Optics: measuring and testing – Angle measuring or angular axial alignment – With photodetection remote from measured angle
Patent
1982-04-16
1984-10-16
Buczinski, S. C.
Optics: measuring and testing
Angle measuring or angular axial alignment
With photodetection remote from measured angle
250557, 250561, 356 1, 356381, 356400, G01B 1126, G01C 310, G06K 715, G06K 1500
Patent
active
044771851
ABSTRACT:
An imaging apparatus, for instance a wafer stepper, has an optical system for forming an image of an object such as a reticle and it has a focusing device. The focusing device has detector means for determining deviations between the actual image surface of the optical system and a second surface (surface of the semiconductor wafer) on which the image is to be formed. The focusing device includes two sets of detector means, each said set having means fast with the optical system and constructed to focus a spot of monochromatic light under a large angle of incidence onto said actual image surface and means for collecting the light reflected by said second surface and focusing it on a differential light detector so located that the image of the spot is centered on the detector when the two surfaces coincide and means for summing differential signals supplied by the detectors of both sets, said sets being arranged for the light path in the two sets of detector means to be substantially reverse from each other.
REFERENCES:
patent: 3612698 (1971-10-01), Mathisen
patent: 3645623 (1972-02-01), Patten
patent: 3775011 (1973-11-01), Marsh
patent: 3865483 (1975-02-01), Wojcik
patent: 4090068 (1978-05-01), Widmann et al.
Rhodes, K. E., "Semiconductor Chip Leveling Apparatus", IBM Tech. Disclosure Bulletin, vol. 21, No. 10, 3/79-pp. 4121-4122.
"Step-and-Repeat Wafer Imaging", by S. Wittekoek, Solid State Technology, vol. 23, Jun. 1980, pp. 80-84.
Berger Laurent
Tigreat Paul
Buczinski S. C.
Euromask
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