JP2018063337A - Method for forming resist pattern and pattern-thickening polymer composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a material allowing formation of a finer pattern into a good shape.SOLUTION: A method for forming a resist pattern is provided, which includes: a step of forming a resist pre-pattern 2 having a polar group exposed on a surface 2a, on a support body 1; a step of forming a polymer film 3 by applying a pattern-thickening polymer composition on the support body 1 where the resist pre-pattern 2 is formed, so as to cover the resist pre-pattern 2; a step of forming a developer-insoluble layer 3a on the surface 2a; and a step of thickening the resist pre-pattern 2 to form a resist pattern 4 by developing the resist pre-pattern 2 with the developer-insoluble layer 3a formed thereon and the polymer film 3 covering the pre-pattern. The pattern-thickening polymer composition comprises a copolymer having specific first to third structural units or specific fourth and fifth structural units.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a resist pattern forming method and a polymer composition for pattern thickening.

In lithography technology, for example, a resist film made of a resist material is formed on a substrate, and the resist film is selectively irradiated with radiation such as light or an electron beam through a mask on which a predetermined pattern is formed. A step of forming a resist pattern having a predetermined shape on the resist film is performed by performing exposure and developing.
A resist material in which the exposed portion changes to a property that dissolves in the developer is referred to as a positive type, and a resist material that changes to a property in which the exposed portion does not dissolve in the developer is referred to as a negative type.

In the manufacture of semiconductor elements and liquid crystal display elements, pattern miniaturization is progressing due to advances in lithography technology.
As a pattern miniaturization technique, generally, the exposure light source has a shorter wavelength (higher energy). Specifically, conventionally, ultraviolet rays typified by g-line and i-line have been used, but at present, semiconductor devices using a KrF excimer laser or an ArF excimer laser are mass-produced. Further, studies have been made on electron beams having shorter wavelengths (higher energy) than these excimer lasers, EUV (extreme ultraviolet rays), X-rays, and the like.

Along with the shortening of the wavelength of the exposure light source, the resist material is required to improve lithography characteristics such as sensitivity to the exposure light source and resolution capable of reproducing a fine pattern. A chemically amplified resist composition is known as a resist material that satisfies such requirements.
As the chemically amplified resist composition, generally, a resist composition containing a base material component whose solubility in a developing solution is changed by the action of an acid and an acid generator component that generates an acid upon exposure is used. Yes. For example, when the developer is an alkali developer (alkaline development process), a substrate component that has increased solubility in an alkali developer due to the action of an acid is used.

  A positive development process that combines a positive chemically amplified resist composition, that is, a chemically amplified resist composition whose solubility in an alkali developer increases upon exposure, and an alkaline developer is a negative chemically amplified type. Compared to a negative development process in which a resist composition and an alkali developer are combined, there are advantages such as a simple photomask structure and excellent pattern characteristics. Therefore, at present, a positive development process in which a positive chemically amplified resist composition and an alkali developer are combined is mainly used for forming a fine pattern.

When the positive development process is applied, when the resist film obtained by applying the chemically amplified resist composition on the support is selectively exposed, the exposed portion of the resist film is decomposed by acid in the base resin. Since the functional group is decomposed by the action of the acid generated from the acid generator and the like, and is changed from poorly soluble to soluble in an alkali developer, the unexposed portion of the resist film remains hardly soluble in alkali and remains unchanged. By developing with a developing solution, a dissolution contrast can be provided between the exposed and unexposed areas, and a positive resist pattern can be formed.
However, applying the positive development process to form a fine pattern (dense pattern, trench pattern, etc.) results in a region with low optical intensity, particularly in the film thickness direction, in the exposed portion of the resist film. In addition, the resolution of the resist pattern is likely to deteriorate.

For forming a fine pattern as described above, a method in which a region having a low optical intensity is selectively dissolved and removed to form a resist pattern (negative resist pattern) is useful. As a method for forming a negative resist pattern using a chemically amplified resist composition used in the mainstream positive development process, a negative development process combined with a developer containing an organic solvent (organic developer). Is known (see, for example, Patent Document 1).
When the negative development process is applied, when the resist film obtained by applying the chemically amplified resist composition on the support is selectively exposed, the exposed portion of the resist film is decomposed by acid in the base resin. The functional group is decomposed by the action of an acid generated from an acid generator and the like, and it changes from being soluble to hardly soluble in an organic developer, while the unexposed portion of the resist film remains soluble and does not change. By developing with a developer, it is possible to provide a dissolution contrast between the exposed portion and the unexposed portion, and a negative resist pattern in which the exposed portion remains as a pattern can be formed.

JP 2013-178515 A

In recent years, further advancement of lithography technology, expansion of application fields, and the like have progressed, and pattern miniaturization is rapidly progressing. Among these, when manufacturing a semiconductor element etc., the technique which can form the fine pattern in which a dimension is less than 100 nm with a favorable shape is required.
This invention is made | formed in view of the said situation, and makes it a subject to provide the resist pattern formation method which can form a finer pattern with a favorable shape, and the polymer composition for pattern thickening used for this. .

  A first aspect of the present invention is a method of forming a resist pattern having a thickened resist prepattern, the step A of forming a resist prepattern having a polar group exposed on the surface on a support, On the support on which the resist prepattern is formed, a pattern thickening polymer composition is applied to form a polymer film on the support on which the resist prepattern is formed, and on the surface of the resist prepattern Step C for forming a developer-insoluble layer, a resist prepattern having the developer-insoluble layer formed on the surface thereof, and a resist pattern in which the resist film is thickened by developing the polymer film covering the resist prepattern And a step D of forming a resist pattern.

In the resist pattern forming method of the first embodiment, a pattern thickening polymer composition containing a copolymer having a first structural unit, a second structural unit, and a third structural unit is used. The first structural unit is a structural unit having a thickening function of the resist prepattern, and the second structural unit and the third structural unit satisfy the following formula (α): To do.
Glass transition temperature (Tg ₂ ) <Glass transition temperature (Tg ₃ ) (α)
Tg ₂ : Glass transition temperature of homopolymer consisting of repeating structure of the second structural unit Tg ₃ : Glass transition temperature of homopolymer consisting of repeating structure of the third structural unit

  In the resist pattern forming method of the second embodiment, a pattern thickening polymer composition containing a copolymer having a fourth structural unit and a fifth structural unit is used. The fourth structural unit is a structural unit having a thickening function of the resist pre-pattern, and the fifth structural unit has a glass transition temperature of a homopolymer having a repeating structure of less than 109 ° C. It is characterized by.

  The second aspect of the present invention is a pattern thickening polymer composition used for thickening a resist prepattern having a polar group exposed on the surface.

The polymer composition for pattern thickening according to the first embodiment contains a copolymer having a first structural unit, a second structural unit, and a third structural unit. The first structural unit is a structural unit having a thickening function of the resist prepattern, and the second structural unit and the third structural unit satisfy the following formula (α): To do.
Glass transition temperature (Tg ₂ ) <Glass transition temperature (Tg ₃ ) (α)
Tg ₂ : Glass transition temperature of homopolymer consisting of repeating structure of the second structural unit Tg ₃ : Glass transition temperature of homopolymer consisting of repeating structure of the third structural unit

The polymer composition for pattern thickening according to the second embodiment contains a copolymer having a fourth structural unit and a fifth structural unit.
The fourth structural unit is a structural unit having a thickening function of the resist pre-pattern, and the fifth structural unit has a glass transition temperature of a homopolymer having a repeating structure of less than 109 ° C. It is characterized by.

  ADVANTAGE OF THE INVENTION According to this invention, the resist pattern formation method which can form a finer pattern with a favorable shape, and the polymer composition for pattern thickening used for this can be provided.

It is a schematic process drawing explaining one Embodiment of the resist pattern formation method.

In the present specification and claims, “aliphatic” is a relative concept with respect to aromatics, and is defined to mean groups, compounds, etc. that do not have aromaticity.
Unless otherwise specified, the “alkyl group” includes linear, branched and cyclic monovalent saturated hydrocarbon groups.
The “alkylene group” includes linear, branched, and cyclic divalent saturated hydrocarbon groups unless otherwise specified. The same applies to the alkyl group in the alkoxy group.
The “halogenated alkyl group” is a group in which part or all of the hydrogen atoms of the alkyl group are substituted with a halogen atom, and examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
“Fluorinated alkyl group” or “fluorinated alkylene group” refers to a group in which part or all of the hydrogen atoms of an alkyl group or alkylene group are substituted with fluorine atoms.
“Structural unit” means a monomer unit (monomer unit) constituting a polymer compound (resin, polymer, copolymer).
“A structural unit derived from an acrylate ester” means a structural unit formed by cleavage of an ethylenic double bond of an acrylate ester.
“Acrylic acid ester” is a compound in which the hydrogen atom at the carboxy group terminal of acrylic acid (CH ₂ ═CH—COOH) is substituted with an organic group.
In the acrylate ester, the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent. The substituent (R ^α ) for substituting the hydrogen atom bonded to the α-position carbon atom is an atom or group other than a hydrogen atom, such as an alkyl group having 1 to 5 carbon atoms or a halogenated group having 1 to 5 carbon atoms. Examples thereof include an alkyl group and a hydroxyalkyl group. The α-position carbon atom of the acrylate ester is a carbon atom to which a carbonyl group is bonded unless otherwise specified.
Hereinafter, an acrylate ester in which a hydrogen atom bonded to a carbon atom at the α-position is substituted with a substituent may be referred to as an α-substituted acrylate ester. Further, the acrylate ester and the α-substituted acrylate ester may be collectively referred to as “(α-substituted) acrylate ester”.
“A structural unit derived from hydroxystyrene or a hydroxystyrene derivative” means a structural unit formed by cleavage of an ethylenic double bond of hydroxystyrene or a hydroxystyrene derivative.
“Hydroxystyrene derivative” is a concept including those in which the hydrogen atom at the α-position of hydroxystyrene is substituted with another substituent such as an alkyl group or an alkyl halide group, and derivatives thereof. The derivatives include those in which the hydrogen atom at the α-position may be substituted with a substituent, the hydrogen atom of the hydroxyl group of hydroxystyrene substituted with an organic group, and the hydrogen atom at the α-position substituted with a substituent. Examples include those in which a substituent other than a hydroxyl group is bonded to a good benzene ring of hydroxystyrene. The α-position (α-position carbon atom) means a carbon atom to which a benzene ring is bonded unless otherwise specified.
Examples of the substituent for substituting the hydrogen atom at the α-position of hydroxystyrene include the same substituents as those mentioned as the substituent at the α-position in the α-substituted acrylic ester.
The “structural unit derived from vinyl benzoic acid or a vinyl benzoic acid derivative” means a structural unit configured by cleavage of an ethylenic double bond of vinyl benzoic acid or a vinyl benzoic acid derivative.
The “vinyl benzoic acid derivative” is a concept including a compound in which the hydrogen atom at the α-position of vinyl benzoic acid is substituted with another substituent such as an alkyl group or an alkyl halide group, and derivatives thereof. These derivatives include those obtained by substituting the hydrogen atom of the carboxy group of vinyl benzoic acid with an organic group, which may be substituted with a hydrogen atom at the α-position, and the hydrogen atom at the α-position with a substituent. Examples thereof include those in which a substituent other than a hydroxyl group and a carboxy group is bonded to the benzene ring of vinyl benzoic acid. The α-position (α-position carbon atom) means a carbon atom to which a benzene ring is bonded unless otherwise specified.
“Styrene derivative” means a styrene-substituted α-position hydrogen atom substituted with another substituent such as an alkyl group or a halogenated alkyl group.
“Structural unit derived from styrene” and “structural unit derived from styrene derivative” mean a structural unit formed by cleavage of an ethylenic double bond of styrene or a styrene derivative.
The alkyl group as a substituent at the α-position is preferably a linear or branched alkyl group, specifically, an alkyl group having 1 to 5 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group). , N-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group) and the like.
Specific examples of the halogenated alkyl group as the substituent at the α-position include groups in which part or all of the hydrogen atoms of the above-mentioned “alkyl group as the substituent at the α-position” are substituted with a halogen atom. It is done. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable.
Specific examples of the hydroxyalkyl group as a substituent at the α-position include a group in which part or all of the hydrogen atoms of the “alkyl group as the substituent at the α-position” are substituted with a hydroxyl group. 1-5 are preferable and, as for the number of the hydroxyl groups in this hydroxyalkyl group, 1 is the most preferable.
When it is described as “may have a substituent”, when a hydrogen atom (—H) is substituted with a monovalent group, and when a methylene group (—CH ₂ —) is substituted with a divalent group Including both.
“Exposure” is a concept including general irradiation of radiation.

(Resist pattern formation method)
The resist pattern forming method according to the first aspect is a method of forming a resist pattern obtained by thickening a resist prepattern, and includes the following step A, step B, step C, and step D.
Step A: Step of forming a resist prepattern having a polar group exposed on the surface thereof on the support Step B: Pattern thickness on the support on which the resist prepattern is formed so as to cover the resist prepattern Step of forming a polymer film by applying a polymerizing composition (hereinafter also simply referred to as “polymer composition”) Step C: Step of forming a developer-insoluble layer on the surface of the resist prepattern Step D: A step of developing a resist prepattern having a developer-insoluble layer formed on the surface and the polymer film covering the resist prepattern to form a resist pattern having a thickened resist prepattern

  Hereinafter, the resist pattern forming method of this embodiment will be described with reference to the drawings. However, the present invention is not limited to this.

FIG. 1 is a schematic process diagram for explaining the resist pattern forming method of the present embodiment, and shows a series of steps when the hole pattern is thickened.
First, a resist pre-pattern 2 is formed on a support 1 using a resist composition (step A; FIG. 1 (a)). In the resist prepattern 2, the diameter of the hole there is a T _1. Polar groups are exposed on the surface 2 a of the resist pre-pattern 2.
Next, a specific polymer composition is applied on the support 1 on which the resist prepattern 2 is formed so as to cover the resist prepattern 2 to form a polymer film 3 in contact with the surface 2a of the resist prepattern 2 (Step B; FIG. 1B).
Next, a developer insoluble layer 3a (thickened portion) is formed on the resist prepattern 2 (step C; FIG. 1 (c)).
Next, the resist prepattern 2 having the developer insoluble layer 3a formed on the surface and the polymer film 3 covering the resist prepattern 2 are developed. As a result, in the present embodiment, the resist prepattern 2 is thickened in the height direction and the radial direction of the holes, and a fine resist pattern 4 having a hole diameter smaller than that of the resist prepattern 2 is formed ( Step D; FIG. 1 (d)).
In FIG. 1D, a resist pattern 4 is a hole pattern composed of a resist pre-pattern 2 and a developer insoluble layer 3a. In the resist pattern 4, the resist pre-pattern 2 is thickened, and the hole diameter is reduced from T ₁ to T ₂ (T ₂ <T ₁ ). The width of the thickened portion in the radial direction of the hole (shrink volume: SV) is T ₀ (ie, T ₁ −T ₀ = T ₂ , T ₀ = T _0a + T _0b ).

[Step A]
Step A is a step of forming a resist prepattern 2 on the support 1.
As a method of forming the resist pre-pattern 2, for example, an operation of forming a resist film using a resist composition on the support 1, an operation of exposing the resist film, and developing the resist film after the exposure And a method having an operation of forming the resist pre-pattern 2 having the surface 2a where the polar group is exposed.

The resist prepattern can be formed as follows, for example.
First, a resist composition described later is applied onto a support with a spinner or the like, and a baking (post-apply bake (PAB)) treatment is performed, for example, at a temperature of 80 to 150 ° C. for 40 to 120 seconds, preferably 60 to A resist film is formed by applying for 90 seconds.
Next, exposure or a mask pattern is performed on the resist film through a mask (mask pattern) on which a predetermined pattern is formed using an exposure apparatus such as an ArF exposure apparatus, an electron beam drawing apparatus, or an EUV exposure apparatus. After performing selective exposure by drawing or the like by direct irradiation of an electron beam without passing through, baking (post-exposure baking (PEB)) treatment is performed, for example, at a temperature of 80 to 150 ° C. for 40 to 120 seconds, preferably 60 to Apply for 90 seconds.

Next, the resist film is developed.
The development treatment is performed using an alkaline developer in the case of an alkali development process, and using a developer (organic developer) containing an organic solvent in the case of a solvent development process.
The development treatment may be an alkali development process or a solvent development process, but is preferably a solvent development process. That is, step A preferably includes an operation of developing a resist film with an organic solvent to form a resist prepattern, and further, a resist composition containing a resin component whose solubility in an organic solvent is reduced by the action of an acid. It is more preferable to include an operation of forming a resist film on a support using an object and an operation of developing the resist film with an organic solvent to form a resist prepattern. That is, the resist prepattern formed in the step A is preferably a solvent development negative resist prepattern.

In the case of an alkali development process, for example, a resist pre-pattern in which the exposed portion of the resist film is dissolved and removed in an alkali developer by the development process, the unexposed portion of the resist film remains, and the polar groups are exposed Is formed.
In the case of a solvent development process, for example, the unexposed portion of the resist film is dissolved and removed in an organic developer by a development process, and the exposed portion of the resist film remains, leaving a polar group exposed on the surface. A pattern is formed.
Examples of the polar group exposed on the surface of the resist prepattern include a carboxy group, a hydroxyl group, an amino group, and a sulfo group (—SO ₃ H).

After the development process, a rinse process is preferably performed. The rinse treatment is preferably a water rinse using pure water in the case of an alkali development process, and is preferably a rinse solution containing an organic solvent in the case of a solvent development process.
In the case of a solvent development process, after the development process or the rinse process, a process of removing the developer or rinse liquid adhering to the pattern with a supercritical fluid may be performed.
Drying is performed after development or rinsing. Moreover, depending on the case, you may perform a baking process (post-baking), for example at about 100 degreeC after the said development process.
As described above, a resist prepattern can be obtained.

Although FIG. 1 shows a series of steps for thickening the hole pattern, the shape of the resist pre-pattern is not particularly limited, and may be a line pattern, a trench pattern, or the like.
The resist pattern forming method of the present embodiment is a particularly useful method when the shape of the resist pre-pattern in step A is a hole pattern (particularly an elliptical shape).

The support is not particularly limited, and a conventionally known one can be used, and examples thereof include a substrate for electronic components and a substrate on which a predetermined wiring pattern is formed. More specifically, a silicon substrate, a metal substrate such as copper, chromium, iron, and aluminum, a glass substrate, and the like can be given. As a material for the wiring pattern, for example, copper, aluminum, nickel, gold or the like can be used.
Further, the support may be a substrate in which an inorganic and / or organic film is provided on the above-described substrate. An inorganic antireflection film (inorganic BARC) is an example of the inorganic film. Examples of the organic film include organic films such as an organic antireflection film (organic BARC) and a lower organic film in a multilayer resist method.
Here, the multilayer resist method is a method in which at least one organic film (lower organic film) and at least one resist film (upper resist film) are provided on a substrate, and the resist pattern formed on the upper resist film is used as a mask. This is a method of patterning a lower organic film, and it is said that a pattern with a high aspect ratio can be formed. That is, according to the multilayer resist method, a desired thickness can be secured by the lower organic film, so that the resist film can be thinned and a fine pattern with a high aspect ratio can be formed.
In the multilayer resist method, basically, a method having a two-layer structure of an upper layer resist film and a lower layer organic film (two layer resist method) and one or more intermediate layers (between the upper layer resist film and the lower layer organic film ( And a method of forming a multilayer structure of three or more layers provided with a metal thin film (three-layer resist method).

The exposure is not particularly limited, and radiation such as ArF excimer laser, KrF excimer laser, F ₂ excimer laser, EUV (extreme ultraviolet), VUV (vacuum ultraviolet), EB (electron beam), X-ray, soft X-ray is used. Can be done.

The exposure method of the resist film may be normal exposure (dry exposure) performed in an inert gas such as air or nitrogen, or may be immersion exposure (Liquid Immersion Lithography).
In immersion exposure, the space between the resist film and the lens at the lowest position of the exposure apparatus is previously filled with a solvent (immersion medium) having a refractive index larger than that of air, and exposure (immersion exposure) is performed in that state. It is an exposure method.
As the immersion medium, a solvent having a refractive index larger than the refractive index of air and smaller than the refractive index of the resist film to be exposed is preferable. The refractive index of such a solvent is not particularly limited as long as it is within the above range.
Examples of the solvent having a refractive index larger than the refractive index of air and smaller than the refractive index of the resist film include water, a fluorine-based inert liquid, a silicon-based solvent, and a hydrocarbon-based solvent.
Specific examples of the fluorine-based inert liquid include a fluorine-based compound such as C ₃ HCl ₂ F ₅ , C ₄ F ₉ OCH ₃ , C ₄ F ₉ OC ₂ H ₅ , and C ₅ H ₃ F ₇ as a main component. Examples thereof include liquids, and those having a boiling point of 70 to 180 ° C are preferable, and those having a boiling point of 80 to 160 ° C are more preferable. It is preferable that the fluorine-based inert liquid has a boiling point in the above range since the medium used for immersion can be removed by a simple method after the exposure is completed.
As the fluorine-based inert liquid, a perfluoroalkyl compound in which all hydrogen atoms of the alkyl group are substituted with fluorine atoms is particularly preferable. Specific examples of the perfluoroalkyl compound include a perfluoroalkyl ether compound and a perfluoroalkylamine compound.
More specifically, examples of the perfluoroalkyl ether compound include perfluoro (2-butyl-tetrahydrofuran) (boiling point: 102 ° C.). Examples of the perfluoroalkylamine compound include perfluorotributylamine ( Boiling point of 174 ° C.).
As the immersion medium, water is preferably used from the viewpoints of cost, safety, environmental problems, versatility, and the like.

Examples of the alkali developer used for the development treatment in the alkali development process include a 0.1 to 10% by mass tetramethylammonium hydroxide (TMAH) aqueous solution.
As the organic solvent contained in the organic developer used for the development process in the solvent development process, any solvent can be used as long as it can dissolve the component (A) (component (A) before exposure) blended in the resist composition. It can select suitably from well-known organic solvents. Specifically, polar solvents or hydrocarbon solvents such as ketone solvents, ester solvents, alcohol solvents, amide solvents, ether solvents and the like can be used.
A known additive can be blended in the organic developer as required. Examples of the additive include a surfactant. The surfactant is not particularly limited. For example, ionic or nonionic fluorine-based and / or silicon-based surfactants can be used.
When the surfactant is blended, the blending amount is usually 0.001 to 5% by mass, preferably 0.005 to 2% by mass, and 0.01 to 0. 5 mass% is more preferable.

  The development process can be performed by a known development method. For example, a method in which a support is immersed in a developer for a certain period of time (dip method), a developer is raised on the surface of the support by surface tension, and is left for a certain period of time. (Paddle method), spraying developer on the surface of the support (spray method), coating the developer while scanning the developer coating nozzle at a constant speed on the support rotating at a constant speed The method of continuing (dynamic dispensing method) etc. are mentioned.

