Duty-cycle shift under asymmetric BTI aging: A simple characterization method and its application to SRAM timing

The effect of DC BTI stress on the clock signal's duty-cycle has been experimentally verified for the first time based on the precise frequency shift measurement from Ring OSCillators (ROSC). A simple and practical methodology based on the “silicon odometer” beat-frequency detection framework has been proposed for accurately measuring duty-cycle shifts while preventing unwanted BTI recovery. The measurement results from a 65nm test chip were used to further analyze the impact of asymmetric BTI aging during clock gated mode on SRAM timing signals.