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Proceedings Paper

Automatic feedback control to optimize stepper overlay
Author(s): Mark Drew Jr.; Kevin G. Kemp
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Paper Abstract

Systematic offset errors can be a major contributor to total overlay error on projection wafer steppers. To compensate for this offset error we have developed an automated method using measured overlay results from previous lots to generate offset correction values for current lots. This method provides statistically optimized offset corrections while eliminating the need to process test wafers. In addition the dynamic correction capability of the feedback control loop automatically compensates for offset changes such as drift in stepper alignment systems, process modification, and mask revisions. The system has been in use for over a year and has proven extremely effective in eliminating systematic offset errors on numerous devices.

Paper Details

Date Published: 4 August 1993
PDF: 7 pages
Proc. SPIE 1926, Integrated Circuit Metrology, Inspection, and Process Control VII, (4 August 1993); doi: 10.1117/12.148965
Show Author Affiliations
Mark Drew Jr., Motorola, Inc. (United States)
Kevin G. Kemp, Motorola, Inc. (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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