STT-SOT Magnetoresistive Element With SCC Write-Current Crowding
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Solution Overview
Problem
Current magnetoresistive memory technologies face challenges in achieving high write efficiency and thermal stability while maintaining a high MR ratio and scalability, particularly in reducing the write current and improving switching speed in perpendicular spin-transfer-torque MRAMs, due to limitations in device miniaturization and material properties.
Innovation Solution
The development of STT-SOT hybrid perpendicular magnetoresistive elements with a sidewall-current-channel (SCC) structure, which includes a magnetic reference layer, tunnel barrier layer, SOT material layer, and a conductive sidewall channel, allowing for uniform spin-polarized current flow and combined spin-transfer and spin-orbit torques to efficiently switch the magnetization direction, reducing critical write current and write power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a planar-type MTJ with in-plane magnetization is used, then the magnetization direction can be switched by spin-polarized current, but high shape anisotropy or high magneto-crystalline anisotropy materials are required which prevent scalability and high density memory
Solution Approach 1:
The patent inverts the conventional in-plane magnetization configuration to perpendicular magnetization. By switching from in-plane to perpendicular magnetization direction, the device achieves thermal stability without requiring high aspect ratio structures, thereby enabling scalability and high density memory while maintaining reliable magnetization switching.
Solution Approach 2:
The patent changes the magnetic anisotropy parameter from in-plane to perpendicular orientation. This parameter change allows the use of perpendicular magnetic anisotropy materials that provide thermal stability without requiring the high shape anisotropy structures that would prevent miniaturization and scaling.
2Volume of moving object
If the volume of the magnetic layer is reduced for miniaturization, then lower write current is expected, but thermal stability may be compromised
Solution Approach 1:
The patent changes the magnetization orientation parameter to perpendicular, which fundamentally alters the energy barrier characteristics. This allows smaller magnetic layer volumes to maintain adequate thermal stability because perpendicular magnetic anisotropy provides stronger stabilization at reduced dimensions compared to in-plane configurations.
Solution Approach 2:
The patent employs composite perpendicular magnetization structures combining multiple magnetic layers with perpendicular magnetic anisotropy. These composite structures enhance thermal stability in miniaturized devices by distributing the magnetic moment across multiple layers with perpendicular orientation, maintaining energy barrier height even as overall volume decreases.
3Volume of moving object
If perpendicular magnetic anisotropy materials are used for miniaturization, then device size is reduced, but write efficiency and switching speed need improvement
Solution Approach 1:
The patent merges spin-transfer torque (STT) and spin-orbit torque (SOT) mechanisms into a hybrid switching approach. This combination leverages the advantages of both methods: STT provides direct magnetization switching through the tunnel barrier while SOT provides additional spin-orbit coupling assistance, resulting in enhanced switching speed and efficiency in perpendicular magnetization devices without increasing device size.
4Reliability
If high magneto-crystalline anisotropy materials are used for thermal stability, then thermal disturbance resistance is maintained, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the magnetization orientation to perpendicular, which fundamentally alters the anisotropy requirements. This parameter change enables the use of materials and structures that provide thermal stability through perpendicular magnetic anisotropy interfaces rather than requiring complex high magneto-crystalline anisotropy material compositions, thereby reducing manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances write efficiency and thermal stability, enabling faster switching speeds and lower write power consumption while maintaining high MR ratios, thus addressing the limitations of existing technologies in device miniaturization and scalability.
Implementation Method 1
a spin-orbit torque (SOT) material layer provided on a top surface of the MTJ stack and exhibiting the Spin Hall Effect
Implementation Method 2
magnetic random access memories (hereinafter referred to as MRAMs) using the magnetoresistive effect of ferromagnetic tunnel junctions
Implementation Method 3
the magnetization direction of a recording layer is reversed by applying a spin-polarized current along a specific direction to the magnetoresistive element
Data Source
AI summary
A magnetoresistive element comprises a nonmagnetic sidewall-current-channel (SCC) structure provided on a surface of the SOT material layer that exhibits the Spin Hall Effect, which is opposite to a surface of the SOT material layer where the magnetic recording layer is provided, and comprising an insulating medium in a central region of the SCC structure, and a conductive medium being a sidewall of the SCC structure and surrounding the insulating medium, making an electric current crowding inside the SOT material layer and the magnetic recording layer to achieve a spin-orbit torque and a higher spin-polarization degree for an applied electric current.