Browsing by Author "Yang, Yi-Chieh"

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Investigating degradation behaviors induced by mobile Cu ions under high temperature negative bias stress in a-InGaZnO thin film transistors
(2017-09-25)
Chiang, Hsiao-Cheng
;
Chang, Ting-Chang
;
Liao, Po-Yung
;
Chen, Bo-Wei
;
Tsao, Yu-Ching
This letter investigates the effect of negative bias temperature stress (NBTS) on amorphous InGaZnO4 thin film transistors with copper electrodes. After 2000 s of NBTS, an abnormal subthreshold swing and on-current (I-on) degradation is observed. The recovery of the Id-Vg curve after either annealing or positive bias temperature stress suggests that there are some native mobile copper ions in the active layer. Both the existence of copper and the degradation mechanism can be confirmed by AC stress with different frequencies and by transmission electron microscope energy-dispersive X-ray spectroscopy analysis. Published by AIP Publishing.
Role of H2O Molecules in Passivation Layer of a-InGaZnO Thin Film Transistors
(2017-04-01)
Chien, Yu-Chieh
;
Chang, Ting-Chang
;
Chiang, Hsiao-Cheng
;
Chen, Hua-Mao
;
Tsao, Yu-Ching
This letter analyzes performance and reliability of inverted staggered type amorphous indium-gallium-zinc oxide devices in a moist environment with H2O molecules in the passivation layer. There is a negative threshold voltage shift (Delta Vth) in the saturation region (V-D = 10 V), which increases with decreasing channel length. We propose that this is explained by the drain-induced barrier lowering that is due to the H2O molecules. Moreover, a hydrogen bonding model under bias stress is also proposed, in contrast to the conventional H2O doping model. Recovery behavior after bias stress and ac operation were utilized to distinguish the difference between these models.