Etching of Ga-based III-V semiconductors in inductively coupled Ar and CH4/H2-based plasma chemistries

We report results of a study on the inductively coupled plasma (ICP) etching of GaAs, AlGaAs, GaSb, and GaP in pure Ar, CH4/H2/Ar and CH4/H2/N2 plasma chemistries. Etch rates of the semiconductors initially increase with ICP source power, reaching maxima around 1500-2000 angstroms min-1 with approximately 500-700 W ICP power, and then decrease with further increase of ICP power because of the decrease in cathode dc self-bias. Etch rates increase at fixed ICP power with rf chuck power in the range of 100 W to 450 W, while they showed little dependence on the chamber pressure (2 reTorr-20 m Torr) in CH4/H2/Ar discharges. We found that the dc self-bias on the rf chuck decreased exponentially as ICP power increased, while it increased with rf chuck power and pressure in these plasma chemistries. A simple calculation of ion flux and etch yield based on dc self-bias of the plasmas on the sample chuck was used to measure typical values of etch yield. In both ICP CH4/H2/Ar and CH4/H2/N2 discharges these were close to the pure Ar sputter yield.