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Proceedings Paper

Stepper overlay performance measurements using the air-turbulence-compensated interferometer
Author(s): Philip D. Henshaw
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Paper Abstract

Air turbulence affects the performance of the helium-neon interferometer used to control the wafer stage of stepper or step and scan lithography systems. In this paper we describe the principles of operation and in-stepper performance of an air turbulence compensated interferometer designed to address these problems. Collinear combination of a two-wavelength compensation system using second harmonic interferometry, with the existing HeNe interferometer used for length measurement, provides a highly accurate system with real-time compensation for air turbulence. This paper reports on the hardware configuration and preliminary performance evaluation of an ATCI system which has been installed on a semiconductor wafer stepper. A brief overview of the signal processing algorithms is provided, showing the automatic compensation features and noise insensitivity of the algorithm.

Paper Details

Date Published: 7 June 1996
PDF: 12 pages
Proc. SPIE 2726, Optical Microlithography IX, (7 June 1996); doi: 10.1117/12.240942
Show Author Affiliations
Philip D. Henshaw, SPARTA, Inc. (United States)

Published in SPIE Proceedings Vol. 2726:
Optical Microlithography IX
Gene E. Fuller, Editor(s)

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