Design and Analysis of Radiation Hardened Sensing Circuits for Spin Transfer Torque Magnetic Memory and Logic

Abstract

CMOS downscaling makes advanced memory and computing systems more vulnerable to radiation. Emerging non-volatile memories such as Magnetic RAM (MRAM) are under development to replace SRAM and FLASH memories. Spin Transfer Torque Magnetic Memory (STT-MRAM) is considered as one of the most promising memories for high reliability appli- cations. This is due to its intrinsic hardness to radiation, as storage is based on the spin direction of electrons instead of the charge. Its peripheral CMOS circuits are sensitive to radiation; however we can recharge frequently the non-volatile storage to get correct data. Different from conventional MRAM based on magnetic field switching, STT-MRAM is unable to be used directly for hard radi- ation applications as the current pulses induced by radiation may change the storage due to the stochastic behaviors of spin transfer torque mechanism. In this paper, we analyze firstly this issue and propose a rad-hard design for STT-MRAM sensing circuit with low area overhead and negligible performance degradation. Both transient and Monte-Carlo simulation have been performed to demonstrate its performance and behaviors.