JP2020023636A - Polymer, resist composition, and manufacturing method of substrate with pattern formed - Google Patents

Abstract

To provide a polymer and a resist composition, good in developer dissolubility.SOLUTION: There is provided a polymer having a constitutional unit represented by the formula 1. Ris H, or a methyl group, R, R, and Rare a combination of an alkoxy group, an alkyl group, H, Zis a bivalent chain hydrocarbon group having 1 to 20 C atoms, a bivalent cyclic hydrocarbon group which may have a hetero atom, or a single bond, Zis a bivalent chain hydrocarbon group, Zis a chain hydrocarbon group which may have a hetero atom together with C to which (RRR)C- binds, and n is an integer of 0 to 3.SELECTED DRAWING: None

Description

  The present invention relates to a polymer, a resist composition containing the polymer, and a method for producing a substrate on which a pattern is formed using the resist composition.

As a resist composition that can suitably cope with shortening of the wavelength of irradiation light and miniaturization of patterns in lithography technology, including a resist polymer from which an acid leaving group is eliminated by the action of an acid, and a photoacid generator A so-called chemically amplified resist composition has been proposed, and its development and improvement have been promoted.
Patent Document 1 discloses that, as a structural unit having an acid leaving group, an ester moiety is a hydrocarbon group containing a specific alicyclic hydrocarbon group (adamantyl group, cyclopentyl group), and an oxygen atom forming an ester bond A resist polymer having a (meth) acrylic ester unit having a tertiary carbon atom at a bonding site between the compound and alicyclic hydrocarbon group is described.

JP 2016-212213 A

In recent years, the miniaturization of patterns has been rapidly progressing, and there has been a keen demand for the development of resist materials capable of improving various lithography characteristics such as sensitivity, pattern formability, and line width roughness (LWR) more than ever.
In a resist composition containing a polymer having an acid leaving group, the sensitivity at the time of pattern formation can be improved by increasing the reactivity between the acid leaving group and the acid (acid reactivity).
However, a polymer using a structural unit having an acid-eliminable group described in Patent Document 1 may have insufficient solubility in a developer even if the acid reactivity is good.
An object of the present invention is to provide a polymer having good solubility in a developing solution, a resist composition containing the polymer, and a method for producing a substrate on which a pattern is formed using the resist composition.

The present invention has the following aspects.
[1] A polymer having a structural unit represented by the following formula (1).

[In formula (1), R ¹ is a hydrogen atom or a methyl group, one of R ²¹ , R ²² , and R ²³ is an alkoxy group having 1 to 20 carbon atoms, and the other is an alkoxy group having 1 to 20 carbon atoms. An alkyl group, the other one is a hydrogen atom, an alkoxy group having 1 to 20 carbon atoms or an alkyl group having 1 to 20 carbon atoms, and Z ¹ is a substituted or unsubstituted divalent chain having 1 to 20 carbon atoms. hydrocarbon group, having 1 to 20 carbon atoms, a substituted or unsubstituted, divalent may have a hetero atom cyclic hydrocarbon group or a single bond, Z ^2, is 2 to 12 carbon atoms A valent chain hydrocarbon group, Z ³ is a cyclic hydrocarbon group which may have a heteroatom having 3 to 10 carbon atoms together with a carbon atom to which (R ²¹ R ²² R ²³ ) C— is bonded. And n is an integer of 0 to 3. ]
[2] The polymer according to [1], further comprising a structural unit having a lactone skeleton.
[3] The polymer according to [1] or [2], wherein the content of the structural unit represented by the formula (1) is 10 mol% or more with respect to all the structural units.
[4] A resist composition comprising the polymer according to any one of [1] to [3] and a compound that generates an acid upon irradiation with actinic rays or radiation.
[5] a step of applying the resist composition of the above [4] on a surface to be processed of a substrate to form a resist film, a step of exposing the resist film, and a step of developing the exposed resist film with a developing solution And a step of developing the substrate using the method.

  According to the present invention, it is possible to provide a polymer having good solubility in a developing solution, a resist composition containing the polymer, and a method for producing a substrate on which a pattern is formed using the resist composition.

The following definitions of terms apply throughout the present specification and claims.
In the present specification, “structural unit” means an atomic group formed by a polymerization reaction of a monomer.
In the present specification, “(meth) acrylic acid” means acrylic acid or methacrylic acid.
In this specification, the structural unit represented by the formula (1) is referred to as a structural unit (1). Structural units represented by other formulas are similarly described.
In this specification, the compound represented by the formula (2) is referred to as a compound (2). The same applies to compounds represented by other formulas.
In this specification, the monomer represented by the formula (m1) is referred to as a monomer (m1). The same applies to monomers represented by other formulas.

