JP4104155B2 - Novel (meth) acrylate copolymer and process for producing the same - Google Patents

Description

The present invention is a novel (meth) acrylate suitably used as a resin component of a chemically amplified photoresist composition that is highly transparent to ArF excimer laser and provides a resist pattern with excellent pattern characteristics, particularly dry etching resistance and adhesion. The present invention relates to a copolymer and a method for producing the same.

So far, as the resin component of the chemically amplified resist, polyhydroxystyrene having high transparency to KrF excimer laser (248 nm) and those obtained by protecting this hydroxyl group with an acid dissociable, dissolution inhibiting group have been mainly used. I came.
However, in recent years, the demand for miniaturization of semiconductor elements is increasing, and the light source is also shifting from a KrF excimer laser to a process using a shorter wavelength ArF excimer laser (193 nm).

  By the way, in a process using an ArF excimer laser (193 nm) as a light source, a resin having an aromatic ring such as polyhydroxystyrene, which has been used in the past, is not sufficiently transparent to the ArF excimer laser. As an alternative, an acrylic resin having no aromatic ring has been attracting attention. However, this acrylic resin has a drawback of poor dry etching resistance.

  In order to improve such dry etching resistance, it is known that it is effective to introduce an ester of acrylic acid and alicyclic alkyl into the structural unit in the resin. A polymer of an acrylate ester having a skeleton (see Patent Document 1), a copolymer of an acrylate ester having an adamantane skeleton in the ester portion and an acrylic acid tetrahydropyranyl ester (see Patent Document 2), and the like have been proposed. .

  However, if such an acrylate ester having an adamantane skeleton is introduced as a structural unit, a certain degree of improvement in transparency and dry etching resistance is recognized, but the effect is not always satisfactory. In addition, the acrylic acid ester having an adamantane skeleton itself is not readily available, and thus cannot be avoided in terms of cost. In addition, the sensitivity is insufficient, and a good pattern shape cannot be obtained.

On the other hand, in the process using an ArF excimer laser, it is an important purpose to form an ultrafine pattern of 0.2 μm or less with high resolution. There is a problem in that the adhesion with the resist layer is insufficient and the pattern collapses.
For this reason, the introduction of an acrylic acid ester having an oxygen-containing heterocyclic group such as 3-oxocyclohexyl ester of acrylic acid (see Patent Document 3) and γ-butyrolactone (see Patent Document 4) as a structural unit is proposed. Has been.

  However, when an acrylic resin into which an acrylate ester unit having such an oxygen-containing heterocyclic group is introduced is used for an ArF excimer laser, it can be used as a developer, although some improvement is observed in terms of adhesion. In paddle development, which has insufficient affinity for an aqueous alkali solution and is the mainstream of semiconductor device manufacturing, a faithful resist pattern cannot be formed. For this reason, it is an important issue in this field to realize an ArF excimer laser resist having excellent adhesion to a substrate and having an affinity for an aqueous alkali solution capable of paddle development.

JP-A-4-39665 (Claims and others) JP-A-5-265212 (Claims and others) JP-A-5-346668 (Claims and others) Japanese Patent Laid-Open No. 7-181677 (Claims and others)

Under such circumstances, the present invention is highly transparent to ArF excimer laser and exhibits excellent sensitivity, resist pattern shape, dry etching resistance and adhesion, and has high affinity for alkali. The object of the present invention is to provide a (meth) acrylate copolymer which can be suitably used as a resin component of a chemically amplified photoresist composition capable of giving a good resist pattern by development and a method for producing the same.

As a result of extensive research on chemically amplified photoresist compositions for ArF excimer lasers, particularly positive photoresist compositions, the present inventors have a monomer unit having a specific butyrolactone ring and an acid-dissociable protecting group. By using a copolymer containing a (meth) acrylate unit as a resin component, it has good transparency with respect to an ArF excimer laser and exhibits excellent sensitivity, resist pattern shape, dry etching resistance and adhesion. Further, it has been found that a chemically amplified photoresist composition having a high affinity for alkali can be obtained, and the present invention has been made based on this finding.
Here, (meth) acrylate means acrylic acid ester and methacrylic acid ester.

