JPH0259751A - Photosensitive composition - Google Patents

Abstract

PURPOSE:To provide the photosensitive compsn. which is usable with a KrF excimer laser light source by constituting the compsn. of a specific polymer and photosensitive agent. CONSTITUTION:The photosensitive compsn. is constituted of the polymer having the basic structural unit expressed by formula I and the photosensitive agent. The polymer expressed by formula I is obtd. by alternate copolymn. of the compd. expressed by formula II and SO2. In formula I, R1 to R4 respectively denote hydrogen or 1 to 6C, more preferably 1 to 3 residual hydrocarbon group; (n) denotes 0 or 1 to 3 integer. In formula II, R1 to R4 respectively denote hydrogen or 1 to 6C residual hydrocarbon group; (n) denotes 0 or 1 to 3 integer. The use of the photosensitive compsn. with the KrF excimer laser light source is enabled in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photosensitive composition suitable for manufacturing semiconductor devices such as LSIs. More specifically, the present invention relates to a photosensitive composition suitable as a resist material for photolithography for manufacturing semiconductor devices using deep ultraviolet light as a light source.

[Prior Art] Semiconductor elements such as LSIs have been becoming increasingly finer in recent years, and the minimum line width of circuits has entered the submicron (1 μm or less) region. Along with this, the requirements for photolithography are becoming stricter year by year, with line widths of half a micron (0.
A light source (
(exposure equipment) and resists are now in demand.

The light source that has been used so far in photolithography is g.
line (wavelength 438r+m), but it is impossible to achieve half a micron with this g-line, and it is necessary to use far-ultraviolet light with a shorter wavelength as a light source. KrF excimer laser light with a wavelength of 248 r+m is used as a far-ultraviolet light source, and exposure apparatuses using this have already been developed.

[Problems to be Solved by the Invention] However, resist materials for light sources with sufficient performance have not yet been developed. Among the resists developed so far, positive resists in which a quinone diazide compound as a photosensitive component is added to a novolac type phenol resin (hereinafter abbreviated as novolac resin) have been evaluated as relatively excellent. However, with this type of resist,
The reality is that even if a short wavelength light source that can achieve high resolution is used, it is not possible to draw a high resolution pattern. The main reason for the low resolution of resists whose main component is novolac resin is 248nm due to novolac resin.
It is known that the light absorption is too strong, or in other words, the 2480 m light transmittance of novolak resin is very low.

Novolac resin is often used as the main component (binder resin) of resist materials because this resin is: ■ Soluble in alkaline aqueous solution; ■ Resistance to plasma etching by CF4 gas, etc. (plasma resistance and the following) This is because it has the following two characteristics: high 248r+m light transmittance (abbreviated), and is excellent as a binder resin except for the low 248r+m light transmittance.

However, there is a strong demand in the semiconductor industry for a resin that satisfies the above two points as a binder resin for a resist and, at the same time, (1) has a high transmittance for 248 nm light. This is because if such a resin is used as a binder resin, it will become a resist material that can form a pattern with high resolution in photolithography using KrF excimer laser light as a light source.

However, a resin that satisfies all of ■, ■, and ■ is not yet known. The resins that have been developed so far that satisfy (■) are all aromatic polymers, including novolac resins, so the 248rv caused by the aromatic ring
Light absorption becomes inevitable, and the 248 nm light transmittance becomes low.

There is a strong demand for the development of a resist using a resin as a binder that satisfies all of the above (1), (2), and (2), that is, a photosensitive composition that can be used with a KrF excimer laser light source.

[Means for Solving the Problems] The present invention solves the above problems and provides a photosensitive composition that can be used in a KrF excimer laser light source. More specifically, the present invention provides a novel high-performance resist material consisting of a binder resin and a photosensitizer that is 1) soluble in aqueous alkaline solutions, 2) has high plasma resistance, and 2) has high 248rv light transmittance.

That is, the present invention relates to a photosensitive composition comprising a polymer having a basic structural unit represented by the following general formula [I] and a photosensitizer.

[R+, R2, R3 and R4 each represent hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, n
represents 0 or an integer from 1 to 3. The polymer represented by the general formula [I] of the present invention can be obtained by alternating copolymerization of the compound represented by the following general formula [A] and S02.

