Investigation of a PECVD Silicon Oxide/Silicon Nitride Passivation System Concerning Process Influences

In this work we investigated the properties of silicon oxide (SiOy) and silicon nitride (SiNx) layers deposited by a large area 13.56 MHz PECVD system as well as of the combined SiO-SiN stack . The bonding nature of the layers was determined by FTIR spectroscopy. Furthermore, a characterization of the interface trap density as well as of the fixed charges in the different passivating layers was performed by preparing and measuring metal-insulator-semiconductor samples and supplemented by lifetime measurements. We show how temperature steps as well as x-ray and UV-radiation change the layer properties: High energetic radiation leads to a depassivation of the surface deposited with the SiO-SiN stack. The low surface recombination velocity can be fully recovered by an annealing step. In addition, rear side passivated solar cells were fabricated with a SiO-SiN stack as passivation layer and the rear surface recombination velocity of the solar cells was measured by the CELLO technique.