JPH0225850A - Radiation sensitive composition and pattern forming method using same - Google Patents

Abstract

PURPOSE:To improve the sensitivity and the resolution of the title composition by composing the title composition of a polymer contg. acetal or thioacetal group in the side chain of the polymer and a compd. capable of being generated and acid by the irradiation of radioactive rays. CONSTITUTION:The composition is composed of the polymer contg. acetal or thioacetal group in the side chain of the polymer and the compd. capable of being generated the acid. The compounding amount of the compd. is preferably 1-50pts.wt., further preferably 1-30pts.wt. per 100pts.wt. of the polymer. When the acetal group in the side chain of the polymer is attacked the acid generated by irradiation of radioactive rays, the acetal group is effectively converted to hydroxyl or carboxyl group whereby the difference of polarity, namely, the difference of the solubility between the irradiated part and the unirradiated part of the composition is produced. So that, the positive type or the negative type pattern of the composition is obtd. by selecting a developer. Accordingly, the resolution and the sensitivity of a pattern are improved.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a composition sensitive to radiation such as ultraviolet rays, electron beams, ion beams, or X-rays, and a pattern forming method using the same. More specifically, the present invention relates to a radiation-sensitive composition suitable for microfabrication and excellent in dry etching resistance, and a pattern forming method using the same.

[Conventional technology]

Conventionally, regarding radiation-sensitive compositions of a mixed system of a compound and a polymer that generate acid upon radiation irradiation, Japanese Patent Application Laid-open No. 59
-45439, JP-A-62-164045, JP-A-62
-39420. None of the prior art indicates the use of specific polymers in the present invention.

[Problem to be solved by the invention]

As the future of lithography, short wavelength lithography, especially lithography using excimer lasers, is attracting attention. However, at this exposure wavelength (248 nm), the conventionally used positive photoresist made of naphthoquinonediazide and novolac has strong absorption and cannot be used. The above-mentioned prior art has been reported as an attempt to solve this problem. However, when using excimer laser lithography, it is necessary to narrow the exposure wavelength band due to restrictions on exposure equipment, and as a result, the exposure intensity decreases, so high sensitivity of the resist is required. Furthermore, increasing the sensitivity of high-resolution resists remains a major challenge in electron beam lithography. An object of the present invention is to provide a high resolution and high sensitivity resist made of a new polymer.

[Means to solve the problem]

The above objective was to find a system in which the acid generated by exposure to light dissociates chemical bonds in the side chains of the polymer in a mixed system of acid precursor and polymer, and the solubility of the final product is significantly different from that of the initial polymer. achieved. The acid precursor used in the present invention is a conventionally known diazonium salt that has absorption in the short wavelength region. Onium salts such as diallyliodonium salts and triarylsulfonium salts and halogenated organic compounds are used. The counteranion of the salt in the present invention is a Lewis acid such as tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, trifluoroacetic acid, toluenesulfonate, etc. It is not limited to counter-anions. Desirable polymers in the present invention are vinyl polymers whose chemical bonds in the polymer side chains are efficiently dissociated by acid and whose final product has a polarity (solubility) that is significantly different from that of the polymer before dissociation. However, the invention is not limited to polymers obtained by vinyl addition polymerization. Other polymerizations such as polycondensation, polyaddition and addition condensation are also used to synthesize the polymers useful in the present invention. We found that the acid-labile groups generated by irradiation are acetals and thioacetals formed by reactions that protect the hydroxyl groups of alkali-soluble resins such as polyvinylphenol, polyvinylbenzoic acid, and novolak resins. Preferred polymers include poly(p-tetrahydropyranyloxystyrene), poly(p-tetrahydrofuranyloxystyrene), poly(p-tetrahydrothiopyranyloxystyrene), poly(p-tetrahydrothiopyranyloxystyrene), poly( p-vinylbenzoic acid tetrahydropyranyl ester), poly(p-vinylbenzoic acid tetrahydrofuranyl ester), poly(p-vinylbenzoic acid tetrahydrothiopyranyl ester), poly(p-vinylbenzoic acid tetrahydrothiopyranyl ester)
vinylbenzoic acid tetrahydrothiofuranyl ester),
These are poly(p-styrylacetic acid tetrahydropyranyl ester), poly(p-styrylacetic acid tetrahydrofuranyl ester), poly(p-styrylacetic acid tetrahydrothiopyranyl ester), and poly(p-styrylacetic acid tetrahydrothiofuranyl ester). The polymer may be a copolymer with the above polymer containing an acetal in its side chain, or may be a mixed system of a polymer compatible with the above polymer. In the composition of the present invention, the amount of the compound that generates an acid upon irradiation with radiation is preferably in the range of 1-50 parts by weight, preferably 1-3 parts by weight, based on 100 parts by weight of the polymer compound.
It is more preferable that the amount is 0 parts by weight, and less than 1 part by weight will have little effect. Moreover, if it exceeds 50 parts by weight, the properties of the coating film tend to deteriorate, so the above range is desirable. [Function] When the acetal of the polymer side chain is attacked by an acid generated by radiation irradiation, a hydroxyl group and a carboxylic acid are efficiently formed. This causes a difference in polarity, that is, a difference in solubility, between the irradiated area and the unirradiated area. Therefore, by selecting a developer, it is possible to obtain a positive or negative pattern. For example, if development is performed using a polar solvent, the exposed area has a high solubility in the developer;
The unexposed area has poor solubility and is difficult to dissolve, and a positive pattern can be obtained. On the other hand, if development is carried out using a non-polar solvent, the solubility of the unexposed areas in the developer is high and a negative pattern can be obtained. In the present invention, the acid generated by radiation irradiation acts as a catalyst for the acetal decomposition reaction. Since the acid is a catalyst, it only needs to be present in a small amount and is not consumed by the acetal decomposition reaction.

