Observation of oxide films on CH4/H-2 reactive ion etch processed InP mesa sidewalls and surfaces

Oxide films observed on InP mesa sidewalls (about 30 nm thick) and horizontal surfaces (about 10 nm thick) after CH4/H-2 reactive ion etching (RIE) and subsequent O-2 plasma ashing were characterized in detail. Auger electron spectroscopy and x-ray microanalysis in transmission electron microscopy suggested that the films are In-Si-P oxides containing more In than P, which is only partially consistent with previous reports. The films presented a serious barrier during subsequent fabrication processes such as regrowth and chemical cleaning, but could be effectively removed by cleaning in a diluted HF solution. It was proposed that Si in the film was incorporated as a result of mask erosion, excess In was due to the preferential evaporation of P during the CH4/H-2 RIE, and oxidation of the elements occurred during the subsequent oxygen plasma ashing process.