Thin Film Devices Based On Metal Oxide Materials

In recent years, Thin Film Transistor (TFT) has become a hot research topic, and has been widely used, it is expected to become the next generation of driver components of the displays. The research valve of TFT based on novel semiconductor material becomes more significant because of the discovery and further research of novel material.There are two kinds of semiconductor investigated in this paper:n-type amorphous Indium-Gallium-Zinc-Oxide (a-IGZO), which owns great research value; p-type Stannous Oxide (SnO), of which the potential is inestimable.(1) High performance amorphous indium gallium zinc oxide thin film transistors and process exploration.We chose bottom-gate structure as the fabrication process in our work by researching large amounts of literature about a-IGZO semiconductor and considering the actual situation of laboratory, Heavy doped P-type silicon (Si) worked as substrate and bottom gate, compact silicon oxide (SiO2) was then thermally grown on Si to act as dielectric layer. A-IGZO, as active layer, was sputtered to deposit on SiO2 film, the last step is to deposit titanium (Ti) on a-IGZO film, which works as source and drain electrode. Because the Si substrate was uniform doping and SiO2 surface was so smooth, the device had good stability and repeatability. We investigated several parameters influence on the a-IGZO TFT performance, such as thickness of a-IGZO film, thermal treatment and encapsulation treatment.Thermal treatment is a process to heat samples on a hot plate. The lattice vibrational in a-IGZO film gets strengthened, the atoms become more organized and the number of defects decreases accordingly. So the performance of device was improved in the paper. The impact of encapsulation on the devices mainly consists of two aspects:the one is to improve the stability of device by insulating the external factors; the other is to optimize the interface situation between active layer and encapsulation material, and to improve the device performance. We also paid attention to the influence of a-IGZO thickness on the device, which had a sharp deterioration when the active layer was thinner than 5 nm. But, with the aid of thermal treatment and encapsulation, the device performance regenerated dramatically. In addition to this, we also investigated the Electric Double Layers (EDL) TFT based on a-IGZO film, of which the performance was closely related to the electrolyte concentration. Finally, the EDL TFT was able to work under much low voltage (IV).(2) Fabrication process and technology research of Stannous Oxide TFT.Based on the latest literature research and considering the actual Lab situation, bottom-gated structure was chosen to be applied on SnO TFT. The fabrication process is similar to that of a-IGZO TFT. The substrate was glass Corning 7059, double layer metal palladium/titanium (Pd/Ti), as gate electrode, was deposited on the cleaned substrate by electron-beam evaporation. Ta2Os and SnO film were then grown orderly, acting as dielectric layer and active layer respectively, by sputter process. Finally, metal Pd, as source and drain electrode, was deposited on the active layer. Several parameters were investigated in this paper, such as structure of gate electrode, performance of Ta2O5 and choice of source and drain material. It is a great way to solve the test problem, and improving Ta2Os electric insulativity, by thermal treatment, is essential to device performance. Metal palladium owning high working function, as source and drain electrode, could form ohmic contact with p-type SnO, to improve the performance of SnO TFT.