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Proceedings Paper

Focus vernier for optical lithography
Author(s): William H. Arnold; Eytan Barouch; Uwe Hollerbach; Steven A. Orszag
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Paper Abstract

As the depth of focus of optical steppers grows smaller, it becomes more important to determine the position of best focus accurately and quickly. This paper describes the use of phase-shifted mask technology to form a focus vernier: a phase pattern on the stepper reticle which, when imaged in resist, can give both the magnitude and the direction of the focus error. In this, the focus vernier structure is analogous to 3overlay verniers. Thus the determination of focus error can be treated as an alignment problem in the z-axis. This technique is an improvement on previous schemes for the determination of best focus from resist images as it can indicate both the magnitude of the error and its direction in a single exposure.

Paper Details

Date Published: 4 August 1993
PDF: 13 pages
Proc. SPIE 1926, Integrated Circuit Metrology, Inspection, and Process Control VII, (4 August 1993); doi: 10.1117/12.148958
Show Author Affiliations
William H. Arnold, Advanced Micro Devices, Inc. (United States)
Eytan Barouch, Princeton Univ. (United States)
Uwe Hollerbach, Princeton Univ. (United States)
Steven A. Orszag, Princeton Univ. (United States)

Published in SPIE Proceedings Vol. 1926:
Integrated Circuit Metrology, Inspection, and Process Control VII
Michael T. Postek, Editor(s)

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