| As the core device of FPD, TFT is the key to influence the performance. The IGZO-TFT is widely studied by domestic and overseas scholars due to its low temperature process, good uniformity, high light transmission and it can be deposited on flexible substrates compares to the traditional a-Si-TFT. In this article, we studied on the material characteristics of a-IGZO, and then the model of IGZO-TFT was built. Building further on this foundation, we studied the IGZO-TFT with double active layers. The parameters were optimized and the interface between the two active layers was analyzed to give the reference to the practice.At first, we used MS for material simulation of ZnO, ZnO with oxygen vacancies, line alternated IGZO and atom alternated IGZO. By studying on the band structures and DOS, the influence of each atom on the band structure and DOS were drawn. We found that the band minimum of IGZO mainly consists of the metal atoms' s orbitals, and the In 5s orbitals contribute the largest. In the other hand, the oxygen vacancies would be suppressed by the introduction of Ga. Because the In 5s orbitals had the characteristics of the spherically symmetric, IGZO material was insensitive to structural deformation.Then, based on the DOS model we used TCAD for simulation of IGZO-TFT. And the simulation results were in agreement with experimental data, which proved the model was correct. The IGZO-TFT was optimized afterwards. We found that IGZO-TFT with 20 nm active layer, 30?m channel length and 60 nm insulating layer had the best performance. And the actual process structure was presented.At last, based on the above model we simulated the IGZO-TFT with double active layers. The effect of the thickness variation of each active layer and the interface between two active layers were studied. The high performance device with Vth=-0.89 V, SS=0.27, Ion/Ioff=6.98×1014 was obtained in this ideal case. And when the interface was at the edge of the main conductive area, the device had best performance. |
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