Isotropic plasma-thermal atomic layer etching of aluminum nitride using SF$_6$ plasma and Al(CH$_3$)$_3$

TL;DR

This paper demonstrates isotropic plasma atomic layer etching of aluminum nitride using SF$_6$ plasma and TMA, achieving controlled etch rates and surface improvements relevant for photonics and semiconductor applications.

Contribution

It introduces a novel ALE process for AlN using SF$_6$ plasma and TMA, with detailed etch rates and surface characterization.

Findings

Maximum etch rate of 1.9 Å/cycle at 300°C

Surface oxygen concentration decreased after etching

Surface roughness reduced by approximately 35%

Abstract

We report the isotropic plasma atomic layer etching (ALE) of aluminum nitride using sequential exposures of SF$_6$ plasma and trimethylaluminum (Al(CH$_3$)$_3$, TMA). ALE was observed at temperatures greater than 200 $^\circ$C, with a maximum etch rate of 1.9 \r{A}/cycle observed at 300 $^\circ$C as measured using ex-situ ellipsometry. After ALE, the etched surface was found to contain a lower concentration of oxygen compared to the original surface and exhibited a $\sim 35$% decrease in surface roughness. These findings have relevance for applications of AlN in nonlinear photonics and wide bandgap semiconductor devices.