Performance and Reliability Comparison of ZnO and IGZO Thin-Film Transistors and Inverters Fabricated at a Maximum Process Temperature of 115 °C

Performance and reliability comparison of oxide-based thin-film transistors fabricated at a maximum process temperature of 115 °C is presented. A fully patterned and passivated process was successfully evaluated and implemented using polycrystalline ZnO and amorphous indium-gallium-zinc-oxide (IGZO) as an active layer in glass substrates. Saturation mobilities of 14.2 and 9.0 cm
²
·V
^-1
·s
^-1
were obtained for ZnO and IGZO, respectively, with threshold voltages of 2.2 and 2.0 V, an ON/ OFF ratio > 1 × 10
⁸
, and an I
_off
<; 1 × 10
^-12
A. The small mobility change in IGZO with gate voltage is due to its amorphous character. Longer variation is observed in polycrystalline ZnO due to its grain boundaries. Reliability studies show a threshold voltage shifting of 0.4 and 1.8 V for ZnO and IGZO devices, testing after 1200-s stress. Devices were successfully implemented in ZnO- and IGZO-based inverters using saturation and zero-drive structures, showing a maximum dc gain of 2.4and 25-V/V, respectively.