Atomic layer deposition of titanium dioxide from TiCl4 and H2O: investigation of growth mechanism

Atomic layer deposition (ALD) of titanium dioxide from TiCl4 and H2O was st udied at substrate temperatures of 100-400 degreesC. Using a real-time quar tz crystal microbalance method, it was demonstrated that although the surfa ce reactions were self-limited, the growth rate depended on the temperature and development of the thin film structure. Relatively low growth rate whi ch was obtained in the TiCl4/H2O ALD process, was found to be a result of a significant chlorine amount adsorbed during the TiCl4 pulse. Surface inter mediates formed in the initial stage of TiCl4 adsorption were unstable and weakly bonded to the surface. Desorption and decomposition of these species additionally influenced the deposition late and, especially, its dependenc e on the precursor pulse times. (C) 2001 Elsevier Science B.V. All rights r eserved.