New Insights into the Impact of Hydrogen Evolution on the Reliability of IGZO FETs: Experiment and Modeling

In this work, we report a comprehensive and deep understanding of the impact of hydrogen evolution on the reliability of the Indium-Gallium-Zinc-oxide (IGZO) FETs with HfO
2
gate dielectric. We innovate in combining negative bias stress (NBS) and positive bias temperature instability (PBTI) and discover: (1) two distinct H states $(H^{P}$ and $H^{N})$, which can be differentiated under different stress and recovery conditions; (2) strong channel length $(L_{ch})$ dependence of threshold voltage shift $(\Delta V_{th})$ under NBS; (3) a unified specific energy density $(E_{s})$ to quantify the transition time from the electron-trapping-dominated region to the H-dominated region. We propose a unique feedback mechanism between the H evolution and V
th
to explain the dramatic V
th
drop in the H-dominated region. We further develop a physics-based model considering the electron trapping, H evolution, and feedback mechanism, leading to an excellent agreement between our modeled results and the measured data.