JP3063539B2 - Positive photoresist composition and pattern forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive photoresist composition and a pattern forming method which have high sensitivity and high resolution resist performance and can be effectively used for i-line exposure.

[0002]

2. Description of the Related Art The development of exposure apparatus and photoresist used in semiconductor lithography is rapid, exceeding the production of 16 MDRAM with a design rule of 0.5 .mu.m by i-line exposure method to 0.35 .mu.m. 64MDRAM with 0.30μm design rule
Efforts are being made to push its limits to the production of.

[0003] The photoresist composition used here is a positive photoresist composition mainly containing an alkali-soluble resin, especially a novolak resin and a photosensitive agent. As this photosensitizer, a 1,2-naphthoquinone-2-diazidosulfonic acid compound is generally used. This compound itself acts as a dissolution inhibitor to reduce the alkali solubility of the novolak resin, decomposes by light irradiation to produce an alkali-soluble substance, indene carboxylic acid, which promotes the alkali solubility of the novolak resin, It is an ideal compound that increases the difference in alkali dissolution rate before and after exposure.

However, 1,2-naphthoquinone-2-diazidosulfonic acid esters as photosensitizers generally have high hydrophobicity and are not suitable for a good solvent for a novolak resin frequently used in an i-line exposure method. There was a problem in compatibility. The above compounds are insoluble or hardly soluble in alcohols such as methanol and ethanol (Japanese Patent Publication No. Sho 3).
7-13109 and 37-1953), especially when the solubility is low, it crystallizes and precipitates during storage,
It is not practical. In recent years, a mixed solvent of N, N-dimethylformamide and alkylene glycol monoalkyl ether acetate has been proposed (see JP-A-2-115847), but none of them show satisfactory solubility. Was the current situation.

On the other hand, the action of the above photosensitive agent is mainly
This is due to the action of the 2-naphthoquinone-2-diazidosulfonic acid group, and the selection of a ballast molecule is extremely important for fully exerting this action. Conventionally, for ballast molecules that bind photosensitive groups, unbound OH
It has been practiced to balance the total number of OH groups and the number of 1,2-naphthoquinone-2-diazidosulfonyl groups in which groups should remain. That is, OH having no 1,2-naphthoquinone-2-diazidosulfonyl group in the photosensitive agent
This is because the group is related to the alkali dissolution inhibiting action on the novolak resin (the difference in the dissolution rate between the exposed and unexposed parts) and affects the resist performance. Generally, it is easily speculated that photosensitizers are hydrophobic, and unbound OH groups increase hydrophilicity and can greatly affect resist performance and compatibility with resins and solvents (new photopolymer technology). Development, published by Toray Research Center, pp. 219-220).

[0006] Therefore, there is a demand for the development of a photosensitive agent which is satisfactory in compatibility with a solvent.

[0007] The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a positive resist composition and a pattern forming method which are excellent in compatibility with a solvent, contain a high-sensitivity and high-performance photosensitive agent, and are excellent in sensitivity and resolution of resist performance.

[0008]

The present inventors have made intensive studies to achieve the above object, and as a result, have found that a positive photoresist composition containing an alkali-soluble resin and a photosensitizing agent as main components is used as a photosensitizing agent. 1,2 of 2,6-bis (1-hydroxy-4-alkoxycarbonylmethylphenyl) -p-cresol represented by the following general formula (1)
-Positive photoresist composition comprising naphthoquinone-2-diazide-5-sulfonic acid (partial) ester has high sensitivity and high resolution resist performance, and this positive photoresist composition is coated on a substrate. After coating and pre-baking, preferably, a water-soluble contrast enhancer layer containing a nitrone compound represented by the following general formula (2) as a main component is formed thereon and exposed, and then the water-soluble contrast enhancer layer is formed. It has been found that high-quality patterns can be formed by washing and removing, followed by alkali development.

