobisisobutyronitrile (AIBN), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), and 2,2′-azobis (2-cyclopropyl) Azo radical initiators such as propionitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2′-azobisisobutyrate;
Peroxide-based radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide and the like can be mentioned.

  Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

Examples of the solvent used for the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane and n-decane;
Alicyclic hydrocarbons such as cyclohexane, cycloheptane, cyclooctane, decalin, norbornane;
Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene and cumene;
Halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene;
Saturated carboxylic esters such as ethyl acetate, n-butyl acetate, i-butyl acetate and methyl propionate;
Ketones such as acetone, methyl ethyl ketone, 4-methyl-2-pentanone and 2-heptanone;
Ethers such as tetrahydrofuran, dimethoxyethanes and diethoxyethanes;
Alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 4-methyl-2-pentanol and propylene glycol monomethyl ether;
Examples of the amide solvent include linear amides such as N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropionamide, and the like. And amides such as cyclic amides such as N-methylpyrrolidone and N, N'-dimethylimidazolidinone.

  Among these, ketones, alcohol solvents and ethers are preferred. The solvents used in these polymerizations may be used alone or in combination of two or more.

  The lower limit of the reaction temperature in the above polymerization is usually 40 ° C, preferably 50 ° C. The upper limit of the reaction temperature is usually 150 ° C, preferably 120 ° C. The lower limit of the reaction time is usually one hour. The upper limit of the reaction time is usually 48 hours, and preferably 24 hours.

  [A] The lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) of the polymer is preferably 1,000, more preferably 2,000, still more preferably 2,500, and 3,000. Is particularly preferred. The upper limit of Mw is preferably 50,000, more preferably 30,000, still more preferably 20,000, and particularly preferably 15,000. [A] When the Mw of the polymer is in the above range, the coating property and the development defect suppressing property of the radiation-sensitive resin composition (I) are improved. [A] If the Mw of the polymer is less than the lower limit, a resist film having sufficient heat resistance may not be obtained.

  [A] The lower limit of the ratio of Mw (Mw / Mn) to the number average molecular weight (Mn) in terms of polystyrene by GPC of the polymer is usually 1, and preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3 and more preferably 2.5.

The Mw and Mn of the polymer in the present specification are values measured using gel permeation chromatography (GPC) under the following conditions.
GPC column: 2 “G2000HXL”, 1 “G3000HXL”, 1 “G4000HXL” from Tosoh Column temperature: 40 ° C.
Elution solvent: tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass
Sample injection volume: 100 μL
Detector: Differential refractometer Standard substance: Monodisperse polystyrene

<[B] acid generator>
[B] The acid generator is a substance that generates an acid upon irradiation with radiation. The acid dissociable group of the polymer [A] is dissociated by the action of the acid to generate a polar group such as a carboxy group, and as a result, the etching rate of the polymer [A] changes. [B] The acid generator may be contained in any of the following compound forms (hereinafter referred to as "[B] acid generator" as appropriate) or in a form incorporated as a part of the polymer. Both forms may be used.

  [B] Examples of the acid generator include onium salt compounds, N-sulfonyloxyimide compounds, halogen-containing compounds, and diazoketone compounds.

  Examples of the onium salt compound include a sulfonium salt, an iodonium salt, a tetrahydrothiophenium salt, a phosphonium salt, a diazonium salt, a pyridinium salt and the like.

  [B] Specific examples of the acid generator include, for example, compounds described in paragraphs [0080] to [0113] of JP-A-2009-134088.

  [B] The acid generator preferably contains a compound represented by the following formula (b). [B] When the acid generator contains a compound having the following structure, the rectangularity of the cross-sectional shape of the pattern can be further improved.

In the above formula (b), R ^B1 is a monovalent group containing an alicyclic structure having 6 or more ring members or a monovalent group containing an aliphatic heterocyclic structure having 6 or more ring members. ^RB2 is a fluorinated alkanediyl group having 1 to 10 carbon atoms. X ⁺ is a monovalent radiation-sensitive onium cation.

Examples of the monovalent group such as cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, cyclodecyl group, cycloalkyl groups such as cyclododecyl containing ring members 6 or more alicyclic structure represented by R ^B1 ;
Cycloalkenyl groups such as cyclohexenyl group, cycloheptenyl group, cyclooctenyl group, cyclodecenyl group;
Polycyclic alicyclic saturated hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group;
And polycyclic alicyclic unsaturated hydrocarbon groups such as a norbornenyl group and a tricyclodecenyl group.

Examples of the monovalent group including ring members 6 or more aliphatic heterocyclic structure represented by R ^B1, for example, norbornane lactone - yl lactone structure-containing group such as a group;
A sultone structure-containing group such as a norbornane sultone-yl group;
An oxygen atom-containing heterocyclic structure-containing group such as an oxacycloheptyl group or an oxanorbornyl group;
A nitrogen-containing heterocyclic structure-containing group such as an azacyclohexyl group, an azacycloheptyl group or a diazabicyclooctane-yl group;
Examples thereof include a sulfur atom-containing heterocyclic structure-containing group such as a thiacycloheptyl group and a thianorbornyl group.

The lower limit of the number of ring members of the group represented by R ^B1 is preferably 8, more preferably 9, and still more preferably 10, from the viewpoint that the above-mentioned acid diffusion length becomes more appropriate. On the other hand, the upper limit of the number of ring members is preferably 15 and more preferably 13.

As R ^B1 , among these, a monovalent group containing an alicyclic structure having 9 or more ring members and a monovalent group containing an aliphatic heterocyclic structure having 6 or more ring members are preferable, and an adamantyl group and a hydroxyadamantyl group are preferred. Norbornane lactone-yl group, 5-oxo-4-oxatricyclo [4.3.1.1 ^3,8 ] undecane-yl group, adamantane-1-yloxycarbonyl group, norbornane sultone-2-yloxycarbonyl Groups and piperidin-1-ylsulfonyl groups are more preferred.

Fluorinated alkanediyl group having 1 to 10 carbon atoms represented by R ^B2, for example methylene bridge, ethanediyl group, one or more hydrogen atom of the alkanediyl group having 1 to 10 carbon atoms such as propane-diyl group With a fluorine atom.

Among these, SO ₃ ^- fluorinated alkane diyl group which has a fluorine atom to carbon atom is bonded to adjacent groups are preferred, SO ₃ ^- 2 fluorine atoms to the carbon atom adjacent to the group is attached Fluorinated alkanediyl groups are more preferred, 1,1-difluoromethanediyl group, 1,1-difluoroethanediyl group, 1,1,3,3,3-pentafluoro-1,2-propanediyl group, 1,1 , 2,2-tetrafluoroethanediyl, 1,1,2,2-tetrafluorobutanediyl, 1,1,2,2-tetrafluorohexanediyl, 1,1,2-trifluorobutanediyl And 1,1,2,2,3,3-hexafluoropropanediyl groups are more preferred.

The monovalent radiation-sensitive onium cation represented by X ⁺ is a cation that is decomposed by irradiation with exposure light. In the exposed portion, a sulfonic acid is generated from a proton generated by the decomposition of the radiation-sensitive onium cation and a sulfonate anion. Examples of the monovalent radiation-sensitive onium cation represented by X ⁺ include elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. And radiation-sensitive onium cations. Examples of the cation containing S (sulfur) as an element include a sulfonium cation and a tetrahydrothiophenium cation, and examples of the cation containing I (iodine) as an element include an iodonium cation. Among these, a sulfonium cation represented by the following formula (ba), a tetrahydrothiophenium cation represented by the following formula (bb) and an iodonium cation represented by the following formula (bc) preferable.

In the above formula (ba), R ^B3 , R ^B4 and R ^B5 each independently represent a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkyl group. aromatic hydrocarbon group having 6 to 12 carbon _atoms, a or a -OSO ^{2 -R BB1} or _-SO 2 ^{-R BB2,} or two or more are combined with each other configured ring of these groups . R ^BB1 and R ^BB2 each independently represent a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms. Or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. b1, b2 and b3 are each independently an integer of 0 to 5. R ^B3 to R ^B5 and, if a plurality ^{R BB1} and ^{R BB2} are each the plurality of ^R B3 ^{to R B5} and ^{R BB1} and ^{R BB2} may each be the same or different.

In the formula (bb), ^RB6 represents a substituted or unsubstituted linear or branched alkyl group having 1 to 8 carbon atoms or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms. It is. b4 is an integer of 0 to 7. If R ^B6 is plural, the plurality of R ^B6 may be the same or different, and plural R ^B6 may represent a constructed ring aligned with each other. R ^B7 is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. b5 is an integer of 0 to 6. If R ^B7 is plural, R ^B7 may be the same or different, and plural R ^B7 may represent a keyed configured ring structure. n _b is an integer of 0 to 3.

