Room-temperature ALD of metal oxide thin films by energy-enhanced ALD

Room-temperature atomic layer deposition (RT-ALD) processes are of interest for applications using temperature-sensitive substrates. Challenges with RT-ALD arise when the precursors are not sufficiently volatile, purge times become impractically long, and precursors or co-reactants are unreactive with the surface species. In several cases, the latter two challenges can be overcome using energy-enhanced ALD. Here, we demonstrate RT-ALD (25°C) processes for Al2O3, TiO2, and SiO2 from trimethylaluminum (Al(CH3)3, TMA), titanium(IV) tetraisopropoxide (Ti(OiPr)4, TTIP), and bis(diethylamino)silane (SiH2(NEt2)2, BDEAS) precursors with an O2 plasma or O3 gas as co-reactants. Saturated RT-ALD growth was obtained for all O2 plasma processes and TMA/O3, whereas the TTIP/O3 and BDEAS/O3 processes gave no growth. Using these and literature results, the criteria for viable RT-ALD processes are discussed.