Abstract
Hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) are widely used in active matrix flat panel electronics such as liquid crystal displays (LCDs), solid-state X-ray imagers, and more recently, organic light emitting displays (OLEDs). With a-Si:H TFTs, reproducible device characteristics that suit a number of applications can be obtained over a large substrate area using a simple low cost fabrication process. This makes a-Si:H TFT technology very attractive. However, low field effect mobility and electrical degradation restrict the use of a-Si:H TFTs as pixel drivers. On the other hand, hydrogenated microcrystalline silicon (μc-Si:H) has recently received considerable attention as a viable alternative to its amorphous counterpart for large-area applications. However, people studying on microcrystalline silicon TFTs will encounter an issue that the leakage current of TFTs is about 100pA which is a very high value if to be used as a switching TFT for AMOLED display. In this present thesis, we focus on the mechanism of the leakage current in microcrystalline TFTs. In our work, we use plasma enhanced chemical vapor deposition (PECVD) to fabricate deposition of microcrystalline silicon (uc-Si) film successfully. Through plasma treatment at surface of gate dielectric, we has grown the uc-Si with high crystallization. And we investigate the mechanism of leakage current in uc-Si TFTs and find a way to suppress that. Finally, we compare with uc-Si deposited by ICP-CVD. And the different characteristics of uc-Si TFTs was observed between the ICP-CVD and PECVD.