Structural and dielectric characterization of atomic layer deposited HfO<inf>2</inf> and TiO<inf>2</inf> as promising gate oxides

Abstract

Tetrakis (diethylamino) hafnium (TDEAH), tetrakis (diethylamino) titanium (TDEAT) and H 2 O were used for the atomic layer deposition of HfO 2 and TiO 2 films on silicon substrates. X-ray Photoelectron Spectroscopy showed that after a short Ar+ sputtering for removing surface contaminants, both HfO 2 and TiO 2 films were found to be essentially carbon free. While HfO 2 remained at +4 chemical state after the surface sputtering, TiO 2 partially changed into Ti+3 (Ti 2 O 3 ) and Ti+2 (TiO), suggesting a preferential sputtering of O over Ti. Phase-shift interferometry (PSI) was applied to probe the surface morphology of both as-deposited and post annealed films, which were later examined by Grazing Incidence X-ray Diffraction (GIXRD). From both PSI and GIXRD results, as-deposited HfO 2 and TiO 2 films were found to be amorphous with smooth surfaces but began to crystallize with roughened surfaces after annealing at 600 °C, with HfO 2 crystallizing into a monoclinic structure and TiO 2 crystallizing into an anatase structure. C-V and I-V measurement were performed after electron beam evaporation of Al metal contacts on the dielectric layers. The calculated dielectric constant (k) value of TiO 2 is almost three times higher than that of HfO 2 and the measured leakage current densities for the metal oxides are below 10−5 A/cm2 at the applied voltage of 1 V.