A Study on Optimization of Alternating Phase Shifting Mask Structure

摘要

Many studies have reported that the alternating phase shift mask (Alt. PSM) improves resolution and depth of focus (DOF). The purpose of this study is to investigate the influence of process latitude and optimize undercut and pre etch depth of both single trench and dual trench process employing the Solid-CM~(TM) simulation tool for 248 run DUV lithography system. To compensate for the unbalance intensity, we adopted the amount of undercut in the phase shifter regions of both single trench and dual trench. The results suggest that process is improved with optimized undercut for 130 nm line & space (L/S). For the single trench, we can see that with undercut of about 800 A the max intensites are equal. In the case of dual trench, the margins for image balance of 800 A and 1600 A undercuts was obtained up to 800 A, 1200 A of pre etch depth, respectively. Finally, it was found that the effect of undercut was improving the process latitude and the balance intensity of both single trench and dual trench.