A robust reliability methodology for accurately predicting Bias Temperature Instability induced circuit performance degradation in HKMG CMOS

A robust reliability characterization / modeling approach for accurately predicting Bias Temperature Instability (BTI) induced circuit performance degradation in High-k Metal Gate (HKMG) CMOS is presented. A series of device level stress experiments employing both AC and DC stress/relax BTI measurements are undertaken to characterize FET's threshold voltage instability response to a dynamic (inverter type) operation. Results from the AC stress experiments demonstrate that VT instability is frequency independent, an observation that suggests that VT degradation under AC stress can be equivalently measured through the simpler DC stress/relax sequence. An AC BTI model is developed that accurately captures the critical BTI relaxation effect through the DC stress/relax predictions on duty cycle dependence. A Ring Oscillator (RO) circuit is used as a model verification vehicle. Excellent agreement is demonstrated between the frequency degradation measurements obtained with a newly developed Ultra-Fast On-The-Fly (OTF) measurement technique optimized for BTI and the AC BTI model based RO simulations.