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Proceedings Paper

Polarization-induced astigmatism caused by topographic masks
Author(s): Johannes Ruoff; Jens Timo Neumann; Emil Schmitt-Weaver; Eelco van Setten; Nicolas le Masson; Chris Progler; Bernd Geh
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Paper Abstract

With the continuous shrink of feature sizes the pitch of the mask comes closer to the wave length of light. It has been recognized that in this case polarization effects of the mask become much more pronounced and deviations in the diffraction efficiencies from the well-known Kirchhoff approach can no longer be neglected. It is not only the diffraction efficiencies that become polarization-dependent, also the phases of the diffracted orders tend to deviate from Kirchhoff theory when calculated rigorously. This also happens for large structures, where these phase deviations can mimic polarization dependent wave front aberrations, which in the case of polarized illumination can lead to non-negligible focus shifts that depend on the orientation and the features size themselves. This orientation dependence results in a polarization induced astigmatism offset, which can be of the same order of magnitude or even larger as polarization effects stemming from the lens itself. Hence, for correctly predicting polarization induced astigmatism offsets, one has to both consider lens and mask effects at the same time. In this paper we present a comprehensive study of polarized induced phase effects of topographic masks and develop a simple theoretical model that accurately describes the observed effects.

Paper Details

Date Published: 30 October 2007
PDF: 15 pages
Proc. SPIE 6730, Photomask Technology 2007, 67301T (30 October 2007); doi: 10.1117/12.747039
Show Author Affiliations
Johannes Ruoff, Carl Zeiss SMT AG (Germany)
Jens Timo Neumann, Carl Zeiss SMT AG (Germany)
Emil Schmitt-Weaver, ASML US, Inc. (United States)
Eelco van Setten, ASML Netherlands (Netherlands)
Nicolas le Masson, ASML Netherlands (Netherlands)
Chris Progler, Photronics, Inc. (United States)
Bernd Geh, Carl Zeiss SMT AG (Germany)
ASML US, Inc. (United States)

Published in SPIE Proceedings Vol. 6730:
Photomask Technology 2007
Robert J. Naber; Hiroichi Kawahira, Editor(s)

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