2048
IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 62, NO. 6, JUNE 2015
Compact Model of Subvolume MTJ and Its Design Application at Nanoscale Technology Nodes Yue Zhang, Member, IEEE, Bonan Yan, Wang Kang, Student Member, IEEE, Yuanqing Cheng, Member, IEEE, Jacques-Olivier Klein, Member, IEEE, Youguang Zhang, Member, IEEE, Yiran Chen, Member, IEEE, and Weisheng Zhao, Senior Member, IEEE Abstract— The current-induced perpendicular magnetic anisotropy magnetic tunnel junctions (p-MTJs) offer a number of advantages, such as high density and high speed. As p-MTJs downscale to ∼40 nm, further performance enhancements can be realized thanks to high spin-torque efficiency, i.e., lower critical current density and higher thermal stability. In this paper, we investigate the origin of high spin-torque efficiency and give a phenomenological theory to describe the critical current reduction due to the subvolume activation. Based on various physical theories and structural parameters, a compact model of nanoscale MTJ is developed and demonstrates a satisfactory agreement with experimental results. Dynamic, static, and stochastic switching behaviors have been addressed and validated. Then, we perform mixed simulations for hybrid MTJ/CMOS read/write circuits, magnetic random access memory, and magnetic flip-flop to evaluate their performance. Analyses of energy consumption are given to show the prospect of MTJ technology node miniaturization. Index Terms— Compact model, hybrid integrated circuit, magnetic tunnel junction (MTJ), spin-torque efficiency.
I. I NTRODUCTION AGNETIC tunnel junctions (MTJs) are versatile spintronic devices cooperating with silicon-based semiconductor devices in memories, logic modules, and sensors [1]–[3]. Two appealing advantages drive the development of MTJ: 1) its compatibility with CMOS technology and 2) its scalability potential. These give rise to the intense investigations of MTJ at advanced technology nodes of modern microelectronic devices. The scalability of MTJ is guaranteed by two observations: 1) spin transfer torque (STT) provides an effective switching operation of nanoscale MTJs [4], [5] and 2) perpendicular magnetic
M
Manuscript received July 15, 2014; revised January 22, 2015; accepted March 14, 2015. Date of publication April 2, 2015; date of current version May 18, 2015. This was supported in part by the National Natural Science Foundation of China under Project 61071072 and Project 61471015 and in part by the Agence Nationale de la Recherche through Digital IP based on emerging non-volatile MEMories. The review of this paper was arranged by Editor R. Huang. (Corresponding author: Weisheng Zhao.) Y. Zhang, W. Kang, Y. Cheng, Y. Zhang, and W. Zhao are with the Beihang Spintronics Interdisciplinary Center, Beihang University, Beijing 100083, China (e-mail:
[email protected];
[email protected]; yuanqing@ buaa.edu.cn;
[email protected];
[email protected]). B. Yan was with the Beihang Spintronics Interdisciplinary Center, Beihang University, Beijing 100083, China. He is now with the University of Pittsburgh, Pittsburgh, PA 15261 USA (e-mail:
[email protected]). J.-O. Klein is with the Institut d’Electronique Fondamentale, University of Paris-Sud, Orsay 91400, France (e-mail:
[email protected]). Y. Chen is with the University of Pittsburgh, Pittsburgh, PA 15261 USA (e-mail:
[email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TED.2015.2414721
anisotropy (PMA) materials ensure the thermal stability of small MTJs (e.g.,
