Smooth, low-bias plasma etching of InP in microwave Cl2/CH4/H2 mixtures

Abstract
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 ∼150 °C. Rates of 2500 Å min−1 are obtained at a pressure of 0.5 mTorr and ∼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 H2 addition significantly enhances the etch rate at low pressure.