Electrical Characteristics of Low Temperature Polysilicon TFT With a Novel TEOS/Oxynitride Stack Gate Dielectric

Abstract—This investigation is the first to demonstrate a novel tetraethylorthosilicate (TEOS)/oxynitride stack gate dielectric for low-temperature poly-Si (LTPS) thin film transistors (TFTs), composed of a plasma-enhanced chemical vapor deposition (PECVD) thick TEOS oxide/ultrathin oxynitride grown by PECVD N 2 O-plasma. The stack oxide shows a very high electrical breakdown field of 8.4 MV/cm, which is approximately 3 MV/cm larger than traditional PECVD TEOS oxide. The field effective mobility of stack oxide LTPS TFTs is over 4 times than that of traditional TEOS oxide LTPS TFTs. These improvements are attributed to the high quality N 2 O-plasma grown ultrathin oxynitride forming strong Si N bonds, as well as to reduce the trap density in the oxynitride/poly-Si interface