Etched multilayer mask is better than conventional absorber mask

The main problem in extreme ultra-violet (EUV) lithography for mass production is low source power. In order to overcome this problem, we suggest to use an etched multilayer mask introduced several years ago. The etched multilayer mask structure does not need an absorber stack and it was found that we could get higher aerial image slope and peak intensity than those of the conventional absorber mask structure. Also, the etched multilayer mask can reduce the pattern shift and horizontal-vertical (H-V) bias.