Highly selective dry etching of III nitrides using an inductively coupled Cl-2/Ar/O-2 plasma

The selective etch characteristics of GaN, AlxGa1-xN, and InxGa1-xN have be en examined in an inductively coupled plasma reactor using Cl-2/Ar/O-2 as t he etchant gas. Etch rates and selectivities were strongly influenced by th e flow rate of oxygen as well as the plasma parameters. Etch rates as high as 5500 Angstrom/min were obtained for GaN, 1850 Angstrom/min for Al0.05Ga0 .95N, 420 Angstrom/min for Al0.1Ca0.9N, and 2589 Angstrom/min for In0.12Ga0 .88N. Moreover, the etch selectivities of GaN and the In0.12Ga0.88N over th e Al0.1Ga0.9N were as high as 24 and 32, respectively. These are the highes t values ever reported for an AlGaN film with a relatively low Al compositi on (x = 0.1). An x-ray photoelectron spectroscopy analysis of the etched su rface showed that an Al-O bond was formed on the AlGaN surface during the C l-2/Ar/O-2 plasma etching and the high selectivity thus obtained could be a ttributed to the etch-resistant aluminum oxide layer. This oxide layer coul d be easily etched off by a HE-based solution during the mask removal proce ss. (C) 2000 American Vacuum Society. [S0734-211X(00)13103-8].