Optical properties of TaTe2O7 thin films as absorber materials for extreme ultraviolet lithography binary masks

摘要

In this study, the authors propose tantalum-tellurium oxide (TaTe2O7) as a new mask material for extreme ultraviolet lithography (EUVL). TaTe2O7 films were deposited by using the RF magnetron sputtering method. The optical constants of the TaTe2O7 film were calculated as n = 0.9529 and k = 0.05548 at a wavelength of 13.5 nm by using an indirect optical method. The reflectance spectra for the deposited TaTe2O7 film on a (Mo/Si) multilayer mirror were measured in the EUV region and also simulated by using the optical constants. The simulated reflectance spectra show that the minimum reflectance of 0.2% required for a EUVL mask absorber material is attained at 44.14 nm thickness for the TaTe2O7 film and 37.05 nm for the bulk TaTe2O7. The measured reflectance for the TaTe2O7 films of various thicknesses (4.88, 13.12, 22.5, 41.18, and 54.47 nm) agreed relatively well with the simulated results.