（式中のＲ¹は水素原子又はメチル基である）
で表わされる構成単位と（ｂ）酸解離性保護基を有する（メタ）アクリル酸エステルから誘導される構成単位を含むことを特徴とする（メタ）アクリレート共重合体、及びγ‐ブチロラクトン‐２‐イル（メタ）アクリレートと酸解離性保護基を有する（メタ）アクリル酸エステルとを共重合させることを特徴とする、上記の（メタ）アクリレート共重合体の製造方法を提供するものである。 That is, the present invention relates to (a) a structural unit derived from γ-butyrolactone-2-yl (meth) acrylate, that is, a general formula

(R ¹ in the formula is a hydrogen atom or a methyl group)
In include structural units represented by the (b) having an acid dissociable protecting group (meth) structural unit that will be derived from an acrylate ester wherein the (meth) acrylate copolymer, and γ- butyrolactone-2 The present invention provides a method for producing the above (meth) acrylate copolymer, which comprises copolymerizing yl (meth) acrylate and (meth) acrylic acid ester having an acid dissociable protecting group.

  Examples of the structural unit (b) include, for example, a hydrogen atom of a carboxyl group of acrylic acid or methacrylic acid, a tert-butyl group, a 2-tetrahydropyranyl group, a 2-tetrahydrofuranyl group, a 1-methylcyclohexyl group, a 1- Protect carboxyl groups such as those substituted by methyl adamantyl group, 1-ethoxyethyl group and 1-methoxypropyl group, or esters of acrylic acid or methacrylic acid with 2-hydroxy-3-pinanone with acid-dissociable substituents And structural units derived from acrylic acid or methacrylic acid.

  In addition to the structural units (a) and (b) described above, the copolymer of the present invention further comprises an ethylenic double as a structural unit (c) as desired in order to impart alkali solubility as desired. A structural unit derived from an unsaturated carboxylic acid having a bond can be included. Examples of such unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, and fumaric acid. Among these, acrylic acid and methacrylic acid are particularly preferable.

The copolymer of the present invention may further contain a monomer unit conventionally used as a structural unit in the chemically amplified resin component, if desired. As such, the hydrogen atom of the carboxyl group of (meth) acrylic acid can be adamantyl group, cyclohexyl group, naphthyl group, benzyl group, 3-oxocyclohexyl group, bicyclo [2,2,1] heptyl group, tricyclo group. A structural unit derived from a (meth) acrylic acid ester substituted with a non-acid-dissociable substituent, such as those substituted with a decanyl group and an acetonyl group, or a carboxyl group such as an ester of acrylic acid or methacrylic acid and terpineol; , alkyl esters of (meth) a acrylic acid, for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n- butyl acrylate, isobutyl acrylate, n- hexyl acrylate, octyl acrylate, 2-ethylhexyl a Relate, lauryl acrylate, and 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and the corresponding methacrylates and amides of acrylic acid or methacrylic acid such as acrylamide, N- methylol acrylamide, diacetone acrylamide and the corresponding methacrylamides, Examples thereof include structural units derived from compounds having an ethylene bond such as acrylonitrile, methacrylonitrile, vinyl chloride, and ethyl vinyl ether.

（式中のＲ¹は前記と同じ意味をもち、Ｘはメチレン基又はアルキル置換メチレン基である）
で表わされる（メタ）アクリレート及び一般式

（式中のＲ¹は前記と同じであり、Ｒ²は水素原子又は低級アルキル基、Ｙは酸素原子、メチレン基又はアシル基を有するメチレン基、Ｚはメチレン基、アルキル置換メチレン基又はカルボニル基である）
で表わされる（メタ）アクリレートから誘導された構成単位であってもよい。 Other general formulas

(Wherein R ¹ has the same meaning as described above, and X is a methylene group or an alkyl-substituted methylene group)
(Meth) acrylate represented by the general formula

(Wherein R ¹ is as defined above, R ² is a hydrogen atom or a lower alkyl group, Y is a methylene group having an oxygen atom, a methylene group or an acyl group, Z is a methylene group, an alkyl-substituted methylene group or a carbonyl group) Is)
A structural unit derived from (meth) acrylate represented by

Examples of the (meth) acrylate represented by the general formula (II) include 2-oxacyclopentan-4-one-1-yl ester of acrylic acid, 3-methyl-2-oxacyclopentane-4-one-1- Mention may be made of yl esters or 3,3-dimethyl-2-oxacyclopentan-4-one-1-yl esters and the corresponding esters of methacrylic acid.

