Stepper overlay performance measurements using the air-turbulence-compensated interferometer

Philip D. Henshaw

doi:10.1117/12.240942

7 June 1996 Stepper overlay performance measurements using the air-turbulence-compensated interferometer

Philip D. Henshaw

Proceedings Volume 2726, Optical Microlithography IX; (1996) https://doi.org/10.1117/12.240942
Event: SPIE's 1996 International Symposium on Microlithography, 1996, Santa Clara, CA, United States

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.

Citation Download Citation

Philip D. Henshaw "Stepper overlay performance measurements using the air-turbulence-compensated interferometer", Proc. SPIE 2726, Optical Microlithography IX, (7 June 1996); https://doi.org/10.1117/12.240942

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