<Polymer>
The polymer of the present embodiment (hereinafter, also referred to as “polymer (A)”) has the following structural unit (1). Structural unit (1) is a structural unit having a specific acid leaving group. The polymer (A) is suitable as a resist polymer.
The polymer (A) is preferably a copolymer having two or more types of structural units.
The polymer (A) preferably contains one or more structural units other than the structural unit (1), and more preferably 1 to 5 other structural units.
As other structural units, known structural units in a chemically amplified resist composition can be used. For example, a structural unit having a lactone skeleton and a structural unit having a hydrophilic group are exemplified.

[Structural unit (1)]
The structural unit (1) is represented by the following formula (1). The structural unit (1) is a structural unit formed by cleavage of an ethylenic double bond of a monomer (hereinafter, referred to as monomer (1)) that is a (meth) acrylate compound.

In the formula (1), R ¹ is a hydrogen atom or a methyl group.
One of R ²¹ , R ²² , and R ²³ is an alkoxy group having 1 to 20 carbon atoms, another is an alkyl group having 1 to 20 carbon atoms, the other is a hydrogen atom, and 1 to 20 carbon atoms. Or an alkyl group having 1 to 20 carbon atoms.

It is preferable that there is one alkyl group among R ²¹ , R ²² , and R ^{23 from} the viewpoint that higher solubility in an alkali developer is easily obtained.
That is, it is preferable that one of R ²¹ , R ²² and R ²³ is an alkoxy group, the other one is an alkyl group, and the other one is a hydrogen atom or an alkoxy group.

The alkoxy group is preferably linear or branched. The carbon number of the alkoxy group is preferably from 1 to 4, more preferably from 1 to 3, and even more preferably 1 or 2.
The alkyl group may be linear, branched or cycloalkyl. The carbon number of the linear or branched alkyl group is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 or 2.
The cycloalkyl group preferably has 3 to 8 carbon atoms, more preferably 5 or 6.

Z ¹ is a substituted or unsubstituted divalent chain hydrocarbon group having 1 to 20 carbon atoms, a substituted or unsubstituted divalent hydrocarbon group having 1 to 20 carbon atoms which may have a hetero atom. Or a single bond.
When Z ¹ is a divalent chain hydrocarbon group, it may be linear or branched. As the divalent chain hydrocarbon group, an alkylene group is preferable. Examples of the substituent include -O-, -S-, -NH-, and -PH-. The number of carbon atoms is preferably 1 to 10, more preferably 1 to 6.
When Z ¹ is a divalent cyclic hydrocarbon group, it may be monocyclic or polycyclic. As the cyclic hydrocarbon group, a cyclic saturated hydrocarbon group is preferable. Examples of the hetero atom include a nitrogen atom, an oxygen atom, a sulfur atom, and a phosphorus atom. A substituent may be bonded to a carbon atom constituting the ring. Examples of the substituent include an alkyl group having 1 to 10 carbon atoms. The alkyl group may be linear or branched.
Z ¹ is preferably a single bond from the viewpoint of increasing the solubility of the resist material in a developing solution.

Z ² is a divalent chain hydrocarbon group having 1 to 12 carbon atoms. It may be linear or branched. As the chain hydrocarbon group, an alkylene group is preferable. As for carbon number, 1-6 are preferred, and 1-3 are more preferred.
n is an integer of 0 to 3, preferably 0 to 2, and more preferably 0 or 1.

Z ³ is an atomic group forming a cyclic hydrocarbon group which may have a hetero atom having 3 to 10 carbon atoms together with the carbon atom to which (R ²¹ R ²² R ²³ ) C— is bonded. is there. The cyclic hydrocarbon group may be monocyclic or polycyclic. As the cyclic hydrocarbon group, a cyclic hydrocarbon group (having no hetero atom) composed of a hydrocarbon is preferable.
The carbon number of the cyclic hydrocarbon group includes the carbon atom to which (R ²¹ R ²² R ²³ ) C— is bonded.
Examples of the cyclic hydrocarbon group composed of a monocyclic hydrocarbon having 3 to 10 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and cyclopentenyl. Group, cyclohexenyl group, cyclooctadienyl group and the like. Among these, a cyclopentyl group and a cyclohexyl group are preferred from the viewpoint of availability.
Examples of the cyclic hydrocarbon group composed of a polycyclic hydrocarbon having 3 to 10 carbon atoms include bicyclo [4.3.0] nonanyl, naphthalenyl, decahydronaphthalenyl, bornyl, isobornyl, and norbornyl. Group, adamantyl group, noradamantyl group and the like. Among these, a norbornyl group and an adamantyl group are preferred from the viewpoint of availability.

