WO2020129611A1 - Polymer having hydrophilic protecting group for resists - Google Patents

Abstract

[Problem] To produce and provide a polymer for resists with high accuracy, said polymer for resists having a high alkali dissolution rate and being useful for a thick resist. [Solution] A polymer for resists, the solubility of which in a developer liquid is changed by the action of an acid, and which has a structure wherein at least some of the phenolic hydroxyl groups in the polymer are protected by groups represented by formula (1). (In formula (1), R¹ represents an alkyl group having 1-5 carbon atoms or a cycloalkyl group having 3-6 carbon atoms; n represents an integer of 1-5; and * represents a binding site to a residue that is obtained by removing a hydrogen atom from a phenolic hydroxyl group.)

Description

Polymer for resist having hydrophilic protective group

The present invention relates to a resist polymer whose solubility in a developing solution is changed by the action of an acid. More specifically, it relates to a polymer useful for a thick film resist and a composition for a thick film resist containing the same.

According to downsizing of electronic devices, the mounting density of semiconductor packages is increasing. Photolithography technology has been used to develop multi-pin thin-film packaging of packages, miniaturization of package size, two-dimensional packaging technology by flip chip method, three-dimensional packaging technology, and the like, which are called photofabrication.

For the above-mentioned photofabrication, a thick film resist composition for forming a photoresist layer having a film thickness of 1 μm or more has been used (see Patent Documents 1 to 3). In lithography using a thick film photoresist, not only the alkali dissolution rate of an exposed portion but also the alkali dissolution rate of an unexposed portion that is not deprotected is required to be appropriately high in order to improve throughput.

On the other hand, in the chemically amplified photoresist used for the pattern formation of LSI, as a base resin, a protecting group (hereinafter, referred to as “acid dissociation” that dissociates an alkali-soluble group such as a carboxyl group or a phenolic hydroxyl group by the action of an acid. A polymer having a repeating unit having a structure protected with a "protective group" has been used. A hydrophobic protective group has been used as the acid dissociable protective group in order to increase the difference in dissolution rate between the exposed portion and the unexposed portion (development contrast) during development of the resist film (see Patent Document 4). ..

In order to increase the alkali dissolution rate of a polymer using a hydrophobic acid-dissociable protective group, the introduction rate of the hydrophobic acid-dissociable protective group in the polymer must be reduced. However, it is not easy to accurately manufacture a polymer having a low introduction rate of the hydrophobic acid dissociable protective group. In addition, since a slight difference in the introduction rate greatly affects the alkali dissolution rate of the polymer, it was extremely difficult to strictly control the alkali dissolution rate of the polymer.

International publication WO2017/110352 Special table 2011-501815 Japanese Unexamined Patent Publication No. 2006-178423 JP-A-10-171110

An object of the present invention is to accurately manufacture and provide a resist polymer having a high alkali dissolution rate, which is useful for a thick film resist.

As a result of intensive studies to solve the above problems, the present inventors have shown that in a resist polymer whose solubility in a developing solution is changed by the action of an acid, a phenolic hydroxyl group in the polymer is a hydrophilic group having an oxyethylene group. The present inventors have found that the protection with an acidic acid-dissociable protective group can increase the alkali dissolution rate as compared with the conventional protection with a hydrophobic acid-dissociable protective group, and completed the present invention.

（式（１）中、Ｒ^１は炭素数１～５のアルキル基を示し、ｎは１～５の整数を表す。＊はフェノール性水酸基から水素原子を除いた残基への結合部を表す。）
で表される基で保護された構造を有する、レジスト用重合体。
＜２＞　フェノール性水酸基の少なくとも一部が式（１）で表される基で保護される重合体が、ｐ－ヒドロキシスチレンまたは４－ヒドロキシフェニル（メタ）アクリレートに由来する構造単位を有する重合体である、＜１＞に記載のレジスト用重合体。
＜３＞　フェノール性水酸基の少なくとも一部が式（１）で表される基で保護される重合体が、フェノール類と、アルデヒド類またはケトン類との縮重合により得られるノボラック型重合体である、＜１＞に記載のレジスト用重合体。
＜４＞　前記フェノール性水酸基の前記式（１）で表される基による保護率が、前記重合体に含まれる全フェノール数１００モル％に対して５～６０モル％である、＜１＞～＜３＞のいずれかに記載のレジスト用重合体。
＜５＞　重量平均分子量が５，０００～４００，０００である、＜１＞～＜４＞のいずれかに記載のレジスト用重合体。
＜６＞　少なくとも、＜１＞～＜５＞のいずれかに記載の重合体、溶媒および酸発生剤を含む、厚膜レジスト用組成物。 That is, the present invention provides the following <1> to <6>.
<1> A resist polymer whose solubility in a developing solution is changed by the action of an acid,
At least part of the phenolic hydroxyl groups in the polymer is represented by the following formula (1):

