Lifetime Enhancement under High Frequency NBTI measured on Ring Oscillators

In this paper, we studied the frequency degradation of ring oscillators (ROs) fabricated using 130nm technology. We demonstrate that for ROs operating at high temperatures in the frequency-range of 100MHz to 3GHz, Negative bias temperature instability (NBTI) is the dominant frequency degradation mechanism. The NBTI-lifetime measured on ROs is 4 decades longer than that of DC-stressed devices. A recovery of RO frequency is observed when stress is reduced, similar to stress relaxation in DC stress mode. Based on RO degradation data measured up to 3 GHz, we conclude that for circuits operating in a continuous switching mode, NBTI will not be a show stopper