JPH02150846A - Photosensitive composition and pattern forming method - Google Patents

Abstract

PURPOSE:To decrease the film thinning of a resist at the time of development and to obtain good patterns by forming the compsn. of an arom. azide compd., epoxy compd. and alkali soluble high-polymer compd. CONSTITUTION:This compsn. consists of the arom. azide compd., the epoxy compd. and the alkali soluble high-polymer compd. To be exact, the content of the azide compd. varies slightly with the sensitivity characteristics, optical characteristics, etc., of the compd. and is generally preferably in the range of about 1 to 40wt.% of the total weight. The concn. of the epoxy compd. may be in the entire range of 1 to 90wt.% of the total weight of the photosensitive compsn. with respect to the desired properties of the photosensitive compsn. The arom. azide compd. which is the photosensitive agent of the negative type photoresist is made into an amine compd. by exposing. The ring opening reaction of the epoxy compd. is induced by the amine compd. generated by this photochemical reaction, by which the epoxy compd. is sufficiently crosslinked in the resist. The film thinning of the resist at the time of the development is thus suppressed and the good exposing and developing characteristics are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a photosensitive composition and a pattern forming method, and particularly to a photosensitive composition and pattern forming method suitable for microfabrication. BACKGROUND OF THE INVENTION Photosensitive compositions are used in various applications such as semiconductor manufacturing processes. Semiconductor devices, especially LSI, VSL
In order to improve the performance of semiconductor devices such as I, it is necessary to improve the resolution (fineness) of their processing. Currently, g-line (436 nm) reduction exposure equipment is widely used for exposure. In order to improve the resolution, the NA (numerical aperture) of the reduction projection lens can be increased, and the
Efforts are being made to shorten the wavelength to 365 nm. It is technically difficult to increase the former NA without reducing the exposure area. Even if an exposure optical system with a high NA were created, the depth of focus would be shallow, making it impossible to use a simple process using a single-layer resist coating, which would cause practical problems. The latter shortening of the exposure wavelength is quite promising in practice. Of course, even if the wavelength is shortened, the requirements for resists such as high resolution will not change. Recently, exposure processes using KrF excimer lasers have been attracting attention in the short wavelength region. This is because the exposure wavelength of the KrF excimer laser is quite short at 248 nm, the output is large, and the oscillation is stable. for example,
Proceedings of the 47th Japan Society of Applied Physics Academic Conference, p. 323
, 29. a-ZF-2 (1986) using MP2400 (manufactured by Shipley Japan) as a positive photoresist and the results of KrF excimer laser exposure have been reported. Also, Proceedings of the 34th Applied Physics Association Lectures, Volume 2, p. 432.30a-N-8 (198
In 7), PMMA was used as a positive photoresist, and K
The results of rF excimer laser exposure have been reported. Problem 1 to be Solved by the Invention The above-mentioned conventional technology has a problem in that it cannot simultaneously satisfy both characteristics of high sensitivity and high resolution. In other words, MP2400 has a thickness of 1 μm and a wavelength of 2
The absorbance at 48 nm is 1.2, which is quite large for a positive type photoresist, and the incident light does not reach the bottom of the photoresist sufficiently.
There was a problem in that the cross-sectional shape of the pattern after exposure and development deteriorated considerably and became an inverted trapezoid. In addition, in the case of PMMA, the absorption is too weak, so its sensitivity is 32 J/cm.
”, which was a practical problem.In addition, PMM
When A is used on a silicon wafer, more than 80% of the incident light reaches the silicon wafer substrate, creating a large standing wave inside the lens 1-, making it difficult to resolve fine patterns. There was also the problem that it was not possible. Therefore, it is sufficient to develop a negative resist with lower absorption at 248 nm. However, in conventional negative resists, a large amount of photosensitizer is added so that the crosslinking reaction caused by light absorption of the photosensitizer can occur sufficiently. For this reason, the absorption of the resist at 248 nm is too strong.
After exposure and development, the pattern becomes an inverted trapezoid. 2
If the concentration of the photosensitizer used in the resist is reduced in order to lower the absorption at 48 nm, photocrosslinking due to exposure to light will be insufficient.
A problem arises in that the film on the lens 1 is greatly reduced during development, making it impossible to obtain a good pattern. The purpose of the present invention is to
The object of the present invention is to provide a photosensitive material having high sensitivity and resolution at 48 nm and a pattern forming method using the same. [Means for Solving the Problems 1] The photosensitive composition of the present invention is characterized by comprising an aromatic azide compound, an epoxy compound, and an alkali-soluble polymer compound. If the 248 nm absorption of the negative photolens 1- is too strong, the absorption of light on the surface of the coating film will be too strong and the pattern after development will be an inverted trapezoid, making it difficult to create vertical shapes or control the line width. The disadvantage is that it is difficult to do. If the concentration of the photosensitizer is lowered in order to reduce absorption, the photocrosslinking caused by exposure to light is insufficient, resulting in a large loss of resist film during development, resulting in the problem that a good pattern cannot be obtained. Therefore, we investigated resist materials and processes that do not cause film loss during development even when using a small amount of photosensitive agent. An aromatic azide compound, which is a photosensitizer for negative photoresists, becomes an amine compound upon exposure. The amine compound generated by this photochemical reaction causes a ring-opening reaction of the epoxy compound, resulting in sufficient crosslinking within the resist.
