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Proceedings Paper

Scatterometry-based overlay metrology
Author(s): Hsu-Ting Huang; Gayathri Raghavendra; Apo Sezginer; Kenneth Johnson; Fred E. Stanke; Michelle L. Zimmerman; Cristina Cheung; Makoto Miyagi; Bhanwar Singh
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Paper Abstract

Scatterometry provides a new, vibration-tolerant technique of overlay metrology. Gauge repeatability and reproducibility is improved by an order of magnitude over imaging-based overlay metrology. To measure the overlay of patterned layers A and B by scatterometry, one line grating is placed in layer A and another in layer B. The two gratings overlap when they are viewed in the direction that is normal to the wafer. The line gratings in layers a and b are of equal pitch and their lines are parallel. In one method, overlay is measured by fitting the optical properties of the target with spectra calculated using a model of the target and rigorous coupled wave analysis. A faster and simpler method obtains overlay by applying a linear estimator to a difference of spectra. Optical properties of targets were measured by a normal incidence spectroscopic reflectometer. Test wafers representing three overlay applications were fabricated: contact mask to shallow-trench, first metal mask to contact, and gate-mask to shallow-trench. Overlay measured by scatterometry agree with imaging-based measurements and offsets intentionally written to the reticle.

Paper Details

Date Published: 2 June 2003
PDF: 12 pages
Proc. SPIE 5038, Metrology, Inspection, and Process Control for Microlithography XVII, (2 June 2003); doi: 10.1117/12.483668
Show Author Affiliations
Hsu-Ting Huang, Therma-Wave, Inc. (United States)
Gayathri Raghavendra, Therma-Wave, Inc. (United States)
Apo Sezginer, Therma-Wave, Inc. (United States)
Kenneth Johnson, Therma-Wave, Inc. (United States)
Fred E. Stanke, Therma-Wave, Inc. (United States)
Michelle L. Zimmerman, Therma-Wave, Inc. (United States)
Cristina Cheung, Advanced Micro Devices, Inc. (United States)
Makoto Miyagi, Tokyo Electron Texas (United States)
Bhanwar Singh, Advanced Micro Devices, Inc. (United States)

Published in SPIE Proceedings Vol. 5038:
Metrology, Inspection, and Process Control for Microlithography XVII
Daniel J. Herr, Editor(s)

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