INVESTIGATION INTO EXCIMER-LASER RADIATION-DAMAGE OF DEEP-ULTRAVIOLETOPTICAL-PHASE MASKING FILMS

A variety of materials based on various oxides, nitrides, fluorides, a nd composites have been found to be potentially suitable for use as at tenuated phase masking materials for use at excimer laser wavelengths. Presented here are results from the investigation into 193 nm excimer laser radiation of zirconium-nitride-based, aluminum-nitride-based, c hrome-fluoride, amorphous-carbon, and tantalum-silicon-nitride (TaN/Si 3N4) attenuated phase-shift mask materials at fluence levels mask mate rials experience during wafer exposure. Spectroscopic photometric and ellipsometric methods were utilized to quantify damage through measure ment of transmission and reflection properties and extraction of optic al constants. Results show that understoichiometric zirconium-and alum inum-nitride materials are susceptible to radiation-induced modificati on through oxidation effects while tantalum-silicon-nitride and chrome -fluoride films are able to withstand exposure to several thousand J/c m(2) without significant degradation. (C) 1997 American Vacuum Society .