Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Patent
1988-12-20
1990-09-04
Dees, Jose
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
430296, 430325, 430967, G03C 516
Patent
active
049544241
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to pattern fabrication by radiation-induced graft copolymerization employed in the processing of semiconductor devices etc. and particularly to a resist having excellent dry etching durability.
BACKGROUND ART
In the processing of ULSI etc., studies on pattern fabrication by radiation-induced graft copolymerization using radiation, such as X-ray, are in progress. This pattern fabrication typically comprises an exposure step of irradiating a predetermined region of a resist layer formed on a wafer through coating with radiation, a graft copolymerization step of introducing a monomer to graft-copolymerize the resist layer with the monomer, a development step of eveloping the resist layer to fabricate a predetermined resist pattern, and an etching step of etching the surface of the wafer by making use of the resist pattern as a mask. The feature of the above-described pattern fabrication resides in that the resist can sufficiently be exposed even when the exposure dosage to the resist is small, i.e., an enhancement in the sensitivity of the resist can substantially be attained. This feature enables the pattern fabrication process to be expedited, which makes it possible to attain high throughput.
Conventional pattern fabrication by radiation-induced graft copolymerization is described in, for example, Japanese Pat. Laid-Open No. 137671/ 1978 (corresponding to U.S. Pat. No. 4195108). In this literature, an example wherein poly(methyl methacrylate) (PMMA) is used as a resist is described. This resist is widely employed as a model resist in the field of lithography.
However, the above-described PMMA resist has a drawback that when the surface of the substrate is dry-etched by making use of the fabricated resist pattern as the mask, the mask per se is etched, i.e., the dry etching resistance is low. Therefore, an improvement in the dry etching resistance of the resist has been desired in order to put pattern fabrication by radiation-induced graft copolymerization to practical use.
DISCLOSURE OF INVENTION
An object of the present invention is to provide pattern fabrication by radiation-induced graft copolymerization which enables an improvement in the dry etching resistance.
In order to attain the above-described object, the resist according to the present invention is made of a resist material capable of causing radiation-induced graft copolymerization and having excellent dry etching resistance, i.e., poly(methacrylate) containing a phenyl group, polystyrene or its derivatives.
As with polystyrene, poly(methacrylate) containing a phenyl group, such as poly(phenyl methacrylate) or poly(benzyl methacrylate), has excellent dry etching resistance, so that the current dry etching process can be employed as it is. Further, since these polymers generate radicals having a long life by irradiation, it is possible to conduct copolymerization with a monomer through graft copolymerization.
Therefore, the present invention enables not only the formation of a fine pattern of a resist in a very small exposure dosage but also excellent etching fabrication through the use of the current dry etching process, which greatly contributes to an improvement in the reliability.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1A to 1E are each a schematic flow diagram illustrating Example 1 according to the present invention;
FIGS. 2A to 2E are each a schematic flow diagram illustrating Example 2 according to the present invention; and
FIG. 3 is a graph showing the dry etching resistance of a typical resist.
BEST MODE FOR CARRYING OUT THE INVENTION
Example 1
FIGS. 1A to 1E are each a schematic flow diagram illustrating Example 1. A Si wafer 2 having a silicon oxide film 1 containing phosphor deposited on the whole surface thereof is coated with poly(phenyl methacrylate) (PPhMA) to form a resist 3 having a thickness of 1 .mu.m. The resist was exposed to an X-ray 10 in a nitrogen atmosphere containing air in an amount reduced to 1% or less through an X-ray mask 4 having a predetermined circu
REFERENCES:
patent: 4596761 (1986-06-01), Brault
Liu et al., "Polymethyl Methaesylate Resist Sensitivity Enhancement in X-Ray Lithegraphy . . . ", Appl. Phys. Lett., 44(10), May 15, 1984, pp. 973-975.
Harada, "Dry Etching Durability of Positive Electron Resist", J. Appl. Polymer Sci., vol. 26, 3395-3408, (1981).
Kimura Takeshi
Mochiji Kozo
Ogawa Taro
Oizumi Hiroaki
Soda Yasunari
Dees Jose
Hitachi , Ltd.
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