An 8T SRAM With On-Chip Dynamic Reliability Management and Two-Phase Write Operation in 28-nm FDSOI

Bias temperature instability (BTI) degradation poses increasingly critical lifetime reliability design challenges in static random access memory (SRAM), as fabrication technology marches toward a very deep nanometer regime. This paper presents circuit techniques that enable on-chip dynamic reliability management, which intelligently monitors and mitigates the half-selected cell stability failure due to BTI degradation in SRAM. The dynamic reliability management is achieved through the automated BTI-aware write word-line (WWL) control, whereby it detects the BTI degradation in SRAM cells through a replica row-based BTI-aware stability monitor and adjusts the WWL voltage level with two-phase write operation (TPWO). The WWL voltage level is divided into two phases to maintain the half-selected cell stability with BTI without compromising other circuit parameters. Silicon validation of a 16-kb SRAM based on a 28-nm fully depleted silicon on insulator (FDSOI) technology successfully demonstrates that the half-selected cell stability failure is eliminated from 57.13% down to 0% with the proposed approach at a marginal 3.42% power and 10% area overheads.