  The rinse treatment (washing treatment) using the rinse liquid can be performed by a known rinse method. Examples of the method include a method of continuously applying a rinsing liquid on a support rotating at a constant speed (rotary coating method), a method of immersing the support in a rinsing liquid for a predetermined time (dip method), and the surface of the support. And a method of spraying a rinse liquid (spray method).

[Step B]
In the step B, a specific polymer composition is applied onto the support 1 on which the resist prepattern 2 is formed so as to cover the resist prepattern 2 formed in the step A. This is a step of forming the polymer film 3 in contact with the surface 2a. As the polymer composition, for example, the pattern thickening polymer composition of the first embodiment or the second embodiment described later can be used.
The polymer film 3 is formed, for example, by applying a polymer composition on the support 1 on which the resist prepattern 2 is formed so as to cover a part or the whole of the resist prepattern 2 and drying it.
As a method for applying the polymer composition, a conventionally known spin coating method, spray method, roller coating method, dipping method or the like can be used, and the spin coating method is preferable.

[Step C]
Step C is a step of forming the developer insoluble layer 3 a on the resist prepattern 2.
If the polymer composition of the first embodiment is used for the polymer film 3 formed on the resist prepattern 2 in step B, the first structural unit, the second structural unit, and the third structural unit are used. If a copolymer having a unit is included and the polymer composition of the second embodiment is used, a copolymer having a fourth structural unit and a fifth structural unit is included.
After the polymer film 3 is formed, the copolymer and the resist pre-pattern 2 interact to form a developer insoluble layer 3a (thickened portion).

  In step C, it is preferable to heat (shrink bake) the resist prepattern 2 and the polymer film 3 covering the resist prepattern 2. By such heating, the action of the first or fourth constituent unit portion of the copolymer in the polymer film 3 and the polar group exposed on the surface 2a of the resist prepattern 2 is further enhanced, and the resist prepattern 2 is likely to form a developer-insoluble layer 3a (thickened portion). In addition, the residual solvent in the resist prepattern 2 and the polymer film 3 is removed.

The heating temperature and time are appropriately set according to the type of resist material to be used, the type of copolymer in the polymer composition, or the required width of the thickened portion (shrink volume: SV). Can do.
The heating temperature is preferably 0 to 200 ° C, more preferably 50 to 170 ° C, still more preferably 70 to 160 ° C, and particularly preferably 80 to 150 ° C. If the heating temperature is equal to or higher than the preferred lower limit, S.P. V. Can be further enhanced. If it is less than or equal to the preferable upper limit value, the resist pattern shape is easily maintained favorably.
The heating time is preferably 30 to 300 seconds, more preferably 50 to 120 seconds, and particularly preferably 50 to 80 seconds.

In Step C, the first or fourth constituent unit of the copolymer has a neutral group that can be neutralized with the polar group exposed on the surface 2a of the resist prepattern 2, and the first Alternatively, an embodiment in which the neutralizing group of the fourth structural unit and the polar group exposed on the surface 2a of the resist prepattern 2 are neutralized to form the developer-insoluble layer 3a on the surface 2a is preferable.
The surface 2a of the resist pre-pattern 2 is in a state where polar groups such as carboxylic acid are exposed by deprotection of the base material component contained in the resist composition in step A. Here, when the polymer composition is coated, the polymer composition comes into contact with the resist prepattern 2 and the polar groups exposed on the surface 2a of the resist prepattern 2 and the neutralizing groups possessed by the copolymer in the polymer composition And the developer insoluble layer 3a which is insoluble in the developer at the time of development in the subsequent step D is formed more stably.
In step C, the residual solvent and the like are removed preferably by heating, and the neutralization on the resist prepattern surface proceeds better.

[Step D]
Step D is a step of developing the resist prepattern 2 having the developer-insoluble layer 3a formed thereon and the polymer film 3 covering the resist prepattern 2 to form a resist pattern 4 having a thickened resist prepattern 2. . By the development in Step D, the polymer film 3 other than the developer-insoluble layer 3a and the excess or unreacted polymer composition are removed.

  The development treatment may be performed by an alkali development process or a solvent development process. In the case of an alkali development process, an alkali developer is used, and in the case of a solvent development process, a developer containing an organic solvent (organic developer) is used. Among these, the development treatment is preferably performed by a solvent development process from the viewpoint of the removal efficiency of the polymer composition.

After the development process, a rinse process is preferably performed. The rinse treatment is preferably a water rinse using pure water in the case of an alkali development process, and is preferably a rinse solution containing an organic solvent in the case of a solvent development process.
In the case of a solvent development process, after the development process or the rinse process, a process of removing the developer or rinse liquid adhering to the pattern with a supercritical fluid may be performed.
Drying is performed after development or rinsing. In some cases, a baking process (post-bake) may be performed after the development process.
In this way, a target resist pattern in which the resist prepattern is thickened can be obtained.

In the resist pattern forming method of this embodiment, as shown in FIG. 1 (d), by the resist pre-pattern 2 is thickened, the fine pattern hole diameter T ₁ is is reduced to a hole diameter T ₂ 4 can be formed easily.

As described above, in the resist pattern forming method of this embodiment, a specific polymer composition, that is, the pattern thickening polymer composition of the first embodiment or the second embodiment described later is used. The shrink volume (SV) can be increased and a finer pattern can be formed in a good shape.
The thickening of the resist prepattern includes a case where the pattern size of the resist prepattern is faithfully reduced, and a case where, for example, an elliptical pattern is thickened to obtain a pattern close to a perfect circle. The resist pattern forming method of the present embodiment can be particularly suitably used for forming a pattern close to a perfect circle by thickening an elliptical pattern.

  In the above-described embodiment, the resist pre-pattern is a hole pattern, but is not limited to this. For example, a line-and-space pattern (hereinafter referred to as “LS pattern”) may be used. When the resist pre-pattern is an LS pattern, according to the resist pattern forming method of the present embodiment, the space width is sufficiently reduced, and a fine pattern with a good shape can be easily formed. Is more planned.

(Polymer composition for pattern thickening)
The pattern thickening polymer composition (polymer composition) according to the second embodiment is used for thickening a resist prepattern having a polar group exposed on the surface, and is composed of a resin component (X) ( (Hereinafter also referred to as “component (X)”).
Such a polymer composition is suitably used in Step B in order to increase the thickness of the resist prepattern formed in Step A in the above-described resist prepattern forming method.

In the present invention, “thickening the resist pre-pattern” means changing the dimension of the previously formed pattern (shrink). By increasing the thickness of the pattern, for example, if it is a hole pattern, an opening is formed. In the case of a line and space pattern, the line width increases and the space width decreases.
The thickening of the resist prepattern includes a case where the pattern size of the resist prepattern is faithfully reduced, and a case where, for example, an elliptical pattern is thickened to obtain a pattern close to a perfect circle. The resist pattern forming method of this aspect can be particularly suitably used for forming a pattern close to a perfect circle by thickening an elliptical pattern.

Examples of such a polymer composition include the following embodiments.
First Embodiment: Polymer composition containing a copolymer (X1) (hereinafter also referred to as “component (X1)”) having a first structural unit, a second structural unit, and a third structural unit. object.
Second Embodiment: A polymer composition containing a copolymer (X2) having a fourth structural unit and a fifth structural unit (hereinafter also referred to as “component (X2)”).

[Polymer Composition of First Embodiment]
The polymer composition of the first embodiment contains a resin component (X), and this (X) component is a copolymer having a first structural unit, a second structural unit, and a third structural unit (( X1) component).

<Copolymer (X1)>
The component (X1) is a copolymer having a first structural unit, a second structural unit, and a third structural unit. When the polymer composition contains the component (X1), the resist pre-pattern is made thicker and a resist pattern with a good shape is formed.

First structural unit:
The first structural unit is a structural unit having a thickening function of the resist prepattern.

  In the present invention, “having a resist prepattern thickening function” means that it interacts with the resist prepattern to form a part of the pattern (developer insoluble layer) on the resist prepattern surface. It means having.

For example, the first structural unit includes a structural unit containing a functional group that acts on a polar group exposed on the surface of the resist prepattern.
Examples of the first structural unit include a structural unit (u1-1) including a neutralizing group that neutralizes with a polar group exposed on the surface of the resist prepattern.
Or as a 1st structural unit, the structural unit (u1-2) containing the crosslinkable group which carries out a crosslinking reaction with the polar group exposed on the surface of the resist pre pattern is mentioned.

Structural unit (u1-1):
The structural unit (u1-1) is a structural unit containing a neutralizing group that neutralizes with a polar group exposed on the surface of the resist prepattern.
Since the (X1) component has the structural unit (u1-1) containing a neutralizing group, in Step C, the neutralizing group and the polar group exposed on the surface of the resist prepattern are By neutralization, a developer-insoluble layer is easily formed on the resist prepattern surface.
The neutralizing group in the structural unit (u1-1) is appropriately selected in consideration of the type of resist prepattern formed in step A. For example, the step A includes an operation of forming a resist film on a support using a resist composition containing a resin component whose solubility in an organic solvent is reduced by the action of an acid, and developing the resist film with an organic solvent. Including the operation of forming a resist prepattern, the neutralizing group in the structural unit (u1-1) is a basic group.
As the basic group, an “organic group having a nitrogen atom” exemplified in the description of Rx ¹ in the general formula (u1-1-1) described later is preferable.

  As a preferable structural unit (u1-1), the structural unit represented by the following general formula (u1-1-1) is mentioned, for example.

［式中、Ｒは、水素原子、炭素数１〜５のアルキル基又は炭素数１〜５のハロゲン化アルキル基である。Ｖｘ^０１は、エーテル結合若しくはアミド結合を有する２価の炭化水素基、２価の芳香族炭化水素基又は単結合である。Ｙｘ^０１は、単結合又は２価の連結基である。Ｒｘ^１は、中和性基を含む有機基である。］

[In formula, R is a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 halogenated alkyl group. Vx ⁰¹ is a divalent hydrocarbon group having an ether bond or an amide bond, a divalent aromatic hydrocarbon group, or a single bond. Yx ⁰¹ is a single bond or a divalent linking group. Rx ¹ is an organic group containing a neutralizing group. ]

[R]
In said formula (u1-1-1), R is a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 halogenated alkyl group.
The alkyl group having 1 to 5 carbon atoms in R is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, specifically, methyl group, ethyl group, propyl group, isopropyl group, n- Examples thereof include a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group. The halogenated alkyl group having 1 to 5 carbon atoms in R is a group in which part or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms are substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable.
As R, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a fluorinated alkyl group having 1 to 5 carbon atoms is preferable, and a hydrogen atom or a methyl group is particularly preferable from the viewpoint of industrial availability.

[Vx ⁰¹ ]
In the formula (u1-1-1), Vx ⁰¹ is a divalent hydrocarbon group having a ether bond or an amide bond, a divalent aromatic hydrocarbon group, or a single bond, and preferably a single bond.

The hydrocarbon group of Vx ⁰¹ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. An aliphatic hydrocarbon group means a hydrocarbon group having no aromaticity.
Examples of Vx ⁰¹ include those in which the divalent hydrocarbon group has an ether bond or an amide bond.

· Aliphatic hydrocarbon group in the aliphatic hydrocarbon radical Vx ⁰¹ may be saturated, may be unsaturated, but is preferably saturated.
More specific examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing a ring in the structure, and the like.

.. Linear or branched aliphatic hydrocarbon group The linear aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and 1 to 4 carbon atoms. More preferably, 1 to 3 is most preferable.
As the linear aliphatic hydrocarbon group, a linear alkylene group is preferable. Specifically, a methylene group [—CH ₂ —], an ethylene group [— (CH ₂ ) ₂ —], a trimethylene group [ — (CH ₂ ) ₃ —], tetramethylene group [— (CH ₂ ) ₄ —], pentamethylene group [— (CH ₂ ) ₅ —] and the like can be mentioned.
The branched aliphatic hydrocarbon group preferably has 3 to 10 carbon atoms, more preferably 3 to 6, still more preferably 3 or 4, and most preferably 3.
As the branched aliphatic hydrocarbon group, a branched alkylene group is preferred, and specifically, —CH (CH ₃ ) —, —CH (CH ₂ CH ₃ ) —, —C (CH ₃ ). _{2 -, - C (CH 3} ) (CH 2 CH 3) -, - C (CH 3) (CH 2 CH 2 CH 3) -, - C (CH 2 CH 3) 2 - ; alkylethylene groups such as - _{CH (CH 3) CH 2 -} , - CH (CH 3) CH (CH 3) -, - C (CH 3) 2 CH 2 -, - CH (CH 2 CH 3) CH 2 -, - C (CH 2 CH _{3) 2} -CH ₂ - alkyl groups such _{as; -CH (CH 3) CH 2} CH 2 -, - CH 2 CH (CH 3) CH 2 - alkyl trimethylene groups such as; -CH _(CH 3) _{CH 2 CH 2 CH 2 -,} - CH 2 CH (CH 3) CH 2 CH 2 - And the like alkyl alkylene group such as an alkyl tetramethylene group of. The alkyl group in the alkyl alkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

.. Aliphatic hydrocarbon group containing a ring in the structure As the aliphatic hydrocarbon group containing a ring in the structure, an alicyclic hydrocarbon group (a group obtained by removing two hydrogen atoms from an aliphatic hydrocarbon ring) A group in which an alicyclic hydrocarbon group is bonded to the end of a linear or branched aliphatic hydrocarbon group, or an alicyclic hydrocarbon group in the middle of a linear or branched aliphatic hydrocarbon group And a group intervening in the group. Examples of the linear or branched aliphatic hydrocarbon group include those described above.
The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably 3 to 12 carbon atoms.
The alicyclic hydrocarbon group may be polycyclic or monocyclic. The monocyclic alicyclic hydrocarbon group is preferably a group obtained by removing two hydrogen atoms from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group obtained by removing two hydrogen atoms from a polycycloalkane, and the polycycloalkane preferably has 7 to 12 carbon atoms. Adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane and the like.

Aromatic hydrocarbon group An aromatic hydrocarbon group is a hydrocarbon group having an aromatic ring.
The aromatic hydrocarbon group in Vx ⁰¹ preferably has 3 to 30 carbon atoms, more preferably 5 to 30, more preferably 5 to 20, particularly preferably 6 to 15, and most preferably 6 to 10. However, the carbon number does not include the carbon number in the substituent.
Specific examples of the aromatic ring possessed by the aromatic hydrocarbon group include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; some of the carbon atoms constituting the aromatic hydrocarbon ring are heterogeneous. Aromatic heterocycles substituted with atoms; and the like. Examples of the hetero atom in the aromatic heterocyclic ring include an oxygen atom, a sulfur atom, and a nitrogen atom.
Specifically, the aromatic hydrocarbon group is a group obtained by removing two hydrogen atoms from the aromatic hydrocarbon ring (arylene group, preferably phenylene group, naphthylene group); a hydrogen atom from the aromatic hydrocarbon ring. Groups in which one hydrogen atom of the group (aryl group) except one is substituted with an alkylene group (for example, benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, 2 A group obtained by further removing one hydrogen atom from an aryl group in an arylalkyl group such as a naphthylethyl group; The alkylene group (alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms, and particularly preferably 1 carbon atom.

^{[Yx 01]}
In the formula (u1-1-1), ^{Yx 01} is a single bond or a divalent linking group.
Examples of the divalent linking group for Yx ^01, but are not limited to, divalent hydrocarbon group which may have a substituent group, and a divalent linking group containing a hetero atom as preferred.

-Divalent hydrocarbon group which may have a substituent The hydrocarbon group as the divalent linking group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.
An aliphatic hydrocarbon group means a hydrocarbon group having no aromaticity. The aliphatic hydrocarbon group may be saturated or unsaturated, and is usually preferably saturated.
Examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing a ring in the structure, and the like.

Examples of the linear aliphatic hydrocarbon group, branched aliphatic hydrocarbon group, and aliphatic hydrocarbon group containing a ring in the structure of Yx ⁰¹ include the linear aliphatic hydrocarbon group of Vx ⁰¹ , Branched chain aliphatic hydrocarbon groups, and aliphatic hydrocarbon groups containing a ring in the structure.

  The linear or branched aliphatic hydrocarbon group may or may not have a substituent. Examples of the substituent include a fluorine atom, a fluorinated alkyl group having 1 to 5 carbon atoms substituted with a fluorine atom, and a carbonyl group.

The aliphatic hydrocarbon group containing the said ring may have a substituent and does not need to have it. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, and a carbonyl group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
The alkoxy group as the substituent is preferably an alkoxy group having 1 to 5 carbon atoms, preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group or a tert-butoxy group. Most preferred is an ethoxy group.
Examples of the halogen atom as the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.
Examples of the halogenated alkyl group as the substituent include groups in which part or all of the hydrogen atoms of the alkyl group have been substituted with the halogen atoms.
In the aliphatic hydrocarbon group containing a ring, a part of carbon atoms constituting the ring structure may be substituted with a substituent containing a hetero atom. As the substituent containing the hetero atom, —O—, —C (═O) —O—, —S—, —S (═O) ₂ —, and —S (═O) ₂ —O— are preferable.

The aromatic hydrocarbon group for Yx ^01, include the same aromatic hydrocarbon group in the Vx ^01.
In the aromatic hydrocarbon group, a hydrogen atom of the aromatic hydrocarbon group may be substituted with a substituent. For example, a hydrogen atom bonded to an aromatic ring in the aromatic hydrocarbon group may be substituted with a substituent. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, and a hydroxyl group.
The alkyl group as the substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
Examples of the alkoxy group, the halogen atom and the halogenated alkyl group as the substituent include those exemplified as the substituent for substituting the hydrogen atom of the cyclic aliphatic hydrocarbon group.

-A divalent linking group containing a hetero atom A hetero atom in a divalent linking group containing a hetero atom is an atom other than a carbon atom and a hydrogen atom. For example, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, Can be mentioned.

When Yx ⁰¹ is a divalent linking group containing a hetero atom, preferred examples of the linking group include —O—, —C (═O) —O—, —C (═O) —, —O—C ( = O) -O-, -C (= O) -NH-, -NH-, -NH-C (= NH)-(H may be substituted with a substituent such as an alkyl group or an acyl group. _{), - S -, - S} (= O) 2 -, - S (= O) 2 -O-, the formula ^{-Y 21 -O-Y 22 -,} - Y 21 -O -, - Y 21 -C (═O) —O—, —C (═O) —O—Y ²¹ —, [Y ²¹ —C (═O) —O] _{m ′} —Y ²² — or —Y ²¹ —O—C (═O ) -Y 22 ^- group represented by wherein, Y ²¹ and Y ²² are each independently a divalent which may have a substituent hydrocarbon group, O is an oxygen atom, m 'Is an integer from 0 to 3. ] Etc. are mentioned.
When the divalent linking group containing a hetero atom is —C (═O) —NH—, —NH—, —NH—C (═NH) —, H is a substituent such as an alkyl group or acyl. May be substituted. The substituent (alkyl group, acyl group, etc.) preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 1 to 5 carbon atoms.
Formula ^{-Y 21 -O-Y 22 -,} - Y 21 -O -, - Y 21 -C (= O) -O -, - C (= O) -O-Y 21 -, - [Y 21 -C (═O) —O] _{m ′} —Y ²² — or —Y ²¹ —O—C (═O) —Y ²² —, wherein Y ²¹ and Y ²² each independently have a substituent. It is also a good divalent hydrocarbon group. Examples of the divalent hydrocarbon group include those similar to the “divalent hydrocarbon group optionally having substituent (s)” mentioned in the description of the divalent linking group.
Y ²¹ is preferably a linear aliphatic hydrocarbon group, more preferably a linear alkylene group, still more preferably a linear alkylene group having 1 to 10 carbon atoms, and a straight chain having 1 to 8 carbon atoms. A chain alkylene group is particularly preferable, and a linear alkylene group having 2 to 6 carbon atoms is most preferable.
Y ²² is preferably a linear or branched aliphatic hydrocarbon group, and more preferably a methylene group, an ethylene group or an alkylmethylene group. The alkyl group in the alkylmethylene group is preferably a linear alkyl group having 1 to 5 carbon atoms, more preferably a linear alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.
In the group represented by the formula — [Y ²¹ —C (═O) —O] _{m ′} —Y ²² —, m ′ is an integer of 0 to 3, preferably an integer of 0 to 2, Or 1 is more preferable, and 1 is particularly preferable. That is, the group represented by the formula — [Y ²¹ —C (═O) —O] _{m ′} —Y ²² — is represented by the formula —Y ²¹ —C (═O) —O—Y ²² —. The group is particularly preferred. Among these, a group represented by the formula — (CH ₂ ) _{a ′} —C (═O) —O— (CH ₂ ) _{b ′} — is preferable. In the formula, a ′ is an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, further preferably 1 or 2, and most preferably 1. b ′ is an integer of 1 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 5, more preferably 1 or 2, and most preferably 1.

Among these, Yx ⁰¹ is preferably a divalent linking group, more preferably a divalent linking group containing a hetero atom, an ester bond [—C (═O) —O—], an ether bond (—O—). , —C (═O) —O—Y ²¹ —, a linear or branched alkylene group, or a combination thereof is particularly preferable.

[Rx ¹ ]
In the formula (u1-1-1), Rx ¹ is an organic group containing a neutralizing group.
The organic group containing a neutralizing group is not particularly limited as long as it can bind to a polar group exposed on the resist prepattern surface by neutralization to form a developer insoluble layer on the resist prepattern surface.
As the organic group containing a neutralizing group, for example, an organic group having a nitrogen atom is preferable.

  As the organic group having a nitrogen atom, for example, primary aliphatic amines, secondary aliphatic amines, tertiary aliphatic amines, aromatic amines or heterocyclic amines are suitable. It is mentioned as a thing.

  Aliphatic amines include ethylamine, n-propylamine, sec-butylamine, tert-butylamine, hexylamine, cyclohexylamine, octylamine, dodecylamine, ethylenediamine, tetraethylenepentamine, dimethylamine, diethylamine, di-n- Propylamine, diisopropylamine, di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine, dihexylamine, dicyclohexylamine, dioctylamine, didodecylamine, N, N-dimethylethylenediamine, N, N-dimethyltetra Ethylenepentamine, trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, triisobutylamine Tri-sec-butylamine, tripentylamine, trihexylamine, tricyclohexylamine, triheptylamine, trioctylamine, tridecylamine, tridodecylamine, N, N, N ′, N′-tetramethylmethylenediamine, N , N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N′-tetramethyltetraethylenepentamine, dimethylethylamine, methylethylpropylamine, benzylamine, phenethylamine, benzyldimethylamine, monoethanolamine , Diethanolamine, triethanolamine, N-ethyldiethanolamine, N, N-diethylethanolamine, triisopropanolamine, 2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butyl Nord, 2,2,6,6 tetramethylpiperidine, 2,2,6,6, pentamethyl piperidine, and the like.

