Mark position determining apparatus for use in exposure system

Details Mark position determining apparatus for use in exposure system Mark position determining apparatus for use in exposure system

1993-03-04

1995-08-29

Limanek, Robert P.

Optics: measuring and testing

By alignment in lateral direction

With light detector

250548, 356399, G01J 120, G01N 2147

Patent

active

054465427

ABSTRACT:
A mark position determining apparatus used in an exposure system includes a laser light source for projecting a laser beam onto an alignment mark which is formed on a substrate to be exposed with a pattern and which has a center flat surface and a pair of side surfaces. A spatial filter is located to shield a light reflected from the center flat surface of the alignment mark. But, the spatial filter has a pair of windows allowing passage of all scattered lights reflected from the side surfaces of the alignment mark even if a size and/or shape of the alignment mark vary. An image sensor is located to receive the scattered lights which have passed through the spatial filter, so as to generate an image signal. An image processor receives the image signal for obtaining a light intensity distribution of the image signal, and for discriminating whether or not a plurality of light intensity peaks included in the obtained light intensity distribution are substantially in symmetry. The image processor also operates to determine that a symmetry point is a center position of the alignment mark when the light intensity peaks are substantially in symmetry.

REFERENCES:
patent: 4659227 (1987-04-01), Sato et al.
patent: 4795260 (1989-01-01), Schnur et al.
patent: 5114236 (1992-05-01), Matsugu et al.
patent: 5218193 (1993-06-01), Miyatake
"An Advanced H-Line Stepper", Solid State Technology/Jan. 1987, Jere D. Buckley, pp. 87-93.

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