Dry etching characteristics of III–V semiconductors in microwave BCl3 discharges

Electron cyclotron resonance (ECR) BCl3 discharges with additional rf biasing of the sample position have been used to etch a variety of III–V semiconductors. GaAs and AlxGa1−xAs (x = 0−1) etch at equal rates in BCl3 or BCl3/Ar discharges, whereas SF6 addition produces high selectivities for etching GaAs over AlGaAs. These selectivities are in excess of 600 for dc biases of ≤−150 V, and fall to ≤6 for biases of −300 V. If the dc biases are kept to ≤ − 100 V, there is no measurable degradation of the optical properties of the GaAs and AlGaAs. The AlF3 formed on the AlGaAs surface during exposure to BCl3/SF6 plasmas can be removed by sequential rinsing in dilute NH4OH and water. In-based materials (InP, InAs, InSb, InGaAs) etch at slow rates with relatively rough morphologies in BCl3 plasmas.