The structural unit (1) in the polymer (A) may be one type or two or more types. From the viewpoint of balance with the structural units other than the structural unit (1), the structural unit (1) is preferably three or less.
The content of the structural unit (1) with respect to all the structural units of the polymer (A) is preferably at least 10 mol%, more preferably at least 20 mol%, even more preferably at least 30 mol%. When the ratio is equal to or more than the lower limit, the effect of improving solubility in an organic solvent used as a resist solvent is excellent.
In light of the balance of resist performance, the content of the structural unit (1) is preferably equal to or less than 80 mol%, more preferably equal to or less than 70 mol%, and still more preferably equal to or less than 60 mol%.

Preferred embodiments of the structural unit (1) include the following.
R ¹ is a hydrogen atom or a methyl group, and Z ³ is an atomic group forming a cyclopentyl group, a cyclohexyl group, a norbornyl group, or an adamantyl group together with a carbon atom to which (R ²¹ R ²² R ²³ ) C— is bonded. R ²¹ , R ²² and R ²³ are selected from the group consisting of any combination of a methoxy group, a methyl group and a hydrogen atom, any combination of two methoxy groups and a methyl group, or any combination of a methoxy group and two methyl groups; A structural unit wherein Z ¹ is a single bond and n = 0.

The monomer (1) is obtained, for example, by reacting a hydroxy compound (4) represented by the following formula (4) with a (meth) acrylic acid chloride to form a (meth) compound represented by the following formula (5). It can be produced by a method for obtaining an acrylate (5).
The hydroxy compound (4) can be produced by reacting an ester compound (2) represented by the following formula (2) with a compound (3) represented by the following formula (3).

In the formula (2), R ²¹ , R ²² and R ²³ are the same as R ²¹ , R ²² and R ²³ in the formula (1) including preferred embodiments.
In the formula (2), R ¹¹ is an alkyl group. The alkyl group may be linear, branched, or a cycloalkyl group. Examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an s-butyl group, a t-butyl group, a cyclopentyl group, and a cyclohexyl group. Among these, a methyl group, an ethyl group, a propyl group, and an isopropyl group are preferable in terms of availability.

In the formula (3), Y ¹ is an alkylene group having 2 to 9 carbon atoms or a cycloalkylene group, and M ² and M ³ are each independently MgX (X is a halogen atom).
The alkylene group for Y ¹ may be linear or branched. For example, ethylene group, propylene group, isopropylene group, butylene group, pentylene group, hexylene group and the like can be mentioned. Examples of the cycloalkylene group include a cyclohexylene group. Among these, a butylene group and a pentylene group are preferable from the viewpoint of availability.

In the reaction between the compound (2) and the compound (3), the amount of the compound (3) is not particularly limited. However, from the viewpoint of obtaining the compound (4) in good yield, 0 is used per mole of the compound (2). It is preferably at least 0.5 mol, and more preferably at most 5 mol from the viewpoint of suppressing a side reaction and a load on a treatment step after the reaction.
Compound (3) is preferably 0.5 to 5 mol, more preferably 0.8 to 4 mol, and still more preferably 1 to 3 mol, per 1 mol of compound (2).

  In the reaction between compound (2) and compound (3), a solvent may be used. The solvent is not particularly limited as long as it does not react with the compound (3). For example, aromatic solvents such as toluene and xylene: hydrocarbon solvents such as hexane, heptane, octane, and cyclohexane: ether solvents such as diethyl ether, diisopropyl ether, t-butyl methyl ether, tetrahydrofuran, and dioxane. . These solvents may be used alone or as a mixture of two or more. The amount of the solvent used can be appropriately set.

The reaction temperature of the compound (2) with the compound (3) may be a temperature in a usual cyclization reaction using the compound (3). From the viewpoint of shortening the reaction time, the temperature is preferably -100 ° C or higher, more preferably -80 ° C or higher. Further, the temperature is preferably 100 ° C. or lower, more preferably 80 ° C. or lower, from the viewpoint of suppressing problems such as side reactions.
The reaction time varies depending on the reaction temperature and the like, and may be appropriately determined. For example, it is preferably about 0.5 to 30 hours.

The compound (4) obtained by reacting the compound (2) with the compound (3) may be purified.
The purification method can be appropriately combined with known purification methods such as washing with alkaline water, washing with water, distillation, crystallization, and filtration in consideration of the physical properties of the product, types and amounts of raw materials, types of solvents, and the like.

Compound (5) is obtained by reacting compound (4) with (meth) acrylic acid chloride.
As the (meth) acrylic acid chloride, a commercially available product or a product synthesized separately may be used. The amount of the (meth) acrylic acid chloride to be used is not particularly limited, but is preferably 0.5 mol or more per 1 mol of the compound (4) from the viewpoint of obtaining the compound (5) in good yield. From the viewpoint of preventing polymerization derived from chloride, the amount is preferably 3 mol or less.
Acrylic acid chloride is preferably 0.5 to 3 mol, more preferably 0.7 to 2.5 mol, and even more preferably 0.9 to 2 mol, per 1 mol of compound (4).