The (meth) acrylate represented by the general formula (III) includes 2,4-dioxacyclohex-5-one-1-yl ester of acrylic acid, 3-methyl-2,4-dioxacyclohexene. Sa-5-one-1-yl ester, 3,3-dimethyl-2,4-dioxacyclohex-5-one-1-yl ester, 1-methyl-2-oxacyclohexa-3,5-dione Mention may be made of -1-yl esters, 1-methyl-4-acetyl-2-oxacyclohexa-3,5-dione-1-yl esters and the corresponding esters of methacrylic acid.

（式中のＲ¹は前記と同じ意味をもつ）
で表わされる（メタ）アクリレートを用いて導入することができる。この一般式（ＩＶ）で表わされる（メタ）アクリレートは、新規化合物でこれまで化学増幅型ホトレジストの樹脂成分である、酸の作用によりアルカリに対する溶解性が増加するアクリル系樹脂を製造する際の単量体として使用されることが未だ知られていなかった化合物である。 The structural unit (a) of the copolymer of the present invention has the general formula

(Wherein R ¹ has the same meaning as above)
It can introduce | transduce using (meth) acrylate represented by these. This (meth) acrylate represented by the general formula (IV) is a novel compound, which has been used as a resin component of a chemically amplified photoresist, and has been used in the production of acrylic resins whose solubility in alkali is increased by the action of acid. It is a compound not yet known to be used as a monomer.

で表わされる含酸素複素環ヒドロキシ化合物を反応させることにより得られる。 The monomer represented by the general formula (IV) is, for example, a compound of (meth) acrylic acid according to a conventional esterification method.

It is obtained by reacting an oxygen-containing heterocyclic hydroxy compound represented by the formula:

The copolymer of the present invention is the formed these monomer units, particularly preferred are represented by the above general formula (IV) (meth) 2 with acrylic acid ester - tetrahydropyranyl acrylate, 2 - tetrahydrofuranyl acrylate, 1 - ethoxyethyl acrylate, 1 - methoxy acrylate and the corresponding hydroxyl of the carboxyl group such as methacrylates and protected with an acid dissociable substituent acetal (meth) acrylate especially the 2-tetrahydropyranyl A copolymer using (meth) acrylate as a monomer is advantageous because it has high acid dissociation properties and is less dependent on post-exposure heat treatment.

  In the copolymer of the present invention, it is necessary to include the structural unit (a) represented by the general formula (I) as described above, and the proportion of the structural unit (a) A range of 20 to 80 mol%, particularly 50 to 80 mol% is preferable in terms of improving dry etching resistance, adhesion, and contrast with unexposed areas.

The copolymer of the present invention can be used as a chemically amplified resist composition in combination with an acid generator. This acid generator can be arbitrarily selected from compounds known so far as acid generators for chemically amplified resist compositions.
Examples of such compounds include the following.

(A) Bissulfonyldiazomethane;
Bis (p-toluenesulfonyl) diazomethane, bis (1,1-dimethylethylsulfonyl) diazomethane, bis (cyclohexylsulfonyl) diazomethane, bis (2,4-dimethylphenylsulfonyl) diazomethane, and the like.

(B) Nitrobenzyl derivatives;
p-toluenesulfonic acid 2-nitrobenzyl, p-toluenesulfonic acid 2,6-dinitrobenzyl and the like.

(C) sulfonic acid ester;
Pyrogallol trimesylate, pyrogallol tritosylate, etc.

