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Proceedings Paper

Improving stepper alignment capability through phase-shifting techniques
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Paper Abstract

One of the primary goals for low K1 lithography is to maintain consistent pattern alignment against wafer thin-film stack effect, substrate reflectivity and graininess. Alignment sensitivity to such perturbations is basically reflected in increases or decreases of the amount of the diffracted energy captured by the stepper alignment detectors. "Tunning" the alignment marks etch depth/thin film stack/coating thickness and uniformity with the stepper optical alignment system can improve dramatically the alignment capability of an existing machine. The present paper reports on our simulation and experimental work to "tune" the alignment mark topography to a Nikon LSA alignment system. Parameters known to affect alignment capability, such as Si etch depth or Si oxide etch depth were first analyzed and experimentally verified. Then alignment marks topographies with more complex (but also more closer to real situations) were simulated and experimentally studied. Situations when a "phase shifter" or a "phase compensator" is constructed on the LSA marks may overcome initial etch depth influence upon alignment capability and registration results. In most cases simulation results can predict "succesful alignment" when diffracted energy efficiency is higher than 3 to 5%. Phase shifters/compensators improved registration results (mean +3S) to 0.120 - 0.150um, on practical multilayer topographies.

Paper Details

Date Published: 1 June 1992
PDF: 13 pages
Proc. SPIE 1674, Optical/Laser Microlithography V, (1 June 1992); doi: 10.1117/12.130321
Show Author Affiliations
Mircea V. Dusa, SEEQ Technology, Inc. (United States)
Maciej W. Rudzinski, Nikon Precision, Inc. (United States)

Published in SPIE Proceedings Vol. 1674:
Optical/Laser Microlithography V
John D. Cuthbert, Editor(s)

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