| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 94 === In this dissertation, the instability of a-Si:H TFTs with different AC bias stressing frequency conditions stressed at DC and AC bias was discussed. It was found that the mechanism of threshold voltage shift is composed of charge trapping and state creation.
Firstly, we setup a testing system that can support the AC and DC signal to make bias stressing measurement. We used the system to study the factors affecting the characteristics of a-Si:H TFTs under the operation of AC signals. Therefore, we observed the device characteristic under AC signal operation with different polarity, amplitude , frequency and duty ratio. Furthermore, the threshold voltage shift is associated with the duty ratio, variation of characteristics of TFTs is small owning to detrap of charges and relax of created state. Under the drain AC bias stress, we can observe the device characteristic degradation increasing with AC signal frequency decreasing.
Finally, we propose a new process for micro-crystalline TFTs fabrication, and compare the performance with a-Si:H TFTs. We observe that the performance of μ-Si TFT is better than that of a-Si:H TFTs.
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