[0009]

Embedded image (Where D is a hydrogen atom or 1,2-naphthoquinone-
A 2-diazido-5-sulfonyl group, at least one of which is a 1,2-naphthoquinone-2-diazido-5-sulfonyl group. R is a lower alkyl group. )

[0010]

Embedded image (Wherein, R ¹ , R ² , and R ³ are the same or different alkyl groups, aryl groups, or hydrogen atoms;
^{4 to} R ⁸ are the same or different alkyl groups,
A hydrogen atom or a carboxy group, and at least one of R ^{4 to} R ⁸ is a carboxy group. X is an alkoxy group represented by R ⁹ O—, a dialkylamino group represented by R ¹⁰ R ¹¹ N—, or a hydrogen atom; R ⁹ is an alkyl group;
R ¹⁰ and R ¹¹ are the same or different alkyl groups. n is 0, 1 or 2. )

In this case, the compound of the above formula (1) is 1,
By introducing a highly hydrophilic functional group into the 2-naphthoquinone-2-diazido-5-sulfonyl group, the compatibility of the alkali-soluble resin with a good solvent is improved, and the sensitivity and resolution of the resist performance are improved. It has been found that the positive resist composition of the present invention described above is effective, reliable and advantageously capable of forming a pattern with a resolution of half a micron or less in an i-line exposure method, and has led to the present invention. It is a thing.

Accordingly, the present invention provides a positive photoresist composition comprising an alkali-soluble resin and a photosensitizer as main components, wherein the photosensitizer is represented by the general formula (1):
Positive type characterized by comprising 1,2-naphthoquinone-2-diazido-5-sulfonic acid (partial) ester of 6-bis (1-hydroxy-4-alkoxycarbonylmethylphenyl) -p-cresol. Provided is a photoresist composition and a pattern forming method, which comprises applying the positive photoresist composition on a substrate, prebaking, exposing, and then alkali developing.

Now, the present invention will be described in further detail. The positive resist composition of the present invention comprises an alkali-soluble resin and a photosensitive agent as main components.

As the alkali-soluble resin, for example, novolak resin, styrene-maleic anhydride copolymer, polyvinyl hydroxybenzoate, polyhydroxystyrene, carboxyl group-containing acrylic resin, acetone-pyrogallol resin and the like can be used. Novolak resins are preferred.

The cresol novolak resin has a molecular weight (weight average (Mw), GPC polystyrene conversion) of 1
000 to 20,000, especially 3000 to 100
00 is preferred. If the molecular weight is lower than 1,000, the heat resistance may decrease, and the molecular weight may be 2,000.
When it is higher than 0, the heat resistance is improved, but the alkali solubility decreases with an increase in the molecular weight, and the resolution may deteriorate.

In the present invention, 2,6-bis (1-hydroxy-4-) represented by the following general formula (1) is used as a photosensitive agent.
It is characterized in that 1,2-naphthoquinone-2-diazido-5-sulfonic acid (partial) ester of (alkoxycarbonylmethylphenyl) -p-cresol is compounded.

[0017]

Embedded image (Where D is a hydrogen atom or 1,2-naphthoquinone-
A 2-diazido-5-sulfonyl group, at least one of which is a 1,2-naphthoquinone-2-diazido-5-sulfonyl group. R is a group having 1 carbon atom such as a methyl group or an ethyl group.
To 5 lower alkyl groups. )

The compound of the above formula (1) is, for example, 2,6-
Bis (hydroxymethyl) -p-cresol is reacted with hydroxyphenylacetic acid or hydroxyphenylacetic acid ester in the presence of an acid catalyst to give 2,6-bis (1-hydroxy-4-alkoxycarbonylmethylphenyl)-
After synthesizing p-cresol, 1,2-naphthoquinone-2-diazido-5-sulfonyl chloride is added thereto, and the reaction can be performed by reacting in the presence of amines.

In this case, the reaction ratio between 2,6-bis (hydroxymethyl) -p-cresol and hydroxyphenylacetic acid or hydroxyphenylacetic acid ester is the former 1
It is desirable to use the latter 2 mol or more, particularly 4 to 8 mol, per mol. If the amount is less than 2 mol, the polymer component may increase.

As the acid catalyst, hydrochloric acid, sulfuric acid, oxalic acid and the like can be used, but hydrochloric acid is preferred because the production of polymer components can be suppressed as much as possible. The acid catalyst is
It can be used in an amount of 0.1 to 20% based on the reactants, but is not particularly limited thereto.

