A New Study on the Degradation Mechanism in Low-Temperature p-Channel Polycrystalline Silicon TFTs Under Dynamic Stress

Pronounced device degradation and temperature dependence of p-channel polycrystalline silicon thin-film transistors (polysilicon TFTs) under pulse stress were investigated. This device degradation is due to the trap states produced by repetition between electron injection and hole injection. The analysis of activation energy affirms that the rapid degradation at high temperature is caused by an increase in the number of trapped holes, to which the negative-bias-temperature stress significantly contributes. The degradation is strongly dependent on the duration of hole injection and the location of the hole-injection region. To produce highly reliable TFT circuits, it is thus important to shorten the duration of hole injection and separate the region of hole injection from that of electron injection.