SMOOTH, LOW-BIAS PLASMA-ETCHING OF INP IN MICROWAVE CL2/CH4/H2 MIXTURES

Electron cyclotron resonance microwave (2.45 GHz) discharges of Cl2/CH4/H2 with low additional dc biases ( -80 to -150 V) on the sample are shown to provide smooth, anisotropic dry etching of InP at approximately 150-degrees-C. Rates of 2500 angstrom min-1 are obtained at a pressure of 0.5 mTorr and approximately 80 V dc bias. SiO2 masks show no discernible erosion under these conditions, yielding a process that is extremely well suited for laser mesa fabrication. The CH4 addition promotes the anisotropy of the etching by a sidewall polymer mechanism, while the H-2 addition significantly enhances the etch rate at low pressure.