Reliability improvement in low-temperature processed poly-Si TFTs for AMLCDs

Low-temperature processed polysilicon thin-film-transistors have shown negative threshold voltage shift under gate bias stress. This shift was produced as a result of the positive charge created by water penetration and by the subsequent field activated chemical reaction in the gate oxide. Thermal desorption mass spectrometry (TDS) measurements reveal that dissociation of Si-OH bonds with hydrogen-bonded water in the oxide may be a fundamental contributor to the creation of the positive charge. As a preventative measure, we used hydrogenation to dissociate the Si-OH bonds beforehand, and in this way we have been able to obtain stable TFTs that can be applied to drivers for AMLCDs.<>