In the above formula ( ^bc ), R ^B8 and R ^B9 each independently represent a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted C 6 12 aromatic hydrocarbon _group, or an -OSO ^{2 -R BB3} or _-SO 2 ^{-R BB4,} or two or more are combined with each other configured ring of these groups. R ^BB3 and R ^BB4 each independently represent a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms. Or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. b6 and b7 are each independently an integer of 0 to 5. ^{R B8,} R B9, R ^BB3 and when ^{R BB4} is plural respective plurality of ^{R B8, R B9, R BB3} and ^{R BB4} may have respectively the same or different.

Examples of the unsubstituted linear alkyl group represented by R ^{B3 to} R ^B9 include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group.
Examples of the unsubstituted branched alkyl group represented by R ^{B3 to} R ^B9 include an i-propyl group, an i-butyl group, a sec-butyl group, and a t-butyl group.
As the ^R B3 ^{to R B5,} unsubstituted aromatic hydrocarbon groups represented by ^{R B8} and ^{R B9,} for example, a phenyl group, a tolyl group, a xylyl group, mesityl group, an aryl group such as phenyl or naphthyl;
And aralkyl groups such as benzyl group and phenethyl group.
Examples of the unsubstituted aromatic hydrocarbon group represented by ^RB6 and ^RB7 include a phenyl group, a tolyl group, and a benzyl group.

  Examples of the substituent which may substitute a hydrogen atom of the alkyl group and the aromatic hydrocarbon group include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, a hydroxy group, a carboxy group, and a cyano group. Nitro group, alkoxy group, alkoxycarbonyl group, alkoxycarbonyloxy group, acyl group, acyloxy group and the like. Of these, a halogen atom is preferred, and a fluorine atom is more preferred.

Examples of the ^R B3 ^{to R B9,} unsubstituted, straight or branched alkyl group, a fluorinated alkyl group, an unsubstituted monovalent aromatic hydrocarbon group and -OSO ₂ -R ^BB5, -SO ₂ - R ^BB5 is preferred, a fluorinated alkyl group and an unsubstituted monovalent aromatic hydrocarbon group are more preferred, and a fluorinated alkyl group is even more preferred. R ^BB5 is an unsubstituted monovalent alicyclic hydrocarbon group or an unsubstituted monovalent aromatic hydrocarbon group.

In the above formula (ba), b1, b2 and b3 are preferably integers of 0 to 2, more preferably 0 and 1, and still more preferably 0.
B4 in the above formula (bb) is preferably an integer of 0 to 2, more preferably 0 and 1, and still more preferably 1. b5 is preferably an integer of 0 to 2, more preferably 0 and 1, and even more preferably 0. The n _b, is preferably an integer of 1 to 3, more preferably 2 and 3, 2 is more preferable.
In the above formula (bc), b6 and b7 are preferably integers of 0 to 2, more preferably 0 and 1, and still more preferably 0.

X ⁺ is preferably a cation represented by the above formula (ba), and more preferably a triphenylsulfonium cation.

  Examples of the acid generator represented by the formula (b) include compounds represented by the following formulas (b-1) to (b-16) (hereinafter, referred to as “compounds (b-1) to (b-16) ))).

  [B] As the acid generator, among these, an onium salt compound is preferable, a sulfonium salt and a tetrahydrothiophenium salt are more preferable, and the compound (b-1), the compound (b-12), and the compound (b-13) ) And compound (b-14) are more preferred.

  When the acid generator [B] is the acid generator [B], the content of the acid generator [B] relative to 100 parts by mass of the polymer [A] is from the viewpoint of improving the pattern shape of the formed pre-pattern. The lower limit of the amount is preferably 0.1 part by mass, more preferably 0.5 part by mass, still more preferably 1 part by mass, and particularly preferably 3 parts by mass. On the other hand, the upper limit of the content of the acid generator [B] is preferably 40 parts by mass, more preferably 35 parts by mass, still more preferably 30 parts by mass, and particularly preferably 25 parts by mass. [B] By setting the content of the acid generator in the above range, the rectangularity of the pre-pattern is improved. [B] One or more acid generators can be used.

<[C] solvent>
The radiation-sensitive resin composition (I) contains a solvent [C]. [C] Solvent dissolves or disperses [A] polymer and [B] acid generator, and [D] acid diffusion controller, [E] polymer and other optional components contained as necessary. There is no particular limitation as long as it is possible. [C] Solvents include, for example, alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, hydride solvents and the like.

Examples of the alcohol-based solvent include aliphatic monoalcohol-based solvents having 1 to 18 carbon atoms, such as 4-methyl-2-pentanol and n-hexanol;
An alicyclic monoalcohol solvent having 3 to 18 carbon atoms such as cyclohexanol;
A polyhydric alcohol solvent having 3 to 18 carbon atoms such as 1,2-propylene glycol;
Examples thereof include polyhydric alcohol partial ether solvents having 3 to 19 carbon atoms such as propylene glycol monoethyl ether.

Examples of the ether solvent include dialiphatic ether solvents such as diethyl ether, dipropyl ether and dibutyl ether;
Aromatic ring ether solvents such as anisole and diphenyl ether;
And cyclic ether solvents such as tetrahydrofuran and dioxane.

Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, diethyl ketone, methyl-iso-butyl ketone, methyl-n-amyl ketone, ethyl-n-butyl ketone, methyl-n-hexyl Chain ketone solvents such as ketone, di-iso-butyl ketone, trimethylnonanone, acetophenone;
Alcohol solvents and ketone solvents such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone;
Diketone solvents such as 2,4-pentanedione and acetonylacetone are exemplified.

Examples of the amide solvent include linear amides such as N-methylformamide, N, N-dimethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropionamide, and the like. System solvent;
And cyclic amide solvents such as N-methylpyrrolidone and N, N'-dimethylimidazolidinone.

Examples of the ester solvent include monocarboxylic acid ester solvents such as n-butyl acetate and ethyl lactate;
lactone solvents such as γ-butyrolactone and valerolactone;
Polyhydric alcohol partial ether carboxylate solvents such as propylene glycol monomethyl ether acetate;
Polyvalent carboxylic acid diester solvents such as diethyl oxalate;
Examples thereof include carbonate solvents such as dimethyl carbonate and diethyl carbonate.

  Of these, alcohol solvents and ketone solvents are preferred, and polyhydric alcohol partial ether carboxylate solvents and cyclic ketone solvents are more preferred. [C] The solvent can be used alone or in combination of two or more.

<[D] Acid diffusion controller>
The radiation-sensitive resin composition (I) may optionally contain [D] an acid diffusion controller. The [D] acid diffusion controller has an effect of controlling the diffusion phenomenon of the acid generated from the [B] acid generator by exposure in the resist film, and suppressing an undesired chemical reaction in the non-exposed region. As a result, the storage stability of the obtained radiation-sensitive resin composition (I) is further improved. In addition, the resolution as a resist is further improved, and a line width change of a resist pattern due to a change in a laying time from exposure to development processing can be suppressed, so that a radiation-sensitive resin composition (I ) Is obtained. [D] As the content form of the acid diffusion controller in the radiation-sensitive resin composition (I), a form of an acid diffusion controller which is a low molecular compound as described below (hereinafter, also referred to as “acid diffusion controller” as appropriate) ) Or acid diffusion controlling groups incorporated as part of the polymer, or both.

  Examples of the acid diffusion controller [D] include compounds represented by the following formula (c-1) (hereinafter, also referred to as “nitrogen-containing compound (I)”) and compounds having two nitrogen atoms in the same molecule (Hereinafter also referred to as “nitrogen-containing compound (II)”), a compound having three nitrogen atoms (hereinafter also referred to as “nitrogen-containing compound (III)”), an amide group-containing compound, a urea compound, and a nitrogen-containing heterocyclic compound And the like.

In the above formula (c-1), R ^C1 , R ^C2 and R ^C3 are each independently a hydrogen atom, a linear, branched or cyclic alkyl group, aryl group or aralkyl group which may be substituted. It is.

  Examples of the nitrogen-containing compound (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline. Can be

  Examples of the nitrogen-containing compound (II) include ethylenediamine, N, N, N ', N'-tetramethylethylenediamine, and the like.

  Examples of the nitrogen-containing compound (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

  Examples of the amide group-containing compound include formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone. Can be

  Examples of the urea compound include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

  Examples of the nitrogen-containing heterocyclic compound include pyridines such as pyridine and 2-methylpyridine, pyrazine, pyrazole and the like.

  Further, as the acid diffusion controller, a compound having an acid dissociable group can be used. Examples of the acid diffusion controller having such an acid dissociable group include N- (t-butoxycarbonyl) piperidine, N- (t-butoxycarbonyl) imidazole, N- (t-butoxycarbonyl) benzimidazole, and N- (t-butoxycarbonyl) benzimidazole. (T-butoxycarbonyl) -2-phenylbenzimidazole, N- (t-butoxycarbonyl) di-n-octylamine, N- (t-butoxycarbonyl) diethanolamine, N- (t-butoxycarbonyl) dicyclohexylamine, N -(T-butoxycarbonyl) diphenylamine, N- (t-butoxycarbonyl) -4-hydroxypiperidine and the like.

