Position detector for detecting the position of an object using

Details Position detector for detecting the position of an object using Position detector for detecting the position of an object using

1992-09-21

1994-11-29

Turner, Samuel A.

Optics: measuring and testing

By particle light scattering

With photocell detection

356363, 356356, G01B 902

Patent

active

053694864

ABSTRACT:
A position detector includes a diffraction grating provided on the surface of an object, an illumination system for illuminating the diffraction grating, a detection system for detecting diffracted light diffracted from the diffraction grating, and a processing system for detecting positional information relating to the object. The illumination system emits a first pair of beams which are diffracted by the diffraction grating and interfere with each other, and emits a second pair of beams which are diffracted by the diffraction grating and also interfere with each other. The first pair of beams are incident upon the diffraction grating along a plane extending in a first direction in which the diffraction grating extends. The second pair of beams are incident upon the diffraction grating along a plane extending in a second direction in which the diffraction grating extends. The first and second directions are different from a grating line direction. The detection system detects the interfering light and generates first and second beat signals therefrom. The processing system detects positional information with respect to the first direction from the phase state of the first beat signal and with respect to the second direction from the phase state of the second beat signal.

REFERENCES:
patent: 4710026 (1987-12-01), Magome et al.
patent: 5000573 (1991-03-01), Suzuki et al.
patent: 5114236 (1992-05-01), Matsugu et al.
patent: 5148037 (1992-09-01), Suda et al.
IBM Technical Disclosure Bulletin, vol. 32, No. 10B, Mar. 1990, pp. 214-217, "Interferometric Method of Checking the Overlay Accuracy in Photolithographic Exposure Processes".

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