Countermeasures against NBTI degradation on 6T-SRAM cells

In current process technologies, NBTI (negative bias temperature instability) has the most severe aging effect on static random access memory (SRAM) cells. This degradation effect causes loss of stability. In this paper counter-measures against this hazard are presented and quantified via simulations in 90 nm process technologies by the established metrics SNMread, SNMhold, I-read and Write Level. With regard to simulation results and practicability best candidates are chosen and, dependent on individual preferences at memmy cell design, the best countermeasure in each case is recommended.