Photomask alignment system

Details Photomask alignment system Photomask alignment system

1978-01-16

1980-07-08

Corbin, John K.

Optics: measuring and testing

By alignment in lateral direction

With light detector

250237G, 356356, G01B 1126, G01B 902

Patent

active

042114896

ABSTRACT:
An automatic photomask alignment system includes a monochromatic light source, such as a laser, a series of diffraction patterns which are located on a semiconductor substrate and keys which are located on photomasks with which the substrate is to be aligned. A light beam is directed through the key on a photomask onto the diffraction pattern to provide a pattern of light spots whose intensities at various locations are determined by the relative alignment of the mask and the diffraction grating. A feedback arrangement which employs photocells and means for moving the photomasks relative to the substrate provides the alignment of the photomasks with the substrate.

REFERENCES:
patent: 3756723 (1973-09-01), Hock
patent: 3930733 (1976-01-01), Holly
patent: 4103998 (1978-08-01), Nakazawa et al.
patent: 4105339 (1978-08-01), Wirtanen
Flanders et al., "A New Interferometric Alignment Technique", App. Physics Letters, vol. 31, 10-1-77, pp. 426-428.
Post, D., "Moire Fringe Multiplication with a Nonsymmetrical Doubly Blazed Reference Grating", App. Optics, vol. 10, 4-1971, pp. 901-907.

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