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 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 45nm technology node. Thermal impact on more advanced 11nm technology node is also evaluated in the paper. Additionally, we propose a thermal-aware design for STT-RAM sensing circuit using bodybiasing 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 2.47X when reading '0' and 3.15X when reading '1', and reduce read disturbance error rate by 55.6% on average.

Addressing the Thermal Issues of STT-MRAM From Compact Modeling to Design Techniques

“…This paper focuses on the thermal behaviors of the MTJ device. There are many works on studying the switching behaviors of MTJ device under the temperature variations, but an electrical model capturing the thermal properties of the MTJ device is still missing for circuit design and evaluation [17,18]. In this paper, we first present a compact MTJ model that includes the thermal properties.…”

A Survey of Test and Reliability Solutions for Magnetic Random Access Memories

“…Especially, the characteristics of FM materials, such as TMR, are very sensitive to environmental temperature, which has already been observed in many experiments, such as in [87]. Wu et al [88] proposed a thermal model of MTJ validated by published experimental measurements and found a significant read disturbance in the deep submicrometer regime. A bodybiased feedback sensing amplifier was also proposed to improve read reliability at high temperatures.…”

Neural Network-Based Dynamic Threshold Detection for Non-Volatile Memories

“…Moreover, the resistance distributions of the STT-MRAM cell are also affected by the working temperature. It has been found that with the increase of temperature, the high resistance R 1 will decrease and while the low resistance R 0 hardly changes [5]. Fig.…”

“…In the recently commercialized STT-MRAM, the change of the working temperature also has a significant impact on the memory reliability. In particular, with the increase of temperature, the low resistance of the STT-MRAM cell hardly changes, but the high resistance decreases, thus leading to more overlapping of the memory resistance distributions [5]. The corresponding deviations from the nominal values of memory readback signals (e.g.…”