Apparatus for projecting a pattern on a semiconductor substrate
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United States of America Patent
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Jun 3, 1986
Grant Date -
N/A
app pub date -
Jan 23, 1985
filing date -
Jan 23, 1984
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
An apparatus for determining the focus state of a system for the projection exposure of a mask on a semiconductive substrate for producing integrated circuits without relatively displacing the mask, projection objective and substrate along the common optical axis, utilizes an arrangement for varying cyclically the optical path length for rays at least arising from a projected image on the substrate and running through the objective to a detector plane so that an intensity measurement of the light intensity at this plane indicates the path length required for sharpness and hence the focus state of the projection assembly.
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