Determination of film thickness and surface profile using reflectometry and spectrally resolved phase shifting interferometry |
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Authors: | Sanjit Kumar Debnath Joonho You and Seung-Woo Kim |
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Affiliation: | (1) Department of Engineering Science and Mechanics, Virginia Polytechnic Institute and State University (Virginia Tech), 24061 Blacksburg, VA, USA;(2) Mechanical Engineering Department, University of Maryland, 20742 College Park, MD, USA |
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Abstract: | Surface profiling and film thickness measurement play an important role for inspection in semi conductor industry. White light
source had been used as scanning white light interferometry and spectrally resolved white light interferometry for determining
surface and film thickness profile. These techniques however failed for thinner film. Recently, reflectometry and spectrally
resolved white light interferometry was combined for the same. This technique used Fourier Transform for the calculation of
phase in spectral domain with the use of Linnik interferometer. In this method a large amount of carrier offset (carrier fringes)
is required to be effective. This carrier fringes in spectrally resolved white light interferometry was achieved by increasing
the optical path difference between the test and the reference surface. But, Linnik interferometer cause defocusing problem
to create these carrier fringes. We propose in this paper to combine reflectometry and spectrally resolved phase shifting
interferometry for measurement of surface and film thickness profile with the use of Michelson objective. Michelson objective
will be convenient to implement as compared to the Linnik type and the use of phase shifting interferometry does not necessarily
need large number of fringes in the spectral domain. |
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