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28 July 2014 Proximity corrected accurate in-die registration metrology
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193nm immersion lithography is the mainstream production technology for the 20nm and 14nm logic nodes. Multi-patterning of an increasing number of critical layers puts extreme pressure on wafer intra-field overlay, to which mask registration error is a major contributor [1]. The International Technology Roadmap for Semiconductors (ITRS [2]) requests a registration error below 4 nm for each mask of a multi-patterning set forming one layer on the wafer. For mask metrology at the 20nm and 14nm logic nodes, maintaining a precision-to-tolerance (P/T) ratio below 0.25 will be very challenging. Full characterization of mask registration errors in the active area of the die will become mandatory. It is well-known that differences in pattern density and asymmetries in the immediate neighborhood of a feature give rise to apparent shifts in position when measured by optical metrology systems, so-called optical proximity effects. These effects can easily be similar in magnitude to real mask placement errors, and uncorrected can result in mis-qualification of the mask. Metrology results from KLA-Tencor’s next generation mask metrology system are reported, applying a model-based algorithm [3] which includes corrections for proximity errors. The proximity corrected, model-based measurements are compared to standard measurements and a methodology presented that verifies the correction performance of the new algorithm.
© (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
M. Daneshpanah, F. Laske, M. Wagner, K.-D. Roeth, S. Czerkas, H. Yamaguchi, N. Fujii, S. Yoshikawa, K. Kanno, and H. Takamizawa "Proximity corrected accurate in-die registration metrology", Proc. SPIE 9256, Photomask and Next-Generation Lithography Mask Technology XXI, 92560F (28 July 2014);


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