Preparation And Characteristics Of Amorphous Indium Tin Zinc Oxide Thin Films

Transparent conducting oxides (TCOs) thin films have been widely used in microelectronics industry due to its excellent optical and electrical characteristic. The indium tin oxide (ITO) thin films and other polycrystalline films have been widely applied at present. However, its characteristic can be affected by the thickness of films and environment. At present, the study of amorphous semiconductor transparent conductive film is limited. Amorphous indium tin zinc oxide thin films (ITZO) has received great attention because its excellent characteristic and stability. Compared to conventional polycrystalline oxide film, ITZO film has many advantages such as the simple preparation methods, the high transmittance and the excellent electrical properties. It is known that the ITZO films can be used as the active layer and electrode layer. The research on ITZO transparent conductive film is few up to now. In this paper, the ITZO films were prepared by magnetron sputtering in different RF power, working pressure and different thickness, the properties of electrical, optical and structural were studied. We also fabricated homojunction ITZO-TFT by using ITZO films.(1) Amorphous ITZO films were deposited on glass substrate using the magnetron sputtering at the room temperature. The effects of the RF power on the properties of ITZO films were investigated. The film has a better characteristic with a resistivity of 3.381×10-4Ω·cm, a carrier concentration of 6.45×1020 cm-3 and a mobility of 24.14 cm2V-1s-1 at the RF power of 80 W. The average transmittance of ITZO films is more than 84%.(2) The effect of working pressure on the properties of ITZO film was investigated. As the working pressure increased, the resistivity of ITZO film decreased, and the carrier concentration increased. When the working pressure was 0.8 Pa, the ITZO film had a better characteristic with a resistivity of 3.66×10-4Ω·cm, a carrier concentration of 6.75×1020 cm-3 and a mobility of 26.06 cm2V-1s-1.(3) As the thickness of ITZO film was increased, the properties of ITZO film became better and better. As the thickness is 500 nm, the characteristic of ITZO film is better than the others. As the thickness was increased, the average transmittance was decreased. The reason for this phenomenon was light scattering, absorbing and reflecting caused by the increase of ITZO fims.(4) Homojunction ITZO-TFT was fabricated by magnetron sputtering on the silicon substrate at the room temperature. The active layers and the electrode layers were made by ITZO films. Homojunction ITZO-TFT have a good performance with a threshold voltage of 0.2 V, an on/off ratio of 2×10-6, a swing threshold of 1.9 V/decade and a mobility of 10.5 s-1cm2V-1. It implied that ITZO transparent conductive films can be used to prepare ITZO-TFT.