[R+, R2, R'3 and R4 each represent hydrogen or a hydrocarbon residue having 1 to G carbon atoms, and n is 0 or 1 to 3
represents an integer of ] The compound represented by formula [A] can be synthesized by various methods. For example, it can be synthesized by a Diels-Alder reaction between a compound represented by the general formula [Al1] and a compound represented by the general formula [A2].

[R,, R2, R3 and R4 each represent hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, and n represents 0 or an integer of 1 to 3 [A+] Compound Examples include cyclopentadiene, methylcyclopentadiene, ethylcyclopentadiene, butylcyclopentadiene, dimethylcyclopentadiene, diethylcyclopentadiene, and the like. Among these, compounds that can be preferably used include cyclopentadiene, methylcyclopentadiene,
Dimethylcyclopentadiene may be mentioned. A particularly preferred compound is cyclopentadiene. A composition comprising one or more of these compounds can be used to synthesize the compound represented by the general formula [A].

Examples of the compound represented by [A2] include acrylic acid, crotonic acid, methacrylic acid, vinyl acetic acid, propylidene acetic acid, tiglic acid, and allyl acetic acid. Among these, compounds that can be preferably used include acrylic acid, methacrylic acid, and vinyl acetic acid. A particularly preferred compound is acrylic acid. A composition comprising one or more of these compounds can be used to synthesize the compound represented by the general formula [A].

Copolymerization of the compound represented by the general formula [A] and S02 is carried out using a radical catalyst as a catalyst, and at a temperature of -100°C to
It is carried out at 100°C, preferably -50°C to 0°C.

Examples of radical polymerization catalysts include t-butyl hydroperoxide, cumene hydroperoxide, and di-t-butyl hydroperoxide.
Examples include organic peroxides such as butyl peroxide and t-butylcumyl peroxide, and azo compounds such as azobisisobutyronitrile and azobis-2,4-dimethylvaleronitrile.

Polymerization is carried out using cyclohexanone, chloroform,
This can be carried out in the presence of an organic solvent such as methyl ethyl ketone.

Further, a compound represented by the general formula [B] can also be allowed to coexist in the polymerization system as a monomer.

The compound represented by the general formula [B] can be synthesized by various methods. For example, it can be synthesized by a Diels-Alder reaction between a compound represented by the general formula [A+1] and a compound represented by the general formula [B2].

[R+, R2, R3 and R4 each represent hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, and R5 represents hydrogen or an organic residue having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms. represents a residue] When a compound represented by the formula [B] is used, a polymer in which a structural unit represented by the following general formula [13] is partially inserted into the molecular skeleton is obtained.

1-<4 +5 R, R4 [Compounds represented by B11 include, for example, ethylene,
Propylene, 1-butene, 2-butene, ■-pentene,
2-pentene, 3-pentene, methyl vinyl ether,
Examples include methyl acrylate, ethyl acrylate, hexyl acrylate, methyl methacrylate, ethyl methacrylate, and hexyl methacrylate. Among these, compounds that can be preferably used include ethylene, propylene,
Examples include methyl acrylate and methyl methacrylate. Particularly preferably used compounds include ethylene and methyl acrylate.

A composite acid consisting of one or more of these compounds can be used to synthesize the compound represented by the general formula [B].

The compound represented by the general formula [B] can be used insofar as it does not impair the solubility of the resulting polymer in an alkaline aqueous solution. The compound [B] can be used in a molar ratio of 0 to 300%, preferably 0 to 100%, and more preferably 0 to 40% relative to the compound represented by the general formula [A].

These polymers belong to the so-called polysulfone class, and the above-mentioned polymers can also be synthesized by other methods known for synthesizing polysulfones, such as oxidation of polysulfides.

The number average molecular weight of these polymers is not particularly limited, but is usually 10,000 to 1,000,000, preferably 20,000 to 300,000.

As the photosensitizer used in the present invention, compounds conventionally used as photosensitizers for resist materials for lithography can be used, regardless of whether they are positive type or negative type.

