Passivation kinetics of two types of defects in polysilicon TFT by plasma hydrogenation

The effects and kinetics of hydrogen passivation on polycrystalline-silicon thin-film transistors (poly-TFTs) are investigated. Based on the response of device parameters with the progress of hydrogenation, two types of defects can be distinguished from the difference in passivation rate. The threshold voltage and subthreshold slope, which are strongly influenced by the density of dangling bond midgap states, have a faster response to hydrogenation. The off-state leakage current and field-effect mobility, related to stain-bond tail states, respond more slowly to hydrogenation, with an onset period of approximately 4 to 12 h depending on the grain size. Since the larger-grain-size samples showed a longer onset period, the contribution of intragranular defects to the strain-bond tail states appears to be significant.<>