The Study Of The Preparation And Property Of Indium Gallium Zinc Oxide Thin Film Transistor

Amorphous indium gallium zinc oxide(IGZO) has the characteristics of high mobility, good uniformity and high optical transmittance in the visible region, is expected to achieve a transparent and flexible display. It is the most widely used as the channel material in the oxide thin film transistor. In this paper, IGZO films were deposited by DC magnetron sputtering and used as the active layer in IGZO-TFT. The main work of this paper is the following aspects:(1) IGZO films were deposited by DC magnetron sputtering. The optical transmittance of IGZO films was analyzed under different conditions(sputtering power, sputtering time). The results showed that the optical transmittance of IGZO films in the visible region maintains at about 80%. The film deposited under 180 W has the highest transmittance(89.73%). The surface morphology of IGZO films under different sputtering power, sputtering pressure and oxygen partial pressure were observed by SEM and AFM. The SEM images showed that IGZO film has a smoother surface and fewer defects from 180 W to 200 W, under the sputtering pressure of 2 mTorr. It can be seen that the surface of thin film is smoother and the roughness is smaller with the increase of oxygen partial pressure from the AFM images. The AFM images also showed that organic thin film can improve the surface defects on the substrate itself and the smoothness of organic thin film is better for the deposition of IGZO film. At last, IGZO films deposited by DC magnetron sputtering were amorphous through the XRD test.(2) IGZO-TFT devices based on a bottom-gate top-contact were prepared with PMMA, PVA as insulating layer formed by spin coating and IGZO as active layer deposited by DC magnetron sputtering. The electric properties of IGZO-TFT devices were studied under different conditions including with oxygen partial pressure, the buffer layer, the thickness of insulating layer and annealing temperature. For IGZO-TFT devices with PMMA as insulating layer, the results showed that the increase of oxygen partial pressure will cause the carrier mobility first increases and then decreases. We found the device has the highest carrier mobility(0.84 cm2·V-1·s-1) under oxygen partial pressure of 1.2%. Using low power magnetron sputtering thin IGZO buffer layer(5 nm) can reduce the electron trap and film roughness, optimize the interface between the insulating layer and the active layer, improve the quality of film forming of the active layer. For IGZO-TFT devices with PVA as insulating layer, the results showed that the carrier mobility and the current on/off ratio increases with the increase of the thickness of the insulating layer. The performance of the device is better than the device which used PMMA as the insulating layer. The electrical characteristic of TFT is best under the insulating layer thickness of 800 nm. The carrier mobility is 11.4 cm2·V-1·s-1, the on/off ratio is 9.6×102 and the threshold voltage is 9.7 V. The study also showed the annealing treatment will improve the performance of the device. We found the device has the highest carrier mobility(24.8 cm2·V-1·s-1) and the highest on/off ratio(3.5×103) under the annealing temperature of 200℃.