In the reaction of compound (4) with (meth) acrylic acid chloride, a base may be added from the viewpoint of obtaining compound (5) in good yield. Examples of the base include n-butyllithium, s-butyllithium, t-butyllithium, methylmagnesium bromide, t-butylmagnesium chloride, triethylamine, 4-dimethylaminopyridine, 1,8-diazabicyclo [5.4.0. ] -7-undecene and the like.
The amount of the base to be used is preferably 0.1 mol or more per 1 mol of compound (4) from the viewpoint of the reaction yield, and is preferably 3 mol or less from the viewpoint of suppressing the load on the treatment step after the reaction.
The base is preferably 0.1 to 3 mol, more preferably 0.5 to 2 mol, per 1 mol of the compound (4).

  In the reaction between compound (4) and (meth) acrylic acid chloride, a solvent may be used. The solvent is not particularly limited as long as it does not react with the (meth) acrylic acid chloride. For example, aromatic solvents such as toluene and xylene: hydrocarbon solvents such as hexane, heptane, octane, and cyclohexane: ether solvents such as diethyl ether, diisopropyl ether, t-butyl methyl ether, tetrahydrofuran, and dioxane. . These solvents may be used alone or as a mixture of two or more. The amount of the solvent used can be appropriately set.

  In the reaction between compound (4) and (meth) acrylic acid chloride, a polymerization inhibitor may be present in the reaction system in order to suppress polymerization. Examples of the polymerization inhibitor include, but are not particularly limited to, hydroquinone monomethyl ether, hydroquinone, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, phenothiazine, and copper salt. These may be used alone or in combination of two or more.

The reaction temperature in the step of reacting the compound (4) with (meth) acrylic acid chloride may be a temperature used in ordinary esterification. From the viewpoint of shortening the reaction time, the temperature is preferably -100 ° C or higher, more preferably -80 ° C or higher. Further, from the viewpoint of suppressing problems such as side reactions and polymerization, the temperature is preferably 65 ° C or lower, more preferably 45 ° C or lower.
The reaction time varies depending on the reaction temperature and the like, and may be appropriately determined. For example, about 0.5 to 20 hours is preferable.

  It is preferable to purify the compound (5) obtained by reacting the compound (4) with (meth) acrylic acid chloride. The compound (5) can be purified by a known purification method such as washing with alkali, washing with water, distillation, crystallization, or filtration in consideration of the physical properties of the product, the raw materials, the type and amount of the base, and the type of the solvent. They can be appropriately combined.

Preferred embodiments of the method for producing the compound (5) include the following embodiments (1) to (3). Hereinafter, the methoxy group may be described as "MeO-" and the ethoxy group may be described as "EtO-".
Aspect (1): The following ester compound (2-1) is reacted with a compound (3-1) in which Y ¹ is a butylene group and M ² and M ³ are each MgBr in the formula (3). A method of obtaining the following hydroxy compound (4-1) and reacting the hydroxy compound (4-1) with (meth) acrylic acid chloride to obtain the following compound (5-1).
Compound (3-1) is a reaction product of 1,4-dibromobutane and metallic Mg.

  Aspect (2): The following compound (3-1) is reacted with the following ester compound (2-2) to obtain the following hydroxy compound (4-2), and the hydroxy compound (4-2) and (meth) A method of reacting with acrylic acid chloride to obtain the following compound (5-2).

  Aspect (3): The following ester compound (2-3) is reacted with the compound (3-1) to obtain a hydroxy compound (4-3), and the hydroxy compound (4-3) and (meth) acryl A method of reacting with an acid chloride to obtain the following compound (5-3).

[Structural unit having lactone skeleton]
The polymer (A) preferably has, as a structural unit other than the structural unit (1), one or more structural units having a lactone skeleton.
The lactone skeleton means a monocyclic or polycyclic atomic group including a ring having -OC (= O)-. The ring having -OC (= O)-may be a ring having -C (= O) -OC (= O)-.
The lactone skeleton is preferably a 4- to 20-membered ring, more preferably a 5- to 10-membered ring.
The lactone skeleton may be a single ring having only a lactone ring, or an aromatic or non-aromatic hydrocarbon ring or heterocyclic ring may be fused to the lactone ring.

  As the monomer having a lactone skeleton, a (meth) acrylate compound is preferable. In particular, a (meth) acrylate having a substituted or unsubstituted δ-valerolactone ring and a (meth) acrylate having a substituted or unsubstituted γ-butyrolactone ring, from the viewpoint of excellent adhesion to a substrate or the like. At least one selected from the group consisting of is preferred, and a monomer having an unsubstituted γ-butyrolactone ring is particularly preferred.

