(Invited) Vacuum Ultraviolet Photochemical Atomic Layer Deposition of Alumina and Titania Films

Abstract

Conventional atomic layer deposition (ALD) is a thermo-chemical process where co-reagents are sequentially pulsed in cycles onto a heated substrate. As an alternative to substrate heating, various forms of other “non-thermal” ALD processes are being investigated. Herein, the photochemical atomic layer deposition of Al2O3 and TiO2 thin films at 60°C is reported using a shuttered vacuum ultraviolet light source to excite molecular oxygen as a co-reagent with the metal precursors. The growth mechanisms using trimethyl aluminium and titanium tetraisopropoxide precursors, are investigated using in-situ quartz crystal microbalance and post-deposition ellipsometric measurements. The photochemical ALD Al2O3 films exhibit different capacitance equivalent thicknesses for irradiated and masked regions respectively, even after post-deposition annealing. The photochemical ALD titania films are amorphous and when incorporated into Pt / TiO2 / Pt metal - insulator - metal structures, the titania exhibits a resistive switching behavior.