Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1985-07-09
1987-07-21
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250201, 356400, G01B 1100, G01J 120
Patent
active
046820370
ABSTRACT:
A projection exposure apparatus for projecting a pattern of a mask onto a semiconductor wafer through a projection optical system including plural refracting surfaces, and for irradiating the mask with a wavelength of light suitable for assuring optimum projection performances of the projection optical system to expose the wafer to the pattern of the mask, wherein at least one of the refracting surfaces of the projection optical system is provided with an interference film having an anti-reflection function relative to the wavelength of the light for the exposure of the mask, and having a predetermined reflection factor relative to a wavelength of light different from that of the exposure light, whereby the positional relation between the mask and the wafer can be detected through the projection optical system with the wavelength of light other than that of the exposure light.
REFERENCES:
patent: 3897138 (1975-07-01), Kano
patent: 4062623 (1977-12-01), Suzuki et al.
patent: 4232969 (1980-11-01), Wilczynski
patent: 4269505 (1981-05-01), Mayer
patent: 4357100 (1982-11-01), Mayer et al.
patent: 4492459 (1985-01-01), Omata
Canon Kabushiki Kaisha
Westin Edward P.
Wieland Charles
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