JP2005048128A - (co)polymer, manufacturing method, resist composition and pattern-forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer useful as a constituent resin of a resist or the like, its manufacturing method, a resist composition which exhibits high sensitivity and high resolution, hardly forms a microgel and gives reduced line edge roughness when used for DUV excimer laser lithography or the like, and a pattern-forming method using the resist composition. <P>SOLUTION: The (co)polymer comprises a constituent unit represented by formula (1). A resist pattern is formed using the resist composition comprising the resist polymer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a (co) polymer useful for a resist material and the like, in particular, a (co) polymer for a resist material suitable for fine processing using an excimer laser or an electron beam, a method for producing the same, and the (co) polymer. The present invention relates to a resist composition and a pattern forming method.

  In recent years, in the field of microfabrication in the manufacture of semiconductor elements and liquid crystal elements, miniaturization has rapidly progressed due to advances in lithography technology. As a method for miniaturization, generally, the wavelength of irradiation light emitted from an exposure light source is shortened. Specifically, it is represented by conventional g-line (wavelength: 438 nm) and i-line (wavelength: 365 nm). Irradiation light is changing from ultraviolet rays to DUV (Deep Ultra Violet).

At present, KrF excimer laser (wavelength: 248 nm) lithography technology is introduced into the market, and ArF excimer laser (wavelength: 193 nm) lithography technology for further shortening the wavelength is about to be introduced. Further, as a next-generation technique, an F ₂ excimer laser (wavelength: 157 nm) lithography technique has been studied. In addition, an electron beam lithography technique has been energetically studied as a slightly different type of lithography technique.
As a high-resolution resist for such short-wavelength irradiation light or electron beam, a “chemically amplified resist” containing a photoacid generator has been proposed. At present, improvement and development of this chemically amplified resist are energetic. It is advanced to.

In order to shorten the wavelength of irradiation light, the resin used for the resist is also forced to change its structure. For example, in KrF excimer laser lithography, polyhydroxystyrene having high transparency with respect to irradiation light having a wavelength of 248 nm, or a hydroxyl group protected with an acid dissociable, dissolution inhibiting group is used. However, in ArF excimer laser lithography, the resin is not necessarily sufficiently transparent with respect to irradiation light having a wavelength of 193 nm, and often cannot be used.
Therefore, an acrylic resin that is transparent with respect to irradiation light with a wavelength of 193 nm has attracted attention as a resist resin used in ArF excimer laser lithography. As an example of this, acrylic resins containing structural units having an alicyclic skeleton are disclosed in Patent Documents 1-2.

  Patent Document 1 describes a polymer obtained by polymerizing a polymer precursor containing a (meth) acrylate derivative having an alicyclic lactone structure in a photoresist material for lithography using irradiation light of 220 nm or less. ing. However, the resist composition containing this polymer has many microgels, and the resist pattern obtained using this resist composition has poor pattern rectangularity.

  Patent Document 2 describes a polymer containing a structural unit having an alicyclic lactone structure, a structural unit having a group capable of leaving by an acid, and a structural unit having a hydroxyl group or a cyano group.

  However, in the resist composition containing this polymer, the side wall roughness of the resist pattern generated by patterning with an excimer laser and the subsequent development processing, that is, the line edge roughness cannot be sufficiently suppressed. In some cases, the circuit width may be non-uniform or the circuit itself may be disconnected, leading to a decrease in yield in the semiconductor manufacturing process.

JP 2000-26446 A JP 2003-122007 A

  The present invention is a (co) polymer useful as a constituent resin such as a resist, a method for producing the same, and when used in DUV excimer laser lithography, etc., has high sensitivity and high resolution, and produces less microgels. An object of the present invention is to provide an excellent resist composition having a small line edge roughness and a pattern forming method using the resist composition.

  As a result of intensive studies in view of the above problems, the present inventors have found that a polymer having a specific alicyclic lactone structure and / or a polymer having a specific cyano group and / or a specific in DUV excimer laser lithography or electron beam lithography. By using a polymer having an acid-eliminable group and / or a polymer having a specific alkoxy group in a resist composition, high sensitivity and high resolution are not impaired, line edge roughness is small, The inventors found that the production was suppressed, and reached the present invention.

  That is, the first of the present invention is a (co) polymer containing a structural unit represented by the following formula (1).

（式（１）中、Ｒ¹は水素原子またはメチル基を表し、Ｒ²〜Ｒ⁵はそれぞれ独立して水素原子、−Ｒ⁷−ＣＮ、−Ｒ⁸−ＣＨ(ＣＮ)₂、−Ｒ⁹−ＣＯＯ−Ｒ¹⁰、−（ＣＨ_３）_ｍ−Ｃ（ＣＦ_３）_２−ＯＨのいずれかを表し、Ｒ⁶は水素原子、炭素数１〜３の分岐を有していてもよいアルコキシ基、シアノ基、または炭素数１〜６のエステル基を表すか、Ｒ²もしくはＲ³とＲ⁴もしくはＲ⁵とが、または、Ｒ²もしくはＲ³とＲ⁶とが、または、Ｒ⁴もしくはＲ⁵とＲ⁶とが一緒になって−ＣＯＯ−(ＣＨ₂)_ｎ−を表し、ｎは０〜３の整数を表す。Ｒ⁷〜Ｒ⁹はそれぞれ独立して炭素数１〜４の分岐を有していてもよいアルキレン基か単結合を表し、Ｒ¹⁰は酸脱離性基を表す。ＸおよびＹは、一方がメチル基で、もう一方がイソプロピル基である。ｍは０〜６の整数を表す）

(In the formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ^{2 to} R ⁵ are each independently a hydrogen atom, —R ⁷ —CN, —R ⁸ —CH (CN) ₂ , —R ^9. —COO—R ¹⁰ , — (CH ₃ ) _m —C (CF ₃ ) ₂ —OH is represented, and R ⁶ is a hydrogen atom, an alkoxy group optionally having 1 to 3 carbon atoms, A cyano group or an ester group having 1 to 6 carbon atoms, R ² or R ³ and R ⁴ or R ⁵ , or R ² or R ³ and R ⁶ , or R ⁴ or R ⁵ And R ⁶ together represent —COO— (CH ₂ ) _n —, where n represents an integer of 0 to _3. R ^{7 to} R ⁹ each independently has 1 to 4 carbon atoms. R ¹⁰ represents an acid-eliminable group, one of which is a methyl group and the other is an isopropyl group M represents an integer of 0 to 6)

  The “ester group having 1 to 6 carbon atoms” means “carboxy group esterified with an alcohol having 1 to 6 carbon atoms”.

  The second of the present invention is a (co) polymer having a structural unit represented by the following formula (1-a).

（式（１−ａ）中、Ｒ¹〜Ｒ^４、ＸおよびＹは式（１）と同義である。）

(In formula (1-a), R ^{1 to} R ⁴ , X and Y have the same meanings as in formula (1).)

  The third of the present invention is a (co) polymer having a structural unit represented by the following formula (1-b).

（式（１−ｂ）中、Ｒ^１、Ｘ、Ｙ、Ｒ^６は式（１）と同義である。）

(In formula (1-b), R ¹ , X, Y, and R ⁶ have the same meanings as in formula (1).)

  The fourth aspect of the present invention is the (co) polymerization in which the (co) polymerization is carried out while dropping a monomer that is a constituent unit of the (co) polymer of the present invention into a polymerization vessel. It is a manufacturing method of a polymer.

  A fifth aspect of the present invention is a chemically amplified resist composition comprising at least one of the above (co) polymers and a photoacid generator.

  A sixth aspect of the present invention is a step of applying at least one of the resist compositions on a substrate to be processed, a step of exposing with light having a wavelength of 250 nm or less, and developing using a developer. A pattern forming method including a process.

  A seventh aspect of the present invention includes a step of applying at least one of the resist compositions on a substrate to be processed, a step of exposing with an electron beam, and a step of developing using a developer. This is a pattern forming method.

  The (co) polymer of the present invention is useful as a constituent resin for paints, adhesives, pressure-sensitive adhesives, ink resins, resists, optical materials and the like. In particular, when the polymer of the present invention is used as a resist resin in DUV excimer laser lithography or the like, it has high sensitivity and high resolution, small line edge roughness, and little generation of microgel. Therefore, the resist composition using the resist polymer of the present invention can be suitably used for lithography using DUV excimer laser lithography or electron beam lithography, particularly ArF excimer laser (wavelength: 193 nm). In addition, a resin suitable for a resist composition can be produced by the production method of the present invention. In addition, the pattern forming method of the present invention can stably form a high-precision fine resist pattern.

  The resist (co) polymer of the present invention contains the structural unit represented by the formula (1). Here, “(co) polymerization” means homopolymerization or copolymerization.

