Oxidation Dynamics and Surface Chemistry of Iridium and Iridium Oxide Films Grown by Atomic Layer Deposition Using O2 and O3

Abstract

Atomic layer deposition of Ir and IrO2 is demonstrated using O2 and O3 with various exposure conditions as reactants. The nucleation density of Ir increases with the oxidation potential of the reactants, leading to the formation of continuous and conductive films at lower thicknesses. A higher oxidation potential improves the continuity and crystallinity of the Ir films, resulting in a decrease in their resistivity. O2-based processes result in Ir metal films regardless of O2 exposure time due to low oxidation potential. Conversely, in O3-based processes, deposited Ir is oxidized into IrO2 with prolonged exposure time due to higher oxidation potential of O3. The resistivity of IrO2 films decrease with increasing oxidation potential due to higher purity, resulting from facilitated oxidation. Additionally, the formation of surface OH groups is observed and increased with O3 exposure time or pressure, causing a decrease in precursor adsorption efficiency and thus suppression of the film deposition. A model explaining growth behavior of Ir and IrO2 films, regarding oxidation potential and exposure time of reactant, is proposed.