Improving 1D optical proximity effect matching for 45-nm node by scatterometry metrology

The fingerprint of the optical proximity effect, OPE, is required to develop each process node's optical proximity correction (OPC) model. This model should work equally well on different exposure systems. However, small differences in optical and mechanical properties in the lithographic system can lead to a different CD characteristic for a given OPC. It becomes beneficial to match the OPE of one scanner to the scanner population in a fab. Here, we focus on aspects of angle resolving scatterometry metrology used for OPE matching of two XT:1700i scanners and compare those to SEM metrology. The capability of the scatterometry tool for monitoring the stability of OPE is evaluated. Scatterometry allows measuring the side wall angle, SWA, of a resist profile and this can be used as a measure for focus. Here, focus comparison by SWA is included into the matching process. For the application used here, the residual RMS mismatch through pitch for scatterometry could be reduced to 0.2nm compared to 0.5nm for CD-SEM.