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 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. © 1998 American Institute of Physics.