JPH03223860A - Novel resist material - Google Patents

Abstract

PURPOSE:To obtain a resist material having transmittance and heat resistance higher than those before exposure to the i-line rays and high sensitivity by using a heat-resistant resin composed of constituents each having a functional group chemically changeable and solubilizable in alkali by heating under an atmosphere containing an acid and constituents for imparting heat resistance to the resin. CONSTITUTION:The heat-resistant resin 2 to be used is composed of the constituents each having the functional group chemically changeable and solubilizable in alkali by heating under an atmosphere containing an acid generated from an acid generator by exposure and the constituents each suppressing softening of the resin itself against heating. The constituent having the functional group is embodied by the monomer unit of a p-hydroxystyrene derivative having a protective group releasable by the acid, and the like, and the resin 2 is embodied by the copolymer of p-isopropoxystyrene and alpha-methylstyrene, and the like, thus permitting the obtained resist material to be high in sensitivity and enhanced in transmittance and heat resistance by exposure to the i-line rays and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resist material used in manufacturing semiconductor devices and the like. For details, see 400 yen as an exposure energy source.
nn or less light source, e.g. 365nn 1-line light, 300n
The present invention relates to a resist material for forming a positive pattern using deep ultraviolet light of n or less, for example, 248.4nr+ KrF excimer laser light.

[Prior Art] In recent years, with the high density integration of semiconductor devices, the light source of exposure equipment used for machine box processing, especially photolithography, has become increasingly shorter in wavelength, and now KrF excimer laser (
248.4 nm) light is now being considered. However, a resist material suitable for this wavelength has not yet been found.

For example, MP2400 (
(manufactured by Sibley), the pattern shape after development is very poor and cannot be used due to the large surface absorption of the novolac resin itself as a base polymer to the exposure light and the poor photoreactivity of the naphthoquinone diazide compound as a photosensitizer. do not have.

In addition, resist materials have been developed that use KrF excimer laser light or far ultraviolet light as a light source. (
For example, JP-A-64-80944; JP-A-1-1
A pattern forming material made of photosensitive compound No. 54048 and a resin having high light transmittance around 248.4 nm has also been developed. (For example, JP-A No. 1-188852
; Y, Tan1 et al., 5PIE's 1989 Sy
mpo, 1086-03, etc.). A pattern forming method using this resist material will be described using FIG. A resist material 5 is spin-coated onto the semiconductor substrate 1 to obtain a 1.0 μm resist material film (FIG. 4(a)). Note that an oxide film, a conductive film, and an insulating film are often formed on the substrate 1. Next, 248.4nn KrE' excimer laser light 3
Then, selective exposure is performed through the mask 4 (FIG. 4(b)).

Finally, development is performed using an ordinary alkaline developer (0.24% tetramethylammonium hydroxide aqueous solution) to dissolve and remove the exposed areas of the resist material 5, thereby obtaining a pattern 5a (FIG. 4(C)). . The ultraviolet ray spectral curve of this resist material film (1 μL) after exposure is shown in FIG. While the resin used is 70% at 1μ0 thickness,
The transmittance of this resist material after exposure was as low as 40%, indicating that sufficient light chromaticity was not obtained. Additionally, as a result of pattern formation experiments, the aspect ratio of the pattern was approximately 7.
A sufficient pattern shape of 0 degree was not obtained. Furthermore, when using a resist material containing a photosensitive compound having a film base of this resist material, the sensitivity for boat fishing is 100 to 30.
KrF excimer laser light (248,4 nm
) is currently difficult to put into practical use. Also, in recent years,
As a means to reduce the amount of exposure energy, a chemically amplified resist material using acid generated by exposure as a medium has been proposed [H. Ito et al., Polym, Eng, Sci.
23, p. 1012 (1983)], and various reports have been made regarding this. (For example, W, R, Brun
svold et al., 5PIE'51989 Sympo.
1086-40; T, Neenan et al., 5PIE'
s 1989Sympo, 1086-01) However, due to the fact that the resins used in these chemically amplified resist materials have a relatively large number of aromatic rings,
There are problems such as insufficient light transmittance around 8.4 nm and poor heat resistance of the resin.

Therefore, it is difficult to obtain a good pattern shape, and a large amount of exposure energy is required. In addition, for chemically amplified resist materials, 248-4 nm of resin
It cannot be used unless the light transmittance in the vicinity is improved or the heat resistance of the resin is improved.

