Passivation of Liquid‐Phase Crystallized Silicon With PECVD‐SiNx and PECVD‐SiNx/SiOx

Abstract

Silicon nitride (SiNx) and silicon oxide (SiOx) 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 SiNx prior to the silicon deposition. The interface defect state density (Dit) and the effective fixed charge density (QIL,eff) are obtained from high‐frequency capacitance‐voltage measurements on developed metal‐insulator‐semiconductor structures based on SiOx/SiNx/LPC‐Si and SiOx/SiNx/SiOx/LPC‐Si sequences. Charge transfer across the SiNx/LPC‐Si interface is observed which does not occur with the thin SiOx between SiNx and LPC‐Si. The SiOx/SiNx/LPC‐Si interface is characterized by QIL,eff > 1012 cm−2 and Dit,MG>1012 eV−1 cm−2. With SiOx/SiNx/SiOx stack, both parameters are around one order of magnitude lower. Based on obtained QIL,eff and Dit(E) and capture cross sections for electrons and holes of σn = 10−14 cm s−1 and σp = 10−16 cm s−1, respectively, a front‐side surface recombination velocity in the range of 10 cm s−1 at both interfaces is determined using the extended Shockley‐Read‐Hall recombination model. Results indicate that field‐effect passivation is strong, especially with SiOx/SiNx stack.