Benchmarking multi-mode CD-SEM metrology to 180nm

Fully automated, multi-mode CD-SEM metrology, utilizing both backscattered electron (BSE) and secondary electron (SE) detection, has been benchmarked to 180nm critical dimensions using patterns generated by deep-UV lithography. Comparison of pure BSE with conventional SE SEM data used in a study of across-chip linewidth variation (ACLV) revealed that heterogeneous system matching depends on feature orientation as well as an offset between BSE and SE intensity profiles. The corresponding AFM data showed that the BSE measurements were more accurate and less sensitive to feature orientation and sample charging. Using the multi-mode system, we found that SE profiles had a higher signal-to-noise ratio while the BSE profiles gave a better representation of the actual line shape. Static and dynamic measurement precision below 2nm has been achieved with BSE on etched polysilicon. Move-acquire-measure (MAM) times at this precision were under 10 seconds per site. Models for orientation-independent measurement, generic wafer throughput, and overall equipment effectiveness were used to address the issues of system matching, tool productivity, and factory integration, respectively.