Apparatus for controlling relation in position between a photoma

Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems

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356400, G01V 904, G01B 1100

Patent

active

048702897

ABSTRACT:
A system for controlling the relation in position between a photomask and a wafer for use in manufacturing apparatus of a highly integrated circuit such as large scale integration (LSI). The position control system includes a coherent light source for generating two light beams which are different in frequency and polarizing direction from each other. The light beams from the coherent light source is introduced into a first diffraction grating and the diffracted light from the first diffraction grating selectively pass through a telecentric lens system and are led to second and third diffraction gratings respectively disposed on the photomask and the wafer. Light beat signals are obtained in correspondance with the diffracted light from the second and third difraction gratings and the position relation between the photomask and wafer is controlled on the basis of the phase difference between the obtained light beat signals which corresponds to the position difference between the photomask and the wafer.

REFERENCES:
patent: 3541338 (1970-11-01), Duda et al.
patent: 3867038 (1975-02-01), Westell
patent: 4631416 (1986-12-01), Trutna, Jr.
patent: 4664524 (1987-05-01), Hattori et al.
patent: 4780616 (1988-10-01), Nishi et al.

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