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Proceedings Paper

Advanced diffraction-based overlay for double patterning
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Paper Abstract

Diffraction based overlay (DBO) technologies have been developed to address the tighter overlay control challenges as the dimensions of integrated circuit continue to shrink. Several studies published recently have demonstrated that the performance of DBO technologies has the potential to meet the overlay metrology budget for 22nm technology node. However, several hurdles must be cleared before DBO can be used in production. One of the major hurdles is that most DBO technologies require specially designed targets that consist of multiple measurement pads, which consume too much space and increase measurement time. A more advanced spectroscopic ellipsometry (SE) technology-Mueller Matrix SE (MM-SE) is developed to address the challenge. We use a double patterning sample to demonstrate the potential of MM-SE as a DBO candidate. Sample matrix (the matrix that describes the effects of the sample on the incident optical beam) obtained from MM-SE contains up to 16 elements. We show that the Mueller elements from the off-diagonal 2x2 blocks respond to overlay linearly and are zero when overlay errors are absent. This superior property enables empirical DBO (eDBO) using two pads per direction. Furthermore, the rich information in Mueller matrix and its direct response to overlay make it feasible to extract overlay errors from only one pad per direction using modeling approach (mDBO). We here present the Mueller overlay results using both eDBO and mDBO and compare the results with image-based overlay (IBO) and CD-SEM results. We also report the tool induced shifts (TIS) and dynamic repeatability.

Paper Details

Date Published: 1 April 2010
PDF: 10 pages
Proc. SPIE 7638, Metrology, Inspection, and Process Control for Microlithography XXIV, 76382C (1 April 2010); doi: 10.1117/12.848516
Show Author Affiliations
Jie Li, Nanometrics Inc. (United States)
Yongdong Liu, Nanometrics Inc. (United States)
Prasad Dasari, Nanometrics Inc. (United States)
Jiangtao Hu, Nanometrics Inc. (United States)
Nigel Smith, Nanometrics Inc. (United States)
Oleg Kritsun, GLOBALFOUNDRIES Inc. (United States)
Catherine Volkman, GLOBALFOUNDRIES Inc. (United States)


Published in SPIE Proceedings Vol. 7638:
Metrology, Inspection, and Process Control for Microlithography XXIV
Christopher J. Raymond, Editor(s)

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