| Thin film transistors(TFTs)are semiconductor devices widely used in flat panel displays.Currently,large size high resolution high refresh rate panels have an increasingly important market position,which puts higher demands on the performance of TFT devices.The traditional active layer and source-drain electrode materials can no longer meet the new display requirements for mobility and delay,and new InSnZnO materials are attracting attention due to their higher carrier mobility than traditional In Ga Zn O materials.The copper process is also desired for reducing the wiring resistance and thus the RC delay of the panel due to the low resistivity properties of the material itself.In this thesis,research on active layer materials and source-drain electrode materials is carried out with the goal of preparing TFT devices with high mobility and low RC delay for the future demand of large size high resolution high refresh rate panels.The details are as follows.(1)Firstly,InSnZnO active layer was prepared by co-sputtering,and the commonly used ITOwas prepared by DC magnetron sputtering as the source drain electrode.The measured device mobility of 15.23 cm~2/V·s demonstrates the potential of InSnZnO for future display applications,but the contact resistance of the tested ITO source drain is as high as 48 K?,which can cause high RC delay and thus affect the display effect.(2)In order to reduce the contact resistance of the device,the attention was directed to copperwith low resistivity.We prepared a TFT device using copper as the source-drain electrode,and used stepwise annealing to address the problem of copper diffusion and oxidation at high temperatures.The device mobility was increased to 19.88 cm~2/V·s,and the contact resistance was reduced to 10.128 K?due to the material change.However,due to the diffusion of copper,the transmission line method was used to fit the calculation and found that the source drain electrode did not form a good ohmic contact with the InSnZnO active layer,plus the 5.4V offset of the positive bias stability test was much worse than that of the ITO electrode,and the device lost its switching performance after one week.The device was found to lose its switching performance after one week.(3)In order to prevent the adverse effects of copper diffusion,a self-assembled monomolecular layer of Methyltriethoxysilane prepared by the vapor-phase method is introduced as the diffusion barrier layer of copper.Compared with the traditional"sandwich"or stacked metal structure,this process has the advantages of ultra-thin,low cost,low preparation temperature,no additional process introduced,no damage to the active layer,and the self-assembled layer prepared by the vapor-phase method is flatter and more suitable for mass production than that prepared by the liquid-phase method,with no impurity residue in solution and friendly to the environment.After the test,it was found that the mobility was as high as 24.42 cm~2/V·s,and the copper device formed a good ohmic contact with a contact resistance of only 4.1 K?.The offset of 3.4 V in the positive bias stability test for copper diffusion was better than that of the unblocked device,and the stability performance was comparable to that of the ITO electrode device,which still had good performance after 60 days.The experimental results show that the self-assembled single molecule layer prepared by the vapor phase method can be used as a diffusion barrier layer for copper to overcome the disadvantages of copper diffusion and improve the device performance.It is compatible with the in-line process and has various advantages,which fully demonstrates the promising application of the self-assembly process in the field of flat panel display.. |
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