Passivation of Liquid‐Phase Crystallized Silicon With PECVD‐SiN_x and PECVD‐SiN_x/SiO_x

Abstract

Silicon nitride (SiN x ) and silicon oxide (SiO x ) grown with plasma-enhanced chemical vapor deposition are used to passivate the front-side of liquid-phase crystallized silicon (LPC-Si). The dielectric layer/LPC-Si interface is smooth and layers are well-defined as demonstrated with transmission electron microscopy. Using electron energy loss spectroscopy a thin silicon oxynitride is detected which is related to oxidation of the SiN x prior to the silicon deposition. The interface defect state density (D it ) and the effective fixed charge density (Q IL,eff ) are obtained from high-frequency capacitance-voltage measurements on developed metal-insulator-semiconductor structures based on SiO x /SiN x /LPC-Si and SiO x /SiN x /SiO x /LPC-Si sequences. Charge transfer across the SiN x /LPC-Si interface is observed which does not occur with the thin SiO x between SiN x and LPC-Si. The SiO x /SiN x /LPC-Si interface is characterized by Q IL,eff > 10 12 cm À2 and D it,MG >10 12 eV À1 cm À2 . With SiO x /SiN x /SiO x stack, both parameters are around one order of magnitude lower. Based on obtained Q IL,eff and D it (E) and capture cross sections for electrons and holes of σ n ¼ 10 À14 cm s À1 and σ p ¼ 10 À16 cm s À1 , respectively, a front-side surface recombination velocity in the range of 10 cm s À1 at both interfaces is determined using the extended Shockley-Read-Hall recombination model. Results indicate that field-effect passivation is strong, especially with SiO x /SiN x stack.