INFLUENCE OF LOW-TEMPERATURE ANNEALING ON THE DIELECTRIC CHARACTERISTICS AND FINAL PARAMETERS OF SIO2 MIS THIN-FILM TRANSISTORS

Hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) h ave been prepared using PECVD SiO2, deposited under different depositi on conditions, as the dielectric. The layers were evaluated to determi ne the best deposition regime with regard to the index of refraction a nd electrical insulation properties. This regime was found to be a dep osition temperature of 200 degrees C, rf power density of 145 mW cm(-2 ), and a flow rate ratio of O-2 to a 10 vol.% mixture of SiH4 in H-2 i n the interval 7-25. The devices were characterized by measuring the e ffective mobility, the threshold voltage, and their behavior in the su b-threshold regime. The influence of low-temperature annealing on thes e parameters was determined. The best results were obtained when the d evices were annealed in the temperature interval 250-300 degrees C. (C ) 1997 Elsevier Science S.A.