Aromatic amines or heterocyclic amines include aniline, diphenyl (p-tolyl) amine, methyldiphenylamine, triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene, pyrrole, oxazole, thiazole, imidazole, pyrazole, furazane, pyrroline. , Pyrrolidine, imidazoline, imidazolidine, pyridine (preferably 2- (2-hydroxyethyl) pyridine), pyridazine, pyrimidine, pyrazine, pyrazoline, pyrazolidine, piperidine, piperazine (preferably 1- (2-hydroxyethyl) piperazine, 1 -[2- (2-hydroxyethoxy) ethyl] piperazine, morpholine (preferably 4- (2-hydroxyethyl) morpholine), indole, isoindole, 1H-indazo , Indoline, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, phthalazine, purine, pteridine, carbazole, phenanthridine, acridine, phenazine, 1,10-phenanthroline, adenine, adenosine, guanine, guanosine, uracil, uridine, etc. .
These aromatic amines or heterocyclic amines may have a substituent. Preferred examples of the substituent include a hydroxyl group, amino group, alkyl group, alkoxy group, acyl group, acyloxy group, aryl group, aryloxy group, nitro group, cyano group, ester group, and lactone group.

Among them, Rx ¹ is preferably a group represented by any one of the following general formula (Rx-1) or (Rx-2).

［式中、Ｒｘ^０１〜Ｒｘ^０４は、それぞれ独立に、水素原子、又は、直鎖状若しくは分岐鎖状のアルキル基であり、ｎ_０は０〜８の整数であり、＊はＹｘ^０１との結合手を示す。］

[Wherein, Rx ^{01 to} Rx ⁰⁴ are each independently a hydrogen atom or a linear or branched alkyl group, n ₀ is an integer of ₀ to 8, and * is Yx ⁰¹ Indicates a bond. ]

In the above formula, the linear or branched alkyl group of Rx ^{01 to} Rx ⁰⁴ is preferably an alkyl group having 1 to 10 carbon atoms; specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group N-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, 1,1-dimethylethyl group, 1,1-diethylpropyl group, 2,2-dimethylpropyl group, 2,2 , -Dimethylbutyl group and the like.
Of these, a methyl group or an ethyl group is preferable.
n ₀ is an integer of 0 to 8, and is preferably 2 or 4.

  Specific examples of the group represented by the general formula (Rx-1) are shown below. In the following specific examples, * indicates a bond.

The group represented by the formula (Rx-2) means a cyclic amine.
The group represented by the general formula (Rx-2) is preferably a group represented by the following general formula (Rx-2-1). Of the groups represented by the following general formula (Rx-2-1), the group represented by the general formula (Rx-2-1) is particularly preferable.

［式中、Ｒｘ^０５〜Ｒｘ^０６、Ｒｘ^０６１〜Ｒｘ^０６４は、それぞれ独立に、水素原子、又は、直鎖状若しくは分岐鎖状のアルキル基であり、ｎ１は０〜８の整数であり、＊はＹｘ^０１との結合手を示す。］

^{Wherein, Rx 05 ~Rx 06, Rx 061} ~Rx 064 each independently represent a hydrogen atom, or a linear or branched alkyl group, n1 is an integer from 0 to 8, * represents a bond with ^{Yx 01.} ]

The linear or branched alkyl groups of Rx ^{05 to} Rx ⁰⁶ and Rx ^{061 to} Rx ⁰⁶⁴ are the same as those described above for Rx ^{01 to} Rx ⁰⁴ . n1 is an integer of 0-8.

  Specific examples of the group represented by the general formula (Rx-2) are shown below. In the following specific examples, * indicates a bond.

  As the structural unit (u1-1), structural units represented by any of the following general formulas (u1-11) to (u1-13) are preferable.

［式中、Ｒは、水素原子、炭素数１〜５のアルキル基又は炭素数１〜５のハロゲン化アルキル基である。Ｒ^ｓｔは、水素原子又はメチル基である。Ｙｘ^０１’は、単結合又は２価の炭化水素基である。Ｒｘ^１は、中和性基を含む有機基を示す。］

[In formula, R is a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 halogenated alkyl group. R ^st is a hydrogen atom or a methyl group. Yx ⁰¹ ′ is a single bond or a divalent hydrocarbon group. Rx ¹ represents an organic group containing a neutralizing group. ]

In the formula (u1-11) ~ (u1-13), R, a description of the ^{Yx 01} and Rx ¹ is the same as defined above. The divalent hydrocarbon group in Yx ⁰¹ ′ is the same as described for the divalent hydrocarbon group in Yx ⁰¹ .

Specific examples of the structural unit (u1-1) will be described below. In the following specific examples, R and R ^st are the same as described above.

Structural unit (u1-2):
The structural unit (u1-2) is a structural unit containing a crosslinkable group that undergoes a crosslinking reaction with a polar group exposed on the surface of the resist prepattern.
Since the component (X1) has the structural unit (u1-2) containing a crosslinkable group, the crosslinkable group and the polar group exposed on the surface of the resist prepattern are crosslinked to form a resist prepattern surface. Thus, a developer-insoluble layer can be easily formed, and the resist prepattern can be thickened.
The crosslinkable group in the structural unit (u1-2) is appropriately selected in consideration of the type of the resist prepattern. Examples of the crosslinkable group include a residue of an isocyanate protecting agent, a glycidyl group, an oxetyl group, and a hydroxyphenyl group.

  As a preferable structural unit (u1-2), the structural unit represented by the following general formula (u1-2-1) is mentioned, for example.

［式中、Ｒは水素原子、炭素数１〜５のアルキル基又は炭素数１〜５のハロゲン化アルキル基である。Ｙｓ^０１は単結合又は２価の連結基である。Ｒｓ^０１は、イソシアナート保護剤の残基を示す。］

[In formula, R is a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 halogenated alkyl group. Ys ⁰¹ is a single bond or a divalent linking group. Rs ⁰¹ represents a residue of an isocyanate protecting agent. ]

  In the formula (u1-2-1), description of R is the same as the description of R in the general formula (u1-1-1).

In the formula (u1-2-1), Ys ⁰¹ is a single bond or a divalent linking group. The description of the divalent linking group in Ys ⁰¹ is the same as the description of the divalent linking group described for Yx ⁰¹ in the general formula (u1-1-1).
Among the divalent linking groups as those described above for Yx ^01, preferably a divalent hydrocarbon group which may have a substituent group, straight-chain aliphatic hydrocarbon group having 1 to 10 carbon atoms, or carbon A branched aliphatic hydrocarbon group of several 3 to 10 is preferable.

The linear aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6, still more preferably 1 to 4, and most preferably 1 to 3.
As the linear aliphatic hydrocarbon group, a linear alkylene group is preferable. Specifically, a methylene group [—CH ₂ —], an ethylene group [— (CH ₂ ) ₂ —], a trimethylene group [ — (CH ₂ ) ₃ —], tetramethylene group [— (CH ₂ ) ₄ —], pentamethylene group [— (CH ₂ ) ₅ —] and the like can be mentioned.
The branched aliphatic hydrocarbon group preferably has 3 to 10 carbon atoms, more preferably 3 to 6, still more preferably 3 or 4, and most preferably 3.
As the branched aliphatic hydrocarbon group, a branched alkylene group is preferred, and specifically, —CH (CH ₃ ) —, —CH (CH ₂ CH ₃ ) —, —C (CH ₃ ). _{2 -, - C (CH 3} ) (CH 2 CH 3) -, - C (CH 3) (CH 2 CH 2 CH 3) -, - C (CH 2 CH 3) 2 - ; alkylethylene groups such as - _{CH (CH 3) CH 2 -} , - CH (CH 3) CH (CH 3) -, - C (CH 3) 2 CH 2 -, - CH (CH 2 CH 3) CH 2 -, - C (CH 2 CH _{3) 2} -CH ₂ - alkyl groups such _{as; -CH (CH 3) CH 2} CH 2 -, - CH 2 CH (CH 3) CH 2 - alkyl trimethylene groups such as; -CH _(CH 3) _{CH 2 CH 2 CH 2 -,} - CH 2 CH (CH 3) CH 2 CH 2 - And the like alkyl alkylene group such as an alkyl tetramethylene group of. The alkyl group in the alkyl alkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

In the formula (u1-2-1), Rs ⁰¹ represents a residue of an isocyanate protecting agent.
Examples of the protecting agent include phenol, cresol, xylenol, ethylphenol, o-isopropylphenol, butylphenol such as p-tert-butylphenol, p-tert-octylphenol, nonylphenol, dinonylphenol, styrenated phenol, oxybenzoate, Phenols such as thymol, p-naphthol, p-nitrophenol, p-chlorophenol; methanol, ethanol, propanol, butanol, ethylene glycol, methyl cellosolve, butyl cellosolve, methyl carbitol, benzyl alcohol, phenyl cellosolve, furfuryl alcohol, Alcohols such as cyclohexanol; dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetyl Active methylenes such as acetone; mercaptans such as butyl mercaptan, thiophenol, tert-dodecyl mercaptan; amines such as diphenylamine, phenylnaphthylamine, aniline, carbazole; acid amides such as acetanilide, acetanisidide, acetic acid amide, benzamide; -Lactams such as caprolactam, δ-valerolactam, γ-butyrolactam, β-propiolactam; acid imides such as succinimide and maleic imide; imidazoles such as imidazole, 2-methylimidazole and 2-ethylimidazole Pyrazoles such as pyrazole and 3,5-dimethyl-1H-pyrazole; ureas such as urea, thiourea and ethyleneurea; carbamates such as phenyl N-phenylcarbamate and 2-oxazolidone; Imines such as ethyleneimine, polyethyleneimine, propane-2-imine; oximes such as formaldoxime, acetoaldoxime, acetoxime, methylethylketoxime, methylisobutylketoxime, cyclohexanone oxime; sodium bisulfite, potassium bisulfite, etc. And the bisulfite system.
These protective agents may be used alone or in combination of two or more.

Among these, phenol type, lactam type, alcohol type, oxime type, pyrazole type and imine type are preferable, and nonylphenol, styrenated phenol, oxybenzoic acid ester, acetoxime, methyl ethyl ketoxime, ε-caprolactam, pyrazole, 3, 5 -Dimethyl-1H-pyrazole and propane-2-imine are particularly preferred.
The “residue of the isocyanate protecting agent” is a group obtained by removing a hydrogen atom from the above protecting agent.

More specifically, the residue of the isocyanate protecting agent in Rs ⁰¹ includes a nitrogen-containing cyclic group as a suitable group.
Examples of the nitrogen-containing cyclic group in Rs ⁰¹ include groups represented by any of the following general formulas (bc-r-1) to (bc-r-8).

［式中、Ｒｓ^００１は炭素数１〜５のアルキル基である。ｎ_２は０〜３の整数である。＊は結合手を示す。］

[Wherein Rs ⁰⁰¹ represents an alkyl group having 1 to 5 carbon atoms. n ₂ is an integer of 0 to 3. * Indicates a bond. ]

Examples of the alkyl group having 1 to 5 carbon atoms of Rs ⁰⁰¹ include a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group, and a methyl group or an ethyl group is preferable.

  Specific examples of the structural unit (u1-2) are described below. In the following specific examples, R is the same as described above.

  When the polymer film that covers the resist pre-pattern is heated to the dissociation temperature or higher in Step D to be described later, the protecting group in the structural unit (u1-2) of the component (X1) is eliminated and an isocyanate group is generated. Since this isocyanate group acts on the polar group on the resist prepattern surface and the crosslinking reaction proceeds, the resist prepattern can be thickened.

The first structural unit contained in the component (X1) may be one type or two or more types.
Among the first structural units, the structural unit (u1-1) is particularly preferable because the thickening effect of the resist prepattern can be easily obtained.
The proportion of the first structural unit in the component (X1) is preferably 1 mol% or more, more preferably 1 to 50 mol%, based on all structural units (100 mol%) constituting the component (X1). 2 to 25 mol% is more preferable, and 2 to 10 mol% is particularly preferable.
When the proportion of the first structural unit is not less than the lower limit of the above preferable range, the effect of increasing the thickness of the resist prepattern is more easily obtained. On the other hand, when it is not more than the upper limit value of the preferred range, it becomes easy to balance with other structural units.

Second structural unit and third structural unit:
In the component (X1), the second structural unit and the third structural unit satisfy the following formula (α).
Glass transition temperature (Tg ₂ ) <Glass transition temperature (Tg ₃ ) (α)
Tg ₂ : Glass transition temperature of homopolymer consisting of repeating structure of the second structural unit Tg ₃ : Glass transition temperature of homopolymer consisting of repeating structure of the third structural unit

In the present invention, the glass transition temperature (Tg (° C.)) of a polymer indicates a simulation value by molecular modeling software CAChe that calculates and simulates the molecular structure.
For example, the glass transition temperature of the polymer can be obtained from CAChe Worksystem Pro. It is determined by performing structure optimization using MM geometry (MM2) and PM3 geometry using Version 6.1.1.12.33.

The second constitutional unit and the third constitutional unit need only have a relationship satisfying the above formula (α). For a homopolymer composed of a repeating structure of each constitutional unit, the preferred range of each glass transition temperature is For example:
The glass transition temperature (Tg ₃ ) of the homopolymer composed of the repeating structure of the third structural unit is preferably 109 ° C. or higher, more preferably 109 to 220 ° C., further preferably 109 to 180 ° C.
The glass transition temperature (Tg ₂ ) of the homopolymer composed of the repeating structure of the second structural unit is preferably less than 109 ° C, more preferably 20 to 100 ° C, still more preferably 20 to 85 ° C.
The absolute value of the difference between Tg ₃ and Tg ₂ is, for example, preferably 2 ° C. or more, more preferably 20 to 100 ° C., still more preferably 25 to 80 ° C.

Second structural unit:
Since the (X1) component has the second structural unit, for example, an elliptical pattern is thickened, and microfabrication into a pattern close to a perfect circle is facilitated.
As a 2nd structural unit, the structural unit represented by the following general formula (u2-1) is mentioned suitably, for example.

［式中、Ｒは、水素原子、炭素数１〜５のアルキル基又は炭素数１〜５のハロゲン化アルキル基である。Ｖｘ^０２は、２価の連結基又は単結合である。Ｒｘ^２は、置換基を有してもよい炭化水素基である。］

[In formula, R is a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 halogenated alkyl group. Vx ⁰² is a divalent linking group or a single bond. Rx ² is may have a substituent hydrocarbon group. ]

In said formula (u2-1), R is a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 halogenated alkyl group. Examples of R include those similar to R in the formula (u1-1-1).
As R, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a fluorinated alkyl group having 1 to 5 carbon atoms is preferable, and a hydrogen atom or a methyl group is particularly preferable from the viewpoint of industrial availability.

In the formula (u2-1), Vx ⁰² is a divalent linking group or a single bond.
The divalent linking group in Vx ⁰² is a divalent linking group in Yx ⁰¹ in the general formula (u1-1-1) (a divalent hydrocarbon group which may have a substituent, a hetero atom. And a divalent linking group to be included).
Among them, as the Vx ^02, a divalent linking group is preferably a divalent linking group containing a hetero atom is more preferable. Among these, ester bonds [—C (═O) —O—], —C (═O) —, ether bonds (—O—), amide bonds [—C (═O) —NH—], linear Alternatively, a branched alkylene group or a combination thereof is preferable, an ester bond or an amide bond is more preferable, and an ester bond is particularly preferable.

In the formula (u2-1), Rx ² is a hydrocarbon group that may have a substituent.
Examples of the hydrocarbon group in Rx ² include a chain hydrocarbon group and a cyclic hydrocarbon group.
The chain hydrocarbon group in Rx ² may be a straight chain hydrocarbon group or a branched chain hydrocarbon group, and the hydrocarbon group is preferably an alkyl group having 1 to 20 carbon atoms. 1-10 alkyl groups are more preferred. Specifically, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, 1,1-dimethylethyl group, 1,1 -Diethylpropyl group, 2,2-dimethylpropyl group, 2,2, -dimethylbutyl group and the like.

Examples of the substituent that the chain hydrocarbon group in Rx ² may have include a halogen atom and an oxo group (═O).

The cyclic hydrocarbon group in Rx ² may be aliphatic or aromatic, may be polycyclic, or may be monocyclic.
The monocyclic alicyclic hydrocarbon group is preferably a group obtained by removing one hydrogen atom from a monocycloalkane. The monocycloalkane preferably has 3 to 8 carbon atoms, and specific examples include cyclopentane, cyclohexane and cyclooctane.
The polycyclic alicyclic hydrocarbon group is preferably a group obtained by removing one hydrogen atom from a polycycloalkane, and the polycycloalkane is preferably one having 7 to 12 carbon atoms, specifically adamantane. , Norbornane, isobornane, tricyclodecane, tetracyclododecane and the like.
In the case of an aromatic hydrocarbon group, specific examples of the aromatic ring contained include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, phenanthrene; carbon atoms constituting the aromatic hydrocarbon ring An aromatic heterocycle partially substituted with a heteroatom; and the like. Examples of the hetero atom in the aromatic heterocyclic ring include an oxygen atom, a sulfur atom, and a nitrogen atom.
Specifically, the aromatic hydrocarbon group is a group obtained by removing one hydrogen atom from the aromatic hydrocarbon ring (aryl group); a group in which one of the hydrogen atoms of the aryl group is substituted with an alkylene group (for example, Benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, arylalkyl group such as 2-naphthylethyl group); and the like. The alkylene group (alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms, and particularly preferably 1 carbon atom.

Examples of the substituent that the cyclic hydrocarbon group in Rx ² may have include a halogen atom, an oxo group (═O), an alkyl group, and a halogenated alkyl group.

Further, in the above formula (U2-1), Rx ^2, which binds to ^{Vx 02,} from the viewpoint of thickening of the resist prepattern may be a group having an acid-dissociable. As Rx ^{2 in} this case, for example, an acid dissociable group represented by the following general formula (a1-r-2) is preferably exemplified.

［式中、Ｒａ’^４〜Ｒａ’^６は炭化水素基であり、Ｒａ’^５、Ｒａ’^６は互いに結合して環を形成してもよい。］

[Wherein, Ra ′ ^{4 to} Ra ′ ⁶ are hydrocarbon groups, and Ra ′ ⁵ and Ra ′ ⁶ may be bonded to each other to form a ring. ]

As the hydrocarbon group for Ra ′ ^{4 to} Ra ′ ^6, the same groups as those described above for Rx ² can be mentioned.
Ra ′ ⁴ is preferably an alkyl group having 1 to 5 carbon atoms.
When Ra ′ ⁵ and Ra ′ ⁶ are bonded to each other to form a ring, a group represented by general formula (a1-r2-1) shown below can be given. On the other hand, when Ra ′ ^{4 to} Ra ′ ⁶ are not bonded to each other and are independent hydrocarbon groups, groups represented by the following general formula (a1-r2-2) are exemplified.

［式中、Ｒａ’^１０は炭素数１〜１０のアルキル基であり、Ｒａ’^１１はＲａ’^１０が結合した炭素原子と共に脂肪族環式基を形成する基である。Ｒａ’^１２〜Ｒａ’^１４は、それぞれ独立に炭化水素基を示す。］

[Wherein, Ra ′ ¹⁰ is an alkyl group having 1 to ¹⁰ carbon atoms, and Ra ′ ¹¹ is a group that forms an aliphatic cyclic group together with the carbon atom to which Ra ′ ¹⁰ is bonded. Ra ′ ^{12 to} Ra ′ ¹⁴ each independently represent a hydrocarbon group. ]

Alkyl group of the alkyl group having 1 to 10 carbon atoms of formula (a1-r2-1) in, Ra ^'10 is mentioned as a straight-chain or branched hydrocarbon group of Rx ² in the formula (U2-1) Are preferred. In formula (a1-r2-1), the aliphatic cyclic group constituted by Ra ′ ¹¹ is preferably the group exemplified as the cyclic alkyl group for Rx ² in formula (u2-1).

In formula (a1-r2-2), Ra ′ ¹² and Ra ′ ¹⁴ are preferably each independently an alkyl group having 1 to 10 carbon atoms, and the alkyl group is Rx ² in formula (u2-1). Are more preferable, a linear alkyl group having 1 to 5 carbon atoms is more preferable, and a methyl group or an ethyl group is particularly preferable.
In formula (a1-r2-2), Ra ′ ¹³ is preferably a linear, branched or cyclic hydrocarbon group exemplified as the hydrocarbon group for Rx ² in formula (u2-1). . Among these, a group exemplified as the cyclic hydrocarbon group of Rx ² is more preferable.

  Specific examples of the group represented by the formula (a1-r2-1) are given below. In the following formula, “*” indicates a bond.

  Specific examples of the group represented by the formula (a1-r2-2) are given below.

Among the above, Rx ² in the formula (u2-1) is preferably a chain hydrocarbon group.
If rx ² is a group having an acid dissociable, preferably a group represented by the formula (a1-r2-2), the formula (r-pr-c1), (r-pr-c2) or ( The group represented by r-pr-c3) is more preferable.

Below, the specific example of a 2nd structural unit is described. In the following specific examples, R is the same as defined above. The glass transition temperature (Tg ₂ ) of a homopolymer comprising a repeating structure of the exemplified structural unit is also shown.

The second structural unit contained in the component (X1) may be one type or two or more types.
The proportion of the second structural unit in the component (X1) is preferably 1 mol% or more, more preferably 1 to 60 mol%, based on all structural units (100 mol%) constituting the component (X1). More preferred is ˜20 mol%.
When the ratio of the second structural unit is equal to or higher than the lower limit value of the preferable range, the shrink volume (SV) is easily increased. In addition, the resist pattern shape is further improved. On the other hand, when it is not more than the upper limit value of the preferred range, it becomes easy to balance with other structural units.

In the component (X1), the molar ratio of the first structural unit to the second structural unit (hereinafter also referred to as “(u2) / (u1)”) is (u2) / (u1) = 50/50. -90/10 are preferable, 60 / 40-85 / 15 are more preferable, and 70 / 30-80 / 20 are still more preferable.
When the molar ratio (u2) / (u1) is not more than the upper limit of the above preferable range, a thickened portion is more easily formed on the resist prepattern surface. On the other hand, if it is more than the lower limit value of the preferable range, the shrink volume (SV) is easily increased. In addition, the resist pattern shape is further improved.

Third structural unit:
Since the (X1) component has the third structural unit, the resist prepattern can be thickened more efficiently.
Suitable examples of the third structural unit include a structural unit having a styrene skeleton (hereinafter also referred to as “structural unit (u3-1)”).
As the structural unit (u3-1), a structural unit derived from hydroxystyrene, a hydroxystyrene derivative, or styrene can be given.
The number of hydroxyl groups bonded to the benzene ring of hydroxystyrene is preferably 1, 2 or 3, and more preferably 1.

