A new a-Si TFT with SiO2/SiN/sub x/ gate insulator for 10.4-inch LCDs

Abstract

A novel a-Si TFT (thin-film transistor) with a composite gate insulator of CVD (chemical-vapor-deposited) SiO/sub 2//PE-CVD (plasma-enhanced CVD) SiN/sub x/ has been developed. This TFT has been applied to 10.4-in-diagonal LCDs (liquid crystal displays). Because of the high quality of CVD SiO/sub 2/, Vth drift, which was often observed after prolonged application of gate bias, was remarkably reduced compared to PE-CVD SiO/sub x/N/sub y/. Also, the degradation of subthreshold characteristics on a-Si TFT (often observed after long-term operation of LCDs at high temperature) was improved. Selective etching technologies of SiN/sub x/ against SiO/sub 2/, which is one of key issues in connection with obtaining high production yield, have been developed.<>