Therefore, there is a current need for a resist material that has even higher transmittance after exposure to KrF excimer laser light or i-line light, has heat resistance, and has high sensitivity.

[Object of the Invention] The present invention was made in view of the above-mentioned situation, and has high transparency after exposure to i-line light, far ultraviolet light, such as KrF excimer laser light, etc., and has heat resistance. Another object of the present invention is to provide a resist material with high sensitivity (low exposure energy amount).

[Configuration of the Invention] In order to achieve the above object, the present invention consists of the following configuration.

``A heat-resistant resin consisting of a component that has a functional group that undergoes a chemical change when heated in an acid atmosphere and becomes alkali-soluble, and a component that imparts heat resistance to the resin, and a photosensitive compound that generates an acid when exposed to light. and a solvent capable of dissolving both of them.'' The resist material of the present invention utilizes chemical amplification in order to reduce the amount of exposure energy as much as possible. That is, the resist material of the present invention contains a component having a functional group that undergoes a chemical change upon heating in an acid atmosphere generated from an acid generator upon exposure and becomes alkali-soluble, and a component that imparts heat resistance to the resin, i.e., a component that imparts heat resistance to the resin. In contrast, this is a novel resist material characterized by the use of a heat-resistant resin (hereinafter abbreviated as "resin according to the present invention") composed of a component that has the function of suppressing the softening of the entire resin. . A component having a functional group that becomes alkali-soluble by heating in an acidic atmosphere according to the present invention (hereinafter referred to as "component having a specific functional group")
It is abbreviated as ), for example, P-hydroxystyrene derivatives having a protecting group that can be removed with acid, P-hydroxy-
Examples include α-methylstyrene derivatives and the like.

Specific examples include ρ-methoxystyrene, P-isopropoxystyrene, p-tert-butoxystyrene, P-methoxymethoxystyrene, P-isopropoxymethoxystyrene, P-tetrahydropyranyloxystyrene, P-tetrahydrofuranyloxystyrene. , p
-Trimethylsilyloxystyrene, p-tert-butoxycarbonyloxystyrene, P-impropoxycarbonyloxystyrene, or ρ-hydroxy-α-methylstyrene derivatives having the same protecting group as these P-hydroxystyrene derivatives. However, it is of course not limited to these.

In addition, as a component that imparts heat resistance to the resin, any component that can prevent the entire resin from softening even when heated to 100°C or higher, more preferably 140°C or higher can be used as the component that imparts heat resistance to the resin. Good though.

For example, p-hydroxystyrene, p-chlorostyrene,
Styrene, α-methylstyrene, fumaronitrile, monoisopropyl maleate, mono-tert-butyl maleate, di-tert-butyl maleate, monocyclohexyl maleate, maleic anhydride, N-phenylmaleimide, N-substituted phenylmaleimide, N- More common monomers include methylmaleimide and N-n-butylmaleimide.

The resin according to the present invention has the following general formula [I] or [II].
] You can have hail.

[wherein R1 is a methyl group, isopropyl group, tertiary butyl group, methoxymethyl group, isopropoxymethyl group, tetrahydropyranyl group, tetrahydrofuranyl group,
Represents a trimethylsilyl group, a mere-butoxycarbonyl group or an isopropoxycarbonyl group, R2 represents a hydrogen atom, a halogen atom or a methyl group, R3 represents a hydrogen atom, P-hydroxyphenyl M, P-chlorophenyl group, phenyl group, cyanide group or -COOR7 (however,
R7 is a branched or cyclic alkyl group having 3 to 10 carbon atoms,
Or represents a hydrogen atom. ), R4 and R6 each independently represent a hydrogen atom, a methyl group, or a halogen atom, and R5 is a hydrogen atom, a cyano group, or -COOR8 (however, R8 is a branched or cyclic alkyl group having 3 to 10 carbon atoms) , or a hydrogen atom), R9 is a hydrogen atom or -〇〇OR'0 (However, Rlo is a carbon number of 3 to 10
represents a branched or cyclic alkyl group, or a hydrogen atom. ), and k and 1 each independently represent a natural number. Ko [in the ceremony.

X is an oxygen atom or]N (CH2)(]-R (where q represents O or a natural number, and R1+ is a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms or a substituent) ), 1' and P each independently represent O or a natural number, R1, R2
, R3, RA, R5, R6, R9 and k are the same as above. These compounds represented by the general formula [I] or [I[] are examples of the resin according to the present invention, but the resin according to the present invention is of course not limited to these compounds. .

