Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1981-11-09
1984-10-02
Britton, Howard W.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
382 8, 358107, H04N 718
Patent
active
044751222
ABSTRACT:
This automatic wafer alignment technique may be used in a step-and-repeat photomicrolithographic exposure system accurately to prealign a wafer before exposure to the B-level and subsequent reticles, and automatically to align the wafer at each die site prior to exposure. A search technique optimizes location of the global targets used for wafer prealignment. The search begins at the most likely target position and proceeds through a search area established by the maximum expected rough prealignment error. A wafer alignment target configuration consisting of a cross with one elongated arm and a short crossbar is used to optimize target verification. To locate targets a video image is digitized and the average intensity at each video scan line and column is obtained and stored. This data is used to determine the presence in the video image of feature edges. A table of all such edges is established. These listed edges are correlated to determine all pairs of edges that may represent potential targets. From these, the best target is selected by comparing certain weighted parameters of each potential target.
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patent: 4253112 (1981-02-01), Doemens
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Britton Howard W.
TRE Semiconductor Equipment Corporation
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