Temperature Impact Analysis and Access Reliability Enhancement for 1T1MTJ STT-RAM

Abstract

Spin-transfer torque magnetic random access memory (STT-RAM) is a promising and emerging technology due to its many advantageous features such as scalability, nonvolatility, density, endurance, and fast access speed. However, the operation of STT-RAM is severely affected by environmental factors such as process variations and temperature. As the temperature rockets up in modern computing systems, it is highly desirable to understand thermal impact on STT-RAM operations and reliability. In this paper, a thermal-aware MTJ model, calibrated and validated by experimental measurements, is proposed as the basis for thoroughly thermal aware analysis of a 1T1MTJ STT-RAM cell structure. Using this model, we investigate temperature effect on memory cell access behavior in terms of access latency, energy, and reliability on a 45-nm technology node. Thermal impact on a more advanced 11-nm technology node is also evaluated in the paper. Additionally, we propose a thermal-aware design for STT-RAM sensing circuit using a body-biasing technique, which can enlarge read margin dramatically to enhance read reliability under temperature variations. Moreover, our proposed technique can suppress read disturbance effectively as well. Experimental results show that our proposed sensing circuit can enlarge read margin by 2.47 $\times$ when reading “0” and 3.15 $\times$ when reading “1,” and reduce read disturbance error rate by 55.6% on average.