Film loss during resist development is suppressed, and good exposure and development characteristics can be obtained. The azide compound used in the present invention has an absorption band in the short wavelength exposure region. Of course, it may be a compound whose maximum absorption wavelength is on the longer wavelength side than the exposure wavelength. As such an azide compound, any known photosensitive compound may be used. For example, JP-A-56-162744, JP-A-5
There are azides described in the specification of No. 9-222833. The exact amount of the azide compound varies depending on the compound's sensitivity characteristics, optical properties, etc., but - numerically, the total amount (
The amount is preferably in the range of about 1 to 40% by weight based on the azide compound, epoxy compound, and polymer compound), and
More preferably, the content is in the range of about 30% by weight. Epoxy compounds that can be used in the present invention include glycidyl epoxides, aliphatic epoxides, epoxy cresol novolac resins, epoxy phenolic resins,
Polynuclear phenol-glycidyl ether derivatives and mixtures of these can also be used. 24 more
It is more preferable to use a material with low light absorption at 8 nm. The concentration of the epoxy compound of the present invention depends on the desired properties of the photosensitive composition, and the concentration of the epoxy compound of the present invention is determined based on the total amount of the photosensitive composition.
It can range from ~90% by weight, preferably from 10 to 50% by weight. Curing or photopolymerization with the epoxy compounds of the present invention is a triggered reaction. By exposure to radiation, an amine catalyst as a photopolymerization initiator is formed, and a curing reaction or a photopolymerization reaction proceeds and continues even after exposure. The use of thermal energy during or after exposure, ie, thermal boss curing, generally accelerates the curing reaction, and even mild increases in temperature may greatly accelerate the curing reaction. As the polymer compound of the present invention, a polymer compound used in general negative photoresists is used.
Particularly preferred are those that are alkali-soluble, and more preferably those that have dry etching resistance. Many of these polymer compounds have a benzene ring. Examples include condensation reaction products of phenols and formaldehyde such as cresol novolak resin, copolymers containing phenols, hydroxystyrene polymers, copolymers containing hydroxystyrene, and the like. [Function] In the present invention, the wavelength of the exposing light is made shorter than the generally used 436 nm, so the resolution is improved. For example, if the wavelength is 248 nm, the wavelength is 346 nm.
The minimum line width that can be resolved is 57% smaller than in the case of exposure. The absorbance at 248 nm of the 1 μm thick coating film of the present invention can be easily reduced to 1 or less. This is because the concentration of the photosensitizer can be lowered and the absorption of the epoxy compound is also small. For example, if the absorbance is 1 without using an epoxy compound,
When a photosensitive composition is prepared, the amount of photosensitizer is too small and sufficient crosslinking does not occur even after exposure. Therefore, film loss during development becomes large, making this method impractical. The photosensitive composition of the present invention does not have the problem of film thinning and has 24
The absorption of light at 8 nm can be easily controlled. Film thickness is 1μ
When the above-mentioned absorbance is 0.5 to 1.5 for a coating film of m, the cross-sectional shape of the coating film after exposure and development has its edges substantially perpendicular to the surface. If the absorbance is set to a value less than 0.5, for example 0.4, the cross-sectional shape of the coating film after exposure and development will have a gentle taber. On the other hand, if the value exceeds 1.5, for example 1.6, the cross-sectional shape of the coating film becomes an inverted trapezoid, which is not preferable. [Example 1] Hereinafter, the present invention will be explained in detail using an example. It should be noted that the following examples are for illustrating the present invention and are not intended to limit the scope of the present invention. Example 1 A photoresist solution having the following composition was prepared. Poly(4-hydroxystyrene), 3-(4'-azidostyryl)-5,5-dimethyl-2-cyclohexen-1-one, and hexanediol diglycidyl ether in a ratio of 64:6:
A photoresist solution was prepared by dissolving in cyclohexane in a weight ratio of 30. It was spin-coated onto a silicon wafer and baked at 80° C. for 10 minutes to form a coating film with a thickness of 1 μm. This film was
F excimer laser (Lambda physic = Lambda
(manufactured by Physik), and exposure was performed by changing the irradiation amount and irradiation position. The exposed coating film was developed for 60 seconds with a 0.952% aqueous solution of tetramethylammonium hydroxide. By this operation, the coating film in the unexposed areas was removed, and only the coating film insolubilized by exposure remained on the wafer. The film thickness after development was measured using a stylus-type film thickness meter (Alpha Step 200; Tenker Instruments; Ten, cor Instr.
