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 [2-3].
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.