NBTI Lifetime Prediction and Kinetics at Operation Bias Based on Ultrafast Pulse Measurement

Predicting negative bias temperature instability (NBTI) lifetime can be dangerous since it is difficult to assess its safety margin. The common technique uses gate bias V_g acceleration to reduce the test time, and the data were typically obtained from quasi-DC measurements. Recently, it has been shown that substantial recovery occurs during the quasi-DC measurement, and the suppression of recovery requires using ultrafast pulse measurement, where time was reduced to the order of microseconds. In a real circuit, different transistors have different levels of recovery, and the worst case scenario is when recovery is suppressed. At present, there is little information on how this worst case NBTI lifetime can be predicted and whether the traditional V_g acceleration technique can still be used. This work will show that the prediction based on the V_g acceleration results in a substantial error, and its cause will be analyzed. To predict the worst case lifetime, a model for NBTI kinetics under operation gate bias is developed. This kinetics includes contributions from both as-grown and generated defects, and it no longer follows a simple power law. Based on the new kinetics, a single-test prediction method is proposed, and its safety margin is estimated to be 50%.