Thin film detection method and apparatus
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United States of America Patent
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Aug 10, 1999
Grant Date -
N/A
app pub date -
Mar 11, 1997
filing date -
Mar 11, 1997
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A method and apparatus for detecting the presence of a thin film such as a photoresist film on a semiconductor wafer or other substrate. Only when a film is present does the surface reflectance (reflective power) of light incident on the wafer surface vary sinusoidally when the incidence angle of the light is varied. This sinusoidal variation in the reflected optical power is due to interference occurring between the film surface and wafer surface reflections. This method and apparatus allows determining whether an undeveloped photoresist layer is present on a wafer; this is not possible using merely visual inspection especially when an underlying pattern is present. The present method and apparatus may also be used to determine the thickness of a particular thin film.
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