Apparatus and method for fine alignment of a photomask to a semiconductor wafer
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United States of America Patent
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May 5, 1981
Issued Date -
N/A
app pub date -
Mar 14, 1979
filing date -
Nov 4, 1977
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A method and apparatus are disclosed for fine aligning a photomask to a semiconductor using the interference and diffraction effects produced by coherent light impinging upon or passing through repetitive patterns on a photomask and a semiconductor. A plurality of photodetectors are employed to convert the interference information into phase dependent electrical signals that are used to control conventional X, Y and .theta. workpiece positioning mechanisms.
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