JPH03113448A - Resist composition - Google Patents

Abstract

PURPOSE:To form a thick fine negative type resist pattern having a satisfactory cross-sectional shape and high accuracy by incorporating an org. polymer and a specified sensitizer. CONSTITUTION:An org. polymer and a sulfoxide compd. represented by formula I or II as a sensitizer are incorporated. In the formulae I, II, each of R1 and R2 is a monovalent org. group, R1 and R2 may be different from each other, they may partially bond to each other to form an S-contg. cyclic compd., the double bond (=) of O is practically equivalent to the coordinate bond ( ) and this expression is adopted because S=O bond has the property of coordinate bond. A thick fine pattern having a satisfactory cross-sectional shape can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a resist composition useful for forming fine resist patterns.

(Prior Art) Resists are widely used in fine pattern formation processes including the manufacture of semiconductor devices such as LSIs. In particular, in order to achieve higher densities in response to the increasing functionality and sophistication of electronic devices, proposals have been made to miniaturize resist patterns, shorten the wavelength of light used for exposure, and form patterns using ionizing radiation. As resist compositions suitable for such pattern formation, several diazo resist compositions (Japanese Unexamined Patent Publication No. 1933/1983) have been proposed.

However, when a resist film formed by applying and drying the resist composition is exposed to light, the light absorption is large, and as the film becomes thicker, it becomes difficult for the radiation to reach the bottom of the resist film, resulting in poor cross-sectional shape (pattern accuracy). becomes worse.

As a result, there was a problem in that it was not possible to form a resist pattern that could be used as a mask in a dry etching process.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and provides a resist composition that has a thick film thickness, a good cross-sectional shape, and is suitable for forming fine patterns. This is what we are trying to provide.

[Constitution of the Invention (Means for Solving the Problems) The present invention provides a resist characterized by containing an organic polymer and a photosensitizer consisting of a sulfoxide compound represented by the following general formula (I) or CU). Composition.

(I) However, RI and R2 in formulas (I) and (II) may be the same or different and represent a monovalent organic group. Also, R, R2
may be partially combined to form a cyclic compound containing an S atom. Here, regarding the bonding state of the oxygen atom, double (=) and coordinate bond (→) are substantially equivalent, and this expression can be made because the S-0 bond has coordinate bonding property. I'm being told.

The above-mentioned organic polymer may basically be any polymer compound that can form a thin film and does not decompose significantly upon irradiation with radiation. For example, radiation-crosslinked polyacrylate resin and/or its copolymer with polyacrylic acids, polystyrene, halogenated polystyrene, poly(vinylbenzyl chloride), polyester resin, polyether resin, polyimide resin, polyvinylphenol resin, phenol. Examples include novolak resins, polyamide resins, and the like. Among these, alkali-soluble resins suitable for alkaline development are preferred, and in particular, polyvinylphenol resins and novolak resins prepared by condensing phenol, cresol, xyresol, butylphenol, halogenated phenol, etc. with aldehyde compounds are most preferred.

Such phenolic resin has a molecular weight of 3000 to 2000.
A softening point of at least 100'C or higher is preferable from the viewpoint of heat resistance. Further, when short wavelength ultraviolet rays are used as the exposure light source, it is desirable to use a thin film with a thickness of 1 μm formed of the phenol resin alone and having a transmittance of at least 25% at the exposure wavelength.

Photosensitizers made of sulfoxide compounds represented by the above general formulas (I) and (II) can be used for light such as ultraviolet rays, electron beams,
It is sensitive to ionizing radiation such as X-rays. General formula (I
), R1R2 introduced into (II) is, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cyclo Alkyl group, or halogenated alkyl group in which some of these hydrogen atoms are substituted with halogen, cyclohalogenated alkyl group, phenyl group, phenyl group in which alkyl or halogen alkyl is substituted, halogenated phenyl group, hydroxy-substituted Examples thereof include a phenyl group substituted with a phenyl group, a phenyl group substituted with an amino group, a benzyl group substituted with a halogen, a hydroxy group, a nitro group, or a benzyl group substituted with an amino group. Further, R1 and R2 may be partially combined to form a cyclic compound containing an S atom, and specific examples include cyclic compounds having the structural formula shown in Table 1 below. Basically, the higher the content of a photosensitive agent made of such a sulfoxide compound in a resist composition, the higher the resolution, but on the contrary, the sensitivity, coating properties, and film forming properties deteriorate. It is desirable that the solid content is in the range of 0.5 to 5096%, more preferably 5 to 30% of the total solid content of the composition.

