On-axis interferometric alignment of plates using the spatial ph

Details On-axis interferometric alignment of plates using the spatial ph On-axis interferometric alignment of plates using the spatial ph

1993-06-01

1995-05-09

Hille, Rolf

Optics: measuring and testing

By polarized light examination

With birefringent element

356356, 356401, 250548, G01B 902, G01V 904

Patent

active

054145147

ABSTRACT:
There are first and second relatively movable plates. On a face of each of the first and second plates, there are first and second alignment marks, each being a linear grating of parallel lines of uniform spatial period, the spatial periods being different from each other. There is a light source for illuminating the linear grating on the second plate through the linear grating on the first plate to produce an interference pattern. Indicia on the first or second plates indicate a periodic reference pattern having a phase. A detector is configured to detect when the spatial phase of the interference pattern and the spatial phase of said reference pattern differ by a predetermined value. A position adjustor is for adjusting the relative position of the first and second plates until the detector detects said phase difference.

REFERENCES:
patent: 4340305 (1982-07-01), Smith et al.
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patent: 5189494 (1993-02-01), Muraki
patent: 5216257 (1993-06-01), Brueck et al.
Jahns et al., "Precise Alignment Through Thick Wafers Using an Optical Copying Technique", Optics Letters, vol. 17, No. 6, Mar. 15, 1992.
Flanders et al., "A New Interferometric Alignment Technique", Applied Physics Letters, vol. 31, No. 7, Oct. 1, 1977.
Kinoshita et al., "A Dual Grating Alignment Technique for X-ray Lithography", J. Vac. Sci. Technol. B, vol. 1, No. 4, Dec. 1983.

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