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Proceedings Paper

Use of computer optimization programs for the enhancement of Nikon stepper throughput with defectivity reduction benefits
Author(s): Yumiko Takamori; Christof G. Krautschik
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Paper Abstract

It is known that the wafer shot maps generated by the Nikon stepper software are not truly optimum, and if one can understand the uniqueness of the Nikon software, more die may be placed on the wafer. We have developed two software applications: WAFER OPT finds an optimum wafer shot layout, and GRAPH DRAW draws an existing wafer shot map generated by the Nikon stepper software for comparison to the optimized version. A `cleaner' shot map, with fewer clusters yet significantly more die on the wafer, can be achieved after assessing the validity of changing an existing wafer map to an optimum one. Hence, the two computer applications can result in greatly enhanced stepper throughput and reduced defectivity from the partial clusters often necessary in a nonoptimum wafer shot map. Given a set of parameters such as exposure field dimensions, die layout within a reticle, partial cluster criterion, wafer size, wafer flat length, wafer edge exclusion width, and wafer identification character size, the WAFER OPT program mathematically finds a shot map having the maximum number of complete die using the minimum number of shots and having the least sensitivity to map placement errors of the stepper stage. In addition, WAFER OPT calculates x and y map offsets, uniquely defined in the Nikon software, that can be directly entered in the stepper data file. Another software application called GRAPH DRAW can be used to draw an existing wafer shot map for comparison to the optimized version. A case that resulted in a significant increase in the number of die per wafer and a decrease in both the number of exposure fields and the number of partial die on the wafer is presented.

Paper Details

Date Published: 1 June 1992
PDF: 10 pages
Proc. SPIE 1673, Integrated Circuit Metrology, Inspection, and Process Control VI, (1 June 1992); doi: 10.1117/12.59818
Show Author Affiliations
Yumiko Takamori, Motorola, Inc. (United States)
Christof G. Krautschik, Optical Sciences Ctr./Univ. of Arizona (United States)

Published in SPIE Proceedings Vol. 1673:
Integrated Circuit Metrology, Inspection, and Process Control VI
Michael T. Postek, Editor(s)

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