(In the formula (1), R ¹ represents an alkyl group having 1 to 5 carbon atoms, n represents an integer of 1 to 5. * represents a bond portion to a residue obtained by removing a hydrogen atom from a phenolic hydroxyl group. .)
A resist polymer having a structure protected by a group represented by.
<2> A polymer in which at least a part of a phenolic hydroxyl group is protected by a group represented by the formula (1), the polymer having a structural unit derived from p-hydroxystyrene or 4-hydroxyphenyl(meth)acrylate. The polymer for resist according to <1>.
<3> The polymer in which at least a part of the phenolic hydroxyl group is protected by the group represented by the formula (1) is a novolak-type polymer obtained by condensation polymerization of phenols and aldehydes or ketones. The polymer for resist according to <1>.
<4> The degree of protection of the phenolic hydroxyl group with the group represented by the formula (1) is 5 to 60 mol% with respect to 100 mol% of the total number of phenols contained in the polymer, <1> to The resist polymer according to any one of <3>.
<5> The resist polymer according to any one of <1> to <4>, which has a weight average molecular weight of 5,000 to 400,000.
<6> A thick film resist composition containing at least the polymer according to any one of <1> to <5>, a solvent, and an acid generator.

According to the present invention, it is possible to accurately provide a resist polymer having a high alkali dissolution rate.

　式（１）において、Ｒ^１は炭素数１～５のアルキル基であり、好ましくは炭素数１～３のアルキル基、さらに好ましくはメチル基又はエチル基である。ｎは１～５の整数であり、好ましくは１～４の整数である。＊はフェノール性水酸基から水素原子を除いた残基への結合部を表す。 <Polymer for resist>
The polymer of the present invention is a resist polymer whose solubility in a developing solution is changed by the action of an acid, and at least a part of the phenolic hydroxyl group in the polymer is a group represented by the following formula (1). It has a protected structure.

In the formula (1), R ¹ is an alkyl group having 1 to 5 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group or an ethyl group. n is an integer of 1 to 5, preferably 1 to 4. * Represents a bond to a residue obtained by removing a hydrogen atom from a phenolic hydroxyl group.

Examples of the group represented by the formula (1) include the following.

In the polymer of the present invention, a part of the phenolic hydroxyl group in the polymer having a structural unit derived from p-hydroxystyrene or 4-hydroxyphenyl(meth)acrylate is protected by the group represented by the formula (1). Polymers are preferred.
In addition, in this specification, "(meth)acrylate" means "at least 1 type of an acrylate and a methacrylate".

Further, as the polymer of the present invention, a part of the phenolic hydroxyl group in the novolak type polymer obtained by the condensation polymerization of phenols and aldehydes or ketones is protected by the group represented by the formula (1). Polymers are also preferred.

　式（２）において、Ｒ^１およびｎの定義および好ましい態様は式（１）と同じである。 The polymer of the present invention is obtained by reacting (acetalizing) a polymer having a phenolic hydroxyl group in its structure with a vinyl ether represented by the following formula (2) in the presence of a solvent and an acid catalyst. You may use 1 type or multiple types of vinyl ether.

In formula (2), the definitions and preferred embodiments of R ¹ and n are the same as in formula (1).

For example, the polymer of the present invention is obtained by adding a polymer having a structural unit derived from p-hydroxystyrene or 4-hydroxyphenyl(meth)acrylate to a vinyl ether represented by the formula (2) in the presence of a solvent and an acid catalyst. It can be obtained by reacting with (acetalization). Similarly, the polymer of the present invention is obtained by reacting a novolak-type polymer obtained by polycondensation of a phenol with an aldehyde or a ketone with a vinyl ether represented by the formula (2) in the presence of a solvent and an acid catalyst. It is obtained by (acetalization). In each case, one kind or plural kinds of vinyl ether may be used.

Examples of the vinyl ether represented by the formula (2) include the following.