The sulfoxide compounds represented by the above general formulas (I) and (n) are synthesized by oxidation of a sulfide compound having -8- in its structure. In addition to the generally well-known oxidation method using hydrogen peroxide,
For example, New Experimental Chemistry Course (I4), [Maruzen J p, 41B
Oxidation with N-halocarboxylic acid amides is preferred as described in .

The resist composition according to the present invention is prepared by dissolving one or more of the organic polymer and the photosensitizer in a solvent. Suitable examples of such solvents include cellosolve solvents such as ethyl cellosolve and butyl cellosolve, cellosolve acetate solvents such as ethyl cellulosolve acetate and butyl cellosolve acetate, ketone solvents such as cyclohexanone and methyl ethyl ketone, and ester solvents such as butyl acetate. be. However, these solvents may contain trace amounts of xylene, toluene, dimethylformamide, N-methylpyrrolidone, dioxane, etc., or may contain trace amounts of surfactants.

In addition to the organic polymer, photosensitizer, and solvent, the resist composition according to the present invention may optionally contain a sensitizer such as benzophenone, biphenyl, triphenyl, fluorene, benzaldehyde, and xanthone, and a sensitizer for storage stability. thermal polymerization inhibitor, an antihalation agent to prevent halation from the substrate, an adhesion promoter to improve adhesion to the substrate, or another polymer to modify the coating film (e.g. propylene oxide). - ethylene oxide copolymer, silicone rubber), etc. may be blended.

Next, a pattern forming process using the resist composition of the present invention will be explained.

First, a resist composition prepared by dissolving the organic polymer and photosensitizer in a solvent is applied onto a substrate by spin coating or dipping, and then dried at a temperature of 150°C or less, preferably 70 to 120°C to form a resist film. form. Examples of the substrate used here include a silicon single crystal wafer, a silicon wafer whose surface is coated with various films such as an insulating film and a conductive film, a blank mask, and a compound semiconductor wafer such as GaAs and InP. can.

Next, the resist film is exposed. When this exposure light source is light, the wavelength of ultraviolet rays, excimer laser light (KrF, ArF), etc. using a high and low pressure mercury lamp as the light source is 300 nm.
m or less is used. Furthermore, when the exposure light source is ionizing radiation, electron beams, X-rays, vacuum ultraviolet rays, etc. are used. Such light or ionizing radiation may be monochromatic light or a mixture of light with multiple wavelengths, but monochromatic light usually produces standing waves due to interference between incident light and reflected light, reducing resolution. There is a tendency to In order to reduce such standing waves, it is desirable to perform a baking process after exposure.

Next, the exposed resist film is developed using a predetermined developer to form a desired resist pattern. For example, when the organic polymer blended in the resist composition is an alkali-soluble resin such as a phenolic resin, the developer used is an aqueous solution of tetramethylammonium hydroxide, an aqueous solution of choline, or the like.

