Demonstration of Spin Orbit Torque Multi-Level Cell With Enhanced State Distinction

Abstract

Spin-orbit torque (SOT)-based multi-level cell (MLC) shows the advantage of area saving by sharing the write path and reducing the number of transistors. However, to our knowledge, it is challenging to accurately write different states into SOT-MLC due to intrinsic bottlenecks such as inter-cell interference and ballooning-like effect. In this work, we firstly propose and experimentally realize structural optimization of SOT-MLC using the shared top electrode and varying-width heavy metal layer. Furthermore, we improve the writing method by utilizing the double-pulse scheme to experimentally reshape multiple switching probability curves. Meanwhile, the mutual interaction between the adjacent cells is modeled and analyzed. Our work enables the SOT-MLC to be applied in both accurate storage and fault-tolerant computing scenarios.