Proximity Effects during GeTe Area-Selective Deposition by Atomic Layer Deposition: Nanopattern Induced Thickness Profile Alteration

Abstract

Area-selective deposition (ASD) shows promise for tackling nanofabrication challenges for advanced nanoelectronic devices. Understanding the proximity effects during ASD in nanopatterns is important to ensure atomic scale precision of deposition. This work reveals and analyzes proximity effects during GeTe ASD by atomic layer deposition (ALD) with the well-known dechlorosilylation chemistry and an aminosilane inhibitor. The proximity of the TiN growth and the trimethylsilyl-terminated SiO2 nongrowth area in a line-pattern with 35 nm critical dimension leads to an altered GeTe thickness profile and a higher selectivity compared to the nonpatterned SiO2 substrate. The GeTe film on the TiN growth area shows a well-controlled, inverted U-shaped profile, different than conformal deposition typical for ALD. The ASD process in a passivated trench is mimicked using a previously developed stochastic lattice growth model, and the model results indicate that the observed edge profile is consistent with electrostatic interactions between the Te precursor’s Si­(CH3)3 ligands on the growth surface and the trimethylsilyl-groups present on the adjacent vertical passivated SiO2 nongrowth surface. The selectivity increase is attributed to diffusion-mediated migration of adspecies from the nongrowth to the growth area. We conclude that this ASD process is influenced by the proximity of growth and nongrowth surfaces by processes that go beyond the well-known self-limiting surface reactions of ALD. This work opens opportunities to tune the thickness profiles during ALD in nanopatterns beyond conformal deposition by the substrate and deposition conditions. The insights into the mechanisms of proximity effects are relevant to enable atomic-scale precision in ASD for various materials and applications in nanofabrication, including nanoelectronic device fabrication by ALD and by other deposition techniques.