BTI and HCI degradation detection in SRAM cells

The influence of Bias-Temperature Instability (BTI) and Hot Carrier Injection (HCI) on Static Random Access Memory (SRAM) aging is of major importance. In this paper a circuit for the periodic monitoring of BTI and HCI degradation in SRAM cells is proposed. Periodic aging monitoring provides the ability to avoid failures in the memory array by locating and replacing over-degraded cells. The proposed scheme exploits a low cost differential ring oscillator that can be easily embedded in a typical SRAM without affecting its normal mode of operation.