JP7192298B2 - Polymers, resist compositions, and methods of making patterned substrates - Google Patents

Description

The present invention relates to a polymer, a resist composition containing the polymer, and a method for producing a patterned substrate using the resist composition.

As a resist composition suitable for shortening the wavelength of irradiation light and miniaturizing patterns in lithography technology, it contains a resist polymer from which an acid-labile 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 are proceeding.
In Patent Document 1, as a structural unit having an acid-leaving group, the ester moiety is a hydrocarbon group containing a specific alicyclic hydrocarbon group (adamantyl group, cyclopentyl group), and an oxygen atom constituting an ester bond. describes a resist polymer having a (meth)acrylic acid ester unit having a tertiary carbon atom at the bonding site between and an alicyclic hydrocarbon group.

JP 2016-212213 A

In recent years, pattern miniaturization has progressed rapidly, and the development of resist materials capable of further improving various lithography properties such as sensitivity, pattern formability, and line width roughness (LWR) is desired.
In a resist composition containing a polymer having an acid-leaving group, sensitivity during pattern formation can be improved by increasing the reactivity (acid reactivity) between the acid-leaving group and acid.
However, the polymer using the structural unit having an acid-leaving group described in Patent Document 1 may have insufficient solubility in a developing solution, even if it has good acid reactivity.
An object of the present invention is to provide a polymer having good developer solubility, a resist composition containing the polymer, and a method for producing a patterned substrate using the resist composition.

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

[wherein 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 one is a an alkyl group, the remaining one is a hydrogen atom, an alkoxy group having 1 to 20 carbon atoms or an alkyl group having 1 to 20 carbon atoms, Z ¹ is a substituted or unsubstituted divalent chain formula having 1 to 20 carbon atoms a hydrocarbon group, a substituted or unsubstituted divalent cyclic hydrocarbon group having 1 to 20 carbon atoms which may have a heteroatom, or a single bond, Z ² is 2 having 1 to 12 carbon atoms A valent chain hydrocarbon group Z ³ is a cyclic hydrocarbon group optionally having a heteroatom having 3 to 10 carbon atoms together with the carbon atom to which (R ²¹ R ²² R ²³ )C— is bonded. and n is an integer of 0-3. ]
[2] The polymer of [1], further comprising a structural unit containing a lactone skeleton.
[3] The polymer of [1] or [2], wherein the content of the structural unit represented by the formula (1) is 10 mol% or more based on the total 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 exposure to actinic rays or radiation.
[5] A step of applying the resist composition of [4] above to a surface to be processed of a substrate to form a resist film, exposing the resist film to light, and exposing the exposed resist film to a developing solution. and developing a patterned substrate.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the board|substrate with which the pattern was formed using the polymer which developing solution solubility is favorable, the resist composition containing the said polymer, and the said resist composition can be provided.

The following term definitions apply throughout the specification and claims.
As used herein, a "structural unit" means an atomic group formed by a polymerization reaction of monomers.
As used herein, "(meth)acrylic acid" means acrylic acid or methacrylic acid.
In this specification, the structural unit represented by formula (1) is referred to as structural unit (1). Structural units represented by other formulas are similarly described.
In this specification, the compound represented by formula (2) is referred to as compound (2). Compounds represented by other formulas are similarly described.
In this specification, the monomer represented by formula (m1) is referred to as monomer (m1). Monomers represented by other formulas are similarly described.

<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.
Polymer (A) is preferably a copolymer having two or more structural units.
The polymer (A) preferably contains one or more structural units other than the structural unit (1), and more preferably contains 1 to 5 other structural units.
As other structural units, known structural units for chemically amplified resist compositions can be used. Examples thereof include structural units having a lactone skeleton and structural units having a hydrophilic group.

[Constituent 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 the ethylenic double bond of a monomer (hereinafter referred to as monomer (1)) which is a (meth)acrylate compound.

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, the other one is an alkyl group having 1 to 20 carbon atoms, and the remaining one is a hydrogen atom and 1 to 20 carbon atoms. or an alkyl group having 1 to 20 carbon atoms.

Among R ²¹ , R ²² , and R ²³ , the number of alkyl groups is preferably one in that higher solubility in an alkaline developer can be 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 remaining one is a hydrogen atom or an alkoxy group.

