Robust Mobility Enhancement and Comprehensive Reliability Evaluation for Amorphous InGaZnO TFT by Double Layers With Quantum Well Structures

Mobility enhancement is an important research topic for amorphous InGaZnO (a-IGZO) thin-film transistor (TFT) since it is directly related to the device’s performance. The double-layer a-IGZO channel with quantum well structure was proposed for mobility enhancement. However, the impact of such double layers with the quantum well structure on a-IGZO TFT reliabilities, i.e., positive bias temperature stress (PBTS) and negative bias temperature illumination stress (NBTIS), is still elusive. In this work, the mobility enhancement by double layers with quantum well structures is proven to be robust in mass production Gen 8.5 line. Then, the a-IGZO TFT under PBTS and NBTIS is investigated systematically. The variations of mobility
$\mu $
, subthreshold slope SS, and threshold voltage shift
${\Delta {V}_{\text {th}}}$
with PBTS and NBTIS stress time are evaluated and analyzed, respectively. It is shown that the double-layer a-IGZO channel with quantum well structure can sustain as good reliability performance as the reference single-layer device.