Spectro-ellipsometric study of thin films for ULSI process - Optical properties of transition metal nitride barrier layers

摘要

Low-k materials for interlayer dielectrics and diffusion barrier layers for Cu metallization seems to be inevitable in the further ULSI process. The present report is focused on the study of transition metal nitride barrier layers especially to the spectro-ellipsometoric evaluation of these materials. The studied samples were reactively sputtered Titaniun Nitride (TiN/SiO{sub}2/Si), Tantalum Nitride (TaN{sub}x/SiO{sub}2) and Vanadium Nitride (VN/Si). VN layer and several TaN{sub}x layers with different deposition temperatures (200-400°C) were prepared optically thick. Lorentz-Drude parameterization of dielectric function of thin TiN films were determined by simultaneous fitting of ellipsometric and optical reflectivity spectra. VN and TiN optical constants show strong metallic character whereas TaN{sub}x dielectric functions depending on the substrate temperature present featureless free electron behavior for low substrate temperature.