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Proceedings Paper

Electrical Method Of Determining Absolute Distortion In A 1X Wafer Stepper Independent Of Stage Precision
Author(s): Robert J. Naber
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Paper Abstract

Absolute distortion measurement in stepping metrology is critical in optimizing wafer stepper performance. The conventional reduction wafer stepper method of determining absolute distortion relies on a single reticle field of adjustable size and on a high precision stage. Data to determine distortion is collected from "box in a box" registration structures by optical or electrical measurements. This method is inappropriate, or compromising, in determining distortion of a commercial 1X wafer stepper. The 1X wafer stepper has multiple reticle fields of fixed size and achieves accurate pattern overlay thru site by site alignment without a high precision stage. The vendor of the 1X stepper has developed a method of determining absolute distortion by imaging two reticles of identical distortion on the stepper and then superimposing the image of one reticle onto the other with a known offset. The site metrology system of the stepper is used to collect data to determine distortion. This paper evaluates a new method of determining distortion of a 1X wafer stepper. The new method combines the vendor concept of superimposed reticle images with data collection and analysis techniques of electrical "box in a box" registration structures thus eliminating any stage contributions to distortion. Results presented are compared with the distortion results obtained by the vendor.

Paper Details

Date Published: 17 April 1987
PDF: 13 pages
Proc. SPIE 0775, Integrated Circuit Metrology, Inspection, & Process Control, (17 April 1987); doi: 10.1117/12.940409
Show Author Affiliations
Robert J. Naber, National Semiconductor (United States)

Published in SPIE Proceedings Vol. 0775:
Integrated Circuit Metrology, Inspection, & Process Control
Kevin M. Monahan, Editor(s)

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