A study of 193-nm immersion lithography using novel high refractive index fluids

In search for the next 193-nm immersion lithography fluid, research and development continue to focus on low absorbance fluids with a refractive index n higher than 1.6. In this paper, the properties of a newly developed high refractive index fluid of low absorption coefficient named ‘Delphi’ will be discussed. The refractive index of ‘Delphi’ at 193.39 nm was 1.63 and absorption coefficient was 0.08/cm as evaluated using a spectroscopic ellipsometer. Thirty two nanometer lines and spaces patterns imaging of excellent rectangular profiles were achieved with this fluid using a 193-nm two-beam interferometric exposure tool. The physical characteristics of ‘Delphi’ were also proven as feasible for application with possible future 193-nm high refractive index immersion lithography systems.