Online Measurement of Degradation Due to Bias Temperature Instability in SRAMs

A method is proposed to detect failing cells due to bias temperature instability (BTI) in Static Random Access Memories (SRAMs) en route to failure. If potentially failing cells are detected prior to failure, SRAMs can be operated without failures, since the detection of potentially failing cells can trigger reconfiguration, given available memory redundancy. Using an experimentally verified BTI model, we study the performances of conventional 6T SRAM cells as a function of BTI degradation, in the presence of process variations. An on-chip monitoring scheme is presented that can be embedded within conventional SRAM designs without affecting normal device operation and with minimal overhead.