Plasma oxidation for the front side passivation of perc solar cells

A thin silicon oxide film is grown using microwave plasma oxidation (MW-PO) for improving the surface passivation quality of silicon nitride SiNx anti reflection coating layer on crystalline silicon wafers without affecting the optical properties of the layer. The SiNx layers deposited at different conditions of chamber pressure are found to have different optical properties. Meanwhile, inclusion of thin oxide layer did not lead to change in optics of the front-side passivation stack. The oxide thickness was varied from 1.5-2.5 nm and is found to be influenced mainly by the change in the microwave power, chamber pressure and the substrate temperature. A comparison of single layer SiNx and the SiOx/SiNx stack is made for PERC solar cells, which revealed an enhancement of open-circuit voltage VOC up to 7 mV for the stack layer suggesting a positive effect of plasmabased oxidation on the emitter surface passivation.