Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1992-10-14
1994-02-08
Evans, F. L.
Optics: measuring and testing
By polarized light examination
With light attenuation
356364, 356401, G01B 1100
Patent
active
052852580
ABSTRACT:
A semiconductor wafer, which has a diffractive grating array acting as a alignment mark, is irradiated with a polarized light beam while relatively moving the semiconductor wafer and the polarized light beam. The polarized light beam consists of a polarized component which vibrates in a direction substantially perpendicular to the diffractive grating array. A diffractive light beam from the wafer is received to measure the light intensity thereof. On the basis of the measured intensity, the diffractive grating array is detected. Thus, it is possible to accurately detect the alignment mark.
REFERENCES:
patent: 4938598 (1990-07-01), Akiyama et al.
Evans F. L.
Mitsubishi Denki & Kabushiki Kaisha
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