非晶铟镓锌氧薄膜晶体管反相器稳定性提升的电路设计

Improving circuit design for the stability of inverters based on amorphous indium gallium zinc oxide thin film transistors

薄膜晶体管(TFT)反相器的稳定性问题是影响其在玻璃上系统(SOG)显示技术等领域中实际应用的重要挑战。本文基于实验数据提取了非晶铟镓锌氧TFT器件仿真模型,拟合并得到了其阈值电压变化幅度(ΔVTH)与电压偏置时间的拉伸指数方程。在此基础上,探究了传统伪CMOS反相器的电学稳定性随偏置时间的变化规律,并提出了一种改进的TFT反相器电路,对其进行管宽调节并设计了物理版图。改进型反相器通过延迟输出级下拉管的开启使输出高电平值接近电源电压,增加了18.47%。通过反馈缓解其阈值电压漂移所导致的等效电阻增大对输出级电流的影响,显著提高了其速度稳定性。在电压偏置时间为2.56×10^(7)s时,其上升时间的变化率只有4.09%,远低于传统伪CMOS反相器的296.11%。

The stability of thin film transistor inverters affects their further applications in the fields such as system on glass(SOG),etc.In this study,a simulation model of amorphous IGZO TFT devices was extracted based on the experimental data.In addition,the stretched-exponential equation between the threshold voltage change(ΔVTH)and the bias stress time was obtained by fitting.Then,the variation of the electrical stability of traditional pseudo-CMOS inverters with bias stress time was explored,and an improved TFT inverter circuit was proposed,followed by the channel width adjustment and layout design.The revised inverter improves the high output voltage by 18.47%by delaying the pull-down transistor in the output stage.Meanwhile,the proposed inverter alleviates the effect of equivalent resistance increase caused by the threshold voltage shift on the output stage current through feedback,significantly improving its speed stability.When the bias stress time is 2.56×10^(7)s,the variation rate in its rise time is only 4.09%,far lower than the 296.11%of the traditional pseudo-CMOS inverters.