  As a structural unit (u3-1), the structural unit represented by the following general formula (u3-11) or the structural unit represented by the following general formula (u3-12) is mentioned, for example.

［式（ｕ３−１１）中、Ｒ^ｓｔは水素原子又はメチル基を表し、ｍ_０１は１〜３の整数を表す。式（ｕ３−１２）中、Ｒ^ｓｔは水素原子又はメチル基を表し、Ｒ^０１は炭素数１〜５のアルキル基を表し、ｍ_０２は０または１〜３の整数を表す。］

Wherein ^{(u3-11), R st} is a hydrogen atom or a methyl _{group, m 01} represents an integer of 1 to 3. Wherein ^{(u3-12), R st} is a hydrogen atom or a methyl ^{group, R 01} represents an alkyl group having 1 to 5 carbon _{atoms, m 02} represents an integer of 0 or 1-3. ]

In the formula (u3-11), R ^st is a hydrogen atom or a methyl group, and preferably a hydrogen atom.
m ₀₁ is an integer of 1 to 3, and is preferably 1.
The substitution position of the hydroxyl group may be any of the o-position, m-position and p-position. From the viewpoint of easy availability and low price, it is preferable that m ₀₁ is 1 and has a hydroxyl group at the p-position. When m ₀₁ is 2 or 3, any substitution position can be combined.

In the formula (u3-12), R ^st is a hydrogen atom or a methyl group, and is preferably a hydrogen atom.
R ⁰¹ is a linear or branched alkyl group having 1 to 5 carbon atoms, and is a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, or pentyl. Group, isopentyl group, neopentyl group and the like. Industrially, a methyl group or an ethyl group is preferable.

_M02 is 0 or an integer of 1 to 3. Among these, _m02 is preferably 0 or 1, and particularly preferably 0 industrially.
When m ₀₂ is 1, R ⁰¹ may be substituted at any of the o-position, m-position, and p-position, and when m ₀₂ is 2 or 3, any position The substitution positions can be combined.

  Among the structural units (u3-1) described above, the structural unit represented by the general formula (u3-12) is preferable.

A specific example of the third structural unit is described below. In the following specific examples, R ^st is the same as described above. The glass transition temperature (Tg ₃ ) of a homopolymer having a repeating structure of the exemplified structural unit is also shown.

The third structural unit contained in the component (X1) may be one type or two or more types.
When the component (X1) has the third structural unit, the proportion of the third structural unit in the component (X1) is 1 mol% with respect to all the structural units (100 mol%) constituting the component (X1). The above is preferable, 1 to 98 mol% is more preferable, and 75 to 90 mol% is more preferable.
When the proportion of the third structural unit is less than or equal to the upper limit value of the preferable range, it is easy to balance with other structural units, and the shrink volume (SV) is easily increased. In addition, the resist pattern shape is further improved. On the other hand, if it is at least the lower limit value of the above preferred range, the resist prepattern can be more efficiently thickened.

In the component (X1), the molar ratio between the second structural unit and the third structural unit (hereinafter referred to as “(u3) / (u2)”) is:
(U3) / (u2) = 70/25 to 90/5 is preferable, 75/20 to 90/5 is more preferable, and 75/20 to 80/15 is further preferable.
When the molar ratio (u3) / (u2) is equal to or less than the upper limit of the preferable range, the shrink volume (SV) is easily increased. In addition, the resist pattern shape is further improved. On the other hand, if it is more than the lower limit of the preferable range, the resist pre-pattern can be made thicker more efficiently.

  In the polymer composition of the first embodiment, the component (X1) is a copolymer having a first structural unit, a second structural unit, and a third structural unit, and among these, the structural unit (u1- A copolymer having a repeating structure of 1), a structural unit represented by the general formula (u2-1), and a structural unit (u3-1) is preferably exemplified.

The component (X1) may be a random copolymer or a block copolymer. A block copolymer is preferable from the viewpoint of a large amount of shrink and a thicker pre-pattern.
The block copolymer refers to a polymer compound in which a plurality of partial constituent components (block chains) in which the same type of structural units are repeatedly bonded are bonded.

When the component (X1) is a random copolymer, the component (X1) is a radical polymerization initiator such as azobisisobutyronitrile (AIBN) or dimethyl azobisisobutyrate. It can be obtained by known radical polymerization using
When the component (X1) is a block copolymer, the component (X1) can be obtained by living polymerization because the effect of increasing the thickness of the resist prepattern can be increased by narrowing the dispersion. preferable. Living anionic polymerization and living radical polymerization are preferred as living polymerization methods, and living anionic polymerization is preferred because the effect of thickening the resist prepattern is further enhanced.

The glass transition temperature (Tg) of the component (X1) is preferably 105 ° C. or lower, more preferably 70 to 105 ° C., and further preferably 80 to 105 ° C.
When the glass transition temperature of the component (X1) is equal to or lower than the upper limit value of the preferable range, a finer pattern is easily formed in a desired good shape. When it is at least the lower limit value of the preferable range, the heat resistance of the pattern is easily maintained.

The weight average molecular weight (Mw) of the component (X1) (polystyrene conversion standard by gel permeation chromatography) is preferably 1000 to 200000, more preferably 1000 to 100,000, and still more preferably 1000 to 50000. The higher the Mw of the component (X1), the larger the width of the thickened portion (shrink volume: SV) can be adjusted, and the thickening effect can be easily obtained.
The dispersity (weight average molecular weight / number average molecular weight) of the component (X1) is preferably 2.0 or less, more preferably 1.9 or less, still more preferably 1.8 or less, and particularly preferably 1.7 or less.

In the pattern thickening polymer composition, the component (X1) may be used alone or in combination of two or more.
The proportion of the component (X1) in the component (X) is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass, or 100% by mass. Particularly preferred.

  The (X) component contained in the pattern thickening polymer composition is a copolymer other than the (X1) component and the (X2) component from the viewpoint of controlling the pattern shape before and after the resist prepattern is thickened. Hereinafter, this may be referred to as “(X3) component”).

The component (X3) is not particularly limited, and examples thereof include those that do not have a resist prepattern thickening function (a polymer that cannot form a developer-insoluble layer on the resist prepattern surface in Step C above). Can be mentioned.
Examples of the component (X3) include those having at least one selected from the group consisting of a structural unit (a1), a structural unit (a2), a structural unit (a3), and a structural unit (a4) described later.
In the polymer composition for pattern thickening, the component (X3) may be used alone or in combination of two or more.

<Solvent>
The polymer composition of the first embodiment can be prepared by mixing the component (X) and a solvent.
The solvent contained in such a polymer composition may be water or an organic solvent, and is preferably one that does not dissolve the resist prepattern, and is appropriately selected according to the polymer composition material or resist composition to be used. be able to. As such a solvent, an organic solvent is preferably used.
When water is used as the solvent, pure water is preferred, and when an organic solvent is used, one or more of ketone solvents, ester solvents, alcohol solvents, amide solvents, ether solvents, etc. are used. It is preferable to use a mixed solvent.
Among these, from the viewpoint of not dissolving the resist prepattern, it is more preferable to use an ester solvent, and it is particularly preferable to use butyl acetate.
The total solid concentration (total mass excluding the solvent) of the polymer composition for pattern thickening is preferably 0.1 to 20% by mass with respect to the total amount (100% by mass) of the polymer composition for pattern thickening. More preferably, it is 0.1-10 mass%, More preferably, it is 0.1-5 mass%.

<Other ingredients>
As long as the effect of this invention is not impaired, the polymer composition of 1st Embodiment may contain other components other than the above-mentioned (X) component and a solvent as needed.
Examples of other components include a plasticizer, a surfactant, and a photoreactive substance.

As described above, the polymer composition of the first embodiment contains a copolymer (component (X1)) having a first structural unit, a second structural unit, and a third structural unit. By using the polymer composition containing the component (X1) in the resist pattern forming method described above, a copolymer having the first structural unit and the third structural unit (however, the second structural unit is included). As compared with the case of using a polymer composition containing no), the shrink volume (SV) is further increased, and a finer pattern can be formed in a desired good shape.
The reason why this effect is obtained is not clear, but in the component (X1), the following formula (α)
Glass transition temperature (Tg ₂ ) <Glass transition temperature (Tg ₃ ) (α)
Is selected so that the glass transition temperature of the component (X1) is a copolymer having the first structural unit and the third structural unit (however, the second structural unit is present). This is presumed to be lower than the glass transition temperature.

[Polymer Composition of Second Embodiment]
The polymer composition of the second embodiment contains a resin component (X), and this (X) component contains a copolymer ((X2) component) having a fourth structural unit and a fifth structural unit. .

<Copolymer (X2)>
The component (X2) is a copolymer having a fourth structural unit and a fifth structural unit. When the polymer composition contains the component (X2), the resist pre-pattern is made thicker and a resist pattern with a good shape is formed.

Fourth structural unit:
The fourth structural unit is a structural unit having a thickening function of the resist prepattern. The description of the fourth structural unit is the same as that of the first structural unit described above.
That is, examples of the fourth structural unit include a structural unit containing a functional group that acts on a polar group exposed on the surface of the resist prepattern. For example, the fourth structural unit neutralizes with a polar group exposed on the surface of the resist prepattern. Examples thereof include a structural unit (u1-1) containing a neutralizing group or a structural unit (u1-2) containing a crosslinkable group that undergoes a crosslinking reaction with a polar group exposed on the surface of the resist prepattern.

The fourth structural unit contained in the component (X2) may be one type or two or more types.
Among the fourth structural units, the structural unit (u1-1) is particularly preferable because the thickening effect of the resist pre-pattern can be easily obtained.
The proportion of the fourth structural unit in the component (X2) is preferably from 1 to 98 mol%, more preferably from 5 to 60 mol%, based on all structural units (100 mol%) constituting the component (X2). 5 to 50 mol% is more preferable.
When the ratio of the fourth structural unit is equal to or more than the lower limit value of the preferable range, the effect of increasing the thickness of the resist prepattern is more easily obtained. On the other hand, when it is not more than the upper limit value of the preferred range, it becomes easy to balance with other structural units.

Fifth structural unit:
The fifth structural unit is a structural unit in which the glass transition temperature of the homopolymer having the repeating structure is less than 109 ° C.
The glass transition temperature (Tg ₅ ) of the homopolymer comprising the repeating structure of the fifth structural unit is less than 109 ° C., preferably 5 to 100 ° C., more preferably 20 to 85 ° C.

  Examples of the fifth structural unit include the same structural units as those described above. That is, as the fifth structural unit, a structural unit represented by the general formula (u2-1) can be suitably exemplified.

(X2) The 5th structural unit which a component has may be 1 type, or 2 or more types.
The proportion of the fifth structural unit in the component (X2) is preferably from 1 to 98 mol%, more preferably from 20 to 90 mol%, based on all the structural units (100 mol%) constituting the component (X2). 30 to 60 mol% is more preferable.
When the ratio of the fifth structural unit is equal to or higher than the lower limit value of the preferable range, the shrink volume (SV) is easily increased. In addition, the resist pattern shape is further improved. On the other hand, when it is not more than the upper limit value of the preferred range, it becomes easy to balance with other structural units.

  The component (X2) may have other structural units in addition to the fourth structural unit and the fifth structural unit.

  In the polymer composition of the second embodiment, the component (X2) is a copolymer having a fourth structural unit and a fifth structural unit. Among these, the structural unit (u1-1) and the general formula A copolymer having a repeating structure of the structural unit represented by (u2-1) is preferable.

  The component (X2) may be a random copolymer or a block copolymer. A block copolymer is preferable from the viewpoint of a large amount of shrink and a thicker pre-pattern.

When the component (X2) is a random copolymer, the component (X2) is a radical polymerization initiator such as azobisisobutyronitrile (AIBN) or dimethyl azobisisobutyrate. It can be obtained by known radical polymerization using
When the component (X2) is a block copolymer, the component (X2) can be obtained by living polymerization because the effect of thickening the resist prepattern can be further improved by narrowing the dispersion. preferable. Living anionic polymerization and living radical polymerization are preferred as living polymerization methods, and living anionic polymerization is preferred because the effect of thickening the resist prepattern is further enhanced.

The glass transition temperature (Tg) of the component (X2) is preferably 120 ° C. or lower, more preferably 30 to 100 ° C., still more preferably 50 to 90 ° C.
When the glass transition temperature of the component (X2) is not more than the upper limit of the above preferred range, a finer pattern can be easily formed in a desired good shape. When it is at least the lower limit value of the preferable range, the heat resistance of the pattern is easily maintained.

The weight average molecular weight (Mw) of the component (X2) (polystyrene conversion standard by gel permeation chromatography) is preferably 1000 to 200000, more preferably 1000 to 100,000, and still more preferably 1000 to 50000. As the Mw of the component (X2) is higher, the width of the thickened portion (shrink volume: SV) can be adjusted larger, and the effect of thickening can be easily obtained.
The dispersity (weight average molecular weight / number average molecular weight) of the component (X2) is preferably 2.0 or less, more preferably 1.9 or less, further preferably 1.8 or less, particularly preferably 1.7 or less. .2 to 1.7 is most preferred.

In the polymer composition for pattern thickening, such (X2) component may be used alone or in combination of two or more.
The proportion of the component (X2) in the component (X) is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass, or 100% by mass. Particularly preferred.

The component (X) contained in the polymer composition for pattern thickening is not only the component (X2) but also the component (X3) from the viewpoint of controlling the pattern shape before and after the resist prepattern is thickened. You may use together.
In the polymer composition for pattern thickening, the component (X3) may be used alone or in combination of two or more.

<Solvent>
The polymer composition of the second embodiment can be prepared by mixing the component (X) and a solvent.
The solvent contained in such a polymer composition may be water or an organic solvent, and is preferably one that does not dissolve the resist prepattern, and is appropriately selected according to the polymer composition material or resist composition to be used. be able to. As such a solvent, an organic solvent is preferably used.
When water is used as the solvent, pure water is preferred, and when an organic solvent is used, one or more of ketone solvents, ester solvents, alcohol solvents, amide solvents, ether solvents, etc. are used. It is preferable to use a mixed solvent.
Among these, from the viewpoint of not dissolving the resist prepattern, it is more preferable to use an ester solvent, and it is particularly preferable to use butyl acetate.
The total solid concentration (total mass excluding the solvent) of the polymer composition for pattern thickening is preferably 0.1 to 20% by mass with respect to the total amount (100% by mass) of the polymer composition for pattern thickening. More preferably, it is 0.1-10 mass%, More preferably, it is 0.1-5 mass%.

<Other ingredients>
As long as the effect of this invention is not impaired, the polymer composition of 2nd Embodiment may contain other components other than the above-mentioned (X) component and a solvent as needed.
Examples of other components include a plasticizer, a surfactant, and a photoreactive substance.

As described above, the polymer composition of the second embodiment contains a copolymer (component (X2)) having a fourth structural unit and a fifth structural unit. By using the polymer composition containing the component (X2) in the above-described resist pattern forming method, for example, it has a structural unit (structural unit (u3-1)) having a styrene skeleton and a fourth structural unit. Compared with the case of using a polymer composition containing a copolymer, the shrink volume (SV) is further increased, and a finer pattern can be formed in a desired good shape.
The reason why this effect is obtained is not clear, but in the component (X2), a structural unit (fifth structural unit) is selected so that the glass transition temperature of the homopolymer satisfies 109 ° C. or lower. Thereby, it is estimated that the glass transition temperature of the component (X2) is controlled to be lower than the glass transition temperature of the copolymer having the structural unit (u3-1)) and the fourth structural unit. .

  When the resist pre-pattern is thickened using the polymer composition of the first embodiment or the second embodiment described above, the amount of thickening in the minor axis direction (X direction) and the major axis direction (Y direction) The ratio of the thickening amount (Y direction / X direction) exceeds 1 and the thickening amount in the Y direction can be made larger than the thickening amount in the X direction. That is, by using the polymer composition of the first embodiment or the second embodiment, regardless of the shape of the target pattern, the X direction and the Y direction can be sufficiently thickened, miniaturization is achieved, and A resist pattern having a desired shape can be formed. For example, an elliptical pattern is thickened, and fine processing into a pattern close to a perfect circle is facilitated.

(Resist composition)
The resist composition that can be used in Step A in the resist pattern forming method of the present embodiment is a resist composition that generates an acid upon exposure and changes its solubility in a developer due to the action of the acid. preferable.
The resist composition preferably contains a base component (A) (hereinafter also referred to as “component (A)”) whose solubility in a developer is changed by the action of an acid.
When a resist film is formed using such a resist composition and the resist film is selectively exposed, an acid is generated in the exposed portion, and the action of the acid causes the solubility of the component (A) in the developer. On the other hand, since the solubility of the component (A) in the developer does not change in the unexposed area, a difference in solubility in the developer occurs between the exposed area and the unexposed area. Therefore, when the resist film is developed, when the resist composition is positive, the exposed portion is dissolved and removed to form a positive resist pattern, and when the resist composition is negative, the unexposed portion is dissolved. This is removed to form a negative resist pattern.
In this specification, a resist composition in which an exposed portion is dissolved and removed to form a positive resist pattern is referred to as a positive resist composition, and a resist composition that forms a negative resist pattern in which an unexposed portion is dissolved and removed. Is referred to as a negative resist composition.
In the present embodiment, the resist composition may be a positive resist composition or a negative resist composition.
In the present embodiment, the resist composition may be used for an alkali development process that uses an alkali developer for the development process at the time of forming a resist pattern. The developer composition contains an organic solvent in the development process (an organic developer). ) May be used for a solvent development process, but is preferably used for a solvent development process.

The resist composition has an acid generating ability to generate an acid upon exposure, and the (A) component may generate an acid upon exposure, and the additive component blended separately from the (A) component May generate an acid upon exposure.
Specifically, in the present embodiment, the resist composition is
(1) It may contain an acid generator component (B) that generates an acid upon exposure (hereinafter referred to as “component (B)”);
(2) The component (A) may be a component that generates an acid upon exposure;
(3) The component (A) is a component that generates an acid upon exposure, and may further contain a component (B).
That is, in the case of the above (2) and (3), the component (A) is a “base material component that generates an acid upon exposure and changes its solubility in a developer due to the action of the acid”. When the component (A) is a base material component that generates an acid upon exposure and changes its solubility in a developer due to the action of the acid, the component (A1) described later generates an acid upon exposure, and A polymer compound whose solubility in a developing solution is changed by the action of an acid is preferable. As such a polymer compound, a resin having a structural unit that generates an acid upon exposure can be used. A well-known thing can be used as a structural unit which generates an acid by exposure.
In the present embodiment, the resist composition is particularly preferably the above (1).

≪ (A) component≫
In the present embodiment, the “base component” is an organic compound having a film forming ability, and preferably an organic compound having a molecular weight of 500 or more is used. When the molecular weight of the organic compound is 500 or more, the film forming ability is improved, and in addition, a nano-level photosensitive resin pattern is easily formed.
Organic compounds used as the base material component are roughly classified into non-polymers and polymers.
As the non-polymer, those having a molecular weight of 500 or more and less than 4000 are usually used. Hereinafter, the “low molecular compound” refers to a non-polymer having a molecular weight of 500 or more and less than 4000.
As the polymer, those having a molecular weight of 1000 or more are usually used. Hereinafter, the term “resin” refers to a polymer having a molecular weight of 1000 or more.
As the molecular weight of the polymer, a polystyrene-reduced weight average molecular weight by GPC (gel permeation chromatography) is used.
As the component (A), a resin may be used, a low molecular compound may be used, or these may be used in combination.
The component (A) has a change in solubility in a developer due to the action of an acid.
In the present embodiment, the component (A) may generate an acid upon exposure.

In the present embodiment, the component (A) is a polymer compound (A1) having a structural unit containing an acid-decomposable group whose polarity is increased by the action of an acid (hereinafter also referred to as “structural unit (a1)”) (( A1) component) is preferably included.
In addition to the structural unit (a1), the component (A1) includes a structural unit containing a lactone-containing cyclic group, an —SO ₂ — containing cyclic group, or a carbonate-containing cyclic group (hereinafter also referred to as “structural unit (a2)”). And a structural unit containing a polar group-containing aliphatic hydrocarbon group (hereinafter also referred to as “structural unit (a3)”).

Structural unit (a1):
The structural unit (a1) is a structural unit containing an acid-decomposable group whose polarity is increased by the action of an acid.
The “acid-decomposable group” is an acid-decomposable group that can cleave at least part of bonds in the structure of the acid-decomposable group by the action of an acid.
Examples of the acid-decomposable group whose polarity increases by the action of an acid include a group that decomposes by the action of an acid to generate a polar group. The polar group generated here becomes a polar group exposed on the surface of the resist prepattern formed in step A.
Examples of the polar group include a carboxy group, a hydroxyl group, an amino group, a sulfo group (—SO ₃ H), and the like. Among these, a sulfo group or a polar group containing —OH in the structure (hereinafter sometimes referred to as “OH-containing polar group”) is preferable, a sulfo group, a carboxy group or a hydroxyl group is preferable, and a carboxy group is particularly preferable. .
More specifically, examples of the acid-decomposable group include groups in which the polar group is protected with an acid-dissociable group (for example, a group in which a hydrogen atom of an OH-containing polar group is protected with an acid-dissociable group).
Here, “acid-dissociable group” means
(I) an acid-dissociable group capable of cleaving a bond between the acid-dissociable group and an atom adjacent to the acid-dissociable group by the action of an acid, or
(Ii) a group capable of cleaving a bond between the acid-dissociable group and an atom adjacent to the acid-dissociable group by further decarboxylation reaction after partial bond cleavage by the action of an acid ,
Both.
The acid-dissociable group constituting the acid-decomposable group must be a group having a lower polarity than the polar group generated by dissociation of the acid-dissociable group. Is dissociated, a polar group having a polarity higher than that of the acid dissociable group is generated to increase the polarity. As a result, the polarity of the entire component (A1) increases. As the polarity increases, the solubility in the developer changes relatively, and when the developer is an organic developer, the solubility decreases.

The acid-dissociable group is not particularly limited, and those that have been proposed as acid-dissociable groups for base resins for chemically amplified resists can be used.
Among the polar groups, examples of the acid dissociable group that protects a carboxy group or a hydroxyl group include an acid dissociable group represented by the following general formula (a1-r-1) (hereinafter referred to as “acetal acid dissociable for convenience”). Group ”).

