Etching characteristics of GaN by plasma chemical vaporization machining

A high‐quality bulk gallium nitride (GaN) substrate, which is suitable for high‐quality homoepitaxial growth, is indispensable for realizing high‐performance GaN devices. With improvement in the quality of the bulk GaN substrate, the removal of subsurface damage induced during surface polishing has become increasingly necessary. To remove the subsurface damage from the bulk GaN substrate, a chemical finishing method that does not produce further damage is required. We applied plasma chemical vaporization machining (CVM) to remove the subsurface damage from the bulk GaN substrate. In this study, we investigated the etching characteristics of GaN by plasma CVM applying atmospheric pressure Cl₂/He plasma. The maximum removal rate in the depth direction by plasma CVM was 9100 nm/min, which is seven times greater than that of reactive ion etching (RIE). The activation energy in plasma CVM was estimated to be 2.1 kcal/mol, which is 1.75 times greater than that in RIE. It is supposed that some of the energy required for the removal reaction in RIE is supplied by ion bombardment, but plasma CVM depends on only a chemical reaction without high‐energy ion collision. This result suggests that plasma CVM is a finishing method that causes less subsurface damage than RIE. Copyright © 2008 John Wiley & Sons, Ltd.