Examples of the acid catalyst used in the acetalization reaction include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid; carboxylic acids such as formic acid, acetic acid, butyric acid and trifluoroacetic acid; methanesulfonic acid, benzenesulfonic acid and toluene. Examples thereof include sulfonic acids such as sulfonic acid; phosphonic acids such as methanephosphonic acid and benzenephosphonic acid. Among them, phosphoric acid or sulfonic acid is preferable from the viewpoint of suppressing the polymerization reaction of vinyl ether.

The amount of the acid catalyst used cannot be unconditionally specified because it varies depending on the type of acid used, but it is usually 1 to 5000 ppm, preferably 1 to 2000 ppm with respect to the reaction system. When the amount of the acid catalyst used is within the above range, side reactions such as a polymerization reaction of vinyl ether are unlikely to occur, and a sufficient reaction rate can be easily obtained.

The solvent used for the acetalization reaction may be a solvent that can stably dissolve the polymer having a phenolic hydroxyl group as a raw material, vinyl ether, an acid catalyst, and the product obtained by the acetalization reaction, and specifically Are esters such as methyl acetate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, methyl propionate, methyl lactate, ethyl lactate; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, Examples thereof include ether esters such as propylene glycol monoethyl ether acetate; ethers such as tetrahydrofuran, 1,4-dioxane, ethylene glycol dimethyl ether; aromatic hydrocarbons such as toluene and xylene, which may be used alone or in combination. The above can be mixed and used.

The temperature of the acetalization reaction is preferably 25 to 120°C, preferably 30 to 100°C, more preferably 30 to 80°C.

The protection rate of the phenolic hydroxyl group in the polymer of the present invention by the group represented by the formula (1) (protection group introduction rate) is preferably 5 to 100 mol% of the total number of phenols contained in the polymer. 60 mol%, more preferably 8 to 60 mol%, further preferably 15 to 60 mol%, particularly preferably 20 to 60 mol%, still more preferably 25 to 55 mol%. , Most preferably 30 to 50 mol %. When the protective group introduction ratio is 5 mol% or more, particularly 20 mol% or more, the protection group introduction ratio is easily adjusted, and therefore the alkali dissolution rate is more easily adjusted. When it is 60 mol% or less, It becomes easy to form a desired resist pattern while realizing a high alkali dissolution rate.

After the acetalization reaction, a basic compound may be added to neutralize the acid catalyst. Specifically, alkali metal compounds such as alkali metal hydroxides, carbonates and hydrogencarbonates such as sodium and potassium; ammonia water and ammonia gas; amines such as trimethylamine and triethylamine; pyridine and methylpyridine. Pyridines; quaternary ammonium compounds such as tetraalkylammonium hydroxide; and basic ion exchange resins, etc. are preferable, amines and quaternary ammonium compounds are more preferable, and amines are more preferable.

The polymer of the present invention may contain other structures. As the monomer that provides another structural unit, various monomers used in known resist polymers for adjusting the solubility in a lithographic solvent or an alkali developing solution or the substrate adhesion can be used. ..

When the polymer in which the phenolic hydroxyl group is protected by the group represented by the formula (1) is a polymer having a structural unit derived from p-hydroxystyrene or 4-hydroxyphenyl(meth)acrylate, examples of the comonomer include: Styrene-based monomers derived from styrene, vinylnaphthalene, vinylanthracene, etc.; Various (meth)acrylic acid ester-based monomers derived from acrylic acid and methacrylic acid; derived from norbornene, tricyclodecene, tetracyclododecene, etc. And norbornene-based monomers. Further, indene, acenaphthylene and the like can be copolymerized. However, when using a monomer having an acid-dissociable group in the above-mentioned monomers, care must be taken so that the acid-dissociable group is not eliminated by the action of the acid catalyst used in the acetalization reaction.

Polymers having a structural unit derived from p-hydroxystyrene or 4-hydroxyphenyl(meth)acrylate are known, for example, as described in JP-A-02-047109, JP-A-10-251315, and re-table 2012/081619. It can be manufactured by the method of.
Further, poly-p-hydroxystyrene is available from Maruzen Petrochemical Co., Ltd. and Nippon Soda Co., Ltd.
A novolac type polymer obtained by polycondensation of phenols with aldehydes or ketones can also be produced by a known method. That is, it can be produced by a method of reacting a phenol with an aldehyde or a ketone in the presence of an acid catalyst. Further, since many kinds of novolac resins are commercially available, they can be used.

<Composition for thick film resist>
The composition containing the above-mentioned polymer can be used for applications such as resists required for semiconductor lithography. In particular, it can be suitably used for the purpose of forming a thick film resist having a film thickness of 1 μm or more, preferably 1 μm or more and 100 μm or less. The thick film resist composition of the present invention contains at least a polymer, a solvent, and an acid generator, and may further contain an acid diffusion inhibitor and the like.

