双有源层a-IGZO薄膜晶体管的特性仿真

发布时间：2018-05-12 08:42

本文选题：薄膜晶体管 + 双有源层　；参考：《江南大学》2017年硕士论文

【摘要】：现如今平板显示技术正在急速发展,而薄膜晶体管(thin film transistor,TFT)作为其核心组成器件更是受到众多研究者的关注。在此前非晶硅TFT、多晶硅TFT作为像素开关得到广泛应用,但是自从稳定性好、低温制备性能良好、均匀性好、透光率高的非晶铟镓锌氧化物薄膜晶体管(a-IGZO TFT)被研制出来之后,便迅速占领市场。然而随着技术的发展,视频格式的变化对设备的分辨率、清晰度的要求日益增高,现如今的设备已经满足不了广大用户的强烈需求,便不断地有双层有源层TFT被研究出来。2005年,美国的Dehuff研究小组研制出非晶铟锌氧化物薄膜晶体管(a-IZO TFT),其迁移率高、开态电流高、低温制备性能也较好,其缺点便是稳定性不高。因此本文在此基础上,对TFT器件采用双层有源层结构,前沟道为a-IZO材料,利用a-IZO的高迁移率的特性提高TFT器件的开态电流;背沟道为a-IGZO材料,利用a-IGZO的低关态电流的特性提高TFT器件的开关电流比。本文的研究重点如下:1)本文对双有源层TFT器件的两种有源层材料的厚度组成进行研究,即设定双层有源层TFT的有源层的总厚度为一定值,改变前沟道为a-IZO材料、背沟道为a-IGZO材料的厚度比,根据其厚度比的变化,研究其双有源层TFT的导电机制,以及有源层的载流子浓度的变化对TFT器件的电学特性的影响。并且对比讨论这两种材料的厚度在怎样的状态下才能使TFT的器件性能达到最佳。研究得出,当双层有源层TFT器件的前沟道材料a-IZO的厚度为5nm(a-IZO与a-IGZO的厚度比为5/35)时,TFT器件的开关电流比达到最大值、阈值电压最为接近0、亚阈值摆幅也为所研究的所有厚度比例TFT中的最小值、其稳定稳定性也佳。并且研究过程中发现,双层有源层TFT的电学特性普遍比单层有源层TFT的特性要好。2)态密度模型(density of states,DOS)是a-IGZO半导体与a-IZO半导体的电学特性的一个重要表征,在众多研究者对其特性的模拟研究中,均对DOS模型中的参数进行了研究。由于a-IZO较a-IGZO半导体相比,只是缺少了Ga元素,因此本文便结合现有的a-IGZO DOS模型对两种有源层材料的态密度模型参数进行研究。主要讨论其特定参数的变化对TFT器件的影响程度。仿真结果表明:a)前沟道a-IZO的导带尾态在E=EC时的nta浓度的增加,会导致双有源层TFT器件的开态电流的减小、阈值电压的增加;前沟道a-IZO的导带尾态的特性斜率wta的增加,会导致导带尾态的面积增加以及TFT器件的开态电流的减小、阈值电压的增加、亚阈值摆幅的减小。b)背沟道材料a-IGZO材料的氧空位态的变化对TFT器件的特性影响巨大,并且氧空位态与费米能级的相对位置对TFT器件也会有影响。因此前沟道的导带尾态(即阳离子的空轨道)对TFT器件的整体影响巨大,而背沟道的缺陷态对TFT器件的影响更加不可忽略。
[Abstract]:Now flat display technology is developing rapidly, and thin film transistor (TFT), as its core component, is paid more and more attention by many researchers. Before the amorphous silicon TFT, polycrystalline silicon TFT is widely used as a pixel switch, but since the stability is good, the low temperature preparation performance is good, the uniformity is good, the transmittance is good. After the high amorphous indium and gallium oxide thin film transistor (a-IGZO TFT) has been developed, the market is rapidly occupied. However, with the development of technology, the changes in video format have increased the resolution and clarity of the equipment. Nowadays, the equipment has been unable to meet the strong needs of the broad users, and there is a double layer of active layer TF. T has been studied for.2005 years. The Dehuff research team in the United States developed amorphous indium oxide thin film transistor (a-IZO TFT), which has high mobility, high open state current and good low temperature preparation performance. The disadvantage is that the stability is not high. Therefore, on this basis, the TFT device uses a double layer active layer structure, the front channel is a a-IZO material and a is used. The high mobility of -IZO improves the open state current of the TFT device; the back channel is a a-IGZO material, and the switching current ratio of the TFT device is improved by the characteristics of the low off state current of the a-IGZO. The focus of this paper is as follows: 1) this paper studies the thickness composition of the two active layer materials of the double active layer, that is, setting the double layer active layer TFT The total thickness of the active layer is a certain value, and the thickness ratio of the front channel is a-IZO material and the back channel is the thickness ratio of the a-IGZO material. According to the change of the thickness ratio, the conductive mechanism of the double active layer TFT and the influence of the carrier concentration of the active layer on the electrical characteristics of the TFT device are studied. And the thickness of the two materials is compared and discussed. It is concluded that when the thickness of the front channel material a-IZO of the double active layer TFT device is 5nm (a-IZO and a-IGZO thickness ratio 5/35), the switching current ratio of the TFT device is maximum, the threshold voltage is closest to 0, and the sub threshold swing is also in all the thickness proportion TFT studied. In the course of the study, it is found that the electrical properties of the double layer active layer TFT are generally better than that of the single layer active layer TFT (.2). The density of states (DOS) is a important characterization of the electrical properties of a-IGZO semiconductors and a-IZO semiconductors, and in the simulation of the characteristics of a large number of researchers. All the parameters in the DOS model are studied. As compared with the a-IGZO semiconductor, a-IZO is only missing the Ga element, so this paper combines the existing a-IGZO DOS model to study the parameters of the density model of the two active layer materials. The main discussion is about the influence of the change of the specific parameters on the TFT device. The simulation results show that: before a) The increase of the NTA concentration of the tail state of the channel a-IZO leads to the increase of the NTA concentration at E=EC, which will lead to the decrease of open state current and the increase of the threshold voltage. The increase of the characteristic slope WTA of the tail state of the front channel a-IZO leads to the increase in the area of the tail state of the guide band and the decrease of the open state current of the TFT device, the increase of the threshold voltage and the subthreshold value. The decrease of the swing.B) the change of oxygen vacancy in the a-IGZO material of the back channel material has great influence on the characteristics of the TFT device, and the relative position of the oxygen vacancy state and the Fermi level will also affect the TFT device. Therefore, the guide band tail state of the front channel (the cation empty orbit) has a great influence on the TFT device, and the defect state of the back channel is TFT The effect of the device can not be ignored.

【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN321.5

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