High transmission attenuated PSM - benefits and limitations through a validation study of 33%, 20% and 6% transmission masks

Simulations indicate high transmission attenuated phase shift mask to improve resolution, reduce line end shortening, corner rounding and provide process window enhancements for some pitches. They also indicate that as the transmission is increased for line features, the Normalized image log slope (NILS) increases for all pitches. In this work the performance of 33% and 20% attenuated masks has been compared against 6% and binary masks. Imaging results were obtained for 160nm features at various pitches with a 0.6NA 248nm SVGL MSIII with conventional and annular illumination. Performance of high transmission in terms of Depth of Focus, Overlapping process windows (ODOF), Exposure latitude and Proximity effects with the various % transmissions. Critical issues such as manufacturing of tri-tone masks, Inspection, Repair and material availability for High transmission (HiT) masks will be addressed.