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

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 and optionally having a hetero atom; or a single bond.
When Z ¹ is a divalent chain hydrocarbon group, it may be linear or branched. An alkylene group is preferred as the divalent chain hydrocarbon group. Substituents include -O-, -S-, -NH- and -PH-. The number of carbon atoms is preferably 1-10, more preferably 1-6.
When Z ¹ is a divalent cyclic hydrocarbon group, it may be monocyclic or polycyclic. A cyclic saturated hydrocarbon group is preferable as the cyclic hydrocarbon group. Heteroatoms include nitrogen, oxygen, sulfur and phosphorus atoms. A substituent may be bonded to a carbon atom constituting the ring. Examples of substituents include alkyl groups having 1 to 10 carbon atoms. Alkyl groups may be linear or branched.
Z1 is preferably a ^single bond from the viewpoint of increasing the solubility of the resist material in the developer.

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

Z ³ is an atomic group forming a cyclic hydrocarbon group optionally having a heteroatom with 3 to 10 carbon atoms together with the carbon atom to which (R ²¹ R ²² R ²³ )C— is bonded; be. A cyclic hydrocarbon group may be monocyclic or polycyclic. The cyclic hydrocarbon group is preferably a hydrocarbon cyclic hydrocarbon group (having no heteroatoms).
The number of carbon atoms in the cyclic hydrocarbon group includes the carbon atom to which (R ²¹ R ²² R ²³ )C- is attached.
Cyclic hydrocarbon groups consisting of monocyclic hydrocarbons 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 preferable from the viewpoint of availability.
Cyclic hydrocarbon groups consisting of polycyclic hydrocarbons having 3 to 10 carbon atoms include, for example, bicyclo[4.3.0]nonanyl group, naphthalenyl group, decahydronaphthalenyl group, bornyl group, isobornyl group, norbornyl group, adamantyl group, noradamantyl group, and the like. Among these, a norbornyl group and an adamantyl group are preferred from the standpoint of availability.

The structural unit (1) in the polymer (A) may be of one kind or two or more kinds. From the viewpoint of balance with structural units other than the structural unit (1), the number of structural units (1) is preferably 3 or less.
The content of the structural unit (1) relative to the total structural units of the polymer (A) is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 30 mol% or more. When it is at least the above lower limit, the effect of improving the solubility in the organic solvent used for the resist solvent is excellent.
From the viewpoint of resist performance balance, the content of the structural unit (1) is preferably 80 mol % or less, more preferably 70 mol % or less, and even more preferably 60 mol % or less.

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 the carbon atom to which (R ²¹ R ²² R ²³ )C- is bonded. and R ²¹ , R ²² and R ²³ are 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 , Z ¹ is a single bond, and n=0.

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 obtain a (meth) It can be produced by a method for obtaining acrylic acid ester (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 formula (2), R ²¹ , R ²² and R ²³ are the same as R ²¹ , R ²² and R ²³ in formula (1) including preferred embodiments.
In formula (2), R ¹¹ is an alkyl group. The alkyl group may be linear, branched, or a cycloalkyl group. Examples include methyl group, ethyl group, propyl group, isopropyl group, butyl group, s-butyl group, t-butyl group, cyclopentyl group, cyclohexyl group and the like. Among these, a methyl group, an ethyl group, a propyl group, and an isopropyl group are preferable from the standpoint of availability.

In 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 of Y ¹ may be linear or branched. Examples thereof include ethylene group, propylene group, isopropylene group, butylene group, pentylene group and hexylene group. A cyclohexylene group etc. are mentioned as a cycloalkylene group. Among these, a butylene group and a pentylene group are preferable from the viewpoint of availability.

In the reaction between compound (2) and compound (3), the amount of compound (3) to be used is not particularly limited, but from the viewpoint of obtaining compound (4) in good yield, 0 per mol of compound (2) .5 mol or more is preferable, and 5 mol or less is preferable from the viewpoint of suppressing side reactions and the load on the processing steps after the reaction.
Compound (3) is preferably 0.5 to 5 mol, more preferably 0.8 to 4 mol, even more preferably 1 to 3 mol, per 1 mol of compound (2).

