<i>In Vacuo</i> Studies on the Mechanism of Inherently Area-Selective Atomic Layer Deposition of Iridium

The mechanism of the area-selective atomic layer deposition process of iridium was studied. The depositions were done with iridium(III) acetylacetonate (Ir(acac)3) and O2 as precursors. The selectivity mechanism was studied with in vacuo surface analytical techniques on four surfaces: two growth surfaces of in situ deposited Al2O3 and native SiO2-terminated Si, and two nongrowth surfaces of Al2O3 and HfO2. The nongrowth surfaces and the native SiO2 contained airborne hydrocarbons from the ambient. The in situ Al2O3 surface was −OH group terminated. On the growth surfaces, ligand exchange likely occurred at the beginning of the deposition. The growth started to accelerate once the iridium on the surface was reduced from +3 to metallic, after which the O2 molecule could dissociate into reactive atomic oxygen species. The nongrowth surfaces were passivated by hydrocarbon compounds formed when Ir(acac)3 interacted with the airborne hydrocarbons on ionic metal oxides. The passivation layer did not contain iridium atoms.