SELECTIVE REACTIVE ION ETCHING OF INGAAS/INALAS HETEROSTRUCTURES IN HBR PLASMA

A reactive ion etching process using HBr plasma has been developed for the selective removal of InGaAs on InAlAs. Etch rates of 110 and 0.67 angstrom/min are obtained for InGaAs and InAlAs, respectively, at a plasma self-bias voltage of -100 V, a chamber pressure of 120 mTorr, and a HBr flow rate of 10 sccm. This translates to an etch selectivity of over 160 which is the highest that has been obtained for this material system. The etch stop mechanism on the InAlAs is deduced from x-ray photoelectron spectroscopy to be due to involatile Al2O3 that is formed by residual O2 and/or H2O vapor in the chamber. It is shown that the surface of the etched InAlAs can be restored to the state prior to HBr etching by sequential rinsing in dilute HCl and H2O. This process should be useful for the fabrication of InAlAs/InGaAs heterostructure field-effect transistors.