Etch mechanism and etch-induced effects in the inductively coupled plasma etching of GaN

The inductively coupled plasma (ICP) processing of gallium nitride (GaN) using SF6/N2 and Cl2/Ar gas mixtures has been compared. ICP processing of GaN using SF6 and N2 mixture of 1:1 produces an optimized etch rate of 67 nm/min while five times higher etch rate of 314 nm/min is achieved using Cl2 and Ar mixture of 1:3. Etch mechanism studies indicate an ion-induced, coupled with a large chemical enhancement component for both SF6/N2 and Cl2/Ar inductively coupled plasma etching. From electrical diode characterization, an increase in electrical degradation with increasing dc bias in Cl2/Ar plasma is observed, while an improvement of diode characteristics is evident after etching in SF6/N2 plasma. X-ray photoelectron spectroscopy results indicate the presence of a significantly Ga deficient surface after etching GaN in Cl2 and Cl2/Ar plasmas. Correlation between etch mechanism and etch-induced damage results strongly indicates the existence of ion-induced chemical damage in the ICP etching of GaN in Cl2 and Cl2/Ar plasmas.