Photo mask, focus measuring method using the mask, and method of manufacturing semiconductor device
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United States of America Patent
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Mar 16, 2010
Grant Date -
Oct 22, 2009
app pub date -
Jul 1, 2009
filing date -
Jul 26, 2004
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A photo mask includes an asymmetrical diffraction grating pattern in which diffraction efficiencies of plus primary diffracted light and minus primary diffracted light are different, the asymmetrical diffraction grating pattern including a shielding portion which shields light, a first transmitting portion which transmits light, and a second transmitting portion which transmits light, a ratio of widths of the shielding portion, the first transmitting portion, and the second transmitting portion being n11 where n is a positive real number except 2, the asymmetrical diffraction grating pattern approximately satisfying 163°≦360°/(n+2)+θ≦197° where θ (≠90°) indicates an absolute value of a difference between a phase of the light transmitted through the first transmitting portion and that of the light transmitted through the second transmitting portion, and a reference pattern for obtaining an image as a reference for measuring a shift of an image of the asymmetrical diffraction grating pattern.
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