High-density plasma etch selectivity for the III–V nitrides

Abstract

High-density plasma etching has been an effective patterning technique for the group-III nitrides due to ion fluxes which are 2–4 orders of magnitude higher than more conventional reactive ion etch (RIE) systems. GaN etch rates exceeding 0.68 μm/min have been reported in Cl 2/H 2/Ar inductively coupled plasmas (ICP) at −280 V dc-bias. Under these conditions, the etch mechanism is dominated by ion bombardment energies which can induce damage and minimize etch selectivity. High selectivity etch processes are often necessary for heterostructure devices which are becoming more prominent as growth techniques improve. In this study, we will report high-density ICP etch rates and selectivities for GaN, AlN, and InN as a function of plasma chemistry, cathode rf-power, ICP-source power, and chamber pressure. GaN:AlN selectivities >8:1 were observed in a Cl 2/Ar plasma at 10 mTorr pressure, 500 W ICP-source power, and 130 W cathode rf-power, while the GaN:InN selectivity was optimized at ∼6.5:1 at 5 mTorr, 500 W ICP-source power, and 130 W cathode rf-power.