Selective GaAs/AlxGa1−xAs reactive ion etching using CCl2F2

The reactive ion etching (RIE) of GaAs/AlxGa1−xAs heterolayers has been examined as a function of alloy composition (x=0.00–0.31) and the etching parameters of pressure, rf applied power, gas flow rate, and time using CCl2F2 as the etching gas. The information derived from this study was used to determine the GaAs to AlxGa1−xAs etch selectivities. The use of CCl2F2 promotes the formation of nonvolatile reaction products on the surface of AlxGa1−xAs, so that even for small amounts of aluminum the etch rate of AlxGa1−xAs is significantly reduced compared to GaAs. This compositional factor favors the highly selective etching of GaAs over AlxGa1−xAs. High gas pressure and flow rate and a low rf applied power also contribute to high selectivities in this system. A selectivity (GaAs to AlxGa1−xAs etch ratio) of 300 was attained for a pressure of 20 mTorr and an rf power of 500 W.