The acid generator can be appropriately selected and used from those proposed as acid generators for chemically amplified resists. Such examples include onium salts such as iodonium salts and sulfonium salts, oxime sulfonates, diazomethanes such as bisalkyl or bisarylsulfonyldiazomethanes, nitrobenzyl sulfonates, imino sulfonates, disulfones and the like. Of these, onium salts are preferable. These may be used alone or in combination of two or more.

The acid diffusion inhibitor can be appropriately selected from those that have been proposed as acid diffusion inhibitors for chemically amplified resists. As such an example, a nitrogen-containing organic compound can be mentioned, and primary to tertiary alkylamines or hydroxyalkylamines are preferable. Particularly, tertiary alkylamines and tertiary hydroxyalkylamines are preferable, and among them, triethanolamine and triisopropanolamine are particularly preferable. These may be used alone or in combination of two or more.

Any solvent may be used as long as it can dissolve each component constituting the resist composition to form a uniform solution, and any one of known solvents for forming a coating film can be used as a single solvent. Alternatively, it can be used as a mixed solvent of two or more kinds. A solvent having at least one polar group selected from a ketone bond, an ester bond, an ether bond, and a hydroxy group is preferable because of its excellent solubility. Among them, a solvent having a boiling point of 110 to 220° C. at atmospheric pressure is particularly preferable because it has an appropriate evaporation rate in baking after spin coating and is excellent in film forming property. Specific examples of such a solvent include a solvent having a ketone bond such as methyl isobutyl ketone, methyl isoamyl ketone, methyl amyl ketone, and cyclohexanone; an ether bond such as propylene glycol monomethyl ether (PGME) and propylene glycol monoethyl ether; and a hydroxy group. A solvent having an ether bond and an ester bond such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate and ethyl 3-ethoxypropionate, an ester bond such as methyl lactate and ethyl lactate and a hydroxy group. And a solvent having an ester bond such as γ-butyrolactone. Of these, PGMEA, PGME, γ-butyrolactone and ethyl lactate are preferable.

In the resist composition, if desired, organic carboxylic acids or oxoacids of phosphorus for the purpose of preventing sensitivity deterioration of the acid generator, improving the resist pattern shape, leaving stability, etc., and improving the performance of the resist film. In order to improve the coating property, a surfactant, a dissolution inhibitor, a plasticizer, a stabilizer, a colorant, an antihalation agent, a dye, etc., which are commonly used as resist additives, are required. It can be contained as appropriate.

Hereinafter, the embodiments of the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples. In the following examples, parts are based on mass unless otherwise specified.

The analysis of the compound in this example was performed as follows.

[Weight average molecular weight/dispersion]
The weight average molecular weight (Mw) and dispersity (Mw/Mn) of the polymer synthesized below were measured by GPC (gel permeation chromatography) using polystyrene as a standard product. 0.02 g of the purified polymer was dissolved in 1 ml of tetrahydrofuran to prepare a sample for analysis. The sample injection amount into the device was 50 μl.
Measuring device: Tosoh HPLC-8220GPC
Detector: Differential refractive index (RI) detector Column: Shodex GPC KF804 x 3 (manufactured by Showa Denko)
Eluent: Tetrahydrofuran Flow rate: 1.0 mL/min Temperature: 40°C
Calibration curve: Created using polystyrene standard sample (Tosoh Corporation)

[Polymerization composition ratio/protection group introduction ratio]
The composition ratio and the protective group introduction ratio of the synthesized polymer were analyzed by ¹³ C-NMR. 2.0 g of the polymer solution after concentration adjustment and 0.1 g of Cr(III) acetylacetonate were dissolved in 1.0 g of heavy acetone to prepare a sample for analysis.
Device: Bruker AVANCE400
Nuclide: ¹³ C
Measurement method: Inverse gate decoupling Integration number: 6000 times Measurement tube diameter: 10 mmφ

[Alkaline dissolution rate (ADR)]
Each raw material was diluted with PGMEA, and applied using a spin coater so as to have a film thickness of 1.0 μm on the disilazane-treated Si substrate. After baking at 100° C. for 60 seconds and measuring with an optical interference type film thickness meter, development is carried out with an alkali developing solution having a tetramethylammonium hydroxide (TMAH) concentration of 2.38 wt %, and the polymer is completely removed. The dissolution rate (Å/sec) was calculated from the time until dissolution and the film thickness. For those with a slow dissolution rate, the dissolution rate (Å/sec) was calculated from the amount of film loss after development for 600 seconds.
Optical interference film thickness meter: KT-22 (Foothill Instruments)
Alkaline developer: MF-CD26 (2.38wt%-TMAH)
Development temperature: 23℃
DR measuring device: TFA-11 manufactured by Luzchem Research, Inc.

