Investigation of the Surface Passivation of P+-Type Si Emitters by PECVD Silicon Carbide Films

The surface passivation of an industrial applicable (e.g. screen printing) 60 Omega_{sq/ p⁺ boron emitter on Cz n-type c-Si wafers by amorphous SiCx films is investigated. A partial optimization of the deposition conditions of the SiCx films was performed resulting in an improved passivation quality of the SiCx films which also serves as anti-reflection coating. Passivation quality is determined by measuring the injection level dependency of the effective minority carrier lifetime using the quasi-steady state photoconductance method. Combining the information form the boron diffusion profile measured by SIMS and injection level dependent lifetime curves it can be concluded that a boron depletion layer formed during in-situ drive-in and oxidation has a detrimental effect on the passivation quality. Changing the diffusion conditions to prepare an improved boron profile with a similar sheet resistance should result in a further improvement of the passivation quality. This could include a reduction or a removal of the boron depletion layer at the emitter surface}