Specific examples of the resin according to the present invention include p-isopropoxystyrene and α-methylstyrene copolymer, P-isopropoxystyrene and α-methylstyrene copolymer,
Tetrahydropyranyloxystyrene and p-hydroxystyrene copolymer, p-tert-butoxystyrene and P-hydroxystyrene copolymer, p-tert-butoxycarbonyloxystyrene and maleic acid monocyclohexyl ester copolymer, p-tert -Butoxycarbonyloxystyrene and α-methylstyrene copolymer, p-tert-butoxystyrene and fumaronitrile copolymer, P-methoxymethoxystyrene and P-chlorostyrene copolymer, P-methoxymethoxystyrene and monocyclohexyl maleate Copolymer of ester and maleic anhydride, P-tetrahydrofuranyloxystyrene and N-methylmaleimide copolymer, p-tert-butoxycarbonyloxystyrene and P-hydroxystyrene and maleic anhydride copolymer, P - Copolymer of tetrahydropyranyloxystyrene, p-hydroxystyrene and fumaronitrile, copolymer of p-tert-butoxycarbonyloxystyrene, P-hydroxystyrene and N-butylyareimide, P-tetrahydropyranyloxystyrene and Examples include, but are not limited to, copolymers of P-hydroxystyrene and N-phenylmaleimide.

The resin according to the present invention comprises a component having the above-mentioned specific functional group (
It can be easily obtained by copolymerizing one or more monomers and one or more monomers imparting heat resistance to the resin according to a conventional method for producing copolymers. That is, one or more components (monomers) having the above-mentioned specific functional groups and one or more components (monomers) that impart heat resistance to the resin are combined with radicals in an organic solvent such as benzene or toluene. Polymerization initiator [e.g. azobisisobutyronitrile 2,2'-azobis(2,
4-dimethylvaleronitrile), 2,2'-azobis(
Polymerization in a nitrogen stream at 50 to 100°C for 1 to 10 hours in the presence of an azo polymerization initiator such as (methyl 2-methylpropionate) or a peroxide polymerization initiator such as benzoyl peroxide, lauroyl peroxide, etc. It is sufficient to carry out the reaction, and after the reaction, post-treatment may be carried out according to a conventional method for obtaining a polymer compound, and the product may be isolated.

The resin according to the present invention can also be used as a commercially available PO! It goes without saying that it can also be easily obtained by appropriately introducing the specific functional group into a polymer such as , I (P-vinylphenol) through a chemical reaction.

The weight average molecular ffi (Mw) of the resin according to the present invention is usually about t,ooo to 40,000, preferably 3
, Cl00 to about 20,000.

Specific examples of the photosensitive compound that generates an acid upon exposure to light used in the present invention include P-)luenesulfonic acid 2,
6-cinitrobenzyl, 2,6-dinitrobenzyl trichloroacetate, 2-nitrobenzyl p-)luenesulfonate, 2-nitrobenzyl trichloroacetate, 2,4-dinitrobenzyl trifluorobenzenesulfonate, diphenyl-P-methyl Examples include, but are not limited to, phenacylsulfonium verchlorate, diphenyl-2,5-dimethoxyphenacylsulfonium P-)luenesulfonate, diphenyl phenacylsulfonium trifluoromethanesulfonate, and the like.

The solvent used in the present invention may be any solvent as long as it can dissolve both the resin and the photosensitive compound, but it is usually more preferable to use a solvent that does not have absorption in the vicinity of 365 nm and 248.4 nm. . More specific examples include ethyl cellosolve acetate, methyl cellosolve acetate, diethylene glycol dimethyl ether, ethyl lactate, methyl lactate, dioxane, and ethylene glycol monoisopropyl ether, but are not limited thereto.

The heat-resistant resin of the present invention does not absorb light in a wavelength region of 300 nm or more, and has extremely high light transmittance to J-line light of 365 nm. It has also been confirmed that acid generators generate acids even with i-line light, and chemical amplification can be used. Therefore, the resist material of the present invention uses a chemical amplification method to produce a low exposure dose of KrF excimer laser light (248
, 4 nm) or J-line light (365 nm).

