Investigation of Surface Sputtering and Post Annealing Effects on Atomic Layer Deposited ${\rm HfO}_{2}$ and ${\rm TiO}_{2}$

Abstract

Tetrakis (diethylamino) hafnium and tetrakis (diethylamino) titanium were used for the atomic layer deposition (ALD) of HfO2 and TiO2 films on silicon (100) substrates with water being the oxidant. Studies on the decomposition temperatures of both metal precursors within the reactor and on carbon impurity helped determine the optimal ALD temperature range. X-ray photoelectron spectroscopy showed that after a short Ar+ sputtering to remove surface contaminants, both HfO2 and TiO2 were carbon-free when films were deposited within the optimal ALD temperature window. However, Ar+ sputtering of the surface altered the chemical state of Ti4+ and led to the formation of lower oxidation states of titanium. Optical profiling in the phase-shifting interferometry mode and grazing incidence X-ray diffraction were applied to probe the change of surface morphology and film crystallinity upon post-deposition annealing at 600°C for 5 min. Capacitance-voltage and current-voltage measurements were performed over a metal-insulator-semiconductor structure after electron beam evaporation of 150-nm-thick Al metal contacts on the dielectric layers; the calculated dielectric constant, k, of TiO2 was found to be about three times higher than that of HfO2 and the measured leakage current densities for both metal oxides were below 2 × 10-5 A/cm2 at 1-V.