In situ mass spectrometry study on atomic layer deposition from metal (Ti,Ta, and Nb) ethoxides and water

Reaction mechanisms between titanium, tantalum, and niobium ethoxides and d euterated water in the atomic layer deposition (ALD) of TiO2, Ta2O5, and Nb 2O5 were studied with a mass spectrometer. The amounts of the reaction prod uct CH3CH2OD+ (m/z = 47) and its main fragment CH2OD+ (m/z = 32) increased up to about 300 degreesC where all the metal precursors started to thermall y decompose. Despite the decomposition, significant amounts of the ligands still remained on the surface and were released in the exchange reactions w ith D2O. It was also observed that in the titanium dioxide process titanium ethoxide adsorbs on the water-treated TiO2 surface mostly without obvious exchange reactions, and over 90% of the ligands were released during the wa ter pulse. The adsorption of C2H5OH on the TiO2 surface was also examined, and it can partially explain the low amount of ligands released during the metal precursor pulses. At 325 degreesC the ALD growth of Ta2O5 and Nb2O5 c an mainly be described as an alternate release of (C2H5)(2)O during the Ta( OC2H5)(5) or Nb(OC2H5)(5) pulses and C2H5OD during the D2O pulse.