Specific examples of the monomer having a lactone skeleton include β- (meth) acryloyloxy-β-methyl-δ-valerolactone, 4,4-dimethyl-2-methylene-γ-butyrolactone, β- (meth) acryloyl Oxy-γ-butyrolactone, β- (meth) acryloyloxy-β-methyl-γ-butyrolactone, α- (meth) acryloyloxy-γ-butyrolactone, 2- (1- (meth) acryloyloxy) ethyl-4-butanolide , Pantoyl lactone (meth) acrylate, 5- (meth) acryloyloxy-2,6-norbornanecarboractone, 8-methacryloxy-4-oxatricyclo [5.2.1.0 ^2,6 ] decane-3 - one, 9-methacryloxy-4-oxatricyclo [5.2.1.0 ^{2, 6]} decan-3-one, etc. mentioned et al That.
As the monomer having a lactone skeleton, one type may be used alone, or two or more types may be used in combination.
When the polymer (A) contains a structural unit having a lactone skeleton, its content is preferably at least 20 mol%, more preferably at least 25 mol%, based on all the structural units. Further, from the viewpoint of sensitivity and resolution, it is preferably at most 70 mol%, more preferably at most 60 mol%, even more preferably at most 50 mol%.

[Structural unit having hydrophilic group]
The polymer (A) may have one or more structural units having a hydrophilic group as structural units other than the structural unit (1) and the structural unit having a lactone skeleton.
The “hydrophilic group” in the present specification is at least one selected from the group consisting of —C (CF ₃ ) ₂ —OH, a hydroxy group, a cyano group, a methoxy group, a carboxy group, and an amino group.
Among these, the polymer applied to the pattern forming method for exposing with light having a wavelength of 250 nm or less preferably has a hydroxy group or a cyano group.
As the monomer having a hydrophilic group, a (meth) acrylate compound is preferable.

Specific examples of the monomer having a hydrophilic group include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxy-n- (meth) acrylate. -Propyl, 4-hydroxybutyl (meth) acrylate, 3-hydroxyadamantyl (meth) acrylate, 2- or 3-cyano-5-norbornyl (meth) acrylate, 2-cyanomethyl-2-adamantyl (meth) acrylate, and the like Is mentioned.
From the viewpoint of adhesion to a substrate or the like, 3-hydroxyadamantyl (meth) acrylate, 3,5-dihydroxyadamantyl (meth) acrylate, 2- or 3-cyano-5-norbornyl (meth) acrylate, 2-cyanomethyl- 2-adamantyl (meth) acrylate and the like are preferred.
As the monomer having a hydrophilic group, one type may be used alone, or two or more types may be used in combination.
When the polymer (A) contains a structural unit having a hydrophilic group, the content is preferably from 5 to 30 mol%, more preferably from 10 to 25 mol%, based on the total structural units in view of the rectangularity of the resist pattern. More preferred.

[Structural unit having another acid leaving group]
The polymer (A) may have, as another structural unit, one or more structural units having another acid-eliminable group, which does not correspond to the structural unit (1).
The structural unit (1) is preferably at least 20 mol%, more preferably at least 40 mol%, and more preferably 50 mol%, based on the total of the structural unit having another acid-eliminable group and the structural unit (1). The above is more preferred. It may be 100 mol%.

  As a preferred embodiment of the polymer (A), the constitutional unit (1) is 15 to 80 mol% and the constitutional unit having a lactone skeleton is 20 to 70 mol%, based on all the constitutional units. 70-100 mol% of a polymer.

The polymer (A) can be produced, for example, by a solution polymerization method in which a monomer is radically polymerized using a polymerization initiator in the presence of a polymerization solvent.
The weight average molecular weight of the polymer (A) is preferably from 1,000 to 100,000, more preferably from 3,000 to 50,000, and still more preferably from 5,000 to 30,000.

<Resist composition>
The resist composition preferably contains the polymer (A), a resist solvent, and a compound that generates an acid upon irradiation with actinic rays or radiation. One kind of the polymer (A) may be used alone, or two or more kinds may be used in combination.
The content of the polymer (A) with respect to the resist composition (excluding the solvent) is not particularly limited, but is preferably 70 to 99.9% by mass.

Examples of the resist solvent include cyclopentanone, cyclohexanone, propylene glycol monomethyl ether acetate (PGMEA), and propylene glycol monomethyl ether (PGME). One resist solvent may be used, or two or more resist solvents may be used in combination.
The amount of the resist solvent used depends on the thickness of the resist film to be formed, but is preferably in the range of 100 to 10,000 parts by mass per 100 parts by mass of the polymer (A).

