Structural, interfacial and optical characterization of ultrathin zirconia film grown by in situ thermal oxidation of sputtered metallic Zr films

Abstract

High dielectric constant ZrO2 gate dielectric thin films have been prepared by means of in situ thermal oxidation of sputtered metallic Zr films. XRD reveals that the as-oxidized samples are amorphous, but can be made polycrystalline with a highly ()-preferential orientation by increasing the annealing temperature. AFM measurements confirm that high temperature annealing results in increase of the roughness root mean square value of the films. The growth and properties of the interfacial SiO2 layer formed at the ZrO2/Si interface are observed by using Fourier transform infrared spectroscopy. It has been found that the formation of the interfacial layer depends on the post-deposition annealing temperature. On the basis of a parametrized Tauc–Lorentz dispersion model, the optical properties of the as-oxidized and annealed films related to the annealing temperature are systematically investigated by spectroscopic ellipsometry. The increase in the refractive index and decrease in extinction coefficient with increase of the annealing temperature are discussed in detail.