Reference Example 1 Preparation of p-Hydroxystyrene Homopolymer (PHS) Solution In a round-bottomed flask equipped with a thermometer, a cooling tube and a stirrer, 1000 parts of poly p-hydroxystyrene (Maruzen Petrochemical, Marukalinker S-2P) After 5,000 parts of propylene glycol monomethyl ether acetate (hereinafter, PGMEA) was charged and the system was replaced with nitrogen while stirring, the temperature was raised to 60°C. Next, the mixture was concentrated under reduced pressure at 40° C. to remove excess water and PGMEA, and the polyp-hydroxystyrene concentration was adjusted to 30 wt %.
The adjusted poly-p-hydroxystyrene had Mw=5700 and Mw/Mn=2.03.

Example 1 97.5 parts of the 30 wt% poly-p-hydroxystyrene/PGMEA solution obtained in Reference Example 1 and 31.2 parts of PGMEA were placed in a round-bottomed flask equipped with a PHS-MOVE protected polymer thermometer, a condenser and a stirrer. Then, 0.7 parts of a 0.1 wt% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 9.4 parts of methoxyethyl vinyl ether (hereinafter, MOVE) and 8.7 parts of PGMEA was added dropwise thereto over 30 minutes, and after the completion of the addition, the reaction was continued for 6 hours. After completion of the reaction, 15.3 parts of PGMEA was added to the reaction solution to dilute it, and then 3.3 parts of a weakly basic ion exchange resin (Amberlist B20-HG•DRY manufactured by Organo) was used for about 6 hours using a column. Ion exchange was performed. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Example 2 195.8 parts of the 30 wt% poly-p-hydroxystyrene/PGMEA solution obtained in Reference Example 1 and 34.2 parts of PGMEA were placed in a round-bottomed flask equipped with a PHS-MOVE protected polymer thermometer, a condenser and a stirrer. 0.8 parts of 0.1 wt% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 28.2 parts of MOVE and 26.3 parts of PGMEA was added dropwise over 30 minutes, and the reaction was continued for another 3 hours after the completion of the addition. After completion of the reaction, 25.8 parts of PGMEA was added to the reaction solution to dilute it, and ion exchange was carried out for about 6 hours using 0.7 part of Amberlyst B20-HG.DRY using a column. After the ion exchange resin, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Example 3 317.3 parts of the 30 wt% poly-p-hydroxystyrene/PGMEA solution obtained in Reference Example 1 and 53.4 parts of PGMEA were placed in a round-bottomed flask equipped with a PHS-EOVE protected polymer thermometer, a condenser and a stirrer. Then, 1.2 parts of a 0.1 wt% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 33.5 parts of ethoxyethyl vinyl ether (hereinafter, EOVE) and 30.9 parts of PGMEA was added dropwise over 30 minutes, and the reaction was continued for another 2.5 hours after the completion of the addition. After completion of the reaction, 53.4 parts of PGMEA was added to the reaction solution to dilute it, and then ion exchange was carried out for about 6 hours using 1.7 parts of Amberlyst B20-HG/DRY. After the ion exchange resin, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Example 4 251.7 parts of the 30 wt% poly-p-hydroxystyrene/PGMEA solution obtained in Reference Example 1 and 34.2 parts of PGMEA were placed in a round-bottomed flask equipped with a PHS-TEGVE protected polymer thermometer, a condenser and a stirrer. Then, 1.0 part of a 0.1 wt% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40° C. by heating. A mixed solution of 2-(2-(2-methoxyethoxy)ethoxy)ethyl vinyl ether (hereinafter TEGVE) 44.6 parts and PGMEA 41.9 parts was added dropwise over 30 minutes, and the reaction was continued for another 3 hours after the completion of the addition. I continued. After the completion of the reaction, 25.0 parts of PGMEA was added to the reaction solution to dilute it, and then 1.3 parts of Amberlyst B20-HG/DRY was used for column exchange for about 6 hours using a column. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Reference Example 2 Production of p-Hydroxystyrene /m- Hydroxystyrene Copolymer (PHS/MHS) In an eggplant flask equipped with a thermometer, a cooling tube and a stirrer, 24 wt% of p-hydroxystyrene, 23 wt% of methanol, and 10 wt of water. % P-ethylphenol solution (hereinafter PHS monomer solution) 300.0 parts, m-hydroxystyrene 24 wt%, methanol 23 wt%, water 10 wt% m-ethylphenol solution (hereinafter MHS monomer solution) 64.9 Parts were charged, and the temperature was raised to 80° C. by heating. 700.0 parts of PHS monomer solution, 151.4 parts of MHS monomer solution, and 61.5 parts of dimethyl 2,2′-azobis(2-methylpropionate) were added to another flask and stirred to form a uniform dropping solution. The dropping solution was dropped into the eggplant flask for 2 hours to carry out a polymerization reaction. After the dropping was completed, the reaction was further continued at 80° C. for 2 hours. Then, a solution prepared by dissolving 15.4 parts of dimethyl 2,2′-azobis(2-methylpropionate) in 61.5 parts of isopropanol was additionally charged, and the reaction was continued for another 2 hours. After the polymerization liquid was cooled to room temperature, it was added dropwise to 2012 parts of methylcyclohexane to precipitate a polymer, and the supernatant liquid was removed. After adding 360 parts of isopropanol to the precipitated polymer and re-dissolving it, the operation of dropping the polymer solution into methylcyclohexane to precipitate the polymer was repeated 5 times to remove unreacted monomers and oligomers in the polymer. The recovered polymer was dissolved in 390 parts of methanol, and heated at 40° C. under reduced pressure with stirring to add PGMEA while distilling off methanol to prepare a PGMEA solution having a polymer concentration of 30 wt %.
The obtained copolymer had a polymer composition of p-hydroxystyrene:m-hydroxystyrene=80.4:19.6, Mw=5900, and Mw/Mn=1.68.

