Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Electron beam imaging
Patent
1986-03-19
1987-10-13
Kittle, John E.
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Electron beam imaging
430281, 430312, 430326, 430330, 430942, 430967, G03C 500
Patent
active
046998705
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a patterning method for use in the manufacture of semiconductor integrated circuits, optical integrated circuits, Josephson devices and so forth.
BACKGROUND ART
With the improvement of the integration density and performance of semiconductor integrated circuits and so on, there has been a growing demand for a microfabrication technique for a semiconductor substrate or the like. In particular, for obtaining a predetermined pattern on a substrate or thin film of an insulator, a semiconductor or metal, a photoetching technique which removes an unnecessary part by an optical or chemical method is important and is now attracting attention as the microfabrication technique.
But, when imaging is performed through use of ultraviolet radiation for microfabrication in the order of submicrons, its wavelength is so long that it is impossible to prevent image lines from "defocusing" which is caused by the diffraction or reflection of light in a mask transfer process.
In the recent years, there has been developed, with a view to achieving ultra-microfabrication, an exposure system which utilizes an electron beam or soft X-rays of a shorter wavelength than the ultraviolet rays. The development of such an exposure system and improvement in a dry etching system which produces no appreciable undercut of a resist material together have made possible ultra-microfabrication in the order of submicrons.
The sensitivity of positive resist, which is a sort of resist, increases with an increase in the G-value used as a measure of the solubility of a main chain and an increase in the ratio between the solubility rates of irradiated and unirradiated parts of the resist during development, that is, an increase in the selective solubility of the resist itself.
Now, consider a benzene ring-containing polymer. This kind of resist is highly resistant to dry etching but since its G-value is small, it is difficult to achieve high sensitivity. It is considered, however, that if the abovesaid selective solubility could be enhanced by some method, a positive electron resist could be obtained which is excellent in the resistance to dry etching and high in sensitivity.
A cross-linking method has been known as one of techniques for improving the selective solubility. This method is one that coats straight-chain high molecules on a substrate and then heat treats the coating to create intermolecular cross-links, whereby the positive resist forms a resist film which is insoluble in a solvent. The positive resist of this kind, even after having been irradiated by an electron beam or X-rays, retains the cross-linking structure in the unirradiated part, so that even if a strong developing solvent is used, the unirradiated part will not undergo any swelling or deformation. With the strong developing solvent, since the irradiated part slightly decomposed by a very small amount of irradiation is also dissolved, high sensitivity can be achieved.
The known cross-linking type positive resist can be roughly divided into the following four kinds according to the type of thermal cross-linking reaction (the following reaction formulae being given noting only functionality groups of polymer side chains). 4,061,832) --(CH.sub.3).sub.3 or --CH.sub.2 CCl.sub.3. ) (See U.S. Pat. No. 4,264,715) K. Harada et al., "Poly(Phenyl Methacrylate-Co-Methacrylic Acid) as a Dry-Etching Durable Positive Electron Resist", IEEE Ed-29 (4) p518 (1982))
Usually these thermally cross-linkable functional groups are located in the same polymer molecules through copolymerization or in dissimilar polymer molecules through mixture of dissimilar polymers. However, since the thermal crosslink density varies with the content of such functional groups and the heat treatment temperature, their accurate control is needed for obtaining sensitivity of excellent reproducibility after development.
Especially, in the case where it is necessary, for the purpose of increasing the dry etching resistance of the resist, to mix therein a monomer unit cont
REFERENCES:
patent: 4024293 (1977-05-01), Hatzakis
patent: 4156745 (1979-05-01), Hatzakis et al.
patent: 4330614 (1982-05-01), Moyer et al.
Harada Katsuhiro
Iwadate Kazumi
Dees Jos,e G.
Kittle John E.
Nippon Telegraph and Telephone Corporation
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