Comparison of ICl- and IBr-based plasma chemistries for inductively coupled plasma etching of GaN, InN and AlN

A parametric study of the etch characteristics of GaN, AlN and InN has been carried out with ICl/Ar and IBr/Ar chemistries in an inductively coupled plasma discharge. The etch rates of InN and AlN were relatively independent of plasma composition, while GaN showed increased etch rates with interhalogen concentration. Etch rates for all materials increased with increasing rf chuck power, indicating that higher ion bombardment energies are more efficient in enhancing sputter desorption of etch products. The etch rates increased for source powers up to 500 W and remained relatively flat thereafter for all materials, while GaN and InN showed maximum etch rates with increasing pressure. The etched GaN showed extremely smooth surfaces, which were somewhat better with IBr/Ar than with ICl/Ar. Maximum selectivities of ∼ 14 for InN over GaN and >25 for InN over AlN were obtained with both chemistries.