The reaction is preferably carried out in a solvent such as methanol, and the reaction can be carried out at 20 to 60 ° C. for 5 to 15 hours.

In a methanol solvent in the presence of an acid catalyst, the esterification reaction proceeds at the same time even when hydroxyphenylacetic acid is used, whereby an ester form is obtained. The product is a mixture of polynuclears, mainly 2,6-bis (1-hydroxy-4-methoxycarbonylmethylphenyl) -p-cresol.

Next, 2,6-bis (1-hydroxy-
4-alkoxycarbonylmethylphenyl) -p-cresol is reacted with 1,2-naphthoquinone-2-diazido-5-sulfonyl chloride, and the molar ratio in this case is preferably in the range of 1/1 to 1/3. .

Examples of the amines include triethylamine, tributylamine, pyridine, diazabicyclooctane and the like, and the use amount thereof is desirably equivalent to 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride.

The reaction can be carried out according to a conventional method, and is preferably carried out in a solvent such as dioxane at 5 to 30 ° C. for 2 to 8 hours. After completion of the reaction, the reaction mixture is added to an aqueous acid solution such as hydrochloric acid to form a precipitate, which is filtered and dried to obtain the desired compound of the above formula (1).

The esterification rate (theoretical esterification rate) of the compound of the above formula (1) synthesized by the above method is 2,6.
It can be adjusted by the mixing ratio of -bis (1-hydroxy-4-alkoxycarbonylmethylphenyl) -p-cresol and 1,2-naphthoquinone-2-diazido-5-sulfonyl chloride. 9
0% is preferred.

The amount of the photosensitive agent of the above formula (1) is 1 to 100 parts (parts by weight, hereinafter the same) of the alkali-soluble resin.
0 to 50 parts, especially 20 to 40 parts, is preferred. The amount is 1
If the amount is less than 0 parts, the ability to reduce the alkali dissolution rate of the resin is not exhibited, or the increase in the alkali dissolution rate after photolysis by exposure is poor, and the performance as a resist may not be exhibited, and more than 50 parts In addition, the resist performance may decrease as the exposure amount increases (sensitivity decreases). This may be due to incomplete dissolution inhibition by exposure, or a reaction with the resin due to photolysis. Ideally, as long as the dissolution rate difference before and after exposure can be obtained, the blending amount of the photosensitive agent is preferably as small as possible within the above range.

The composition of the present invention preferably contains a solvent. Examples of the solvent include cellosolve esters such as ethyl cellosolve acetate and methyl cellosolve acetate, glycol ethers such as ethylene glycol monomethyl ether and diethylene glycol monomethyl ether, and ethers such as 1,2-diethoxyethane and 1,2-dibutoxyethane. And esters such as ethyl acetate, diethyl malonate and ethyl lactate, and ketones such as cyclopentanone and cyclohexane. It is preferable to adjust the compounding amount of the solvent according to the required resist film thickness. However, there is no inconvenience if the solubility is high, and the solvent is usually adjusted as a 50 to 90% solution.

It is desirable to add a surfactant in order to improve the coating properties and striation of the composition. Specific examples of the surfactant include nonionic surfactants such as polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, and polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonylphenyl ether; Florad FC-430; FC
-431 (manufactured by Sumitomo 3M Limited) and the like. The amount of the surfactant is 0.01 to
0.1% is preferred.

Further, a sensitizer, a storage stabilizer, a light absorbing agent, an adhesion aid, and the like can be added as optional components to the composition of the present invention, and the amounts of these additives do not impair the effects of the present invention. Can be used as a normal amount.

In the present invention, the above-mentioned positive type photoresist composition is applied on a substrate by a usual spin coater at a rotation speed of 2000 to 5000 rpm to a thickness of about 0.5 to 5 μm, and prebaked. After that, the pattern can be formed by exposing and then developing with alkali.

Further, after the positive photoresist composition is coated on a substrate and prebaked, a water-soluble contrast enhancer layer is formed thereon and exposed, and then the water-soluble contrast enhancer layer is washed off with water. Then, it is more preferable to perform pattern formation by performing alkali development, and according to this method, a pattern with a higher depth of focus can be formed.

