High rate electron cyclotron resonance etching of GaN, InN, and AlN

Electron cyclotron resonance etch rates of GaN, InN, and AlN are reported as a function of pressure, microwave power, and radio‐frequency (rf) power in a Cl2/H2/CH4/Ar plasma at 170 °C. The etch rates for GaN and InN increase as a function of rf power. At 275 W, the etch rates reach maximum values of 2850 and 3840 A/min, respectively. These are the highest etch rates reported for these materials. As a function of pressure, the etch rates reach a maximum value at 2 mTorr and then decrease as the pressure is increased to 10 mTorr. The GaN and AlN etch rates increase less than a factor of 2 as the microwave power is increased from 125 to 850 W whereas the InN etch rate increases by more than a factor of 3.5. The maximum etch rate for AlN obtained in this study is 1245 A/min at a microwave power of 850 W, 1 mTorr pressure, and 225 W rf power. Atomic force microscopy is used to determine root‐mean‐square roughness as a function of etch conditions for GaN and InN and, while very smooth pattern transfer can be o...