［式中、Ｒａ’^１、Ｒａ’^２は水素原子またはアルキル基、Ｒａ’^３は炭化水素基、Ｒａ’^３は、Ｒａ’^１、Ｒａ’^２のいずれかと結合して環を形成してもよい。］

[Wherein, Ra ′ ¹ and Ra ′ ² are hydrogen atoms or alkyl groups, Ra ′ ³ is a hydrocarbon group, and Ra ′ ³ may be bonded to either Ra ′ ¹ or Ra ′ ² to form a ring. Good. ]

In formula (a1-r-1), Ra ′ ¹ and Ra ′ ² are exemplified as substituents that may be bonded to the α-position carbon atom in the description of the α-substituted acrylate ester described above. Examples thereof include the same as the alkyl group, preferably a methyl group or an ethyl group, and most preferably a methyl group.

The hydrocarbon group for Ra ′ ³ is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms; a linear or branched alkyl group is preferable, specifically , Methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, 1,1-dimethylethyl group, 1,1-diethylpropyl group 2,2-dimethylpropyl group, 2,2, -dimethylbutyl group and the like can be mentioned.

When Ra ′ ³ is a cyclic hydrocarbon group, it may be aliphatic or aromatic, may be polycyclic, or may be monocyclic. The monocyclic alicyclic hydrocarbon group is preferably a group obtained by removing one hydrogen atom from a monocycloalkane. The monocycloalkane preferably has 3 to 8 carbon atoms, and specific examples include cyclopentane, cyclohexane and cyclooctane. The polycyclic alicyclic hydrocarbon group is preferably a group obtained by removing one hydrogen atom from a polycycloalkane, and the polycycloalkane is preferably one having 7 to 12 carbon atoms, specifically adamantane. , Norbornane, isobornane, tricyclodecane, tetracyclododecane and the like.

In the case of an aromatic hydrocarbon group, specific examples of the aromatic ring contained include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, phenanthrene; carbon atoms constituting the aromatic hydrocarbon ring An aromatic heterocycle partially substituted with a heteroatom; and the like. Examples of the hetero atom in the aromatic heterocyclic ring include an oxygen atom, a sulfur atom, and a nitrogen atom.
Specifically, the aromatic hydrocarbon group is a group obtained by removing one hydrogen atom from the aromatic hydrocarbon ring (aryl group); a group in which one of the hydrogen atoms of the aryl group is substituted with an alkylene group (for example, Benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, arylalkyl group such as 2-naphthylethyl group); and the like. The alkylene group (alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms, and particularly preferably 1 carbon atom.

When Ra ′ ³ is bonded to either Ra ′ ¹ or Ra ′ ² to form a ring, the cyclic group is preferably a 4- to 7-membered ring, and more preferably a 4- to 6-membered ring. Specific examples of the cyclic group include a tetrahydropyranyl group and a tetrahydrofuranyl group.

  Among the polar groups, examples of the acid dissociable group that protects the carboxy group include acid dissociable groups represented by the above general formula (a1-r-2) (the formula (a1-r- Among the acid dissociable groups represented by 2), those composed of an alkyl group may be hereinafter referred to as “tertiary alkyl ester type acid dissociable groups” for convenience).

  Examples of the acid dissociable group for protecting the hydroxyl group among the polar groups include, for example, an acid dissociable group represented by the following general formula (a1-r-3) (hereinafter referred to as “tertiary alkyloxycarbonyl acid for convenience”). Sometimes referred to as a “dissociable group”).

［式中、Ｒａ’^７〜Ｒａ’^９はアルキル基を示す。］

[Wherein, Ra ′ ^{7 to} Ra ′ ⁹ represent an alkyl group. ]

In formula (a1-r-3), Ra ′ ^{7 to} Ra ′ ⁹ are preferably an alkyl group having 1 to 5 carbon atoms, and more preferably 1 to 3 groups.
Moreover, it is preferable that the total carbon number of each alkyl group is 3-7, it is more preferable that it is 3-5, and it is most preferable that it is 3-4.

  The structural unit (a1) is a structural unit derived from an acrylate ester in which a hydrogen atom bonded to a carbon atom at the α-position may be substituted with a substituent, and an acid whose polarity is increased by the action of an acid. A structural unit containing a decomposable group; a structural unit in which at least a part of hydrogen atoms in the hydroxyl group of a structural unit derived from hydroxystyrene or a hydroxystyrene derivative is protected by a substituent containing the acid-decomposable group; vinylbenzoic acid or Examples include a structural unit in which at least a part of hydrogen atoms in —C (═O) —OH of a structural unit derived from a vinylbenzoic acid derivative is protected by a substituent containing the acid-decomposable group.

Among the above, the structural unit (a1) is preferably a structural unit derived from an acrylate ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent.
As the structural unit (a1), structural units represented by general formula (a1-1) or (a1-2) shown below are preferred.

［式中、Ｒは水素原子、炭素数１〜５のアルキル基または炭素数１〜５のハロゲン化アルキル基である。Ｖａ^１はエーテル結合、ウレタン結合、又はアミド結合を有していてもよい２価の炭化水素基であり、ｎ_ａ１は０〜２であり、Ｒａ^１は上記式（ａ１−ｒ−１）〜（ａ１−ｒ−２）で表される酸解離性基である。Ｗａ^１はｎ_ａ２＋１価の炭化水素基であり、ｎ_ａ２は１〜３であり、Ｒａ^２は上記式（ａ１−ｒ−１）または（ａ１−ｒ−３）で表される酸解離性基である。］

[Wherein, R represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. Va ¹ is a divalent hydrocarbon group that may have an ether bond, a urethane bond, or an amide bond, n _a1 is 0 to 2, and Ra ¹ is the above formula (a1-r-1) to It is an acid dissociable group represented by (a1-r-2). Wa ¹ is a n _a2 +1 valent hydrocarbon group, n _a2 is 1 to 3, and Ra ² is an acid dissociation property represented by the above formula (a1-r-1) or (a1-r-3). It is a group. ]

In the general formula (a1-1), the alkyl group having 1 to 5 carbon atoms is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, specifically, a methyl group, an ethyl group, Examples include propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. The halogenated alkyl group having 1 to 5 carbon atoms is a group in which part or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms are substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable.
R is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl group having 1 to 5 carbon atoms, and is most preferably a hydrogen atom or a methyl group in terms of industrial availability.

In the formula (a1-1), Va ¹ is a divalent hydrocarbon group which may have an ether bond, a urethane bond, or an amide bond.
The hydrocarbon group for Va ¹ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. An aliphatic hydrocarbon group means a hydrocarbon group having no aromaticity.

Aliphatic hydrocarbon group The aliphatic hydrocarbon group as the divalent hydrocarbon group in Va ¹ may be saturated or unsaturated, and is usually preferably saturated.
More specific examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing a ring in the structure, and the like.
Examples of Va ¹ include those in which the divalent hydrocarbon group has an ether bond or an amide bond.

.. Linear or branched aliphatic hydrocarbon group The linear aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and 1 to 4 carbon atoms. More preferably, 1 to 3 is most preferable.
As the linear aliphatic hydrocarbon group, a linear alkylene group is preferable. Specifically, a methylene group [—CH ₂ —], an ethylene group [— (CH ₂ ) ₂ —], a trimethylene group [ — (CH ₂ ) ₃ —], tetramethylene group [— (CH ₂ ) ₄ —], pentamethylene group [— (CH ₂ ) ₅ —] and the like can be mentioned.
The branched aliphatic hydrocarbon group preferably has 3 to 10 carbon atoms, more preferably 3 to 6, still more preferably 3 or 4, and most preferably 3.
As the branched aliphatic hydrocarbon group, a branched alkylene group is preferred, and specifically, —CH (CH ₃ ) —, —CH (CH ₂ CH ₃ ) —, —C (CH ₃ ). _{2 -, - C (CH 3} ) (CH 2 CH 3) -, - C (CH 3) (CH 2 CH 2 CH 3) -, - C (CH 2 CH 3) 2 - ; alkylethylene groups such as - _{CH (CH 3) CH 2 -} , - CH (CH 3) CH (CH 3) -, - C (CH 3) 2 CH 2 -, - CH (CH 2 CH 3) CH 2 -, - C (CH 2 CH _{3) 2} -CH ₂ - alkyl groups such _{as; -CH (CH 3) CH 2} CH 2 -, - CH 2 CH (CH 3) CH 2 - alkyl trimethylene groups such as; -CH _(CH 3) _{CH 2 CH 2 CH 2 -,} - CH 2 CH (CH 3) CH 2 CH 2 - And the like alkyl alkylene group such as an alkyl tetramethylene group of. The alkyl group in the alkyl alkylene group is preferably a linear alkyl group having 1 to 5 carbon atoms.

.. Aliphatic hydrocarbon group containing a ring in the structure As the aliphatic hydrocarbon group containing a ring in the structure, an alicyclic hydrocarbon group (a group obtained by removing two hydrogen atoms from an aliphatic hydrocarbon ring) A group in which an alicyclic hydrocarbon group is bonded to the end of a linear or branched aliphatic hydrocarbon group, or an alicyclic hydrocarbon group in the middle of a linear or branched aliphatic hydrocarbon group And a group intervening in the group. Examples of the linear or branched aliphatic hydrocarbon group include those described above.
The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably 3 to 12 carbon atoms.
The alicyclic hydrocarbon group may be polycyclic or monocyclic. The monocyclic alicyclic hydrocarbon group is preferably a group obtained by removing two hydrogen atoms from a monocycloalkane. The monocycloalkane preferably has 3 to 6 carbon atoms, and specific examples thereof include cyclopentane and cyclohexane. The polycyclic alicyclic hydrocarbon group is preferably a group obtained by removing two hydrogen atoms from a polycycloalkane, and the polycycloalkane preferably has 7 to 12 carbon atoms, specifically adamantane. , Norbornane, isobornane, tricyclodecane, tetracyclododecane and the like.

Aromatic hydrocarbon group An aromatic hydrocarbon group is a hydrocarbon group having an aromatic ring.
The aromatic hydrocarbon group as the divalent hydrocarbon group in Va ¹ preferably has 3 to 30 carbon atoms, more preferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbon atoms, and particularly preferably 6 to 15 carbon atoms. Is most preferred. However, the carbon number does not include the carbon number in the substituent.
Specific examples of the aromatic ring possessed by the aromatic hydrocarbon group include aromatic hydrocarbon rings such as benzene, biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; some of the carbon atoms constituting the aromatic hydrocarbon ring are heterogeneous. Aromatic heterocycles substituted with atoms; and the like. Examples of the hetero atom in the aromatic heterocyclic ring include an oxygen atom, a sulfur atom, and a nitrogen atom.
Specifically, the aromatic hydrocarbon group is a group obtained by removing two hydrogen atoms from the aromatic hydrocarbon ring (arylene group, preferably phenylene group, naphthylene group); a hydrogen atom from the aromatic hydrocarbon ring. Groups in which one hydrogen atom of the group (aryl group) except one is substituted with an alkylene group (for example, benzyl group, phenethyl group, 1-naphthylmethyl group, 2-naphthylmethyl group, 1-naphthylethyl group, 2 A group obtained by further removing one hydrogen atom from an aryl group in an arylalkyl group such as a naphthylethyl group; The alkylene group (alkyl chain in the arylalkyl group) preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms, and particularly preferably 1 carbon atom.

In the formula (a1-2), the n _a2 +1 valent hydrocarbon group in Wa ¹ may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group means a hydrocarbon group having no aromaticity, may be saturated or unsaturated, and is usually preferably saturated. Examples of the aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group, an aliphatic hydrocarbon group including a ring in the structure, or a linear or branched aliphatic hydrocarbon group. It includes a group formed by combining an aliphatic hydrocarbon group in the structure containing a ring, and specific examples thereof include the same groups as Va ¹ in the aforementioned formula (a1-1).
The n _a2 +1 valence is preferably 2 to 4, and more preferably 2 or 3.

  As the formula (a1-2), a structural unit represented by general formula (a1-2-01) shown below is particularly desirable.

In formula (a1-2-01), Ra ² is an acid dissociable group represented by the above formula (a1-r-1) or (a1-r-3). n _a2 is an integer of 1 to 3, preferably 1 or 2, and more preferably 1. c is an integer of 0 to 3, preferably 0 or 1, and more preferably 1. R is the same as described above.

Specific examples of the above formulas (a1-1) and (a1-2) are shown below. In the following formulas, R ^α represents a hydrogen atom, a methyl group or a trifluoromethyl group.

  The proportion of the structural unit (a1) in the component (A1) is preferably 20 to 80 mol%, more preferably 20 to 75 mol%, more preferably 25 to 70 mol%, based on all structural units constituting the component (A1). Is more preferable. By setting the proportion of the structural unit (a1) to be equal to or higher than the lower limit value, lithography properties such as sensitivity, resolution, and LWR are also improved. Moreover, the balance with another structural unit can be taken by making it below an upper limit.

Structural unit (a2):
The structural unit (a2) is a structural unit including a lactone-containing cyclic group, an —SO ₂ -containing cyclic group, or a carbonate-containing cyclic group.
The lactone-containing cyclic group, -SO ₂ -containing cyclic group or carbonate-containing cyclic group of the structural unit (a2) can be used to adhere the resist film to the substrate when the component (A1) is used for forming the resist film. It is effective in enhancing the sex.
In the present embodiment, the component (A1) preferably has the structural unit (a2).
In addition, when the structural unit (a1) includes a lactone-containing cyclic group, an —SO ₂ -containing cyclic group, or a carbonate-containing cyclic group in the structure, the structural unit also corresponds to the structural unit (a2). However, such a structural unit corresponds to the structural unit (a1) and does not correspond to the structural unit (a2).

  The structural unit (a2) is preferably a structural unit represented by the following general formula (a2-1).

［式中、Ｒは水素原子、炭素数１〜５のアルキル基又は炭素数１〜５のハロゲン化アルキル基であり、Ｙａ^２１は単結合または２価の連結基であり、Ｌａ^２１は−Ｏ−、−ＣＯＯ−、−ＣＯＮ（Ｒ’）−、−ＯＣＯ−、−ＣＯＮＨＣＯ−又は−ＣＯＮＨＣＳ−であり、Ｒ’は水素原子またはメチル基を示す。ただしＬａ^２１が−Ｏ−の場合、Ｙａ^２１は−ＣＯ−にはならない。Ｒａ^２１はラクトン含有環式基、−ＳＯ_２−含有環式基又はカーボネート含有環式基である。］

[Wherein, R is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms, Ya ²¹ is a single bond or a divalent linking group, and La ²¹ is —O -, -COO-, -CON (R ')-, -OCO-, -CONHCO- or -CONHCS-, wherein R' represents a hydrogen atom or a methyl group. However, when La ²¹ is —O—, Ya ²¹ is not —CO—. Ra ²¹ is a lactone-containing cyclic group, a —SO ₂ — containing cyclic group, or a carbonate-containing cyclic group. ]

The divalent linking group of Ya ²¹ is not particularly limited, and preferred examples thereof include a divalent hydrocarbon group which may have a substituent and a divalent linking group containing a hetero atom. The divalent hydrocarbon group which may have a substituent in Ya ^{21 and} the divalent linking group containing a hetero atom have a substituent in Va ¹ in the above formula (a1-1). Examples thereof include the same divalent hydrocarbon groups and divalent linking groups containing a hetero atom.
In this embodiment, Ya ²¹ is a single bond, an ester bond [—C (═O) —O—], an ether bond (—O—), a linear or branched alkylene group, or a combination thereof. It is preferable that

The “lactone-containing cyclic group” refers to a cyclic group containing a ring (lactone ring) containing —O—C (═O) — in the ring skeleton. The lactone ring is counted as the first ring. When only the lactone ring is present, it is called a monocyclic group, and when it has another ring structure, it is called a polycyclic group regardless of the structure. The lactone-containing cyclic group may be a monocyclic group or a polycyclic group.
Any lactone-containing cyclic group can be used without any particular limitation. Specific examples include groups represented by the following general formulas (a2-r-1) to (a2-r-7). Hereinafter, “*” represents a bond.

［式中、Ｒａ’^２１はそれぞれ独立に水素原子、アルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、水酸基、−ＣＯＯＲ”、−ＯＣ（＝Ｏ）Ｒ”、ヒドロキシアルキル基またはシアノ基であり；Ｒ”は水素原子またはアルキル基であり；Ａ”は酸素原子もしくは硫黄原子を含んでいてもよい炭素数１〜５のアルキレン基、酸素原子または硫黄原子であり、ｎ’は０〜２の整数であり、ｍ’は０または１である。］

[Wherein, Ra ′ ²¹ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, —COOR ″, —OC (═O) R ″, a hydroxyalkyl group or a cyano group. Yes; R ″ is a hydrogen atom or an alkyl group; A ″ is an alkylene group having 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom, an oxygen atom or a sulfur atom, and n ′ is 0 to 2 And m ′ is 0 or 1. ]

In general formulas (a2-r-1) to (a2-r-7), A ″ represents an oxygen atom (—O—) or a sulfur atom (—S—), and may have 1 to 5 carbon atoms. The alkylene group having 1 to 5 carbon atoms in A ″ is preferably a linear or branched alkylene group, a methylene group, an ethylene group, an n-propylene group, An isopropylene group etc. are mentioned. When the alkylene group contains an oxygen atom or a sulfur atom, specific examples thereof include a group in which —O— or —S— is interposed between the terminal or carbon atoms of the alkylene group, such as —O—CH _{2. -, - CH 2 -O-CH} 2 -, - S-CH 2 -, - CH 2 -S-CH 2 - , and the like. A ″ is preferably an alkylene group having 1 to 5 carbon atoms or —O—, more preferably an alkylene group having 1 to 5 carbon atoms, and most preferably a methylene group. Ra ′ ²¹ independently represents an alkyl group or an alkoxy group. A group, a halogen atom, a halogenated alkyl group, —COOR ″, —OC (═O) R ″, a hydroxyalkyl group or a cyano group.
The alkyl group in ra ^'21, preferably an alkyl group having 1 to 5 carbon atoms.
The alkoxy group in the ra ^'21, preferably an alkoxy group having 1 to 6 carbon atoms. The alkoxy group is preferably linear or branched. Specifically, groups of the the Ra 'group and an oxygen atom mentioned as the alkyl group in ²¹ (-O-) are linked and the like.
Examples of the halogen atom in Ra ′ ²¹ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.
'Examples of the halogenated alkyl group for ^21, the Ra' Ra part or all of the hydrogen atoms of the alkyl group in ²¹ can be mentioned it has been substituted with the aforementioned halogen atoms. As the halogenated alkyl group, a fluorinated alkyl group is preferable, and a perfluoroalkyl group is particularly preferable.

  Specific examples of groups represented by general formulas (a2-r-1) to (a2-r-7) are given below.

The “—SO ₂ -containing cyclic group” refers to a cyclic group containing a ring containing —SO ₂ — in the ring skeleton, specifically, the sulfur atom (S) in —SO ₂ — is It is a cyclic group that forms part of the ring skeleton of the cyclic group. The ring containing —SO ₂ — in the ring skeleton is counted as the first ring, and when it is only the ring, it is a monocyclic group, and when it has another ring structure, it is a polycyclic group regardless of the structure. Called. The —SO ₂ — containing cyclic group may be monocyclic or polycyclic.
-SO ₂ - containing cyclic group, in particular, -O-SO ₂ - within the ring skeleton cyclic group containing, i.e. -O-SO ₂ - -O-S- medium is a part of the ring skeleton A cyclic group containing a sultone ring to be formed is preferable. More specifically, examples of the —SO ₂ -containing cyclic group include groups represented by general formulas (a5-r-1) to (a5-r-4) shown below.

［式中、Ｒａ’^５１はそれぞれ独立に水素原子、アルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、水酸基、−ＣＯＯＲ”、−ＯＣ（＝Ｏ）Ｒ”、ヒドロキシアルキル基またはシアノ基であり；Ｒ”は水素原子またはアルキル基であり；Ａ”は酸素原子もしくは硫黄原子を含んでいてもよい炭素数１〜５のアルキレン基、酸素原子または硫黄原子であり、ｎ’は０〜２の整数である。］

[Wherein, Ra ′ ⁵¹ independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, —COOR ″, —OC (═O) R ″, a hydroxyalkyl group or a cyano group. Yes; R ″ is a hydrogen atom or an alkyl group; A ″ is an alkylene group having 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom, an oxygen atom or a sulfur atom, and n ′ is 0 to 2 Is an integer. ]

In the general formulas (a5-r-1) to (a5-r-4), A ″ is the same as A ″ in the general formulas (a2-r-1) to (a2-r-7). . Examples of the alkyl group, alkoxy group, halogen atom, halogenated alkyl group, —COOR ″, —OC (═O) R ″, and hydroxyalkyl group in Ra ′ ⁵¹ include the above-described general formulas (a2-r-1) to ( It is the same as Ra ′ ^{21 in} a2-r-7).

  Specific examples of groups represented by general formulas (a5-r-1) to (a5-r-4) are given below. “Ac” in the formula represents an acetyl group.

The “carbonate-containing cyclic group” refers to a cyclic group containing a ring (carbonate ring) containing —O—C (═O) —O— in the ring skeleton. When the carbonate ring is counted as the first ring, the carbonate ring alone is called a monocyclic group, and when it has another ring structure, it is called a polycyclic group regardless of the structure. The carbonate-containing cyclic group may be a monocyclic group or a polycyclic group.
Any carbonate ring-containing cyclic group can be used without any particular limitation. Specific examples include groups represented by the following general formulas (ax3-r-1) to (ax3-r-3).

［式中、Ｒａ’^ｘ３１はそれぞれ独立に水素原子、アルキル基、アルコキシ基、ハロゲン原子、ハロゲン化アルキル基、水酸基、−ＣＯＯＲ”、−ＯＣ（＝Ｏ）Ｒ”、ヒドロキシアルキル基またはシアノ基であり；Ｒ”は水素原子またはアルキル基であり；Ａ”は酸素原子もしくは硫黄原子を含んでいてもよい炭素数１〜５のアルキレン基、酸素原子または硫黄原子であり、ｐ’は０〜３の整数であり、ｑ’は０または１である。］

[ ^Wherein , Ra ′ ^x31 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, —COOR ″, —OC (═O) R ″, a hydroxyalkyl group or a cyano group. Yes; R ″ is a hydrogen atom or an alkyl group; A ″ is an alkylene group having 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom, an oxygen atom or a sulfur atom, and p ′ is 0 to 3 And q ′ is 0 or 1. ]

A ″ in the general formulas (ax3-r-1) to (ax3-r-3) is the same as A ″ in the general formula (a2-r-1).
As the alkyl group, alkoxy group, halogen atom, halogenated alkyl group, —COOR ″, —OC (═O) R ″, and hydroxyalkyl group in Ra ′ ^x31 , the above general formulas (a2-r-1) to ( a2-r-7) as in the same as those exemplified in the description of the Ra ^'21 of the like.

  Specific examples of groups represented by general formulas (ax3-r-1) to (ax3-r-3) are given below.

