Optical design of hybrid-type attenuated phase-shift masks for extreme-ultraviolet lithography by use of a Fabry-Perot interference filter

We have designed what we believe to be new hybrid-type attenuated phase-shift masks for extreme-ultraviolet optical lithography by use of a Fabry-Perot interference filter. The designs for the attenuated phase-shift masks show a smaller step height for less geometric shadow effects than additive- and subtractive-type attenuated phase-shift masks, a contrast higher than 94% for both deep-ultraviolet and extreme-ultraviolet wavelength regimes, and a 180 degrees phase-shift in the extreme-ultraviolet wavelength regime. (C) 2008 Optical Society of America.