Highly-scalable disruptive reading and restoring scheme for Gb-scale SPRAM and beyond

We propose a disruptive reading and restoration scheme for a high density spin-transfer-torque random access memory (SPRAM). The proposed scheme uses the feature that - with a desired error rate and a tunnel magneto resistance (TMR) device, which is the memory device of the SPRAM - does not switch its magnetization of free layer in a specific period of large current pulse. The restoration operation is performed to secure the storing data. As a result, by keeping good scalability of spin-transfer-torque writing toward Gb-scale and beyond, high-speed reading with read-disturbance-free operation can be achieved. This operation also enables the SPRAM to accept the DDRx-SDRAM compatible operation. In addition, we also proposed a 4-F² cell structure with a vertical transistor and prospected the reliability of a tunnel barrier of the TMR devices for a Gb-scale SPRAM.