Improving stepper alignment capability through phase-shifting techniques

Mircea V. Dusa; Maciej W. Rudzinski

doi:10.1117/12.130321

1 June 1992 Improving stepper alignment capability through phase-shifting techniques

Mircea V. Dusa, Maciej W. Rudzinski

Proceedings Volume 1674, Optical/Laser Microlithography V; (1992) https://doi.org/10.1117/12.130321
Event: Microlithography '92, 1992, San Jose, CA, United States

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.

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Mircea V. Dusa and Maciej W. Rudzinski "Improving stepper alignment capability through phase-shifting techniques", Proc. SPIE 1674, Optical/Laser Microlithography V, (1 June 1992); https://doi.org/10.1117/12.130321

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KEYWORDS

Optical alignment

Phase shifts

Etching

Silicon

Diffraction

Semiconducting wafers

Diffraction gratings

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