The clarification of leakage conduction mechanism of HfO2/SiNx stacked a-IGZO TFT and its variation at high temperature

Abstract

In this paper, the current conduction mechanisms of an a-IGZO thin-film transistor based on HfO2/SiNx stacks were investigated at room temperature and its variation at 523 K. Ti/HfO2/SiNx/ITO metal–insulator–metal capacitors were fabricated and researched under positive gate bias by performing current–voltage measurements. As a function of electric field, different types of current conduction mechanisms were detected, i.e., ohmic conduction (5–15 MV/m), Frenkel–Poole emission (17.5–50 MV/m), and trap assisted tunneling (52.5–100 MV/m). With the increase in temperature, leakage current increased about two orders of magnitude combined with the variation of leakage mechanisms. The barrier height and dielectric constant were reduced simultaneously, proving the deterioration of dielectric properties at high temperature.