Nanostructure evolution of magnetron sputtered hydrogenated silicon thin films

Abstract

Hydrogenated silicon (Si:H) thin films have been prepared by radio frequency (RF) magnetron sputtering. The effect of hydrogen gas concentration during sputtering on the resultant film structural and optical properties has been investigated by real time spectroscopic ellipsometry (RTSE) and grazing incidence x-ray diffraction (GIXRD). The analysis of in-situ RTSE data collected during sputter deposition tracks the evolution of surface roughness and film bulk layer thickness with time. Growth evolution diagrams depicting amorphous, nanocrystalline, and mixed-phase regions for low and high deposition rate Si:H are constructed and the effects of process parameter (hydrogen gas concentration, total pressure, and RF power) variations on the deposition rate have been qualified. Virtual interface analysis of RTSE data provides nanocrystalline volume fraction depth profiles in the mixed-phase growth regime. GIXRD measurements show the presence of (111) and (220) oriented crystallites. Vibrational mode absorption features from Si-Hn bonding configurations at 590, 640, 2000, and 2090 cm−1 are obtained by ex-situ infrared spectroscopic ellipsometry. Hydrogen incorporation decreases as films transition from amorphous to nanocrystalline phases with increasing hydrogen gas concentration during sputtering.