Optical properties of non-stoichiometric sputtered zirconium nitride films

Non-stoichiometric dc magnetron-sputtered ZrN films on silicon have been optically and electrically characterized through spectral reflectance measurements and a four-probe method, respectively. The deposition of the films was monitored by the nitrogen gas flow which has been increased from 1 to 11 sccm. Experimental results show that the reflectivity as well as the electrical resistivity strongly depends on the nitrogen concentration. In order to determine the optical constants of the various ZrN layers, Drude’s model was used to fit the reflectance spectra of the films with a metallic behavior, and an extended model for the films with a more insulating behavior. The optical resistivity for the frequency ω=0 was derived from the optical constants and compared to the electrical resistivity obtained by the four-probe method. A good agreement between electrical and optical resistivities was obtained.