Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
1998-02-12
2001-04-10
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S905000, C430S907000, C430S910000
Reexamination Certificate
active
06214517
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive type photoresist composition suitable for exposure treatment with active light rays or radiation, particularly light rays having a wavelength as very short as 170 nm to 220 nm, and more particularly to a positive type photoresist composition high in sensitivity, and giving an excellent resist pattern and a pattern excellent in adhesion to a substrate.
Further, the present invention relates to an ultramicro-lithography process or another photofabrication process for producing a very large scale integrated circuit or a high capacity microchip, and more particularly to a positive type photoresist composition which can form a highly refined pattern by use of far ultraviolet rays including excimer laser beams.
BACKGROUND OF THE INVENTION
In recent years, there have been glowing demands in the field of production of various electronic devices requiring fine processing such as semiconductor elements towards the devices progressively increased in density and integration. This makes very severe the required performances for the photography techniques for realizing refined patterns. Contributing to this refining technique are photoresists increased in resolution and exposure light having a shortened wavelength.
In general, the resolution (Res) of the optical system can be represented by the Rayleigh equation, namely Res=k·&lgr;/NA (wherein k is a process factor, &lgr; is a wavelength of an exposure light source, and NA is the number of openings of a lens). This equation shows that the width of a reproduced line can be decreased to resolve a fine pattern (namely high resolution can be obtained) by shortening the wavelength at the time of exposure. Surely, the exposure wavelength has been sifted to the g-line (436 nm) and the i-line (365 nm) of a high pressure mercury lamp with a decrease in the minimum width of the reproduced line, and the production of the devices by use of the KrF excimer laser beam (249 nm) has been studied. For further fine processing, the use of an excimer laser beam having a shorter wavelength, particularly ArF (193 nm), has a good prospect.
Looking at photoresists exposed to shortwave light, high integration in multilayer resist systems utilizing surface lithography, not in monolayer resist systems which have previously been used in the industrial production, is also studied. However, it still suffers from the problem of complicated processes which have prevented the practical application of the multilayer resists.
In the case of excimer lasers including KrF excimer lasers, it is generally considered that the life of gases is short, and that the cost performance of the lasers is required to be improved because exposure devices themselves are expensive.
Responding to this are so-called chemical amplification type resists becoming the main current in KrF excimer laser exposure applications. In the chemical amplification type resists, acids are generated from photo acid generators existing in catalytic amounts in the systems by exposure, and protective groups of alkali-soluble groups of binders or low molecular weight compounds are eliminated with the catalytic amount of acids by the catalytic reaction to ensure discrimination of the solubility in alkali developing solutions. In the chemical amplification type resists, the acids generated by the photocatalytic reaction are catalytically utilized, so that an increase in sensitivity is expected.
In general, the chemical amplification system resists can be roughly divided into three classes, commonly called as a 2-component system, a 2.5-component system and a 3-component system. In the 2-component system, a photo acid generator is combined with a binder resin. The binder resin is a resin having a group which is decomposed by the action of an acid to enhance the solubility of the resin in an alkali developing solution (which is also referred to as an acid decomposable group) in its molecule. The 2.5-component system contains a low molecular weight compound further having an acid decomposable group in addition to such a 2-component system. The 3-component system contains the photo acid generator, the alkali-soluble resin and the above-mentioned low molecular weight compound.
However, when the wavelength of exposure light becomes short, a new problem is encountered. That is, in the photoresists, raw materials good in transparency to shortwave light is poor in resistance to dry etching. On the other hand, there is the problem that raw materials good in resistance to dry etching is poor in transparency. The compatibility of the resistance to dry etching and the transparency is basically the problem of the performance of the binder resins contained in photoresist layers.
The binder resins include novolak resins and poly(p-hydroxystyrene). The novolak resins are widely utilized as alkali-soluble resins for i-line resists, and the poly(p-hydroxystyrene) resins are used as base polymers for KrF excimer laser resists. These produce no problem as long as long-wave light is used. However, different therefrom, the use of shortwave light rises a problem. In particular, the above-mentioned resins have high optical density within the wavelength region of 170 nm to 220 nm. It is therefore actually difficult to directly use these resins as with the conventional methods. Accordingly, the development of resins high in light transparency and resistance to dry etching has been looked forward to.
One of the general solutions to this problem is a method of introducing, for example, an alicyclic hydrocarbon moiety into the resin. There is also a method of utilizing a naphthalene skeleton, one of the aromatic compounds. In particular, various reports disclose that the introduction of alicyclic hydrocarbon moieties fulfills demands for both light transparency and resistance to dry etching. For example, it is described in
Journal of Photopolymer Science and Technology,
3, 439 (1992).
On the other hand, what to select as the acid decomposable group contained in the resin is important, particularly, because it affects the sensitivity and resolution of the resist and further the aging stability.
The acid decomposable groups for protecting carboxylic acid groups, which have hitherto been mainly reported, include tertiary alkyl esters such as t-butyl esters and acetal esters such as tetrahydropyranyl esters and ethoxyethyl esters. However, the t-butyl ester groups have the drawback that the ability of being eliminated with the generated acids is low, resulting in a lowering of the sensitivity. Conversely, the tetrahydropyranyl esters and the ethoxyethyl esters have a large problem with the aging stability because of their easy decomposition at ordinary temperatures.
Further, JP-A-5-346668 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) has proposed to use 3-oxocyclohexyl ester groups as the acid decomposable groups. However, they are not necessarily satisfactory in sensitivity.
As described above, for the acid decomposable groups for protecting the carboxylic acids which satisfy the sensitivity and the aging stability of the photoresists at the same time, how to design the acid decomposable groups has been not necessarily clear.
Furthermore, in order to decrease the width of the reproduced line to resolve the fine pattern in the resulting resist pattern, not only the above-mentioned characteristics but also sufficient adhesion of the fine pattern obtained to a substrate is required. Even if the fine pattern is obtained, insufficient adhesion thereof sometimes causes separation thereof.
On the other hand, in photofabrication processes of lithography, the production of semiconductors for ICs and the production of circuit substrates for thermal heads, semiconductor wafer, glass, ceramic or metal substrates are coated with photoresists to a thickness of 0.5 &mgr;m to 2.5 &mgr;m by spin coating or roller coating, followed by heating and drying. Then, circuit patterns are printed thereon through exposure masks with active light such as u
Aoai Toshiaki
Sato Kenichiro
Chu John S.
Fuji Photo Film Co. , Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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