The structural unit (a2) contained in the component (A1) may be one type or two or more types.
When the component (A1) has the structural unit (a2), the proportion of the structural unit (a2) is preferably 1 to 80 mol% with respect to the total of all the structural units constituting the component (A1). It is more preferably 5 to 70 mol%, further preferably 10 to 65 mol%, and particularly preferably 10 to 60 mol%.
By making the proportion of the structural unit (a2) equal to or higher than the lower limit value, the effect of containing the structural unit (a2) can be sufficiently obtained, and by making the ratio lower than the upper limit value, balance with other structural units is achieved. Therefore, various lithography characteristics such as DOF and CDU and pattern shapes are improved.

Structural unit (a3):
The structural unit (a3) is a structural unit containing a polar group-containing aliphatic hydrocarbon group (except for those corresponding to the structural units (a1) and (a2) described above).
It is considered that when the component (A1) has the structural unit (a3), the hydrophilicity of the component (A) is increased and the resolution is improved.
Examples of the polar group in the structural unit (a3) include a hydroxyl group, a cyano group, a carboxy group, and a hydroxyalkyl group in which part of the hydrogen atoms of the alkyl group is substituted with a fluorine atom. A hydroxyl group is particularly preferable.
Examples of the aliphatic hydrocarbon group include a linear or branched hydrocarbon group having 1 to 10 carbon atoms (preferably an alkylene group) and a cyclic aliphatic hydrocarbon group (cyclic group). The cyclic group may be a monocyclic group or a polycyclic group. For example, a resin for a resist composition for an ArF excimer laser can be appropriately selected from those proposed. The cyclic group is preferably a polycyclic group, and more preferably 7 to 30 carbon atoms.
Among them, a structural unit derived from an acrylate ester containing an aliphatic polycyclic group containing a hydroxyalkyl group in which a part of hydrogen atoms of a hydroxyl group, a cyano group, a carboxy group, or an alkyl group is substituted with a fluorine atom Is more preferable. Examples of the polycyclic group include groups in which two or more hydrogen atoms have been removed from bicycloalkane, tricycloalkane, tetracycloalkane and the like. Specific examples include groups in which two or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. Among these polycyclic groups, there are groups in which two or more hydrogen atoms have been removed from adamantane, groups in which two or more hydrogen atoms have been removed from norbornane, and groups in which two or more hydrogen atoms have been removed from tetracyclododecane. Industrially preferable.

The structural unit (a3) is not particularly limited as long as it contains a polar group-containing aliphatic hydrocarbon group, and any structural unit can be used.
The structural unit (a3) is a structural unit derived from an acrylate ester in which the hydrogen atom bonded to the carbon atom at the α-position may be substituted with a substituent, and includes a polar group-containing aliphatic hydrocarbon group A structural unit is preferred.
The structural unit (a3) is derived from a hydroxyethyl ester of acrylic acid when the hydrocarbon group in the polar group-containing aliphatic hydrocarbon group is a linear or branched hydrocarbon group having 1 to 10 carbon atoms. When the hydrocarbon group is a polycyclic group, the structural unit represented by the following formula (a3-1), the structural unit represented by the formula (a3-2), the formula ( The structural unit represented by a3-3) is preferred.

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

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

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

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

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

The structural unit (a3) contained in the component (A1) may be one type or two or more types.
When the component (A1) has the structural unit (a3), the proportion of the structural unit (a3) is preferably 5 to 50 mol% with respect to the total of all the structural units constituting the component (A1). 5-40 mol% is more preferable, and 5-25 mol% is further more preferable.
By setting the proportion of the structural unit (a3) to the lower limit value or more, the effect of including the structural unit (a3) can be sufficiently obtained, and by setting the proportion of the structural unit (a3) to the upper limit value or less, balance with other structural units can be obtained. It becomes easy.

  The component (A1) may have the following structural unit (a4) in addition to the structural unit (a1), structural unit (a2), and structural unit (a3).

Structural unit (a4):
The structural unit (a4) is a structural unit containing an acid non-dissociable cyclic group. When the component (A1) has the structural unit (a4), the dry etching resistance of the formed resist pattern is improved. Moreover, the hydrophobicity of (A1) component increases. The improvement in hydrophobicity is thought to contribute to the improvement of resolution, resist pattern shape, etc., particularly in the case of organic solvent development.
The “acid non-dissociable cyclic group” in the structural unit (a4) means that when an acid is generated from the later-described component (B) by exposure, it is not dissociated even if the acid acts on the structural unit. The remaining cyclic group.
As the structural unit (a4), for example, a structural unit derived from an acrylate ester containing a non-acid-dissociable aliphatic cyclic group is preferable. Examples of the cyclic group include those similar to those exemplified for the structural unit (a1), for ArF excimer laser, for KrF excimer laser (preferably for ArF excimer laser), etc. A number of hitherto known materials can be used as the resin component of the resist composition.
In particular, at least one selected from a tricyclodecyl group, an adamantyl group, a tetracyclododecyl group, an isobornyl group, and a norbornyl group is preferable in terms of industrial availability. These polycyclic groups may have a linear or branched alkyl group having 1 to 5 carbon atoms as a substituent.
Specific examples of the structural unit (a4) include those represented by general formulas (a4-1) to (a4-7) shown below.

［式中、Ｒ^αは、水素原子、メチル基またはトリフルオロメチル基を示す。］

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

The structural unit (a4) contained in the component (A1) may be one type or two or more types.
When the component (A1) has the structural unit (a4), the proportion of the structural unit (a4) is preferably 1 to 30 mol% with respect to the total of all the structural units constituting the component (A1). More preferably, it is -20 mol%.

  The component (A1) is preferably a polymer having the structural unit (a1), and particularly preferably a copolymer having the structural unit (a1), the structural unit (a2), and the structural unit (a3). preferable.

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

In this embodiment, the weight average molecular weight (Mw) (polystyrene conversion standard by gel permeation chromatography) of the component (A1) is not particularly limited, preferably 1000 to 50000, more preferably 1500 to 30000, 2000-20000 is most preferable.
When it is below the upper limit of this range, it has sufficient solubility in a resist solvent to be used as a resist, and when it is above the lower limit of this range, dry etching resistance and resist pre-pattern cross-sectional shape are good. .

In the resist composition, as the component (A1), one type may be used alone, or two or more types may be used in combination.
The proportion of the component (A1) in the substrate component (A) is preferably 25% by mass or more, more preferably 50% by mass, further preferably 75% by mass, based on the total mass of the substrate component (A). It may be mass%. When the proportion is 25% by mass or more, the lithography properties are further improved.

In the resist composition, as the component (A), one type may be used alone, or two or more types may be used in combination.
In the present embodiment, the content of the component (A) may be adjusted according to the resist film thickness to be formed.

≪Acid generator component; (B) ingredient≫
In the present embodiment, the resist composition may contain an acid generator component (B) that generates an acid upon exposure (hereinafter referred to as “component (B)”).
The component (B) is not particularly limited, and those that have been proposed as acid generators for chemically amplified resists can be used.
Examples of such acid generators include onium salt acid generators such as iodonium salts and sulfonium salts, oxime sulfonate acid generators, bisalkyl or bisarylsulfonyldiazomethanes, and diazomethanes such as poly (bissulfonyl) diazomethanes. Examples include an acid generator, a nitrobenzyl sulfonate acid generator, an imino sulfonate acid generator, and a disulfone acid generator. Of these, it is preferable to use an onium salt acid generator.

  Examples of the onium salt-based acid generator include a compound represented by the following general formula (b-1) (hereinafter also referred to as “(b-1) component”) and a general formula (b-2). A compound (hereinafter also referred to as “(b-2) component”) or a compound represented by the general formula (b-3) (hereinafter also referred to as “(b-3) component”) can be used.

［式中、Ｒ^１０１、Ｒ^１０４〜Ｒ^１０８はそれぞれ独立に置換基を有していてもよい環式基、置換基を有していてもよい鎖状のアルキル基、または置換基を有していてもよい鎖状のアルケニル基である。Ｒ^１０４、Ｒ^１０５は、相互に結合して環を形成していてもよい。Ｒ^１０６〜Ｒ^１０８のいずれか２つは、相互に結合して環を形成していてもよい。Ｒ^１０２はフッ素原子または炭素数１〜５のフッ素化アルキル基である。Ｙ^１０１は単結合または酸素原子を含む２価の連結基である。Ｖ^１０１〜Ｖ^１０３はそれぞれ独立に単結合、アルキレン基、またはフッ素化アルキレン基である。Ｌ^１０１〜Ｌ^１０２はそれぞれ独立に単結合または酸素原子である。Ｌ^１０３〜Ｌ^１０５はそれぞれ独立に単結合、−ＣＯ−又は−ＳＯ_２−である。Ｍ’^ｍ＋はｍ価の有機カチオンである。］

[Wherein, R ¹⁰¹ and R ^{104 to} R ¹⁰⁸ each independently has a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a substituent. A chain alkenyl group which may be present. R ¹⁰⁴ and R ¹⁰⁵ may be bonded to each other to form a ring. Any two of R ^{106 to} R ¹⁰⁸ may be bonded to each other to form a ring. R ¹⁰² is a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms. Y ¹⁰¹ is a single bond or a divalent linking group containing an oxygen atom. V ^{101 to} V ¹⁰³ are each independently a single bond, an alkylene group, or a fluorinated alkylene group. L ^{101 to} L ¹⁰² are each independently a single bond or an oxygen atom. L ^{103 to} L ¹⁰⁵ are each independently a single bond, —CO— or —SO ₂ —. M ′ ^{m +} is an m-valent organic cation. ]

{Anion part}
-Anion moiety of component (b-1) In formula (b-1), R ¹⁰¹ represents a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, Alternatively, a chain alkenyl group which may have a substituent.

.. A cyclic group which may have a substituent in R ¹⁰¹ The cyclic group is preferably a cyclic hydrocarbon group, and the cyclic hydrocarbon group is an aromatic hydrocarbon group, Or an aliphatic hydrocarbon group.
The aromatic hydrocarbon group for R ¹⁰¹ is the aromatic hydrocarbon ring mentioned for the divalent aromatic hydrocarbon group for Va ¹ in the formula (a1-1), or an aromatic compound containing two or more aromatic rings. An aryl group in which one hydrogen atom is removed from the aryl group, and a phenyl group and a naphthyl group are preferable.
The cyclic aliphatic hydrocarbon group in R ¹⁰¹ is obtained by removing one hydrogen atom from the monocycloalkane or polycycloalkane mentioned as the divalent aliphatic hydrocarbon group in Va ¹ in the formula (a1-1). Group, and an adamantyl group and a norbornyl group are preferable.
In addition, the cyclic hydrocarbon group in R ¹⁰¹ may contain a hetero atom such as a heterocycle, and is specifically represented by the general formulas (a2-r-1) to (a2-r-7). Lactone-containing cyclic groups, —SO ₂ -containing cyclic groups represented by the above general formulas (a5-r-1) to (a5-r-4), and the following chemical formulas (r-hr-1) to And heterocyclic groups each represented by (r-hr-16).

Examples of the substituent in the cyclic hydrocarbon group of R ¹⁰¹ include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, and a nitro group.
The alkyl group as a substituent is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.
The alkoxy group as a substituent is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group, or a tert-butoxy group. Most preferred is an ethoxy group.
Examples of the halogen atom as a substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.
As the halogenated alkyl group as a substituent, a part or all of hydrogen atoms such as an alkyl group having 1 to 5 carbon atoms, for example, methyl group, ethyl group, propyl group, n-butyl group, tert-butyl group, and the like And a group substituted with a halogen atom.

· The chain alkyl group of the alkyl group R ¹⁰¹ may be chain substituted in R ^101, may be either linear or branched.
The linear alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms. Specifically, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, isotridecyl group, tetradecyl group Group, pentadecyl group, hexadecyl group, isohexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, heicosyl group, docosyl group and the like.
The branched alkyl group preferably has 3 to 20 carbon atoms, more preferably 3 to 15 carbon atoms, and most preferably 3 to 10 carbon atoms. Specifically, for example, 1-methylethyl group, 1-methylpropyl group, 2-methylpropyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group, Examples include 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group and the like.

The chain alkenyl group of alkenyl group R ¹⁰¹ may be chain substituted in · · R ^101, may be either linear or branched, is 2-10 carbon atoms 2-5 are more preferable, 2-4 are more preferable, and 3 is particularly preferable. Examples of the linear alkenyl group include a vinyl group, a propenyl group (allyl group), and a butynyl group. Examples of the branched alkenyl group include a 1-methylpropenyl group and a 2-methylpropenyl group.
Among the above, the chain alkenyl group is particularly preferably a propenyl group.

Examples of the substituent in the chain alkyl group or alkenyl group of R ¹⁰¹ include an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, a carbonyl group, a nitro group, an amino group, and the cyclic group in R ¹⁰¹ described above. Can be mentioned.

Among these, R ¹⁰¹ is preferably a cyclic group which may have a substituent, and more preferably a cyclic hydrocarbon group which may have a substituent. More specifically, each group is represented by a general formula (a2-r-1) to (a2-r-7) obtained by removing one or more hydrogen atoms from a phenyl group, a naphthyl group, or a polycycloalkane. Lactone-containing cyclic groups, —SO ₂ -containing cyclic groups represented by the general formulas (a5-r-1) to (a5-r-4), respectively, and the like are preferable.

In formula (b-1), Y ¹⁰¹ represents a single bond or a divalent linking group containing an oxygen atom.
When Y ¹⁰¹ is a divalent linking group containing an oxygen atom, Y ¹⁰¹ may contain an atom other than an oxygen atom. Examples of atoms other than oxygen atoms include carbon atoms, hydrogen atoms, sulfur atoms, and nitrogen atoms.
Examples of the divalent linking group containing an oxygen atom include an oxygen atom (ether bond: —O—), an ester bond (—C (═O) —O—), and an oxycarbonyl group (—O—C (═O). )-), Amide bond (—C (═O) —NH—), carbonyl group (—C (═O) —), carbonate bond (—O—C (═O) —O—), etc. A combination of a non-hydrocarbon oxygen atom-containing linking group and an alkylene group; and the like. A sulfonyl group (—SO ₂ —) may be further linked to the combination. Examples of the combination include linking groups represented by the following formulas (y-al-1) to (y-al-7), respectively.

［式中、Ｖ’^１０１は単結合または炭素数１〜５のアルキレン基であり、Ｖ’^１０２は炭素数１〜３０の２価の飽和炭化水素基である。］

[Wherein, V ′ ¹⁰¹ is a single bond or an alkylene group having 1 to 5 carbon atoms, and V ′ ¹⁰² is a divalent saturated hydrocarbon group having 1 to 30 carbon atoms. ]

The divalent saturated hydrocarbon group for V ′ ¹⁰² is preferably an alkylene group having 1 to 30 carbon atoms.

The alkylene group for V ′ ¹⁰¹ and V ′ ¹⁰² may be a linear alkylene group or a branched alkylene group, and a linear alkylene group is preferred.
Specific examples of the alkylene group in V ′ ¹⁰¹ and V ′ ¹⁰² include a methylene group [—CH ₂ —]; —CH (CH ₃ ) —, —CH (CH ₂ CH ₃ ) —, —C (CH ₃ ). _{2 -, - C (CH 3} ) (CH 2 CH 3) -, - C (CH 3) (CH 2 CH 2 CH 3) -, - C (CH 2 CH 3) 2 - ; alkylethylene groups such as ethylene Groups [—CH ₂ CH ₂ —]; —CH (CH ₃ ) CH ₂ —, —CH (CH ₃ ) CH (CH ₃ ) —, —C (CH ₃ ) ₂ CH ₂ —, —CH (CH ₂ CH - ₃₎ CH ₂ alkyl groups such as, trimethylene group (n- propylene _{group) [- CH 2 CH 2 CH} 2 -]; - CH (CH 3) CH 2 CH 2 -, - CH 2 CH (CH 3) CH ₂ - and the like alkyl trimethylene group; tetramethylene _{[-CH 2 CH 2 CH 2 CH} 2 -]; - CH (CH 3) CH 2 CH 2 CH 2 -, - CH 2 CH (CH 3) CH 2 CH 2 - alkyl tetramethylene group and the like; pentamethylene group _{[-CH 2 CH 2 CH 2 CH} 2 CH 2 -] , and the like.
Moreover, some methylene groups in the alkylene group in V ′ ¹⁰¹ or V ′ ¹⁰² may be substituted with a C 5-10 divalent aliphatic cyclic group. The aliphatic cyclic group is preferably a divalent group obtained by further removing one hydrogen atom from the cyclic aliphatic hydrocarbon group of Ra ′ ^{3 in} the formula (a1-r-1). 1,5-adamantylene group or 2,6-adamantylene group is more preferable.

Y ¹⁰¹ is preferably a divalent linking group containing an ester bond or an ether bond, and linking groups represented by the above formulas (y-al-1) to (y-al-5) are preferred.

In formula (b-1), V ¹⁰¹ represents a single bond, an alkylene group, or a fluorinated alkylene group. The alkylene group and fluorinated alkylene group for V ¹⁰¹ preferably have 1 to 4 carbon atoms. ^Examples of the fluorinated alkylene group for V ¹⁰¹ include groups in which some or all of the hydrogen atoms of the alkylene group for V ¹⁰¹ have been substituted with fluorine atoms. Among ^{them, V 101} is preferably a single bond, or a fluorinated alkylene group having 1 to 4 carbon atoms.

In formula (b-1), R ¹⁰² represents a fluorine atom or a fluorinated alkyl group having 1 to 5 carbon atoms. R ¹⁰² is preferably a fluorine atom or a C 1-5 perfluoroalkyl group, and more preferably a fluorine atom.

(B-1) Specific examples of the anion moiety of the component, for example, if the Y ¹⁰¹ is a single bond, fluorinated alkyl sulfonate anions such as trifluoromethane sulfonate anion or perfluorobutane sulfonate anion can be exemplified; Y ¹⁰¹ is In the case of a divalent linking group containing an oxygen atom, anions represented by any one of the following formulas (an-1) to (an-3) can be mentioned.

［式中、Ｒ”^１０１は、置換基を有していてもよい脂肪族環式基、前記式（ｒ−ｈｒ−１）〜（ｒ−ｈｒ−６）でそれぞれ表される基、又は置換基を有していてもよい鎖状のアルキル基であり；Ｒ”^１０２は、置換基を有していてもよい脂肪族環式基、前記一般式（ａ２−ｒ−１）〜（ａ２−ｒ−７）でそれぞれ表されるラクトン含有環式基、又は前記一般式（ａ５−ｒ−１）〜（ａ５−ｒ−４）でそれぞれ表される−ＳＯ_２−含有環式基であり；Ｒ”^１０３は、置換基を有していてもよい芳香族環式基、置換基を有していてもよい脂肪族環式基、又は置換基を有していてもよい鎖状のアルケニル基であり；Ｖ”^１０１は、フッ素化アルキレン基であり；Ｌ”^１０１は、−Ｃ（＝Ｏ）−又は−ＳＯ_２−であり；ｖ”はそれぞれ独立に０〜３の整数であり、ｑ”はそれぞれ独立に１〜２０の整数であり、ｎ”は０または１である。］

[Wherein R ″ ¹⁰¹ represents an aliphatic cyclic group which may have a substituent, a group represented by each of the above formulas (r-hr-1) to (r-hr-6), or a substituent. A chain-like alkyl group which may have a group; R ″ ¹⁰² represents an aliphatic cyclic group which may have a substituent, the above-mentioned general formulas (a2-r-1) to (a2- a lactone-containing cyclic group represented by each of r-7), or a —SO ₂ -containing cyclic group represented by each of the general formulas (a5-r-1) to (a5-r-4); R ″ ¹⁰³ is an aromatic cyclic group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain alkenyl group which may have a substituent. by ^{and; V "101} is an fluorinated alkylene ^{group; L" 101} is, -C (= O) - or -SO ₂ - a and; v "each independently 0 Is 3 integer, q "are each independently an integer of 1 to 20, n" is 0 or 1. ]

The aliphatic cyclic group which may have a substituent of R ″ ¹⁰¹ , R ″ ¹⁰² and R ″ ¹⁰³ is preferably a group exemplified as the cyclic aliphatic hydrocarbon group in R ¹⁰¹ . Examples of the substituent include the same substituents that may be substituted for the cyclic aliphatic hydrocarbon group in R ¹⁰¹ .

The aromatic cyclic group which may have a substituent in R ″ ¹⁰³ is preferably the group exemplified as the aromatic hydrocarbon group in the cyclic hydrocarbon group in R ¹⁰¹ . , R ¹⁰¹ and the same substituents that may be substituted for the aromatic hydrocarbon group.

The chain alkyl group which may have a substituent in R ″ ¹⁰¹ is preferably the group exemplified as the chain alkyl group in R ^101. The chain in R ″ ¹⁰³ has a substituent. The good chain alkenyl group is preferably the group exemplified as the chain alkenyl group in R ¹⁰¹ . V ″ ¹⁰¹ is preferably a fluorinated alkylene group having 1 to 3 carbon atoms, and particularly preferably —CF ₂ —, —CF ₂ CF ₂ —, —CHFCF ₂ —, —CF (CF ₃ ) CF ₂ —. , —CH (CF ₃ ) CF ₂ —.

-Anion part of component (b-2) In formula (b-2), R ¹⁰⁴ and R ¹⁰⁵ may each independently have a cyclic group which may have a substituent or a substituent. Examples thereof include a good chain alkyl group or a chain alkenyl group which may have a substituent, and examples thereof include the same as those described above for R ¹⁰¹ in formula (b-1). However, R ¹⁰⁴ and R ¹⁰⁵ may be bonded to each other to form a ring.
R ¹⁰⁴ and R ¹⁰⁵ are preferably a chain alkyl group which may have a substituent, and are a linear or branched alkyl group, or a linear or branched fluorinated alkyl group. It is more preferable.
The chain alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 7 carbon atoms, and still more preferably 1 to 3 carbon atoms. The carbon number of the chain alkyl group of R ¹⁰⁴ and R ¹⁰⁵ is preferably as small as possible for reasons such as good solubility in a resist solvent within the above carbon number range. In addition, in the chain alkyl group of R ¹⁰⁴ and R ^105, the greater the number of hydrogen atoms substituted with fluorine atoms, the stronger the acid strength, and against high-energy light and electron beams of 200 nm or less Since transparency improves, it is preferable. The proportion of fluorine atoms in the chain alkyl group, that is, the fluorination rate is preferably 70 to 100%, more preferably 90 to 100%, and most preferably all hydrogen atoms are substituted with fluorine atoms. Perfluoroalkyl group.
In formula (b-2), V ¹⁰² and V ¹⁰³ are each independently a single bond, an alkylene group, or a fluorinated alkylene group, and each of them is the same as V ¹⁰¹ in formula (b-1). Can be mentioned.
In formula (b-2), L ^{101 to} L ¹⁰² each independently represents a single bond or an oxygen atom.

