Effect of back-channel plasma etching on the leakage current of a-Si : H thin film transistors

The effects of back-channel plasma etching conditions and the amount of HCl and plasma power on the leakage current of a-Si:H thin-film transistors (T FTs) were studied. Atomic force microscopy (AFM) and secondary ion mass spe ctrometry (SIMS) analyses were performed to determine the optimal etching c onditions which reduce the leakage current at the back channel. Etching wit h a HCl-rich gas mixture was found to be effective to reduce the leakage cu rrent and chlorine ions were believed to affect the back-channel surface ch aracteristics and exhibit acceptor-like behavior in the lower subthreshold region. Chlorine is believed to suppress the electron generation in the bac k-channel region and trap electrons that are generated by thermal emission. The back-channel surface roughness was found to have no appreciable effect on the leakage current.