Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Removal of imaged layers
Reexamination Certificate
1998-10-30
2002-06-11
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Removal of imaged layers
C430S322000, C430S325000, C430S331000
Reexamination Certificate
active
06403289
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a developer for photosensitive polyimide resin compositions, and more particularly to a developer comprising an aqueous alkaline solution containing a basic compound. The developer according to the present invention is used in development after patterning exposure of a photosensitive layer formed from a photosensitive polyimide resin composition containing a polyamic acid.
BACKGROUND OF THE INVENTION
In a fabrication process of a semiconductor device, a photoresist is separated and removed from a substrate after its role has been filled in a step of etching or the like. However, such a photoresist film is left as a permanent film if it is used as a surface-protecting film or a layer insulation film. Therefore, it is required to have electrically and mechanically high characteristics or properties. Further, such a film also must resist a high temperature applied in the fabrication process of the semiconductor device.
In recent years, a film formed of a photosensitive polyimide resin composition has been used in such an application. The polyimide resin is excellent in electrical and mechanical characteristics, and heat resistance and is used as a surface-protecting film or layer insulation film for a semiconductor device, or the like. In order to selectively provide a film of a polyimide resin on minute parts of the semiconductor device, it is convenient to use a photosensitive polyimide resin composition containing a polyamic acid (i.e., a polyimide precursor). The photosensitive polyimide resin composition is coated on a substrate and dried to form a photosensitive layer. The photosensitive layer is then subjected to patterning exposure and developed to remove an unexposed portion thereof, thereby forming a pattern. The pattern thus formed is heat-treated as needed to cyclize the polyamic acid, thereby polyimidating it.
Examples of a developer heretofore used in a developing step of the photosensitive polyimide resin composition include developers obtained by adding a lower alcohol such as methanol, or water as a poor solvent to an aprotic polar solvent such as N-methyl-2-pyrrolidone (Japanese Patent Application Laid-Open Nos. 66940/1983 and 127738/1987) and developers obtained by adding an aromatic hydrocarbon such as xylene to an aprotic polar solvent such as N-methyl-2-pyrrolidone (Japanese Patent Application No. 255898/1990, corresponding with Japanese Patent Application Laid-Open No. 133062/1992”. The developers all comprise an organic solvent as a main component.
In recent years, it has been indicated that when an organic solvent is used as a developer, developer cost becomes high, explosion-proof apparatus are required, operator's health may be endangered, and natural environment is adversely affected. Therefore, attention is paid to polyamic acids and photosensitive polyimide resin compositions developable with an alkaline developer, particularly, a developer comprising an alkaline aqueous solution in place of the organic solvent.
As alkali-developed or alkaline aqueous solution-developed polyamic acids, there have hitherto been reported, for example, those obtained by introducing a protective group capable of leaving into a carboxyl group or a phenolic hydroxyl group under acid or alkaline conditions [J. Macromol. Sci. Chem., A24 (12) pages 1407-1422 (1987), Japanese Patent Application Laid-Open No. 259351/1989 and Japanese Patent Application Laid-Open No. 363361/1992]. However, these polyamic acids require to introduce a substituent group great in steric hindrance through a covalent bond into a main-chain carboxyl group or side-chain hydroxyl group. Therefore, they involve such problems that their synthetic processes become complicated, they require a high curing temperature, and film properties of films formed therefrom are deteriorated.
It has been proposed to incorporate a dihydropyridine derivative, which is a photo-induced base generator, and accelerate the imidation-facilitating effect of a base formed by exposure by PEB (post-exposure baking), thereby conducting development with an alkaline developer utilizing a difference in solubility caused by the imidation (Japanese Patent Application Laid-Open Nos. 5995/1993 and 281717/1993). However, these processes involve such problems that the PEB treatment is required, and the film formed has a low sensitivity to exposure, and so an exposure value must be made greater.
It has also been proposed to use a photosensitive resin composition obtained by adding a specific photopolymerizable monomer as a crosslinking auxiliary to a polyamic acid to conduct development with an alkaline developer or alkaline aqueous solution (Japanese Patent Application Laid-Open Nos. 183439/1988 and 100424/1993). In these processes, special polymerizable unsaturated compounds such as those having an isocyanate structure or a urethane structure are used as the photopolymerizable monomers. Since the polyamic acids used in these processes have no photopolymerizable group in their structures, there is a problem that sensitivity and resolution are insufficient.
It has been proposed to use an alkaline aqueous solution containing an amino-alcohol and another alkali than the amino-alcohol as a developer for photosensitive polyimide precursors (Japanese Patent Application Laid-Open No. 301217/1994). This publication discloses, for example, tetramethylammonium hydroxide, choline and sodium hydroxide as other alkalis than the amino-alcohol. A feature of the invention set forth in this publication is to provide a developer having a stronger basicity than that of a developer used for positive resists comprising a novolak resin as a resin component. It is said that when the use of this developer as a developer for a positive photosensitive polyimide precursor is advantageous to the control of developing speed and the formation of a minute pattern. However, this developer is too strong in dissolving power when a carboxyl group having salt-forming ability exists in a pattern-formed portion of the photosensitive polyimide precursor, so that swelling of the resin occurs at the pattern-formed portion, deterioration in resolution and the rate of residual film is caused, and consequently the impossibility of forming a pattern may be incurred in an extreme case.
It has been proposed to conduct development with an alkaline aqueous solution upon formation of a pattern using a photosensitive, heat-resistant polymer composition comprising a polyamic acid with a photosensitive group introduced into its recurring units, a sensitizer, and a sensitizing auxiliary (Japanese Patent Application Laid-Open No. 180505/1994). A wiring structure on which a surface-protecting film composed of a cured film of the photosensitive, heat-resistant polymer composition has been formed is produced by this process. When an alkaline aqueous solution containing tetramethylammonium hydroxide or the like, which is specifically disclosed in this publication, is used as a developer, however, it is difficult to fully prevent the swelling of a resin portion left as a pattern, so that resolution becomes insufficient, and moreover the strength of the resulting film is deteriorated.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a developer for photosensitive polyimide resin compositions, which scarcely swell a pattern-formed portion of a photosensitive polyimide resin composition upon development, has excellent resolution, causes no film separation upon development and scarcely affects film properties of a film obtained after curing.
The present inventors have carried out an extensive investigation with a view toward overcoming the above-described problems involved in the prior art. As a result, it has been found that when an alkaline aqueous solution containing a specific quaternary ammonium salt or quaternary phosphonium salt having a bulky substituent group as a basic compound (alkali) is used as a developer, the swelling of a resin portion left as a pattern is prevented, so that sensitivity and
Sakamoto Kei
Tanaka Akira
Yokouchi Kishio
Yoneda Yasuhiro
Barreca Nicole
Dinsmore & Shohl LLP
Huff Mark F.
Nippon Zeon Co. Ltd.
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