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Proceedings Paper

Inspection of sub-wavelength structures and zero-order gratings using polarization interferometry
Author(s): Michael Totzeck; Alexander V. Tavrov; Norbert Kerwien; Hans J. Tiziani
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Paper Abstract

The low-pass characteristic of the optical imaging limits severely a quantitative measurement of structure-sizes below the optical wavelength and leads to measurement errors. On the other hand, small structures show different optical characteristics for different polarizations. A fact that corresponds to the form-birefringence of microstructures. It is described for zero-order gratings by polarization dependent dielectric constants in the effective medium theory. The birefringence can be measured accurately by use of polarization interferometry where two orthogonal polarizations interfere so that their phase-difference can be determined. To that end an electro-optic modulator is inserted into the optical path of a polarization microscope to provide the well-defined phase steps for an evaluation according to phase-shifting interferometry. From the phase difference we can conclude on the optical path-difference for both polarizations and from this - using the structure thickness - on the birefringence. Waveguide-models are applied for image interpretation. For an estimation of the width of the structure we compare polarization-interferometrical measurements with rigorous numerical simulations.

Paper Details

Date Published: 20 June 2002
PDF: 15 pages
Proc. SPIE 4777, Interferometry XI: Techniques and Analysis, (20 June 2002); doi: 10.1117/12.472233
Show Author Affiliations
Michael Totzeck, Univ. Stuttgart (Germany)
Alexander V. Tavrov, Univ. Stuttgart (Germany)
Norbert Kerwien, Univ. Stuttgart (Germany)
Hans J. Tiziani, Univ. Stuttgart (Germany)

Published in SPIE Proceedings Vol. 4777:
Interferometry XI: Techniques and Analysis
Katherine Creath; Joanna Schmit, Editor(s)

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