Comparative study on light-induced bias stress instabilities of IGZO thin film transistors with SiN_x and SiO_x gate dielectrics

摘要

We investigated the effect of gate dielectric materials on the light-induced bias-temperature instability of IGZO TFT. The application of light on the negative bias temperature stress (NBTS) accelerated the negative displacement of the threshold voltage (V_(th)) of the SiO_x-gated IGZO TFT. This phenomenon can be attributed to the trapping of the photon-induced carriers into the gate dielectric/channel interface or the gate dielectric bulk. Interestingly, the negative V_(th) shift under photon-enhanced NBTS condition was deteriorated for the SiN_x-gated IGZO TFTs. This result can be explained by considering the hole carrier injection barrier (i.e. valance off-set) and the density of hole trap centers in bulk gate dielectric materials for both devices.