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Proceedings Paper

Reduction of image-based ADI-to-AEI overlay inconsistency with improved algorithm
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Paper Abstract

In image-based overlay (IBO) measurement, the measurement quality of various measurement spectra can be judged by quality indicators and also the ADI-to-AEI similarity to determine the optimum light spectrum. However we found some IBO measured results showing erroneous indication of wafer expansion from the difference between the ADI and the AEI maps, even after their measurement spectra were optimized. To reduce this inconsistency, an improved image calculation algorithm is proposed in this paper. Different gray levels composed of inner- and outer-box contours are extracted to calculate their ADI overlay errors. The symmetry of intensity distribution at the thresholds dictated by a range of gray levels is used to determine the particular gray level that can minimize the ADI-to-AEI overlay inconsistency. After this improvement, the ADI is more similar to AEI with less expansion difference. The same wafer was also checked by the diffraction-based overlay (DBO) tool to verify that there is no physical wafer expansion. When there is actual wafer expansion induced by large internal stress, both the IBO and the DBO measurements indicate similar expansion results. The scanning white-light interference microscope was used to check the variation of wafer warpage during the ADI and AEI stages. It predicts a similar trend with the overlay difference map, confirming the internal stress.

Paper Details

Date Published: 18 April 2013
PDF: 6 pages
Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 86812P (18 April 2013); doi: 10.1117/12.2010570
Show Author Affiliations
Yen-Liang Chen, Taiwan Semiconductor Manufacturing Co. Ltd. (Taiwan)
Shu-Hong Lin, Taiwan Semiconductor Manufacturing Co. Ltd. (Taiwan)
Kai-Hsiung Chen, Taiwan Semiconductor Manufacturing Co. Ltd. (Taiwan)
Chih-Ming Ke, Taiwan Semiconductor Manufacturing Co. Ltd. (Taiwan)
Tsai-Sheng Gau, Taiwan Semiconductor Manufacturing Co. Ltd. (Taiwan)


Published in SPIE Proceedings Vol. 8681:
Metrology, Inspection, and Process Control for Microlithography XXVII
Alexander Starikov; Jason P. Cain, Editor(s)

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