Selective dry etching of the GaN/InN/AlN, GaAs/AlGaAs and GaAs/InGaP systems

Selective etching' of InN over GaN and AIN, and of GaAs over both AlGaAs and InGaP was examined with a number of different plasma chemistries under inductively coupled plasma conditions. Selectivities up to 55 for InN/GaN and 20 for InN/AlN were achieved in ICI/Ar discharges. For GaAs/AlGaAs, maximum selectivities of 75(with BCl3/SF6) were obtained while for GaAs/InGaP values of 80(with BCl3/SF6) and 25(with BCl3/NF3) were achieved. Selective etching of InGaP over GaAs is possible with either CH4/H-2 or BI3. The selectivity is a strong function of ion flux and ion energy, and can result from two factors - either formation of a nonvolatile etch product, or a difference in bond strength between the two materials.