【作者】 李帅帅；

【导师】 杨田林；

【作者基本信息】 山东大学 ， 微电子学与固体电子学， 2013， 硕士

【摘要】 薄膜晶体管(Thin Film Transistor, TFT)是由电极层、半导体层和绝缘层组成的场效应器件。它是组成液晶显示器(Liquid Crystal Display, LCD)和有源矩阵有机发光二极管(Active Matrix Organic Light Emitting Diode, AMOLED)驱动电路的核心部件。目前应用于显示器的开关元件仍为非晶硅TFT、多晶硅TFT等。但是,非晶硅TFT的场效应迁移率低,难以提供足够大的电流驱动OLED发光；多晶硅TFT的制造工艺复杂,成本高,均一性差,难以大面积生产。这些问题严重制约着新一代显示技术AMOLED的发展。近年来,氧化物TFT的研究取得了很大的进展,尤其是透明非晶铟镓锌氧化物薄膜晶体管(IGZO-TFT),它在载流子迁移率、稳定性、均匀性等方面都具有独特的优势,将有望成为下一代显示技术的核心驱动原件。本论文重点研究IGZO-TFT的制备条件以及后处理条件对器件性能的影响。(1)制备了有源层厚度分别为16、33、44nm的IGZO-TFT,研究了有源层厚度对器件电学性能的影响,发现IGZO厚度由16nm增加到44nm时,IGZO-TFT的阈值电压向负方向移动,TFT由增强型逐渐变为耗尽型,这是由于有源层厚度增加,引起电阻减小,导致更多的自由电荷从源极流向漏极；器件的亚阈值摆幅逐渐增大,这是由于陷阱密度增加所引起的；制备的器件电流开关比均高于107；场效应迁移率均高于11cm2V-1s-1.(2)在相同的条件下制备了一组器件,在不同的温度下进行快速退火处理,发现退火温度对IGZO-TFT性能的影响很大。在合适的退火温度下,器件的场效应迁移率和电流开关比均有较大幅度的提高,阈值电压也相应的减小。退火温度为300℃,器件的综合性能最佳。(3)在氧分压分别为4.76%、9.52%和20%条件下制备了非晶IGZO-TFT,讨论了氧分压对TFT电学性能的影响,结果发现随着氧气含量的增加器件的场效应迁移率、电流开关比均降低；闽值电压与亚闽值摆幅均增大。这是因为随着氧气含量的增加,氧空位逐渐被填充,导致载流子浓度降低,有源层逐渐由相对低阻转向高阻状态。(4)制备了以IGZO为源漏电极的TFT,并研究了不同厚度的有源层对器件性能的影响,发现TFT电学性能的变化规律几乎不受电极材料的影响,另外IGZO电极与ITO电极相比并没有比较突出的优势。更多还原

【Abstract】 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.更多还原