Optical and electrical properties of reactively sputtered TiN, ZrN, and HfN thin films

Thin films of titanium, zirconium, and hafnium nitride are prepared by DC magnetron reactive sputtering at room temperature on fused silica, optical glass and silicon substrates. Deposition parameters are investigated in order to obtain stoichiometric films. The optical and electrical properties of the films as a function of nitrogen partial pressure are determined. The results show that an inverse correlation exists between the optical reflectance and the electrical resistivity of the films. The optical constants of the films are determined by Variable Angle Spectroscopic Ellipsometry (VASE) measurements from 240- 1700 nm at 10 nm steps. Deposited film composition is obtained by the Rutherford Ion Back Scattering (RBS) method. The rms roughness of the films is measured by using an optical scatterometer. Ellipsometer data for all three films show that their refractive index (n) in the visible spectrum is decreased by increasing the film thickness while the extinction coefficient (k) is unchanged. Thin films of TiN have the lowest room temperature resistivity (approximately equals 75 (mu) (Omega) - cm) relative to ZrN and HfN thin films.