Radiation imagery chemistry: process – composition – or product th – Registration or layout process other than color proofing
Patent
1994-02-24
1995-12-19
Rosasco, S.
Radiation imagery chemistry: process, composition, or product th
Registration or layout process other than color proofing
430312, 430394, 430397, 355 53, 355 67, 355 68, G03F 900
Patent
active
054767369
ABSTRACT:
A projection exposure method in which a mask pattern containing both an isolated geometrical shape and closely arranged geometrical shapes can be improved in depth of focus. A central part in cross section of a beam of light is darkened prior to illumination of a mask. The beam of light thus darkened is projected to a photoresist film formed on a substrate through the mask and an optical projection system to carry out a first exposure. Next, at least one of the photoresist film and the optical projection system is relatively moved along an optical axis of the optical projection system, and then, the darkened beam of light is projected again to the photoresist film through the mask and the optical projection system to carry out a second exposure at a different position from that in the first exposure. A surface of the photoresist film is not in accordance with a focal plane of the optical projection system during the first and second exposures, respectively. The pattern of the mask is transferred on the photoresist film through the first and second exposures.
REFERENCES:
patent: 5255050 (1993-10-01), Kitagawa
patent: 5305054 (1994-04-01), Suzuki et al.
H. Fukuda et al., "A New Method for Enhancing Focus Latitude in Optical Lithography: FLEX", IEEE Electron Device Letters, vol. EDL-8, No. 4, Apr. 1987, pp. 179-180.
N. Shiraishi et al., "New Imaging Technique for 64M-DRAM", SPIE, vol. 1674, Optical/Laser Microlithography V, (1992) pp. 741-752.
NEC Corporation
Rosasco S.
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