铟锡锌氧化物薄膜晶体管的制备与特性研究

发布时间：2018-01-23 22:07

  本文关键词： 铟锡锌氧化物 薄膜晶体管 射频磁控溅射 工艺参数 有源层厚度　出处：《山东大学》2016年硕士论文　论文类型：学位论文

【摘要】：薄膜晶体管作为像素开关被广泛应用于液晶显示器、有机发光二极管及电子纸等平板显示和柔性显示中。由于显示器在视角、响应速度、屏幕尺寸、对比度及功耗等方面的要求逐渐提高,对薄膜晶体管的要求也更高了。近7年来,ITZOTFT凭借迁移率高、亚阈值摆幅小等优点成为研究的热点,并被期待在显示领域成为核心元件,但目前国内对ITZO TFT的研究报道较少,制备工艺及工艺参数还在探索中。射频磁控溅射技术制备的薄膜均匀、重复性好,还没有发现用该技术系统研究ITZO TFT'性能的相关报道。本文采用此技术在室温下硅衬底上制备以ITZO为有源层的TFT,研究了工艺参数及有源层厚度对器件电学性能和稳定性的影响,其中,ITZO靶的靶材比例为IN2O3:SnO2:ZnO=88:10:2 wt%。(1)研究了溅射功率对ITZO TFT电学性能的影响,功率变化范围为50-80W。实验结果表明：功率太低时,不利于ITZO TFT电流开关比的提高；而功率太高则会造成TFT的关电流太大,器件失效。当溅射功率为60 W时,ITZO TFT的关电流值最小为10-10A、电流开关比为105。(2)在压强分别为0.4、0.6、0.8、1.0 Pa时制备了ITZO TFT,研究溅射气压对器件性能的影响。随着气压的增大,ITZO TFT的迁移率逐渐降低、负向阈值电压先减小后增大,这是由载流子浓度和界面缺陷密度两方面因素共同决定的。0.6 Pa是制备ITZO TFT较为理想的沉积气压。(3)采用氧分压分别为12%、17%、19%制备了ITZO TFT。随着氧分压的增大,TFT的阈值电压由负值变为正值、迁移率先增大后减小。当氧分压为17%时,器件的综合电学特性最好：迁移率大小为6.28 cm2／Vs、电流开关比高于105、亚阈值摆幅仅为0.60 V/decade.(4)研究了ITZO TFT的电学性能在不同厚度有源层影响下的变化规律。采用最优的工艺参数：溅射功率60 W、溅射气压0.6 Pa、氧分压17%,ITZO厚度分别为16、25、36、45、55 nm。随着厚度的增加,TFT的迁移率先上升后下降,而阈值电压呈现出相反的变化趋势；除有源层厚度为16 nm的TFT外,其它厚度对应TFT的电流开关比均高于105、亚阈值摆幅都在0.8 V/decade以下。(5)对器件的稳定性做了初步研究,研究对象是不同有源层厚度的ITZOTFT,条件是在大气氛围中静置20天。通过测试电学特性发现：有源层为16 nm的器件输出特性最差；36 nm对应的器件阈值电压漂移达到12.51 V；而55 nm的ITZO TFT阈值电压漂移只有1.07 V,稳定性较好。将ITZO TFT在60℃空气氛围中加热360 s后发现：有源层厚度为45、55 nm的ITZO TFT的迁移率提高了3倍多,几乎达到初始水平；阈值电压略有增大；亚阈值摆幅变化不大,均在0.8 V/decade以下。由此得出：增加有源层厚度可以削弱空气和水分对TFT造成的侵蚀、提高器件在空气中的稳定性；加热可以有效地抑制空气对器件造成的不良影响同时提升TFT在阈值电压方面的性能。
[Abstract]:Thin film transistors are widely used as pixel switches in liquid crystal displays, organic light-emitting diodes, electronic paper and other flat panel display and flexible display, because of the display in the angle of view, response speed, screen size. The requirement of contrast and power consumption is increasing gradually, and the requirement of thin film transistor is also higher. In the last seven years, ITZOTFT has become a hot topic because of its high mobility and small sub-threshold swing. It is expected to become the core component in the field of display, but there are few reports on the research of ITZO TFT in China at present, and the preparation process and technological parameters are still under exploration. The thin films prepared by RF magnetron sputtering are uniform. Good reproducibility has not been found in the study of the performance of ITZO TFT'by using this technique. In this paper, TFT with ITZO as active layer was prepared on silicon substrate at room temperature. The effects of process parameters and active layer thickness on the electrical properties and stability of the devices are studied. The effect of sputtering power on the electrical properties of ITZO TFT was studied. The experimental results show that when the power is too low, the current switching ratio of ITZO TFT is unfavorable. If the power is too high, the switching current of TFT will be too large and the device will fail. When the sputtering power is 60W, the minimum off current value of ITZO TFT is 10-10A. ITZO TFT was prepared when the current switching ratio was 105. 2) and the voltage was 0. 4 ~ 0. 6 ~ 0. 8 ~ 0. 0 Pa, respectively. The effect of sputtering pressure on the device performance is studied. With the increase of pressure, the mobility of ITZO TFT decreases gradually, and the negative threshold voltage decreases first and then increases. It is determined by carrier concentration and interface defect density that 0.6Pa is the ideal deposition pressure for preparing ITZO TFT.) the oxygen partial pressure is 12%, respectively. With the increase of oxygen partial pressure, the threshold voltage of ITZO is changed from negative to positive, and the migration increases first and then decreases. When the oxygen partial pressure is 17, the threshold voltage of TFT is increased. The overall electrical properties of the device are the best: the mobility is 6.28 cm ~ 2 / V _ s and the current-switching ratio is higher than 105. The sub-threshold swing is only 0.60 V / decade. 4). The variation of electrical properties of ITZO TFT under the influence of different thickness active layers was studied. The optimal process parameter: sputtering power 60W was adopted. The thickness of ITZO in the sputtering pressure is 0.6 Pa, and the thickness of ITZO is 162525, 36, 4555 nm, respectively. With the increase of the thickness, the TFT increases first and then decreases. The threshold voltage showed the opposite trend. With the exception of TFT with active layer thickness of 16 nm, the current switching ratio of other thickness corresponding to TFT is higher than 105. The subthreshold swing is below 0.8 V / decade. The stability of the device is studied preliminarily. The object of study is ITZOTFT with different active layer thickness. The experimental results show that the output characteristics of the device with active layer of 16 nm are the worst. The threshold voltage drift of the device corresponding to 36 nm is 12.51 V. The threshold voltage shift of 55 nm ITZO TFT is only 1.07 V. When ITZO TFT was heated in air at60 鈩，

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