[Function] To explain the action of the present invention using a specific example, a portion exposed to KrF excimer laser light, J-ray light, etc. generates acid according to the photoreaction shown in (A) or (B) below, for example.

Following the margin 2N 2N exposure step, heat treatment causes the functional groups of the resin to undergo a chemical change with the acid according to the reaction formula (C) below, becoming alkali-soluble and eluting into the developer during development.

On the other hand, since no acid is generated in the unexposed area, no chemical change occurs even after heat treatment, and no alkali-soluble groups are expressed. Furthermore, since the resin itself has high heat resistance, no softening of the resin is observed during heat treatment. When a pattern is formed using the resist material of the present invention in this way, a large difference in solubility in an alkaline developer occurs between the exposed and unexposed areas.
Moreover, since the resin in the unexposed areas does not soften during the heat treatment, a positive pattern with good contrast is formed. Further, as shown in the reaction formula (C), since the acid generated by exposure acts catalytically, exposure only needs to generate the necessary acid, making it possible to reduce the amount of exposure energy.

[Example] The present invention will be explained in more detail with reference to Examples and Reference Examples below, but the present invention is not limited by these in any way.

Reference Example 1 88 g of p-tert-butoxystyrene and 39 g of fumaronitrile were mixed in a toluene solvent under a nitrogen stream in the presence of 2,2'-azobis(methyl 2-methylpropionate),
A polymerization reaction was carried out at 90°C for 2 hours. After the reaction, the reaction solution was poured into methanol to cause crystallization, and the precipitated product was collected by filtration and dried to obtain 120 g of p-tert-butoxystyrene-fumaronitrile copolymer (h about 10,000).

Example 1゜ A resist material having the following composition was prepared.

P-crt-butoxystyrene-fumaronitrile copolymer (■ approx. 10,000) 2,6-cinitrobenzyl trichloroM acid 0.3g diethylene glycol dimethyl ether 13.7g Pattern using the above resist material using Fig. 1 The formation method will be explained. The resist material 2 was spin-coated onto a substrate 1 such as a semiconductor, and after soft baking on a hot plate at 90° C. for 90 seconds, a resist material film with a thickness of 1.0 μm was obtained (first
Figure (a)). Next, 248.4 nm (7) KR F excimer laser light 3 was selectively exposed through a mask 4 (
Figure 1(b)). After baking on a hot plate at 130°C for 90 seconds, developing with an alkaline developer (2.38% tetramethylammonium hydroxide aqueous solution) for 60 seconds dissolves and removes only the exposed areas of resist material 2, forming a positive pattern. 2a was obtained (Fig. 1(C)). FIG. 2 shows the ultraviolet ray spectral curves of this resist material film (1 μm) before and after exposure. The transmittance before and after exposure hardly changes, and even after exposure it shows a high transmittance of about 65%. Further, the positive pattern at this time had a well-shaped 0.3 μm line-and-space pattern with an aspect ratio of about 87 degrees. Furthermore, the γ characteristics of this resist material film (1 μm) are shown in FIG. This material has a minimum exposure tt 10mJ/c
It had a high sensitivity of m2.

Example 2 A resist material having the following composition was prepared, and the same experiment as in Example 1 was conducted.

p-Tetrahydropyranyloxystyrene-P-hydroxystyrene copolymer (Mw about 12,000) diethylene glycol dimethyl ether 13.7 g The results show that good results similar to those in Example 1 were obtained using this resist material. The positive pattern obtained using this method had an I'iT ability for pattern formation at this exposure energy amount of about 18 mJ/an.

Example 3゜P-methoxymethoxystyrene maleic acid copolymer (shoulder approximately 15,000) (k/
i/p22/l/1)
6.0g diphenyl-2,5-dimethoxyphenacylsulfonium P-)luenesulfonate 0.
3g Shiniko Rengelicol Dimethyl Ether 13.7.
g An experiment similar to Example 1 was conducted using a resist material prepared with the above composition.

As a result, good results similar to those of Example 1 were obtained. The positive pattern obtained using this resist material is approximately 20 m long.
Pattern formation was possible with an exposure energy amount of J/an2.

Example 4 p-tert-butoxystyrene-P-hydroxystyrene copolymer (Mw about 8,000)
2.6-cinitrobenzyl p-toluenesulfonate 0.3g diethylene glycol dimethyl ether 1.3.1g An experiment similar to Example 1 was conducted using a resist material prepared with the above composition.

