Defect inspection and printability of deep-UV halftone phase-shifting mask

As feature size goes down to a quarter micron, halftone phase- shifting mask (HT PSM) has been studied to extend photo lithography capabilities especially in contact hole patterns. However, defect problem of HT PSM is more serous than that of conventional chrome mask because of added reticle fabrication process steps in which unexpected defects can be generated. In this paper, test HT PSMs which have different transmittance at 488 nm and same background contact patterns with programmed defects having various types are investigated for 250 nm contact hole patterns. The programmed defect are used for the sensitivity evaluation of reticle inspection systems, i.e. detectability and exposed by 4X reduction DUV exposure tool to determine printability and water defect detectability. Direct reticle inspection results show that the detectability depends on transmittance at the inspection wavelength 488 nm. The printability from the wafer exposure results is proportional to defect area strongly. Indirect reticle inspection results using an imaged wafer and wafer inspection tool of SEMSpec show that direct reticle inspection is better than indirect inspection.