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Proceedings Paper

A Production Proven Technique For Machine-To-Machine Overlay Matching
Author(s): Michael J. Cummings; Norman Haley; Ken Ngo; John Schaller
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Paper Abstract

The natural progression of today's semiconductor industry is toward smaller device features and tighter registration requirements. Typically, this progression results in high capital equipment investments, along with a large capacity reduction per investment dollar for most lithographic exposure processes. One major cause for the capacity loss is the industry's willingness to migrate from full-field scanning projection printers to a lower throughput field-by-field alignment step-and-repeat exposure system. Standard Microsystems Corporation (SMC) sought to achieve higher performance on its scanners without compromising throughput. The original goal at SMC was to improve Perkin-Elmer's specified Micralign 641 HT machine-to-machine registration performance from ± 0.30 micron to less than ± 0.25 micron. With this in mind, we set out to investigate the true alignment and registration limitations of a Micralign Model 600 HT Series Projection Aligner. Although SMC was apparently successful at matching two Micralign 641 HT systems to ± 0.25 micron by manually reading verniers, this technique proved to be time consuming and prone to human error. Electrical probing of wafers was considered, but the special masks and processing steps and its destructive nature were considered undesirable. For this study, an automatic optical overlay measurement system was used to optimize overlay on the SMC Micralign systems. The results were enlightening. The specified overlay of ± 0.30 micron for 98% of the data improved to better than ± 0.25 micron, 3 sigma. These results were achieved without the use of Automatic Magnification Compensation (AVM/AMC). We.also discovered that many otherwise transparent mechanical/optical anomalies, such as contamination and scan interference, could be readily identified. Experimental data is presented and the beneficial application of this technique to a production process is discussed.

Paper Details

Date Published: 11 October 1989
PDF: 7 pages
Proc. SPIE 1138, Optical Microlithography and Metrology for Microcircuit Fabrication, (11 October 1989); doi: 10.1117/12.961746
Show Author Affiliations
Michael J. Cummings, The Perkin-Elmer Corporation (United States)
Norman Haley, Standard Microsystems Corporation (United States)
Ken Ngo, Standard Microsystems Corporation (United States)
John Schaller, Standard Microsystems Corporation (United States)

Published in SPIE Proceedings Vol. 1138:
Optical Microlithography and Metrology for Microcircuit Fabrication
Michel J. Lacombat; Stefan Wittekoek, Editor(s)

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