| Summary: | 碩士 === 國立交通大學 === 光電工程學系 === 98 === In this study, a complete experiment is performed to verify the origin of bias stress induced instability and a fabrication procedure is recommended to attain a stable amorphous In-Ga-Zn-O TFT (a-IGZO TFT). Three treatment phases, including as-deposited, post-annealing, passivated on amorphous Indium-Gallium-Zinc-Oxide thin film transistors (a-IGZO TFTs) were developed and investigated. In as-deposition phase, the influence of deposition parameters on a-IGZO TFTs like substrate temperature, RF-power, working pressure, and gases ratio, are investigated. We demonstrated the phases change from conductor to insulator of the a-IGZO film is tunable by modulating these parameters. In post-annealing phase, the optimized electric characteristic of a-IGZO TFT was attained with mobility ~10cm2/(V-s), sub-threshold swing ~0.1V/dec. , and on/off ratio ~108. In passivation phase, we demonstrated the positive stability of the device enhanced obviously with no degradation of electric performance.
The investment of stability in positive and negative bias stress was implemented for each treatment phase. We provided mechanisms of instability in a-IGZO TFT in each bias stress direction. The evolution of electric characteristics and stability of each treatment phase on device was also investigated. The final device, finished three phase treatments in order exhibited a high-performance and high-stability characteristic. The time constants of threshold voltage shift fitting model under positive and negative bias stress are 860000-sec. and 2140000-sec., respectively.
This thesis provided a usable direction to develop a feasible a-IGZO TFT device with acceptable stability.
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