High-Performance and Stable Transparent Hf–In–Zn–O Thin-Film Transistors With a Double-Etch-Stopper Layer

Transparent hafnium indium zinc oxide thin-film transistors adopting single- and double-etch-stopper layers were evaluated. Compared to devices with a single
$\hbox{SiO}_{x}$
etch stopper (ES) grown at 150
$^{\circ}\hbox{C}$
, a double ES with a second
$\hbox{SiO}_{x}$
film grown at 350
$^{\circ}\hbox{C}$
provides a superior device performance such as improved subthreshold swing, threshold voltage, field effect mobility, and higher stability under a negative bias stress. The stretched-exponential analyses of the bias stress results indicate that the denser high-temperature
$\hbox{SiO}_{x}$
protects more effectively the underlying semiconductor during the source/drain etch process and suppresses the generation of defect states therein.