Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1996-12-27
1999-06-08
Font, Frank G.
Optics: measuring and testing
By polarized light examination
With light attenuation
356373, 356401, 356399, 250548, 250561, 250557, 250491, G01B 1114
Patent
active
059108436
ABSTRACT:
A positioning apparatus and a method which enables precise positioning of a mask and a wafer without being influenced by the deviation of the gap between the mask and wafer or the positional deviation of the irradiated light beam. A light beam irradiates on a first mark of a first object and a second mark of a second object. The relative position of the two objects is detected on the basis of a plurality of spot images of the light beam transmitting through the two marks, or being reflected upon or diffracted upon the marks. Each centroid of the plurality of spots is detected and a first alignment amount is obtained; in addition, a correction amount for the first alignment is obtained by applying the fuzzy inference method based on an additional signal, such as the positional relation of the first and second objects or the positional relation of the irradiated light beam and the first mark.
REFERENCES:
patent: 4780617 (1988-10-01), Umatate et al.
patent: 4971444 (1990-11-01), Kato
patent: 5153678 (1992-10-01), Ota
patent: 5543921 (1996-08-01), Uzawa et al.
Canon Kabushiki Kaisha
Font Frank G.
Ratliff Reginald A.
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