【Example】

Preferred synthetic methods for forming the desired polymers described above are now presented.

[Reference Example 1] Synthesis of poly(p-tetrahydrofuranyloxystyrene) 40 mQ of 2,3-dihydro-4H-pyran and 35 g of P-hydroxybenzaldehyde were dissolved in 230 mQ of ethyl acetate, and a catalytic amount of hydrochloric acid was added to the solution. added. This solution was stirred at room temperature for 24 hours. This solution was washed with 2% sodium hydroxide solution. After drying with sodium sulfate, it was concentrated under reduced pressure. 45 g of this product was dissolved in tetrahydrofuran and added to a tetrahydrofuran solution of 75 g of methyltriphenylphosphonium bromide and 52 g of potassium t-butoxy. After reacting for 2 hours, the solution was poured into ice water and extracted three times with ethyl acetate. The organic layer was dried over magnesium sulfate and concentrated. The crude product was purified by column chromatography. Add 1w of 7zobisisobutyronitrile (AIBN) to this toluene solution of p-tetrahydropyranyloxystyrene.
t,% was added and heated to 80° C. for 6 hours under nitrogen atmosphere. After cooling, the polymer was precipitated in petroleum ether and dried in vacuo to give the title polymer. Also, instead of p-hydroxybenzaldehyde, m-
When hydroxybenzaldehyde and 0-hydroxybenzaldehyde were used, the corresponding meta-substituted styrene and ortho-substituted styrene were obtained in exactly the same manner.

[Reference Example 2] Synthesis of poly(p-tetrahydrofuranyloxystyrene) 36 g of sulfuryl chloride and 1.5 Ω of tetrahydrofuran were mixed at room temperature, and 2-chlorotetrahydrofuran was dissolved in THF.
A solution was prepared. p-hydroxybenzaldehyde 20
The above 2-chlorotetrahydrofuran solution and the THF solution of 60 g of triethylamine were simultaneously added to the THF solution of 60 g of triethylamine. Furanyloxybenzaldehyde was obtained by removing the generated triethylamine hydrochloride and concentrating the solvent. T of 59 g of methyltriphenylphosphonium bromide and 39 g of p-butoxypotassium under nitrogen atmosphere.
The above THF solution of p-furanyloxybenzaldehyde was added to the HF solution. After 2 hours the product was poured into ice water and extracted three times with ethyl acetate. The crude product of p-tetrahydrofuranyloxystyrene was obtained by drying with magnesium sulfate and concentrating. This crude product was purified by column chromatography. 1 wt% azobisisobutyronitrile (AIBN) was added to a toluene solution of the monomer and heated to 80"C for 6 hours under a nitrogen atmosphere. After cooling, the polymer was precipitated in petroleum ether and dried in vacuo to give the indicated product. obtained the polymer,

[Reference Example 3] Synthesis of poly(p-vinylbenzoic acid tetrahydropyranyl ester) p-bromostyrene and metallic magnesium were reacted, and then carbon dioxide gas was blown into the reactor to synthesize p-vinylbenzoic acid. This carboxylic acid was esterified using 2,3-dihydropyran to obtain P-vinylbenzoic acid tetrahydropyranyl ester. Add AIBN to a toluene solution of monomers purified by distillation.
1 wt% was added and heated to 80° C. for 4 hours under a nitrogen atmosphere. After cooling, the polymer was precipitated in petroleum ether and dried in vacuo to give the title polymer.