The compound that generates an acid upon irradiation with actinic rays or radiation can be arbitrarily selected from those that can be used as a photoacid generator of a chemically amplified resist composition. One photoacid generator may be used alone, or two or more photoacid generators may be used in combination.
Examples of the photoacid generator include an onium salt compound, a sulfonimide compound, a sulfone compound, a sulfonate compound, a quinonediazide compound, and a diazomethane compound.
The amount of the photoacid generator to be used is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the polymer (A).

  The resist composition may contain a nitrogen-containing compound, an acid compound (organic carboxylic acid, oxo acid of phosphorus or a derivative thereof), a surfactant, other quencher, a sensitizer, an antihalation agent, a storage stabilizer, if necessary. And various additives such as an antifoaming agent. As the additive, those known in the art can be used.

<Method of manufacturing substrate on which pattern is formed>
An example of a method for manufacturing a substrate on which a pattern is formed will be described.
First, a resist composition is applied to the surface of a substrate to be processed such as a silicon wafer by spin coating or the like. Then, the substrate to be processed to which the resist composition has been applied is dried by baking (pre-baking) or the like to form a resist film on the substrate.
Next, the resist film is irradiated with light having a wavelength of 250 nm or less through a photomask to form a latent image (exposure). The irradiation light, KrF excimer laser, ArF excimer laser, _{F 2} excimer laser, the EUV excimer laser Preferably, ArF excimer laser is particularly preferable. Further, an electron beam may be irradiated.
Liquid immersion for irradiating light with a high refractive index liquid such as pure water, perfluoro-2-butyltetrahydrofuran, or perfluorotrialkylamine interposed between the resist film and the final lens of the exposure apparatus. Exposure may be performed.

After exposure, heat treatment is appropriately performed (post-exposure bake, PEB), and a part of the resist film is dissolved by bringing a developer into contact with the resist film. In the positive development process, the exposed portion is dissolved and removed with an alkaline developer.
In the polymer (A), the bond of the acid-labile group is cleaved by the acid generated by the exposure, and the dissolution rate of the exposed portion in the alkali developing solution is increased.
An alkaline aqueous solution is used as the alkaline developer. For example, inorganic alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, and aqueous ammonia; primary amines such as ethylamine and n-propylamine; diethylamine and di-n-butylamine Secondary amines; tertiary amines such as triethylamine and methyldiethylamine; alcoholamines such as dimethylethanolamine and triethanolamine; quaternary ammonium salts such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; Aqueous solutions of cyclic amines such as pichelidine;
After the development, the substrate is appropriately rinsed with pure water or the like. Thus, a resist pattern is formed on the substrate to be processed.
The substrate on which the resist pattern is formed is appropriately heat-treated (post-baked) to strengthen the resist, and selectively dry-etch a portion without the resist.
After the dry etching, the resist is removed with a stripping agent to obtain a substrate on which a fine pattern is formed.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Reaction tracking was performed by gas chromatography.

<Method of measuring weight average molecular weight>
The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer were determined by gel permeation chromatography in terms of polystyrene. The eluent used was tetrahydrofuran (THF).

<Method of measuring copolymer composition ratio>
For the polymers obtained in each example, the composition ratio (unit: mol%) of the structural units based on each monomer was determined by ¹ H-NMR measurement.
In this measurement, an ECS-400 type superconducting FT (Fourier transform) -NMR device manufactured by JEOL Ltd. was used, and about 5% by mass of a sample solution (solvent was deuterated chloroform) was placed in a sample tube having a diameter of 5 mmφ. , observation frequency 400MHz, in the single-pulse ^mode, 1 H
64 integrations were performed. The measurement was performed at a temperature of 60 ° C.

<Evaluation method of developer solubility (method of measuring turbidity)>
Turbidity Th (80) and turbidity Tm (80) were measured using the turbidimeter (Orbeco-Hellige, product name: TB200) by the following measurement method. Th (80) is an index of solubility in a low-polarity organic solvent, and Tm (80) is an index of solubility in a high-polarity organic solvent. Higher turbidity indicates lower solubility in organic solvents. In other words, the higher the turbidity, the higher the polarity and the better the solubility in an alkali developer.

[Method of measuring turbidity Th (80)]
(1) A polymer to be measured is dissolved in PGMEA to prepare a 10% by mass PGMEA solution.
(2) n-heptane is added to the PGMEA solution prepared in the above (1) to form a mixture, and when the turbidity of the mixture becomes 10 NTU, the amount of n-heptane added to the PGMEA solution (Xh % By weight).
(3) An amount of n-heptane corresponding to 80% of the Xh mass% is added to the PGMEA solution prepared in (1) and stirred at 25 ° C. for 4 hours to obtain a measurement solution.
(4) The turbidity of the measurement solution at 25 ° C. is defined as Th (80).
[Method of measuring turbidity Tm (80)]
(5) Methanol is added to the PGMEA solution prepared in the above (1) to form a mixture, and when the turbidity of the mixture becomes 5.0 NTU, the amount of methanol added to the PGMEA solution (Xm mass% ).
(6) An amount of methanol corresponding to 80% of the Xm mass% is added to the PGMEA solution prepared in (1), and the mixture is stirred at 25 ° C. for 4 hours to obtain a measurement solution.
(7) The turbidity of the measurement solution at 25 ° C. is defined as Tm (80).

