Image analysis – Applications – Manufacturing or product inspection
Patent
1998-02-24
2000-08-08
Boudreau, Leo H.
Image analysis
Applications
Manufacturing or product inspection
356401, G06K 900, G01B 1100
Patent
active
06101267&
ABSTRACT:
A plurality of alignment marks disposed on a substrate is photoelectrically detected, and detected photoelectric signals are added to phase-shifted signals produced by shifting the phase of the detection signals to produce a sum signal. The phase is shifted by quantities corresponding to the intervals between the marks to superpose the peaks of the detection signals on the peaks of the phase-shifted signals. A correlation is determined between the sum signal and a reference signal corresponding to the narrow width of detection. A position where the coefficient of correlation is a maximum value is taken as the mark position. Thus, it is possible to use a reference signal having less peaks and a narrow width in the detecting direction, so that the number of times of product-sum calculation for calculation of the correlation can be small as compared with that when a reference signal having as many peaks as the marks and a same periodicity. The mark can be detected in a shorter time to raise the throughput of a mass production of semiconductor devices which are produced by exposing a substrate.
REFERENCES:
patent: 4688088 (1987-08-01), Hamazaki et al.
patent: 4860374 (1989-08-01), Murakami et al.
patent: 5500736 (1996-03-01), Koitabashi et al.
Boudreau Leo H.
Cage Shawn B
Nikon Corporation
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