Repeated measurements of the same structure at separate locations are used to extract SEM contours across several instances. The average measurements from these locations can then be used for OPC model calibration. Using 14nm process data, it is shown that including more contours in hybrid OPC model calibration leads to improved model verification. Within an appropriate range, higher weight on the contour patterns leads to improved model verification on measurement sites unseen by the calibration set. Calibrating a model with fewer contour structures, but at higher weight shows improvement over standard CD only model calibration.
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Marshal Miller, Keiichiro Hitomi, Scott Halle, Ioana Graur, Todd Bailey, "Application of SEM-based contours for OPC model weighting and sample plan reduction," Proc. SPIE 9426, Optical Microlithography XXVIII, 94260Y (31 March 2015);