Pitch Scaling Prospect of Ultra-Small Magnetic Tunnel Junctions for High-Density STT-MRAM: Effects of Magnetostatic Interference From Neighboring Bits

Magnetic tunnel junction (MTJ) miniaturization has been demonstrated down to 2 nm with performance applicable to a wide variety of applications. In highly dense STT-MRAM, where such ultra-small MTJs are packed with tight pitches, magnetostatic interference from neighboring bits becomes a concern. In this study, we investigate the impact of magnetostatic interference on the ultra-small MTJs with various stack structures when integrated into highly dense arrays and discuss the scaling prospect. We first calculate the stray fields exerted on an MTJ from neighboring bits and then evaluate the tolerance of the MTJ against the field by measuring the external field dependence of the switching voltage of isolated MTJs. We find that STT-MRAM using the ultra-small MTJs has the potential to achieve a large capacity above 100 Gbit/cm2 with a reasonably small variation in switching voltage. This work provides pitch scaling prospects toward high-density STT-MRAM with ultra-small MTJs.