(Function) -5O-(sulfoxide) introduced into the photosensitizers represented by general formulas (I) and (II) used in the present invention is resistant to ionizing radiation such as light with a wavelength of 8 (I0ni or less) and electron beams. The organic polymer is decomposed by irradiation with light or ionizing radiation and acts as a so-called negative type, exhibiting a solvent suppressing effect within the organic polymer blended with the photosensitizer.Moreover, the resist containing the photosensitizer The composition does not cause a strong increase in absorbance (coloration).Therefore, the resist film obtained by coating and drying such a resist composition is irradiated with ionizing radiation such as light with a wavelength of 300nrII or less or an electron beam (exposure). ) Then, the irradiated area becomes in a solvent-suppressed state due to the decomposition of the photosensitizer, and its excellent transparency allows light and ionizing radiation to reach the bottom of the resist even with a film thickness of about 1 μm.As a result, the development process after exposure A negative resist pattern with high precision and good cross-sectional shape can be formed.
Furthermore, it is sufficiently durable to be used as a mask in a dry etching process, and provides effects such as being able to accurately etch the base of a substrate or the like.

(Example) Examples of the present invention will be described in detail below.

Example 1 First, 1 l of commercially available (Aldrich) diphenyl sulfoxide [sensitizer A] was added to a novolac resin obtained by condensing p-cresol and metacresol with formaldehyde.
OW t 96: After blending and dissolving with ethyl cellosol rubber acetate in an amount 2.5 times the weight of the solid content, the resist composition was prepared by filtration. Subsequently, this resist composition was applied onto a silicon wafer to form a resist film with a thickness of 1 μm, and then an electron beam was applied to the resist film at an accelerating voltage of 20 μm.
Sensitivity was investigated by irradiating under kV conditions. As a result, Do,
5 (exposure amount that gives a residual film rate of 0.5) and 10 μC/cm2
The sensitivity as a negative resist was obtained.

For this reason, after drawing a line-and-space pattern on the resist film by scanning an electron beam with a beam diameter of 0.2 μm under the condition of 20 μC/cm2,
．． The film was developed for 4 minutes with a TMA H aqueous solution having a concentration of 38%. As a result, it was possible to resolve up to a line and space pattern of 0.3 μm.

Examples 2 to 6 Five types of resist compositions were prepared by dissolving the organic polymers and photosensitizers shown in Table 2 below in 2.5 times the weight of the solid content of ethyl cellosol rubber acetate. Example 1
Similarly, D. , and the resolution of resist patterns formed under the exposure and development conditions shown in Table 2 were investigated. The results are also listed in Table 2. In addition, the second
The results of Example 1 are also listed in the table.

Example 7 A resist film having a thickness of 1 μm was formed by coating on a silicon wafer having the same composition as in Example 1, and then the sensitivity was examined by irradiating the resist film with excimer laser light of 0.248 μm. As a result, a sensitivity of 100 mJ/cm 2 was obtained at Do,s (exposure amount at which the residual film rate was 0.5) as a negative resist.

For this reason, the resist film has a thickness of 0.248 μm.
After performing line and space pattern exposure by selectively irradiating excimer laser light, the film was developed with a TMA H aqueous solution having a concentration of 2.38% for 4 minutes. As a result, it was possible to resolve up to a line and space pattern of 0.3 μm.

Examples 8 to 12 Five types of resist compositions were prepared by dissolving the organic polymers and photosensitizers shown in Table 2 below in 2.5 times the weight of the solid content of ethyl cellosol rubber acetate. Example 7
Similarly, the resist sensitivity at D o, , and the resolution of resist patterns formed under the exposure and development conditions shown in Table 2 were investigated. The results are also listed in Table 2. Note that the results of Example 7 are also listed in Table 2.

As is clear from Table 2 above, the resist composition of the present invention has good sensitivity to electron beams and excimer laser light, and can form fine negative resist patterns with high resolution.

[Effects of the Invention] As detailed above, the resist composition of the present invention forms a negative resist pattern that is thick, has a good cross-sectional shape, is fine, and has high precision, and can also be used as a mask in the dry etching process. It is durable enough to be used as an etchant, and has effects such as being able to precisely etch the base of a substrate or the like.

Claims (1)

[Scope of Claims] A resist composition comprising an organic polymer and a photosensitizer represented by the following general formula (I) or (II). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) However, R_1 and R_2 in formulas (I) and (II) may be the same or different, and 1 Indicates a valent organic group. Also, R_1
, R_2 may be partially combined to form a cyclic compound containing an S atom.