Intensity Weighed Focus Drilling Exposure for Maximizing Process Window of Sub-100nm Contact by Simulation

摘要

In our previous study, we introduced the method of intensity weighting over various image planes for FLEX (Focus Latitude Enhancement eXposure) process. By higher energy weighting on the best focus image for the approach of triple focal plane exposure, it demonstrated higher contrast over wide focus range than conventional FLEX, accordingly achieved the better performance on DoF (Depth of Focus), EL (Energy Latitude), proximity and CD uniformity. However, this technique limits the production capability by the increased number of images. Thanks for all the technology developments on RET (Resolution Enhancement Technology) with tool functionality, which is related to focus drilling method in scanner system. Hence there have been several papers addressed the focus drilling technique with high frequency illumination source recently, the focus drilling technique enables more continual image planes over focus range on advanced step and scan system while scanning the image with single uniformity energy level over various focus ranges. In this paper, the approach combining focus drilling with intensity weighting was introduced to strengthen the potential of process in step and scan system. Since the hardware for focus drilling and intensity weighting is not available in our study, we've only demonstrated the technical concepts through simulation by Prolith Ver. 9.31. To achieve the effect of intensity weighting on the focus range, we've been suggested new idea of application and applied some treatment on data from simulation tool. Simulation result on intensity weighted focus drilling achieved higher EL and DoF than the conventional focus drilling at the same focus range.