Observation of oxide films on 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 reactive ion etching (RIE) and subsequent 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 RIE, and oxidation of the elements occurred during the subsequent oxygen plasma ashing process.