High resolution alignment technique and apparatus

Details High resolution alignment technique and apparatus High resolution alignment technique and apparatus

1978-06-05

1980-03-18

Evans, F. L.

Optics: measuring and testing

Angle measuring or angular axial alignment

Sides of angle or axes being aligned transverse to optical...

250237G, 356401, G01B 1127

Patent

active

041936876

ABSTRACT:
There is provided a technique and apparatus for aligning a mask to a substrate with high precision using Moire fringe effects produced by superimposing diffraction gratings. The gratings comprise first and second patterns of horizontal and vertical lines and spaces, respectively. The first pattern comprises horizontal and vertical lines and spaces of a first width. The second pattern comprises horizontal and vertical lines of a second width which differs from the lines in the first pattern by a small amount .DELTA.. The patterns are superimposed to provide a Moire fringe effect. When alignment occurs, a symmetrical pattern is provided. If misalignment in the X, Y or .theta. coordinate occurs, an assymmetrical or skewed pattern of Moire fringe effects is generated.

REFERENCES:
patent: 3688570 (1972-09-01), Burke
patent: 3806254 (1974-04-01), Ha et al.
patent: 4047585 (1977-09-01), Dlugos
patent: 4074131 (1978-02-01), Schwebel
Oster et al., "Moire Patterns," Scientific American, May 1963, pp. 54-63.

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