Al2O3钝化层对a-IGZO薄膜晶体管电性能的增强机制研究

The enhancement mechanism of Al2O3 passivation layer on the electrical properties of a-IGZO thin film transistors

摘要:

非晶铟镓锌氧薄膜晶体管（a-IGZO TFT）具有高场效应迁移率、高开关比等优点，在主动驱动显示技术、柔性和可穿戴电子器件领域具有巨大的应用潜力。但其电学性能稳定性差是制约大规模应用的关键问题。本文采用空心阴极增强脉冲激光沉积技术（HC-PLD）在室温制备高质量的Al2O3薄膜，作为a-IGZO TFT器件的钝化层，显著增强了Al2O3/a-IGZO TFT器件的亚阈值特性，其原因在于空心阴极引入的氧等离子体抑制了Al2O3/a-IGZO界面处氧空位的形成。进一步研究发现，针对a-IGZO薄膜的180 oC退火处理有利于消除弱结合氧并抑制深能级缺陷，提高载流子迁移率并降低阈值电压漂移；而针对Al2O3/a-IGZO TFT器件进行100 oC退火处理有助于消除其界面附近的氧空位，降低载流子浓度，改善亚阈值特性。结合两步退火工艺所制备的Al2O3/a-IGZO TFT器件迁移率高达22.8 cm2V-1s-1，亚阈值摆幅为0.6 Vdecade-1，综合电性能优异。

Abstract:

Amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFTs) have the advantages of high field effect mobility and high switching ratio, and thus exhibit great potential applications in the fields of active drive display technology, flexible and wearable electronic devices. However, the poor stability of the electronic performances is the key problem restricting its large-scale applications. In this paper, Al2O3 thin films with low oxygen vacancy content were prepared by hollow cathode assistant pulsed laser deposition at room temperature, and used as the passivation layer of a-IGZO TFT devices. In-depth X-ray photoelectron spectroscopy illustrates that oxygen plasma introduced by the hollow cathode inhibits the formation of oxygen vacancies at the Al2O3/a-IGZO interface, which could improve the subthreshold performances of the TFT devices. 180 oC annealing for a-IGZO films could improve the mobility and reduce the threshold voltage shift; Annealing at 100 oC for Al2O3/a-IGZO TFT devices is helpful to reduce the carrier concentration and improve the subthreshold characteristics. The mobility of TFT devices processed by these two combining annealing processes could be as high as 22.8 cm2V-1s-1, and the subthreshold swing is 0.6 Vdecade-1.