Trimethylamine: Novel source for low damage reactive ion beam etching of InP

A new reactive ion beam etching process using trimethylamine for low damage etching of InP at room temperature has been developed. Characteristics of the etching process, i.e., etch rate, surface morphology, and etch-induced damage are reported. Photoluminescence yield (PLY) was used to characterize the residual damage by using near-surface quantum wells as probes and the etched surface morphologies were quantified by roughness measurements using atomic force microscopy. The etch rate could be varied by over an order of magnitude, from low (∼4 nm/min) at 75 eV up to 100 nm/min at 500 eV. The etched surfaces were extremely smooth (rms roughness <1 nm) independent of ion energy. This was so even for samples etched to a depth of more than 1 μm. Process induced damage as measured by PLY was also significantly smaller than for CH4 based dry etch processes. Further, upon annealing at 650 °C in a PH3 ambient, the etched samples showed near complete PLY recovery, indicating significant damage reduction. Hence, the new process results in a simplified plasma chemistry that provides not only reasonable etch rates but also extremely smooth surfaces and low optical damage.