Cross-Point Architecture for Spin-Transfer Torque Magnetic Random Access Memory

Spin-transfer torque magnetic random access memory (STT-MRAM) is considered as one of the most promising candidates to build up a true universal memory thanks to its fast write/read speed, infinite endurance, and nonvolatility. However, the conventional access architecture based on 1 transistor + 1 memory cell limits its storage density as the selection transistor should be large enough to ensure the write current higher than the critical current for the STT operation. This paper describes a design of cross-point architecture for STT-MRAM. The mean area per word corresponds to only two transistors, which are shared by a number of bits (e.g., 64). This leads to significant improvement of data density (e.g., 1.75 F²/bit). Special techniques are also presented to address the sneak currents and low-speed issues of conventional cross-point architecture, which are difficult to surmount and few efficient design solutions have been reported in the literature. By using an STT-MRAM SPICE model including precise experimental parameters and STMicroelectronics 65 nm technology, some chip characteristic results such as cell area, data access speed, and power have been calculated or simulated to demonstrate the expected performances of this new memory architecture.