柔性非晶SnSiO薄膜晶体管不稳定性研究

Amorphous oxide thin film transistor (TFT) is one of the flexible display candidate materials due to its advantages of high mobility, high transparency, high uniformity, and low process temperature. Among the three oxide materials (ZnO, In2O3, SnO2), In has an extremely low abundance, and ZnO is not suitable for wet etching. Therefore, tin oxide-based TFTs have attracted much attention. However, the stability and stress stability of tin oxide-based TFTs are poor, and the mechanism of instability is not clear, which limit its practical application in the field of flexible display. This project intends to take Si-doped tin oxide TFT (a-SnSiO TFT) as the research object (doping Si effectively suppresses carrier concentration due to the high Si-O binding energy) which adopts the method of changing the annealing conditions, plasma treatment and mechanical stress, regulating the atomic arrangement, changing the defect distribution of the channel layer to obtain the stability variation law of a-SnSiO TFT. We further analyze the mechanism of bias and mechanical stress instability and explore ways to overcome instability through a combination of structural characterization, performance testing and computational simulation. The research results of this project will provide experimental basis and theoretical reference for the stability control of amorphous tin oxide-based TFTs and the development of national flexible display core technologies.

非晶氧化物薄膜晶体管(TFT)由于具有高迁移率、高透明性、高均匀性和低工艺温度的优点而成为了柔性显示候选材料之一。三大氧化物基体材料(ZnO, In2O3, SnO2)中，In丰度极低，ZnO不适用湿法刻蚀，因此，氧化锡基TFT备受关注。但氧化锡基TFT偏压稳定性与应力稳定性较差，不稳定性机制尚不清晰，从而制约了其在柔性显示领域的实际应用。本项目拟以硅掺杂氧化锡TFT（a-SnSiO TFT）为研究对象（Si-O结合能高，能有效抑制载流子浓度），通过改变退火条件、等离子处理及施加机械应力的方式，调控沟道层的原子种类与排列，进而改变缺陷态分布，获得a-SnSiO TFT的稳定性变化规律；通过结合结构表征、性能测试和计算模拟，深入分析偏压和机械应力不稳定性的发生机制，探索克服不稳定性的方法。本项目的研究结果将为非晶氧化锡基TFT的稳定性调控以及国家柔性显示核心技术的发展提供实验依据和理论参考。

本项目分别通过磁控溅射法、溶胶凝胶法制备了非晶氧化锡基薄膜晶体管(TFT)，并探究了退火气氛、退火温度、元素掺杂、等离子体处理等对氧化锡基TFT电学特性以及稳定性影响。实验发现，在350 ℃退火温度下，氧化锡基薄膜依然保持非晶态，并显示出极为优异的光学透射率。退火期间，氧气的存在（空气和氧气中退火）能够产生更多与氧有关的缺陷态，降低TFT的迁移率以及偏压稳定性。氮气中退火后的TFT显示出更高的迁移率和更佳的偏压稳定性。退火温度的升高造成更多的氧空位由深能级缺陷转变为浅能级缺陷，释放出更多的电子，导致载流子浓度和迁移率增加。并且，在氧化锡基沟道层中适当元素的掺杂(如Ga、Eu)有利于降低氧化锡基TFT沟道层中的载流子浓度，减小关态电流，改善亚阈值摆幅，并提高开关比。在正/负栅压条件下，氧化锡基TFT显示出正向/负向阈值电压漂移现象，且栅压越大，漂移现象越严重，这主要归因于沟道层内以及沟道层/界面态缺陷态对载流子更快速的捕获以及空气中水分、氧气的吸附作用造成。适当的氩等离子体处理能够增加氧化锡基沟道层内载流子浓度，阈值电压负向移动，提高开关比，亚阈值摆幅也有所改善，相反，氧等离子体处理后，氧化锡基TFT载流子浓度降低，阈值电压正向漂移。当两种等离子体处理时间过长时，由于大量深能级缺陷的产生，造成输出曲线中“驼峰”现象的产生。本项目将为氧化锡基TFT在显示产业中的应用，以及显示基础理论的发展提供一定的研究基础和技术支持。