Optical device having a variable geometry filter usable for alig

Details Optical device having a variable geometry filter usable for alig Optical device having a variable geometry filter usable for alig

1989-02-22

1989-09-12

Evans, F. L.

Optics: measuring and testing

By alignment in lateral direction

With light detector

250548, 356401, G01B 1100

Patent

active

048654558

ABSTRACT:
An optical device including a spatial filter disposed at a location coincident with or in close proximity to a position optically conjugate with a pupil of a projection optical system for projecting a pattern of a mask onto a wafer. The spatial filter is adapted to intercept a light beam specularly reflected by a surface of the mask and/or by a surface of the wafer to thereby allow photoelectric detection of a light beam scatteringly reflected from the mask surface and/or the wafer surface. The spatial filter has a variable geometry filtering portion to assume high-accuracy photoelectric detection of the scatteringly reflected light beam.

REFERENCES:
patent: 4199219 (1980-04-01), Suzki et al.
patent: 4202627 (1980-05-01), Suzki et al.
patent: 4251129 (1981-02-01), Suzki et al.
patent: 4641035 (1987-02-01), Suzuki et al.
patent: 4717257 (1988-01-01), Kaneta et al.

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