铟镓锌氧薄膜晶体管的制备及其性能研究

发布时间：2018-09-14 18:19

【摘要】：近年来,氧化物半导体薄膜晶体管在电子工业领域的应用越来越广泛。随着显示技术的高速发展,传统的以非晶硅为主体的晶体管器件已经不能满足现有显示技术的需求,而IGZO-TFT(铟镓锌氧薄膜晶体管)的出现,很好的解决了这一难题。由于IGZO的导电输运通道主要是由相邻金属原子之间球对称分布的s轨道相互重叠而形成的,所以即使是非晶状态,也能使IGZO-TFT薄膜晶体管保持良好的工作性能。而且,IGZO薄膜的非晶特性意味着能在较低温度下制备晶体管,以上特性非常有利于实现透明的柔性显示器。本论文采用射频磁控溅射法制备IGZO薄膜,通过X射线衍射(XRD)和能量散射谱(EDS)分析薄膜结构情况,并以IGZO薄膜为有源层材料制备了薄膜晶体管。文中讨论了薄膜的工艺优化和器件的结构调整对提高薄膜晶体管的性能的影响,本文的主要内容如下:本文对薄膜工艺的改进方面进行了探索,在带有二氧化硅覆盖层的硅片上生长IGZO薄膜,首先研究了退火气氛对IGZO-TFT性能的影响,实验发现在空气中退火的TFT器件性能最佳。其次,在对退火温度的讨论中,发现450oC下退火的晶体管展现出了良好的开关特性和稳定的饱和电流,迁移率高达到了4.23 cm2V-1s-1。此外,研究表明有源层更薄的TFT器件整体性能比较好,因为随着有源层厚度的降低,内部的电子散射现象降低,沟道等效电阻减小。另外随着沟道宽长比W/L的增大,TFT性能是逐渐提升的。实验还比较了用不同金属材料(Au、Cu、Al)作为源漏电极对器件性能的影响。研究表明,Cu和Al作电极较容易被氧化,使其接触电阻增大,从而导致TFT性能弱于Au电极的TFT器件性能。对使用不同绝缘层的IGZO-TFT的结果表明,SiNx明显优于SiO2,这归功于SiNx能使电介质层与沟道层之间陷阱浓度降低。本文还研究了退火对TFT器件性能的影响,发现退火可以使TFT器件的迁移率从1.48 cm2 V-1s-1上升到15.8 cm2 V-1s-1。XPS能谱分析结果表明退火能降低薄膜内部的氧空位缺陷浓度,从而明显提高TFT器件的迁移率和降低其阈值电压。最后,我们还检测了退火器件的稳定性和均一性,测试结果显示退火之后的器件性能都非常稳定。
[Abstract]:In recent years, oxide semiconductor thin film transistors have been widely used in the electronic industry. With the rapid development of display technology, traditional transistor devices based on amorphous silicon can no longer meet the needs of existing display technology. The emergence of IGZO-TFT (Indium Gallium Zinc Oxygen Thin Film Transistor) has solved this problem well. Because the conductive transport channels of IGZO are mainly formed by the overlap of spherically symmetrical s-orbits between adjacent metal atoms, even in the amorphous state, IGZO-TFT thin film transistors can maintain good performance. Moreover, the amorphous characteristics of IGZO thin films mean that transistors can be fabricated at lower temperatures, and the above characteristics are non-crystalline. In this paper, IGZO thin films were prepared by RF magnetron sputtering. The structure of the thin films was analyzed by X-ray diffraction (XRD) and energy scattering spectroscopy (EDS). Thin film transistors were fabricated by using IGZO thin films as active layers. The main contents of this paper are as follows: In this paper, the improvement of thin film technology is explored. IGZO thin films are grown on silicon wafers with silicon dioxide coating. Firstly, the influence of annealing atmosphere on the performance of IGZO-TFT is studied. It is found that the performance of TFT devices annealed in air is the best. In the discussion of temperature, it is found that the transistors annealed at 450oC exhibit good switching characteristics and stable saturation current, and the mobility is as high as 4.23 cm2V-1s-1. In addition, the study shows that the overall performance of TFT devices with thinner active layer is better, because with the decrease of the thickness of active layer, the internal electron scattering phenomenon decreases and the channel equivalent electricity decreases. In addition, the TFT performance is improved gradually with the increase of channel width ratio W/L. The effects of different metal materials (Au, Cu, Al) as source and drain electrodes on the performance of TFT devices are also compared. The results show that Cu and Al as electrode are easier to be oxidized, resulting in the increase of contact resistance, which leads to the weaker TFT performance than that of Au electrode. The results of IGZO-TFT with different insulating layers show that SiNx is superior to SiO2, which is attributed to the fact that SiNx can reduce the trap concentration between dielectric layer and channel layer. The results show that annealing can reduce the oxygen vacancy defect concentration in the film, thus significantly improving the mobility of TFT devices and lowering its threshold voltage.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN321.5

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