Method of projecting printing on semiconductor substrate and workpiece including such substrate
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United States of America Patent
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Sep 20, 1983
Grant Date -
N/A
app pub date -
May 20, 1981
filing date -
May 20, 1981
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
In the projection-copying of a mask on a workpiece including a light-reflecting semiconductor substrate, the alignment of mask and workpiece is effected by illuminating marks on the substrate which appear dark relative to a surrounding area. To provide each mark with a contrasting background of sufficient brightness, a partly reflecting surface layer overlying the substrate in that area has a nonuniform optical thickness whereby cancellation of reflections due to interference is limited to isolated regions.
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