Internal structure of mixed phase hydrogenated silicon thin films made at 39℃

摘要

A combined cross-sectional transmission electron microscope (XTEM) and atomic force microscope (AFM) study of a hydrogen to silane dilution series of thin silicon films deposited by very high frequency plasma enhanced chemical vapor deposition at a substrate temperature that is low enough (39℃) to neglect the role of the surface diffusion in the growth process is reported. XTEM images of a mixed amorphous/microcrystalline layer reveal a structure of isolated conically shaped crystalline conglomerates (surface diameter ～570±75 nm) embedded in an amorphous phase of columns with diameters of ～51 ± 3 nm. Detailed closeups of these crystallites, combined with AFM images of the hydrogen dilution dependent evolution of the surface, reveal similarities between the nucleation of amorphous and crystalline columnar structures at this low substrate temperature.