Smooth, anisotropic etching of indium containing structures using a high density ICP system

Most methods for dry etching indium-containing materials involve the use of hydrocarbon and halogen-based plasmas. This work presents HBr-based chemistries using a high density plasma ICP system to provide an inherently anisotropic, smooth and notch free etching process. Indium containing structures were etched at rates of 2.0 μm/min with extremely smooth, clean surfaces (surface roughness < 2.0 nm RMS). The etch selectivity to hard masks (SiO₂ or SiN_x) was greater than 30:1. Waveguide loss values of less than 1 dB/cm are reported.