GaN MIS-HEMT偏置温度不稳定性表征和寿命预测

Bias Temperature Instability Characterization and Lifetime Prediction of GaN MIS-HEMT

MIS-HEMT是最有前景的GaN HEMT器件结构之一,其通过引入高势垒的绝缘介质层,可以极大地抑制栅极泄漏电流,从而降低静态功耗。然而,额外的绝缘介质层在绝缘介质层和AlGaN界面处引入了大量的缺陷,使得MIS-HEMT的可靠性非常差,在偏置电压下的阈值电压的漂移极大,即偏置温度不稳定性(BTI)老化严重。与硅不同,GaN MIS-HEMT中绝大多数的缺陷都属于可恢复缺陷,随着栅极电压的变化可以反复地充放电,因此其BTI的恢复效应要远大于硅。采用单点I_(d)测量方法,将GaN MIS-HEMT阈值电压(V_(th))的测量从传统直流(DC)法的秒级缩短到了1 ms,构建了考虑恢复效应的GaN MIS-HEMT的BTI老化物理模型,预测了器件的寿命。试验结果表明,传统DC法严重地低估了BTI退化,在ΔV_(th)=1 V的失效判据下,传统DC法预测的器件寿命比考虑恢复效应的单点I_(d)法测得的寿命高了4个数量级。

MIS-HEMT is one of the most promising GaN HEMT device structures.By introducing a high barrier insulating dielectric layer,gate leakage current can be significantly suppressed,thereby reducing static power consumption.However,the additional insulating dielectric layer introduces a large number of defects at the interface between the insulating dielectric layer and AlGaN,which makes the reliability of MIS-HEMT very poor,and the threshold voltage drift under bias voltage is extremely large,that is,the aging of BTI,is serious.Unlike silicon,most defects in GaN MIS-HEMT are recoverable,which can be charged and discharged repeatedly depending on gate voltage,so the recovery effect of BTI is much greater than that of silicon.Using the spotI_(d)measurement method,the measurement time of the threshold voltage(V_(th))of the GaN MIS-HEMT is shortened from the second level of traditional DC method to 1 ms.The BTI aging physical model of GaN MIS-HEMT considering the recovery effect is constructed,and device lifetime is predicted.The test results show that the traditional DC method seriously underestimates the aging of BTI,under the failure criterion ofΔV_(th)=1 V,the device lifetime predicted by the traditional DC method is 4 orders of magnitude higher than that of spot-I_(d)method which considers the recovery effect.