DRY-ETCHING CHARACTERISTICS OF III-V SEMICONDUCTORS IN MICROWAVE BCL3DISCHARGES

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 i n BCl3 or BCl3/Ar discharges, whereas SF6 addition produces high selec tivities for etching GaAs over AlGaAs. These selectivities are in exce ss of 600 for dc biases of less-than-or-equal-to -150 V, and fall to l ess-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 o f the optical properties of the GaAs and AlGaAs. The AlF3 formed on th e 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 morphol ogies in BCl3 plasmas.