【作者】 袁毅；

【导师】 张磊；

【作者基本信息】 电子科技大学 ， 工程硕士（专业学位）， 2019， 硕士

【摘要】 氧化物薄膜晶体(TFT)具有迁移率高、可低温制备、可大面积制备、均匀性好、透明等一系列优点,所以在全透明显示以及柔性显示领域都有着巨大的发展潜力。本论文根据某些氧化物薄膜透明度高的这一特点制备了一系列基于a-IGZO材料为沟道层的全透明TFT。论文中成功的制备了全透明TFT,并且对全透明器件的绝缘层以及电极进行了研究以及优化。本论文的具体内容如下:(1)首先对全透明器件的绝缘层进行研究。论文中采用PMMA、PVA两种材料来作为全透明器件的绝缘层,并且分别制备了不同绝缘层转速下的TFT。研究发现,旋涂法制备的PMMA、PVA薄膜表面形貌良好,但PMMA薄膜的表面形貌要更为优异,并且提高旋转速度可以提高器件的整体性能。总体上,PVA薄膜的绝缘性能要优于PMMA薄膜,但是由于PVA薄膜表面形貌稍差,所以后续的研究选择了 PMMA作为器件的绝缘层。(2)确定了PMMA绝缘层的最佳转速之后,又对器件的电极进行了一系列的研究。首先研究了 ITO、IGZO这两种薄膜在不同制备工艺下光电性能有何改变。在0%氧分压、溅射功率为125 W、溅射时间为1500 s,腔体压强为1 mTorr下制备出的ITO薄膜电阻率最低,为1.54×10-4Ω·cm;在0%氧分压、溅射功率为125 W、溅射时间为1500 s、腔体压强为1 mTorr下制备的IGZO薄膜电阻率最低。(3)确定了透明电极的最佳制备工艺之后,制备了基于IGZO以及ITO作为透明电极的全透明TFT,两种器件都展示出了一定的性能,其中基于ITO电极的全透明TFT的性能更为优异。基于ITO电极的TFT开关比为1.7×104,迁移率为6.335 cm2V-1s-1,阈值电压为0.8 V,亚阈值摆幅为1.9 V/decade。基于IGZO电极的TFT开关比为0 696×103,迁移率为4.101cm2V-1s-1,阈值电压为3.1V,亚阈值摆幅为6.4 V/decade。(4)为了提高基于IGZO透明电极的器件的整体性能,还对器件进行了退火处理,研究发现退火可以改善绝缘层与有源层之间的界面缺陷,提高载流子迁移率,退火后,器件的迁移率提高到了 6.065 cm2V-1s-1,阈值电压从3.1V下降到了 1.6V。为了进一步提高器件的性能,制备了基于复合绝缘层的全透明TFT。在原有的PMMA绝缘层之前增加了一层超薄的原子层沉积(ALD)的氧化铝,复合绝缘层器件的迁移率为5.99 cm2V-1s-1,开关比为0.87×104,阈值电压以及亚阈值摆幅分别为2.6 V和3.5 V/decade。更多还原

【Abstract】 Oxygen thin film transistors(TFT)have a series of advantages,such as high mobility,low temperature preparation,large area preparation,good uniformity,transparency and so on.Therefore,they have great potential in the field of fully transparent display and flexible display.In this work,a series of fully transparent thin film transistors based on a-IGZO material are fabricated according to the high transparency of some oxide films.In this work,the fully transparent TFT is successfully prepared,and the insulating layer and electrode of the transparent device are studied and optimized.The specific contents of this work are as follows:(1)First,the insulating layer of fully transparent devices is studied.In this work,PMMA and PVA are used as insulating layers of transparent devices,and TFT at different rotational speeds of insulating layers are prepared respectively.The results show that the surface morphology of PMMA and PVA films prepared by spin coating is good,but the surface morphology of PMMA films is better,and the overall performance of devices can be improved by increasing the rotation speed.In general,the insulation performance of PVA film is better than that of PMMA film,but because the surface morphology of PVA film is slightly worse,PMMA is chosen as the insulation layer of devices in the follow-up study.(2)After determining the optimum speed of PMMA insulation layer,a series of studies have been carried out on the electrodes of the device.Firstly,the photoelectric properties of ITO and IGZO thin films were studied under different fabrication processes.The resistivity of ITO thin films prepared under 0%oxygen partial pressure,125 W sputtering power,1500 s sputtering time and 1 mTorr cavity pressure is the lowest,which is 1.54×10-4 Ω·cm.The resistivity of IGZO thin films prepared under 0%oxygen partial pressure,125 W sputtering power,1500 s sputtering time and 1 mTorr cavity pressure is the lowest.(3)After determining the optimum preparation process of transparent electrode,fully transparent TFT based on IGZO and ITO as transparent electrode was prepared.Both devices show certain performance,and the fully transparent TFT based on ITO electrode has better performance.The TFT switching ratio based on ITO electrode is 1.7×104,the mobility is 6.335 cm2V-1s-1,the threshold voltage is 0.8 V,and the sub-threshold swing is 1.9 V/decade.The TFT switching ratio based on IGZO electrode is 0.696×103,the mobility is 4.101 cm2V-1s-1,the threshold voltage is 3.1 V,and the sub-threshold swing is 6.4 V/decade.(4)In order to improve the overall performance of the device based on IGZO transparent electrode,annealing treatment was also carried out.It was found that annealing can improve the interface defects between the insulating layer and the active layer and improve the carrier mobility.After annealing,the mobility of the device increased to 6.065 cm2V-1s-1,and the threshold voltage decreased from 3.1 V to 1.6 V.In order to further improve the performance of the device,a transparent TFT based on composite insulating layer was prepared.Before the original PMMA insulating layer,a layer of ultra-thin atomic layer deposition(ALD)aluminium oxide was added.The mobility of the composite insulating layer device was 5.99 cm2V-1s-1,the switching ratio was 0.87×104,and the threshold voltage and sub-threshold swing amplitude were 2.6 V and 3.5 V/decade,respectively.更多还原