Studies on the formation of source and drain in low temperature polycrystalline silicon thin film transistors

Abstract

The source and drain regions were formed successfully by dopant induced crystallization method for top gate poly silicon thin film transistors. It was found that the resistance of source and drain varies with respect to dopant concentration and the grain boundary influence on resistance at different doses was intensively studied in this work. In the present study, boron was doped by ion mass doping (IMD) and PECVD and the resistance of 230 Ω was the doping condition of 2 keV 1 min and 17 keV 10 min in ion mass doping method. Thin film transistor by DIC exhibited a field effect mobility of 56 cm2/V s, leakage current of 4.1 × 10−11 A, slope of 0.84 V/dec, Ion of 2.7 × 10−4 A, Vth of −6.5 V at Vd = 10 V In crystallization of in situ boron doped a-Si, 80 Ω in resistance was obtained at 1000 Å. N type poly Si of 1000 Å has 270 Ω in in-situ doping method. In-situ doped a-Si deposited by PECVD was further doped by using IMD. And the resistance was lowered by 10–20 Ω. Bottom gate thin film transistors fabricated by metal induced lateral crystallization (MILC) exhibits a field effect mobility of 26 cm2/V s, leakage current of 1.34 × 10−10 A, slope of 0.7 V/dec, Ion of 1.02 × 10−4 A, Vth of 4.5 V at Vd = 10 V.