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Proceedings Paper

Optimization of image-based aberration metrology for EUV lithography
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Paper Abstract

EUV lithography is likely more sensitive to drift from thermal and degradation effects than optical counterparts. We have developed an automated approach to photoresist image-based aberration metrology. The approach uses binary or phase mask targets and iterative simulation based solutions to retrieve an aberrated pupil function. It is well known that a partially coherent source both allows for the diffraction information of smaller features to be collected by the condenser system, and introduces pupil averaging. In general, smaller features are more sensitive to aberrations than larger features, so there is a trade-off between target sensitivity and printability. Therefore, metrology targets using this technique must be optimized for maximum sensitivity with each illumination system. This study examines aberration metrology target optimization and suggests an optimization scheme for use with any source. Interrogation of both low and high order aberrations is considered. High order aberration terms are interrogated using two separate fitting algorithms. While the optimized targets do show the lowest RMS error under the test conditions, a desirable RMS error is not achieved by either high order interrogation scheme. The implementation of a previously developed algorithm for image-based aberration metrology is used to support this work.

Paper Details

Date Published: 17 April 2014
PDF: 8 pages
Proc. SPIE 9048, Extreme Ultraviolet (EUV) Lithography V, 90482M (17 April 2014); doi: 10.1117/12.2046483
Show Author Affiliations
Zac Levinson, Rochester Institute of Technology (United States)
Germain Fenger, Rochester Institute of Technology (United States)
Andrew Burbine, Rochester Institute of Technology (United States)
Anthony R. Schepis, Rochester Institute of Technology (United States)
Bruce W. Smith, Rochester Institute of Technology (United States)

Published in SPIE Proceedings Vol. 9048:
Extreme Ultraviolet (EUV) Lithography V
Obert R. Wood; Eric M. Panning, Editor(s)

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