  Further, as the acid diffusion controller, a photo-degradable base that is exposed to light to generate a weak acid can be used. Examples of the photodisintegrable base include an onium salt compound which decomposes upon exposure to light and loses the acid diffusion controllability. Examples of the onium salt compound include a sulfonium salt compound represented by the following formula (c-2) and an iodonium salt compound represented by the following formula (c-3).

In the formulas (c-2) and (c-3), R ^{C4 to} R ^C8 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a hydroxy group, or a halogen atom. E ⁻ and Q ⁻ are each independently an OH ⁻ , R ^CC1 —COO ⁻ , R ^CC1 —SO ₃ ^— or an anion represented by the following formula (c-4). Here, R ^CC1 is an alkyl group, an aryl group or an aralkyl group.

In the above formula (c-4), R ^C9 represents a linear or branched alkyl group having 1 to 12 carbon atoms, in which some or all of the hydrogen atoms may be substituted with a fluorine atom, or a carbon atom having 1 to 12 carbon atoms. 12 straight-chain or branched alkoxyl groups. n _c is an integer of 0-2. If n _c is 2, it may be different in each of the plurality of R ^C9 same.

  When the radiation-sensitive resin composition (I) contains the [D] acid diffusion controller, the lower limit of the content of the [D] acid diffusion controller relative to 100 parts by mass of the polymer [A] is 0.1 mass. Parts by mass, more preferably 0.3 parts by mass. On the other hand, the upper limit of the content is preferably 10 parts by mass, more preferably 8 parts by mass, and still more preferably 5 parts by mass.

<[E] polymer>
The polymer [E] is a fluorine atom-containing polymer other than the polymer [A], is a polymer having a larger fluorine atom content than the polymer [A], and is a water-repellent polymer additive. When the radiation-sensitive composition contains the [E] polymer, and the resist film is formed, the distribution of the [E] polymer in the film near the surface of the resist film due to the oil repellency characteristics of the [E] polymer in the film. It tends to be unevenly distributed, and can suppress elution of an acid generator, an acid diffusion controller, and the like during immersion exposure to the immersion medium. Further, due to the water-repellent characteristics of the polymer [E], the advancing contact angle between the resist film and the immersion medium can be controlled within a desired range, and the occurrence of bubble defects can be suppressed. Further, the receding contact angle between the resist film and the immersion medium is increased, and high-speed scanning exposure can be performed without leaving water droplets. When the radiation-sensitive resin composition (I) contains the polymer [E], a resist film suitable for the liquid immersion exposure method can be formed.

When the radiation-sensitive resin composition (I) has the polymer [E], the lower limit of the fluorine atom content of the polymer [E] is preferably 1% by mass, more preferably 2% by mass, and 3% by mass. Is more preferable, and 5% by mass is particularly preferable. On the other hand, the upper limit of the content is preferably 60% by mass, more preferably 40% by mass, and still more preferably 30% by mass. [E] If the fluorine atom content of the polymer is less than the above lower limit, the hydrophobicity of the resist film surface may decrease. The fluorine atom content (% by mass) of the polymer can be calculated from the structure of the polymer obtained by measuring the ¹³ C-NMR spectrum.

  [E] The form of the fluorine atom contained in the polymer is not particularly limited, and may be any of a main chain, a side chain and a terminal, but preferably has a structural unit containing a fluorine atom.

  [E1] The polymer preferably has a structural unit (IVa), a structural unit (IVb) and a combination thereof in the polymer [A] as a structural unit containing a fluorine atom. [E1] The polymer may have one or more structural units (IVa) and two or more structural units (IVb), respectively.

  The lower limit of the content ratio of the structural unit (IVa) and the structural unit (IVb) is preferably 10 mol%, more preferably 15 mol%, and more preferably 20 mol%, based on all the structural units constituting the polymer [E]. % Is more preferred. On the other hand, the upper limit of the content ratio is preferably 90 mol%, more preferably 85 mol%, and still more preferably 80 mol%.

  Further, the polymer [E] preferably has a structural unit containing an acid-dissociable group. Examples of the structural unit containing an acid dissociable group include the structural unit (II) in the polymer [A].

  When the radiation-sensitive resin composition (I) contains the polymer [E], the lower limit of the content of the polymer [E] to 100 parts by mass of the polymer [A] is preferably 0.1 part by mass, 0.2 parts by mass is more preferable, 0.5 parts by mass is more preferable, and 1 part by mass is particularly preferable. On the other hand, the upper limit of the content is preferably 30 parts by mass, more preferably 20 parts by mass, still more preferably 15 parts by mass, and particularly preferably 10 parts by mass.

  The polymer [E] can be synthesized in the same manner as the polymer [A] described above.

  [E] The weight average molecular weight (Mw) of the polymer in terms of polystyrene measured by gel permeation chromatography (GPC) is not particularly limited, but the lower limit is preferably 1,000, more preferably 2,000, and 2,500. Is more preferable, and 3,000 is particularly preferable. On the other hand, the upper limit of the weight average molecular weight is preferably 50,000, more preferably 30,000, still more preferably 20,000, and particularly preferably 15,000. [E] When the Mw of the polymer is in the above range, the coating property and the development defect suppressing property of the radiation-sensitive resin composition (I) are improved. [E] When the Mw of the polymer is less than the above lower limit, a resist film having sufficient heat resistance may not be obtained. [E] When the Mw of the polymer exceeds the above upper limit, the developability of the resist film may decrease.

  [E] The lower limit of the ratio (Mw / Mn) of Mw to the number average molecular weight (Mn) in terms of polystyrene by GPC of the polymer is preferably 1. On the other hand, the upper limit of the ratio is preferably 5, more preferably 3, and still more preferably 2.

  The lower limit of the content of the polymer [E] in the radiation-sensitive resin composition (I) is such that the distribution of the polymer [A2] to the surface layer of the resist film is promoted and the radiation-sensitive resin composition (I) From the viewpoint of improving the lithography performance, the amount is preferably 500 parts by mass, more preferably 700 parts by mass, and still more preferably 1,000 parts by mass with respect to 100 parts by mass of the polymer [A2]. On the other hand, the upper limit of the content is preferably 100,000 parts by mass, more preferably 20,000 parts by mass, and still more preferably 10,000 parts by mass. The radiation-sensitive resin composition (I) may contain one or more [F] polymers.

<[F] polymer>
The polymer [F] is a polymer having a smaller fluorine atom content than the polymer [A] and having a structural unit containing an acid-dissociable group. For example, when the polymer [A] is used as a water-repellent polymer additive ([A2] polymer), the radiation-sensitive resin composition (I) contains a polymer [F] as a base polymer. Is preferred. As the polymer [F], those having the structural unit (II) and the structural unit (III) in the polymer [A] are preferable, and may have other structural units.

  The lower limit of the content of the structural unit (II) is preferably 10 mol%, more preferably 20 mol%, based on all structural units constituting the polymer [F]. As a maximum of the above-mentioned content rate, 70 mol% is preferred and 60 mol% is more preferred.

  The lower limit of the content of the structural unit (III) is preferably 10 mol%, more preferably 20 mol%, based on all the structural units constituting the [F] polymer. As a maximum of the above-mentioned content rate, 70 mol% is preferred and 60 mol% is more preferred.

  When the polymer [F] contains other structural units, the lower limit of the other structural units is preferably 10 mol% with respect to all the structural units constituting the polymer [F]. As a maximum of the above-mentioned content rate, 40 mol% is preferred and 30 mol% is more preferred.

  [F] The lower limit of the Mw of the polymer is preferably 1,000, more preferably 2,000, still more preferably 3,000, and particularly preferably 5,000. On the other hand, the upper limit of the Mw of the polymer [F] is preferably 50,000, more preferably 30,000, still more preferably 20,000, and particularly preferably 15,000.

  [F] The lower limit of Mw / Mn of the polymer is usually 1. On the other hand, the upper limit of Mw / Mn is usually 5, preferably 3 and more preferably 2.

  As the lower limit of the content of the polymer [F] in the radiation-sensitive resin composition (I), the uneven distribution of the polymer [A2] to the surface layer of the resist film is promoted, and the content of the radiation-sensitive resin composition (I) is reduced. From the viewpoint of improving the lithography performance, the amount is preferably 500 parts by mass, more preferably 700 parts by mass, and still more preferably 1,000 parts by mass with respect to 100 parts by mass of the polymer [A2]. On the other hand, the upper limit of the content is preferably 100,000 parts by mass, more preferably 20,000 parts by mass, and still more preferably 10,000 parts by mass. The radiation-sensitive resin composition (I) may contain one or more [F] polymers.