  Such a (co) polymer of the present invention is useful as a constituent resin for paints, adhesives, pressure-sensitive adhesives, ink resins, resists, optical materials and the like. In particular, when the (co) polymer of the present invention is used as a resist resin in DUV excimer laser lithography or electron beam lithography, it has high sensitivity, high resolution, little generation of line edge roughness, and generation of a microgel Less resist composition can be obtained. Moreover, according to the pattern formation method using this resist composition, a highly accurate fine resist pattern can be formed stably.

Hereinafter, the present invention will be described in detail.
First, the (co) polymer represented by the formula (1) will be described.
The resist (co) polymer of the present invention contains the structural unit represented by the formula (1). Especially, since it is excellent in the adhesiveness to a metal surface etc. and etching tolerance, the structural unit represented by the said Formula (1-a) and the said Formula (1-b) is preferable. Among the structural units represented by the formula (1-a), those having a cyano group are preferable in that the amount of microgel is small and the line edge roughness is small.

  The structural unit represented by the formula (1) of the resist polymer of the present invention is obtained by (co) polymerizing a monomer having a structure represented by the following formula (1m). The monomer represented by the following formula (1m) may be one type or a mixture of two or more types.

（式（１ｍ）中、Ｒ¹〜Ｒ⁶、ｎ、ＸおよびＹは、式（１）と同義である。）

(In formula (1m), R ^{1 to} R ⁶ , n, X and Y have the same meanings as in formula (1).)

In the formula (1m), R ^{2 to} R ⁵ are preferably —CN and —CH (CN) ₂ from the viewpoint of excellent solubility in an organic solvent, and sensitivity when a (co) polymer is used as a resist composition. -COO-R ¹⁰ is preferable from the viewpoint of excellent resistance. R ⁶ is preferably a methoxy group, an ethoxy group, an n-propyl group, or an iso-propyl group from the viewpoint of excellent solubility in an organic solvent. R ^{2 to} R ⁶ are excellent in adhesion to the substrate to be processed, so that R ² or R ³ and R ⁴ or R ⁵ , or R ⁴ or R ⁵ and R ⁶ are combined to form —COO— ( CH ₂ ) _n — is preferable, and n = 0 or 1 is preferable from the viewpoint of excellent resolution when a (co) polymer is used as a resist composition.

Examples of the acid leaving group (hereinafter referred to as acid leaving group A) of R ¹⁰ include tert-butyl group, tert-amyl group, tetrahydropyran-2-yl group, tetrahydrofuran-2-yl group, 4- Methoxytetrahydropyran-4-yl group, 1-ethoxyethyl group, 1-butoxyethyl group, 1-propoxyethyl group, 3-oxocyclohexyl group, 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group 2- (iso-propyl) -2-adamantyl group, 8-methyl-8-tricyclo [5.2.1.0 ^2,6 ] decyl group, 8-ethyl-8-tricyclo [5.2.1. 0 ^2,6] decyl group, 4-methyl-4-tetracyclo [6.2.1.1 ^3,6 .0 ^2,7] dodecyl, 4-ethyl-4-tetracyclo [6.2.1.1 ^3,6 .0 ^2,7] dodecyl, 2-methyl-2-Bruno Bornyl group, 1,2,7,7-tetramethyl-2-norbornyl group, 2-acetoxymenthyl group, 2-hydroxymenthyl group, 1-methyl-1-cyclohexyl group, 1-ethyl-1-cyclohexyl group, 1 -(N-propyl) -1-cyclohexyl group, 1- (iso-propyl) -1-cyclohexyl group and the like, and tert-butyl group and tert-amyl group from the viewpoint of good solubility in organic solvents. Tetrahydropyran-2-yl group, 1-methyl-1-cyclohexyl group, 1-ethyl-1-cyclohexyl group, 1- (n-propyl) -1-cyclohexyl group, 1- (iso-propyl) -1- A cyclohexyl group is preferable, and 2-methyl-2-adamantyl group, 2-ethyl-2-adamantyl group, 2- ( iso-propyl) -2-adamantyl group, 8-methyl-8-tricyclo [5.2.1.0 ^2,6 ] decyl group, 8-ethyl-8-tricyclo [5.2.1.0 ^2,6 ] decyl group, 4-methyl-4-tetracyclo [6.2.1.1 ^3,6 .0 ^2,7] dodecyl, 4-ethyl-4-tetracyclo [6.2.1.1 ^{3, 6.} 0 ^2,7 ] dodecyl group, 2-methyl-2-norbornyl group and 1,2,7,7-tetramethyl-2-norbornyl group are preferable.
Here, the “acid leaving group” means a group that decomposes or leaves by the action of an acid.

  Specific examples of the monomer represented by the formula (1m) include monomers represented by the following formulas (3-1) to (3-100), but are not limited thereto. is not. In formulas (3-1) to (3-100), R represents a hydrogen atom or a methyl group.

  As the monomer represented by the formula (1m), the formula (3-8), the formulas (3-16) to (3-19), and the formulas described above are excellent in solubility in organic solvents. (3-21) to (3-24), formulas (3-31) to (3-54), formulas (3-56) to (3-59), formulas (3-61) to (3) -64) and the monomers represented by the formulas (3-95) to (3-100) are preferred. The monomer represented by the formula (3-8) is particularly preferable in that it is excellent in solubility in an organic solvent and excellent in copolymerizability with other monomers. Moreover, in the point which is excellent in the solubility to an organic solvent, and the adhesiveness to the to-be-processed substrate at the time of setting it as a resist composition, said Formula (3-16)-(3-19), said Formula (3- 21) to (3-24), the above formulas (3-56) to (3-59), the above formulas (3-61) to (3-64), and the above formulas (3-95) to (3-100). The monomer represented by the formula (3-16) to (3-19) and the formula (3-21) are more preferable because the resolution is excellent when a resist composition is used. ) To (3-24) and the monomers represented by the formulas (3-95) to (3-98) are particularly preferable.

  Moreover, as a monomer represented by said Formula (1m), from the point which is excellent in the sensitivity at the time of setting it as a resist composition, said Formula (3-25)-(3-54) and said Formula (3-65). ) To (3-88) are preferred. Among them, the monomers represented by the above formulas (3-65) to (3-88) are more preferable in view of excellent adhesion to a substrate to be processed when a resist composition is used, and other monomers. From the point which is excellent in copolymerizability with said Formula (3-65)-(3-68), said Formula (3-71)-(3-74), said Formula (3-77)-(3-80) And monomers represented by the above formulas (3-83) to (3-86) are particularly preferable.

  Moreover, as a monomer represented by the said Formula (1m), since the adhesiveness to the to-be-processed substrate at the time of setting it as a resist composition is excellent, said Formula (3-15) and said Formula (3-20) ), The above formula (3-55), the above formula (3-60), and the monomers represented by the above formulas (3-89) to (3-94) are preferable. Among these, in terms of excellent copolymerizability with other monomers, it is represented by the formula (3-15), the formula (3-20), and the formulas (3-89) to (3-92). Particularly preferred are monomers.

  The monomers represented by the formulas (3-1) to (3-100) can be produced, for example, by the following steps. The following process shows the production process of the monomer represented by the formula (3-15), but other monomers can be produced in a similar process.

原料であるテルピネンなどのジエンは、公知の方法で製造することができ、また、市販品を使用することもできる。テルピネンとアクリル酸エステルの環化付加反応は、公知の方法にて行うことができるが、好ましくはルイス酸などの触媒を用いるとよい。

Diene such as terpinene as a raw material can be produced by a known method, and a commercially available product can also be used. The cycloaddition reaction of terpinene and acrylic acid ester can be performed by a known method, but a catalyst such as Lewis acid is preferably used.

  The oxidation reaction for the double bond can be carried out by a known method, but preferably a peroxide such as hydrogen peroxide or perbenzoic acid is used. The subsequent lactonization can be carried out by a known method, but a catalyst such as a Lewis acid is preferably used. Further, the oxidation and lactonization of the double bond can be performed simultaneously.

  The esterification reaction of the obtained alcohol can be performed by a known method, but preferably a carboxylic acid halide such as methacryl chloride, an ester such as methyl methacrylate and vinyl methacrylate, and a carboxylic acid such as methacrylic acid. It is good to react. It is particularly preferable to react with a carboxylic acid halide in a solvent such as methylene chloride or toluene in the presence of a base such as triethylamine.

