Voltage-Controlled Magnetic Anisotropy MeRAM Bit-Cell over Event Transient Effects

Abstract

Magnetic tunnel junction (MTJ) with a voltage-controlled magnetic anisotropy (VCMA) effect has been introduced to achieve robust non-volatile writing control with an electric field or a switching voltage. However, continuous technology scaling down makes circuits more susceptible to temporary faults. The reliability of VCMA-MTJ-based magnetoelectric random access memory (MeRAM) can be impacted by environmental disturbances because a radiation strike on the access transistor could introduce write and read failures in 1T-1MTJ MeRAM bit-cells. In this work, Single-Event Transient (SET) effects on a VCMA-MTJ-based MeRAM in 28 nm FDSOI CMOS technology are investigated. Results show the minimum SET charge Q c required to reach the access transistor associated with the striking time that can lead to an unsuccessful switch, that is, an error in the writing process (write failure). The synchronism between the fluctuations of the magnetic field in the MTJ free layer and the moment of the write pulse is also analyzed in terms of SET robustness. Moreover, results show that the minimum Q c value can vary more than 100 % depending on the magnetic state of the MTJ and the width of the access transistor. In addition, the most critical time against the SET occurrence may be before or after the write pulse depending on the magnetic state of the MTJ.