氨氣電漿處理對複晶矽薄膜電晶體之電特性影響探討

Abstract

利用複晶矽薄膜電晶體(poly-Si TFTs)製作畫素元件及週邊驅動電路並將它積體化於大面積玻璃基板已成為未來製造主動式矩陣液晶顯示器的趨勢。目前複晶矽薄膜電晶體的異常漏電流是一個待解決且刻不容緩的議題。在本論文中，我們使用氮化矽(Si3N4)當作底部閘極之絕緣層，探討經氨氣電漿處理後氫原子與氮原子能夠累積在電晶體的通道內之效應，如此可進一步在汲極接面中填補通道的缺陷數量，可更有效降低元件漏電流之情形。除此之外，我們利用表面電位顯微鏡(KFM)來描述經氨氣電漿處理前後汲極接面能帶圖的變化情形，且此與複晶矽電晶體的異常漏電流有關聯。另一方面，我們也探討了長時間作氨氣電漿處理後，對複晶矽薄膜電晶體電特性之影響。對離子而言要穿透氮化矽薄膜是困難的。因此，此效應造成使用氮化矽與二氧化矽作為複晶矽電晶體的閘極絕緣層之不同行為。

Utilizing polycrystalline silicon thin-film transistors (poly-Si TFTs) as pixel switching elements and peripheral driver circuits is the future trend for manufacturing active-matrix liquid-crystal displays (AMLCDs). Currently, the anomalous leakage current of poly-Si TFTs is an important issue. In this thesis, we used Si3N4 as the insulator of bottom-gated TFTs to investigate the effects of nitrogen and hydrogen radicals accumulated within the channel by NH3 plasma treatment. A reduction of the leakage current was observed because of effectively defect reduction in the drain junction. Furthermore, variations of the profiles of energy band in the drain junction before and after NH3 plasma treatment are characterized by Kelvin Probe Force Microscope (KFM), and are used to associate with the anomalous leakage current of poly-Si TFTs. On the other hand, the influence of long-time NH3 plasma treatment on the electrical characteristics of poly-Si TFTs is studied. It is hard for atomic ions to penetrate into the Si3N4 layer. Therefore, the effect results in the different behaviors of poly-Si TFTs with Si3N4 and SiO2 as the gate insulators.