Alumina thin films prepared by direct liquid injection chemical vapor deposition of dimethylaluminum isopropoxide: a process-structure investigation

The development of a new process to obtain amorphous alumina thin films is presented. We show for the first time the direct liquid injection chemical vapor deposition (DLI CVD) of alumina thin films using dimethylaluminum isopropoxide (DMAI) precursor in two oxidizing atmospheres. At high process temperature (500-700 degrees C), the film growth takes place in the presence of O-2 whereas at low temperature (150-300 degrees C) H2O vapor is used. The materials characteristics, such as the surface morphology and roughness (SEM and AFM), crystal structure (XRD), composition (EPMA) and chemistry (XPS) are discussed in detail. Very smooth films, with typical roughness values lower than 2.0 nm are obtained. The thin films are all composed of an amorphous material with varying composition. Supported by both EPMA and XPS results, film composition evolves from a partial oxyhydroxide to a stoichiometric oxide at low deposition temperature (150-300 degrees C) in the presence of H2O. At higher growth temperature (500-700 degrees C) in the presence of O-2, the composition changes from that of a stoichiometric oxide to a mixture of an oxide with aluminum carbide. Elemental composition of the alumina films deposited in the presence of H2O from 150 to 300 degrees C (circles), in the presence of O-2 from 500 to 700 degrees C (diamonds) or in the presence of N-2 only at 600 degrees C (squares). O/Al ratios and C concentrations are shown. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim