Reliability of Low Temperature Polycrystalline Silicon Thin-Film Transistors with Ultrathin Gate Oxide

We analyzed the reliability against the hot-carriers effect and Joule heating effects of low-temperature polycrystalline silicon (poly-Si) thin-film transistors (TFTs) with an ultrathin gate oxide film deposited by sputtering. For the hot-carrier effect, although the generation of hot-carriers was enhanced in TFT with a thin gate oxide film, no marked degradation due to direct constant voltage (DC) stress was observed in the electric characteristics even when the thickness of the gate oxide film was 9.5 nm. Regarding the effect of Joule heating on the reliability, the thickness of the oxide film markedly affected the TFT characteristics. A new degradation mode different from the conventional mode with a shift in threshold voltage owing to heat generation was observed when the oxide film was extremely thin in spite of small amount of heat generated during the application of DC stress. Regarding the reliability of the low-temperature poly-Si TFT with an ultrathin gate oxide film, the results revealed that a new degradation mode develops due to heat generation.