Study On Preparation And Properties Of Indium Gallium Zinc Oxide Thin Film Transistor

In recent years, oxide semiconductor thin-film transistors(TFTs) are finding wider and wider application in the field of electronic industry. With the rapid development of display technology, since traditional transistors made of amorphous silicon cannot have satisfied the requirements of available display technology, the emergence of the IGZO TFTs well solved this problem. The electricity channel of IGZO materials is mainly formed by overlapping ns orbitals spherically symmetric distribution between adjacent metal atoms, so IGZO TFTs can keep work good performance even if they are amorphous state. In addition, the amorphous nature of IGZO film means that it can be prepared at low temperatures, which is very advantageous to obtain flexible transparent display.In this work, the IGZO thin films have been deposited by radio frequency magnetron sputtering technique. The structures of the deposited thin films have been analyzed by X-ray Diffraction(XRD) and Energy Dispersive Spectroscopy(EDS). TFTs with amorphous IGZO thin films channel layer have been fabricated. In order to prepare better performance of thin film transistors, many experiments have been done to optimize the properties of thin films and adjust the structures of device. The main content of this work is as follows:The exploration of thin film technology improvements is stated in this thesis. The IGZO thin films have been deposited on the silicon wafer with silicon oxide layer, the influences of annealing atmosphere on performance of IGZO TFTs have been investigated, which proves that the devices annealed in the air have the best performance. The transistor device annealed in the air at 450 oC shows excellent switch characteristics, and keeps the stability of the saturation current, while the mobility is up to 4.23 cm2 V-1s-1. In addition, this research shows that the TFTs devices with thinner thickness active layer have the better performance, since the internal electron scattering phenomenon is reduced and the equivalent resistance of channel also decreases with lessen of the active layer thickness. Moreover, device performance is gradually improved with the increasing of channel’s W/L.We also compared the influences on device performance with different metal materials(Au, Cu, Al) as the source and drain electrodes. The studies indicate that the electrodes of Cu and Al are easily oxidized, and increase the contact resistance. The best performance of TFT was obtained with Au electrode. We have investigated the influence of various gate dielectrics on IGZO-TFTs, and the results show that the performance of TFT with SiNx as insulating layer is better than samples with SiO2 as insulating layer, since SiNx thin film can reduce the trap concentration between dielectric layer and the channel layer. The influence of annealing treatment on the TFT device performance has been studied, the result shows that the mobility of TFT device is up from 1.49 to 15.8 cm2 V-1s-1. X-ray photoelectric spectroscopy(XPS) results show that annealing can reduce the concentration of oxygen vacancy in the thin film. Finally, we also tested the stability and homogeneity of the annealed TFT device, the results indicate that the characteristics of annealed IGZO-TFT devices are fairly stable.