HYBRID ELECTRON-CYCLOTRON RESONANCE RADIOFREQUENCY PLASMA-ETCHING OF III-V SEMICONDUCTORS IN CL2-BASED DISCHARGES .2. INP AND RELATED-COMPOUNDS

Electron Cyclotron Resonance (ECR) discharges of CCl2F2 or PCl3 have been used to etch InP, InAs, InSb, InGaAs and AlInAs. The etch rates of these materials increase linearly with additional RF power level applied to the cathode and are in the range 50-180 angstrom . min-1 for 50 W (DC bias approximately 308 V), 10 mTorr, 38 CCl2F2/2 O2 plasmas. The etch rates fall rapidly with increasing pressure or increasing O2-to-CCl2F2 ratio. Polymeric surface residues up to 40 angstrom thick are found on all of these semiconductors when using Freon-based gas mixtures. Etching at practical rates is possible with only 100 V self-bias when using PCl3 discharges, and the addition of microwave excitation under these conditions enhances the etch rates by factors of 2-9. At higher self-biases (300 V) etch rates of 3500-8000 angstrom . min-1 are possible with PCl3 although the surface morphologies are significantly rougher and the etching less anisotropic than with CCl2F2-based mixtures.