Development of structure-property relationships in disordered Zirconia thin films for high energy density MIM capacitors

Semi-crystalline zirconium oxide 50nm-thick films were prepared by reactive RF magnetron sputtering for MIM capacitors. These dielectric films were characterized by impedance spectroscopy at frequencies ranging from 1OmHz to IMHz at temperatures up to 310°C. Annealing gold-electroded thin films at 25O0C greatly reduced the dielectric losses with little changes in crystallinity. Post annealing, space charge relaxation started to appear at 190°C. The activation energy for the relaxation was 0.84eV with a low predicted relaxation frequency (0.23nHz) at room temperature. Electrode effects dominated dielectric losses at extremely low frequencies at high temperatures. AC conductivity followed the universal behavior for the AC charge transport in amorphous materials showing that the films are highly disordered. No DC conductivity regime was observed indicating very low DC conductivity. At low electric fields (<1MV/cm), DC conductivity of the films was of the order of 10^-13 S/m, which is less than that of the high quality MOS gate oxides of comparable thickness. Thus, the disordered ZrÛ2 thin films are promising for high energy density capacitors.