Analysis of focus errors in lithography using phase-shift monitors

We present here a procedure to characterize focus behavior on a first generation prototype 193-nm scanner using phase-shift focus monitors, which clearly identifies the influence of full field dynamic effects and that of the wafer topography and flatness. These results are used to correct the systematic errors due to incorrect tool set-up and show that proposed procedure has capability to identify focus errors and on this basis to construct a focus budget for all components: reticle, wafer, tool. We also present results using a new focus monitor based on phase gratings, which is more sensitive than the traditional phase-shift focus monitor.