Spectroscopic ellipsometry characterization of ZrO2 thin films by nitrogen-assisted reactive magnetron sputtering

Spectroscopic ellipsometry (SE) with photon energy 0.75–6.5 eV at room temperature has been used to derive the optical properties of high-k ZrO2 thin films on Si(1 0 0) substrates prepared by nitrogen-assisted, direct current reactive magnetron sputtering. The Tauc–Lorentz dispersion method was adopted to model the optical dispersion functions of the thin films as a function of annealing temperature. Excellent agreement has been found between the SE fitting results and X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) results, indicating that our model adequately described the measured SE data. Optical band gaps (Eg) were also obtained based on the extracted absorption edge. Our results suggest that nitrogen-assisted process can effectively limit the interfacial layer growth in high-k oxides.