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

Abstract

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 V T instability is frequency independent, an observation that suggests that V T 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.