SELECTIVE DRY ETCHING OF INGAAS AND INP OVER ALLNAS IN CH4/H2/SF6

The addition of SF6 to CH4/H2 discharges is shown to produce a significant increase in the selectivity for dry etching of both InGaAs and InP over AlInAs. The selectivity is a strong function of the dc bias on the sample during the reactive ion etching, with equirate removal of InGaAs and AlInAs for biases above 300 V. For lower bias values, the etch stop mechanism is related to the formation of Al-F and In-F species on the AlInAs surface, as evidenced by x-ray photoelectron spectroscopy. The use of SF 6 allows independent variation of the ratio of F to the other reactive species, in comparison to the use of fixed ratio gases such as C 2H4F2 or CH3F.