Etching and hydrogen diffusion mechanisms during a hydrogen plasma treatment of silicon thin films

摘要

We present here an in situ spectroscopic ellipsometry (SE) study of hydrogen diffusion through hydrogenated amorphous silicon, when exposed to a hydrogen plasma. The spectroscopic data were analyzed by a combination of the tetrahedron model and the Bruggemann effective medium approximation, Our results indicate that etching of amorphous silicon is not just a surface process. Indeed. the formation of a rather thick sub-surface layer appears as a necessary condition for etching. The hydrogen content and thickness of the sub-surface layer were also confirmed by secondary ion mass spectrometry (SIMS) measurements. These results are discussed with respect to the nucleation process of microcrystalline silicon films. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 12]