Low bias electron cyclotron resonance plasma etching of GaN, AlN, and InN

Highly anisotropic dry etching of GaN, AlN, and InN was obtained at low dc self-bias in electron cyclotron resonance Cl2/H2 or CH4/H2/Ar discharges. The Cl2/H2 chemistry produces etch rates of ∼1100 Å min−1 for AlN and ∼700 Å min−1 for GaN at −150 V and 1 mTorr for high microwave powers (1000 W), while the CH4/H2/Ar mixture etches InN at ∼350 Å min−1 at −250 V under similar conditions. The surfaces of the III-V nitrides remain stoichiometric without requiring a wet-etch cleanup. The microwave enhancement of the discharges produces these practical etch rates, the highest reported for the nitrides, while keeping the dc bias relatively low. These low pressure, low bias conditions are well suited to pattern transfer processes in device fabrication.