Analysis of Degradation Phenomenon Caused by Self-Heating in Low-Temperature-Processed Polycrystalline Silicon Thin Film Transistors

The reliability of low-temperature-processed (≦425°C) polycrystalline-silicon thin film transistors (poly-Si TFTs) was investigated. For n-channel TFTs, the sub-threshold characteristics shifted in the positive direction when a high voltage stress was applied to them, which is particularly significant in small-size TFTs as well as in wide-channel TFTs. It was verified that the temperature of the TFTs reached over 300°C due to self-heating when this stress was applied. We estimate that the breaking of Si–H bonds and re-generation of dangling bonds in the channel poly-Si layers due to self-heating are responsible for the degradation phenomenon.