Structural, interfacial and optical characterization of ultrathin zirconia film grown by insitu 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 ofsputtered metallic Zr films. XRD reveals that the as-oxidized samples are amorphous, butcan be made polycrystalline with a highly ()-preferential orientation by increasing the annealing temperature. AFM measurementsconfirm that high temperature annealing results in increase of the roughnessroot mean square value of the films. The growth and properties of the interfacialSiO2 layer formedat the ZrO2/Si interface are observed by using Fourier transform infrared spectroscopy. It has been foundthat the formation of the interfacial layer depends on the post-deposition annealingtemperature. On the basis of a parametrized Tauc–Lorentz dispersion model, the opticalproperties of the as-oxidized and annealed films related to the annealing temperature aresystematically investigated by spectroscopic ellipsometry. The increase in the refractiveindex and decrease in extinction coefficient with increase of the annealing temperature arediscussed in detail.