As a result, good results similar to those in Example 1 were obtained. The positive pattern obtained using this resist material is approximately 24 m long.
Pattern formation was possible with an exposure energy amount of J/an2.

Example 5゜Using a resist material prepared with the composition shown in Example 4,
The same experiment as in Example 1 was conducted using 365 nm i-line light instead of 248.4 nm KrF excimer laser light as the light source.

As a result, good results similar to those of Example 1 were obtained. The positive pattern obtained using this resist material is approximately 25 m long.
Pattern formation was possible with an exposure energy amount of J/an''.

[Effects of the Invention] The resist material according to the present invention can be used with a light source of 400 nm or less, such as 365 nm J-line light, or far ultraviolet light (D) of 300 nm or less.
eepUV) - for example, KrF excimer laser light (248
When used as a resist material for exposure such as 4 nm), fine patterns with good shapes on the order of submicrons can be easily obtained. Therefore, the present invention has great value for the formation of ultra-fine patterns in the semiconductor industry and the like.

This resist material is particularly effective with one-line light, deep ultraviolet light, and KrF excimer laser light, but it can also be used satisfactorily with electron beams and X-rays.

[Brief explanation of drawings]

Figures 1 to 3 show the results obtained in Example 1;
The figure is a process cross-sectional view of a pattern forming method using the resist material of the present invention.
The figures show γ characteristic diagrams of the resist materials of the present invention. Fig. 4 is a process cross-sectional view of a pattern forming method using a conventional resist material, Fig. 5 is an ultraviolet ray spectral curve diagram of a conventional resist material (the solid line is before exposure, the broken line is after exposure), and Fig.
The figure is a γ characteristic diagram of a conventional resist material. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Resist material film of the present invention, 3.
- KrF excimer laser light, 4... mask, 5...
- Conventional resist material film, 2a...resin pattern. Patent applicant Wako Pure Chemical Industries, Ltd.

Claims (3)

[Claims] (1) A heat-resistant resin composed of a component that has a functional group that undergoes a chemical change when heated in an acid atmosphere and becomes alkali-soluble, and a component that imparts heat resistance to the resin, and a photosensitive resin that generates acid when exposed to light. A resist material comprising a compound and a solvent capable of dissolving both. (2) A heat-resistant resin composed of a component having a functional group that undergoes a chemical change upon heating in an acid atmosphere and becomes alkali-soluble, and a component that imparts heat resistance to the resin has the following general formula [
I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼[I] [In the formula, R^1 is a methyl group, isopropyl group, tert
- represents a butyl group, methoxymethyl group, isopropoxymethyl group, tetrahydropyranyl group, tetrahydrofuranyl group, trimethylsilyl group, tert-butoxycarbonyl group or isopropoxycarbonyl group, and R^2 is a hydrogen atom, a halogen atom or a methyl group represents R^3
is a hydrogen atom, p-hydroxyphenyl group, p-chlorophenyl group, phenyl group, cyano group or -COOR^7(
However, R^7 represents a branched or cyclic alkyl group having 3 to 10 carbon atoms, or a hydrogen atom. ), R^4 and R^6 each independently represent a hydrogen atom, a methyl group, or a halogen atom, and R^5 represents a hydrogen atom, a cyano group, or a -C
OOR^8 (however, R^8 represents a branched or cyclic alkyl group having 3 to 10 carbon atoms, or a hydrogen atom), and R^9 represents a hydrogen atom or -COOR^1^0 (however,
R^1^0 represents a branched or cyclic alkyl group having 3 to 10 carbon atoms, or a hydrogen atom. ), and k and l each independently represent a natural number. ] The resist material according to claim (1), which is a resin represented by: (3) A heat-resistant resin composed of a component having a functional group that undergoes a chemical change upon heating in an acid atmosphere and becomes alkali-soluble and a component that imparts heat resistance to the resin has the following general formula [
II] ▲There are mathematical formulas, chemical formulas, tables, etc.▼[II] [In the formula, X is an oxygen atom or N-(CH_2)q-R^1
^1 (However, q represents 0 or a natural number, and R^1^1 represents a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms or a phenyl group which may have a substituent. .)
, l' and p each independently represent 0 or a natural number, R^1, R^2, R^3, R^4, R^5, R^
6, R^9 and k are the same as above. ] The resist material according to claim (1), which is a resin represented by: