Water-Related Instability in Low-Temperature Polycrystalline Silicon Thin-Film Transistors Caused by Self-Heating

It was observed that the bias stressing of low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs) gave rise to anomalous instabilities in device characteristics, such as negative threshold voltage shifts in both n- and p-channel TFTs, and the recovery of the shift even under stress. From detailed investigations of these phenomena, it was found that the instability is caused by self-heating due to the drain current, and is related to hydrogen and/or water diffusing into the gate oxide from the interlayer dielectric. It is considered that these phenomena will become more significant in future scaled TFTs; therefore, it is important that low-temperature processes taking account of water-related components are carefully introduced. (c) 2011 The Japan Society of Applied Physics