In situ X-ray photoelectron spectroscopy study of etch chemistry of methane-based reactive ion beam etching of InP using N2

The effects of nitrogen gas on the methane-based reactive ion beam etching (RIBE) of InP were studied in detail. The surface was very rough and covered with In droplets and heavy polymer when it was etched by the mixture of CH4/H2 without nitrogen gas. In contrast, the surface smoothness was improved markedly when nitrogen gas was added, realizing a root mean square (RMS) roughness comparable to that of the initial InP surface before etching. From the detailed X-ray photoelectron spectroscopy (XPS) analysis, it was found that the formation of P-N bonds on the surface could suppress the preferential evaporation of P atoms in the PH3 form and balance the In- and P-reactions during the etching process. This resulted in the decrease of In droplets and a smoother etched InP surface. It was also found that the rate limiting process for etching was the In-related reaction. The study of Raman scattering showed that the crystal quality of the etched surface was improved when N2 gas was added to the CH4/H2 mixture.