  Although the reaction intermediate produced | generated in the said process can be used for the following process, without refine | purifying, you may refine | purify by well-known methods, such as distillation and column chromatography. In addition, the reaction intermediate and the target monomer may include several structural isomers, geometric isomers, and optical isomers. In the present invention, the mixture of isomers can be used in the polymerization reaction as it is. Even if a reaction intermediate is contained, it can be used in the polymerization reaction as it is. The product of the above reaction is preferably purified by ordinary distillation, thin film distillation, recrystallization, column chromatography or the like, if necessary.

  Since the (co) polymer of the present invention can be used as a chemically amplified resist, it has an acid leaving group other than the structural unit represented by the formula (1) together with the structural unit represented by the formula (1). It is preferable that a structural unit is included (the acid leaving group contained in the structural unit other than the structural unit represented by the formula (1) is referred to as an acid leaving group B). Examples of the structural unit having the acid leaving group B include structures represented by the following formulas (10-1) to (10-4).

（式（１０−１）〜式（１０−４）中、Ｒはメチル基または水素原子を表す。）
これらの構成単位は、下記式（１１−１）〜（１１−４）で表される単量体を（共）重合することによって得られる。

(In formula (10-1) to formula (10-4), R represents a methyl group or a hydrogen atom.)
These structural units are obtained by (co) polymerizing monomers represented by the following formulas (11-1) to (11-4).

（式（１１−１）〜式（１１−４）中、Ｒはメチル基または水素原子を表す。）
レジストに必要とされるドライエッチング耐性が高い点から前記式（１１−３）、および前記式（１１−４）で表される単量体が好ましい。

(In formula (11-1) to formula (11-4), R represents a methyl group or a hydrogen atom.)
The monomer represented by the formula (11-3) and the formula (11-4) is preferable from the viewpoint of high dry etching resistance required for the resist.

  In this polymer, the structural units represented by the formula (1) need not all be the same, and two or more types may be mixed. The structural units having the acid leaving group B do not have to be all the same, and two or more types may be mixed. Moreover, in this polymer, each structural unit can take an arbitrary sequence. Therefore, this polymer may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer.

  In the resist polymer of the present invention, the structural unit having the acid-eliminable group B preferably contains an alicyclic skeleton from the viewpoint of excellent dry etching resistance required for the resist. An alicyclic skeleton is a skeleton having one or more cyclic saturated hydrocarbons. This cyclic saturated hydrocarbon may have a substituent. In order to introduce such a structural unit into the (co) polymer, for example, copolymerization may be performed using a monomer having an alicyclic skeleton.

  Examples of the monomer having an alicyclic skeleton include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, tricyclodecanyl (meth) acrylate, and (meth) acrylic acid. Tetracyclododecanyl, dicyclopentadienyl (meth) acrylate, and derivatives having a substituent on the alicyclic ring of these compounds are preferred. In the present invention, “(meth) acrylic acid” is a general term for acrylic acid and methacrylic acid.

Resist (co) polymers containing a structural unit having an acid leaving group B have excellent sensitivity, and if these structural units contain an alicyclic skeleton, they have excellent dry etching resistance. . Furthermore, when these structural units contain a hydroxyl group and a cyano group, they have excellent resist pattern rectangularity.
Monomers having an alicyclic skeleton can be used alone or in combination of two or more.

  In this polymer, the structural units represented by the formula (1), the formula (1-a), and the formula (1-b) are not necessarily the same, and two or more types are mixed. You may do. The structural units having the acid leaving group B need not all be the same, and two or more types may be mixed. Moreover, in this polymer, each structural unit can take an arbitrary sequence. Therefore, this polymer may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer.

  The total of the structural unit having an acid leaving group A and the structural unit having an acid leaving group B is preferably 30 mol% or more, and 35 mol% or more in terms of sensitivity and resolution with respect to the entire copolymer. More preferred. The total of the structural unit having the acid leaving group A and the structural unit having the acid leaving group B is preferably 80 mol% or less, more preferably 70 mol% or less, from the viewpoint of adhesion to a metal surface or the like. .

  Specific examples of the monomer having the acid leaving group B include monomers represented by the following formulas (12-1) to (12-26).

（式（１２−１）〜（１２−２６）中、Ｒは水素原子またはメチル基を示す。）
中でも、感度および解像度の点から、前記式（１２−１）、前記式（１２−２）、前記式（１２−４）、前記式（１２−１５）、および前記式（１２−１６）で表される単量体ならびにこれらの幾何異性体、光学異性体などが好ましく、パターン形状安定性の点から、前記式（１２−１９）、前記式（１２−２３）、および前記式（１２−２４）で表される単量体が好ましく、中でも前記式（１２−１）、前記式（１２−２）、前記式（１２−１６）、前記式（１２−２３）、および前記式（１２−２４）で表される単量体が特に好ましい。

(In formulas (12-1) to (12-26), R represents a hydrogen atom or a methyl group.)
Among these, in terms of sensitivity and resolution, the above formula (12-1), the above formula (12-2), the above formula (12-4), the above formula (12-15), and the above formula (12-16) are used. Monomers represented by these and geometrical isomers and optical isomers thereof are preferable. From the viewpoint of pattern shape stability, the above formula (12-19), the above formula (12-23), and the above formula (12- 24) is preferable, and among them, the formula (12-1), the formula (12-2), the formula (12-16), the formula (12-23), and the formula (12) are preferable. The monomer represented by -24) is particularly preferred.

  The resist (co) polymer of the present invention has a structural unit represented by the formula (1) and a structural unit having a lactone skeleton other than the structural unit represented by the formula (1) (hereinafter referred to as “having a lactone skeleton”). May be included as “structural unit B”. Among the structural units represented by the formula (1), those having a lactone skeleton are referred to as “structural unit A having a lactone skeleton”. A monomer that becomes a structural unit A having a lactone skeleton by opening a double bond is referred to as “monomer A having a lactone skeleton” (B is also the same).

In order to introduce the structural unit B having a lactone skeleton into the (co) polymer, for example, copolymerization may be performed using the monomer B having a lactone skeleton.
Examples of the monomer B having this lactone skeleton include (meth) acrylic acid derivatives having a δ-valerolactone ring, (meth) acrylic acid derivatives having a γ-butyrolactone ring, and (meth) acrylic having an alicyclic lactone. Examples include acid derivatives and the like, and derivatives having a substituent on the lactone ring of these compounds.

  The resist copolymer containing structural units A and B having a lactone skeleton is excellent in adhesion to a highly polar surface such as a metal surface, and these structural units contain an acid leaving group. Excellent sensitivity. Furthermore, when these structural units contain a high carbon density, they have excellent dry etching resistance.

Monomers A and B having a lactone skeleton can be used alone or in combination of two or more as required.
In this polymer, the structural units represented by the formula (1) need not all be the same, and two or more types may be mixed. The structural unit having an acid leaving group B and the structural unit B having a lactone skeleton need not all be the same, and two or more types may be mixed. Moreover, in this polymer, each structural unit can take an arbitrary sequence. Therefore, this polymer may be a random copolymer, an alternating copolymer, a block copolymer, or a graft polymer.

  The total ratio of the structural unit A having a lactone skeleton and the structural unit B having a lactone skeleton is preferably 30 mol% or more, and 35 mol% or more in terms of adhesion to a metal surface or the like with respect to the entire copolymer. More preferred. Further, the total of the proportions of the structural unit A having a lactone skeleton and the structural unit B having a lactone skeleton is preferably 80 mol% or less, and more preferably 70 mol% or less in terms of sensitivity and resolution.

  Specific examples of the monomer capable of introducing the structural unit B having such a lactone skeleton include monomers represented by the following formulas (13-1) to (13-24).

（式（１３−１）〜（１３−２４）中、Ｒは水素原子またはメチル基を示す。）
中でも、ドライエッチング耐性の点から、前記式（１３−６）、前記式（１３−８）、前記式（１３−１０）、前記式（１３−１２）、前記式（１３−１４）、前記式（１３−１６）、前記式（１３−１８）、および前記式（１３−２０）で表される単量体ならびにこれらの幾何異性体、光学異性体などが好ましく、有機溶剤への溶解性の点から、前記式（１３−１）、前記式（１３−２）、前記式（１３−７）、前記式（１３−１１）、前記式（１３−１５）、および前記式（１３−１９）で表される単量体ならびにこれらの幾何異性体、光学異性体などが好ましい。

(In formulas (13-1) to (13-24), R represents a hydrogen atom or a methyl group.)
Among these, from the point of dry etching resistance, the formula (13-6), the formula (13-8), the formula (13-10), the formula (13-12), the formula (13-14), the above Monomers represented by the formula (13-16), the above formula (13-18), and the above formula (13-20), and geometrical isomers, optical isomers, and the like thereof are preferable. From the above point, the formula (13-1), the formula (13-2), the formula (13-7), the formula (13-11), the formula (13-15), and the formula (13- The monomer represented by 19) and geometrical isomers and optical isomers thereof are preferable.

