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We proposed here a reliability model that successfully introduces both the physical mechanisms of negative bias temperature instability (NBTI) and hot carrier stress (HCS) for p-channel low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs). The proposed model is highly matched with the experimental results, in which the NBTI dominates the device reliability at small negative drain bias while the HCS dominates the degradation at large negative drain bias. In summary, the proposed model provides a comprehensive way to predict the lifetime of the p-channel LTPS TFTs, which is especially necessary for the system-on-panel circuitry design.Index Terms-Hot carrier stress (HCS), low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs), negative bias temperature instability (NBTI), reliability.

The degradation mechanisms of both negative bias temperature instability ͑NBTI͒ and positive bias temperature instability ͑PBTI͒ were studied for low-temperature polycrystalline silicon complementary thin-film transistors. Measurements show that both NBTI and PBTI are highly bias dependent; however, the effect of the temperature is only functional on the NBTI stress. Furthermore, instead of interfacial trap-state generation during the NBTI stress, the PBTI stress passivates the interface trap states. We conclude that the diffusion-controlled electrochemical reactions dominate the NBTI degradation while charge trapping in the gate dielectric controls the PBTI degradation.