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Fabrication And Electrical Properties Of Oxide Thin Film Transistors

Posted on:2012-04-26Degree:MasterType:Thesis
Country:ChinaCandidate:X WangFull Text:PDF
GTID:2178330332993300Subject:Radio Physics
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In the 20th century, the emergence of the flat panel display technology has brought human beings into the information society. Since then the human society happened a qualitative leap. The core component of flat panel display is the thin film transistor (TFT), it is a field effect transistor device produced by thin film technology on the glass. In the active matrix liquid crystal display (AMLCD), it is still using amorphous silicon or polysilicon silicon thin film transistors as the switching unit. However, the amorphous silicon TFT has low field effect mobility, and it is photosensitivity. Whire polysilicon TFT's production process is complicated and costly, thus, the scope of their wider application is limited. If we use the semiconductor oxide as the active layer, not only we can get a higher mobility, bu also the device performance can be enhanced. And the manufacturing process is simple, low temperatures can also obtained, which shows a great prospect.In this paper, we studies transparent oxide TFTs, including ZnO, In2O3 and ZnSnO alloy thin film transistors. We used magnetron sputtering ZnO, In2O3 and ZnSnO films as the active layer to produce TFTs; insulating layer of SiO2 thin film is deposited by Plasma enhanced chemical vapor deposition. In the preparation process of ZnO-TFT and In2O3-TFT, the active layer is easy to form polycrystalline, there can be a large number of grain boundaries and oxygen deficiency, the ZnO-TFT and In2O3-TFT's performance have poor mobilitys,1.49 and 0.69 cm2/(V·s) respectively.We used amorphous alloy film ZnSnO as the active layer to produce TFT, the device has good electrical properties, the field effect mobility is up to 9.1 cm2/(V·s), on/off current is more than 104. After annealed in vacuum, the performances of the device have been significantly improved. We made transparent ZnSnO-TFT device using In2O3 transparent film to made the source and drain electrodes, the device has an excellent performance, the highest field effect mobility is up to 56.2 cm2/(V·s). The electrical properties of the devices including threshold voltage, current switching ratio were significantly improved compared to ZnO-TFT and In2O3-TFT. We tested the stability and uniformity of the device and found that ZnSnO-TFT has good uniformity. Whire scanned at different source drain voltages, the stability of device presented well.The ZnSnO film is amorphous just like the amorphous silicon thin film, so we used a simplified model of amorphous silicon TFT to simulate the ZnSnO-TFT characteristic curve. Almost all regions are in line with the well, which shows a model of amorphous silicon TFT can be used ZnSnO among the theoretical simulation.
Keywords/Search Tags:thin film transistor, zinc tin oxide, magnetron sputtering, annealing
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