Excursion prevention and increasing device performance using mask correction for intrafield CD and Overlay improvement

Advanced process control in lithography and overall patterning is of tremendous importance for advanced semiconductor Fabs to ensure chip performance and yield. The final patterning result and thus yield depend on many process parameters such as lithography processes, exposure tool performance, etch process, CMP etc. To control these effects various knobs, e.g. on the scanner for both wafer inter- and intra-field process control have been introduced, including sophisticated in-line metrology.In this paper, we will describe how device performance can be increased by improving intra-field CDU and Overlay by Mask Tuning . Mask Tuning by the ForTune system from ZEISS uses fs laser technology to locally change the mask transmission which results in improved intra field CDU on wafer (CDC™) [1],[2],[3]. As a result the lithographic process window is increased which leads to less defects on the wafer.By applying another fs laser technique, so-called RegC [4],[5],[6], intrafield overlay can be improved respectively.Below both techniques will be briefly described. Results for the achieved improvement of the intra-field CD uniformity and overlay will be introduced. Furthermore the impact on defect density will be shown.