Growth and Characterization of Ternary Hf x Ta y O z Films via Nitrogen-Infused Wet Oxidation.

Abstract

Nitrogen-infused wet oxidation at different temperatures (400–1000 °C) was employed to transform tantalum–hafnia to hafnium-doped tantalum oxide films. High-temperature wet oxidation at 1000 °C marked an onset of crystallization occurring in the film, accompanied with the formation of an interfacial oxide due to a reaction between the inward-diffusing hydroxide ions, which were dissociated from the water molecules during wet oxidation. The existence of nitrogen has assisted in controlling the interfacial oxide formation. However, high-temperature oxidation caused a tendency for the nitrogen to desorb and form N–H complex after reacting with the hydroxide ions. Besides, the presence of N–H complex implied a decrease in the passivation at the oxide–Si interface by hydrogen. As a consequence, defect formation would happen at the interface and influence the metal–oxide–semiconductor characteristics of the samples. In comparison, tantalum–hafnia subjected to nitrogen-infused wet oxidation at 600 °C has obtained the highest dielectric constant, the largest band gap, and the lowest slow trap density.