Low Surface Recombination Velocity using amorphous Silicon on industrial-type cleaned Surfaces

摘要

The surface passivation ability of a hydrogenated amorphous silicon (a-Si:H) layer is investigated on industrial-type cleaned p-type (2 Dcm) FZ and Cz silicon wafers. The cleaning sequence consists of laser/saw damage removal and immersions in aqueous HCl and HF solutions. After this cleaning an effective surface recombination velocity S_(eff) of 1.0 cm/s is achieved with a deposited and annealed a-Si:H-layer. No RCA or similar elaborate cleaning steps are needed to achieve this low surface recombination velocity. After a firing step in a belt furnace at a wafer temperature of up to 670°C the passivation ability of the a-Si:H layer is fully restored during hydrogen annealing. It is shown that the amount of silicon hydrogen bonds in the a-Si:H layer is correlated to the degradation and recovery of the passivation quality of the a-Si:H layer.