Effective passivation of the low resistivity silicon surface by a rapid thermal oxide/plasma silicon nitride stack

Abstract

A passivation scheme involving plasma silicon nitride (PECVD SiN) deposition on top of SiO2 grown by rapid thermal oxidation is developed to attain a low surface recombination velocity (S) of nearly 10 cm/s on the 1.25 Ω cm p-type (100) silicon surface. Such low S values are achieved by the stack structure even when the rapid thermal oxide (RTO) or PECVD SiN films individually yield poorer surface passivation. Critical to achieving low S by the RTO/PECVD SiN stack is the use of a short, moderate temperature anneal (in this study 730 °C for 30 seconds) after the stack formation. This thermal treatment is believed to enhance the release and delivery of atomic hydrogen from the SiN film to the Si–SiO2 interface, thereby reducing the density of interface traps at the silicon surface. Compatibility with this post-deposition anneal makes the stack passivation scheme attractive for cost-effective solar cell production where a similar anneal is required to form screen-printed contacts.