Evaluation of Effective Thermal Stability Factor for Patterned Magnetic Tunnel Junction Array

Abstract

Accurate and early estimation of the thermal stability factor of a memory array is essential for the development of modern non-volatile magnetic storage devices. We propose an evaluation method for effective array-level thermal stability factors ( $\Delta _{\mathrm {eff}}$ ) via magnetic characterization of patterned magnetic tunnel junction (MTJ) arrays. These patterned arrays do not require traditional electrical contacts and circuitry that are usually needed for $\Delta _{\mathrm {eff}}$ evaluation. Using vibrating sample magnetometer (VSM) at elevated temperatures and under applied fields, we demonstrate that these MTJ arrays exhibit a moment change trend that fits the Neel–Brown model and are able to extract the respective $\Delta _{\mathrm {eff}}$ . The domain-wall-mediated reversal model is used to obtain zero-field $\Delta _{\mathrm {eff}}$ . Using this method, we have optimized MTJ film stacks based on fast array-level feedback and validated high data retention of $\Delta _{\mathrm {eff}} \sim 46$ at 260 °C from fully integrated MTJ bit arrays.