Polarization modulation imaging ellipsometry for thin film thickness measurement |
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Authors: | Chien Chou Hui-Kang Teng Chih-Jen Yu |
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Affiliation: | a Institute of Medical Imaging and Radiological Sciences and Institute of Biophotonics, National Yang-Ming University, Taipei 112, Taiwan b Department of Optics and Photonics, National Central University, Jhongli 320, Taiwan c Department of Electrical Engineering, Nan-Kai Institute of Technology, Nan-Tou 542, Taiwan |
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Abstract: | A polarization modulation (PM) imaging ellipsometer is proposed and setup in order to measure precisely the thickness of thin film. Five images are collected sequentially by CCD camera with respect to five pre-determined azimuth angles of a quarter wave plate (QWP) during measurement. Then two-dimensional (2-D) distributions of the ellipsometric parameters ψ and Δ over the full dynamic range are obtained. Conceptually, PM imaging ellipsometer integrates the features of phase shift interferometry with conventional photometric ellipsometry by rotating the QWP sequentially to produce polarization modulation that is able to measure the thickness of a thin film in two dimensions precisely and quickly. The basic principle of PM imaging ellipsometer is derived wherein features such as common path configuration, full dynamic range of measurement, and insensitive to non-uniform response of the CCD are analyzed. The experimental results verify the ability and performance of PM imaging ellipsometer on 2-D thin film thickness, while the errors regarding the ellipsometric parameters measurements are discussed. |
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