  In the (co) polymer of the present invention, when the structural unit represented by the formula (1) does not have the acid leaving group A and is not the structural unit A having a lactone skeleton, it is represented by the formula (1). The ratio of the structural unit to be formed is preferably 2 mol% or more, more preferably 5 mol%, and the upper limit is preferably 50 mol% or less, in terms of pattern rectangularity with respect to the whole (co) polymer. The mol% or less is more preferable.

  The resist (co) polymer of the present invention may contain a constituent unit other than the constituent unit having the acid-eliminable group B and the constituent unit having the lactone skeleton B. That is, the resist (co) polymer of the present invention is obtained by copolymerizing a monomer having an alicyclic skeleton and another monomer copolymerizable with a monomer having a lactone skeleton B. Also good.

  Examples of such other monomers include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, tricyclodecanyl (meth) acrylate, and dimethacrylate (meth) acrylate. Examples thereof include monomers having an alicyclic skeleton such as cyclopentadienyl and derivatives having a substituent on the cyclic hydrocarbon group of these compounds.

  Specific examples of the monomer having an alicyclic skeleton include monomers represented by the following formulas (60-1) to (60-4). In formulas (60-1) to (60-4), R represents a hydrogen atom or a methyl group.

また、それ以外の共重合可能な他の単量体としては、例えば、（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸２−エチルヘキシル、（メタ）アクリル酸ｎ−プロピル、（メタ）アクリル酸イソプロピル、（メタ）アクリル酸ブチル、（メタ）アクリル酸イソブチル、（メタ）アクリル酸メトキシメチル、（メタ）アクリル酸ｎ−プロポキシエチル、（メタ）アクリル酸ｉｓｏ−プロポキシエチル、（メタ）アクリル酸ｎ−ブトキシエチル、（メタ）アクリル酸ｉｓｏ−ブトキシエチル、（メタ）アクリル酸ｔｅｒｔ−ブトキシエチル、（メタ）アクリル酸２−ヒドロキシエチル、（メタ）アクリル酸３−ヒドロキシプロピル、（メタ）アクリル酸２−ヒドロキシ−ｎ−プロピル、（メタ）アクリル酸４−ヒドロキシ−ｎ−ブチル、（メタ）アクリル酸２−エトキシエチル、（メタ）アクリル酸１−エトキシエチル、（メタ）アクリル酸２,２,２−トリフルオロエチル、（メタ）アクリル酸２,２,３,３−テトラフルオロ−ｎ−プロピル、（メタ）アクリル酸２,２,３,３,３−ペンタフルオロ−ｎ−プロピル等の直鎖または分岐構造を持つ（メタ）アクリル酸エステル；α−（トリ）フルオロメチルアクリル酸メチル、α−（トリ）フルオロメチルアクリル酸エチル、α−（トリ）フルオロメチルアクリル酸２−エチルヘキシル、α−（トリ）フルオロメチルアクリル酸ｎ−プロピル、α−（トリ）フルオロメチルアクリル酸ｉｓｏ−プロピル、α−（トリ）フルオロメチルアクリル酸ｎ−ブチル、α−（トリ）フルオロメチルアクリル酸ｉｓｏ−ブチル、α−（トリ）フルオロメチルアクリル酸ｔ−ブチル、α−（トリ）フルオロメチルアクリル酸メトキシメチル、α−（トリ）フルオロメチルアクリル酸エトキシエチル、α−（トリ）フルオロメチルアクリル酸ｎ−プロポキシエチル、α−（トリ）フルオロメチルアクリル酸ｉｓｏ−プロポキシエチル、α−（トリ）フルオロメチルアクリル酸ｎ−ブトキシエチル、α−（トリ）フルオロメチルアクリル酸ｉｓｏ−ブトキシエチル、α−（トリ）フルオロメチルアクリル酸ｔ−ブトキシエチル等の直鎖または分岐構造を持つα−置換（メタ）アクリル酸エステル；スチレン、α−メチルスチレン、ビニルトルエン、ｐ−ヒドロキシスチレン、ｐ−ｔｅｒｔ−ブトキシカルボニルヒドロキシスチレン、３,５−ジ−ｔｅｒｔ−ブチル−４−ヒドロキシスチレン、３,５−ジメチル−４−ヒドロキシスチレン、ｐ−ｔｅｒｔ−ぺルフルオロブチルスチレン、ｐ−（２−ヒドロキシ−ｉｓｏ−プロピル）スチレン等の芳香族アルケニル化合物；アクリル酸、メタクリル酸、マレイン酸、無水マレイン酸、イタコン酸、無水イタコン酸等の不飽和カルボン酸及びカルボン酸無水物；エチレン、プロピレン、ノルボルネン、テトラフルオロエチレン、アクリルアミド、Ｎ−メチルアクリルアミド、Ｎ,Ｎ−ジメチルアクリルアミド、塩化ビニル、エチレン、フッ化ビニル、フッ化ビニリデン、テトラフルオロエチレン、ビニルピロリドン等が挙げられる。これらは、必要に応じて１種または２種以上を組み合わせて用いることができる。

Other copolymerizable monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and n-propyl (meth) acrylate. , Isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, methoxymethyl (meth) acrylate, n-propoxyethyl (meth) acrylate, iso-propoxyethyl (meth) acrylate, N-butoxyethyl (meth) acrylate, iso-butoxyethyl (meth) acrylate, tert-butoxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (Meth) acrylic acid 2-hydroxy-n-propyl, (meth) acrylic acid 4-hydro Ci-n-butyl, 2-ethoxyethyl (meth) acrylate, 1-ethoxyethyl (meth) acrylate, 2,2,2-trifluoroethyl (meth) acrylate, 2,2, (meth) acrylic acid (Meth) acrylic acid ester having a linear or branched structure such as 3,3-tetrafluoro-n-propyl and (meth) acrylic acid 2,2,3,3,3-pentafluoro-n-propyl; α- (Tri) methyl fluoromethyl acrylate, ethyl α- (tri) fluoromethyl acrylate, 2-ethylhexyl α- (tri) fluoromethyl acrylate, n-propyl α- (tri) fluoromethyl acrylate, α- (tri ) Iso-propyl fluoromethyl acrylate, n-butyl α- (tri) fluoromethyl acrylate, iso-butyl α- (tri) fluoromethyl acrylate, α- ( R) t-butyl fluoromethyl acrylate, methoxymethyl α- (tri) fluoromethyl acrylate, ethoxyethyl α- (tri) fluoromethyl acrylate, n-propoxyethyl α- (tri) fluoromethyl acrylate, α- (Tri) fluoromethyl acrylate iso-propoxyethyl, α- (tri) fluoromethyl acrylate n-butoxyethyl, α- (tri) fluoromethyl acrylate iso-butoxyethyl, α- (tri) fluoromethyl acrylate t Α-substituted (meth) acrylic acid ester having a linear or branched structure such as butoxyethyl; styrene, α-methylstyrene, vinyltoluene, p-hydroxystyrene, p-tert-butoxycarbonylhydroxystyrene, 3,5- Di-tert-butyl-4-hydroxystyrene Aromatic alkenyl compounds such as 3,5-dimethyl-4-hydroxystyrene, p-tert-perfluorobutylstyrene, p- (2-hydroxy-iso-propyl) styrene; acrylic acid, methacrylic acid, maleic acid, anhydrous Unsaturated carboxylic acids and carboxylic anhydrides such as maleic acid, itaconic acid, itaconic anhydride; ethylene, propylene, norbornene, tetrafluoroethylene, acrylamide, N-methylacrylamide, N, N-dimethylacrylamide, vinyl chloride, ethylene, Examples include vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, vinyl pyrrolidone and the like. These can be used alone or in combination of two or more as required.

  Other vinyl monomers can be used as long as the adhesion and dry etching resistance of the obtained (co) polymer are not significantly impaired. In general, it is preferable that the proportion of the structural unit formed by opening a double bond of a vinyl monomer is 20 mol% or less with respect to the entire (co) polymer.

  In polymerization using a polymerization initiator, a radical form of the polymerization initiator is generated in the reaction solution, and the chain polymerization of monomers proceeds from this radical form as a starting point. The polymerization initiator used for the production of the resist (co) polymer of the present invention is preferably one that generates radicals efficiently by heat. Examples of such a polymerization initiator include azo compounds such as 2,2′-azobisisobutyronitrile and dimethyl-2,2′-azobisisobutyrate; 2,5-dimethyl-2,5- And organic peroxides such as bis (tert-butylperoxy) hexane. Moreover, when manufacturing the (co) polymer for lithography using an ArF excimer laser (193 nm) light source, what does not have an aromatic ring in molecular structure is preferable so that light transmittance may not be reduced as much as possible. Furthermore, in consideration of safety during polymerization, the polymerization initiator preferably has a 10-hour half-life temperature of 60 ° C. or higher.

