Atomic layer etching of GaN using Cl2 and He or Ar plasma

During the fabrication of a MOS-HEMT, the plasma-etching steps are critical because they can damage the GaN materials and lead to electrical degradation effects. In this paper, we propose to evaluate GaN etching performances through comparing the Cl2-based atomic layer etching (ALE) process with He or Ar as the sputtering gas. The self-limiting synergy and process window of ALE has been investigated. Based on these results, we propose the reasons for the nonself-limiting behavior of the He ALE process. Both ALE processes were compared to a steady-state process by investigating roughness, and electrical measurements, in order to evaluate the induced damage.