Photomask blank substrate, photomask blank and photomask
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United States of America Patent
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-
Apr 1, 2008
Grant Date -
Jan 27, 2005
app pub date -
Jul 23, 2004
filing date -
Jul 25, 2003
priority date (Note) -
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status (Latency Note)
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Abstract
In a quadrangular photomask blank substrate with a length on each side of at least 6 inches, which has a pair of strip-like regions that extend from 2 to 10 mm inside each of a pair of opposing sides along an outer periphery of a substrate top surface, with a 2 mm edge portion excluded at each end, each strip-like region is inclined downward toward the outer periphery of the substrate, and a difference between maximum and minimum values for height from a least squares plane for the strip-like region to the strip-like region is at most 0.5 .mu.m. The substrate exhibits a good surface flatness at the time of wafer exposure.
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