  A chain transfer agent may be used in producing the resist (co) polymer. When a chain transfer agent is used, there are advantages such that the amount of the polymerization initiator can be reduced when the low molecular weight (co) polymer is produced, and the molecular weight distribution of the (co) polymer can be reduced. is there. Suitable chain transfer agents include, for example, 1-butanethiol, 2-butanethiol, 1-octanethiol, 1-decanethiol, 1-tetradecanethiol, cyclohexanethiol, 2-methyl-1-propanethiol, 2-mercapto Examples include ethanol.

  In the polymerization reaction, a polymer having a radical at the growth end is generated in the reaction solution. However, when a chain transfer agent is used, the growth end radical collides with the chain transfer agent and the growth end is deactivated. Become. On the other hand, the chain transfer agent has a structure having a radical, and the radical body is the starting point, and the monomer is chain-polymerized again. Therefore, a chain transfer residue exists at the terminal of the obtained polymer. When producing a (co) polymer for lithography using an ArF excimer laser (193 nm) light source, a chain transfer agent having no aromatic ring should be used so as not to reduce the light transmittance of the (co) polymer as much as possible. preferable.

  The method for producing the polymer of the present invention is not particularly limited, but a polymerization method called drop polymerization, which is generally performed by solution polymerization and a monomer is dropped into a polymerization vessel, is preferable.

  Among them, from the viewpoint that a polymer having a narrow composition distribution and / or molecular weight distribution can be easily obtained, a monomer that becomes a constituent unit of a target polymer by polymerization (even if only a monomer is used, The polymer of the present invention is preferably produced by a polymerization method called dropping polymerization in which the polymerization is carried out while dropping the solution in an organic solvent.

  In the drop polymerization method, for example, an organic solvent is previously charged in a polymerization vessel and heated to a predetermined polymerization temperature, and then a monomer, a polymerization initiator, and a chain transfer agent dissolved in an organic solvent if necessary The body solution is dropped into the organic solvent in the polymerization vessel. The monomer may be dropped without being dissolved in the organic solvent. In that case, a solution in which the polymerization initiator and, if necessary, the chain transfer agent are dissolved in the monomer is dropped into the organic solvent. Further, the monomer may be dropped into the polymerization vessel without previously charging the organic solvent into the polymerization vessel.

  The polymerization temperature in the dropping polymerization method is not particularly limited, but is preferably in the range of 50 to 150 ° C.

  The organic solvent used in the dropping polymerization method is preferably a solvent that can dissolve both the monomer, the polymerization initiator, and the chain transfer agent when the chain transfer agent is used in combination. Examples of such an organic solvent include 1,4-dioxane, isopropyl alcohol, acetone, tetrahydrofuran (hereinafter also referred to as “THF”), methyl ethyl ketone (hereinafter also referred to as “MEK”), methyl isobutyl ketone (hereinafter referred to as “MIBK”). ), Γ-butyrolactone (hereinafter also referred to as “gBL”), propylene glycol monomethyl ether acetate (hereinafter also referred to as “PGMEA”), ethyl lactate, and the like.

  Although the density | concentration of the monomer solution dissolved in the organic solvent is not specifically limited, It is preferable to exist in the range of 5-50 mass%.

  In this dropping polymerization method, a part of the monomer may be charged in a polymerization vessel in advance. The part of each monomer is preferably in the range of 3 to 70% by mass with respect to the total amount of monomers used. Further, in this dropping polymerization method, depending on the polymerization rate and copolymerization reactivity ratio of each monomer, at least two types of monomer solutions having different monomer composition ratios may be continuously dropped. it can. That at least two or more types of monomer solutions are continuously dropped may start dropping the next-stage monomer solution before the previous-stage monomer solution is dropped into the polymerization vessel. The monomer solution of the next stage may start dropping immediately after the monomer solution is dropped into the polymerization vessel, or after the monomer solution of the previous stage is dropped into the polymerization vessel until the end of the polymerization. You may start dripping the monomer solution of the following step at arbitrary timings. In addition, monomers, initiators, and chain transfer agents, etc., may be added individually.

  The mass average molecular weight of the resist (co) polymer of the present invention is not particularly limited, but is preferably 1,000 or more, more preferably 5000 or more, and preferably 100,000 or less, More preferably, it is 20,000 or less.

Next, an example of a method for using the resist (co) polymer of the present invention will be described. The (co) polymer solution produced by a method such as solution polymerization is used as it is or in a good solvent such as 1,4-dioxane, acetone, THF, MEK, MIBA, gBL, PGMEA, and ethyl lactate as necessary. After dilution to an appropriate solution viscosity, the solution is dropped into a large amount of poor solvent such as methanol or water to precipitate the (co) polymer. This process is generally called reprecipitation, and may be unnecessary depending on circumstances, but is very effective for removing unreacted monomers remaining in the polymerization solution, polymerization initiators, and the like. If these unreacted substances remain as they are, there is a possibility of adversely affecting the resist performance. Therefore, it is preferable to remove them as much as possible. Thereafter, the precipitate may be filtered off and sufficiently dried, or may be used as it is without being dried.
The produced (co) polymer solution can be used as a resist composition as it is or after diluting with a suitable solvent. At that time, additives such as a storage stabilizer may be appropriately added.

  The resist composition of the present invention is obtained by dissolving the above-described resist (co) polymer of the present invention in a solvent. The chemically amplified resist composition of the present invention is obtained by dissolving the above-described (co) polymer for resist of the present invention and a photoacid generator in a solvent. The resist (co) polymer of the present invention may be used alone or in combination of two or more. In addition, without separating the (co) polymer from the (co) polymer solution obtained by solution polymerization or the like, the (co) polymer solution can be used as it is in the resist composition, or the (co) polymer can be used. The polymer solution can be diluted with an appropriate solvent and used in a resist composition.

  In the resist composition of the present invention, the solvent for dissolving the resist polymer of the present invention is arbitrarily selected according to the purpose, but the selection of the solvent is for reasons other than the solubility of the resin, for example, the uniformity of the coating film. In addition, there may be restrictions from the appearance or safety.

Solvents usually used in the present invention include MEK, MIBK, 2-pentanone, 2-hexanone and other linear or branched ketones, cyclopentanone, cyclohexanone and other cyclic ketones, PGMEA, propylene glycol monoethyl ether Propylene glycol monoalkyl acetates such as acetate, ethylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate, propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, etc. Ethylene glycol monoalkyl ethers, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether Such as diethylene glycol alkyl ethers, esters such as ethyl acetate and ethyl lactate, alcohols such as n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tert-butyl alcohol, cyclohexanol and 1-octanol , 1,4-dioxane, ethylene carbonate, gBL and the like. These solvents may be used alone or in combination of two or more.
The amount of the solvent used is usually 200 parts by mass or more and more preferably 300 parts by mass or more with respect to 100 parts by mass of the resist polymer (the (co) polymer of the present invention). Moreover, the usage-amount of a solvent is 5000 mass parts or less with respect to 100 mass parts of resist polymers ((co) polymer of this invention) normally, and it is more preferable that it is 2000 mass parts or less.

  When the (co) polymer for resist of the present invention is used for a chemically amplified resist, it is necessary to use a photoacid generator. Examples of such a photoacid generator include onium salt compounds, sulfonimide compounds, sulfone compounds, sulfonic acid ester compounds, quinonediazide compounds, and diazomethane compounds. Among them, onium salt compounds such as sulfonium salt, iodonium salt, phosphonium salt, diazonium salt, pyridinium salt are suitable, specifically, triphenylsulfonium triflate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium naphthalene sulfonate, (Hydroxyphenyl) benzylmethylsulfonium toluenesulfonate, diphenyliodonium triflate, diphenyliodonium pyrenesulfonate, diphenyliodonium dodecylbenzenesulfonate, diphenyliodonium hexafluoroantimonate and the like.

  A photo-acid generator can be used individually or in mixture of 2 or more types. The amount of photoacid generator used is conveniently selected according to the type of photoacid generator selected, but is usually 0.1 to 20 parts by weight, preferably 0.5 to 10 parts per 100 parts by weight of the (co) polymer. Part by mass. By making the usage-amount of a photo-acid generator into this range, the chemical reaction by the catalytic action of the acid generated by exposure can be sufficiently caused. When the amount of the photoacid generator used is less than this amount, the chemical reaction due to the catalytic action of the acid generated by exposure cannot be sufficiently caused, and when the amount is large, the stability of the resist composition is lowered, The occurrence of uneven coating during coating and scum during development increases.

