19 July 1989 A Statistical Approach To Automated Overlay Measurement Precision, Repeatability, And Reproducibility
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When registration requirements exceed conventional optical inspection capabilities, the need arises for a more precise method of inspection. The Perkin-Elmer OMSTM overlay measurement system has a specified precision of 0.05 micron, 3 sigma. After exposure and development, a production wafer can be quickly and precisely measured, utilizing non-destructive methods employed by the OMS instrument. After the wafers are measured, corrective inputs can be easily entered into lithographic tools to improve overlay and yield. A statistical approach to data analysis was used to establish the actual level of dynamic precision or repeatability and the reproducibility of the overlay measurement tool. For this study, X and Y distortion measurements taken on production wafers were analyzed. Wafers were printed and developed by normal production methods, using a Micralign M544 projection printer and an AEBLE 150 direct-write E-beam system. Samples from these lots were then used to establish the intra-tool repeatability by repeated measurements on 45 sites on each of three wafers for five days. Another sample was used to establish the inter-tool reproducibility by measuring 441 sites on each of two overlay measurement systems and statistically comparing the data. The results of these analyses will be presented, as well as the methodology.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Richard F. Babasick, Richard F. Babasick, Irwin Grater, Irwin Grater, } "A Statistical Approach To Automated Overlay Measurement Precision, Repeatability, And Reproducibility", Proc. SPIE 1087, Integrated Circuit Metrology, Inspection, and Process Control III, (19 July 1989); doi: 10.1117/12.953110; https://doi.org/10.1117/12.953110

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