Reactive Deposition of Conformal Metal Oxide Films from Supercritical Carbon Dioxide

High-purity conformal metal oxide films were deposited onto planar and etched silicon wafers by surface-selective precursor hydrolysis in supercritical carbon dioxide using a cold wall reactor. Continuous films of cerium, hafnium, titanium, niobium, tantalum, zirconium, and bismuth oxides between 21 and 263 nm thick were grown at temperatures between 250 and 300 °C using CO 2 soluble precursors. The as-deposited films were pure single-phase oxide in the cases of HfO 2, ZrO 2, and TiO 2 and composed of oxides of mixed oxidation states in the cases of cerium, tantalum, niobium, and bismuth oxides as determined by XPS. As-deposited films typically contained 5% carbon or less. Carbon contamination was eliminated in all cases by annealing at 400 °C. The films were characterized by XPS, profilometry, SEM, XRD, and AFM.