Inspection of sub-wavelength structures and zero-order gratings using polarization interferometry

Michael Totzeck; Alexander V. Tavrov; Norbert Kerwien; Hans J. Tiziani

doi:10.1117/12.472233

20 June 2002 Inspection of subwavelength structures and zero-order gratings using polarization interferometry

Michael Totzeck, Alexander V. Tavrov, Norbert Kerwien, Hans J. Tiziani

Proceedings Volume 4777, Interferometry XI: Techniques and Analysis; (2002) https://doi.org/10.1117/12.472233
Event: International Symposium on Optical Science and Technology, 2002, Seattle, WA, United States

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.

Citation Download Citation

Michael Totzeck, Alexander V. Tavrov, Norbert Kerwien, and Hans J. Tiziani "Inspection of subwavelength structures and zero-order gratings using polarization interferometry", Proc. SPIE 4777, Interferometry XI: Techniques and Analysis, (20 June 2002); https://doi.org/10.1117/12.472233

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