Relationship between PECVD silicon nitride film composition and surface and edge passivation

Abstract

The relationship between film composition and surface passivation provided by PECVD silicon nitride is investigated in this work. Various surface types and planes of n-type float zoned wafers were studied: planar (100), planar (111), textured (random upright pyramids with (111) facets), boron-diffused layer on planar (100) surfaces, and the edges intersecting the p-n junction. The relationship between film composition and surface passivation on planar (100) p-type silicon is also presented. Light soaking and thermal treatments were performed on the samples and the relationship between film composition and stability is briefly explored. It is shown that, with optimised film composition, SiN layers can provide excellent and stable passivation on all surface types investigated in this work. Implied open circuit voltage of more than 700mV and boron emitter dark saturation currents as low as 5 fA/cm are demonstrated.