Optics: measuring and testing – By alignment in lateral direction – With registration indicia
Patent
1979-05-30
1980-11-11
Corbin, John K.
Optics: measuring and testing
By alignment in lateral direction
With registration indicia
G01B 1127
Patent
active
042329698
ABSTRACT:
A dark field optical alignment apparatus is described for a projection exposure system wherein a tilted plane mirror (37) having at least one elliptical hole is positioned between a pattern mask (7) and a telecentric projection objective (45) to reflect diffracted light from alignment aids on a surface out of a main optical axis of the projection exposure system. Radiation is passed through alignment aid slits in the pattern mask and is transmitted through the elliptical hole in the plane mirror to illuminate corresponding edges (13, 15, 17) of the alignment aids on a wafer. Directly reflected light from the alignment aids is focused back through the elliptical hole by the telecentric objective. Diffracted light from the alignment aid edges is passed by the outer portion of the projection objective to the reflective surface of the plane mirror which reflects the radiation to a photo-detector that measures the intensity of the reflected radiation. The radiation from the alignment aid slits is scanned across the associated edges of the alignment aids until a maximum radiation intensity is detected by the photo-detector. The maximum radiation intensity indicates that the pattern mask and the wafer are in alignment.
REFERENCES:
patent: 1943509 (1934-01-01), Bauersfeld
patent: 3752560 (1973-08-01), Lunn
patent: 3885877 (1975-05-01), Horwath et al.
patent: 4062623 (1977-12-01), Suzuki et al.
patent: 4153371 (1979-05-01), Koizumi et al.
patent: 4165149 (1979-08-01), Suzuki et al.
Makosch, G. "Dark Field Illumination Device," IBM Technical Disclosure Bulletin, vol. 17, No. 11 (Apr. 1975) p. 3264.
Khoury, H. A. "Scattered Light Feedback Detector for Automatic Wafer Alignment," IBM Technical Disclosure Bulletin, vol. 18, No. 2 (Jul. 1975) p. 414.
Corbin John K.
International Business Machines - Corporation
Rosenberger R. A.
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