[Reference Example 4] Synthesis of poly(p-vinylbenzoic acid tetrahydrofuranyl ester) To a THF solution of p-vinylbenzoic acid synthesized in the same manner as above, the above 2-chlorotetrahydrofuran solution and triethylamine solution in THF were added simultaneously. Ta. The generated triethylamine hydrochloride was removed and the solvent was concentrated to obtain p-vinylbenzoic acid tetrahydrofuranyl ester. 1 wt % of AXBN was added to a toluene solution of purified hepatoma obtained by distillation, and the mixture was heated at 80° C. for 4 hours under a nitrogen atmosphere. After cooling, the polymer was precipitated in petroleum ether and dried in vacuo to give the title polymer.

[Reference Example 5] Synthesis of poly(p-styrylacetic acid tetrahydropyranyl ester) p-vinylbenzyl nitrile synthesized from p-chloromethylstyrene and sodium cyanide was hydrolyzed by heating with an acid catalyst. I got it. This carboxylic acid was esterified using 2,3-dihydrobyran to obtain 4-styrylacetic acid tetrahydropyranyl ester. 1 wt % of AIBN was added to a toluene solution of the purified seven-year-old honey obtained by distillation, and the mixture was heated at 80'C for 6 hours under a nitrogen atmosphere. After cooling, the polymer was precipitated in petroleum ether and dried in vacuo to give the title polymer.

[Reference Example 6] Synthesis of poly(p-styrylacetic acid tetrahydrofuranyl ester) To a THF solution of p-styrylacetic acid synthesized in the same manner as above, the above 2-chlorotetrahydrofuran solution and triethylamine solution in THF were added simultaneously. The generated triethylamine hydrochloride was removed and the solvent was concentrated to obtain p-styrylacetic acid tetrahydrofuranyl ester. A toluene solution of purified monomer obtained by distillation
1 wt% of IBN was added, and the mixture was heated to 80° C. for 6 hours under a nitrogen atmosphere. After cooling, the polymer is precipitated in petroleum ether,
Drying in vacuo gave the title polymer. [Example 1] Poly(p-tetrahydropyranyloxystyrene) was dissolved in cyclohexanone to make a 20 wt% solution, and diphenyliodonium trifluoromethanesulfonate was added to this at 10 wt% based on the polymer solid content to prepare a resist. It was made into a solution. This resist solution was spin-coated onto a silicon wafer, and
A resist film having a thickness of 0.7 μm was formed by baking at 0° C. for 30 minutes. Light from a xenon-mercury lamp at 248n
3 mJ/aJ was exposed through a mask with a pattern through an interference filter for m. 10 at 100℃
After baking for a minute, it was developed for 60 seconds with an aqueous solution of 1 wt % tetramethylammonium hydroxide and 10 wt % n-propertool. A good 1 μm line-and-space positive type pattern could be formed. Similarly, when dichloromethane was used as a developer, a negative pattern was obtained.

[Example 2] Poly(p-tetrahydrofuranyloxystyrene) was dissolved in cyclohexanone to make a 20 wt% solution, and diphenyliodonium trifluoromethanesulfonate was added to this at 10 wt% based on the polymer solid content to prepare a resist solution. And so. This resist solution was spin-coated onto a silicon wafer, and
A resist film having a thickness of 0.7 μm was formed by baking at 0° C. for 30 minutes. Light from a xenon-mercury lamp at 248n
3 m J/al was exposed through a mask with a pattern through an interference filter for m. 10 at 100℃
After baking for a minute, it was developed for 60 seconds with an aqueous solution of 1 wt % tetramethylammonium hydroxide and 10 wt % n-propertool. A good 1 μm line-and-space positive type pattern could be formed. Furthermore, even when the polymer was changed from para-substituted to meta-substituted, the effect did not change.

[Example 3] Poly(p-tetrahydropyranyloxystyrene) was dissolved in cyclohexanone to make a 20 wt% solution, and bis-(p-t-butylphenyl)iodonium trifluoromethanesulfonate was added to this solution. A resist solution was prepared by adding 10 wt % to the solid content of the polymer. This resist solution was spin-coated onto a silicon wafer and heated at 80°C for 30 minutes.
A resist film having a thickness of 0.7 μm was formed by baking for a minute. B m
J/d exposure. After baking at 100°C for 10 minutes, 1wt% tetramethylammonium hydroxide and 10w
It was developed with an aqueous solution of t% n-propertool for 60 seconds, and a good 1 μm line-and-space positive type pattern could be formed. [Example 4] Exactly the same operation was carried out using diphenyliodonium trifluoroacetate instead of diphenyliodonium trifluoromethanesulfonate in Example 1, and 4 mJ/c
A good pattern of 1 μm was obtained by exposure to 1 μm. Similar results were also obtained using diphenyliodonium-p-toluenesulfonate.

