Topographical selective deposition: A comparison between plasma-enhanced atomic layer deposition/sputtering and plasma-enhanced atomic layer deposition/quasi-atomic layer etching approaches

In this work, we focus on the development of topographically selective deposition (TSD) leading to local deposition on the vertical sidewalls of 3D structures. A proof of concept is provided for the TSD of Ta2O5. The TSD process relies on plasma-enhanced atomic layer deposition (PEALD) alternating with quasi-atomic layer etching (ALE). Quasi-ALE involves a fluorination treatment followed by a directional Ar+ sputtering step. We show that the fluorination treatment allows a significant decrease in the incident kinetic energy of the subsequent directional Ar+ sputtering step. Conversely, when no fluorination step is carried out, TSD requires high incident kinetic energies during the directional Ar+ sputtering step, which, in turn, leads to detrimental plasma-induced damage on horizontal surfaces, such as roughness, also promoting by-product redeposition. The benefits and shortcomings of these two TSD approaches-PEALD/quasi-ALE and PEALD/energetic Ar+ sputtering-are compared in light of potential bottom-up technological developments.