Among these photosensitizers, positive-type quinonediazide compounds and negative-type azide compounds can be mentioned as photosensitizers that can be preferably used.

Examples of the quinonediazide compound include 1,2-benzoquinonediazide-4-sulfonic acid phenyl ester, 1.2
-Benzoquinonediazide-4-(N-ethyl-N-β-
)-sulfonamide, 1,2-naphthoquinonediazide-
5-sulfonic acid cyclohexyl ester, L-(1,2
-naphthoquinonediazide-5-sulfonyl) -3,5
-dimethylpyrazole, N,N-di(1,2-naphthoquinonediazide-5-sulfonyl)-aniline, 2-(naphthoquinonediazide-5-sulfonyloxy)-1-hydroxy-anthraquinone, 1,2-naphthoquinonediazide-5- Sulfonic acid 2,4-dihydroxybenzophenone ester, 1,2-naphthoquinonediazide-5-sulfonic acid 2,3.4-) dihydroxybenzophenone ester, 2 moles of 1,2-naphthoquinonediazide-5-sulfonic acid chloride and 4.4 'Diaminobenzophenone 1 mol condensate, 1,2-naphthoquinone diazide-
Condensation product of 2 moles of 5-sulfonic acid chloride and 1 mole of 4.4'-dihydroxy-1,1'-diphenylsulfone, condensation product of 1 mole of 1.2-naphthoquinone diazido-5-sulfonic acid chloride and 1 mole of purpurogalin. Can list things. A composition comprising one or more of these quinonediazide compounds can be used as the photosensitizer of the present invention.

Examples of the azide compounds include 4-azidobenzalacetophenone, 4-azidobenzal-4'-methylacetophenone, 4-azidobenzal-4'-methoxyacetophenone, 4,4'-diazidobenzalacetophenone,
4-Azidobenzophenone, 2.6-di(4'-azidobenzal)cyclohexanone, 2.6-di(4'-azidobenzal)4-methylcyclohexanone, 4.4'
Examples include -diazido diphenyl sulfone, 3,3'-diazido diphenyl sulfone, 4,4'-diazido diphenyl ether, 4,4'-diazido diphenyl sulfide, and 4,4'-diazido diphenylmethane. A composition comprising one or more of these azide compounds can be used as the photosensitizer of the present invention.

In the present invention, the amount of the photosensitive agent used is 0.5 to 100 parts by weight per 100 parts by weight of the polymer used in the present invention.
Preferably 1 part of 3 to 70ffiE, more preferably 5
It can be used in a range of 40 parts by weight.

If the amount is less than 0.5 parts by weight, the photosensitive composition will not exhibit sufficient photosensitivity. Moreover, if the amount is more than 100 parts by weight, the film-forming properties of the photosensitive composition will be reduced.

When using the photosensitive composition of the present invention, a film of the photosensitive composition of the present invention is formed on a substrate such as a silicon wafer with a film thickness of 0.1 to 10 microns, and then a film of 248 nm is passed through a mask. Irradiates with far ultraviolet light such as light. Formation of this film can be carried out by dissolving the photosensitive composition of the present invention in an organic solvent, applying the solution onto a substrate using a spin coating machine, and further preheating this as necessary. I can do it. Examples of organic solvents that can be used in this case include methyl cellosolve, ethyl cellosolve, ethylene glycol, diethylene glycol, and ethyl carbitol. When the photosensitive composition of the present invention is made into a solution of these organic solvents, its concentration is 1 to 50 w.
t%, preferably 3 to 30vt%, more preferably 5
It can be used in the range of ~25 wt%.

A pattern can be formed from the composition of the present invention by irradiating it with deep ultraviolet light through a mask and then developing it with an alkaline aqueous solution. Examples of aqueous alkaline solutions include aqueous solutions of sodium hydroxide, potassium hydroxide, sodium carbonate, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and the like. Among these, a preferred developer is an aqueous solution of tetramethylammonium hydroxide.

[Effect of the invention] As mentioned above, the photosensitive composition of the present invention is characterized by the above-mentioned (1).

It consists of a polymer having a basic structural unit represented by the general formula [I] satisfying all of the conditions (1) and (2) and a photosensitizer. By using the photosensitive composition of the present invention, a resist pattern with higher resolution than conventional resist materials can be formed.

