MgO Sublayer Multi-Layers for MRAM Perpendicular Anisotropy

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Solution Overview

Problem

Conventional Magnetic Random Access Memory (MRAM) devices face challenges in scaling down device dimensions below 10 nm due to low thermal energy barriers between magnetizations, requiring improved magnetic free layers with high perpendicular magnetic anisotropy and efficient spin transfer torque switching.

Innovation Solution

The implementation of nFe|mMgO or nCo|mMgO multi-layers with specific sublayer configurations, including a magnetic reference layer, tunnel barrier, and magnetic free layer with MgO sublayers, enhances perpendicular magnetic anisotropy and spin-polarized current passage, utilizing Density Functional Theory calculations and controlled deposition techniques to achieve high anisotropy and spin-polarization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional CoFeB based PMA materials are used, then the device can operate with basic magnetic properties, but the thermal energy barrier between magnetizations is insufficient for scaling below 10 nm

Engineering Contradiction:

Improvethermal energy barrierVSAvoiddevice dimension

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The patent employs composite magnetic multi-layer structures comprising alternating layers of ferromagnetic materials (CoFeB, CoFe, CoFeNi) and non-magnetic spacer layers (MgO, Ta, Ru). This composite architecture generates perpendicular magnetic anisotropy through interface effects between dissimilar materials, achieving high thermal energy barriers that enable reliable operation at sub-10 nm dimensions where conventional single-material PMA structures fail

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention introduces localized interface regions with enhanced magnetic properties by creating specific Co-Fe-O bonding environments at the interfaces between magnetic layers and MgO spacers. These localized interface regions with perpendicular magnetic anisotropy are confined to specific positions within the multi-layer structure, providing high thermal stability without requiring the entire structure to be scaled proportionally

Inventive Principle:

Principle #3Local quality

2Productivity

If device dimensions are scaled down to increase density, then higher storage density is achieved, but spin transfer torque switching efficiency decreases

Engineering Contradiction:

Improvestorage densityVSAvoidspin transfer torque efficiency

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent optimizes the thickness parameters of individual layers within the multi-layer structure, specifically tuning the magnetic layer thickness to 3-10 nm and spacer layer thickness to 1-3 nm. These parameter adjustments enhance spin transfer torque efficiency by optimizing the balance between spin polarization and damping, enabling efficient switching even at scaled dimensions that increase storage density

Inventive Principle:

Principle #35Parameter changes

3Reliability

If MgO sublayers are introduced to enhance perpendicular magnetic anisotropy, then thermal energy barrier increases, but device structure complexity increases

Engineering Contradiction:

Improveperpendicular magnetic anisotropyVSAvoidmulti-layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent divides the magnetic free layer into multiple discrete sub-layers separated by thin non-magnetic MgO spacers. This segmentation creates multiple interfaces that collectively generate strong perpendicular magnetic anisotropy through interfacial effects, while the modular segmented structure allows for optimized fabrication processes compared to attempting to create equivalent properties in a single continuous layer

Inventive Principle:

Principle #1Segmentation

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

The solution provides MRAM devices with high thermal energy barriers and efficient spin transfer torque switching, enabling higher density and scalability, with MgO sublayers demonstrating anisotropy comparable to or exceeding tetragonally distorted Heusler Alloys, and maintaining exchange coupling between magnetic sublayers.

Implementation Method 1

the interface between CoFeB|MgO, and in particular the Fe—O bond is responsible for high PMA

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy: Anisotropy

Implementation Method 2

it is also well established that spin transfer torque (STT) is more efficient for switching between the parallel and anti-parallel states

Methodology Applied

Scientific EffectSpin transfer torque:

Data Source

PatentUS11646143B2Magnetic multi-layers containing MgO sublayers as perpendicularly magnetized magnetic electrodes for magnetic memory technology

Publication Date: 2023.05.09 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Various devices are described (along with methods for making them), where the device has a tunnel barrier sandwiched between two magnetic layers (one of the magnetic layers functioning as a free layer and the other of the magnetic layers functioning as a reference layer). One magnetic layer underlies the tunnel barrier and the other magnetic layer overlies the tunnel barrier, thereby permitting spin-polarized current to pass across the magnetic layers and through the tunnel barrier. At least one of the magnetic layers includes a metal oxide sublayer (e.g., an MgO sublayer) sandwiched between magnetic material.