Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1999-02-02
2000-08-22
Hantis, K. P.
Optics: measuring and testing
By polarized light examination
With light attenuation
G01B 1114
Patent
active
061080896
ABSTRACT:
By scanning a wafer mark to be detected in a measurement direction with respect to a sheet-shaped laser beam and by photoelectrically converting diffraction light generated from the wafer mark, a mark detection signal f(X) is obtained as a function of an X-coordinate value of the wafer mark. On the basis of an emphasized signal g(X) obtained by effecting convolution calculation of a numerical filter with respect to the mark detection signal f(X), slice level S1, Sr for both edge portions of the mark detection signal are determined, an average value of X-coordinate values of intersections between the slice levels S1, Sr and the mark detection signal f(X) or the emphasized signal g(X) is used as a detection position of the wafer mark. Alternatively, by scanning a wafer mark to be detected in a measurement direction with respect to a sheet-shaped laser beam and by photoelectrically converting diffraction light generated from the wafer mark, a mark detection signal f(X) is obtained as a function of an X-coordinate value of the wafer mark. Reference signals g(X) in which the change portions (edges) of the mark detection signals obtained from other wafer marks are previously determined, and correlation function h(X) between the reference signals g(X) and the mark detection signal f(X), and an X-coordinate value X1 when the relative function h(X) becomes maximum is used as the position of the wafer mark.
REFERENCES:
patent: 4962318 (1990-10-01), Nishi
patent: 5140366 (1992-08-01), Shiozawa et al.
patent: 5253040 (1993-10-01), Kamon et al.
patent: 5493403 (1996-02-01), Nishi
Hantis K. P.
Nikon Corporation
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