In this case, as the water-soluble contrast enhancer, those containing a nitrone compound represented by the following formula (2) as a main component are preferably used.

[0034]

Embedded image (Wherein, R ¹ , R ² , and R ³ are the same or different alkyl groups, aryl groups, or hydrogen atoms;
^{4 to} R ⁸ are the same or different alkyl groups,
It is a hydrogen atom or a carboxy group, and at least one is a carboxy group. X is an alkoxy group represented by R ⁹ O—, a dialkylamino group represented by R ¹⁰ R ¹¹ N—, or a hydrogen atom, R ⁹ is an alkyl group, and R ¹⁰ and R ¹¹ are the same or different. It is an alkyl group. n is 0, 1 or 2. )

In the above formula (2), R ¹ , R ² , R
³ is preferably an alkyl group having 1 to 4 carbon atoms, for example, a methyl group, an ethyl group, a butyl group, an aryl group having 6 to 8 carbon atoms, for example, a phenyl group or a hydrogen atom. R ^{4 to} R ⁸ are preferably an alkyl group having 1 to 4 carbon atoms, for example, a hydrogen atom or a carboxyl group such as a methyl group, an ethyl group or a propyl group. X is an alkoxy group represented by R ⁹ O—, a dialkylamino group represented by R ¹⁰ R ¹¹ N—, or a hydrogen atom, and R ⁹ is preferably a methyl group, an ethyl group, or a propyl group having 1 to 3 carbon atoms. Alkyl groups such as R ¹⁰ , R ¹¹
Are the same or different, and preferably have 1 to 1 carbon atoms.
2 alkyl groups such as methyl group and ethyl group.

Specific examples of such a nitrone compound of the above formula (2) include α- [p- (diethylamino) styryl] -N- (2-methyl-4-carboxyphenyl)
Nitrone, α- [p- (dimethylamino) styryl]-
N- (2-methyl-4-carboxyphenyl) nitrone, α- [p- (diethylamino) phenyl] -N-
(2-methyl-4-carboxyphenyl) nitrone and the like are exemplified.

The amount of the nitrone compound of the above formula (2) is preferably 2 to 10% in the water-soluble contrast enhancer.
used.

Other components of the water-soluble contrast enhancer containing a nitrone compound of the above formula (2) as a main component include, for example, basic compounds such as tris (hydroxymethyl) aminomethane and tetraethylammonium hydroxide; Further, a copolymer of polyvinylpyrrolidone and polyacrylic acid, water, and the like can be blended as the film material, and these components can be used in a usual amount as long as the effects of the present invention are not impaired.

[0039]

The positive photoresist composition of the present invention has good compatibility with a good solvent in an alkali-soluble resin of a photosensitive agent, and has high sensitivity and high resolution resist performance. It can be effectively used for the exposure method. Further, according to the pattern forming method of the present invention, a high-quality pattern having the above-described excellent resist performance can be formed.

[0040]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples.

[Synthesis Example 1] Preparation of cresol novolak resin: m-neck was placed in a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser.
43.3 g (0.40 mol) of cresol, 64.9 g (0.60 mol) of p-cresol, 52 g of a 37% formalin aqueous solution and 3 g of oxalic acid were charged, and the temperature was raised to 100 ° C. with stirring, followed by a reaction for 16 hours. After the reaction, the resultant was dissolved in 300 ml of methyl isobutyl ketone, washed sufficiently with water, and then the solvent was removed.
C, a cresol novolak resin of 4000 in terms of polystyrene was obtained in a yield of 85 g.

[Synthesis Example 2] Preparation of photosensitizer: 228 g (15 mol) of hydroxyphenylacetic acid and 698 g of 5% hydrochloric acid were placed in a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser.
The temperature was maintained at 50 ° C., and 42 g of 2,6-bis (hydroxymethyl) -p-cresol (0.25 m
ol) in 450 g of methanol was added over 2 hours and then kept at 50 ° C. for 10 hours. After cooling,
About 400 g of methyl isobutyl ketone was added, extracted, washed with water, and the solvent was removed. 175 g of the obtained highly viscous substance was dissolved in methanol and poured into water to remove excess methyl ester of hydroxyphenylacetic acid. Repeated reprecipitation,
55% of 2,6-bis (1-hydroxy-4-methoxycarbonylmethylphenyl) -p-cresol and 68 g of its higher homolog were obtained.

