Investigation of Field-Effect Passivation Created by Hydrogen Plasma Etching of Radio Corporation of America Formed Chemical Oxides on Crystalline Silicon Wafers

摘要

This work investigates the interface properties of intrinsic hydrogenated amorphous silicon film passivated wafers that underwent hydrogen plasma cleaning. A high level of interface band bending of nearly -0.6 eV, which corresponds to a fixed charge of -2.2 x 10(12) cm(-2), is found to be responsible for an effective minority carrier lifetime of over 6 ms on the 4.5 omega cm n-type wafer, while such field-effect passivation is missing in hydrofluoric acid (HF) cleaned wafers. Further study indicates a positive correlation between the extent of surface band bending and doping concentration, together with an inverted U-shape with respect to the increased annealing condition. The fixed charge on p-type wafer is found to have a higher "formation energy" compared with the n-type case, which renders its field-effect passivation much less effective due to H effusion at high annealing temperatures. With reference to the theory on donor/acceptor-H complex upon H plasma treatment, the origin and observed properties of the surface band bending on both dopant types are discussed. The unique presence of field effect on hydrogen plasma cleaned n-type wafers can provide new insights into passivation material selection and structural design of heterojunction silicon wafer solar cells.