(D) Onium salts;
Diphenyliodonium hexafluorophosphate, (4-methoxyphenyl) phenyliodonium trifluoromethanesulfonate, bis (p-tert-butylphenyl) iodonium trifluoromethanesulfonate, triphenylsulfonium hexafluorophosphate, (4-methoxyphenyl) diphenylsulfonium trifluoro Lomethanesulfonate, (p-tert-butylphenyl) diphenylsulfonium trifluoromethanesulfonate, and the like.

(E) benzoin tosylate and its alkyl-substituted product;
Benzoin tosylate, α-methylbenzoin tosylate, etc.

(F) a halogen-containing triazine compound;
2- (4-Methoxyphenyl) -4,6-bis (trichloromethyl) -1,3,5-triazine, 2- (4-methoxynaphthyl) -4,6-bis (trichloromethyl) -1,3 5-triazine, 2- [2- (2-furyl) ethenyl] -4,6-bis (trichloromethyl) -1,3,5-triazine, 2- [2- (5-methyl-2-furyl) ethenyl ] -4,6-bis (trichloromethyl) -1,3,5-triazine, 2- [2- (3,5-dimethoxyphenyl) ethenyl] -4,6-bis (trichloromethyl) -1,3 5-triazine, 2- [2- (3,4-dimethoxyphenyl) ethenyl] -4,6-bis (trichloromethyl) -1,3,5-triazine, 2- (3,4-methylenedioxyphenyl) -4,6-bis (trichloromethyl) ) -1,3,5-triazine, 2,4,6-tris (2,3-dibromopropyl) -1,3,5-triazine.

(G) an oxime sulfonate having a cyano group;
α- (methylsulfonyloxyimino) phenylacetonitrile, α- (methylsulfonyloxyimino) -4-methoxyphenylacetonitrile, α- (trifluoromethylsulfonyloxyimino) phenylacetonitrile, α- (trifluoromethylsulfonyloxyimino)- 4-methoxyphenylacetonitrile, α- (ethylsulfonyloxyimino) -4-methoxyphenylacetonitrile, α- (propylsulfonyloxyimino) -4-methylphenylacetonitrile, α- (methylsulfonyloxyimino) -4-bromophenylacetonitrile , Α- (methylsulfonyloxyimino) -1-cyclopentenylacetonitrile, α- [1- (or 2-) naphthylsulfonyloxyimino] -4-methoxybenzylcyanide, - (10-camphorsulfonyl) -4-methoxybenzyl cyanide and the like.

  Particularly preferred among these acid generators are onium salts and oxime sulfonates having a cyano group. The blending ratio of the component (A) and the component (B) is 0.5 to 30 parts by weight, preferably 1 to 10 parts by weight with respect to 100 parts by weight of the component (A). When the amount is less than this range, image formation cannot be performed, and when the amount is larger, a uniform solution is not obtained and the storage stability is lowered.

  In addition to the copolymer and acid generator of the present invention, the photoresist composition may contain additive components commonly used in ordinary chemically amplified photoresists, such as antihalation agents, antioxidants, A stabilizer, an adhesion improver, a plasticizer, a colorant, a surfactant, an additional resin, an organic carboxylic acid, an amine and the like can be added in an amount that does not impair the properties of the composition of the present invention.

  The photoresist composition thus prepared is preferably used in the form of a solution in which each of the above components is dissolved in a solvent. Examples of such solvents include ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl isoamyl ketone, 2-heptanone, ethylene glycol, ethylene glycol monoacetate, diethylene glycol, diethylene glycol monoacetate, propylene glycol, propylene glycol monoacetate, Polypropylene and its derivatives such as dipropylene glycol or monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether or monophenyl ether of dipropylene glycol monoacetate, cyclic ethers such as dioxane, lactic acid Methyl, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxypropionate Can be exemplified Le, esters such as ethyl ethoxypropionate. These may be used alone or in combination of two or more.