  In the following Examples and Comparative Examples, monomers (m1) to (m8) represented by the following formulas (m1) to (m8) were used.

<Synthesis example 1>
A monomer (m3) (compound (5-1)) was produced by the method of the above-mentioned embodiment (1).
[Step 1]
2.54 g (63 mmol) of 60% by mass sodium hydride and 50 mL of tetrahydrofuran were added to a glass flask, and cooled to 0 ° C. 5.00 g (42 mmol) of ethyl lactate dissolved in 28 mL of tetrahydrofuran was added, and the mixture was stirred at 0 ° C for 20 minutes. 4.0 mL (63 mmol) of iodomethane was added, and the mixture was stirred at room temperature for 2.5 hours. A saturated ammonium chloride aqueous solution (85 mL) was added to separate the layers. The aqueous layer was extracted three times with 60 mL of diisopropyl ether, and the organic layer was washed with 20 mL of saturated saline. After drying using magnesium sulfate, the solvent was distilled off to obtain 2.97 g of compound (2-1).

[Step 2]
Next, 1.52 g (63 mmol) of shaved magnesium and 25 mL of tetrahydrofuran were added to a glass flask, and 2.7 mL (23 mmol) of 1,4-dibromobutane dissolved in 26 mL of tetrahydrofuran was added at room temperature to 1.3. Dropped in time. Thereafter, the mixture was stirred for 3 hours, cooled to −10 ° C., and 2.97 g (22 mmol) of the compound (2-1) dissolved in 23 mL of tetrahydrofuran was added dropwise in 0.5 hours. After stirring at -10 ° C for 1 hour, the mixture was stirred at room temperature overnight. 50 mL of a 20% by mass aqueous solution of ammonium chloride was added to separate the layers. The aqueous layer was extracted twice with 60 mL of ethyl acetate, and the organic layer was washed by adding 20 mL of a saturated aqueous solution of sodium hydrogen carbonate and subsequently 20 mL of a saturated saline solution. After drying using magnesium sulfate, the solvent was distilled off to obtain 2.80 g of the desired compound.
¹ H-NMR analysis confirmed that the obtained compound was compound (4-1).
¹ H-NMR (270 MHz, CDCl ₃ ): δ 3.38 ppm (s, 3H), 3.23 ppm (q, 1H), 2.11 ppm (s, 1H), 1.84-1.51 ppm (m, 8H) , 1.15 ppm (d, 3H).

[Step 3]
2.80 g (19 mmol) of the compound (4-1) obtained above and 46 mL of tetrahydrofuran were added to a glass flask, and the mixture was cooled to −40 ° C. under a nitrogen flow. 20 mL of n-butyllithium (15% by mass hexane solution, 32 mmol) was added dropwise, and the mixture was stirred at 0 ° C for 1 hour. The mixture was cooled again to −40 ° C., and 4.0 mL (42 mmol) of methacrylic acid chloride was added dropwise, followed by stirring at 0 ° C. for 1.5 hours. After adding 19.45 g of a 10% by mass aqueous solution of lithium hydroxide, the mixture was stirred at 50 ° C. for 2 hours, and then separated. The aqueous layer was extracted three times with 20 mL of ethyl acetate, and the organic layer was washed by adding 30 mL of a saturated aqueous solution of sodium hydrogen carbonate and subsequently 15 mL of a saturated saline solution. After drying using magnesium sulfate, the solvent was distilled off. The obtained crude product was purified by silica gel column chromatography to obtain 3.34 g of the desired compound.
¹ H-NMR analysis confirmed that the obtained compound was compound (5-1).
¹ H-NMR (270 MHz, CDCl ₃ ): δ 6.03 ppm (m, 1H), 5.50 ppm (m, 1H), 4.17 ppm (q, 1H), 3.36 ppm (s, 3H), 1.90 ppm (S, 1H), 2.14-1.56 ppm (m, 8H), 1.09 ppm (d, 3H).

<Synthesis Example 2>
A monomer (m4) (compound (5-2)) was produced by the method of the above-mentioned embodiment (2).
Compound (2-2) was obtained in the same manner as in Step 1 of Synthesis Example 1 except that ethyl lactate was changed to methyl 2-hydroxyisobutyrate.
Compound (4-2) was obtained in the same manner as in Step 2 of Synthesis Example 1 except that compound (2-2) obtained above was used instead of compound (2-1). ¹ H-NMR analysis confirmed that the obtained compound was compound (4-2).
¹ H-NMR (270 MHz, CDCl ₃ ): δ 3.24 ppm (s, 3H), 2.36 ppm (s, 1H), 1.90-1.54 ppm (m, 8H), 1.17 ppm (s, 6H) .

