低溫多晶矽薄膜電晶體光漏電流的研究

Abstract

近年來液晶顯示器的需求急速升溫，中小尺寸高亮度高對比的顯示器需求也是成長近乎供不應求，例如在投影元件應用、行動通訊以及車用面板上都是。然而亮度提高相對的也會提高薄膜電晶體元件的光漏電流，此一漏電流的提高，會降低畫面顯示的對比度以及顯示顏色的偏差。因此降低或抑制元件在高亮度下的光漏電流是必須要的。 在此論文研究中，我們提出了三種降低光漏電流的方式。第一種是改變元件的緩衝層與主動層的載子產生/複和中心；第二種是採取吸光層來取代原本的緩衝層，主要此吸光層是要減少被光源的光到達元件的主動層而使得該區域內的電子電動對因吸光獲得能量，而產生漏電流；最後一種是使用不透光的金屬材料，使他在元件主動層下方將被光源遮住，這是個非常有效的方式，可惜的是此他仍有些邊際效應需要解決。在此文章裡，我們研究了這幾種抑制光漏電流的方法並觀察其在各個結構的漏電流變化，企圖想找處一種最適合的元件結構，當然，在此我們利用了低溫多晶矽的薄膜電晶體來完成研究。 在這篇論文，我們呈現了改變元件結構的實驗結果，接著我們還會針對各個結果進行討論。

The market for liquid crystal displays has been rapidly expanding in recent years. The demand for a high luminance and a high contrast ratio in liquid crystal displays (LCDs), such as small-medium LCDs for projection device, mobile displays and displays for cars, is continuing to grow and seems insatiable. However, high luminance would increase photo leakage current (PLC) in the TFTs, which diminishes the voltages that are held across the pixel electrodes, which in turn, would cause a low contrast ratio Consequently, it is necessary to suppress the PLC in LCDs with high luminosity. There are three schemes to suppress the PLC. First scheme is to vary the center of generated / recombined between the buffer layer and poly-Si active layer so that the electron-hole pairs which were excited by back light. Second one is using the light-absorption structure sot that less light can reach the active layers of TFTs. The last one is using light-shielding structure, here we employ the opaque material to shield the light, it is the most effective to cut-off the light from the light source. Unfortunately, this method still has some side effect that we will have detail discuss later. In this thesis, we focus upon those methods and have examined how the PLC changes depending upon structural parameters of TFTs and pursuit a desirable device structures of the TFTs. This work has been done for the TFTs with low-temperature poly-Si (LTPS). In this article, we present the experimental results of how to the PLC changes depending on the different structure parameters of the TFTs, such as shielding and absorbing materials under the active poly-Si layer. Then, we have some discussion of the results and conclusion.