Improvement of gate oxide integrity in low temperature poly silicon TFT

摘要

The electrical characteristics of SiH_4-based PECVD gate oxide have been investigated with respect to gate oxide integrity (GOI) and its reliability.It was found that the GOI of poly-Si TFT integrated on glass substrate strongly depended on the charge trapping and deep level interface states generation under Fowler-Nordheim stress (FNS).By applying elevated temperature postanneal without vacuum break after the gate oxide deposition,highly reliable gate oxide was obtained.Under FNS,I_D-V_G curve showed severe shift and degradation of subthreshold slope,which were reduced by adopting post-annealed gate oxide.Besides,the TFT with post-annealed gate oxide showed around 10 times higher charge to breakdown than that of as-deposited gate oxide.Charge to breakdown of MOS capacitors were also studied.By applying post-annealed gate oxide,charge to breakdown drastically improved,which could be explained by reduced charge trapping under FNS.