Investigation of surface oxide films on InP mesa sidewalls and flat surfaces reactive ion etched using CH4/H2 chemistry

Oxide films were observed on InP mesa sidewalls and horizontal surfaces after CH₄/H₂ reactive ion etch process. Auger electron spectroscopy and X-ray microanalysis in the transmission electron microscope suggested that the films are In-Si-P or In-P oxides containing more In than P, depending on the RIE instrument utilized. It was suggested that excess In in the film is due to the preferential evaporation of P, and Si is due to the mask erosion during the RIE process. Oxidation of the elements was observed to occur during the subsequent oxygen plasma ashing process. The films presented a serious barrier during the subsequent fabrication processes, such as regrowth and chemical cleaning while they could be effectively removed by cleaning in a diluted HF solution