Monolayer chemical beam etching

Abstract

We have developed an etching process with real-time counting of each monolayer removed, thus achieving etching with monolayer precision and control. This is an exact reversal of molecular beam epitaxy or more specifically in this case, chemical beam epitaxy (CBE). This new etching 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 AsCl 3 directly into a CBE growth chamber impinging on a heated GaAs substrate surface. Having both epitaxial growth and etching integrated in the same process and both capable of ultimate control down to the atomic layer precision represents a very powerful combination. This permits instant switching from growth to etching and vice versa, clean regrown interfaces critical for device applications, direct modification of surface chemistries during etching or growth, and high temperature etching (500–570°C for InP and 500–650°C for GaAs) unachievable in conventional etching processes. The temperature and flux dependence of etching 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.