Analysis of Degradation Mechanism in SONOS-TFT Under Hot-Carrier Operation

This letter investigates the degradation mechanism of polycrystalline silicon thin-film transistors with a silicon-oxide-nitride-oxide-silicon structure under off -state stress. During the electrical stress, the hot hole generated from band-to-band tunneling process will inject into gate dielectric, and the significant on-state degradation (more than 1 order) indicates that the interface states are accompanied with hot-hole injection. In addition, the asymmetric I - V characteristics indicate that the interface states are located near the drain side. Moreover, the ISE-TCAD simulation tool was utilized to model the degradation mechanism and analyze trap states distribution. Although both the vertical and lateral electrical fields are factors for degradation and hot-hole injection, the degradation is mainly affected by the lateral electrical field over a critical point.