MONOLAYER CHEMICAL BEAM ETCHING

We have developed an etching process with real-time counting of each m onolayer removed, thus achieving etching with monolayer precision and control. This is an exact reversal of molecular beam epitaxy or more s pecifically in this case, chemical beam epitaxy (CBE). This new etchin g capability which we refer to as monolayer chemical beam etching (ML- CBET) is achieved by employing in-situ reflection high energy electron diffraction (RHEED) intensity oscillation monitoring during etching. Etching is accomplished in high vacuum by injecting AsCl3 directly int o a CBE growth chamber impinging on a heated GaAs substrate surface. H aving both epitaxial growth and etching integrated in the same process and both capable of ultimate control down to the atomic layer precisi on represents a very powerful combination. This permits instant switch ing from growth to etching and vice versa, clean regrown interfaces cr itical for device applications, direct modification of surface chemist ries during etching or growth, and high temperature etching (500-570-d egrees-C for InP and 500-650-degrees-C for GaAs) unachievable in conve ntional etching processes. The temperature and flux dependence of etch ing rates are also studied using RHEED oscillations. Results indicate that ML-CBET is predominantly via a layer-by-layer mechanism under the present etching conditions studied.