Correlation of Optical Emission and Ion Flux with GaN Etch Rate in Inductively Coupled Ar/Cl 2 Plasma Etching

Abstract

The etching of GaN was investigated in an Ar/Cl2 inductively coupled plasma. Optical emission spectroscopy and an ion flux probe were used to obtain insight into the etch mechanisms during processing. Langmuir probe measurements were also used to determine the basic Ar/Cl2 plasma characteristics. Etch rates of ≈500 nm/min were obtained at relatively low Cl2 fractions of ≈50%. The dominant emission species observed were Ga (at 294 nm) and up to six GaCl peaks between 320 and 345 nm. Plasma characterisation and ion flux indicate etch mechanisms that depend strongly on atomic chlorine but with increasing power and at low Cl2, the significance of ion-based processes cannot be ruled out.