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Imaging ellipsometry for curved surfaces

: Negara, Christian; Längle, Thomas; Beyerer, Jürgen


Journal of vacuum science and technology B. Microelectronics and nanometer structures 38 (2020), Nr.1, Art. 014016
ISSN: 0734-211X
ISSN: 1071-1023
ISSN: 2166-2746
ISSN: 2166-2754
Fraunhofer IOSB ()

The authors propose a new design of an imaging return-path ellipsometer, which enables reflection-based measurements of both flat and curved surfaces. Return-path ellipsometry (RPE) based on mirrors cannot be applied to surface characterization of a specimen with a free-form shape. The authors circumvent this restriction by using microsphere-based retroreflectors instead of a mirror. The measurement equation for retro reflection-based RPE is very similar to that for mirror-based RPE. Therefore, the authors first outline the difference between conventional (unidirectional) and return-path (bidirectional) ellipsometry by focusing on Mueller-matrix ellipsometry. Furthermore, they present a new ellipsometer consisting of a rotating reflector to determine the surface inclination for almost arbitrary media when scattering and diffraction are negligible.