[Example 5] A resist solution prepared as in Example 1 was spin-coated onto a silicon wafer, and the wafer was plated at 80° C. for 30 minutes to obtain a resist film with a thickness of 0.7 μm. Put this resist film into an electron beam lithography system at 20keV 20μC/a
Electron beam lithography was performed with a dose of il. 10 at 100℃
After beta for a minute. 1wt% tetramethylammonium hydroxide and 10wt%
Developed with an aqueous solution of n-propertool for 60 seconds to obtain a good zero
．． A 5 μm line-and-space positive pattern could be formed.

Example 6 A resist solution prepared as in Example 2 was spin-coated onto a silicon wafer and baked at 80° C. for 30 minutes to obtain a resist film with a thickness of 0.7 μm. Put this resist film into an electron beam lithography system at 20keV 15μC/a
Electron beam lithography was performed with a dose of J. After baking at 100° C. for 10 minutes, development was performed for 60 seconds with an aqueous solution of 1 wt % tetramethylammonium hydroxide and 10 wt % n-propertool, and a good line-and-space positive type pattern of 0.05 μm could be formed.

[Example 7] Poly(p-vinylbenzoic acid tetrahydropyranyl ester) was dissolved in cyclohexanone to make a 20 wt % solution, and diphenyliodonium trifluoromethanesulfonate was added to this solution at 10 wt % based on the polymer solid content.
% to form a resist solution. This resist solution was spin-coated onto a silicon wafer and baked at 80° C. for 30 minutes to form a resist film with a thickness of 0° and 8 μm. Light from a xenon-mercury lamp was passed through a 3QSnm interference filter and exposed to 5 mJ/d through a patterned mask. After baking at 100° C. for 10 minutes, development was performed for 60 seconds with an aqueous solution of 1 wt % tetramethylammonium hydroxide and 10 wt % n-propertool, and a good 1 μm line-and-space positive pattern could be formed.

Example 8 A resist solution prepared as in Example 7 was spin-coated onto a silicon wafer and baked at 80° C. for 30 minutes to obtain a resist film with a thickness of 0.8 μm. Put this resist film into an electron beam lithography system at 20keV 15μC/a
Electron beam lithography was performed with a dose of J. 10 at 1.00℃
After baking for a minute. 1, wt% tetramethylammonium hydroxide and 10
It was developed with an aqueous solution of wt% n-propertool for 60 seconds, and a good 0.5 μm line-and-space positive pattern could be formed. [Example 9] Poly(p-styrylacetic acid tetrahydropyranyl ester) was dissolved in cyclohexanone to give a 2Ow blind 1% solution, and triphenylsulfonium trifluoromethanesulfonate was added to this at a concentration of 10W based on the polymer solid content.
t% was added to prepare a resist solution. This resist solution was applied onto a silicon wafer in a rotating chamber and baked at 80° C. for 30 minutes to form a resist film with a thickness of 0° and 8 μm. xenon
Light from a mercury lamp was passed through a 308 nm interference filter and was emitted at 5 mJ/dll through a patterned mask. After baking at 100°C for 10 minutes, 10wt%n
- After rinsing with an aqueous solution of propatool, developing with a 1 wt% tetramethylammonium hydroxide aqueous solution for 60 seconds,
A good 1 μm line-and-space positive type pattern could be formed. L Example 10 Poly(P-styrylacetic acid tetrahydrofuranyl ester) was dissolved in cyclohexanone to make a 20 wt % solution, and triphenylsulfonium trifluoromethanesulfonate was added to this at a concentration of 10 wt % based on the polymer solid content.
% to form a resist solution. This resist solution was spin-coated onto a silicon wafer in the same manner as in Example 8, and an exposure experiment was performed.
A line-and-space positive pattern of μm could be formed. Furthermore, even when diphenyliodonium trifluoromethanesulfonate was used instead of triphenylsulfonium trifluoromethanesulfonate, almost the same results were obtained.

【Effect of the invention】

According to the present invention, it was possible to obtain a positive resist composition that has excellent sensitivity to ultraviolet rays, electron beams, X-rays, and other active radiation, and also has high resolution. Furthermore, by selecting a non-polar developer, it was also possible to form a negative pattern.

Claims (1)

[Scope of Claims] 1. A radiation-sensitive composition comprising a polymer containing an acetal group or a thioacetal group in its side chain and a compound that generates an acid upon irradiation with radiation. 2. A step of applying the radiation-sensitive composition according to claim 1 on a substrate to form a resist film, a pre-bake step to remove the coating solvent, a step of exposing the resist layer to a desired pattern, and a post-exposure bake. A pattern forming method comprising the steps of: developing with an alkaline developer to obtain a positive pattern. 3. A step of applying the radiation-sensitive composition according to claim 1 on a substrate to form a resist film, a pre-bake step to remove the coating solvent, a step of exposing the resist layer to a desired pattern, and a post-exposure bake. A pattern forming method comprising the steps of: developing with a non-polar solvent to obtain a negative pattern.