Optical image enhancement effect in 35 nm isolated pattern replication using diamond x-ray phase shift mask

Recently, technical driver for semiconductor devices is changed from DRAM to MPU, where smaller gate pattern is required. In x-ray lithography, Yang et al. have proposed an optical image enhancement technique, which enables the isolated pattern size in the x-ray mask to shrink until 1/5 times on a wafer. In this technique, /spl pi/ phase shift x-ray mask consisted of SiN was used. In this work, we propose /spl pi/ phase shift x-ray mask consisted of diamond and W. We have investigated on applicability of /spl pi/ phase shift x-ray mask for x-ray wavelength shorter than 7 /spl Aring/, and supposed that it is possible to reduce the shifter thickness resulting in /spl pi/ phase shift by the combination of diamond and W materials, because they have larger phase shift angles than SiN. We also discuss the pattern size variations for 35 nm isolated pattern with respect to phase shifter thickness and mask pattern size variations.