  In order to form a pattern using this photoresist composition, for example, this photoresist composition is applied onto a substrate such as a silicon wafer and prebaked at 70 to 150 ° C. for 30 to 150 seconds to form a resist layer. Then, irradiation with radiation such as ArF excimer laser is performed through a mask, heating at about 70 to 150 ° C. is performed for 30 seconds to 150 seconds, and then development is performed. As the resist developing solution, an alkaline aqueous solution can be used. By development, the exposed portion is dissolved in the alkaline aqueous solution, and a positive pattern is obtained. As the alkaline aqueous solution, for example, an aqueous solution of tetramethylammonium hydroxide, choline, or the like can be used.

  According to the present invention, a novel acrylic acid or methacrylic acid ester copolymer suitable as a resin component of a chemically amplified resist is provided.

  Next, the best mode for carrying out the present invention will be described by way of examples, but the present invention is not limited thereto.

で表わされるメタクリル酸エステルを得た。
この生成物の¹Ｈ−ＮＭＲ（溶媒：アセトン−ｄ₆）を測定した結果、１．９２ｐｐｍ、２．３０〜２．５０ｐｐｍ、３．９０〜４．１０ｐｐｍ、５．２０ｐｐｍ、５．６０ｐｐｍ、６．１２ｐｐｍにピークが認められた。 After dissolving 55.1 g (0.54 mol) of 3-hydroxy-1-oxacyclopentan-2-one and 60 g (0.60 mol) of triethylamine in 200 ml of tetrahydrofuran and stirring sufficiently, methacryloyl chloride 62. 4 g (0.60 mol) was added dropwise at 25 ° C. over 1 hour.
Subsequently, after making it react at 25 degreeC for 24 hours, the reaction liquid was filtered. The solvent of the filtrate was distilled off, and the remaining product was dissolved in 300 ml of diethyl ether and washed 10 times with 10 wt% sodium hydroxide solution. Then, it is purified by column chromatography using n-heptane as a solvent, and as a colorless liquid, the formula

The methacrylic acid ester represented by this was obtained.
As a result of measuring ¹ H-NMR (solvent: acetone-d ₆ ) of this product, 1.92 ppm, 2.30-2.50 ppm, 3.90-4.10 ppm, 5.20 ppm, 5.60 ppm, 6 A peak was observed at 12 ppm.

17.4 g of the methacrylic acid ester thus obtained (0.094 mol, mol% based on the total monomer is 75 mol%), 5.3 g of 2 -tetrahydropyranyl methacrylate (0.031 mol, mol% based on the total monomer) 25 mol%) was dissolved in 560 g of tetrahydrofuran, 0.81 g of azobisisobutyronitrile was added as a reaction initiator, and a polymerization reaction was carried out at 75 ° C. for 3 hours. After completion of the reaction, the reaction product was poured into 5 liters of n-heptane to precipitate a polymer, and the obtained copolymer was dried under reduced pressure at room temperature. Thus, a copolymer of the above methacrylic acid ester and 2-tetrahydropyranyl methacrylate was obtained. The yield of this copolymer was 14.9 g, the weight average molecular weight was 13,500, and the degree of dispersion was 2.01.

Reference Example 100 parts by weight of the polymer obtained in Example 1 and 2 parts by weight of bis (p-tert-butylphenyl) iodonium trifluoromethanesulfonate were dissolved in 680 parts by weight of propylene glycol monomethyl ether acetate to obtain a positive resist solution. .
Next, this resist solution was applied onto a silicon wafer using a spinner and dried at 100 ° C. for 90 seconds on a hot plate to form a resist layer having a thickness of 0.5 μm. Next, after selectively irradiating an ArF excimer laser (193 nm) with an ArF exposure apparatus (manufactured by Nikon Corp.), it was subjected to PEB treatment at 110 ° C. for 90 seconds, and then paddled with 2.38 wt% tetramethylammonium hydroxide aqueous solution for 65 seconds Developed, washed with water for 30 seconds and dried.

The exposure time for forming a 0.25 μm line-and-space formed by such an operation as 1: 1 was measured in mJ / cm ² (energy amount) unit as a sensitivity, and found to be 6.0 mJ / cm ^2. It was.
Further, when the cross-sectional shape of the 0.25 μm resist pattern formed in this way was observed with an SEM (scanning electron microscope) photograph, it was a rectangular resist pattern perpendicular to the substrate.
Further, by such an operation, a resist pattern of 0.20 μm was resolved, and there was no pattern collapse.
Next, using tetrafluoromethane gas as an etching gas, dry etching is performed with an etching apparatus OAPM-406 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), and the dry etching resistance is evaluated by the amount of film reduction per unit time. When 0, it was 1.1.