-Anion part of (b-3) component In formula (b-3), R < ¹⁰⁶ > -R < ¹⁰⁸ > may have the cyclic group which may have a substituent, and a substituent each independently. Examples thereof include a good chain alkyl group or a chain alkenyl group which may have a substituent, and examples thereof include the same as those described above for R ¹⁰¹ in formula (b-1).
L ^{103 to} L ¹⁰⁵ are each independently a single bond, —CO— or —SO ₂ —.

{Cation part}
In formulas (b-1), (b-2) and (b-3), M ′ ^{m +} is an m-valent organic cation, preferably a sulfonium cation or an iodonium cation. The cations represented by (ca-1) to (ca-4) are particularly preferred.

［式中、Ｒ^２０１〜Ｒ^２０７、およびＲ^２１１〜Ｒ^２１２は、それぞれ独立に置換基を有していてもよいアリール基、アルキル基またはアルケニル基を表し、Ｒ^２０１〜Ｒ^２０３、Ｒ^２０６〜Ｒ^２０７、Ｒ^２１１〜Ｒ^２１２は、相互に結合して式中のイオウ原子と共に環を形成してもよい。Ｒ^２０８〜Ｒ^２０９はそれぞれ独立に水素原子または炭素数１〜５のアルキル基を表し、Ｒ^２１０は置換基を有していてもよいアリール基、アルキル基、アルケニル基、又は−ＳＯ_２−含有環式基であり、Ｌ^２０１は−Ｃ（＝Ｏ）−または−Ｃ（＝Ｏ）−Ｏ−を表し、Ｙ^２０１は、それぞれ独立に、アリーレン基、アルキレン基またはアルケニレン基を表し、ｘは１または２であり、Ｗ^２０１は（ｘ＋１）価の連結基を表す。］

[Wherein, R ^{201 to} R ²⁰⁷ and R ^{211 to} R ²¹² each independently represents an aryl group, an alkyl group or an alkenyl group which may have a substituent, and R ^{201 to} R ²⁰³ , R ²⁰⁶ to R ²⁰⁷ and R ^{211 to} R ²¹² may be bonded to each other to form a ring together with the sulfur atom in the formula. R ^{208 to} R ²⁰⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ²¹⁰ is an aryl group, alkyl group, alkenyl group, or —SO ₂ — containing an optionally substituted substituent. A cyclic group, L ²⁰¹ represents —C (═O) — or —C (═O) —O—, Y ²⁰¹ each independently represents an arylene group, an alkylene group or an alkenylene group, and x represents 1 or 2 and W ²⁰¹ represents a (x + 1) -valent linking group. ]

Examples of the aryl group in R ^{201 to} R ²⁰⁷ and R ^{211 to} R ²¹² include an unsubstituted aryl group having 6 to 20 carbon atoms, and a phenyl group and a naphthyl group are preferable.
The alkyl group in R ^{201 to} R ²⁰⁷ and R ^{211 to} R ²¹² is a chain or cyclic alkyl group and preferably has 1 to 30 carbon atoms.
The alkenyl group in R ^{201 to} R ²⁰⁷ and R ^{211 to} R ²¹² preferably has 2 to 10 carbon atoms.
Examples of the substituent that R ^{201 to} R ²⁰⁷ and R ^{210 to} R ²¹² may have include an alkyl group, a halogen atom, a halogenated alkyl group, a carbonyl group, a cyano group, an amino group, an aryl group, and an arylthio group. And groups represented by the following formulas (ca-r-1) to (ca-r-7).
The aryl group in the arylthio group as a substituent is the same as that described for R ¹⁰¹ , and specifically includes a phenylthio group or a biphenylthio group.

［式中、Ｒ’^２０１はそれぞれ独立に、水素原子、置換基を有していてもよい環式基、鎖状のアルキル基、または鎖状のアルケニル基である。］

[Wherein, R ′ ²⁰¹ each independently represents a hydrogen atom, an optionally substituted cyclic group, a chain alkyl group, or a chain alkenyl group. ]

The cyclic group which may have a substituent of R ′ ^201, a chain alkyl group which may have a substituent, or a chain alkenyl group which may have a substituent are as described above. In addition to the same groups as those described above for R ^{101 in} formula (b-1), a cyclic group which may have a substituent or a chain alkyl group which may have a substituent may have the above formula ( Examples thereof include the same acid dissociable groups represented by a1-r-2).

^{R 201 ~R 203, R 206 ~R} 207, R 211 ~R 212 , when bonded to each other to form a ring with the sulfur atom, a sulfur atom, an oxygen atom, or a hetero atom such as nitrogen atom, carbonyl _{group, -SO -, - SO 2 -} , - SO 3 -, - COO -, - CONH- , or -N _(R N) - (. the _{R N} is an alkyl group having 1 to 5 carbon atoms), etc. You may couple | bond through the functional group of. As the ring to be formed, one ring containing a sulfur atom in the ring skeleton in the formula is preferably a 3- to 10-membered ring, particularly a 5- to 7-membered ring, including the sulfur atom. preferable. Specific examples of the ring formed include, for example, thiophene ring, thiazole ring, benzothiophene ring, thianthrene ring, benzothiophene ring, dibenzothiophene ring, 9H-thioxanthene ring, thioxanthone ring, thianthrene ring, phenoxathiin ring, tetrahydro A thiophenium ring, a tetrahydrothiopyranium ring, etc. are mentioned.

R ^{208 to} R ²⁰⁹ each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and when formed into an alkyl group, they are bonded to each other to form a ring. May be formed.

R ²¹⁰ may have an aryl group which may have a substituent, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a substituent. -SO ₂ - containing cyclic group.
The aryl group in R ^210, include unsubstituted aryl group having 6 to 20 carbon atoms, a phenyl group, a naphthyl group.
The alkyl group for R ²¹⁰ is preferably a chain or cyclic alkyl group having 1 to 30 carbon atoms.
The alkenyl group for R ²¹⁰ preferably has 2 to 10 carbon atoms.
Examples of the —SO ₂ — containing cyclic group which may have a substituent in R ²¹⁰ include those similar to the above-mentioned “—SO ₂ — containing cyclic group”, and the general formula (a5- The group represented by r-1) is preferred.

Y ²⁰¹ each independently represents an arylene group, an alkylene group or an alkenylene group.
Examples of the arylene group for Y ²⁰¹ include a group in which one hydrogen atom has been removed from the aryl group exemplified as the aromatic hydrocarbon group for R ¹⁰¹ in the above formula (b-1).
Examples of the alkylene group and alkenylene group for Y ²⁰¹ include the same aliphatic hydrocarbon groups as the divalent hydrocarbon group for Va ¹ in the general formula (a1-1).

In the formula (ca-4), x is 1 or 2.
W ²⁰¹ is a (x + 1) valent, that is, a divalent or trivalent linking group.
The divalent linking group in W ²⁰¹ is preferably a divalent hydrocarbon group which may have a substituent, and examples thereof include the same hydrocarbon groups as Ya ²¹ in the general formula (a2-1). The divalent linking group in W ²⁰¹ may be linear, branched or cyclic, and is preferably cyclic. Of these, a group in which two carbonyl groups are combined at both ends of the arylene group is preferable. Examples of the arylene group include a phenylene group and a naphthylene group, and a phenylene group is particularly preferable.
^Examples of the trivalent linking group in W ²⁰¹ include a group obtained by removing one hydrogen atom from the divalent linking group in W ²⁰¹ , a group in which the divalent linking group is further bonded to the divalent linking group, and the like. Can be mentioned. The trivalent linking group in W ²⁰¹ is preferably a group in which two carbonyl groups are bonded to an arylene group.

  Specific examples of suitable cations represented by the formula (ca-1) include cations represented by the following formulas (ca-1-1) to (ca-1-63), respectively.

［式中、ｇ１、ｇ２、ｇ３は繰返し数を示し、ｇ１は１〜５の整数であり、ｇ２は０〜２０の整数であり、ｇ３は０〜２０の整数である。］

[Wherein, g1, g2, and g3 represent the number of repetitions, g1 is an integer of 1 to 5, g2 is an integer of 0 to 20, and g3 is an integer of 0 to 20. ]

［式中、Ｒ”^２０１は水素原子又は置換基であって、置換基としては前記Ｒ^２０１〜Ｒ^２０７、およびＲ^２１０〜Ｒ^２１２が有していてもよい置換基として挙げたものと同様である。］

[Wherein R ″ ²⁰¹ is a hydrogen atom or a substituent, and the substituent is the same as the substituents that R ^{201 to} R ²⁰⁷ and R ^{210 to} R ²¹² may have. is there.]

  Specific examples of suitable cations represented by the formula (ca-3) include cations represented by the following formulas (ca-3-1) to (ca-3-6).

  Specific examples of suitable cations represented by the formula (ca-4) include cations represented by the following formulas (ca-4-1) to (ca-4-2).

As the component (B), one type of acid generator described above may be used alone, or two or more types may be used in combination.
In this embodiment, when a resist composition contains (B) component, 0.5-60 mass parts is preferable with respect to 100 mass parts of (A) component, and, as for content of (B) component, 1-50 masses. Part is more preferable, and 1 to 40 parts by mass is further preferable.
By forming the content of the component (B) within the above range, pattern formation is sufficiently performed. Moreover, when each component of a resist composition is melt | dissolved in the organic solvent, since a uniform solution is obtained and storage stability becomes favorable, it is preferable.

≪Other ingredients≫
In this embodiment, the resist composition may further contain other components in addition to the component (A) or in addition to the components (A) and (B).
Examples of the other components include (D) component, (E) component, (F) component, and (S) component described later.

(D) component:
In the present embodiment, the resist composition may further contain an acid diffusion controller component (hereinafter also referred to as “component (D)”).
The component (D) acts as a quencher (acid diffusion controller) that traps acid generated by exposure from the component (B) and the like.
The component (D) in the present embodiment may be a photodegradable base (D1) (hereinafter referred to as “(D1) component”) that is decomposed by exposure and loses acid diffusion controllability, and the component (D1). It may be a nitrogen-containing organic compound (D2) (hereinafter referred to as “component (D2)”) that does not fall under.

-(D1) component By making it the resist composition containing (D1) component, when forming a resist pattern, the contrast of an exposure part and a non-exposure part can be improved.
The component (D1) is not particularly limited as long as it is decomposed by exposure and loses acid diffusion controllability, and is a compound represented by the following general formula (d1-1) (hereinafter referred to as “(d1-1) component”). ), A compound represented by the following general formula (d1-2) (hereinafter referred to as “(d1-2) component”) and a compound represented by the following general formula (d1-3) (hereinafter referred to as “(d1- One or more compounds selected from the group consisting of “3) component”) are preferred.
The components (d1-1) to (d1-3) are decomposed in the exposed portion and lose acid diffusion controllability (basicity), and thus do not act as a quencher, and act as a quencher in an unexposed portion.

［式中、Ｒｄ^１〜Ｒｄ^４は置換基を有していてもよい環式基、置換基を有していてもよい鎖状のアルキル基、または置換基を有していてもよい鎖状のアルケニル基である。ただし、式（ｄ１−２）中のＲｄ^２における、Ｓ原子に隣接する炭素原子にはフッ素原子は結合していないものとする。Ｙｄ^１は単結合、または２価の連結基である。Ｍ^ｍ＋はそれぞれ独立にｍ価の有機カチオンである。］

[Wherein Rd ^{1 to} Rd ⁴ are a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a chain which may have a substituent. Of the alkenyl group. However, a fluorine atom is not bonded to a carbon atom adjacent to the S atom in Rd ² in the formula (d1-2). Yd ¹ is a single bond or a divalent linking group. M ^{m +} is each independently an m-valent organic cation. ]

{(D1-1) component}
.. Anion moiety In formula (d1-1), Rd ¹ has a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a substituent. A chain alkenyl group which may be the same as R ¹⁰¹ .
Among these, Rd ¹ may have an aromatic hydrocarbon group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a substituent. A chain hydrocarbon group is preferred. The substituent that these groups may have is preferably a hydroxyl group, a fluorine atom or a fluorinated alkyl group.
The aromatic hydrocarbon group is more preferably a phenyl group or a naphthyl group.
The aliphatic cyclic group is more preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane.
As the chain hydrocarbon group, a chain alkyl group is preferable. The chain alkyl group preferably has 1 to 10 carbon atoms, and specifically includes a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a nonyl group. A linear alkyl group such as a group or decyl group; 1-methylethyl group, 1-methylpropyl group, 2-methylpropyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-ethylbutyl group And branched chain alkyl groups such as 2-ethylbutyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, and the like.

When the chain alkyl group is a fluorinated alkyl group having a fluorine atom or a fluorinated alkyl group as a substituent, the fluorinated alkyl group preferably has 1 to 11 carbon atoms, more preferably 1 to 8 carbon atoms. The fluorinated alkyl group, which is more preferably ˜4, may contain an atom other than a fluorine atom. Examples of atoms other than fluorine atoms include oxygen atoms, carbon atoms, hydrogen atoms, sulfur atoms, and nitrogen atoms.
Rd ¹ is preferably a fluorinated alkyl group in which some or all of the hydrogen atoms constituting the linear alkyl group are substituted by fluorine atoms, and the hydrogen atom constituting the linear alkyl group It is preferable that all are fluorinated alkyl groups (linear perfluoroalkyl groups) substituted with fluorine atoms.

  Preferred specific examples of the anion moiety of the component (d1-1) are shown below.

..Cation part In the formula (d1-1), M ^{m +} is an m-valent organic cation.
The organic cation of M ^{m +} is not particularly limited, and examples thereof include those similar to the cations represented by the general formulas (ca-1) to (ca-4), respectively, and the formula (ca-1- Cations represented by 1) to (ca-1-63) are preferable.
As the component (d1-1), one type may be used alone, or two or more types may be used in combination.

{(D1-2) component}
.. Anion moiety In formula (d1-2), Rd ² has a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a substituent. A chain-like alkenyl group which may be present, and the same groups as those for R ¹⁰¹ may be mentioned.
However, a fluorine atom is not bonded to a carbon atom adjacent to the S atom in Rd ² (not fluorine-substituted). Thereby, the anion of (d1-2) component turns into a moderate weak acid anion, and the quenching ability of (D) component improves.
Rd ² is preferably an aliphatic cyclic group which may have a substituent, and a group in which one or more hydrogen atoms have been removed from adamantane, norbornane, isobornane, tricyclodecane, tetracyclododecane or the like. (It may have a substituent); it is more preferably a group obtained by removing one or more hydrogen atoms from camphor or the like.
The hydrocarbon group of Rd ² may have a substituent, and examples of the substituent include a hydrocarbon group (aromatic hydrocarbon group, aliphatic hydrocarbon group) in Rd ¹ of the formula (d1-1). The same thing as the substituent which may have is mentioned.

  Preferred specific examples of the anion moiety of the component (d1-2) are shown below.

..Cation part In the formula (d1-2), M ^{m +} is an m-valent organic cation, which is the same as M ^{m +} in the formula (d1-1).
As the component (d1-2), one type may be used alone, or two or more types may be used in combination.

{(D1-3) component}
.. Anion moiety In formula (d1-3), Rd ³ has a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a substituent. A chain alkenyl group which may be the same as R ^101, and is preferably a cyclic group containing a fluorine atom, a chain alkyl group, or a chain alkenyl group. Among them, a fluorinated alkyl group is preferable, and the same as the fluorinated alkyl group for Rd ¹ is more preferable.

In formula (d1-3), Rd ⁴ may have a cyclic group which may have a substituent, a chain alkyl group which may have a substituent, or a substituent. Examples of the chain alkenyl group include those similar to R ¹⁰¹ .
Among these, an alkyl group, an alkoxy group, an alkenyl group, or a cyclic group which may have a substituent is preferable.
The alkyl group in Rd ⁴ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, specifically, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group. Tert-butyl group, pentyl group, isopentyl group, neopentyl group and the like. A part of the hydrogen atoms of the alkyl group of Rd ⁴ may be substituted with a hydroxyl group, a cyano group, or the like.
The alkoxy group in Rd ⁴ is preferably an alkoxy group having 1 to 5 carbon atoms. Specific examples of the alkoxy group having 1 to 5 carbon atoms include methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n- Examples include butoxy group and tert-butoxy group. Of these, a methoxy group and an ethoxy group are preferable.

Examples of the alkenyl group in Rd ⁴ include those similar to R ¹⁰¹ described above, and a vinyl group, a propenyl group (allyl group), a 1-methylpropenyl group, and a 2-methylpropenyl group are preferable. These groups may further have, as a substituent, an alkyl group having 1 to 5 carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms.

Examples of the cyclic group for Rd ⁴ include the same groups as those described above for R ^101, and one or more hydrogen atoms are removed from a cycloalkane such as cyclopentane, cyclohexane, adamantane, norbornane, isobornane, tricyclodecane, and tetracyclododecane. An alicyclic group or an aromatic group such as a phenyl group or a naphthyl group is preferred. When Rd ⁴ is an alicyclic group, the resist composition is well dissolved in an organic solvent, whereby the lithography properties are improved. In addition, when Rd ⁴ is an aromatic group, in lithography using EUV or the like as an exposure light source, the resist composition is excellent in light absorption efficiency, and sensitivity and lithography characteristics are good.

In formula (d1-3), Yd ¹ represents a single bond or a divalent linking group.
The divalent linking group in Yd ¹ is not particularly limited, but may be a divalent hydrocarbon group (aliphatic hydrocarbon group or aromatic hydrocarbon group) which may have a substituent, or a hetero atom containing 2 Valent linking groups and the like. These may be the same as those exemplified in the description of the divalent linking group of Ya ²¹ in the formula (a2-1).
Yd ¹ is preferably a carbonyl group, an ester bond, an amide bond, an alkylene group, or a combination thereof. The alkylene group is preferably a linear or branched alkylene group, and more preferably a methylene group or an ethylene group.

  Preferred specific examples of the anion moiety of the component (d1-3) are shown below.

..Cation part In the formula (d1-3), M ^{m +} is an m-valent organic cation, and is the same as M ^{m +} in the formula (d1-1).
As the component (d1-3), one type may be used alone, or two or more types may be used in combination.

As the component (D1), only one of the above components (d1-1) to (d1-3) may be used, or two or more may be used in combination.
The content of the component (D1) is preferably 0.5 to 10 parts by mass, more preferably 0.5 to 8 parts by mass, with respect to 100 parts by mass of the component (A). More preferably, it is part by mass.
When the content of the component (D1) is not less than the preferable lower limit value, particularly good lithography characteristics and a resist pattern shape are obtained. On the other hand, when it is not more than the upper limit value, the sensitivity can be maintained well and the throughput is also excellent.

  The manufacturing method of said (d1-1) component and (d1-2) component is not specifically limited, It can manufacture by a well-known method.

  The content of the component (D1) is preferably 0.5 to 10.0 parts by mass and more preferably 0.5 to 8.0 parts by mass with respect to 100 parts by mass of the component (A). 1.0 to 8.0 parts by mass is even more preferable. When it is at least the lower limit of the above range, particularly good lithography properties and resist pattern shape can be obtained. When the amount is not more than the upper limit of the above range, the sensitivity can be maintained satisfactorily and the throughput is excellent.

-(D2) component (D) component may contain the nitrogen-containing organic compound component (henceforth "(D2) component") which does not correspond to the said (D1) component.
The component (D2) is not particularly limited as long as it functions as an acid diffusion controller and does not correspond to the component (D1), and any known component may be used. Of these, aliphatic amines, particularly secondary aliphatic amines and tertiary aliphatic amines are preferred.
An aliphatic amine is an amine having one or more aliphatic groups, and the aliphatic groups preferably have 1 to 12 carbon atoms.
Examples of the aliphatic amine include an amine (alkyl amine or alkyl alcohol amine) or a cyclic amine in which at least one hydrogen atom of ammonia NH ₃ is substituted with an alkyl group or hydroxyalkyl group having 12 or less carbon atoms.
Specific examples of alkylamines and alkyl alcohol amines include monoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine; diethylamine, di-n-propylamine, di- -Dialkylamines such as n-heptylamine, di-n-octylamine, dicyclohexylamine; trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-pentylamine, tri-n-hexylamine , Trialkylamines such as tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine, tri-n-decylamine, tri-n-dodecylamine; diethanolamine, triethanolamine, diisopropanolamine, Li isopropanolamine, di -n- octanol amines, alkyl alcohol amines tri -n- octanol amine. Among these, a trialkylamine having 5 to 10 carbon atoms is more preferable, and tri-n-pentylamine or tri-n-octylamine is particularly preferable.

Examples of the cyclic amine include heterocyclic compounds containing a nitrogen atom as a hetero atom. The heterocyclic compound may be monocyclic (aliphatic monocyclic amine) or polycyclic (aliphatic polycyclic amine).
Specific examples of the aliphatic monocyclic amine include piperidine and piperazine.
As the aliphatic polycyclic amine, those having 6 to 10 carbon atoms are preferable. Specifically, 1,5-diazabicyclo [4.3.0] -5-nonene, 1,8-diazabicyclo [5. 4.0] -7-undecene, hexamethylenetetramine, 1,4-diazabicyclo [2.2.2] octane, and the like.

  Other aliphatic amines include tris (2-methoxymethoxyethyl) amine, tris {2- (2-methoxyethoxy) ethyl} amine, tris {2- (2-methoxyethoxymethoxy) ethyl} amine, tris {2 -(1-methoxyethoxy) ethyl} amine, tris {2- (1-ethoxyethoxy) ethyl} amine, tris {2- (1-ethoxypropoxy) ethyl} amine, tris [2- {2- (2-hydroxy Ethoxy) ethoxy} ethyl] amine, triethanolamine triacetate and the like, and triethanolamine triacetate is preferable.

As the component (D2), an aromatic amine may be used.
Aromatic amines include aniline, pyridine, 4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole or derivatives thereof, diphenylamine, triphenylamine, tribenzylamine, 2,6-diisopropylaniline, N-tert-butoxy. And carbonylpyrrolidine.

(D2) A component may be used independently and may be used in combination of 2 or more type.
(D2) A component is normally used in 0.01-5.0 mass parts with respect to 100 mass parts of (A) component. By setting the content in the above range, the resist pattern shape, the stability over time, and the like are improved.

(D) A component may be used individually by 1 type and may be used in combination of 2 or more type.
In this embodiment, when a resist composition contains (D) component, it is preferable that (D) component is 0.1-15 mass parts with respect to 100 mass parts of (A) component, and 0.3 More preferably, it is -12 mass parts, and it is further more preferable that it is 0.5-12 mass parts.
When it is at least the lower limit of the above range, lithography properties such as LWR are further improved when a resist composition is used. Further, a better resist pattern shape can be obtained. When it is not more than the upper limit of the above range, the sensitivity can be maintained satisfactorily and the throughput is excellent.

