Atomic layer deposition of TiO 2 from tetrakis(dimethylamino)titanium and H 2 O

Abstract The atomic layer deposition (ALD) of TiO 2 from tetrakis(dimethylamino)titanium (TDMAT) and water was studied in the substrate temperature ( T S ) range of 120 °C to 330 °C. The effect of deposition temperatures on the resulting layer microstructure is investigated. Based on the experimental results, possible interaction mechanisms of TDMAT and H 2 O precursor molecules and the TiO 2 surface at different temperatures are discussed. The TiO 2 layers were characterized with respect to microstructure, composition and optical properties by glancing angle x-ray diffraction and reflectometry, x-ray fluorescence analysis, photoelectron spectroscopy and spectroscopic ellipsometry. A constant layer growth with increasing number of ALD cycles was achieved for all investigated deposition temperatures, if the inert gas purge time after the H 2 O pulse was increased from 5 s at temperatures below 250 °C to 25 s for T S ≥ 320 °C. In the investigated temperature range, the growth per cycle varies between 0.33 and 0.67 A/cycle with a minimum at 250 °C. The variations of the deposition rate are related to a change from a surface determined decomposition of TDMAT to a gas phase decomposition route above 250 °C. At the same temperature, the microstructure of the TiO 2 layers changes from amorphous to predominately crystalline, where both anatase and rutile are present.