<[G] uneven distribution accelerator>
The radiation-sensitive resin composition (I) may optionally contain [G] a localization promoting agent. [G] The uneven distribution accelerator is more effective when the radiation-sensitive resin composition (I) contains a water-repellent polymer additive such as [E] a polymer. This has the effect of causing segregation on the resist film surface. By adding the uneven distribution accelerator to the radiation-sensitive resin composition (I), the amount of the water-repellent polymer additive to be added can be made smaller than before. Therefore, it is possible to further suppress the elution of components from the resist film into the immersion liquid without deteriorating the lithography performance, and it is possible to perform immersion exposure at a higher speed by high-speed scanning. The hydrophobicity of the resist film surface that suppresses immersion-derived defects can be improved. Examples of such a localization accelerator that can be used include low molecular weight compounds having a relative dielectric constant of 30 or more and 200 or less and a boiling point at 1 atm of 100 ° C. or more. Specific examples of such a compound include a lactone compound, a carbonate compound, a nitrile compound, and a polyhydric alcohol.

  Examples of the lactone compound include γ-butyrolactone, valerolactone, mevalonic lactone, norbornane lactone, and the like.

  Examples of the carbonate compound include propylene carbonate, ethylene carbonate, butylene carbonate, and vinylene carbonate.

  Examples of the nitrile compound include succinonitrile.

  Examples of the polyhydric alcohol include glycerin.

  When the radiation-sensitive resin composition (I) contains the [G] uneven distribution accelerator, the lower limit of the content of the [G] uneven distribution accelerator is determined by the polymer of the radiation-sensitive resin composition (I). 10 parts by mass, preferably 15 parts by mass, more preferably 20 parts by mass, and particularly preferably 25 parts by mass with respect to 100 parts by mass in total. The upper limit of the content is preferably 500 parts by mass, more preferably 300 parts by mass, further preferably 200 parts by mass, and particularly preferably 100 parts by mass.

<Other optional ingredients>
The radiation-sensitive resin composition (I) may contain other optional components in addition to the components [A] to [G]. Examples of the other optional components include a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. One or more of these other optional components may be used in combination.

(Surfactant)
Surfactants have the effect of improving coatability, striation, developability, and the like. Examples of the surfactant include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene n-octylphenyl ether, polyoxyethylene n-nonylphenyl ether, polyethylene glycol dilaurate, and polyethylene glycol dilaurate. Nonionic surfactants such as stearate; commercially available products include KP341 (Shin-Etsu Chemical Co., Ltd.) and Polyflow No. 75; 95 (Kyoeisha Chemical), F-Top EF301, EF303, EF352 (Tokim Products), Megafac F171, F173 (DIC, DIC), Florard FC430, FC431 (Sumitomo 3M) Asahi Guard AG710, Surflon S-382, SC-101, SC-102, SC-103, SC-104, SC-105, SC-106 (above, Asahi Glass Industry Co., Ltd.) No. The upper limit of the surfactant content in the radiation-sensitive resin composition (I) is usually 2 parts by mass based on 100 parts by mass of the polymer [A].

(Alicyclic skeleton-containing compound)
The alicyclic skeleton-containing compound has an effect of improving dry etching resistance, pattern shape, adhesion to a substrate, and the like.

Examples of the alicyclic skeleton-containing compound include adamantane derivatives such as 1-adamantane carboxylic acid, 2-adamantanone, and t-butyl 1-adamantane carboxylate;
Deoxycholate esters such as t-butyl deoxycholate, t-butoxycarbonylmethyl deoxycholate, 2-ethoxyethyl deoxycholate;
Lithocholic acid esters such as t-butyl lithocholic acid, t-butoxycarbonylmethyl lithocholic acid, 2-ethoxyethyl lithocholic acid;
3- [2-hydroxy-2,2-bis (trifluoromethyl) ethyl] tetracyclo [4.4.0.1 ^2,5 . 17, ¹⁰ ] dodecane, 2-hydroxy-9-methoxycarbonyl-5-oxo-4-oxa-tricyclo [4.2.1.0 ^3,7 ] nonane and the like. The upper limit of the content of the alicyclic skeleton-containing compound in the radiation-sensitive resin composition (I) is usually 5 parts by mass based on 100 parts by mass of the polymer [A].

(Sensitizer)
The sensitizer has the effect of increasing the amount of acid generated from the acid generator [B], and has the effect of improving the "apparent sensitivity" of the radiation-sensitive resin composition (I).

  Examples of the sensitizer include carbazoles, acetophenones, benzophenones, naphthalenes, phenols, biacetyl, eosin, rose bengal, pyrenes, anthracenes, phenothiazines, and the like. These sensitizers may be used alone or in combination of two or more. The upper limit of the content of the sensitizer in the radiation-sensitive resin composition (I) is usually 2 parts by mass based on 100 parts by mass of the polymer [A].

<Method of preparing radiation-sensitive resin composition (I)>
The radiation-sensitive resin composition (I) comprises, for example, a polymer [A], an acid generator [B], a solvent [C], optional components contained as needed, and an acid diffusion controller [D]. It can be prepared by mixing in proportions. In this case, it is preferable that, after mixing the above components, the mixture be filtered through a filter having a pore size of about 0.2 μm, for example. The lower limit of the solid concentration of the radiation-sensitive resin composition (I) is preferably 0.1% by mass, more preferably 0.5% by mass, still more preferably 1% by mass, and particularly preferably 1.5% by mass. . The upper limit of the solid content concentration is preferably 50% by mass, more preferably 30% by mass, further preferably 20% by mass, and particularly preferably 10% by mass.

<Method of forming resist pattern>
A method for forming a resist pattern according to another embodiment of the present invention includes a step of forming a resist film (hereinafter, also referred to as a “resist film forming step”) and a step of exposing the resist film (hereinafter, also referred to as an “exposure step”). And a step of developing the exposed resist film (hereinafter, also referred to as a “development step”). The resist film is formed from the radiation-sensitive resin composition (I) described above.

  According to the method for forming a resist pattern, since the above-mentioned radiation-sensitive resin composition (I) is used, it exhibits excellent depth of focus and MEEF performance, has a small LWR, has few defects, and has a low cross-sectional shape. It is possible to form a resist pattern excellent in rectangularity and film shrinkage suppression. Hereinafter, each step of the resist pattern forming method will be described.

[Resist film forming step]
In this step, a resist film is formed from the radiation-sensitive resin composition (I). Examples of the substrate on which the resist film is formed include conventionally known substrates such as a silicon wafer, silicon dioxide, and a wafer coated with aluminum. Further, an organic or inorganic antireflection film disclosed in, for example, Japanese Patent Publication No. 6-12452 or JP-A-59-93448 may be formed on a substrate. Examples of the coating method include spin coating (spin coating), cast coating, and roll coating. After the application, if necessary, a pre-bake (PB) may be performed to volatilize the solvent in the coating film. The lower limit of the PB temperature is usually 60 ° C, preferably 80 ° C. On the other hand, the upper limit of the PB temperature is usually 140 ° C., preferably 120 ° C. The lower limit of the PB time is usually 5 seconds, preferably 10 seconds. On the other hand, the lower limit of the PB time is usually 600 seconds, and preferably 300 seconds. The lower limit of the average thickness of the formed resist film is preferably 10 nm. The upper limit of the average thickness is preferably 1,000 nm, and more preferably 500 nm.

[Exposure process]
In this step, the resist film formed in the resist film forming step is irradiated with radiation through a photomask or the like (in some cases, through an immersion medium such as water) to be exposed. Examples of the radiation include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and γ-rays; and charged particle beams such as electron beams and α-rays, depending on the line width of a target pattern. Is mentioned. Among these, far ultraviolet rays, EUV and electron beams are preferable, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV and electron beam are more preferable, and ArF excimer laser light, EUV and electron beam are preferable. More preferred.

  When the exposure is performed by immersion exposure, examples of the immersion liquid used include water and a fluorine-based inert liquid. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has a temperature coefficient of refractive index as small as possible so as to minimize distortion of the optical image projected on the film. In the case of excimer laser light (wavelength: 193 nm), it is preferable to use water from the viewpoint of easy availability and easy handling in addition to the above-described viewpoints. When water is used, an additive that decreases the surface tension of water and increases the surface activity may be added in a small ratio. The additive is preferably one that does not dissolve the resist film on the wafer and has negligible effect on the optical coat on the lower surface of the lens. Distilled water is preferred as the water used.

  After the above exposure, post-exposure bake (PEB) is performed to dissociate the acid dissociable groups of the [A] polymer and the like by the acid generated from the [B] acid generator by the exposure in the exposed portions of the resist film. Is preferably promoted. Due to this PEB, a difference is caused between the exposed part and the unexposed part due to solubility in a developing solution. The lower limit of the PEB temperature is usually 50 ° C., preferably 80 ° C. On the other hand, the upper limit of the PEB temperature is usually 180 ° C., preferably 130 ° C. The lower limit of the PEB time is usually 5 seconds, preferably 10 seconds. On the other hand, the upper limit of the PEB time is usually 600 seconds, and preferably 300 seconds.

[Development step]
In this step, the resist film exposed in the above exposure step is developed. Thereby, a predetermined resist pattern can be formed. After development, it is common to wash with water or a rinse solution such as alcohol and dry. As a developing method in the developing step, alkali developing or organic solvent developing may be used.

  Examples of the developer used for the development include, in the case of alkali development, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n -Propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo- [5.4.0] -7-undecene, An alkaline aqueous solution in which at least one kind of an alkaline compound such as 1,5-diazabicyclo- [4.3.0] -5-nonene is dissolved is exemplified. Among these, a TMAH aqueous solution is preferable, and a 2.38% by mass TMAH aqueous solution is more preferable.

  In the case of organic solvent development, examples thereof include organic solvents such as hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, or solvents containing organic solvents. Examples of the organic solvent include one or more of the solvents listed as the solvent [B] in the radiation-sensitive resin composition (I). Of these, ester solvents and ketone solvents are preferred. As the ester solvent, an acetate solvent is preferable, and n-butyl acetate is more preferable. As the ketone solvent, a chain ketone is preferable, and 2-heptanone is more preferable. The lower limit of the content of the organic solvent in the developer is preferably 80% by mass, more preferably 90% by mass, further preferably 95% by mass, and particularly preferably 99% by mass. Components other than the organic solvent in the developer include, for example, water, silicone oil, and the like.

  As a developing method, for example, a method in which a substrate is immersed in a bath filled with a developing solution for a certain period of time (dip method), a method in which the developing solution is raised on the substrate surface by surface tension and is stopped for a certain period of time (paddle method) ), A method of spraying a developer onto the substrate surface (spray method), a method of continuously applying a developer while scanning a developer application nozzle at a constant speed on a substrate rotating at a constant speed (dynamic dispense method). And the like.

  A method for forming a resist pattern according to another embodiment of the present invention includes a step of forming a resist film), a step of exposing the resist film, and a developing solution containing the exposed resist film as a main component in an organic solvent. And a step of developing. The resist film is formed from the radiation-sensitive resin composition (II).

  According to the method for forming a resist pattern, since the radiation-sensitive resin composition (II) is used, it exhibits excellent depth of focus and MEEF performance, has a small LWR, has few defects, and has a rectangular shape in cross-sectional shape. In addition, a resist pattern having excellent film shrinkage suppression properties can be formed. Hereinafter, each step of the resist pattern forming method will be described.

  The step of forming a resist film and the step of exposing the resist film are the same as the resist film forming step and the exposing step, respectively. Hereinafter, the step of developing the exposed resist film with a developer mainly containing an organic solvent will be described.

[Step of developing the exposed resist film with a developer mainly containing an organic solvent]
In this step, the resist film exposed in the step of exposing the resist film is developed with a developer containing an organic solvent as a main component. Thereby, a predetermined resist pattern can be formed. After development, it is common to wash with water or a rinse solution such as alcohol and dry. The developer preferably has, for example, an organic solvent content of 50% by mass or more.

  As the organic solvent, the same solvents as those exemplified in the above exposure step can be used. Preferred ones and the content of the organic solvent in the developing solution are the same as those in the developing step. Regarding the developing method, the same method as the method exemplified in the above-mentioned developing step can be employed.

<Radiation-sensitive resin composition (II)>
The radiation-sensitive resin composition (II) contains a polymer [A ′], a radiation-sensitive acid generator, and a solvent. The radiation-sensitive resin composition (II) may contain [D] an acid diffusion controller, [E] polymer, [F] polymer and [G] uneven distribution accelerator as suitable components. Other optional components may be contained as long as the effects of the present invention are not impaired.

  The radiation-sensitive resin composition (II) may contain only a base polymer as a polymer component, or may contain a water-repellent polymer additive in addition to the base polymer. By containing the water-repellent polymer additive, the radiation-sensitive resin composition (II) can suppress elution of the acid generator and the like from the resist film, and the formed resist film surface has a high dynamic contact angle. As a result, the surface of the resist film can exhibit excellent drainage characteristics. Accordingly, in the immersion exposure process, high-speed scan exposure can be performed without having to separately form an upper layer film for shielding the resist film surface from the immersion medium.

  When the radiation-sensitive resin composition (II) contains a water-repellent polymer additive, the same water-repellent polymer additive as that described as the component of the radiation-sensitive resin composition (I) is used. The content of the water-repellent polymer additive and the mode of the polymer component in the radiation-sensitive resin composition (II) can be used in the same manner as in the radiation-sensitive resin composition (I).

  Radiation-sensitive acid generator, solvent, [D] acid diffusion controller, [E] polymer, [F] polymer, [G] uneven distribution accelerator of radiation-sensitive resin composition (II) and other optional components As the components, those similar to those described as the respective components of the radiation-sensitive resin composition (I) can be used. The preferred components and the content ratio of each component are the same as those of the radiation-sensitive resin composition (I). Hereinafter, the polymer [A '] will be described.

<[A ′] polymer>
[A ′] The polymer is a polymer having a structural unit (I ′). The radiation-sensitive resin composition (II) is characterized in that the polymer [A '] has the structural unit (I'), and thus has LWR performance, resolution, rectangular cross-sectional shape, depth of focus, MEEF performance, and development defects. It is possible to form a resist pattern which is excellent in suppressing properties and film shrinking suppressing properties. The reason why the radiation-sensitive resin composition (II) has the above-described structure to achieve the above-described effects is not necessarily clear, but can be inferred, for example, as follows. That is, the [A '] polymer has a cyclic skeleton containing an alkylene chain of L (hereinafter, also referred to as "group (L')"), so that the main chain becomes highly rigid. As a result, the [A ′] polymer can appropriately reduce the diffusion length of the acid generated from the radiation-sensitive acid generator, and the [A ′] polymer can be developed using an organic solvent as a main component. When developing with a liquid, film shrinkage due to a change in volume or the like can be suppressed. Therefore, it is considered that the lithography performance of the radiation-sensitive resin composition (II) can be improved.

  The polymer [A] (hereinafter also referred to as “[A1 ′] polymer)” as a base polymer in the radiation-sensitive resin composition (II) includes, in addition to the structural unit (I ′), an acid-labile group. And a structural unit (III) containing a polar group, and may have a structural unit other than the above structural units (I ′) to (III).

  [A ′] polymer (hereinafter also referred to as “[A2 ′] polymer”) as a water-repellent polymer additive in the radiation-sensitive resin composition (I) includes, in addition to the structural unit (I ′), It is preferable to have a structural unit (II) containing an acid-dissociable group, and a structural unit (IV) containing a fluorine atom, which is a structural unit other than the structural unit (III) containing a polar group and the structural unit (I ′). And may have other structural units other than the above structural units (I ′) to (IV).

  [A '] The polymer may have one or more of the above structural units. [A ′] The structural unit (IV) other than the structural unit (II) containing the acid dissociable group, the structural unit (III) containing the polar group, and the structural unit (I ′) of the polymer and containing a fluorine atom ) And structural units other than the above structural units (I ′) to (III), those similar to those described as the respective structural units of the polymer [A] can be used. Also, preferred as each structural unit is the same as in the case of the polymer [A]. Hereinafter, the structural unit (I ′) will be described.

（式（１’）中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４は、それぞれ独立して、水素原子、フッ素原子、メチル基又はトリフルオロメチル基である。Ｒ^５及びＲ^６は、それぞれ独立して、水素原子又は炭素数１〜２０の１価の有機基である。Ｌ’は、炭素数２〜８のアルキレン鎖、上記アルキレン鎖が有する水素原子の一部又は全部を置換基で置換した基又は上記アルキレン鎖の炭素−炭素間に硫黄原子、窒素原子若しくは酸素原子を含む基である。）
[Structural unit (I ')]
The structural unit (I ′) is a structural unit represented by the following formula (1 ′).

(In the formula (1 ′), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ⁵ and R ⁶ are each Independently, it is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, and L ′ is an alkylene chain having 2 to 8 carbon atoms, or a part or all of the hydrogen atoms of the alkylene chain is a substituent. A substituted group or a group containing a sulfur atom, a nitrogen atom or an oxygen atom between carbon and carbon of the alkylene chain.)

As for R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ of the polymer [A ′], the same as those exemplified as each of the above polymers [A] can be used. The preferred components are the same as in the case of the polymer [A]. Hereinafter, the group (L ′) will be described.

(Group (L '))
The group (L ') is an alkylene chain having 2 to 8 carbon atoms, a group in which part or all of the hydrogen atoms of the alkylene chain is substituted with a substituent, or a sulfur atom or a nitrogen atom between the carbon atoms of the alkylene chain. Alternatively, it is a group containing an oxygen atom.

