Development of a MoSi-based bilayer HT-PSM blank for ArF lithography

Attenuated PSM (Phase Shifting Mask) is needed at an early stage of ArF lithography. For HT (Half Tone)-PSM, some materials have been introduced in recent years. We also surveyed several materials for HT-PSM blank. We think MoSiON is the best material if it can be applied to ArF lithography. Because it could be processed with the same mask processors as KrF HT-PSM could be. However we did not get practical MoSiON film for ArF lithography with our conventional DC sputtering method. So we have developed a new sputtering method to get small k (extinction coefficient) with T6% blank at 193nm wavelength. The properties of the MoSiON films obtained by this method have been evaluated, such as optical properties, chemical durability, ArF laser irradiation durability and pattern profile for feasibility. These results indicate that ULCOAT T6% bi-layer MoSiON blank is feasible for 193nm lithography.