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Proceedings Paper

Characterization of spatial coherence uniformity in exposure tools
Author(s): Ilya M. Grodnensky; Etsuya Morita; Kyoichi Suwa; Shigeru Hirukawa
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Paper Abstract

A novel technique to characterize variations of the spatial (partial) coherence (sigma) across the image field in modern steppers and scanners has been developed and experimentally tested. It is based on the high sensitivity of the length L of macroscopically large diamond-shaped marks printed in photoresist to (sigma) variation. Variations in the (sigma) value across the image field lead to variations in the length of marks printed at different image field locations. The mark lengths are measured rapidly with high accuracy by a built-in optical system and then converted into (sigma) values using the calibration dependence L((sigma) ) measured in the same exposure tool. Simulation and experimental studies show that the level of projection lens aberrations in modern Nikon tools have practically no effect on (sigma) measurements obtained with this technique. Our results demonstrate that in the conventional illumination scheme, (sigma) distribution can be measured with an accuracy of 2.5%. The main advantage of the presented method is that (sigma) variation over the image field is characterized by the exposure tool itself, avoiding expensive and time-consuming SEM measurements. Moreover, since the measurement procedure is based on the wedge-shaped marks and laser scanning system currently used in Nikon tools for automated focus detection, implementation of the technique does not require any hardware or software modification.

Paper Details

Date Published: 29 June 1998
PDF: 8 pages
Proc. SPIE 3334, Optical Microlithography XI, (29 June 1998); doi: 10.1117/12.310758
Show Author Affiliations
Ilya M. Grodnensky, Nikon Precision Inc. (United States)
Etsuya Morita, Nikon Precision Inc. (United States)
Kyoichi Suwa, Nikon Corp. (Japan)
Shigeru Hirukawa, Nikon Corp. (Japan)

Published in SPIE Proceedings Vol. 3334:
Optical Microlithography XI
Luc Van den Hove, Editor(s)

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