There are an increasing number of issues confronting lithography engineers in modern wafer fabs. Of these problems, yield loss due to reticle defects has received less attention as compared to the shrinking process window of advanced lithographic requirements. Wafer fabs also have concentrated primarily on equipment and people as major sources of yield loss. The requirement of increased focus on reticle defects is examined. The constraints of the current manufacturing capability of mask shops is driving the need for a better method to link the actual lithographic manufacturing process to the reticle defect analysis. This paper will propose a method for integrating the reticle inspection and wafer process as a method for advanced reticle disposition and specification generation. By linking the fab wafer process to the reticle defect inspection a more complete picture of the impact of having reticle defects can be assessed.
Fully automated, multi-mode CD-SEM metrology, utilizing both backscattered electron (BSE) and secondary electron (SE) detection, has been benchmarked to 180 nm 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 show that the BSE measurements are 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 2 nm 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.