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Proceedings Paper

Improving submicron CD measurements through optimum operating points
Author(s): Mircea V. Dusa; Klaus-Dieter Roeth; Christoph Jung
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Paper Abstract

Some problems encountered when measuring submicron CD patterns with white light conventional optical microscopy are presented. These are intended to support the development of a flexible software controlled new high performance optical system, allowing variation in the illumination degree of coherence, numerical aperture, threshold edge detection criteria, focus plane, giving the user opportunities to optimize the measurements. The paper will present results in measuring 0.90 to 0.65 patterns with opposite polarities in different measuring conditions from which an optimum 'operating point' can be defined considering either +/- 0.030 micrometers accuracy criteria or a +/- 0.020 micrometers reproducibility criteria. From such operating points an optimum numerical aperture and illumination aperture can be selected for a given edge detection criteria. NA selection for best resolution and accuracy is also function of the measuring plane position. For small amount of changes in focus plane, increasing the objective NA may actually decrease the quality of the image intensity profile used for measurement, resulting in decreased reproducibility. Such effects, reported also for submicron lithography imaging systems were observed. An increase in overall accuracy when focus plane is moved from the resist upper surface to the bottom resist surface (wafer surface) is observed for windows measurements.

Paper Details

Date Published: 1 March 1991
PDF: 7 pages
Proc. SPIE 1496, 10th Annual Symp on Microlithography, (1 March 1991); doi: 10.1117/12.29754
Show Author Affiliations
Mircea V. Dusa, SEEQ Technology, Inc. (United States)
Klaus-Dieter Roeth, Leica Mikroskopie und Systeme GmbH (Germany)
Christoph Jung, Leica Mikroskopie und Systeme GmbH (Germany)

Published in SPIE Proceedings Vol. 1496:
10th Annual Symp on Microlithography
James N. Wiley, Editor(s)

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