Next, 10 g of the above 2,6-bis (1-hydroxy-4-methoxycarbonylmethylphenyl) -p-cresol and 11.3 g of 1,2-naphthoquinone-2-diazido-5-sulfonyl chloride in 300 ml were added. Was dissolved in dioxane, and a mixed solution of triethylamine / dioxane = 4.3 g / 20 ml was gradually added dropwise thereto, and reacted at 20 ° C. for 4 hours. The reaction mixture was poured into 1 liter of a 1% aqueous hydrochloric acid solution, and the resulting precipitate was filtered off and sufficiently dried to obtain 1,6-bis (1-hydroxy-4-methoxycarbonylmethylphenyl) -p-cresol. , 2-Naphthoquinone-2-diazide-5
19.5 g of a photosensitizer was obtained as a sulfonic acid ester (65% ester, theoretical esterification ratio).

Similarly, 10 g of 2,6-bis (1-hydroxy-4-methoxycarbonylmethylphenyl) -p-cresol and 13.9 g of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride were converted into 22 g of a photosensitizer of the same esterified product (80% esterified product, theoretical esterification ratio) was obtained.

[Synthesis Example 3] 70.3 g (0.65 mol) of p-cresol, 5% aqueous hydrochloric acid 2
From a solution of 90 g and 42 g (0.25 mol) of 2,6-bis (hydroxymethyl) -p-cresol in 450 g of methanol, 2,6-bis (1-hydroxy-4-methylphenyl) -p-cresol was obtained. 64 g of an oligomer containing 45% were obtained. 10 g of this 2,6-bis (1-hydroxy-4-methylphenyl) -p-cresol mixture and 15.0 g of 1,2-naphthoquinone-2-diazido-5-sulfonyl chloride are dissolved in 300 ml of dioxane, Triethylamine / dioxane =
A 5.6 g / 20 ml mixture was gradually added dropwise, and 20
The reaction was performed at 4 ° C. for 4 hours. The reaction mixture was diluted with 1% aqueous hydrochloric acid 1
The resulting precipitate was filtered off and dried sufficiently to give 2,6-bis (1-hydroxy-4-
1,2-Naphthoquinone-2-diazide-5-sulfonic acid ester of methylphenyl) -p-cresol (6
21 g of a photosensitive agent (5% esterified product, theoretical esterification ratio) was obtained.

[Synthesis Example 4] 4.5 g of α- [p- (diethylamino) styryl] -N- (2-methyl-4-carboxyphenyl) nitrone, 2.0 g of tris (hydroxymethyl) aminomethane, and polyvinylpyrrolidone 60
% Of a copolymer polymer (trade name: Luviscol VA-64) containing 40% polyacrylic acid and 40% polyacrylic acid was thoroughly dissolved in 90 g of pure water to obtain a water-soluble contrast enhancer (CE).
M) was obtained.

Example 1, Comparative Example Preparation of photoresist composition: As shown in Table 1, 10 g of cresol novolak resin obtained above and 3 g of photosensitive agent
Was dissolved in 50 g of ethyl cellosolve acetate, and filtered using a micro filter having a pore size of 0.2 μm to prepare a photoresist composition.

The obtained photoresist composition was spin-coated on a silicone wafer treated with hexamethyldisilazane vapor using an auto coater, and prebaked at 90 ° C. for 60 seconds to obtain a film thickness of 1.05 μm. This resist-coated wafer is reduced by a projection exposure apparatus (Nikon Corporation, NS
R 1755i7A), exposure through a mask pattern, baking after exposure at 110 ° C. for 50 seconds (PEB)
Then, it was developed with a 2.38% aqueous solution of tetramethylammonium hydroxide for 1 minute, washed with water and dried to obtain a resist pattern (by an auto developer).

