Method and apparatus for measuring film thickness in multilayer thin film stack by comparison to a reference library of theoretical signatures
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United States of America Patent
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Sep 10, 1996
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N/A
app pub date -
Dec 22, 1993
filing date -
Dec 22, 1993
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Expired
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Abstract
The thicknesses of a first layer and of a second layer on a semiconductor wafer can be measured together by assuming that the second layer has a substantially uniform thickness. The thicknesses are measured by measuring reflectivity as a function of wavelength at a plurality of points on the wafer to provide a plurality of signatures, comparing each signature with signatures from libraries of theoretical signatures by calculating an error value associated with each signature; and determining the minimum error value. Each library is based upon a unique assumed thickness of the second layer. Thus, the thickness of the second layer is determined by identifying the library associated with the minimum error value.
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