Example 5 194.0 parts of PGMEA solution having a PHS/MHS copolymer concentration of 30 wt% obtained in Reference Example 2 was placed in a round-bottomed flask equipped with a PHS/MHS-MOVE protected polymer thermometer, a condenser and a stirrer, and PGMEA29. 1.4 parts, 3.6 parts of a 0.1 wt% methanesulfonic acid/PGMEA solution were charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 18.5 parts of MOVE and 17.3 parts of PGMEA was added dropwise thereto over 30 minutes, and after completion of the addition, the reaction was continued for 4 hours. After the reaction was completed, 29.4 parts of PGMEA was added to the reaction solution to dilute it, and then ion exchange was carried out for about 6 hours using 6.6 parts of Amberlyst B20-HG.DRY using a column. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Reference Example 3 Preparation of novolak resin solution In a round-bottomed flask equipped with a thermometer, a cooling tube and a stirrer, 272 parts of novolak resin (Phenolite TD-2090 manufactured by DIC) and 1565 parts of PGMEA were charged, and concentrated at 40° C. under reduced pressure to obtain an excess. Water and PGMEA were removed, and the novolak resin concentration was adjusted to 30 wt %.
The adjusted novolak resin had Mw=7600 and Mw/Mn=4.70.

Example 6 194.8 parts of the 30 wt% novolak resin/PGMEA solution obtained in Reference Example 3, PGMEA 28.9 parts, and 0.1 wt were placed in a recovery flask equipped with a novolac-MOVE protected polymer thermometer, a cooling tube, and a stirrer. A 0.7% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 20.5 parts of MOVE and 19.4 parts of PGMEA was added dropwise over 30 minutes, and the reaction was continued for another 4 hours after the completion of the addition. After completion of the reaction, 29.0 parts of PGMEA was added to the reaction solution to dilute it, and then 1.7 parts of a weakly basic ion exchange resin (Amberlist B20-HG DRY manufactured by Organo) was used for about 6 hours using a column. Ion exchange was performed. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Comparative Example 1 162.4 parts of the 30 wt% poly-p-hydroxystyrene/PGMEA solution obtained in Reference Example 1 and 26.2 parts of PGMEA were placed in a round-bottomed flask equipped with a PHS-EVE protected polymer thermometer, a condenser and a stirrer. Then, 1.0 part of a 0.1 wt% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40° C. by heating. A mixed solution of 10.9 parts of ethyl vinyl ether (hereinafter, EVE) and 10.1 parts of PGMEA was added dropwise thereto over 30 minutes, and after the completion of the addition, the reaction was continued for 4 hours. After completion of the reaction, 29.6 parts of PGMEA was added to the reaction solution to dilute it, and then 4.4 parts of a weakly basic ion exchange resin (Amberlist B20-HG DRY manufactured by Organo) was used for about 6 hours using a column. Ion exchange was performed. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Comparative Example 2 In a round-bottomed flask equipped with a PHS-CHVE protected polymer thermometer, a condenser and a stirrer, 215.8 parts of the 30 wt% poly-p-hydroxystyrene/PGMEA solution obtained in Reference Example 1 and 31.2 parts of PGMEA were obtained. 0.5 parts of 0.1 wt% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 25.1 parts of cyclohexyl vinyl ether (hereinafter referred to as CHVE) and 23.8 parts of PGMEA was added dropwise over 30 minutes, and after completion of the addition, the reaction was continued for 4 hours. After the reaction was completed, 29.9 parts of PGMEA was added to the reaction solution to dilute it, and then 0.4 parts of Amberlyst B20-HG.DRY was used for ion exchange over 0.4 hours using a column. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Comparative Example 3 98.5 parts of the 30 wt% poly-p-hydroxystyrene/PGMEA solution obtained in Reference Example 1 and 16.2 parts of PGMEA were placed in a round-bottomed flask equipped with a PHS-DHP protected polymer thermometer, a condenser and a stirrer. Then, 1.5 parts of a 0.1 wt% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 7.3 parts of dihydropyran (hereinafter referred to as DHP) and 7.3 parts of PGMEA was added dropwise over 5 minutes (shorter than other parts. Should it be expressed in actual weight rather than parts?). After the dropping was completed, the reaction was further continued for 6 hours. After completion of the reaction, 16.6 parts of PGMEA was added to the reaction solution to dilute it, and ion exchange was carried out with 0.8 part of Amberlyst B20-HG.DRY using the column for about 6 hours. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Comparative Example 4 195.0 parts of PGMEA solution having a PHS/MHS copolymer concentration of 30 wt% obtained in Reference Example 2 was placed in a round-bottomed flask equipped with a PHS/MHS-EVE protected polymer thermometer, a cooling tube and a stirrer, and PGMEA31. 0.6 parts, 0.7 parts of a 0.1 wt% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 13.3 parts of EVE and 12.3 parts of PGMEA was added dropwise over 30 minutes, and the reaction was continued for another 4 hours after the completion of the addition. After completion of the reaction, 36.0 parts of PGMEA was added to the reaction solution to dilute it, and ion exchange was carried out with 1.4 parts of Amberlyst B20-HG.DRY over 1.4 hours using a column. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Comparative Example 5 195.5 parts of the 30 wt% novolak resin/PGMEA solution obtained in Reference Example 3, PGMEA 14.0 parts, and 0.1 wt were placed in a recovery flask equipped with a novolac-EVE protected polymer thermometer, a cooling tube, and a stirrer. A 0.7% methanesulfonic acid/PGMEA solution was charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 14.8 parts of EVE and 14.0 parts of PGMEA was added dropwise over 30 minutes, and after the completion of the addition, the reaction was continued for 4 hours. After completion of the reaction, 34.6 parts of PGMEA was added to the reaction solution to dilute it, and ion exchange was carried out for about 6 hours using 1.7 parts of Amberlyst B20-HG.DRY using a column. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Reference Example 4 Production of p-Hydroxystyrene /t-Butyl Acrylate Copolymer (PHS/TBA) In an eggplant flask equipped with a thermometer, a condenser and a stirrer, 24 wt% of p-hydroxystyrene, 23 wt% of methanol, 10 wt of water. %-Containing p-ethylphenol solution (hereinafter referred to as PHS monomer solution) (357.0 parts) and TBA (20.8 parts) were charged, and the temperature was raised to 83°C. To another flask, add 153.0 parts of PHS monomer solution, 8.9 parts of TBA, 9.0 parts of dimethyl 2,2'-azobis(2-methylpropionate) and stir to make a uniform drop solution. Was dropped into the eggplant flask for 2 hours to carry out a polymerization reaction. After the dropping was completed, the reaction was further continued at 83° C. for 2 hours. Then, a solution prepared by dissolving 9.0 parts of dimethyl 2,2′-azobis(2-methylpropionate) in 21.1 parts of isopropanol was additionally charged, and the reaction was continued for another 2 hours. The polymerization liquid was cooled to room temperature and then added dropwise to 521 parts of methylcyclohexane to precipitate a polymer, and the supernatant liquid was removed. After 203 parts of isopropanol was added to the precipitated polymer to redissolve it, an operation of dropping the polymer solution into methylcyclohexane to precipitate the polymer was repeated 5 times to remove unreacted monomers and oligomers in the polymer. The recovered polymer was dissolved in 1258 parts of PGMEA, and heated at 40° C. under reduced pressure while stirring to distill off the methylcyclohexane and isopropanol solvent, and PGMEA was added to prepare a PGMEA solution having a polymer concentration of 30 wt %.
The obtained copolymer had a polymer composition of p-hydroxystyrene:t-butyl acrylate=80.2:19.8, Mw=16700, and Mw/Mn=2.08.