A target compound was obtained in the same manner as in Synthesis Example 1, except that the compound (4-2) obtained above was used instead of the compound (4-1).
^{By 1} H-NMR analysis, it was confirmed that the obtained compound was compound (5-2).
¹ H-NMR (270 MHz, CDCl ₃ ): δ 6.00 ppm (m, 1H), 5.48 ppm (m, 1H), 3.25 ppm (s, 3H), 1.91 ppm (s, 1H), 2.06 -1.56 ppm (m, 8H), 1.24 ppm (d, 3H).

[Example 1]
Under a nitrogen atmosphere, 16.7 parts by mass of PGMEA was charged into a flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and the temperature of the hot water bath was raised to 80 ° C. while stirring. Thereafter, the following mixture 1 was dropped into the flask from the dropping funnel over 4 hours, and the temperature was kept at 80 ° C. for 3 hours to obtain a reaction solution.
(Composition of mixture 1)
6.80 parts by mass of monomer (m1) (40 mol%),
4.72 parts by mass (20 mol%) of monomer (m2),
8.49 parts by mass (40 mol%) of monomer (m3),
Solvent: 30.0 parts by mass of PGMEA, and polymerization initiator: 1.61 parts by mass of dimethyl-2,2'-azobisisobutyrate (V601 (trade name) manufactured by Wako Pure Chemical Industries, Ltd.).

The resulting reaction solution was added dropwise to an approximately 10-fold amount of a mixed solvent of methanol and water (methanol / water = 80/20 volume ratio) with stirring to obtain a white precipitate. The precipitate was separated by filtration, poured again into the same amount of methanol as described above, and washed with stirring. The precipitate after washing was filtered off to obtain a polymer wet powder. The polymer wet powder was dried at 60 ° C. under reduced pressure for about 36 hours to obtain a dry powdery polymer.
Turbidity of the obtained polymer was measured by the above method. The results are shown in Table 1 (the same applies hereinafter).
Table 2 shows the measurement results of the copolymer composition ratio, weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the obtained polymer (the same applies hereinafter).

  15.0 parts by mass of the polymer in the form of a dry powder obtained above, 105.0 parts by mass of PGMEA, and 0.3 part by mass of triphenylsulfonium triflate as a photoacid generator were mixed to form a uniform solution. The solution was filtered through a 0.1 μm membrane filter to produce a resist composition.

[Examples 2, 3 and Comparative Examples 1 to 3]
The monomer (m3) in Example 1 was changed to a monomer shown in Table 1. Otherwise, a polymer was produced and evaluated in the same manner as in Example 1.
Further, a resist composition was produced in the same manner as in Example 1 using the obtained polymer.

  As shown in Table 1, the polymers of Examples 1 to 3 having the structural unit (1) had higher turbidity than the polymers of Comparative Examples 1 to 3 having no structural unit (1), High polarity.

Claims (5)

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

[In formula (1), R ¹ is a hydrogen atom or a methyl group, one of R ²¹ , R ²² , and R ²³ is an alkoxy group having 1 to 20 carbon atoms, and the other is an alkoxy group having 1 to 20 carbon atoms. An alkyl group, the other one is a hydrogen atom, an alkoxy group having 1 to 20 carbon atoms or an alkyl group having 1 to 20 carbon atoms, and Z ¹ is a substituted or unsubstituted divalent chain having 1 to 20 carbon atoms. hydrocarbon group, having 1 to 20 carbon atoms, a substituted or unsubstituted, divalent may have a hetero atom cyclic hydrocarbon group or a single bond, Z ^2, is 2 to 12 carbon atoms A valent chain hydrocarbon group, Z ³ is a cyclic hydrocarbon group which may have a heteroatom having 3 to 10 carbon atoms together with a carbon atom to which (R ²¹ R ²² R ²³ ) C— is bonded. And n is an integer of 0 to 3. ]   The polymer according to claim 1, further comprising a structural unit containing a lactone skeleton.   3. The polymer according to claim 1, wherein the content of the structural unit represented by the formula (1) is 10 mol% or more based on all structural units. 4.   A resist composition comprising the polymer according to claim 1 and a compound that generates an acid upon irradiation with actinic rays or radiation.   A step of applying the resist composition according to claim 4 on a surface to be processed of a substrate to form a resist film, a step of exposing the resist film, and using the exposed resist film with a developer. Developing the substrate on which the pattern is formed.