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Proceedings Paper

Fast data acquisition in imaging ellipsometry using four-frame method
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Paper Abstract

Ellipsometry is known as high precision metrology for thin film thickness measurements with sub-angstrom resolution. In ellipsometric measurements it does not measure film thickness or optical constants directly. It measures ellipsometric parameters, ψ and Δ, namely, defined as the ratio of reflection coefficients for p- and s-polarized light. Generally in rotating component ellipsometry, light intensity values at more than 256 angular positions of polarizer or analyzer with discrete Fourier transform methods are used to evaluate Fourier coefficients, which can be calculated to ellipsometric parameters explicitly. Using this scheme it is well suited in single point measuring ellipsometry, but it degrades measurement speed in imaging ellipsometry. In imaging ellipsometry due to the limitation in CCD detection speed, rotating components must move stepwisely, so more discrete positions of polarizer or analyzer takes more measurement time dramatically. So we propose four frame method which can be easily substituted for conventional discrete Fourier transform methods. Four frame method can save measurement time, but natively intensity measurements at only four angular positions can cause erroneous results in Fourier coefficients compared with that of discrete Fourier transform method. In the four frame method, many repetitive measurements for light intensity at each angular position can solve these shortcomings. That is, conceptually to reduce random noise in ellipsometric measurements, conventional discrete Fourier transform method uses spatial averaging technique, but four frame method uses temporal averaging technique. In our experiments we could get more than ten times fast measurements with four frame method.

Paper Details

Date Published: 14 February 2005
PDF: 9 pages
Proc. SPIE 5634, Advanced Sensor Systems and Applications II, (14 February 2005); doi: 10.1117/12.576807
Show Author Affiliations
Won Chegal, Korea Research Institute of Standards and Science (South Korea)
Yong Jai Cho, Korea Research Institute of Standards and Science (South Korea)
Hyun Mo Cho, Korea Research Institute of Standards and Science (South Korea)
Yun Woo Lee, Korea Research Institute of Standards and Science (South Korea)
Soo Hyun Kim, Korea Advanced Institute of Science and Technology (South Korea)

Published in SPIE Proceedings Vol. 5634:
Advanced Sensor Systems and Applications II
Yun-Jiang Rao; Osuk Y. Kwon; Gang-Ding Peng, Editor(s)

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