The photosensitive characteristic curve of the photoresist was obtained by plotting the value against the exposure amount. As a result, the photosensitive composition of the present invention has a sensitivity (20 mJ/cm") that is sufficiently high for practical use and a contrast property (
2,0). In addition, the coating film produced in the same manner as above was exposed to KrF excimer laser light at a dose of 30 mJ/cm'' through a hard mask having a pattern width of 0.5 μm. Developed with a .952% aqueous solution for 60 seconds to obtain a good pattern with a width of 0.5 μm.Example 2 3-(4′-azidostyryl)-5 described in Example 1
, 3,3'-diazide diphenyl sulfone instead of 5-dimethyl-2-cyclohexen-1-one 63:
The method of Example 1 was repeated except that the weight ratio was 1:36. As a result, a good pattern with a width of 0.5 μm and a sensitivity of 80 mJ/cm” and a contrast of 1.5 was obtained. Example 3 The 3-(4'-azidostyryl)- described in Example 1 was obtained.
Using 3,3′-diazide diphenyl sulfone instead of 5,5-dimethyl-2-cyclohexen-1-one,
Additionally, the method of Example 1 was repeated except that butyl glycidyl ether was formulated in a weight ratio of 65:15:20 instead of hexanediol diglycidyl ether. As a result, a good pattern with a width of 0.5 μm and a sensitivity of 52 mJ/cm” and a contrast of 1.7 was obtained. Example 4 3-(4′-azidostyryl)- described in Example 1
Using 3,3′-diazide diphenyl sulfone instead of 5,5-dimethyl-2-cyclohexen-1-one,
Furthermore, in place of hexanediol diglycidyl ether, N,N'-diglycidyl-〇-toluidine 73:
The method of Example 1 was repeated except that the weight ratio was 12:15. As a result, a good pattern with a width of 0.5 μm was obtained with a sensitivity of 47 mJ/Cm'' and a contrast of 2.0. Example 5 3-(4'-azidostyryl)- described in Example 1.
Using 3,3′-diazide diphenyl sulfone instead of 5,5-dimethyl-2-cyclohexen-1-one,
Furthermore, in place of hexanediol diglycidyl ether, N,N'-diglycidylaniline was added at 73:12:15.
The method of Example 1 was repeated except that the weight ratio of As a result, a good pattern with a width of 0.5 μm and a sensitivity of 52 mJ/cm” and a contrast of 1.8 was obtained. Example 6 3-(4′-azidostyryl) described in Example 1 -5
, 5-dimethyl-2-cyclohexen-1-one, 3,3'-diazidiphenyl sulfone was used, and glycidyl ether of cresol novolak resin was used instead of hexanediol diglycidyl ether.
Example 1 except that the weight ratio was 24:11.
The method was repeated. As a result, a good pattern with a width of 0.5 μm was obtained with a sensitivity of 80 mJ/cm” and a contrast of 1.6. Example 7 After exposure using the process described in Example 1, the pattern was placed on a hot plate. de1
The method of Example 1 was repeated with the addition of a post-bake step for 11 minutes at 20°C. As a result, a good pattern with a sensitivity of 18 mJ/cm', a contrast of 1.9, and a width of 0.5 μm was obtained. (Effect of the invention 1) By using the photosensitive composition characterized by comprising an aromatic azide compound, an epoxy compound, and an alkali-soluble polymer compound of the present invention, film thinning of the coating film after exposure and development can be reduced. The cross-sectional shape of the formed pattern is substantially vertical.Also, since the photosensitive composition of the present invention is a negative type photoresist, it is possible to form a high-resolution pattern. This has the advantage that the amount of light that reaches the underlying substrate is small, and the influence of reflection from the substrate is small.

Claims (1)

[Scope of Claims] 1. A photosensitive composition comprising an aromatic azide compound, an epoxy compound, and an alkali-soluble polymer compound. 2. The epoxy compound is at least one selected from the group consisting of hexanediol diglycidyl ether, butyl glycidyl ether, N,N'-diglycidyl-o-toluidine, N,N-diglycidylaniline, and glycidyl ether of cresol novolak resin. 2. The photosensitive composition according to claim 1, which is a type of compound. 3. Either of claims 1 and 2, wherein the polymer compound is at least one type of polymer compound selected from the group consisting of a condensation reaction product of phenols and formaldehyde and a hydroxystyrene polymer. The photosensitive composition described in . 4. A step of applying a photosensitive composition containing an aromatic azide compound, an epoxy compound, and an alkali-soluble polymer compound onto a substrate to form a coating film, and a step of forming a predetermined pattern on the coating film. Characteristic pattern formation method. 5. The epoxy compound is at least one selected from the group consisting of hexanediol diglycidyl ether, butyl glycidyl ether, N,N'-diglycidyl-o-toluidine, N,N-diglycidylaniline, and glycidyl ether of cresol novolak resin. 5. The method for forming a pattern according to claim 4, wherein the compound is a type of compound. 6. Either of claims 4 and 5, wherein the polymer compound is at least one type of polymer compound selected from the group consisting of a condensation reaction product of phenols and formaldehyde and a hydroxystyrene polymer. The pattern forming method described in .