Self-Limiting Behavior of Hot Carrier Degradation and Its Implication on the Validity of Lifetime Extraction by Accelerated Stress

The time dependence of hot carrier degradation of n-channel MOSFETs and the methodology of accelerated stress have been investigated in detail. The time (T) dependence is found to be inconsistent with the simple expression of TN (N-0.25), but rather show a slow-down of the degradation rate. The slope of the degradation curve is also found to be dependent on the stress bias voltage. The projection of device lifetime by accelerated stress based on the TN law and the assumption of constant slope independent of stress bias is unreliable.