[Example 7] The present invention will be specifically explained below using Examples, but the present invention is not limited thereto.

Synthesis Example 1 Cyclopentadiene and an equimolar amount of acrylic acid were reacted in an autoclave at 170° C. for 1 hour to obtain a compound [al] which is a Diels-Alder reaction product.

Compound [a] 113.8g (0.10 mol) and 5O
270i was charged into an autoclave equipped with a stirrer and having an internal volume of 300 d, which was purged with nitrogen, and then the internal temperature was lowered to -30°C using a low temperature bath. To this was added 0.05 d of t-butyl hydroperoxide, and the mixture was allowed to react for 1 hour while keeping the internal temperature at -30° C. without stirring. After the reaction is completed, 100II is added to the system.
dl of methyl cellosolve was added and mixed with the reaction mixture, and the mixture was warmed to room temperature. 2000 d of this methyl cellosolve solution
When added dropwise into ether, a fine white precipitate was formed. After washing this precipitate with ether, it was vacuum dried at 60° C. for 8 hours, and 8.5 g of white powder was recovered. elemental analysis,
This powder was found to be a compound [al] by IR analysis, NMR analysis, etc.
It was confirmed that it was an alternating copolymer of 1 and S02. Gelvermutation chromatography (GPC)
), the number average molecular weight was 64,000 based on polystyrene.

Synthesis Example 2 Cyclopentadiene and an equimolar amount of ethylene were reacted in an autoclave at 170° C. for 1 hour to obtain compound [b] which is a Diels-Alder reaction product.

(0,080 mol) and compound [b] 11.9 g (
0,020 mol) and 270 trdl of 5O were charged into a nitrogen-purged autoclave with an internal volume of 300 d and equipped with a stirrer, and then the internal temperature was lowered to -30°C using a low temperature bath.

To this was added 0.05 d of t-butyl hydroperoxide, and the mixture was allowed to react for 1 hour while keeping the internal temperature at -30° C. without stirring. After the reaction was completed, 100 ml of methyl cellosolve was added to the system and mixed with the reactants, and the temperature was raised to room temperature.

When this methyl cellosolve solution was dropped into 2000 d of ether, a fine white precipitate was formed. After washing this precipitate with ether, it was vacuum dried at 60°C for 7 hours.9.
1 g of white powder was collected. Elemental analysis, IR analysis, NM
According to R analysis, etc., this powder is an alternating copolymer of compound [al or [b] and S02, and Ca] and [b].
It was confirmed that the polymer was steadily introduced into the polymer during preparation. When the molecular weight was measured using GPC, the number average molecular weight was 67,000 based on polystyrene.

Compound synthesized in the above Synthesis Example 1 [al 11.0g Phenol 11.4gS m-Cresol 2B, 1g, 3
28.5 g of 7% formaldehyde aqueous solution, 0.61 g of oxalic acid dihydrate, 3.8 g of ion-exchanged water, and 12.0 g of ethyl cellosolve acetate were placed in a 300 InIl separable flask, and heated and stirred in an oil bath at 110°C for 3 hours. Made it react. After adding 24.0 g of ethyl cellosolve acetate and reacting for an additional 3 hours, the mixture was neutralized, washed with water, and dehydrated to obtain a solution of novolac resin in ethyl cellosolve acetate. When molecular weight is measured by GPC,
The weight average molecular weight was 12,900.

Comparative Synthesis Example 2 39.6 g of m-cresol/p-cresol τ-60/40 (mole ratio) mixed cresol, 27.0 g of 37% formaldehyde aqueous solution, 0.61 g of oxalic acid dihydrate, 3. [ig, ethyl cellosolve acetate 1
Pour 2.0g into a 300-inch separable flask,
The reaction mixture was heated and stirred in a 10°C oil bath for 3 hours.

After adding 24.0 g of ethyl cellosolve acetate and reacting for further 3 hours, the mixture was neutralized, washed with water, and dehydrated to obtain a solution of novolac resin in ethyl cellosolve acetate.

When the molecular weight was measured by GPC, the weight average molecular weight was 15,000.
It was 00.

