Characterisation of SiOX / SiNX Surface Passivation Using Time-of-Flight Elastic Recoil Detection Analysis

An accurate description of the distribution of hydrogen at solar cell interfaces is critical for understanding both passivation and degradation phenomena. Time-of-flight elastic recoil detection analysis (ToF-ERDA) has recently been employed to study this hydrogen distribution by providing a one-dimensional (1D) depth profile. In this work, ToF-ERDA was used to investigate the hydrogen profile in a SiOX / SiNX passivating stack. The ability to resolve the interface with the c-Si interface was studied by using polished wafers and thin (20 nm) passivating stacks. This approach, coupled with Monte Carlo ERD (MCERD) modelling, showed that the identification of the interfacial oxide was much more clearly defined compared with previous reports using ToF-ERDA. Annealing the SiOX / SiNX at 450 °C for 5 minutes substantially increased the effective lifetime. However, no noticeable change in the H distribution measured with ToF-ERD was observed. We comment on the difficulty of correlating physical hydrogen measurements with the surface recombination properties.