STT-RAM Cell Optimization Considering MTJ and CMOS Variations

Spin-transfer torque random access memory (STT-RAM) becomes a promising technology for future computing systems for its fast access time, high density, nonvolatility, and small write current. However, like all the other nanotechnologies, STT-RAM suffers from process variations and environment fluctuations, which significantly affect the performance and stability of magnetic tunneling junction (MTJ) devices. In this study, we combine magnetic and circuit simulations to quantitatively analyze the impacts of MTJ and CMOS variations on the STT-RAM designs. Both bit-to-bit and cycle-by-cycle variations are considered. A robust STT-RAM design flow is also proposed.

[1]  Wenzhong Zhu,et al.  Possible Spin Pumping Effects on Spin Torque Induced Magnetization Switching in Magnetic Tunneling Junctions , 2009, IEEE Transactions on Magnetics.

[2]  Shoji Ikeda,et al.  2Mb Spin-Transfer Torque RAM (SPRAM) with Bit-by-Bit Bidirectional Current Write and Parallelizing-Direction Current Read , 2007, 2007 IEEE International Solid-State Circuits Conference. Digest of Technical Papers.

[3]  Berger.  Emission of spin waves by a magnetic multilayer traversed by a current. , 1996, Physical review. B, Condensed matter.

[4]  Yiran Chen,et al.  Spin Torque Random Access Memory Down to 22 nm Technology , 2008, IEEE Transactions on Magnetics.

[5]  M. Hosomi,et al.  A novel nonvolatile memory with spin torque transfer magnetization switching: spin-ram , 2005, IEEE InternationalElectron Devices Meeting, 2005. IEDM Technical Digest..

[6]  T. Gilbert.  A Lagrangian Formulation of the Gyromagnetic Equation of the Magnetization Field , 1955 .

[7]  Arijit Raychowdhury,et al.  Design space and scalability exploration of 1T-1STT MTJ memory arrays in the presence of variability and disturbances , 2009, 2009 IEEE International Electron Devices Meeting (IEDM).

[8]  Yu Cao,et al.  Statistical modeling and simulation of threshold variation under dopant fluctuations and line-edge roughness , 2008, 2008 45th ACM/IEEE Design Automation Conference.

[9]  Kaushik Roy,et al.  Modeling of failure probability and statistical design of Spin-Torque Transfer Magnetic Random Access Memory (STT MRAM) array for yield enhancement , 2008, 2008 45th ACM/IEEE Design Automation Conference.

[10]  D. Dimitrov,et al.  Spin Torque Induced Magnetization Switching Variations , 2009, IEEE Transactions on Magnetics.