Elemental evolution of the SiOxFy self-masking layer of plasma textured silicon and its modification during air exposure.

The influence of the SiO_xF_y selfmasking process on the formation of black-Silicon (b-Si) textures by maskless SF₆/O₂ plasma etching is of great interest with regard to the optimization of the texturing process for highly antireflective silicon. For that reason, the elemental composition of plasma textured silicon surfaces is analyzed by transmission electron microscopy and X-ray photoelectron spectroscopy. The chemical composition of a fluorine containing oxide layer on top of the surface was confirmed and determined quantitatively. A strongly reduced F content was found after ambient air exposure. A qualitative model of the chemical and physical processes caused by maskless plasma texturing was developed to explain the observed experimental results. The decrease in the F content is assumed to be caused by hydrolysis of F by air moisture, resulting in a successive desorption of HF and transformation of SiO_xF_y to silicon oxide. [ABSTRACT FROM AUTHOR]