Bulk and Surface Passivation by Silicon Nitride Grown by Remote Microwave PECVD

摘要

Surface and bulk passivating properties of SiN,:H layers deposited by RemoteMicrowave PECVD are investigated. We found that the N/Si ratio of the layers is dependent of the substrate temperature, which suggests that the layer growth is dominated by and arrival of separate SiH and NH species at the surface and not by the arrival of SiN,Hy clusters formed in the plasma. SiNx:H layers with good surface passivating properties require different deposition conditions than layers with good bulk passivating properties. For good surface pasivation, Si-rich layers are needed with relatively low H-concentrations. For layers which can provide good hydrogenation through firing, more stoichiometric and hydrogen rich layers are required in which the hydrogen is predominantly bonded to N-atoms. For p-type mc-Si Baysix wafers we found SiNx:H induced hydrogenation can improve the bulk lifetime of charge carriers by more than 20%. No synergistic effects of an A1 BSF on this hydrogenation process, however, were observed.