Photomask repair performance of the SiON/Ta-Hf attenuating PSM

Recently, a new attenuating phase shift film utilizing a bilayer of SiON film and TaHf alloy film was developed for F 2 and high transmission ArF lithography. Basic data, showing their optical properties, chemical durability, and dry-etch performance was introduced during the Photomask Japan 2003. Currently a lot of lithographers are paying their attention on this new material, because of its capability for high transmission ArF, as one of the solution for 65nm node with 193nm extension. As it is becoming more and more recognized by both mask manufacturers and mask users, repair capability of the film material has a great impact on the mask yield, which determines the potential cost and cycle time of the photomask. In this paper, we investigated the capability of this material on critical mask repair, focusing on high transmission and attenuating ternary PSM. We evaluated the repair capability with currently used FIB tools. This new material shows excellent repair capability because of the bilayer structure, where the Ta-Hf film, which was initially designed as a transmission control layer and as an etch stop for the SiON etch, works as a stopper during the FIB repair process assisted by β gas. We also report preliminary test results with the nanomachining repair system RAVE.