Shifter slope variation effect of embedded half-tone phase-shift masks

We have examined focus behavior and process latitude of contact hole patterns on embedded half-tone phase shifting masks (HT-PSM) with simulation and experimentally measured aerial images. The results of simulation and experiment show that the shifter side-wall profile, transmittance, phase angle of shifter, and thickness affect the aerial image profile. Also, it is found that PSMs are affected by mask topography more than binary intensity masks are. AIMS (aerial image measurement system) measurements and actual experiments confirmed that shifter profiles have an effect on the best focus position, not on the focus latitude.