Manufacturable 300mm platform solution for Field-Free Switching SOT-MRAM

Abstract

We propose a field-free switching SOT-MRAM concept that is integration friendly and allows for separate optimization of the field component and SOT/MTJ stack properties. We demonstrate it on a 300 mm wafer, using CMOScompatible processes, and we show that device performances are similar to our standard SOT-MTJ cells: reliable sub-ns switching with low writing power across the 300mm wafer. Our concept/design opens a new area for MRAM (SOT, STT and VCMA) technology development. Introduction: Among non-volatile memory technologies, Spin-Transfer-Torque (STT) MRAM is seen as a credible candidate to replace SRAM in low level caches due to its scalability, low power and high speed, as well as compatibility with scaled CMOS processes and voltages. This is reflected by major foundries and tool suppliers investing significant R&D resources into embedded MRAM past years. Recently they even started prototyping demonstrators, progressively reaching maturity for mass production [1-5]. However, STT-MRAM

Numerical Analysis of Deterministic Switching of a Perpendicularly Magnetized Spin-Orbit Torque Memory Cell

“…4. The x-component of this field averages to about 35 mT, which is similar to that reported in [2] and [7]. In this case, the magnetization of the remaining free part of the FL will precess and be oriented perpendicularly in the wanted direction, dragging along the rest of the FL magnetization, when I 2 is turned off.…”

Energy‐Efficient Ultrafast SOT‐MRAMs Based on Low‐Resistivity Spin Hall Metal Au0.25Pt0.75

“…The relatively low channel resistance due to the low ρ xx of Au 0.25 Pt 0.75 is beneficial for decreasing write energies, achieving unlimited endurance, and also for matching the impedance of superconducting circuits in cryogenic computation systems. This is in contrast to the perpendicular SOT‐MTJs where a highly resistive Ta or W channel is typically required to achieve perpendicular magnetic anisotropy of the free layer . We find that the current‐induced SOT switches the Au 0.25 Pt 0.75 ‐based MRAMs much faster than expected from a rigid macrospin model, most likely due to the rapid micromagnetics within the free layer that is enhanced by the spatial nonuniformities in the free‐layer magnetization that may be induced by DMI, interfacial magnetic roughness, and/or tapering in the MTJ free layer.…”

“…The nonvolatile MRAM also has long data retention and zero standby power. The collinear in‐plane MRAMs can be switched directly by spin current from the spin Hall channel, while perpendicular SOT‐MTJs require a markedly high write current in the nanosecond and sub‐nanosecond pulse regime as well as assistance of a strong in‐plane magnetic field (e.g., stray field from an adjacent ferromagnetic layer or built‐in magnetic field from a lateral structural asymmetry) or an additional large write current in the MTJ nanopillar, which may lower the energy efficiency, the scalability, and the endurance of the MTJ cells. These results indicate that the Au 0.25 Pt 0.75 ‐based in‐plane SOT‐MRAM is a good candidate for ultrafast, energy‐efficient, low‐impedance, unlimited‐endurance memory for large scale computing systems, machine‐learning systems, and superconducting electronics.…”

Optimization of a Spin-Orbit Torque Switching Scheme Based on Micromagnetic Simulations and Reinforcement Learning

“…Switching is accomplished by applying a current through a heavy metal wire attached to the magnetic free layer (FL). Thus, it can operate with a sub-nanosecond timing retaining excellent endurance [ 15 , 16 , 17 ]. These properties make SOT-MRAM particularly interesting for nonvolatile replacement of the classical static random access memory (SRAM) used in caches.…”

“…It should be pointed out, however, that deterministic SOT switching of a perpendicularly magnetized FL requires an external magnetic field [ 18 ]. Several field-free schemes have been proposed to circumvent this issue, usually at the cost of a more complex cell stack fabrication [ 15 , 16 , 19 , 20 , 21 , 22 , 23 ].…”