  Furthermore, various additives such as surfactants, quenchers, sensitizers, antihalation agents, storage stabilizers, antifoaming agents, and the like can be blended with the resist composition of the present invention as necessary. The types and blending amounts of these additives are not particularly limited and may be determined as appropriate.

Next, an example of the pattern forming method of the present invention will be described.
First, the resist composition of the present invention is applied to the surface of a substrate to be processed such as a silicon wafer on which a pattern is formed by spin coating or the like. And the to-be-processed board | substrate with which this chemically amplified resist composition was apply | coated is dried by baking process (prebaking) etc., and a resist film is formed on a board | substrate.
Next, the resist film thus obtained is irradiated with light having a wavelength of 250 nm or less through a photomask (exposure). The light used for exposure is preferably a KrF excimer laser or an ArF excimer laser, and particularly preferably an ArF excimer laser.
After light irradiation (exposure), heat treatment (post-exposure baking, PEB) is appropriately performed, the substrate is immersed in an alkaline developer, and the exposed portion is dissolved and removed in the developer (development). Any known alkaline developer may be used. Then, after development, the substrate is appropriately rinsed with pure water or the like. In this way, a resist pattern is formed on the substrate to be processed.
Usually, a substrate to be processed on which a resist pattern is formed is appropriately heat-treated (post-baked) to strengthen the resist, and a portion without the resist is selectively etched. After etching, the resist is usually removed using a release agent.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In addition, “part” in each example and comparative example means “part by mass” unless otherwise specified.
Moreover, the physical property etc. of the polymer manufactured as follows were measured.

<Mass average molecular weight of resist polymer>
About 20 mg of the resist polymer is dissolved in 5 mL of THF, and filtered through a 0.5 μm membrane filter to prepare a sample solution. This sample solution is measured using gel permeation chromatography (GPC) manufactured by Tosoh. did. For this measurement, a separation column was manufactured by Showa Denko Co., Ltd., Shodex GPC K-805L (trade name) in series, the solvent was THF, the flow rate was 1.0 mL / min, the detector was a differential refractometer, measurement Measurements were made using polystyrene as the standard polymer at a temperature of 40 ° C. and an injection volume of 0.1 mL.

<Average copolymer composition ratio of resist polymer (mol%)>
^It calculated | required by the measurement of < ¹ > H-NMR. This measurement is performed using JSX Corporation GSX-400 type FT-NMR (trade name), deuterated chloroform, deuterated acetone or deuterated about 5 mass% resist polymer sample. The dimethyl sulfoxide solution was put in a test tube having a diameter of 5 mmφ, and the measurement was carried out 64 times in a single pulse mode at a measurement temperature of 40 ° C., an observation frequency of 400 MHz.
Moreover, using the produced polymer, a resist composition was prepared as follows, and its physical properties and the like were measured.

<Preparation of resist composition>
100 parts of the produced resist polymer, 2 parts of triphenylsulfonium triflate as a photoacid generator, and 700 parts of PGMEA as a solvent are mixed to obtain a uniform solution, and then filtered through a membrane filter having a pore size of 0.1 μm. Then, a resist composition solution was prepared.
<Formation of resist pattern>
The prepared resist composition solution was spin-coated on a silicon wafer, and prebaked at 120 ° C. for 60 seconds using a hot plate to form a resist film having a thickness of 0.4 μm. Next, after exposure using an ArF excimer laser exposure machine (wavelength: 193 nm), post-exposure baking was performed using a hot plate at 120 ° C. for 60 seconds. Subsequently, development was performed at room temperature using a 2.38 mass% tetramethylammonium hydroxide aqueous solution, washed with pure water, and dried to form a resist pattern.
<Sensitivity>
The minimum exposure (mJ / cm ² ) for forming a 0.16 μm line and space (L / S = 1/1) with a line width of 1/1 was measured as sensitivity.
<Resolution>
The minimum dimension (μm) of the resist pattern resolved when exposed at the exposure amount was defined as the resolution.
<Line edge roughness>
JSM-6340F field emission scanning electron microscope manufactured by JEOL Ltd. for the range of 5 μm on the side edge in the longitudinal direction of the 0.20 μm resist pattern obtained by the minimum exposure amount reproducing the 0.20 μm resist pattern on the mask Based on (product name), the distance from the reference line where the pattern side edge should be was measured at 50 points, and the standard deviation was obtained to calculate 3σ. A smaller value indicates better performance.
<Resist pattern rectangularity>
The vertical cross section of the 0.20 μm resist pattern was observed with a JSM-6340F field emission scanning electron microscope (trade name) manufactured by JEOL, and the cross-sectional shape was rectangular. Evaluate as “○” when the “beard” does not exist on the ground contact surface, and as a rectangle, but as “△” when the “beard” exists on the ground contact surface with the substrate, and “×” when it is convex or concave. did.
<Amount of microgel>
For the prepared resist composition solution, the number of microgels in the solution immediately after preparation (initial value of microgel) and the number of microgels in the solution after standing at 4 ° C. for 1 week (the number of microgels after aging) The number was measured with a particle counter made by Rion. Then, together with the initial value of the microgel, the number of increased microgels calculated by (number of microgels after time) − (initial value of microgel) was evaluated.
Here, the number of microgels having a particle size of 0.25 μm or more present in 1 mL of the resist composition solution was measured.

<Example 1>
Under a nitrogen atmosphere, 35.1 parts of PGMEA and 8.8 parts of gBL were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 22.8 parts of a mixture of monomers represented by the following formulas (20-1) and (20-2) (hereinafter referred to as M-1);

下記式（２１）で表される２−メタクリロイルオキシ−２−エチルアダマンタン（以下、ＥＡｄＭＡと言う。）２１.３部、

21.3 parts of 2-methacryloyloxy-2-ethyladamantane (hereinafter referred to as EAdMA) represented by the following formula (21);

下記式（２２）で表される１−メタクリロイルオキシ−３−ヒドロキシアダマンタン（以下、ＨＡｄＭＡと言う。）８.５部、

8.5 parts of 1-methacryloyloxy-3-hydroxyadamantane (hereinafter referred to as HAdMA) represented by the following formula (22);

ＰＧＭＥＡ６３.１部、ｇＢＬ１５.８部および２,２’−アゾビスイソブチロニトリル（以下、ＡＩＢＮと言う。）１.９７部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。次いで、得られた反応溶液を約３０倍量のメタノール中に攪拌しながら滴下し、白色の析出物の沈殿を得た。沈殿物に残存する単量体を取り除くために、得られた沈殿を濾別し、重合に使用した単量体に対して約３０倍量のメタノール中で沈殿を洗浄した。そして、この沈殿を濾別し、減圧下５０℃で約４０時間乾燥して共重合体Ａ−１を得た。
得られた共重合体Ａ−１の各物性を測定した結果を表１に示す。

A monomer solution in which 63.1 parts of PGMEA, 15.8 parts of gBL and 1.97 parts of 2,2′-azobisisobutyronitrile (hereinafter referred to as AIBN) were mixed at a constant speed using a dropping device. The solution was dropped into the flask over 6 hours, and then kept at 80 ° C. for 1 hour. Next, the obtained reaction solution was added dropwise to about 30 times amount of methanol with stirring to obtain a white precipitate. In order to remove the monomer remaining in the precipitate, the obtained precipitate was separated by filtration, and the precipitate was washed in about 30 times as much methanol as the monomer used for the polymerization. And this precipitation was separated by filtration and it dried at 50 degreeC under pressure reduction for about 40 hours, and obtained copolymer A-1.
Table 1 shows the results of measurement of physical properties of the obtained copolymer A-1.

<Example 2>
Under a nitrogen atmosphere, 45.3 parts of THF was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 70 ° C. while stirring. 27.5 parts of a mixture of monomers represented by the following formulas (23-1) and (23-2) (hereinafter referred to as M-2);

ＥＡｄＭＡ１７.４部、ＨＡｄＭＡ９.４部、ＴＨＦ８１.５部、ＡＩＢＮ０.９８部およびｎ−オクチルメルカプタン０.２２部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、７０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ａ−２を得た。
得られた共重合体Ａ−２の各物性を測定した結果を表１に示す。

A monomer solution prepared by mixing 17.4 parts of EAdMA, 9.4 parts of HAdMA, 81.5 parts of THF, 0.98 part of AIBN and 0.22 part of n-octyl mercaptan was added to a flask at a constant rate for 6 hours. The solution was added dropwise, and then kept at 70 ° C. for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer A-2.
Table 1 shows the results obtained by measuring the physical properties of the obtained copolymer A-2.