A solvent may be used in the reaction between compound (2) and compound (3). The solvent is not particularly limited as long as it does not react with compound (3). Examples include 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-butylmethyl ether, tetrahydrofuran and dioxane. . These solvents may be used singly or in combination of two or more. The amount of solvent used can be set appropriately.

The reaction temperature between compound (2) and compound (3) may be the temperature for a normal cyclization reaction using compound (3). From the viewpoint of shortening the reaction time, the temperature is preferably −100° C. or higher, more preferably −80° C. or higher. In order to suppress problems such as side reactions, the temperature is preferably 100° C. or lower, more preferably 80° C. or lower.
Since the reaction time varies depending on the reaction temperature and the like, it may be determined appropriately. For example, about 0.5 to 30 hours is preferable.

Compound (4) obtained by the reaction of compound (2) and compound (3) may be purified.
Known purification methods such as alkaline water washing, water washing, distillation, crystallization, and filtration can be appropriately combined in consideration of the physical properties of the product, the type and amount of raw materials, the type of solvent, 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 separately synthesized product may be used. The amount of (meth)acrylic acid chloride used is not particularly limited, but is preferably 0.5 mol or more per 1 mol of compound (4) from the viewpoint of obtaining compound (5) in good yield. From the point of view of preventing chloride-derived polymerization, the amount is preferably 3 mol or less.
The acrylic acid chloride is preferably 0.5 to 3 mol, more preferably 0.7 to 2.5 mol, even more preferably 0.9 to 2 mol, per 1 mol of compound (4).

In the reaction of compound (4) and (meth)acrylic acid chloride, a base may be added in order to obtain compound (5) in good yield. Examples of bases 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 reaction yield, and is preferably 3 mol or less from the viewpoint of suppressing the load on the treatment process after the reaction.
The base is preferably 0.1 to 3 mol, more preferably 0.5 to 2 mol, per 1 mol of compound (4).

A solvent may be used in the reaction between compound (4) and (meth)acrylic acid chloride. The solvent is not particularly limited as long as it does not react with (meth)acrylic acid chloride. Examples include 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-butylmethyl ether, tetrahydrofuran and dioxane. . These solvents may be used singly or in combination of two or more. The amount of solvent used can be set appropriately.

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

The reaction temperature in the step of reacting compound (4) with (meth)acrylic acid chloride may be the 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. Also, 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.
Since the reaction time varies depending on the reaction temperature and the like, it may be determined appropriately. For example, about 0.5 to 20 hours is preferable.

It is preferable to purify the compound (5) obtained by the reaction of the compound (4) and (meth)acrylic acid chloride. The method for purifying compound (5) is a known purification method such as alkaline water washing, water washing, distillation, crystallization, filtration, etc., in consideration of the physical properties of the product, the raw material, the type and amount of the base, the type of solvent, etc. They can be combined as appropriate.

Preferred embodiments of the method for producing compound (5) include the following aspects (1) to (3). In the following, the methoxy group is sometimes referred to as "MeO-" and the ethoxy group 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).
The compound (3-1) is a reaction product of 1,4-dibromobutane and metal Mg.

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

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

[Structural Unit Having Lactone Skeleton]
The polymer (A) preferably has at least one structural unit having a lactone skeleton as a structural unit other than the structural unit (1).
A 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 monocyclic lactone ring only, or the lactone ring may be condensed with an aromatic or non-aromatic hydrocarbon ring or heterocyclic ring.

A (meth)acrylic acid ester compound is preferable as the monomer having a lactone skeleton. In particular, (meth)acrylic acid esters having a substituted or unsubstituted δ-valerolactone ring, and (meth)acrylic acid esters having a substituted or unsubstituted γ-butyrolactone ring, from the viewpoint of excellent adhesion to substrates and 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 monomers 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 , (meth)acrylic acid pantoyl lactone, 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, and the like.
The monomer having a lactone skeleton may be used alone or in combination of two or more.
When the polymer (A) contains a structural unit having a lactone skeleton, the content thereof is preferably 20 mol% or more, more preferably 25 mol% or more, based on the total structural units. From the viewpoint of sensitivity and resolution, it is preferably 70 mol % or less, more preferably 60 mol % or less, and even more preferably 50 mol % or less.

