臺灣博碩士論文加值系統

氫化非晶矽薄膜電晶體已被廣泛應用於各類的顯示器產品中，雖然它的載子遷移率與元件的可靠度方面表現皆不如多晶矽的薄膜電晶體，但因技術成熟且成本較低，因此元件的可靠度仍有值得研究的地方。本論文採用的為非對稱結構的氫化非晶矽薄膜電晶體，探討在紅綠光照度應力和各種不同電壓應力下的可靠度研究。

在直流應力部分，當閘極給予直流應力時，閘極絕緣層或閘極絕緣層與主動層接面發生載子捕捉，使臨界電壓發生變化；當同時給於電性應力與紅綠光照度應力，通道內因為受到光源的照射產生大量的電子電洞對，使得有更多載子被捕捉，且光源提供額外的能量，使弱鍵結斷裂形成空懸鍵，導致臨界電壓有不同的變化，且因兩種光源能量不同，因此元件電性參數退化量的差異，也有相當程度的不同，當加長應力時間並同時照射同照度的紅綠光源，在閘極施加正電壓與負電壓兩種不同電性應力下，元件特性退化的狀況有很明顯的差異。

在交流訊號的部分，當閘極給予不同頻率的0~+30 V交流電壓，元件的電性參數退化量，並沒有因頻率的改變而有太大的變化，而當加了綠光後，發現臨界電壓雖然皆因多加入綠光的緣故而變大，但與頻率之間依舊沒有關聯；而在閘極施加-30~0 V交流電壓部分，元件產生退化的機制與直流偏壓相似，但臨界電壓的變化量較小，因為在一個週期的交流訊號內，只有在高電場時間內，才會發生有效的載子捕捉機制，然而當給予負電性交流應力並同時照綠光時，元件的電性參數退化量卻比只施加負交流電性應力來的小。

Hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) are widely used in various display products. Although the carrier mobility and device stability are not excellent as polycrystalline silicon thin-film transistors (poly-Si TFTs), due to the mature manufacture skills and the low cost, the reliability research of the a-Si:H TFTs is still valuable. In this study, we investigate the reliability of the asymmetric structure of a-Si:H TFTs under different voltage stresses with red and green light illuminance.
In DC stress, a-Si:H TFTs stressed by high gate bias, the carrier would be trapped into gate insulator or the interface between gate insulator and channel layer, resulting in the threshold voltage shift. After a-Si:H TFTs stressed by gate bias and with red and green light illuminance at the same time, the charge trapping is serious due to light irradiation generating more electron hole pairs in the channel. It also supplies additional energy, and the weak bond of silicon may be broken, forming the dangling bonds and resulting in the large threshold voltage shift. And the energy is different between red and green light, so the amount of degradation for a-Si:H TFTs is also quite different. After a-Si:H TFTs stressed by gate bias for long time and with the same degree of red and green illumination in the meantime, they exhibit obvious difference under the gate terminals given positive and negative electric bias.
In AC stress, a-Si:H TFTs stressed by gate bias of 0~+30 V in different frequency, the threshold voltage shifts of devices don’t show obvious difference for different frequency. After a-Si:H TFTs stressed by gate bias and with green light illuminance at the same time, the threshold voltage shift is increased, but it still doesn’t relate to the AC signal frequency. At the gate bias of -30~0 V, the degradation mechanisms of devices are similar to DC stress ones, but the threshold voltage shift is smaller than that with DC stress. Due to in the one period of AC signal, the charge trapping would occur only in the high voltage magnitude of one cycle time. However, a-Si:H TFTs stressed by gate bias of -30~0 V with green light illuminance at the same time, the amount of threshold voltage shift is smaller than that only stressed by gate bias of -30~0 V.

誌謝 i
摘要 ii
Abstract iii
目次 v
表目次 vii
圖目次 viii
第一章 簡介 1
1.1 背景介紹 1
1.2 研究動機 3
1.3 文獻探討 4
1.4 論文架構 5
第二章 實驗內容 6
2.1 液晶顯示器的工作原理 6
2.2 氫化非晶矽薄膜特性 8
2.3 非晶矽薄膜電晶體結構介紹 9
2.4 非晶矽薄膜電晶體製程與電極定義 11
2.5 非晶矽薄膜電晶體退化機制介紹 12
2.6 薄膜電晶體各種電性參數之萃取 13
2.6.1 臨界電壓(threshold voltage，Vth)之定義 13
2.6.2 遷移率(mobility，μFE)和轉導(Gm)定義 13
2.6.3 導通電流(Ion)與漏電流(Ioff)定義 14
2.6.4 次臨界擺幅(subthreshold swing) 14
2.7 量測系統介紹 15
3.1 外加光源之條件 16
3.2 閘極施加直流電壓與交流訊號應力之參數 17
3.3 靜置時間之方法 18
第四章 結果與討論 19
4.1 應力結束後加入靜置時間之測試 19
4.2 不同直流電壓應力與紅綠光照度應力測試 21
4.2.1 直流電壓+30 V與紅綠光照度應力之測試 21
4.2.2 直流電壓-30 V與紅綠光照度應力之測試 22
4.3 不同直流電壓與紅綠光同照度且加長應力時間測試 32
4.3.1 直流電壓+30 V與紅綠光同照度應力加長應力時間之測試 32
4.3.2 直流電壓-30 V與紅綠光同照度應力加長應力時間之測試 33
4.4 交流訊號的應力測試 40
第五章 結論 44
參考文獻 46

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