在此論文中，我們將研究P通道低溫複晶矽薄膜電晶體（LTPS TFTs）經過靜態及動態stress後的劣化機制。樣品為奇美公司所提供。
在靜態stress方面，將研究P通道LTPS TFTs在暗態及照光環境下的負偏壓溫度不穩定性 (NBTI)。在不同的NBTI stress環境下，實驗結果顯示出介面缺陷能態密度 (Nit) 產生量是沒有變化。然而，晶界缺陷能態密度 (Ntrap) 的產生量在照光環境下stress後明顯比在暗態環境下stress還要來的多。這個現象主要是因為照光後產生的額外電洞所造成的影響。
在動態stress方面，我們發現Nit與Ntrap的劣化與stress頻率有關，且隨著頻率增加而減少。結果指出此劣化機制與poly-Si bulk上的主要載子反應有關。另外，Ntrap產生量與閘極端stress波形的rising time有正相關。Nit產生量則不會隨著波形的rising time和falling time調變而改變。此外，在低頻 (<10Hz) 下作stress時，Ntrap的產生量在照光下明顯比暗態多，而在高頻 (>10Hz) 下則沒有差異。
樣品經過機械應力彎曲後，sample對光的敏感度會產生變化，n-type部分由於bending後的tail state較少，載子藉由光源的能量跳出淺缺陷形成漏電流的機率變小，因此光敏感度變差。而p-type則沒有明顯差異。此外，將p-type TFT bending後的sample經過DC以及AC NBTI stress，發現Nit和Ntrap的產生量明顯比在平坦下作stress的產生量還要來的多。這個現象主要是因為sample在經過bending後反轉層內的載子數目增加，在stress過程中有更多的電洞參與NBTI effect發生，導致產生更多的劣化出現。

In this thesis, we will investigate the mechanism of the degradation on the p-channel Low Temperature Polycrystalline Silicon thin film transistors (LTPS TFTs) under the static and dynamic stresses. The devices are offer by Chi Mei Optoelectronics.
On the static stress, the negative bias temperature instability (NBTI) in the p-channel LTPS TFTs under darkened and illuminated environments was investigated. Experimental results reveal that the generation of Nit showed no change between the different NBTI stresses. However, the generation of Ntrap under illumination was more significant than that in the darkened environment. This phenomenon is mainly caused by the extra number of holes generated during the illuminated NBTI stress.
On the dynamic stress, we found that the degradation of Nit and Ntrap were dependent the stress frequency and the degradation were decreased with the frequency increasing. The results indicated that the mechanism of the degradation was the relation with the response of the major carrier on the poly-Si bulk. In addition, the generation of Ntrap was strongly relation with the rising time of gate-pulse. The Nit revealed no change under the different rising and falling times when gate was applied the dynamic signal. Besides, the generation of Ntrap under illuminated stress was more significant than that in the darkened environment at low stress frequency (<10Hz), but it was no difference at high stress frequency (>10Hz).
Under the mechanical bending, the photosensitive was significantly changed. In n-type TFTs, the quantity of tail state was less in bending condition then in flat condition. The light-induced electrons was trapped by shallow trap and decreasing the photosensitive. However, the phenomenon was no distinct in p-type TFTs. In addition, the generation of the traps and holes in the inversion layer due to mechanical bending was assisted the degradation of the device. The generation of Nit and Ntrap were more serious in bending condition then in flat condition in p-type under the static and the dynamic NBTI stress.

致謝 2
中文摘要 3
English Abstract 5
Figure Captions 9
Chapter 1 - Introduction 14
1-1. Overview 14
1-2. Motivation 18
1-3. Introduction of Negative Bias Temperature Instability 19
Chapter 2 – Device fabrication and electrical characterization 23
2-1. Device Fabrication 23
2-1-1. Technology of ELA Crystallization 23
2-1-2. Fabrication Processes of LTPS Poly-Si Device 24
2-2. Defects in polycrystalline-silicon film 25
2-3. Basic characterization of the LTPS TFT 27
2-3-1. The I-V transfer characteristics 27
2-3-2. The C-V transfer characteristics 29
2-4. Introduction of Seto’s model 30
Chapter 3 – Instruments and device parameter extraction 35
3-1. Instruments and measurement setup 35
3-1-1.Instruments 35
3-1-2.Set up instruments for I-V 36
3-2. Methods of Device Parameter Extraction 36
3-2-1 Determination of the threshold voltage 36
3-2-2 Determination of the field-effect mobility 38
3-2-3 Determination of on/off current ratio 39
3-2-4 Determination of the subthreshold swing 39
3-2-5 Determination of the trap density 40
3-2-6 Determination of the active energy 41
3-2-7 Determination of density of state 42
Chapter 4 – Results and Discussion 44
4-1. The influence of DC NBTI stress on LTPS TFTs 44
4-1-1 The Degradation of P-channel TFT under DC NBTI 44
4-1-2 The illuminated effect 46
4-2. The influence of AC NBTI stress in LTPS TFTs 48
4-2-1 The Degradation of P-channel TFT under AC NBTI 48
4-2-2 The Degradation of Pulse Rising and Falling time 49
4-3. The influence of mechanical bending 50
4-3-1 The photosensitive in LTPS TFTs 50
4-3-2 The NBTI effect 51
Chapter 5 - Conclusion 52
Reference 53
Figure 63

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