Design of Almost-Nonvolatile Embedded DRAM Using Nanoelectromechanical Relay Devices
Hongtao Zhong, Mingyang Gu, Juejian Wu, Huazhong Yang and Xueqing Lia
Electronic Engineering Department, Tsinghua University Beijing, China
axueqingli@mail.tinghua.edu.cn
ABSTRACT
This paper proposes low-power design of embedded dynamic random-access memory (eDRAM) using emerging nanoelectromechanical (NEM) relay devices. The motivation of this work is to reduce the standby refresh power consumption through the improvement of retention time of eDRAM cells. In this paper, it is revealed that the tunable beyond-CMOS characteristics of emerging NEM relay devices, especially the ultra-high OFF-state drain-source resistance, open up new opportunities with device-circuit co-design. In addition, the pullin and pull-out threshold voltages are tilled to fit the operating mechanisms of eDRAM, so as to support low-voltage operations along with long retention time. Excitingly, when low-gate-leakage thick-gate transistors are used together, the proposed NEM-relaybased eDRAM exhibits so significant retention time improvement that it behaves almost “nonvolatile”. Even if using thin-gate transistors in a 130nm CMOS, the evaluation of the proposed eDRAM shows up to 63× and 127× retention time improvement at 1.0V and 1.4V supply, respectively. Detailed performance benchmarking analysis, along with the practical CMOScompatible NEM relay model, the eDRAM design and optimization considerations, is included in this paper.
Keywords: Embedded DRAM (eDRAM), DRAM, NEM Relay, retention time, low power, beyond-CMOS.
