Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1988-06-29
1989-08-29
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
356401, G01N 2186
Patent
active
048620084
ABSTRACT:
A wafer is aligned by using an alignment light having a longer wavelength than an exposure light. Exposure and alignment are effected through a common reduction lens. A wavefront aberration caused by the use of the long wavelength alignment light is compensated by a hologram. Thus, an alignment precision is improved without exposing a resist layer to a light.
REFERENCES:
patent: 4668089 (1987-05-01), Oshida et al.
patent: 4677301 (1987-06-01), Tanimoto et al.
patent: 4771180 (1988-09-01), Nomura et al.
patent: 4779986 (1988-10-01), Nakashima et al.
Proceedings of SPIE-The International Society for Optical Engineering, vol. 633, 1986.
Nakashima Naoto
Oshida Yoshitada
Yoshitake Yasuhiro
Allen Stephone B.
Hitachi , Ltd.
Nelms David C.
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