[Structural Unit Having Hydrophilic Group]
The polymer (A) may have at least one structural unit having a hydrophilic group as a structural unit other than the structural unit (1) and the structural unit having a lactone skeleton.
The “hydrophilic group” used herein is one or more selected from the group consisting of —C(CF ₃ ) ₂ —OH, hydroxy group, cyano group, methoxy group, carboxy group and amino group.
Among these, it is preferable that the polymer applied to the pattern forming method of exposing with light having a wavelength of 250 nm or less has a hydroxy group or a cyano group.
A (meth)acrylic acid ester compound is preferable as the monomer having a hydrophilic group.

Specific examples of monomers 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, etc. is mentioned.
From the viewpoint of adhesion to substrates, etc., 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.
A monomer having a hydrophilic group may be used alone or in combination of two or more.
When the polymer (A) contains a structural unit having a hydrophilic group, the content thereof is preferably 5 to 30 mol%, preferably 10 to 25 mol%, based on the total structural units from the viewpoint of resist pattern rectangularity. more preferred.

[Structural units having other acid-leaving groups]
The polymer (A) may have, as other structural units, one or more structural units having other acid-leaving groups that do not fall under the structural unit (1).
The structural unit (1) is preferably 20 mol% or more, more preferably 40 mol% or more, and 50 mol% of the total of the structural units having other acid-leaving groups and the structural unit (1). The above is more preferable. It may be 100 mol %.

As a preferred embodiment of the polymer (A), the structural unit (1) is 15 to 80 mol%, the structural unit having a lactone skeleton is 20 to 70 mol%, and the total of these is Polymers with 70 to 100 mol % are mentioned.

The polymer (A) can be produced, for example, by a solution polymerization method in which monomers are radically polymerized in the presence of a polymerization solvent using a polymerization initiator.
The weight average molecular weight of the polymer (A) is preferably 1,000 to 100,000, more preferably 3,000 to 50,000, even more preferably 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 exposure to actinic rays or radiation. One type of polymer (A) may be used, or two or more types may be used in combination.
The content of the polymer (A) in the resist composition (excluding the solvent) is not particularly limited, but is preferably 70 to 99.9% by mass.

Examples of resist solvents include cyclopentanone, cyclohexanone, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), and the like. One type of resist solvent may be used, or two or more types 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 weight per 100 parts by weight 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 photoacid generators for chemically amplified resist compositions. The photoacid generators may be used singly or in combination of two or more.
Examples of photoacid generators include onium salt compounds, sulfonimide compounds, sulfone compounds, sulfonate ester compounds, quinonediazide compounds, and diazomethane compounds.
The amount of the photoacid generator used is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the polymer (A).

The resist composition may optionally contain nitrogen-containing compounds, acid compounds (organic carboxylic acids, phosphorus oxoacids or derivatives thereof), surfactants, other quenchers, sensitizers, antihalation agents, and storage stabilizers. , and may contain various additives such as antifoaming agents. As the additive, those known in the art can be used.

<Method for manufacturing patterned substrate>
An example of a method for manufacturing a patterned substrate will be described.
First, the surface of a substrate to be processed such as a silicon wafer is coated with a resist composition by spin coating or the like. Then, the substrate to be processed coated with the resist composition 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 is preferably a KrF excimer laser, an ArF excimer laser, an F2 excimer laser, or an EUV excimer laser, and particularly preferably an ArF excimer laser. Moreover, you may irradiate an electron beam.
Further, liquid immersion in which light is irradiated while a high refractive index liquid such as pure water, perfluoro-2-butyltetrahydrofuran, or perfluorotrialkylamine is interposed between the resist film and the final lens of the exposure device. Exposure may be performed.

