Improvement of static noise margin in SRAM by post-fabrication self-convergence technique

Experimental Demonstration of Post-Fabrication Self-Improvement of SRAM Cell Stability by High-Voltage Stress

“…The gate voltage is the same as the source voltage, and the NBTI stress is not applied to p-OFF. As a result, the cell stability is improved [20]- [22].…”

“…Recently, we have proposed a new concept of a postfabrication technique to improve the stability of SRAM cells automatically by simply applying stress voltage to the V DD terminal of SRAM cell array [20], [21]. This technique can apply to the stability self-improvement in both the read operation [20], [21] and the retention operation [22]. When applied to the retention self-improvement, the stronger nFET and pFET out of four transistors in the two inverters are selectively stressed and their |V TH | is raised (and hence these transistors are weakened), while the weaker nFET and pFET are not stressed, resulting in automatic self-improvement of the cell stability.…”

Variability in scaled MOSFETs: Measurements, analysis, and suppression

“…In this study, a post-fabrication scheme for suppression of variability is proposed [14,[19][20]. The key in this concept is the "self-convergence" mechanism.…”

“…On the other hand, "p-low", which is weaker, is not stressed because "p-low" is at the OFF state. As a result, the cell stability is improved [14,[19][20]. 8.…”

Lowering data retention voltage in static random access memory array by post fabrication self-improvement of cell stability by multiple stress application

“…Previously, we proposed a post fabrication SRAM selfimprovement technique, which automatically improves the SRAM cell stability by simply applying a high stress voltage to the power supply terminal. [12][13][14][15] Bias temperature instability (BTI) stress selectively not only weakens the stronger one [12][13][14] but strengthens the weaker one 15,16) of pair transistors in each SRAM cell, resulting in the stability improvement of unstable cells in read 13,14) and retention 13,15) operations. However, one of the demerits of this technique is that stable cells will also be affected by the stress, and their stability can be worsened.…”