Synthesis and characterization of AlTiO films by mist-CVD

Abstract

High-k dielectric aluminum titanium oxide (AlTiO, an alloy of Al<inf>2</inf>O<inf>3</inf> and TiO<inf>2</inf>) films were obtained by mist chemical vapor deposition (mist-CVD), utilizing Al<inf>2</inf>O<inf>3</inf> and TiO<inf>2</inf> precursors. By X-ray fluorescence (XRF) investigations, atomic composition ratios of Al and Ti ratios in the Al<inf>x</inf>Ti<inf>y</inf>O films were verified. X-ray diffraction (XRD) revealed that the Al<inf>x</inf>Ti<inf>y</inf>O films deposited at 400 °C has amorphous-phase structure. It was shown that the refractive index and mass density of the Al<inf>x</inf>Ti<inf>y</inf>O films increases with increase in the Ti composition. Bandgap of the Al<inf>x</inf>Ti<inf>y</inf>O films was also estimated from X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectroscopy. It was found that the bandgap of the Al<inf>x</inf>Ti<inf>y</inf>O films decrease with increase in the Ti composition. Moreover, the obtained refractive index, mass density and bandgap of Al<inf>2</inf>O<inf>3</inf> and TiO<inf>2</inf> films are all comparable to those reported for high-quality Al<inf>2</inf>O<inf>3</inf> and TiO<inf>2</inf> films deposited by ALD, thereby demonstrating the efficacy of using mist-CVD in synthesizing films having almost the same properties as those prepared by the more mature ALD.