Example 7 PHSEA of the 30 wt% poly-p-hydroxystyrene/t-butyl acrylate copolymer obtained in Reference Example 4 was placed in a round-bottomed flask equipped with a PHS/TBA-MOVE protected polymer thermometer, a condenser and a stirrer. A solution (233.9 parts), PGMEA (27.9 parts), and a 10 wt% trifluoroacetic acid/PGMEA solution (1.5 parts) were charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 5.7 parts of MOVE and 5.7 parts of PGMEA was added dropwise over 30 minutes, and the reaction was continued for another 4 hours after the completion of the addition. After the completion of the reaction, 22.2 parts of PGMEA was added to the reaction solution to dilute it, and then 2.8 parts of a weakly basic ion exchange resin (Amberlist B20-HG•DRY manufactured by Organo) was used for about 6 hours using a column. Ion exchange was performed. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

Comparative Example 6 A PHSEA of the 30 wt% poly-p-hydroxystyrene/t-butyl acrylate copolymer obtained in Reference Example 4 was placed in a round-bottomed flask equipped with a PHS/TBA-EVE protected polymer thermometer, a condenser and a stirrer. A solution (398.3 parts), PGMEA (43.3 parts), and a 10 wt% trifluoroacetic acid/PGMEA solution (2.4 parts) were charged, the system was replaced with nitrogen while stirring, and the temperature was raised to 40°C. A mixed solution of 8.5 parts of EVE and 6.9 parts of PGMEA was added dropwise over 30 minutes, and the reaction was continued for another 4 hours after the completion of the addition. After completion of the reaction, 36.4 parts of PGMEA was added to the reaction solution to dilute it, and then it was taken for about 6 hours using 4.5 parts of a weakly basic ion exchange resin (Amberlist B20-HG DRY manufactured by Organo) using a column. Ion exchange was performed. After the ion exchange, PGMEA was concentrated by vacuum concentration at 40° C., and the concentration was adjusted so that the polymer concentration was 50 wt %.
The weight average molecular weight, dispersity, protective group introduction rate, and alkali dissolution rate of the obtained polymer were measured, and the results are shown in Table 1.

The alkali dissolution rate of the polymer of the present invention is remarkably larger than that of the conventional polymer protected with a hydrophobic acid-dissociable group, and it is considered that the polymer of the present invention is useful for improving the lithography throughput by the thick film photoresist.

The polymer of the present invention can be used as a composition for thick film resist.

Claims (6)

A resist polymer whose solubility in a developing solution is changed by the action of an acid,
At least part of the phenolic hydroxyl groups in the polymer is represented by the following formula (1):

(In the formula (1), R ¹ represents an alkyl group having 1 to 5 carbon atoms, n represents an integer of 1 to 5. * represents a bond portion to a residue obtained by removing a hydrogen atom from a phenolic hydroxyl group. .)
A resist polymer having a structure protected by a group represented by. The polymer in which at least a part of the phenolic hydroxyl group is protected by the group represented by the formula (1) is a polymer having a structural unit derived from p-hydroxystyrene or 4-hydroxyphenyl(meth)acrylate. The polymer for resist according to claim 1. The polymer in which at least a part of the phenolic hydroxyl group is protected by a group represented by the formula (1) is a novolac polymer obtained by polycondensation of a phenol with an aldehyde or a ketone. 1. The resist polymer according to 1. The protection rate of the phenolic hydroxyl group by the group represented by the formula (1) is 5 to 60 mol% based on 100 mol% of the total number of phenols contained in the polymer. The polymer for resist according to the item 1. The resist polymer according to any one of claims 1 to 4, which has a weight average molecular weight of 5,000 to 400,000. A thick film resist composition containing at least the polymer according to any one of claims 1 to 5, a solvent, and an acid generator.