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Proceedings Paper

Effective-medium model for fast evaluation of scatterometric measurements on gratings
Author(s): Andrea Weidner; Matthias Slodowski; Christian Halm; Claus Schneider; Lothar Pfitzner
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Paper Abstract

Scatterometry is now an accepted technique for linewidth measurement in semiconductor manufacturing. To reduce the evaluation time when using real-time optimization procedures, we introduce an effective-medium approach to simulate the optical signatures of subwavelength line-and-space gratings. Such gratings behaves approximately like uniaxial crystals whose optical properties are completely described by two refractive indices. We propose an algebraic method for their calculation up to second order in pitch/wavelength for the extraordinary index, and up to 4th order in pitch/wavelength for the ordinary index. The formulas are valid for any angle of incidence and can be used with standard matrix formalism to calculate the optical properties of any arbitrary layer stack. We deduce the formulas for the indices. The comparison of effective medium-calculations to rigorous coupled wave simulations for spectral measurements (polarized reflectometer and spectroscopic ellipsometer) shows excellent agreement. The sensitivity of scatterometry to tilt of the structures is very low for all measurement parameters except phase difference. It is shown that left and right tilt cannot be distinguished at all with spectral measurements with non-conical incidence of light.

Paper Details

Date Published: 24 May 2004
PDF: 12 pages
Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004); doi: 10.1117/12.535147
Show Author Affiliations
Andrea Weidner, Fraunhofer Institute of Integrated Systems and Device Technology (Germany)
Matthias Slodowski, Leica Microsystems Semiconductor GmbH (Germany)
Christian Halm, Leica Microsystems Semiconductor GmbH (Germany)
Claus Schneider, Fraunhofer Institute of Integrated Systems and Device Technology (Germany)
Lothar Pfitzner, Fraunhofer Institute of Integrated Systems and Device Technology (Germany)


Published in SPIE Proceedings Vol. 5375:
Metrology, Inspection, and Process Control for Microlithography XVIII
Richard M. Silver, Editor(s)

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