The obtained resist pattern was observed with a scanning electron microscope and evaluated by the following method. Table 1 shows the results. Sensitivity: The exposure amount at which the film thickness became 0 was displayed (threshold exposure amount). Remaining film ratio: expressed as a percentage before and after development of an unexposed portion. Resolution: The line and space image dimensions of the mask pattern and resist pattern reproduce 1: 1 (± 10% tolerance)
The minimum dimension at the exposure amount is indicated. Depth of focus: The value of 0.5 μm line / space was displayed. Resist shape: From the electron micrograph of the cross section, it was determined that the angle between the wafer surface and the resist wall surface was 85 degrees or more, which was good.

Example 2 The photoresist composition of Example 1 was formed by spin coating and prebaking at 90 ° C. for 60 seconds. The water-soluble CEM of Synthesis Example 4 was spin-coated on the 1.05 μm resist film to form a 0.18 μm film. The coated wafer is exposed through a mask pattern using a reduction projection exposure apparatus, exposed at 110 ° C. for 90 seconds, baked, first, CEL is peeled off with pure water, and then developer N
The image was developed with MD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.).

The resist pattern on the silicone wafer was observed with a scanning electron microscope and evaluated in the same manner as in Example 1. Table 1 shows the results.

From the results shown in Table 1, it was confirmed that the positive resist composition of the present invention can form a resist pattern with high sensitivity and high resolution by forming a pattern by the method of the present invention.

[0053]

[Table 1]

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Kamihara 1-10 Hitomi, Matsuida-machi, Usui-gun, Gunma Prefecture Inside Silicone Electronics Materials Research Laboratory, Shin-Etsu Chemical Co., Ltd. (72) Inventor Kazuhiro Nishikawa Matsui, Usui-gun, Gunma Prefecture Hitomi Tamachi 1-10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Technology Laboratory (56) References JP-A-6-138654 (JP, A) JP-A-62-164664 (JP, A) JP-A-57 -63526 (JP, A) JP-A-62-138843 (JP, A) JP-A-5-208949 (JP, A) JP-A-4-502519 (JP, A) (58) Fields investigated (Int. .7, DB name) G03F ^7/ 00-7/42 H01L 21/027

Claims (4)

(57) [Claims] 1. A positive photoresist composition comprising an alkali-soluble resin and a photosensitive agent as main components, wherein the photosensitive agent is 2,6-bis (1-hydroxy-4-alkoxycarbonyl) represented by the following general formula (1). Methylphenyl)
-A positive photoresist composition comprising 1,2-naphthoquinone-2-diazido-5-sulfonic acid (partial) ester of p-cresol. Embedded image (Where D is a hydrogen atom or 1,2-naphthoquinone-
A 2-diazido-5-sulfonyl group, at least one of which is a 1,2-naphthoquinone-2-diazido-5-sulfonyl group. R is a lower alkyl group. ) 2. A pattern forming method, comprising applying the positive photoresist composition according to claim 1 onto a substrate, prebaking, exposing, and then developing with an alkali. 3. The pattern forming method according to claim 2, wherein after prebaking, a water-soluble contrast-enhancing agent layer is formed thereon and exposed to light, and then the water-soluble contrast-enhancing agent layer is washed off with water. A pattern forming method comprising performing alkali development. 4. The pattern forming method according to claim 3, wherein the water-soluble contrast enhancer layer is formed of a water-soluble contrast enhancer containing a nitrone compound represented by the following general formula (2) as a main component. Embedded image (Wherein, R ¹ , R ² , and R ³ are the same or different alkyl groups, aryl groups, or hydrogen atoms;
^{4 to} R ⁸ are the same or different alkyl groups,
A hydrogen atom or a carboxy group, and at least one of R ^{4 to} R ⁸ is a carboxy group. X is an alkoxy group represented by R ⁹ O—, a dialkylamino group represented by R ¹⁰ R ¹¹ N—, or a hydrogen atom; R ⁹ is an alkyl group;
R ¹⁰ and R ¹¹ are the same or different alkyl groups. n is 0, 1 or 2. )