<Example 3>
Under a nitrogen atmosphere, 40.0 parts of PGMEA was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 22.8 parts of M-1 and 15.3 parts of 1-methacryloyloxy-1-cyanomethylcyclohexane (hereinafter referred to as CMCHMA) represented by the following formula (40).

ＰＧＭＥＡ７２.１部、ＡＩＢＮ０.６６部およびｎ−オクチルメルカプタン０.０６部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ａ−３を得た。
得られた共重合体Ａ−３の各物性を測定した結果を表１に示す。

A monomer solution in which 72.1 parts of PGMEA, 0.66 parts of AIBN and 0.06 parts of n-octyl mercaptan were mixed was dropped into the flask at a constant rate over 6 hours using a dropping device, and then at 80 ° C. Hold for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer A-3.
Table 1 shows the results obtained by measuring the physical properties of the obtained copolymer A-3.

<Example 4>
Under a nitrogen atmosphere, 44.9 parts of MIBK was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. A monomer solution prepared by mixing 28.2 parts of M-2, 20.3 parts of EAdMA, 5.4 parts of CMCHMA, 80.8 parts of MIBK, and 1.64 parts of AIBN was added to a flask at a constant speed for 6 hours. The solution was added dropwise, and then kept at 80 ° C. for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer A-4.
Table 1 shows the results obtained by measuring the physical properties of the obtained copolymer A-4.

<Comparative Example 1>
Under a nitrogen atmosphere, 31.5 parts of PGMEA and 7.9 parts of gBL were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 16.9 parts of 2-exo-methacryloyloxy-4-oxatricyclo [4.2.1.0 ^3,7 ] nonan-5-one represented by the following formula (24) (hereinafter referred to as NLMA) ,

ＥＡｄＭＡ２２.３部、ＨＡｄＭＡ８.０部、ＰＧＭＥＡ５６.７部、ｇＢＬ１４.２部およびＡＩＢＮ１.９７部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ｂ−１を得た。
得られた共重合体Ｂ−１の各物性を測定した結果を表１に示す。

A monomer solution obtained by mixing 22.3 parts of EAdMA, 8.0 parts of HAdMA, 56.7 parts of PGMEA, 14.2 parts of gBL and 1.97 parts of AIBN was dropped into the flask at a constant rate over 6 hours using a dropping device. Then, it was kept at 80 ° C. for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer B-1.
Table 1 shows the results obtained by measuring the physical properties of the obtained copolymer B-1.

<Comparative example 2>
Under a nitrogen atmosphere, 45.3 parts of THF was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 70 ° C. while stirring. 8- or 9-acryloyloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decan-3-one represented by the following formula (25) (hereinafter referred to as OTDA) 27.5 Part,

ＥＡｄＭＡ１７.４部、ＨＡｄＭＡ９.４部、ＴＨＦ８１.５部、ＡＩＢＮ０.９８部およびｎ−オクチルメルカプタン０.２２部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、７０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ｂ−２を得た。
得られた共重合体Ｂ−２の各物性を測定した結果を表１に示す。

A monomer solution prepared by mixing 17.4 parts of EAdMA, 9.4 parts of HAdMA, 81.5 parts of THF, 0.98 part of AIBN and 0.22 part of n-octyl mercaptan was added to a flask at a constant rate for 6 hours. The solution was added dropwise, and then kept at 70 ° C. for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer B-2.
Table 1 shows the results of measurement of physical properties of the obtained copolymer B-2.

Resist compositions (Examples 1 to 4) using the polymer of the present invention had sufficient sensitivity and resolution, and produced less microgel in the resist solution.
On the other hand, in the resist composition using the polymers of Comparative Examples 1 and 2, many microgels were confirmed in the resist solution.

<Example 5>
Under a nitrogen atmosphere, 47.0 parts of PGMEA was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 37.6 parts of a mixture of monomers represented by the following formulas (26-1) and (26-2) (hereinafter referred to as M-3);

ＥＡｄＭＡ１８.９部、ＰＧＭＥＡ８４.６部およびＡＩＢＮ１.８０部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ａ−５を得た。
得られた共重合体Ａ−５の各物性を測定した結果を表２に示す。

A monomer solution in which 18.9 parts of EAdMA, 84.6 parts of PGMEA and 1.80 parts of AIBN were mixed was dropped into the flask at a constant rate over 6 hours using a dropping device, and then kept at 80 ° C. for 1 hour. . Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer A-5.
Table 2 shows the results of measurements of physical properties of the obtained copolymer A-5.

<Example 6>
Under a nitrogen atmosphere, 33.7 parts of PGMEA and 14.5 parts of gBL were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 32.0 parts of a mixture of monomers represented by the following formulas (27-1) and (27-2) (hereinafter referred to as M-4);

下記式（２８）で表される２−メタクリロイルオキシ−２−メチルアダマンタン（以下、ＭＡｄＭＡと言う。）２５.７部、

25.7 parts 2-methacryloyloxy-2-methyladamantane (hereinafter referred to as MAdMA) represented by the following formula (28);

ＰＧＭＥＡ６０.７部、ｇＢＬ２６.０部およびジメチル−２,２’−アゾビスイソブチレート（以下、ＤＡＩＢと言う。）１.７３部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ａ−６を得た。
得られた共重合体Ａ−６の各物性を測定した結果を表２に示す。

A monomer solution in which 60.7 parts of PGMEA, 26.0 parts of gBL and 1.73 parts of dimethyl-2,2′-azobisisobutyrate (hereinafter referred to as DAIB) were mixed was added at a constant speed using a dropping device. Was dropped into the flask over 6 hours, and then kept at 80 ° C. for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer A-6.
Table 2 shows a result obtained by measuring physical properties of the obtained copolymer A-6.

<Comparative Example 3>
Under a nitrogen atmosphere, 37.1 parts of PGMEA was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 26.6 parts of 2-exo-acryloyloxy-4-oxatricyclo [4.2.1.0 ^3,7 ] nonan-5-one (hereinafter referred to as NLA) represented by the following formula (29) ,

ＥＡｄＭＡ１７.９部、ＰＧＭＥＡ６６.７部およびＡＩＢＮ１.８０部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ｂ−３を得た。
得られた共重合体Ｂ−３の各物性を測定した結果を表２に示す。

A monomer solution in which 17.9 parts of EAdMA, 66.7 parts of PGMEA and 1.80 parts of AIBN were mixed was dropped into the flask at a constant rate over 6 hours using a dropping device, and then kept at 80 ° C. for 1 hour. . Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer B-3.
Table 2 shows the results of measurement of physical properties of the obtained copolymer B-3.

<Comparative example 4>
Under a nitrogen atmosphere, 26.8 parts of PGMEA and 11.5 parts of gBL were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 2-exo-methacryloyloxy-4,8-dioxatricyclo [4.2.1.0 ^3,7 ] nonan-5-one represented by the following formula (30) (hereinafter referred to as ONLMA) 21 .1 part

ＭＡｄＭＡ２４.８部、ＰＧＭＥＡ４８.２部、ｇＢＬ２０.６部およびＤＡＩＢ１.７３部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ｂ−４を得た。
得られた共重合体Ｂ−４の各物性を測定した結果を表２に示す。

A monomer solution obtained by mixing 24.8 parts of MAdMA, 48.2 parts of PGMEA, 20.6 parts of gBL and 1.73 parts of DAIB was dropped into the flask at a constant rate over 6 hours using a dropping device, and then 80 ° C. Held for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer B-4.
Table 2 shows the results of measurement of physical properties of the obtained copolymer B-4.

The resist composition using the polymer of the present invention (Examples 5 and 6) has sufficient sensitivity and resolution, has an excellent resist pattern rectangularity, and is excellent in terms of line edge roughness, Moreover, there was little production | generation of the microgel in a resist solution.
On the other hand, the resist compositions using the polymers of Comparative Examples 3 and 4 were inferior in terms of line edge roughness and resist pattern rectangularity, and many microgel formations were confirmed in the resist solution.

<Example 7>
Under a nitrogen atmosphere, 54.3 parts of MEK was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 75 ° C. while stirring. 47.0 parts of a mixture of monomers represented by the following formulas (31-1) and (31-2) (hereinafter referred to as M-5),

ＭＡｄＭＡ７.０部、下記式（３２）で表される１−アクリロイルオキシ−３−ヒドロキシアダマンタン（以下、ＨＡｄＡと言う。）１１.１部、

MAdMA 7.0 parts, 1-acryloyloxy-3-hydroxyadamantane (hereinafter referred to as HAdA) 11.1 parts represented by the following formula (32),

ＭＥＫ９７.７部、ＡＩＢＮ０.８２部およびｎ−オクチルメルカプタン０.２９部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、７５℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ａ−７を得た。
得られた共重合体Ａ−７の各物性を測定した結果を表３に示す。

A monomer solution obtained by mixing 97.7 parts of MEK, 0.82 parts of AIBN and 0.29 parts of n-octyl mercaptan was dropped into the flask at a constant rate over 6 hours using a dropping device, and then at 75 ° C. Hold for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer A-7.
Table 3 shows the results of measurement of physical properties of the obtained copolymer A-7.

