Effect of additive noble gases in chlorine-based inductively coupled plasma etching of GaN, InN, and AlN

The effects of additive noble gases, He, Ar and Xe to chlorine-based inductively coupled plasmas (ICPs) for etching of GaN, AlN and InN were studied in terms of etch rate and selectivity. The etch rates were greatly affected by the chlorine concentration, rf chuck power and ICP source power. The highest etch rates for InN were obtained with Cl-2/Xe, while the highest rates for AIN and GaN were obtained with Cl-2/He. It was confirmed that efficient breaking of the III-nitrogen bond is crucial for higher etch rates. The InN etching was dominated by physical sputtering; the GaN and AIN etch rates were limited by initial breaking of the III-nitrogen bond. Maximum selectivities of similar to 80 fur InN to GaN and InN to AIN were obtained with the Cl-2-based discharges. (C) 1999 American Vacuum Society. [S0734-2101(99)04603-5].