Structural and Dielectric Characterization of Atomic Layer Deposited HfO2 and TiO2 as Promising Gate Oxides

Tetrakis (diethylamino) hafnium (TDEAH), tetrakis (diethylamino) titanium (TDEAT) and H2O were used for the atomic layer deposition of HfO2 and TiO2 films on silicon substrates. X-ray Photoelectron Spectroscopy showed that after a short Ar+ sputtering for removing surface contaminants, both HfO2 and TiO2 films were found to be essentially carbon free. While HfO2 remained at +4 chemical state after the surface sputtering, TiO2 partially changed into Ti+3 (Ti2O3) 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 HfO2 and TiO2 films were found to be amorphous with smooth surfaces but began to crystallize with roughened surfaces after annealing at 600 degrees C, with HfO2 crystallizing into a monoclinic structure and TiO2 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 TiO2 is almost three times higher than that of HfO2 and the measured leakage current densities for the metal oxides are below 10-5 A/cm(2) at the applied voltage of 1 V.