<Example 8>
Under a nitrogen atmosphere, 51.0 parts of PGMEA and 5.7 parts of gBL were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. A mixture of monomers represented by the following formulas (33-1) and (33-2) (hereinafter referred to as M-6) 55.7 parts,

ＥＡｄＭＡ５.５部、下記式（３４）で表される２−または３−シアノ−５−ノルボルニルアクリレート（以下、ＣＮＮＡと言う。）６.９部、

5.5 parts of EAdMA, 6.9 parts of 2- or 3-cyano-5-norbornyl acrylate (hereinafter referred to as CNNA) represented by the following formula (34),

ＰＧＭＥＡ９１.８部、ｇＢＬ１０.２部、ＤＡＩＢ１.７３部および２−メルカプトエタノール０.０８部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ａ−８を得た。
得られた共重合体Ａ−８の各物性を測定した結果を表３に示す。

A monomer solution prepared by mixing 91.8 parts of PGMEA, 10.2 parts of gBL, 1.73 parts of DAIB and 0.08 part of 2-mercaptoethanol was dropped into the flask at a constant rate over 6 hours using a dropping device. Then, it hold | maintained at 80 degreeC for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer A-8.
Table 3 shows the results of measurements of physical properties of the obtained copolymer A-8.

<Example 9>
Under a nitrogen atmosphere, 47.8 parts of PGMEA and 12.0 parts of gBL were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 60.2 parts of a mixture of monomers represented by the following formulas (35-1) and (35-2) (hereinafter referred to as M-7),

下記式（３６）で表される２−または３−シアノ−５−ノルボルニルメタクリレート（以下、ＣＮＮＭＡと言う。）１１.５部、

11.5 parts of 2- or 3-cyano-5-norbornyl methacrylate (hereinafter referred to as CNNNMA) represented by the following formula (36);

ＰＧＭＥＡ８６.０部、ｇＢＬ２１.５部およびＡＩＢＮ１.９７部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ａ−９を得た。
得られた共重合体Ａ−９の各物性を測定した結果を表３に示す。

A monomer solution in which 86.0 parts of PGMEA, 21.5 parts of gBL and 1.97 parts of AIBN were mixed was dropped into the flask over 6 hours at a constant rate using a dropping device, and then kept at 80 ° C. for 1 hour. . Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer A-9.
Table 3 shows the results of measurements of physical properties of the obtained copolymer A-9.

<Example 10>
Under a nitrogen atmosphere, 54.2 parts of MEK was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 75 ° C. while stirring. A mixture of monomers represented by the following formulas (37-1) and (37-2) (hereinafter referred to as M-8) 43.7 parts,

ＨＡｄＡ２１.３部、ＭＥＫ９７.５部およびＡＩＢＮ２.３０部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、７５℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ａ−１０を得た。
得られた共重合体Ａ−１０の各物性を測定した結果を表３に示す。

A monomer solution in which 21.3 parts of HAdA, 97.5 parts of MEK and 2.30 parts of AIBN were mixed was dropped into the flask over 6 hours at a constant rate using a dropping device, and then kept at 75 ° C. for 1 hour. . Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer A-10.
Table 3 shows the results of measurement of physical properties of the obtained copolymer A-10.

<Comparative Example 5>
Under a nitrogen atmosphere, 47.0 parts of MEK was placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 75 ° C. while stirring. 37.4 parts of a monomer represented by the following formula (31-1) (hereinafter referred to as TBNLMA),

ＭＡｄＭＡ８.０部、ＨＡｄＡ１１.１部、ＭＥＫ８４.６部、ＡＩＢＮ０.８２部およびｎ−オクチルメルカプタン０.２９部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、７５℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ｂ−５を得た。
得られた共重合体Ｂ−５の各物性を測定した結果を表３に示す。

A monomer solution prepared by mixing 8.0 parts of MAdMA, 11.1 parts of HAdA, 84.6 parts of MEK, 0.82 parts of AIBN and 0.29 parts of n-octyl mercaptan was added to a flask at a constant speed for 6 hours. The solution was added dropwise, and then kept at 75 ° C. for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer B-5.
Table 3 shows the results of measurement of physical properties of the obtained copolymer B-5.

<Comparative Example 6>
Under a nitrogen atmosphere, 40.7 parts of PGMEA and 10.1 parts of gBL were placed in a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. 48.7 parts of a monomer represented by the following formula (39) (hereinafter referred to as CHNLA),

ＣＮＮＭＡ１２.３部、ＰＧＭＥＡ７３.２部、ｇＢＬ１８.３部およびＡＩＢＮ１.９７部を混合した単量体溶液を、滴下装置を用い、一定速度で６時間かけてフラスコ中へ滴下し、その後、８０℃で１時間保持した。以降の操作は実施例１と同様にして共重合体Ｂ−６を得た。
得られた共重合体Ｂ−６の各物性を測定した結果を表３に示す。

A monomer solution in which 12.3 parts of CNNMA, 73.2 parts of PGMEA, 18.3 parts of gBL and 1.97 parts of AIBN were mixed was dropped into the flask at a constant rate over 6 hours using a dropping device, and then 80 ° C. Held for 1 hour. Thereafter, the same operations as in Example 1 were carried out, so as to obtain a copolymer B-6.
Table 3 shows the results of measurement of physical properties of the obtained copolymer B-6.

The resist composition (Examples 7 to 10) using the polymer of the present invention has sufficient sensitivity and resolution, is excellent in line edge roughness, and also produces a microgel in the resist solution. There were few.
On the other hand, the resist compositions using the polymers of Comparative Examples 5 and 6 were inferior in line edge roughness, and many microgel formations were confirmed in the resist solution.

Claims (13)

A (co) polymer having a structural unit represented by the following formula (1).

(In the formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ^{2 to} R ⁵ are each independently a hydrogen atom, —R ⁷ —CN, —R ⁸ —CH (CN) ₂ , —R ^9. —COO—R ¹⁰ , — (CH ₃ ) _m —C (CF ₃ ) ₂ —OH is represented, and R ⁶ is a hydrogen atom, an alkoxy group optionally having 1 to 3 carbon atoms, A cyano group or an ester group having 1 to 6 carbon atoms, R ² or R ³ and R ⁴ or R ⁵ , or R ² or R ³ and R ⁶ , or R ⁴ or R ⁵ And R ⁶ together represent —COO— (CH ₂ ) _n —, where n represents an integer of 0 to _3. R ^{7 to} R ⁹ each independently has 1 to 4 carbon atoms. R ¹⁰ represents an acid-eliminable group, one of which is a methyl group and the other is an isopropyl group M represents an integer of 0 to 6) A (co) polymer having a structural unit represented by the following formula (1-a).

(In formula (1-a), R ^{1 to} R ⁴ , X and Y have the same meanings as in formula (1).) The (co) polymer according to claim 2, wherein R ^{2 to} R ⁴ are hydrogen atoms. The (co) polymer according to claim 2, wherein any one of R ^{2 to} R ⁴ is a cyano group and the other is a hydrogen atom. The (co) polymer according to claim 2, wherein any one of R ^{2 to} R ⁴ is a dicyanomethyl group and the other is a hydrogen atom. A (co) polymer having a structural unit represented by the following formula (1-b).

(In formula (1-b), R ¹ , X, Y and R ⁶ have the same meanings as in formula (1).)   The (co) polymer according to any one of claims 1 to 6, wherein the mass average molecular weight is 1,000 to 100,000.   The (co) polymerization is carried out while the (co) polymerization is carried out while dropping the monomer that becomes the constituent unit of the (co) polymer of the present invention into the polymerization vessel. Co) polymer production method.   A resist composition comprising at least one of the (co) polymers according to claim 1.   A chemically amplified resist composition comprising at least one of the (co) polymer according to claim 1 and a photoacid generator.   A pattern comprising a step of applying the resist composition according to any one of claims 9 and 10 onto a substrate to be processed, a step of exposing with light having a wavelength of 250 nm or less, and a step of developing using a developer. Forming method.   12. The pattern forming method according to claim 11, wherein the light used for exposure is an ArF excimer laser.   A pattern forming method including a step of applying the resist composition according to any one of claims 9 and 10 onto a substrate to be processed, a step of exposing with an electron beam, and a step of developing using a developer.