After the exposure, a heat treatment (post-exposure bake, PEB) is applied as appropriate, and a developing solution is brought into contact with the resist film to partially dissolve the resist film. In the positive development process, the exposed areas are dissolved and removed with an alkaline developer.
In the polymer (A), the bond of the acid-leaving group is cleaved by the acid generated by exposure, and the dissolution rate of the exposed portion in the alkaline developer 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, aqueous ammonia; primary amines such as ethylamine and n-propylamine; diethylamine, di-n-butylamine and the like. secondary amines; tertiary amines such as triethylamine and methyldiethylamine; alcohol amines such as dimethylethanolamine and triethanolamine; quaternary ammonium salts such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; pyrrole, Cyclic amines such as pyheridine;
After 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 dry etching is selectively performed on portions without the resist.
After dry etching, the resist is removed with a remover to obtain a substrate on which a fine pattern is formed.

EXAMPLES The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. Reaction tracking was performed by gas chromatography.

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

<Method for measuring copolymer composition ratio>
For the polymer obtained in each example, the compositional ratio (unit: mol %) of 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 apparatus manufactured by JEOL Ltd. is used, and about 5% by mass of a sample solution (solvent is heavy chloroform) is placed in a sample tube with a diameter of 5 mm. , observation frequency 400 MHz, single pulse mode, ¹ H
64 integrations were performed. The measurement temperature was 60°C.

<Method for evaluating developer solubility (method for measuring turbidity)>
Using a turbidity meter (manufactured by Orbeco-Hellige, product name: TB200), turbidity Th (80) and turbidity Tm (80) were measured by the following measurement methods. Th(80) is an index of solubility in low-polarity organic solvents, and Tm(80) is an index of solubility in high-polarity organic solvents. 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 alkaline developer.

[Method for measuring turbidity Th (80)]
(1) A PGMEA solution having a concentration of 10% by mass is prepared by dissolving a polymer to be measured in PGMEA.
(2) n-heptane is added to the PGMEA solution prepared in (1) above to form a mixed solution, and the amount of n-heptane added to the PGMEA solution when the turbidity of the mixed solution reaches 10 NTU (Xh mass %) is determined.
(3) Add n-heptane in an amount corresponding to 80% by mass of Xh to the PGMEA solution prepared in (1) above, and stir at 25° C. for 4 hours to obtain a measurement solution.
(4) Let Th(80) be the turbidity of the measurement solution at 25°C.
[Method for measuring turbidity Tm (80)]
(5) Methanol is added to the PGMEA solution prepared in (1) to form a mixed solution, and the amount of methanol added to the PGMEA solution when the turbidity of the mixed solution becomes 5.0 NTU (X m mass% ).
(6) Methanol in an amount equivalent to 80% of the Xm mass % is added to the PGMEA solution prepared in (1) above, and stirred at 25° C. for 4 hours to obtain a measurement solution.
(7) Tm(80) is the turbidity of the measurement solution at 25°C.

Monomers (m1) to (m8) represented by the following formulas (m1) to (m8) were used in the following examples and comparative examples.

<Synthesis Example 1>
Monomer (m3) (compound (5-1)) was produced by the method of 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 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. 85 mL of a saturated ammonium chloride aqueous solution 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 brine. After drying with 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 magnesium shavings and 25 mL of tetrahydrofuran were added to a glass flask. dripped in time. Then, the mixture was stirred for 3 hours, cooled to −10° C., and 2.97 g (22 mmol) of compound (2-1) dissolved in 23 mL of tetrahydrofuran was added dropwise over 0.5 hour. After stirring at -10°C for 1 hour, the mixture was stirred at room temperature overnight. 50 mL of a 20% by mass ammonium chloride aqueous solution was added to separate the layers. The aqueous layer was extracted twice with 60 mL of ethyl acetate, and the organic layer was washed with 20 mL of a saturated sodium bicarbonate aqueous solution and then with 20 mL of saturated brine. After drying with 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 cooled to -40°C under 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. After cooling to −40° C. again, 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 lithium hydroxide aqueous solution and stirring at 50° C. for 2 hours, the liquids were separated. The aqueous layer was extracted with 20 mL of ethyl acetate three times, and the organic layer was washed with 30 mL of saturated aqueous sodium hydrogencarbonate solution and then with 15 mL of saturated brine. After drying with 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>
Monomer (m4) (compound (5-2)) was produced by the method of 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) .

