Surface Passivation of Crystalline and Polycrystalline Silicon Using Hydrogenated Amorphous Silicon Oxide Film

摘要

Excellent passivation properties of hydrogenated amorphous silicon oxide (a-SiO_x:H) prepared by very high frequency plasma-enhanced chemical vapor deposition (VHF PECVD) at a low substrate temperature (170℃ on crystalline and polycrystalline silicon (Si) wafers are reported. Films were characterized by ellipsometry, Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-vis) spectrophotometry, and dark-conductivity and photoconductivity measurements. A comparison of the results with those for different passivation layers such as hydrogenated amorphous silicon carbon nitride (a-SiO_xN_y:H), hydrogenated amorphous silicon nitride (a-SiN_x:H), and hydrogenated amorphous silicon (a-Si:H) reveals their superiority as an excellent passivation layer for p-type crystalline Si as well as polycrystalline Si. A maximum effective lifetime of 400 μs was measured for 1-10 Ω cm, 380-μm-thick p-type c-Si using a micro-photocurrent decay (μ-PCD) system. Fixed charge density (Q_f) was estimated by high-frequency (1MHz) capacitance-voltage measurement using a metal-insulator-silicon structure (CV-MIS). The effect of annealing temperature on surface passivation in a nitrogen atmosphere was also studied.