16 July 2002 Overlay accuracy in 0.18-μm copper dual-damascene process
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As overlay budgets shrink with design rules, the importance of overlay metrology accuracy increases. We have investigated the overlay accuracy of a 0.18mm design rule Copper-Dual-Damascene process by comparing the overlay metrology results at the After Develop (DI) and After Etch (FI) stages. The comparisons were done on five process layers on production wafers, while ensuring that the DI and FI measurements were always done on the same wafer. In addition, we measured the in-die overlay on one of the process layers (Poly Gate) using a CD-SEM, and compared the results to the optical overlay metrology in the scribe-line. We found that a serious limitation to in-die overlay calibration was the lack of suitable structures measurable by CD-SEM. We will present quantitative results from our comparisons, as well as a recommendation for incorporating CD-SEM-measurable structures in the chip area in future reticle designs.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Bernd Schulz, Harry J. Levinson, Rolf Seltmann, Joel L. Seligson, Pavel Izikson, Anat Ronen, "Overlay accuracy in 0.18-μm copper dual-damascene process", Proc. SPIE 4689, Metrology, Inspection, and Process Control for Microlithography XVI, (16 July 2002); doi: 10.1117/12.473477; https://doi.org/10.1117/12.473477


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