The compound of interest was obtained in the same manner as in Step 3 of Synthesis Example 1, except that the compound (4-2) obtained above was used instead of the compound (4-1).
¹ H-NMR analysis 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]
A flask equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer was charged with 16.7 parts by mass of PGMEA under a nitrogen atmosphere, and the temperature of the hot water bath was raised to 80°C while stirring. Thereafter, the following mixture 1 was added dropwise into the flask from a dropping funnel over 4 hours, and the temperature was maintained at 80°C for 3 hours to obtain a reaction solution.
(Composition of mixture 1)
Monomer (m1) 6.80 parts by mass (40 mol%),
Monomer (m2) 4.72 parts by mass (20 mol%),
Monomer (m3) 8.49 parts by mass (40 mol%),
Solvent: 30.0 parts by mass of PGMEA, and polymerization initiator: 1.61 parts by mass of dimethyl-2,2'-azobisisobutyrate (manufactured by Wako Pure Chemical Industries, Ltd., V601 (trade name)).

The resulting reaction solution was added dropwise to about 10 times the volume of a mixed solvent of methanol and water (methanol/water=80/20 volume ratio) while stirring to obtain a white precipitate. The precipitate was separated by filtration, poured into the same amount of methanol as above, and washed with stirring. After washing, the precipitate was separated by filtration to obtain a wet polymer powder. The wet polymer powder was dried at 60° C. under reduced pressure for about 36 hours to obtain a dry powdery polymer.
The turbidity of the resulting polymer was measured by the method described above. The results are shown in Table 1 (hereinafter the same).
Table 2 shows the measurement results of the copolymerization 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 dry powdery polymer obtained above, 105.0 parts by mass of PGMEA, and 0.3 parts by mass of triphenylsulfonium triflate, which is a photoacid generator, were mixed to form a uniform solution, and then the pore diameter It was filtered through a 0.1 μm membrane filter to prepare a resist composition.

[Examples 2 and 3, Comparative Examples 1 to 3]
The monomer (m3) in Example 1 was changed to the monomer shown in Table 1. Otherwise, a polymer was produced and evaluated in the same manner as in Example 1.
Also, 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) have higher turbidity than the polymers of Comparative Examples 1 to 3 having no structural unit (1). Highly polar.

Claims (3)

A polymer comprising a structural unit represented by the following formula (1), a structural unit containing a lactone skeleton, and a structural unit having a hydrophilic group,
from the group consisting of a (meth)acrylic ester having a substituted or unsubstituted δ-valerolactone ring, and a (meth)acrylic ester having a substituted or unsubstituted γ-butyrolactone ring, in which the structural unit containing the lactone skeleton is A structural unit based on at least one selected monomer,
The structural unit having a hydrophilic group is (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxy-n-propyl (meth) acrylate, ( from the group consisting of 4-hydroxybutyl meth)acrylate, 3-hydroxyadamantyl (meth)acrylate, 2- or 3-cyano-5-norbornyl (meth)acrylate, and 2-cyanomethyl-2-adamantyl (meth)acrylate A structural unit based on at least one selected monomer,
With respect to all structural units, 20 to 70 mol% of the structural unit represented by the formula (1), 20 to 70 mol% of the structural unit containing the lactone skeleton, and 5 structural units having the hydrophilic group Polymers with ˜30 mol %.

[wherein 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 one is a an alkyl group, the remaining one is a hydrogen atom, an alkoxy group having 1 to 20 carbon atoms or an alkyl group having 1 to 20 carbon atoms, Z ¹ is a substituted or unsubstituted divalent chain formula having 1 to 20 carbon atoms a hydrocarbon group, a substituted or unsubstituted divalent cyclic hydrocarbon group having 1 to 20 carbon atoms which may have a heteroatom, or a single bond, Z ² is 2 having 1 to 12 carbon atoms A valent chain hydrocarbon group, Z ³ , together with the carbon atom to which (R ²¹ R ²² R ²³ )C- is bonded, forms a cyclic hydrocarbon group optionally having a heteroatom of 5 carbon atoms. atomic group, n is an integer of 0-3. ] A resist composition comprising the polymer according to claim 1 and a compound that generates an acid upon exposure to actinic rays or radiation. A step of applying the resist composition according to claim 2 on a surface to be processed of a substrate to form a resist film, a step of exposing the resist film, and a developing solution for the exposed resist film. and developing a patterned substrate.