Sustained Area-Selectivity in Atomic Layer Deposition of Ir Films: Utilization of Dual Effects of O₃ in Deposition and Etching

Area-selective deposition (ASD) based on self-aligned technology has emerged as a promising solution for resolving misalignment issues during ultrafine patterning processes. Despite its potential, the problems of area-selectivity losing beyond a certain thickness remain critical in ASD applications. This study reports a novel approach to sustain the area-selectivity of Ir films as the thickness increases. Ir films are deposited on Al₂O₃ as the growth area and SiO₂ as the non-growth area using atomic-layer-deposition with tricarbonyl-(1,2,3-η)-1,2,3-tri(tert-butyl)-cyclopropenyl-iridium and O₃. O₃ exhibits a dual effect, facilitating both deposition and etching. In the steady-state growth regime, O₃ solely contributes to deposition, whereas in the initial growth stages, longer exposure to O₃ etches the initially formed isolated Ir nuclei through the formation of volatile IrO₃. Importantly, longer O₃ exposure is required for the initial etching on the growth area(Al₂O₃) compared to the non-growth area(SiO₂). By controlling the O₃ injection time, the area selectivity is sustained even above a thickness of 25 nm by suppressing nucleation on the non-growth area. These findings shed light on the fundamental mechanisms of ASD using O₃ and offer a promising avenue for advancing thin-film technologies. Furthermore, this approach holds promise for extending ASD to other metals susceptible to forming volatile species.