Physical properties of high pressure reactively sputtered hafnium oxide

Hafnium oxide films were deposited on silicon by High Pressure Reactive Sputtering (HPRS) at pressures between 0.8 and 1.6 mbar. Growth, composition and morphology were investigated using Transmission Electron Microscopy (TEM), Heavy Ion Elastic Recoil Detection Analysis (HI-ERDA), Fourier Transform Infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD). The growth rate was found to decrease exponentially with deposition pressure. The films showed a monoclinic polycrystalline structure, with higher grain size for intermediate pressures. All the films were slightly oxygen rich with respect to stoichiometric HfO2, which is attributed to the oxygen plasma. Additionally, it was observed the formation of an interfacial silicon oxide layer, with a minimum thickness for deposition pressures around 1.2 mbar. These results are explained by the oxidation action of the oxygen plasma and the diffusion of oxygen through the grain boundaries of the HfO2 film.