旋塗式有機主動層薄膜電晶體製程研發

Abstract

旋塗式有機薄膜電晶體有利於大面積且低成本的元件製作。此篇論文的研究目標為評估製造旋塗式有機薄膜電晶體的可行性。在本論文中，我們致力於P3HT的電特性討論，製程的研究以及有機薄膜電晶體的電特性探討。P3HT是一種半結晶的物質，用P3HT所做成的薄膜電晶體其載子移動率(mobility)受制於非結晶區域。從電晶體的電特性測量中，我們發現元件受到氧氣的作用，使得電晶體的臨界電壓(threshold voltage)與有機薄膜的導電性(conductivity)會增加。我們從有著Ni金屬電擊和top-contact結構的電晶體中得到了最佳的元件載子移動率，探討其原因，是由於較好的晶體結構與較低的金屬電擊接觸電阻(contact resistance)所造成。此外我們發現載子移動率會隨溫度升高而增加，這證實了載子在P3HT中可以藉由hopping的載子傳導機制來解釋。我們也發現沒有保護層的薄膜電晶體其電特性會隨時間的增加而產生劣化。在實驗中我們發現旋塗式的有機薄膜需要定義(pattern)以隔離元件，否則元件的絕緣層會因為有機層的污染而造成不必要的漏電產生，如此一來元件的電特性會跟著變差。

Organic thin film transistors made by Spin-Coating method with solution processable conjugated polymers have potential advantages for fabricating low-cost, large area devices. The goal of this study was to evaluate the feasibility of Spin-Coating method in fabricating organic thin film transistor with solution processable conjugated polymers. In this thesis, we emphasize the electrical characteristics of poly-3-hexylthiophene (P3HT), investigation of spin-coating process parameters and the electrical characteristics of OTFT with P3HT active layer. P3HT is semi-crystalline; the mobility is limited by amorphous part of P3HT. We have measured conductance, mobility, and ON-OFF current ratio of OTFTs. The best mobility of P3HT OTFT was obtained with a top-contact structure with Ni S/D contacts as a result of a good P3HT molecular morphology and low S/D contact resistance. And we found that the mobility is thermal activated (an evidence for hopping transport mechanism). In addition we found that the conductivity of P3HT film and threshold voltage of OTFT increases when the oxygen molecular is interacted with the P3HT film. A degradation of OTFT without a passivation layer was observed. For a good OTFT performance the organic active layer is needed to be patterned to reduce the gate leakage current.