Measurement of wave film physical properties> The polymers of Synthesis Example 1 and Synthesis Example 2, which are the polymers constituting the photosensitive composition of the present invention, were prepared by preparing an ethyl cellosolve solution, applying it using a spin coating machine, and then heating and drying it. A film with a thickness of 1 micron was formed on each synthetic quartz plate.

Further, from the ethyl cellosolve acetate-1 solution of the polymer obtained in Comparative Synthesis Example 1 and Comparative Synthesis Example 2, a film having a thickness of 1 micron was formed on a synthetic quartz glass plate in the same manner.

The 248 nm light transmittance of the above coating was measured using a spectrophotometer.

Further, using a reactive ion etching (RIE) device, the etching rate was measured at a gas composition of CF 4 /02-95/5 (voJ ratio). The results are shown in Table 1.

The polymers of Synthesis Examples 1 and 2 have a very high 248 nm light transmittance compared to the novolac resins of Comparative Synthesis Examples 1 and 2, and the Kr
It can be seen that this resin is very suitable as a binder resin for resist materials for lithography using far ultraviolet light such as F excimer laser light as a light source.

It can also be seen that the polymers of Synthesis Examples 1 and 2 have excellent RIE etching resistance, which is almost equivalent to that of the novolak resin.

Table 1 Physical properties of coating film and performance evaluation as a positive resist>
2: 1.0 (mole ratio) condensation reaction product was used as a photosensitizer, and the photosensitizer was added to the polymers of the above Synthesis Examples 1 and 2 and Comparative Synthesis Examples 1 and 2 at a weight ratio of polymer/photosensitizer -80/20. was added to evaluate the performance as a positive resist.

The coating solvent used was ethyl cellosolve for the polymers in Synthesis Examples 1 and 2, and ethyl cellosolve acetate for the polymers in Comparative Synthesis Examples 1 and 2, and the solid content concentration was adjusted to 20 wt%. After applying this onto a silicon wafer using a spin coating machine,
A resist film having a thickness of 1 micron was formed by heating at 00° C. for 20 molecules.

A KrF excimer laser device manufactured by Hamamatsu Photonics was used as the light source for exposure.

Developed with tetramethylammonium hydroxide 2.38
It was carried out with a νt% aqueous solution at 20° C. for 3 minutes, and rinsed with water for 1 minute.

A sensitivity characteristic curve was created to determine the sensitivity and γ value (resolution standard: the larger the better). In addition, lines and spaces of 0.5 micron were drawn by contact exposure using a mask manufactured by Dai Nippon Printing ■, and the angle θ between the side wall of the resist pattern and the silicon wafer of the substrate was measured (0°, θ<90°).
). The closer θ is to 90°, the more vertical the sidewalls and the higher the resolution.

The results are shown in Table 2.

It can be seen that both the γ value and the angle θ of the composition of the present invention are higher than those using a conventional novolak resin as a binder. This shows that the photosensitive composition of the present invention has high resolution. It can be seen that the sensitivity is almost the same as that of novolak resin type, and that it has high sensitivity.

Table 2 Performance as a positive resist and performance evaluation as a negative resist> 2. Synthesis Examples 1 to 2 and Comparative Synthesis Example 1 using 6-di(4'-azidobenzal)-4-methylcyclohexanone as a photosensitizer ~2 polymer, polymer/photosensitizer-9
The photosensitive agent was added at a weight ratio of 0/10 and the performance as a negative resist was evaluated.

Developed with tetramethylammonium hydroxide 0.85
% aqueous solution. Other experimental conditions were the same as those for the positive resist. The results are shown in Table 3.

Both the γ value and the angle θ of the composition of the present invention are higher than those using a conventional novolak resin as a binder. This shows that the photosensitive composition of the present invention has high resolution.

In addition, the sensitivity is almost the same as that of novolak resin type,
It can be seen that it has very high sensitivity.

Table 3 Performance as a negative resist substrate

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. A photosensitive composition comprising a polymer having a basic structural unit represented by the following general formula [I] and a photosensitizer. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] [R_1, R_2, R_3 and R_4 each represent hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms, and n is 0 or 1.
~3 represents an integer]