基于体效应的SiC MOSFET器件栅极老化监测方法研究

长期以来,栅极老化一直是SiC MOSFET器件可靠性研究的关键,而偏置温度不稳定性则是栅极老化的重要现象。由于栅极老化的偏置温度不稳定性存在应力撤出后的恢复现象,如能在可靠性实验中快速、准确地监测SiC MOSFET器件的栅极老化变化量,对可靠性研究具有重要意义。因此,文中提出一种新的栅极老化监测方法。该方法以体效应下的阈值电压VTH(body)为基础,建立理论模型来描述VTH(body)和栅极老化之间的关系。提出在栅极电压开关过程中从体二极管电压–栅极电压曲线中得到VTH(body)的方法,并详细研究实验参数对VTH(body)的影响。此外,通过高温栅偏实验对VTH(body)的实用价值进行验证,并与栅极老化参数阈值电压VTH进行对比。实验结果证明,提出的新型栅极老化监测方法可以实现栅极老化的快速、准确及非恒温环境监测。

Study of Gate-oxide Degradation Monitoring Method Based on Body Effect in SiC MOSFETs

Gate-oxide degradation is considered as a critical reliability issue for SiC MOSFETs, for example the important bias-temperature instability phenomenon. The recovery phenomenon is obvious because of the abovementioned instability after the stress is withdrawn, the fast and accurate monitoring method in reliability test is therefore of great significance. In this paper, a new method for the gate oxide degradation monitoring using the threshold voltage induced by the body effect(written as VTH(body)) was proposed and experimentally verified. A theoretical model was firstly established to describe the relationship between VTH(body) and gate-oxide degradation. Then the method to obtain the VTH(body) from the curve of relationship between the body-diode voltage and the gate voltage in the switching process was proposed, and the influence of experimental parameters was studied in detail. Furthermore, the function of VTH(body) were experimentally verified by a high-temperature gate bias(HTGB) test and compared with that of the threshold voltage VTH. The result shows that this proposed method can fast and accurate realize gate oxide degradation monitoring under non-constant temperature environment.