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.

Nucleation and Layer Closure Behavior of Iridium Films Grown Using Atomic Layer Deposition.

Understanding the initial growth process during atomic layer deposition (ALD) is essential for various applications employing ultrathin films. This study investigated the initial growth of ALD Ir films using tricarbonyl-(1,2,3-η)-1,2,3-tri(tert-butyl)-cyclopropenyl-iridium and O2. Isolated Ir nanoparticles were formed on the oxide surfaces during the initial growth stage, and their density and size were significantly influenced by the growth temperature and substrate surface, which strongly affected the precursor adsorption and surface diffusion of the adatoms. Higher-density and smaller nanoparticles were formed at high temperatures and on the Al2O3 surface, forming a continuous Ir film with a smaller thickness, resulting in a very smooth surface. These findings suggest that the initial growth behavior of the Ir films affects their surface roughness and continuity and that a comprehensive understanding of this behavior is necessary for the formation of continuous ultrathin metal films.