Improvements in the Passivation of P+-Si Surfaces by PECVD Silicon Carbide Films

We present further results of a surface passivation study of p⁺-Si emitters by both intrinsic and boron-doped amorphous SiC_x films, deposited in two different standard PECVD reactors. For comparison, thermally grown SiO₂ and PECVD-SiN _x layers with refractive indices of n=2.0 and n=2.4 were examined on the same test structures. While thermal SiO₂ exhibits passivating properties comparable to those on n⁺-Si emitters, PECVD-SiN_x is found to even deteriorate the surface passivation, especially after firing (without metal contacts). On the other hand, PECVD-SiC_x yields, to our knowledge, the best p ⁺-Si passivation so far obtained by an industrially relevant low temperature process. It is expressed by an implied V_oc of 635 mV for a symmetrically 60 Omega/sq BBr₃-diffused n-type CZ-wafer with a base resistivity of 4.6 Omegacm