Fabrication And Properties Of Indium Oxide Based Thin Film Transistor

Thin film transistors (thin film transistor, TFTs) are the key components in flat panel displays. With the development of the science, the trend of flat panel displays is high capacity, high resolution, high drive,3D and large size. In the industry, the mobility of amorphous silicon TFTs is less than 1cm2/V s, and the uniformity of polycrystalline silicon TFTs is poor. Moreover, these Si-based TFTs are opaque in the visible wavelength region, which restricted the development of thin film transistor. Due to high mobility and transparency, the oxide TFT has attracted much attention. In order to meet the requirement of the modern display technology and 3D display, there is a hot issue to be solved, which is the way to improve the mobility of thin film transistors. In this work, In2O3:Li TFT、In0.8Zn0.2O:Li TFT and In0.67Zn0.33O:Li TFT were fabricated. The high performance of indium oxide based TFT devices were obtained by optimizing the experimental parameters. Major works as follows:(1) In2O3:Li TFTs with bottom gate structure were produced by radio frequency magnetron sputtering. The effects of annealing temperature, the active layer thickness and the oxygen gas flow rate on the electrical properties of TFTs were investigated, respectively. The experimental results indicated that the TFTs with an 30nm In2O3:Li films, annealed at 200℃ and oxygen gas flow rate of 2sccm, have the best electrical properties:a field effect mobility of 14.6cm2/V s, an on/off current ratio of 9.0×106 and a threshold voltage of 5.2V.(2) The Ino 8Zno.20:Li TFTs were fabricated on SiO2/Si by magnetron sputtering. The effects of the active layer thickness, argon gas flow rate, annealing temperature, and annealing atmosphere on the electrical properties of TFTs were studied, respectively. Meanwhile, the TFT device with double active layer structure was fabricated. The experimental results indicated that the TFTs with an 30nm In2O3:Li films, argon gas flow rate of 30scccm and annealed at 950℃ in the oxygen atmosphere, have the best electrical properties:a field effect mobility of 56.1cm2/V s, an on/off current ratio of 5.1×106 and a threshold voltage of 2.0V. Compared to the single layer structure, the double-active layer structure can improve the electrical properties of TFT, and the mobility of the TFT was 62.1cm2/V s.(3) The In0.67Zn0.33O:Li films were deposited on quartz by magnetron sputtering, and the effect of annealing temperature on the morphology of Ino.67Zno.330:Li thin films was investigated. In0.67Zn0.33O:Li TFTs were fabricated on SiO2/p-Si substrates, the effects of the oxygen gas flow rate, the sputtering power, the active layer thickness and annealing temperature on the electrical properties of TFTs were investigated, respectively. The experimental results shows the TFT with an 30nm In0.67ZnO.330:Li films, no oxygen gas flow rate, sputtering power of 100W and annealed at 950℃,exhibited the best electrical properties:a field effect mobility of 80.4cm2/V s, an on/off current ratio of 4.0×106 and a threshold voltage of 4.1V. The electrical property of the TFT device is one of the best electrical properties in the papers. Without any protection, the mobility of the TFT decreased slightly to 73.1cm2/V s and showed a good stability in the atmosphere.