  As the substituent for substituting the hydrogen atom of the alkylene chain represented by L ', the same substituents as those described as the substituent for the group (L) can be used. Preferred substituents are the same as those for the group (L). As the sulfur atom contained between the carbon and carbon of the alkylene chain represented by L ′ and the nitrogen atom contained between the carbon and carbon of the alkylene chain represented by L ′, each of the above groups (L) The same ones described as atoms can be used. The preferred atoms are the same as those for the group (L).

  Examples of the oxygen atom included between carbon and carbon of the alkylene chain represented by L ′ include an oxygen atom of —O—, an oxygen atom included in —CO—, —COO—, and —OCO—. Can be

  The chain length of the group (L ') is preferably an integer of 2 to 5, and more preferably an integer of 2 to 4, from the viewpoint of the polymerizability of the monomer giving the structural unit (I').

  Examples of the group containing an oxygen atom between carbon and carbon of the alkylene chain include a group represented by the following formula (L ').

In the formula (L ′), X ′ is a divalent linking group containing an oxygen atom or an oxygen atom linked to at least one of — (CH ₂ ) _m — and — (CH ₂ ) _n —. However, X 'does not include an alkylene chain. m and n have the same meanings as in the above formula (L).

  Examples of the divalent linking group containing an oxygen atom represented by the above X ′ include, for example, —O—, a group constituting an oxygen atom included between carbon and carbon of the alkylene chain represented by the above L ′. Examples include the same groups as the groups.

  Among them, from the viewpoint of more appropriately adjusting the interaction between the acid generated from the [B] acid generator in the resist film and the [A '] polymer and improving the lithography performance, -O- is preferable.

  Examples of the structural unit (I ′) include structural units exemplified as the structural unit (I) and structural units represented by the following formulas (A′-1) to (A′-4) (hereinafter, “structural unit ( I'-1) to (I'-4) ").

  As the structural unit (I ′), the structural units (I-1) to (I-12), (I-15) to (I-17), (I-20) to (I-23), (I- 25) to (I-32), (I-34) to (I-36), (I'-1) and (I'-2).

  The lower limit of the content ratio of the structural unit (I ′) of the polymer [A1 ′] is preferably 1 mol%, more preferably 3 mol%, based on all the structural units constituting the polymer [A1 ′]. 8 mol% is more preferable, and 20 mol% is particularly preferable. The upper limit of the content ratio of the structural unit (I ') is preferably 90 mol%, more preferably 70 mol%, further preferably 50 mol%, and particularly preferably 40 mol%. The lower limit of the content of the structural unit (I) in the [A2 ′] polymer is preferably 1 mol%, more preferably 5 mol%, and more preferably 10 mol%, based on all the structural units constituting the [A2 ′] polymer. Mole% is more preferred, and 50 mol% is particularly preferred. The upper limit of the content ratio of the structural unit (I ') is preferably 95 mol%, more preferably 90 mol%, further preferably 85 mol%, and particularly preferably 80 mol%. [A '] The lithography performance of the radiation-sensitive resin composition (I') can be improved by setting the content of the structural unit (I) of the polymer in the above range.

  The content ratio of the structural unit (I ′) of the polymer [A1 ′] may be 100 mol% based on all structural units constituting the polymer [A1 ′]. By setting the content of the structural unit (I) in the [A1 ′] polymer within the above range, the [A1 ′] polymer can be made uniform, and the radiation-sensitive resin composition (I ′) Lithography performance can be further improved.

  Examples of the monomer giving the structural unit (I ') include a compound represented by the following formula (i') (hereinafter, also referred to as "compound (i ')").

In the formula (i ′), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and L ′ have the same meanings as in the formula (1 ′).

  The compound (i ') can be synthesized, for example, by the same method as that for the compound (i).

<Method for synthesizing [A ′] polymer>
The polymer [A '] can be synthesized, for example, by the same method as the polymer [A] described above.

  [A ′] The lower limit of the weight average molecular weight (Mw) of the polymer in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 1,000, more preferably 2,000, still more preferably 2,500, and 3, 000 is particularly preferred. The upper limit of Mw is preferably 50,000, more preferably 30,000, still more preferably 20,000, and particularly preferably 15,000. [A '] When the Mw of the polymer is in the above range, the coating property and the development defect suppressing property of the radiation-sensitive resin composition (I) are improved. [A '] When the Mw of the polymer is less than the above lower limit, a resist film having sufficient heat resistance may not be obtained.

  [A '] The lower limit of the ratio (Mw / Mn) of Mw to the number average molecular weight (Mn) in terms of polystyrene by GPC of the polymer is usually 1, and preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3 and more preferably 2.5.

  Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples. In addition, each measurement in an Example and a comparative example was performed by the following method.

[Weight average molecular weight (Mw) and number average molecular weight (Mn)]
Using a GPC column (Tosoh “G2000HXL”: two, “G3000HXL”: one, “G4000HXL”: one), flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass %, Sample injection volume: 100 μL, column temperature: 40 ° C., detector: measured by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard under the analysis conditions of a differential refractometer. The degree of dispersion (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[ ¹³ C-NMR analysis]
Using "JNM-ECX400" manufactured by JEOL Ltd., using heavy chloroform as a measurement solvent, analysis was performed to determine the content ratio (mol%) of each structural unit in each polymer.

<Synthesis of Compound>
[Synthesis Example 1] (Synthesis of Compound (M-1))
22.1 g (160 mmol) of potassium carbonate, 30 g (155 mmol) of a compound represented by the following formula (m-1), and 80 mL of tetrahydrofuran were added to a 500 mL round bottom flask, and stirring was started. Thereto, a solution of 5.2 g (80.0 mmol) of malononitrile dissolved in 40 mL of tetrahydrofuran was added dropwise. After the addition, the mixture was stirred at room temperature for 1 hour. Thereafter, the temperature was raised to 50 ° C., and the mixture was heated and stirred for 6 hours. After removing inorganic salts by filtration, the solvent was distilled off and ethyl acetate was added. After washing three times with water, it was dried with anhydrous sodium sulfate. The solvent was distilled off, and the residue was purified by column chromatography to obtain 21.9 g (yield 97%) of a compound represented by the following formula (M-1).

[Synthesis Examples 2 to 30] (Synthesis of Compounds (M-2) to (M-30))
By appropriately selecting the precursor and performing the same operation as in Synthesis Example 1, compounds represented by the following formulas (M-2) to (M-30) were synthesized.

<Synthesis of [A] polymer, [E] polymer and [F] polymer>
The monomers used in the synthesis of the [A] polymer, [E] polymer and [F] polymer other than the compounds (M-1) to (M-30) synthesized above are shown below.

[Synthesis Example 31] (Synthesis of polymer (A1-1))
9.08 g (50 mol%) of the compound represented by the above formula (M′-2), 8.23 g (40 mol%) of the compound represented by the above formula (M′-1), ) Is dissolved in 40 g of 2-butanone, and 0.76 g (5 mol% based on all monomers) of AIBN is added as an initiator to prepare a monomer solution. Prepared. Next, a 100 mL three-necked flask containing 20 g of 2-butanone was purged with nitrogen for 30 minutes, and then heated to 80 ° C. with stirring, and the monomer solution prepared above was added dropwise using a dropping funnel over 3 hours. The start of the dropping was defined as the start time of the polymerization reaction, and the polymerization reaction was performed for 6 hours. After the completion of the polymerization reaction, the polymerization solution was cooled with water to 30 ° C. or lower. The cooled polymerization solution was put into 400 g of methanol, and the precipitated white powder was separated by filtration. The filtered white powder was washed twice with 80 g of methanol, filtered, and dried at 50 ° C. for 17 hours to synthesize a white powdery polymer (A1-1) (14.8 g, yield 74). %). Mw of the polymer (A1-1) was 7,200, and Mw / Mn was 1.53. As a result of ¹³ C-NMR analysis, it is derived from the compound represented by the above formula (M′-2), the compound represented by the above formula (M′-1) and the compound represented by the above formula (M-1). The content ratios of the respective structural units were 50.1 mol%, 40.2 mol%, and 9.7 mol%, respectively.

