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 less-than-or-equal-to -150 V, and fall to less-than-or-equal-to 6 for biases of -300 V. If the dc biases are kept to less-than-or-equal-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.