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Proceedings Paper

Spatial Coherence: The Key To Accurate Optical Micrometrology
Author(s): D. Nyyssonen
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Paper Abstract

The accurate measurement of micrometer-size iinewidths on integrated-circuit photo casks and wafers requires more accurate edge detection tecnniques than traditional optical measuring systems can achieve. A scanning pnotometric optical microscope has the capability of determining edge location using an optical threshold with a resulting linewidth error much smaller than the Airy disc radius of the imaging oujective. However, the threshold corresponding to edge location is dependent upon the spatial coherence of the illumination. Analysis using tne theory of partial coherence has led to threshold equations witn corrections for contrast and optical phase difference at the line edge. Both the tneory and instrumentation which have been developed for measurements on both pnotomasks and wafers are described. Linewidths as small as 0.5 µm can be measured with a sensitivity of 0.01 µm and an estimated uncertainty of 0.05 µm.

Paper Details

Date Published: 25 October 1979
PDF: 11 pages
Proc. SPIE 0194, Applications of Optical Coherence, (25 October 1979); doi: 10.1117/12.957906
Show Author Affiliations
D. Nyyssonen, National Bureau of Standards (United States)


Published in SPIE Proceedings Vol. 0194:
Applications of Optical Coherence
William H. Carter, Editor(s)

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