[Synthesis Example 69] (Synthesis of polymer (A1-39))
42.99 g (50 mol%) of the compound represented by the above formula (M′-3), 41.62 g (40 mol%) of the compound represented by the above formula (M′-2), 15.39 g (10 mol%) of the compound represented by the formula (1), 4.35 g of AIBN (5 mol% based on all monomers) as an initiator and 1,14 g of t-dodecyl mercaptan are dissolved in 100 g of propylene glycol monomethyl ether. Thereafter, under a nitrogen atmosphere, the reaction temperature was maintained at 70 ° C., and copolymerization was carried out for 16 hours. After the completion of the polymerization reaction, the polymerization solution was dropped into 1,000 g of n-hexane to coagulate and purify the polymer. Next, 150 g of propylene glycol monomethyl ether was added again to the above polymer, and then 150 g of methanol, 34 g of triethylamine and 6 g of water were further added, and a hydrolysis reaction was carried out for 8 hours while refluxing at the boiling point. After completion of the reaction, the solvent and triethylamine were distilled off under reduced pressure, and the obtained polymer was dissolved in 150 g of acetone, and then dropped into 2,000 g of water to coagulate. After drying for a time, a polymer (A1-39) as a white powder was obtained (62.1 g, yield 70%). Mw of the polymer (A1-39) was 7,000, and Mw / Mn was 1.87. As a result of ¹³ C-NMR analysis, the content ratio of each structural unit derived from p-hydroxystyrene, the compound represented by the above formula (M′-2) and the compound represented by the above formula (M-1) is as follows: They were 50.2 mol%, 40.1 mol%, and 9.7 mol%, respectively.

[Synthesis Examples 32 to 68 and 71 and 72] (Synthesis of Polymers (A1-2) to (A1-38), (F-1) and (F-2))
Polymers (A1-2) to (A1-38) and (A1-38) and (A1-38) were obtained by performing the same operation as in Synthesis Example 31 except that the components having the types and contents shown in Table 1, Table 2, or Table 3 below were used. F-1) and (F-2) were synthesized.

[Synthesis Example 70] (Synthesis of polymer (A1-40))
A polymer (A1-40) was synthesized by performing the same operations as in Synthesis Example 69 except for using the components and the contents shown in Table 3 below.

[Synthesis Example 73] (Synthesis of polymer (E-1))
71.67 g (70 mol%) of the compound represented by the above formula (M′-12) and 28.33 g (30 mol%) of the compound represented by the above formula (M′-13) were combined with 100 g of 2-butanone. And dimethyl 2,2'-azobisisobutyrate 6.47 g (5 mol% based on all monomers) was dissolved as an initiator to prepare a monomer solution. Next, a 1,000-mL three-necked flask containing 100 g of 2-butanone was purged with nitrogen for 30 minutes, and then heated to 80 ° C. with stirring, and the monomer solution prepared above was added dropwise using a dropping funnel over 3 hours. . The start of the dropping was defined as the start time of the polymerization reaction, and the polymerization reaction was performed for 6 hours. After the completion of the polymerization reaction, the polymerization solution was cooled with water to 30 ° C. or lower. After the reaction solution was transferred to a 2 L separatory funnel, the polymerization solution was uniformly diluted with 150 g of n-hexane, and 600 g of methanol was added and mixed. Next, 30 g of distilled water was added, and the mixture was further stirred and allowed to stand for 30 minutes. Thereafter, the lower layer was recovered to obtain a propylene glycol monomethyl ether acetate solution containing the polymer (E-1) as a solid content (yield: 60%). Mw of the polymer (E-1) was 7,200, and Mw / Mn was 2.00. As a result of ¹³ C-NMR analysis, the content ratio of each of the structural units derived from the compound represented by the formula (M′-12) and the compound represented by the formula (M′-13) was 71.1. Mol% and 28.9 mol%.

[Synthesis Examples 74 to 76] (Synthesis of Polymers (A2-1) to (A2-3))
Polymers (A2-1) to (A2-3) were synthesized by performing the same operations as in Synthesis Example 73 except for using the components and the contents shown in Table 4 below.

<Preparation of radiation-sensitive resin composition (J)>
[B] Acid generator, [C] solvent, [D] acid diffusion controller and [G] used in the preparation of radiation-sensitive resin compositions (J) of Examples 1 to 45 and Comparative Examples 1 and 2 below. The uneven distribution promoter is shown below.

[[B] acid generator]
Each structural formula is shown below.
B-1: triphenylsulfonium 2- (adamantan-1-ylcarbonyloxy) -1,1,3,3,3-pentafluoropropane-1-sulfonate B-2: triphenylsulfonium norbornane sultone-2-yloxy Carbonyl difluoromethanesulfonate B-3: triphenylsulfonium 3- (piperidin-1-ylsulfonyl) -1,1,2,2,3,3-hexafluoropropane-1-sulfonate B-4: triphenylsulfonium adamantane- 1-yloxycarbonyldifluoromethanesulfonate

[[C] solvent]
C-1: Propylene glycol monomethyl acetate acetate C-2: Cyclohexanone

[[D] Acid diffusion controller]
Each structural formula is shown below.
D-1: triphenylsulfonium salicylate D-2: triphenylsulfonium 10-camphorsulfonate D-3: N- (n-undecane-1-ylcarbonyloxyethyl) morpholine D-4: 2,6-dii -Propylaniline D-5: tri-n-pentylamine

[[G] Localization promoting agent]
G-1: γ-butyrolactone

[Example 1]
[A] 100 parts by mass of (A1-1) as a polymer, [B] 8.5 parts by mass of (B-1) as an acid generator, and [C] 2,240 parts by mass of (C-1) as a solvent And (C-2) 960 parts by mass, [D] 2.3 parts by mass as an acid diffusion controller, (E) 3 parts by mass of (E-1) as a polymer, and [G] A radiation-sensitive resin composition (J-1) was prepared by mixing 30 parts by mass of (G-1) as a localization accelerator and filtering the mixture with a membrane filter having a pore size of 0.2 μm.

[Examples 2 to 45, Comparative Examples 1 and 2]
Each radiation-sensitive resin composition was prepared in the same manner as in Example 1 except that the components and the amounts shown in Table 5, Table 6, or Table 7 were used.

<Formation of resist pattern (1)>
Using a spin coater ("CLEAN TRACK ACT12" of Tokyo Electron)) on the surface of a 12-inch silicon wafer, a composition for forming a lower antireflection film ("ARC66" of Brewer Science) was applied, and then 205 By heating at 60 ° C. for 60 seconds, a lower antireflection film having an average thickness of 105 nm was formed. Each of the radiation-sensitive resin compositions prepared above was applied onto the lower antireflection film using the spin coater, and subjected to PB at 90 ° C. for 60 seconds. Thereafter, the resultant was cooled at 23 ° C. for 30 seconds to form a resist film having an average thickness of 90 nm. Next, this resist film was subjected to optical conditions of NA = 1.3 and dipole (Sigma 0.977 / 0.782) using an ArF excimer laser immersion exposure apparatus (“NSR-S610C” manufactured by NIKON). , 40 nm line and space (1L1S) mask pattern. After the exposure, PEB was performed at 90 ° C. for 60 seconds. Thereafter, alkali development was performed using a 2.38% by mass aqueous solution of TMAH as an alkali developer, washed with water, and dried to form a positive resist pattern. In forming the resist pattern, the line width formed through a one-to-one line-and-space mask having a target size of 40 nm, and the exposure amount formed in a one-to-one line-and-space having a line width of 40 nm is defined as an optimum exposure amount. did.

<Formation of resist pattern (2)>
A negative resist pattern was prepared in the same manner as in the formation of the resist pattern (1) except that the organic solvent was developed using n-butyl acetate instead of the TMAH aqueous solution and washing with water was not performed. Was formed.

<Evaluation>
Each radiation-sensitive resin composition was evaluated by measuring the formed resist pattern according to the following method. The evaluation results are shown in Tables 8 and 9 below. The length of the resist pattern was measured using a scanning electron microscope (“CG-4100” manufactured by Hitachi High-Technologies Corporation).

[LWR performance]
The resist pattern was observed from above the pattern using the above scanning electron microscope. The line width was measured at an arbitrary point in a total of 50 points, and a 3 sigma value was obtained from the distribution of the measured values, which was defined as LWR performance (nm). The LWR performance indicates that the smaller the value, the better.

[Resolution]
The dimension of the minimum resist pattern that was resolved at the above optimum exposure amount was measured, and the measurement result was defined as the resolution (nm). The smaller the measured value, the better the resolution.

[Cross-sectional shape]
The cross-sectional shape of the resist pattern resolved at the optimum exposure dose was observed, and the line width Lb at the middle of the resist pattern and the line width La at the top of the film were measured. At this time, when 0.90 ≦ La / Lb ≦ 1.10.

[Depth of focus]
Observe the dimensions when the focus is changed in the depth direction in the resist pattern resolved at the above optimum exposure dose, and the depth direction in which the pattern dimensions fall within 90% to 110% of the standard without any bridges or residues. Was measured, and the measurement result was defined as the depth of focus (nm). The larger the measured value, the better the depth of focus.

[MEEF]
At the above optimum exposure dose, the resist pattern that is resolved with five mask sizes (38.0 nm Line / 80 nm Pitch, 39.0 nm Line / 80 nm Pitch, 40.0 nm Line / 80 nm Pitch, 41.0 nm Line / 80 nm Pitch, 42.0 nm Line / 80 nm Pitch) The line width was measured. The measured values are plotted with the horizontal axis as the mask size and the vertical axis as the line width formed at each mask size, and the slope of the approximate straight line calculated by the least squares method is obtained. The slope is defined as the MEEF performance. The smaller the measured value, the better the MEEF.

