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Proceedings Paper

Sensitivity of SEM width measurements to model assumptions
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Paper Abstract

The most accurate width measurements in a scanning electron microscope (SEM) require raw images to be corrected for instrumental artifacts. Corrections are based upon a physical model that describes the sample-instrument interaction. Models differ in their approaches or approximations in the treatment of scattering cross sections, secondary electron (SE) generation, material properties, scattering at the surface potential barrier, etc. Corrections that use different models produce different width estimates. We have implemented eight models in the JMONSEL SEM simulator. Two are phenomenological models based upon fitting measured yield vs. energy curves. Two are based upon a binary scattering model. Four are variants of a dielectric function approach. These models are compared to each other in pairwise simulations in which the output of one model is fit to the other by using adjustable parameters similar to those used to fit measured data. The differences in their edge position parameters is then a measure of how much these models differ with respect to a width measurement. With electron landing energy, beam width, and other parameters typical of those used in industrial critical dimension measurements, the models agreed to within ±2.0 nm on silicon and ±2.6 nm on copper in 95% of comparisons.

Paper Details

Date Published: 23 March 2009
PDF: 15 pages
Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 72720R (23 March 2009); doi: 10.1117/12.814300
Show Author Affiliations
J. S. Villarrubia, National Institute of Standards and Technology (United States)
Z. J. Ding, Univ. of Science and Technology of China (China)

Published in SPIE Proceedings Vol. 7272:
Metrology, Inspection, and Process Control for Microlithography XXIII
John A. Allgair; Christopher J. Raymond, Editor(s)

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