Burn-in stress induced BTI degradation and post-burn-in high temperature anneal (Bake) effects in advanced HKMG and oxynitride based CMOS ring oscillators

The impact of Bias Temperature Instability stress and poststress high temperature anneal (bake) effects on the performance of Ring Oscillator (RO) circuits is investigated for advanced node High-k Metal Gate (HKMG) and Oxynitride (SiON) based Silicon-On-Insulator (SOI) CMOS technologies. Examination of the circuit response (in terms of % frequency degradation) to a wide range of stress bias/temperature conditions reveals a distinct difference between the two technologies with respect to the voltage acceleration of frequency degradation. This difference is explained in view of the PBTI/NBTI voltage acceleration behaviour and indicates that PBTI dominates HKMG RO performance degradation. Post burn-in bake is found to be equally effective in recovering the burn-in induced frequency degradation in both HKMG and Oxynitride ROs. Finally, a simple model is proposed to predict net RO performance degradation from a combined burn-in/post-burn-in bake as a useful guideline for optimizing product burn-in testing.