Measurement of Sidewall Roughness of InP Etched by Reactive Ion Beam Etching

We have quantitatively measured the sidewall roughness of InP etched by reactive ion beam etching (RIBE) for the first time. An electron probe surface roughness analyzer was employed. The minimum value of average sidewall roughness appeared to be 1 nm and the peak-to-peak roughness appeared to be 6 nm. The etching conditions were an ion extraction voltage of 400 V and a Cl2 gas pressure of 1.2× 10-3 Torr. It is found that the etched sidewall roughness is decreased by lower-ion-extraction-voltage etching in a constant gas pressure, as well as by higher-gas-pressure etching with a constant ion extraction voltage.