Smooth and Vertical InP Reactive Ion Beam Etching with Cl2 ECR Plasma

Smooth and vertical InP reactive ion beam etching has been achieved with electron cyclotron resonance Cl2 plasma at high ion energy (≥900 eV), high temperature (230°C) and relatively low Cl2 pressure (∼10-4 Torr). Smooth etching of an InP system by Cl2 plasma has often been reported as difficult compared to that of the GaAs system due to low volatility of reactive products such as InCl x . In the present work, precise control of incident ion energy and Cl2 pressure contributed to the improvement of both the vertical profile and bottom smooth surface under high substrate temperature (∼200°C). Vertical profiles were easily achieved even at high temperatures by varying the Cl2 pressure. While etching conditions suitable for vertical wall-formation were maintained, surface morphology was drastically improved by increasing ion energy above 900 eV and the bottom roughness became less than 100 nm at 1450 eV.