Hafnium oxide layers derived by photo-assisted sol–gel processing

Abstract

UV irradiation of sol–gel derived HfO 2 thin films in N 2O using excimer lamps was found to effectively remove OH groups, dissociate unreacted Hf–OH and further oxidize sol–gel layers, forming HfO 2 thin films with a high stoichiometry of 1.97. No interface oxidation and silicate formation has been observed when irradiated at 400 °C for 20 min while the films retain a desired amorphous structure. UV-irradiated sol–gel layers exhibited significantly improved optical properties, with high optical transmittances of 81–97% in the visible region of the spectrum, a high refractive index of up to 1.90 being achieved. A leakage current density as low as 5.8×10 −6 A cm −2 at 1 MV cm −2 and breakdown field of larger than 5 cm −2 were obtained on these sol–gel layers with radiation for 20 min.