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

(F) component:
In the present embodiment, the resist composition may contain a fluorine additive (hereinafter referred to as “component (F)”) in order to impart water repellency to the resist film.
Examples of the component (F) include JP 2010-002870 A, JP 2010-032994 A, JP 2010-277043 A, JP 2011-13569 A, and JP 2011-128226 A. The described fluorine-containing polymer compound can be used.
More specifically, examples of the component (F) include a polymer having a structural unit (f1) represented by the following formula (f1-1). As the polymer, a polymer (homopolymer) consisting only of the structural unit (f1) represented by the following formula (f1-1); the structural unit (f1) represented by the following formula (f1-1) and the above A copolymer with the structural unit (a1); a structural unit (f1) represented by the following formula (f1-1); a structural unit derived from acrylic acid or methacrylic acid; and the structural unit (a1). Copolymer; a copolymer of the structural unit (f1) represented by the following formula (f1-1) and the structural unit (a4) is preferable.
Here, as the structural unit (a1) copolymerized with the structural unit (f1) represented by the following formula (f1-1), 1-ethyl-1-cyclooctyl (meth) acrylate, 2-methyl- 2-adamantyl (meth) acrylate or the structural unit represented by the formula (a1-2-01) is preferred.
The structural unit (a4) copolymerized with the structural unit (f1) represented by the following formula (f1-1) is a structure represented by each of the general formulas (a4-1) to (a4-5). Units are preferred.

［式中、Ｒは前記同様であり、Ｒｆ^１０２およびＲｆ^１０３はそれぞれ独立して水素原子、ハロゲン原子、炭素数１〜５のアルキル基、又は炭素数１〜５のハロゲン化アルキル基を表し、Ｒｆ^１０２およびＲｆ^１０３は同じであっても異なっていてもよい。ｎｆ^１は１〜５の整数であり、Ｒｆ^１０１はフッ素原子を含む有機基である。］

[Wherein, R is the same as defined above, and Rf ¹⁰² and Rf ¹⁰³ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms, Rf ¹⁰² and Rf ¹⁰³ may be the same or different. nf ¹ is an integer of ¹ to 5, and Rf ¹⁰¹ is an organic group containing a fluorine atom. ]

In formula (f1-1), R is the same as described above. R is preferably a hydrogen atom or a methyl group.
In formula (f1-1), examples of the halogen atom for Rf ¹⁰² and Rf ¹⁰³ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable. Examples of the alkyl group having 1 to 5 carbon atoms of Rf ¹⁰² and Rf ¹⁰³ include the same as the alkyl group having 1 to 5 carbon atoms of R, and a methyl group or an ethyl group is preferable. Specific examples of the halogenated alkyl group having 1 to 5 carbon atoms of Rf ¹⁰² and Rf ¹⁰³ include a group in which part or all of the hydrogen atoms of the alkyl group having 1 to 5 carbon atoms are substituted with a halogen atom. Can be mentioned. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is particularly preferable. The inter alia ^{Rf 102} and ^{Rf 103,} a hydrogen atom, a fluorine atom, or an alkyl group of 1 to 5 carbon atoms is preferable, a hydrogen atom, a fluorine atom, a methyl group or an ethyl group, preferred.
In formula (f1-1), nf ¹ is an integer of ¹ to 5, preferably an integer of 1 to 3, and more preferably 1 or 2.

In formula (f1-1), Rf ¹⁰¹ is an organic group containing a fluorine atom, and is preferably a hydrocarbon group containing a fluorine atom.
The hydrocarbon group containing a fluorine atom may be linear, branched or cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms. The carbon number of 1 to 10 is particularly preferable.
The hydrocarbon group containing a fluorine atom preferably has 25% or more of the hydrogen atoms in the hydrocarbon group fluorinated, more preferably 50% or more fluorinated, and 60% or more. Fluorination is particularly preferable because the hydrophobicity of the resist film during immersion exposure is increased.
Among ^these, as ^{Rf 101,} particularly preferably a fluorinated hydrocarbon group having 1 to 6 carbon atoms, a methyl _{group, -CH 2 -CF 3, -CH 2} -CF 2 -CF 3, -CH (CF 3) 2 _{, -CH} 2 _-CH 2 _-CF 3, and most preferably _{-CH 2 -CH 2 -CF 2 -CF 2} -CF 2 -CF 3.

(F) As for the weight average molecular weight (Mw) (polystyrene conversion reference | standard by a gel permeation chromatography), 1000-50000 are preferable, 5000-40000 are more preferable, and 10000-30000 are the most preferable. If it is below the upper limit of this range, it has sufficient solubility in a resist solvent to be used as a resist, and if it is above the lower limit of this range, dry etching resistance and resist pattern cross-sectional shape are good.
The dispersity (Mw / Mn) of the component (F) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5.

(F) A component may be used individually by 1 type and may use 2 or more types together.
(F) A component is normally used in the ratio of 0.5-10 mass parts with respect to 100 mass parts of (A) component.

  In this embodiment, the resist composition further contains miscible additives as desired, such as additional resins for improving the performance of the resist film, dissolution inhibitors, plasticizers, stabilizers, colorants, and antihalation. Agents, dyes and the like can be added and contained as appropriate.

(S) component:
In the present embodiment, the resist composition can be produced by dissolving the material in an organic solvent (hereinafter sometimes referred to as “(S) component”).
As the component (S), any component can be used as long as it can dissolve each component to be used to form a uniform solution. Conventionally, any one of known solvents for chemically amplified resists can be used. Two or more types can be appropriately selected and used.
For example, lactones such as γ-butyrolactone; ketones such as acetone, methyl ethyl ketone (MEK), cyclohexanone, methyl-n-pentyl ketone (2-heptanone), methyl isopentyl ketone; ethylene glycol, diethylene glycol, propylene glycol, di- Polyhydric alcohols such as propylene glycol; compounds having an ester bond such as ethylene glycol monoacetate, diethylene glycol monoacetate, propylene glycol monoacetate, dipropylene glycol monoacetate, the polyhydric alcohols or compounds having the ester bond Monoalkyl ethers such as monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether Derivatives of polyhydric alcohols such as compounds having an ether bond such as propylene glycol monomethyl ether acetate (PGMEA) and propylene glycol monomethyl ether (PGME) among these; cyclic ethers such as dioxane, , Methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, ethyl ethoxypropionate, etc .; anisole, ethyl benzyl ether, cresyl methyl Ether, diphenyl ether, dibenzyl ether, phenetole, butyl phenyl ether, ethylbenzene, diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymene, mesitylene And aromatic organic solvents such as dimethyl sulfoxide (DMSO).
These organic solvents may be used independently and may be used as 2 or more types of mixed solvents.
Of these, PGMEA, PGME, γ-butyrolactone, and EL are preferable.
Moreover, the mixed solvent which mixed PGMEA and the polar solvent is also preferable. The blending ratio (mass ratio) may be appropriately determined in consideration of the compatibility between PGMEA and the polar solvent, preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. It is preferable to be within the range.
More specifically, when EL or cyclohexanone is blended as the polar solvent, the mass ratio of PGMEA: EL or cyclohexanone is preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2. . Moreover, when mix | blending PGME as a polar solvent, the mass ratio of PGMEA: PGME becomes like this. Preferably it is 1: 9-9: 1, More preferably, it is 2: 8-8: 2, More preferably, it is 3: 7-7: 3.
In addition, as the component (S), a mixed solvent of at least one selected from PGMEA and EL and γ-butyrolactone is also preferable. In this case, the mixing ratio of the former and the latter is preferably 70:30 to 95: 5.
(S) The usage-amount of a component is not specifically limited, It is a density | concentration which can be apply | coated to a board | substrate etc., and is suitably set according to a coating film thickness. Generally, it is used so that the solid content concentration of the resist composition is in the range of 1 to 20% by mass, preferably 2 to 15% by mass.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to a following example.

<Manufacture of resin components>
[Synthesis of Copolymer (3)]
A Schlenk tube was charged with 0.194 g (4.58 mmol) of LiCl and 178 g of tetrahydrofuran (THF) under an argon atmosphere and cooled to -78 ° C. After dehydrating and degassing the inside of the tube, 0.92 mL (1.00 mol / L hexane / cyclohexane mixed solution, 0.92 mmol) of sec-BuLi as an anionic polymerization initiator in an argon atmosphere, followed by monomer (m31) ( Styrene) (18.76 mL, 163.23 mmol) was added, followed by stirring at −78 ° C. for 30 minutes. After stirring, 0.19 mL (1.10 mmol) of diphenylethylene (DPE) was added, and stirring was performed at −78 ° C. for 30 minutes. Further, 3.10 mL (19.20 mmol) of monomer (m21) (tert-butyl methacrylate) was added, and the mixture was stirred at −78 ° C. for 180 minutes. Subsequently, 2.25 mL (9.60 mmol) of monomer (m11) was added, and the mixture was stirred at −78 ° C. for 180 minutes.
After stirring, 1.11 mL (27.6 mmol) of methanol was added as a polymerization terminator at −78 ° C. to stop the reaction.
The obtained reaction polymerization liquid was dropped into a large amount of methanol to perform the operation of precipitating the polymer, the precipitated white powder was washed with a large amount of methanol, washed with a large amount of pure water and dried. 20.3 g (yield 93.2%) of the target copolymer (3) was obtained.

About the obtained copolymer (3), the weight average molecular weight (Mw) of standard polystyrene conversion calculated | required by GPC measurement was 27000, and molecular weight dispersion degree (Mw / Mn) was 1.06.
The copolymer composition ratio (ratio (molar ratio) of each structural unit in the structural formula) determined by carbon-13 nuclear magnetic resonance spectrum (600 MHz — ¹³ C-NMR) was 1 / m / n = 85/10/5. It was.
Further, the glass transition temperature (Tg) of the copolymer (3) was determined as a calculated value of the simulation by CAChe. Specifically, it was determined by performing structural optimization using MM geometry (MM2) and PM3 geometry according to CAChe Work System Pro Version 6.1.2.33.

[Synthesis of Copolymer (6)]
A Schlenk tube was charged with 0.239 g (5.63 mmol) of LiCl and 190 g of tetrahydrofuran (THF) under an argon atmosphere and cooled to -78 ° C. After dehydrating and degassing the inside of the tube, under an argon atmosphere, 0.56 mL (1.00 mol / L hexane / cyclohexane mixed solution, 0.56 mmol) of sec-BuLi as an anionic polymerization initiator, followed by monomer (m31) ( Styrene) 10.2 mL (88.91 mmol) was added, followed by stirring at −78 ° C. for 30 minutes. After stirring, 0.12 mL (0.675 mmol) of diphenylethylene (DPE) was added, and stirring was performed at −78 ° C. for 30 minutes. Further, 0.79 mL (4.68 mmol) of monomer (m12) was added and stirred at 0 ° C. for 180 minutes.
After stirring, 2.28 mL (56.2 mmol) of methanol was added as a polymerization terminator at −78 ° C. to stop the reaction.
The obtained reaction polymerization liquid was dropped into a large amount of methanol to perform the operation of precipitating the polymer, the precipitated white powder was washed with a large amount of methanol, washed with a large amount of pure water and dried. 8.34 g (yield 83%) of the target copolymer (6) was obtained.

About the obtained copolymer (6), the weight average molecular weight (Mw) of standard polystyrene conversion calculated | required by GPC measurement was 24000, and molecular weight dispersion degree (Mw / Mn) was 1.08.
The copolymer composition ratio (ratio (molar ratio) of each structural unit in the structural formula) determined by carbon-13 nuclear magnetic resonance spectrum (600 MHz — ¹³ C-NMR) was 1 / m = 95/5.
Further, the glass transition temperature (Tg) of the copolymer (6) was determined as a calculated value of simulation by CAChe. Specifically, it was determined by performing structural optimization using MM geometry (MM2) and PM3 geometry according to CAChe Work System Pro Version 6.1.2.33.

[Synthesis of Copolymers (1), (2), (4), (5), (7)]
The copolymer (1) was obtained in the same manner as in [Synthesis of the copolymer (6)] except that the following monomers providing the constituent units constituting the copolymer were used in a predetermined molar ratio. It was.
Copolymers (2), (4), (5) and (7) are the same as those described above except that the following monomers providing the constituent units constituting each copolymer were used in a predetermined molar ratio. It was obtained in the same manner as in [Synthesis of copolymer (3)].
Copolymers (1) to (7) were obtained as block copolymers.

[Synthesis of Copolymers (8) and (9)]
Copolymers (8) and (9) are prepared by using the following monomers that provide constituent units constituting each copolymer in a predetermined molar ratio, and adding dimethyl azobisisobutyrate (V-601) as a polymerization initiator. Then, it was obtained by performing known radical polymerization.
Copolymers (8) and (9) were obtained as random copolymers.

About the obtained copolymers (1)-(9), the weight average molecular weight (Mw) and the molecular weight dispersion degree (Mw / Mn) were calculated | required by GPC measurement (standard polystyrene conversion), respectively.
In addition, for the obtained copolymers (1) to (9), the copolymer composition ratio (ratio (molar ratio) of each structural unit in the structural formula) was determined using the carbon 13 nuclear magnetic resonance spectrum (600 MHz — ¹³ C). -NMR).

  Moreover, about the obtained copolymers (1)-(9), the glass transition temperature (Tg) was calculated | required as a calculated value of the simulation by CAChe, respectively. Specifically, it was determined by performing structural optimization using MM geometry (MM2) and PM3 geometry according to CAChe Work System Pro Version 6.1.2.33. These results are also shown in Table 1.

<Preparation of pattern thickening polymer composition>
Each component shown in Table 2 was mixed and dissolved to prepare a pattern thickening polymer composition (hereinafter also simply referred to as “polymer composition”). All polymer compositions were prepared with a total solid content concentration (total mass excluding solvent) of 1.5% by mass.

Each abbreviation in Table 2 has the following meaning. Moreover, the numerical value in [] is a compounding quantity (mass part).
(X) -1 to (X) -9: Corresponding to the copolymers (1) to (9), respectively.
(S) -1: Mixed solvent of butyl acetate / gamma butyrolactone = 99.5 / 0.5 (mass ratio).
(S) -2: butyl acetate.

<Preparation of resist composition>
Each component shown in Table 3 was mixed and dissolved to prepare a chemically amplified resist composition.

Each abbreviation in Table 2 has the following meaning. Moreover, the numerical value in [] is a compounding quantity (mass part).
(A) -1: a polymer compound represented by the following chemical formula (A) -1. The weight average molecular weight (Mw) in terms of standard polystyrene determined by GPC measurement is 10,000, and the molecular weight dispersity (Mw / Mn) is 1.56. ^The copolymer composition ratio (ratio of each structural unit in the structural formula (molar ratio)) determined by ¹³ C-NMR is 1 / m / n / o / p = 30/10/20/30/10.

(B) -1: An acid generator composed of a compound represented by the following chemical formula (B) -1.
(D) -1: An acid diffusion controller comprising a compound represented by the following chemical formula (D) -1.
(F) -1: A fluorine-containing polymer compound represented by the following chemical formula (F) -1. The weight average molecular weight (Mw) in terms of standard polystyrene determined by GPC measurement is 15000, and the molecular weight dispersity (Mw / Mn) is 1.78. ^The copolymer composition ratio (ratio (molar ratio) of each structural unit in the structural formula) determined by ¹³ C-NMR is 1 / m = 50/50.
(S) -3: A mixed solvent of propylene glycol monomethyl ether acetate / propylene glycol monomethyl ether / cyclohexanone = 45/30/25 (mass ratio).

<Formation of resist pattern>
By the following series of steps A, B, C, and D, a resist pattern having a thick resist pre-pattern was formed.

[Step A]
An organic antireflection film composition “ARC-29A” (trade name, manufactured by Brewer Science Co., Ltd.) was applied onto a 12-inch silicon wafer using a spinner, and baked on a hot plate at 205 ° C. for 60 seconds. By drying, an organic antireflection film having a film thickness of 89 nm was formed, and a support was produced.
Next, the chemical amplification resist composition is applied onto the organic antireflection film using a spinner, and prebaked (PAB) is performed on a hot plate at a temperature of 110 ° C. for 60 seconds. By drying, a resist film having a thickness of 90 nm was formed.
Next, an ArF excimer laser (193 nm) is selectively applied to the resist film via the mask pattern (6% halftone) of the following target (1) using an exposure apparatus NSRX609B (Nikon Corporation; NA 1.07, Annular). Irradiated.
Target (1): elliptical hole pattern elliptical hole diameter minor axis direction (X direction) 65 nm (Pitch: 110 nm)
Long axis direction (Y direction) 174 nm (Pitch: 330 nm)
Subsequently, a post-exposure heating (PEB) treatment was performed under conditions of a temperature of 85 ° C. and 60 seconds.
Subsequently, the solvent development for 13 seconds was performed using butyl acetate, and it sprinkled off and dried.
Then, the baking process (post-baking) for 60 second was performed at the temperature of 110 degreeC.
As a result, a hole pattern (a solvent-developed negative resist prepattern with a carboxy group exposed on the surface) was formed as a resist prepattern.

[Step B]
Next, the polymer composition of each example was apply | coated using the spinner so that the whole said resist pre pattern might be coat | covered on the support body in which the said resist pre pattern was formed, and the polymer film was formed. The coating thickness of this polymer film was an average of 60 nm.

[Step C]
Next, the resist prepattern and the polymer film covering the resist prepattern were heated at a temperature (shrink bake temperature) of 100 ° C. for 60 seconds.

[Step D]
Next, solvent development was performed for 13 seconds using butyl acetate.
As a result, a fine hole pattern in which the resist pre-pattern was thickened and the hole diameter was reduced was formed.

<Evaluation of the width of the thickened portion (shrink volume: SV)>
Each resist pre-pattern and each hole pattern after step D are observed from above the pattern with a length measurement SEM (scanning electron microscope, acceleration voltage 500 V, trade name: CG5000, manufactured by Hitachi High-Technologies Corporation) The hole diameter in the pattern of (1) was measured.

  The ratio of the shrink volume in the X direction to the shrink volume in the Y direction (Y direction / X direction) was determined for the elliptical hole portion in each hole pattern. The results are shown in Table 4.

  In Table 4, from the comparison between Examples 1 to 4 and Comparative Example 1, the comparison between Example 5 and Comparative Example 2, and the comparison between Example 6 and Comparative Example 3, the resist pattern forming method to which the present invention was applied was used. According to this, it can be confirmed that a finer pattern can be formed in a good shape.

1 ... support,
2 ... resist pre-pattern,
3 ... polymer film,
3a: developer insoluble layer,
4 ... resist pattern

Claims (8)

A method of forming a resist pattern with a thickened resist pre-pattern,
Forming a resist prepattern having a polar group exposed on the surface thereof on the support; and
Step B for forming a polymer film by applying a polymer composition for pattern thickening on a support on which the resist prepattern is formed so as to cover the resist prepattern;
Forming a developer insoluble layer on the surface of the resist prepattern; and
Developing the resist prepattern having the developer-insoluble layer formed on its surface and the polymer film covering the resist prepattern to form a resist pattern having a thickened resist prepattern; and
Have
The pattern thickening polymer composition contains a copolymer having a first structural unit, a second structural unit, and a third structural unit,
The first structural unit is a structural unit having a thickening function of the resist pre-pattern,
The resist pattern forming method, wherein the second structural unit and the third structural unit satisfy the following formula (α).
Glass transition temperature (Tg ₂ ) <Glass transition temperature (Tg ₃ ) (α)
Tg ₂ : Glass transition temperature of homopolymer consisting of repeating structure of the second structural unit Tg ₃ : Glass transition temperature of homopolymer consisting of repeating structure of the third structural unit   2. The resist pattern forming method according to claim 1, wherein a ratio of the first structural unit included in the copolymer is 1 to 50 mol% of all structural units constituting the copolymer. The resist pattern forming method according to claim 1, wherein the second structural unit includes a structural unit represented by the following general formula (u2-1).

[In formula, R is a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 halogenated alkyl group. Vx ⁰² is a divalent linking group or a single bond. Rx ² is may have a substituent hydrocarbon group. ] The first structural unit has a neutralizing group;
In the step C, the neutralizing group of the first structural unit and the polar group exposed on the surface of the resist prepattern are neutralized to form a developer insoluble layer on the resist prepattern surface. The resist pattern formation method as described in any one of Claims 1-3. The resist pattern forming method according to claim 4, wherein the first structural unit includes a structural unit represented by the following general formula (u1-1-1).

[In formula, R is a hydrogen atom, a C1-C5 alkyl group, or a C1-C5 halogenated alkyl group. Vx ⁰¹ is a divalent hydrocarbon group having an ether bond or an amide bond, a divalent aromatic hydrocarbon group, or a single bond. Yx ⁰¹ is a single bond or a divalent linking group. Rx ¹ is an organic group containing a neutralizing group. ] A polymer composition for pattern thickening used to thicken a resist pre-pattern with exposed polar groups on the surface,
Containing a copolymer having a first structural unit, a second structural unit, and a third structural unit;
The first structural unit is a structural unit having a thickening function of the resist pre-pattern,
The pattern-thickening polymer composition, wherein the second structural unit and the third structural unit satisfy the following formula (α).
Glass transition temperature (Tg ₂ ) <Glass transition temperature (Tg ₃ ) (α)
Tg ₂ : Glass transition temperature of homopolymer consisting of repeating structure of the second structural unit Tg ₃ : Glass transition temperature of homopolymer consisting of repeating structure of the third structural unit A method of forming a resist pattern with a thickened resist pre-pattern,
Forming a resist prepattern having a polar group exposed on the surface thereof on the support; and
Step B for forming a polymer film by applying a polymer composition for pattern thickening on a support on which the resist prepattern is formed so as to cover the resist prepattern;
Forming a developer insoluble layer on the surface of the resist prepattern; and
Developing the resist prepattern having the developer-insoluble layer formed on its surface and the polymer film covering the resist prepattern to form a resist pattern having a thickened resist prepattern; and
Have
The pattern thickening polymer composition contains a copolymer having a fourth structural unit and a fifth structural unit,
The fourth structural unit is a structural unit having a thickening function of the resist pre-pattern,
The method of forming a resist pattern, wherein the fifth structural unit has a glass transition temperature of a homopolymer having a repeating structure of less than 109 ° C. A polymer composition for pattern thickening used to thicken a resist pre-pattern with exposed polar groups on the surface,
Containing a copolymer having a fourth structural unit and a fifth structural unit;
The fourth structural unit is a structural unit having a thickening function of the resist pre-pattern,
The fifth constituent unit is a polymer composition for pattern thickening, characterized in that the homopolymer having the repeating structure has a glass transition temperature of less than 109 ° C.

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