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Proceedings Paper

Modeling the effect of finite size gratings on scatterometry measurements
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Paper Abstract

The interpretation of scatterometry measurements generally assumes that the grating extends over an area large enough to intercept all the illumination provided by an incident beam. However, in practice, the gratings used in scatterometry are relatively small. Thus, the detected light also includes both that scattered by the grating as well as that from a region surrounding the grating because, generally, the incident beam illuminates both the grating and the surrounding region. To model the effects of such real structures, simulations of the effective reflectance were performed whereby the reflection from the grating was considered to be the sum of the diffraction by the grating and the diffraction of the surrounding region, taking into account the beam profile. To demonstrate the model, the illumination field was assumed to be Gaussian. Results are shown for a specific target design consisting of a 50 μm square measured by normal incidence reflectometry. Significant errors occur when the incident profile has wings that fall outside of the profile and when the scattered light is partially apertured.

Paper Details

Date Published: 25 March 2008
PDF: 8 pages
Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69223P (25 March 2008); doi: 10.1117/12.772769
Show Author Affiliations
Elizabeth Kenyon, National Institute of Standards and Technology (United States)
Michael W. Cresswell, National Institute of Standards and Technology (United States)
Heather J. Patrick, National Institute of Standards and Technology (United States)
KT Consulting, Inc. (United States)
Thomas A. Germer, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 6922:
Metrology, Inspection, and Process Control for Microlithography XXII
John A. Allgair; Christopher J. Raymond, Editor(s)

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