The influence of the gate dielectrics on threshold voltage instability in amorphous indium-gallium-zinc oxide thin film transistors

Abstract

We investigated the threshold voltage (Vth) instability for various gate dielectrics (SiNx and SiOx) in amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs). The a-IGZO TFTs with SiNx 150 °C exhibited reasonable electrical performance (field-effect mobility of 8.1 cm2/V s and Ion/off ratio of >108) but showed huge Vth shift under positive gate bias. The TFTs with SiOx dielectrics exhibit smaller Vth instability than those of SiNx dielectrics. This behavior can be explained by using simple charge trapping into the gate insulators and the difference of Vth instability on various dielectrics may be originated from the hydrogen contents, providing high density of charge traps in gate dielectrics.

Effects of chemical stoichiometry of channel region on bias instability in ZnO thin-film transistors

“…A linear relationship between the V th shift and the logarithmic stress time without significant changes in the subthreshold swing and field-effect mobility after the stress suggests that the bias instability may be attributed to the negative charge trapping in the gate insulator and/or the channel/dielectric interface as reported in the literatures. [13][14][15] Therefore, the V th shift is nearly independent of the drain bias stresses as shown in Fig. 3͑c͒ since the stress along the lateral direction induced by the drain bias do not enhance charge trapping into the gate insulator.…”

Anomalous Stress-Induced Hump Effects in Amorphous Indium Gallium Zinc Oxide TFTs

“…Especially, a-IGZO TFTs have been recognized as a very promising alternative to display backplanes of active matrix organic light emitting diodes (AMOLEDs) and thin-film transistor liquid crystal displays (TFT-LCDs) [1,2]. For practical applications, it was important to have the bias independent reliability and a number of groups have studied the stability of a-IGZO TFTs [3][4][5][6][7]. Particularly, the hump characteristics were considered as one of the critical issues during the operation in TFT displays affecting pixel brightness [8].…”

Effects of substrate and anode metal annealing on InGaZnO Schottky diodes

“…TFTs with higher performance than conventional amorphous silicon transistors have been developed 1,2 after intensive studies and improvements on carrier transport [3][4][5] and stability. [6][7][8] In contrast, very limited studies have been reported on IGZO-based Schottky diodes. A major challenge is the difficulty in forming stable and ideal Schottky contacts on oxide semiconductors, because the surface of oxide semiconductors is known to be sensitive to device fabrication processes and atmospheric exposure.…”