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Preparation And Characteristics Research Of High Mobility Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors

Posted on:2014-01-15Degree:MasterType:Thesis
Country:ChinaCandidate:S S LiFull Text:PDF
GTID:2248330398959270Subject:Microelectronics and Solid State Electronics
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Thin film transistor (TFT) is a kind of field effect device, and it is composed of electrode layer, semiconductor layer and insulator layer. TFT is the key unit in liquid crystal display and active matrix organic light-emitting diode (AMOLED). At present, amorphous silicon or poly silicon thin film transistor is still used in displays as the switching unit. However, the amorphous silicon TFT has low field effect mobility, and it is hard to offer large current to drive the OLED. The production process of polysilicon TFT is complicated and costly, so it is hard to be produced in large area. All these problems limit the development of AMOLED. In recent years, great progress has been made in the research of oxide TFT, especially in the research of the transparent amorphous indium gallium zinc oxide. It is famous for its high mobility, good stability and good uniformity. It is expected to become the key unit of the next generation display technology. The preparation condition of the active layer and the effect of post-processing on the performance of TFTs are studied.(1) The IGZO-TFTs with different active layer thickness of16,33and44nm were produced. The effect of the indium gallium zinc oxide active layer thickness on the properties of the devices was studied. The threshold voltage shifted to the negative direction with different active layer thicknesse ranging from16nm to44nm. The TFT changes from enhancement mode to depletion mode, which is related to the decreasing resistance with increasing the thickness of the active layer, and a higher flow of electrons pass through the source and drain. The subthreshold swing increases gradually with the increase of film thickness, which is caused by the increase of trap density. The on-off current ratio above107is achieved. The field effect mobility is above11cm2V-1s-1. The devices show great combination property.(2) We prepared a set of devices under the same conditions, which were rapid annealed at various temperatures. It was found that the electrical performances of the IGZO-TFTs were highly sensitive to the annealing temperature. The field effect mobility and on-off current radios have greatly improved under the appropriate annealing temperature, and at the same time the threshold voltage decreases. The device shows best performance after annealed at300℃(3) We prepared amorphous IGZO-TFT for active layer with fixed oxygen partial pressure of4.76%、9.52%and20%. The effect of oxygen partial pressure on the TFT electrical properties was discussed. The field effect mobility and on-off current radio decreases with the increase of oxygen content. The threshold voltage and subthreshold swing increase at the same time. The oxygen vacancies are filled slowly with the increasing of oxygen content, which causes the decrease of carrier density. The active layer resistance increases highly.(4) We fabricated the TFTs using IGZO as source and drain electrodes. The influence of the active layer thickness on the properties of the devices was investigated. The kind of electrode materials has almost no effect on the properties of the TFT. The IGZO electrode has no prominent advantages compared with the ITO electrode.
Keywords/Search Tags:Thin film transistors, Indium gallium zinc oxide, Magnetron sputtering, Rapid annealing treatment
PDF Full Text Request
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