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Proceedings Paper

Overlay measurement accuracy verification using CD-SEM and application to the quantification of WIS caused by BARC
Author(s): Laurent Lecarpentier; Vincent Vachellerie; Elyakim Kassel; Yosef Avrahamov; Chin-Chou K. Huang; Frank Felten; Marco Polli; Aurelien Feneyrou; Philippe Thony; Stephane Guillot
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Paper Abstract

As Moore's law drives the semiconductor industry to tighter specifications, challenges are becoming real for overlay metrology. A lot of work has been done on the metrology tool capability to improve single-tool precision, tool-to-tool matching and Tool-Induced Shift (TIS) variability. But nowadays these contribute just a small portion of the Overlay Metrology Error (approximately 10% for 90nm technology). Unmodeled systematic, scanner noise and process variation are becoming the major contributors. In order to reduce these effects, new target design was developed in the industry, showing improvements in performance. Precision, Residual analysis, DI/FI (Develop Inspection / Final Inspection) bias and Overlay Mark Fidelity (OMF) are common metrics for measurement quality. When we come to measurement accuracy, we do not have any direct metric to qualify targets. In the current work we evaluated the accuracy of different AIM (developed by Kla-Tencor) and Frame-In-Frame (FIF) targets by comparing them to reference “SEM” targets. The experiment was conducted using a special designed 65nm D/R reticle, which included various overlay targets. Measurements were done on test wafers with resist on etched poly printed on 248nm scanner. The results showed that, for this "straight-forward" application, the best accuracy performance was achieved by the Non Segmented (NS) AIM target and was estimated in the order of 1.5 nm site-to-site. This is slightly more accurate than hole-based target and far more than NS FIF target in this particular case. When using the non-accurate NS FIF target, correctable parameters and maximum overlay prediction error analysis, showed up to 24nm overlay error at the edge of the wafer. We also showed that part of this accuracy error can be attributed to the non-uniformity of BARC deposition.

Paper Details

Date Published: 10 May 2005
PDF: 11 pages
Proc. SPIE 5752, Metrology, Inspection, and Process Control for Microlithography XIX, (10 May 2005); doi: 10.1117/12.610662
Show Author Affiliations
Laurent Lecarpentier, STMicroelectronics (France)
Vincent Vachellerie, STMicroelectronics (France)
Elyakim Kassel, KLA-Tencor Corp. (United States)
Yosef Avrahamov, KLA-Tencor Corp. (United States)
Chin-Chou K. Huang, KLA-Tencor Corp. (United States)
Frank Felten, KLA-Tencor Corp. (United States)
Marco Polli, KLA-Tencor Corp. (United States)
Aurelien Feneyrou, STMicroelectronics (France)
Philippe Thony, CEA-LETI (France)
Stephane Guillot, STMicroelectronics (France)

Published in SPIE Proceedings Vol. 5752:
Metrology, Inspection, and Process Control for Microlithography XIX
Richard M. Silver, Editor(s)

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