で表わされるアダマンチルメタクリレートと２‐テトラヒドロピラニルメタクリレートとメタクリル酸との共重合体を得た。収量は１６．０ｇであり、重量平均分子量は１６，５００で、分散度は２．２０であった。 Comparative Example 1
Instead of methacrylates of the formula (VI) in Example 1, mol% with the amount of A adamantyl methacrylate of 50 mol% to the total monomers in the same manner as in Example 1, wherein

In A represented adamantyl methacrylate and 2 - to obtain a copolymer of tetrahydropyranyl methacrylate and methacrylic acid. The yield was 16.0 g, the weight average molecular weight was 16,500, and the degree of dispersion was 2.20.

In the reference example, a positive resist solution was prepared in the same manner as in the reference example except that the polymer was replaced with the same amount of the above polymer, and then a resist pattern was formed under the same conditions as in the reference example.
The sensitivity of the definition similar to the reference example at that time was 15 mJ / cm ² , and a resist pattern of 0.30 μm or less could not be resolved.
The dry etching resistance with the same definition as in the reference example was examined and found to be 1.0.

で表わされる化合物のメタクリレート１７．２ｇ（０．０９４モル、全モノマーに対するモル％は７５モル％）を用い、実施例１と全く同様にして、上記モノマーとメタクリル酸２‐テトラヒドロピラニルメタクリレートの共重合体を得た。この共重合体の収量は１４．７ｇであり、重量平均分子量は１４，５００で、分散度は、１．９８であった。 Comparative Example 2
Instead of methacrylates of the formula (VI) in Example 1, wherein

Methacrylates 17.2g of the compound represented by in (0.094 mol, mol% to total monomer is 75 mol%) using, in the same manner as in Example 1, the monomer and methacrylic acid 2-tetrahydropyranyl methacrylate A copolymer was obtained. The yield of this copolymer was 14.7 g, the weight average molecular weight was 14,500, and the degree of dispersion was 1.98.

Using the above copolymer, a positive resist solution was prepared in the same manner as in the reference example, and then a resist pattern was formed under the same conditions as in the reference example.
The sensitivity with the same definition as in the reference example at this time is 5.0 mJ / cm ² , and the resist pattern of 0.25 μm was resolved by such an operation, and the pattern was not collapsed. When the cross-sectional shape of the 30 μm resist pattern was observed with an SEM (scanning electron microscope) photograph, it was a trapezoidal resist pattern relative to the substrate.
Similarly, when the dry etching resistance was examined, it was 1.5.

  The copolymer of the present invention is suitable as a resin component of a chemically amplified resist.

Claims (5)

Characterized in that it comprises a (a) .gamma.-butyrolactone-2-yl (meth) structural units derived from acrylate and (b) having an acid dissociable protecting group (meth) structural unit that will be derived from an acrylate ester (Meth) acrylate copolymer. The (meth) acrylate copolymer according to claim 1, further comprising (c) a structural unit derived from an unsaturated carboxylic acid having an ethylenic double bond, in addition to the structural unit (a) and the structural unit (b). The (meth) acrylate copolymer according to claim 1 or 2, wherein the structural unit (b) is a structural unit derived from 2 -tetrahydropyranyl methacrylate . (a) γ-butyrolactone-2-yl (meth) acrylate characterized by copolymerizing γ-butyrolactone-2-yl (meth) acrylate and (meth) acrylic acid ester having an acid dissociable protecting group constitutional unit (b) having an acid dissociable protecting group (meth) manufacturing method comprising the structural units that will be derived from an acrylate ester (meth) acrylate copolymer derived from. The method for producing a (meth) acrylate copolymer according to claim 4, wherein the (meth) acrylic acid ester having an acid-dissociable protecting group is 2-tetrahydropyranyl (meth) acrylate .