[Development defect suppression]
The number of defects in the resist pattern resolved at the optimum exposure dose was measured using a defect inspection apparatus (“KLA2810” manufactured by KLA-Tencor). Then, the measured defects were classified into those determined to be derived from the resist film and those derived from the outside, and the number of defects determined to be derived from the resist film was calculated and defined as the development defect suppressing property (cm ² ). The less development defects are determined, the better the number of defects determined to be derived from the resist film.

[Film shrinkage suppression]
Using a spin coater ("CLEAN TRACK ACT12" manufactured by Tokyo Electron) on the surface of a 12-inch silicon wafer, a composition for forming a lower antireflection film ("ARC66" manufactured by Brewer Science) was applied. For 60 seconds to form a lower antireflection film having an average thickness of 105 nm. Each of the radiation-sensitive resin compositions prepared above was applied onto the lower antireflection film using the spin coater, and subjected to PB at 90 ° C. for 60 seconds. Thereafter, the resultant was cooled at 23 ° C. for 30 seconds to form a resist film having an average thickness of 90 nm. Next, the resist film was subjected to overall surface exposure at 70 mJ using an ArF excimer laser immersion exposure apparatus (“NSR-S610C” manufactured by NIKON), and then the film thickness was measured to determine the average thickness A. Subsequently, after PEB was performed at 90 ° C. for 60 seconds, the film thickness was measured again to determine the average thickness B. At this time, 100 × (AB) / A (%) was obtained, and this was defined as the film shrinkage inhibiting property (%). The results are shown in Table 10 below. The smaller the measured value is, the better the film shrinkage suppressing property is.

[Preparation of radiation-sensitive resin composition for electron beam exposure]
[Example 46]
[A] 100 parts by mass of (A1-1) as a polymer, [B] 20 parts by mass of (B-1) as an acid generator, [C] 4280 parts by mass of (C-1) as a solvent, [D] ] 3.6 parts by mass of (D-1) and 1830 parts by mass of (C-2) as an acid diffusion controller are mixed, and the mixture is filtered through a membrane filter having a pore size of 0.2 µm to obtain a radiation-sensitive resin composition (J -46) was prepared.

[Examples 47 to 50, Comparative Examples 3 and 4]
Each radiation-sensitive resin composition was prepared in the same manner as in Example 46, except that the components and the amounts of the components shown in Table 11 below were used.

<Formation of resist pattern (3)>
Each radiation-sensitive resin composition described in Table 11 was applied to the surface of an 8-inch silicon wafer using a spin coater (“CLEAN TRACK ACT8” manufactured by Tokyo Electron Ltd.), and PB was performed at 90 ° C. for 60 seconds. . Thereafter, the resultant was cooled at 23 ° C. for 30 seconds to form a resist film having an average thickness of 50 nm. Next, the resist film was irradiated with an electron beam using a simple electron beam lithography system (“Model“ HL800D ”manufactured by Hitachi, Ltd., output: 50 KeV, current density: 5.0 A / cm ² ). After the irradiation, PEB was performed at 120 ° C. for 60 seconds. Thereafter, development was performed at 23 ° C. for 30 seconds using a 2.38% by mass aqueous solution of TMAH as an alkali developer, washed with water, and dried to form a positive resist pattern.

<Formation of resist pattern (4)>
A negative resist pattern was prepared in the same manner as in the formation of the resist pattern (1) except that the organic solvent was developed using n-butyl acetate instead of the TMAH aqueous solution and washing with water was not performed. Was formed.

<Evaluation>
The same evaluation as in Examples 1 to 45 was performed on the resist pattern formed using each of the radiation-sensitive resin compositions. The evaluation results are shown in Table 12 below.

  As can be seen from the results of Table 8, Table 9, Table 10 and Table 12, according to the radiation-sensitive resin compositions of Examples, in both of ArF exposure and electron beam exposure, alkali development and organic development were also performed. In any case, it is excellent in LWR performance, resolution, rectangularity of cross-sectional shape, depth of focus, MEEF performance, development defect suppression property and film shrinkage suppression property. It is known that electron beam exposure and EUV exposure have a correlation in the performance of the obtained resist pattern. Therefore, it is presumed that the radiation-sensitive resin compositions of the examples exhibit excellent lithography performance even in EUV exposure.

  According to the radiation-sensitive resin composition and the method for forming a resist pattern of the present invention, a resist pattern having excellent LWR performance, resolution, rectangular cross-sectional shape, depth of focus, MEEF performance, development defect suppression properties, and film shrinkage suppression properties Can be formed. Therefore, the radiation-sensitive resin composition and the method for forming a resist pattern can be suitably used for the manufacture of semiconductor devices, which are expected to be further miniaturized in the future.

Claims (6)

A first polymer having a structural unit represented by the following formula (1),
A radiation-sensitive resin composition containing a radiation-sensitive acid generator and a solvent.

(In the formula (1), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ⁵ and R ⁶ are each independently And is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, and L is an alkylene chain having 2 to 8 carbon atoms and satisfying the following (i), (ii) or (iii): It is.
(I) a group in which part or all of the hydrogen atoms of the alkylene chain is substituted with a substituent, wherein the substituent is a fluorine atom, a nitro group, or an organic group having 1 to 10 carbon atoms.
(Ii) of the alkylene chain carbons - it is a group containing a sulfur atom between carbon atoms, the sulfur atom, a sulfur atom or an -SO- or -SO 2 of -S- _- a sulfur atom contained in the.
(Iii) of the alkylene chain carbons - is a group containing a nitrogen atom between carbon atoms, the nitrogen atom, -NR ⁷ - or ^-N + ^R 8 ^{R 9} - is a nitrogen atom contained in said ^{R 7} is A hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms, and each of R ⁸ and R ⁹ is independently a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms, or These groups represent a ring structure having 3 to 20 ring members which are combined with each other and formed together with the nitrogen atom to which they are bonded. ) The formula (1) radiation sensitive resin composition of claim 1 wherein at least one of R ⁵ and R ⁶ is an acid dissociable group for. The radiation-sensitive resin composition according to claim 1, wherein at least one of R ⁵ and R ⁶ in the formula (1) is a group containing a polar group. A first polymer having a structural unit represented by the following formula (1),
A radiation-sensitive acid generator, and
solvent
Containing
The first polymer is a polymer having a fluorine atom,
The first low mass content of fluorine atoms than polymer and the second polymer further be that the radiation-sensitive resin composition containing an acid-dissociable group.

(In the formula (1), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ⁵ and R ⁶ are each independently And is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, L is an alkylene chain having 2 to 8 carbon atoms, and a part or all of the hydrogen atoms of the alkylene chain is a substituent. Or a group containing a sulfur atom or a nitrogen atom between carbon and carbon of the alkylene chain.) Forming a resist film,
Exposing the resist film, and developing the exposed resist film,
A resist pattern forming method of forming a radiation-sensitive resin composition according to any one of claims 4, the resist film from claim 1. Forming a resist film,
Exposing the resist film, and developing the exposed resist film with a developer containing an organic solvent as a main component,
The resist film, a resist pattern forming method of forming a radiation-sensitive resin composition,
The radiation-sensitive resin composition is a polymer having a structural unit represented by the following formula (1 ′),
A method for forming a resist pattern, comprising a radiation-sensitive acid generator and a solvent.

(In the formula (1 ′), R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R ⁵ and R ⁶ are each Independently, it is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms, L 'is an alkylene chain having 2 to 8 carbon atoms, and is represented by the following (i), (ii), (iii) or It is a group satisfying (iv) .
(I) a group in which part or all of the hydrogen atoms of the alkylene chain is substituted with a substituent, wherein the substituent is a fluorine atom, a nitro group, or an organic group having 1 to 10 carbon atoms.
(Ii) of the alkylene chain carbons - it is a group containing a sulfur atom between carbon atoms, the sulfur atom, a sulfur atom or an -SO- or -SO 2 of -S- _- a sulfur atom contained in the.
(Iii) of the alkylene chain carbons - is a group containing a nitrogen atom between carbon atoms, the nitrogen atom, -NR ⁷ - or ^-N + ^R 8 ^{R 9} - is a nitrogen atom contained in said ^{R 7} is A hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms, and each of R ⁸ and R ⁹ is independently a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms, or These groups represent a ring structure having 3 to 20 ring members which are combined with each other and formed together with the nitrogen atom to which they are bonded.
(Iv) a group containing an oxygen atom between carbon and carbon of the alkylene chain, wherein the oxygen atom is an oxygen atom of —O— or an oxygen atom included in —CO—, —COO—, or —OCO—. . )