Atomic Layer Deposition, Characterization, And Growth Mechanistic Studies Of Tio2 Thin Films

Two heteroleptic titanium precursors were investigated for the atomic layer deposition (ALD) of titanium dioxide using ozone as the oxygen source. The precursors, titanium (N,N'-diisopropylacetamidinate)-tris(isopropoxide) (Ti((OPr)-Pr-i)(3)((NPr)-Pr-i-Me-amd)) and titanium bis-(dimethylamide)bis(isopropoxide) (Ti(NMe2)(2)(OiPr)(2)), exhibit self-limit-ing growth behavior up to a maximum temperature of 325 degrees C. Ti(NMe2)(2)((OPr)-Pr-i)(2) displays an excellent growth rate of 0.9 angstrom/cycle at 325 degrees C while the growth rate of (Ti((OPr)-Pr-i)(3)((NPr)-Pr-i-Me-amd) is 0.3 angstrom/cycle at at the same temperature. In the temperature range of 275-325 degrees C, both precursors deposit titanium dioxide in the anatase phase. In the case of Ti(NMe2)(2)((OPr)-Pr-i)(2), high-temperature X-ray diffraction (HTXRD) studies reveal a thickness-dependent phase change from anatase to rutile at 875-975 degrees C. X-ray photoelectron spectroscopy (XPS) indicates that the films have high purity and are close to the stoichiometric composition. Reaction mechanisms taking place during the ALD process were studied in situ with quadrupole mass spectrometry (QMS) and quartz crystal microbalance (QCM).