Magnetoresistive Element With Amorphous Interfacial Layer

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Solution Overview

Problem

The challenge is to enhance the thermal stability and magnetic anisotropy of ferromagnetic materials in magnetoresistive elements while reducing saturation magnetization and Gilbert damping factor to achieve high-density, low-power magnetic random access memories (MRAMs) with improved magnetization switching efficiency.

Innovation Solution

A magnetoresistive element is designed with a storage layer having low saturation magnetization and Gilbert damping factor, combined with an interfacial layer of CoFeB and a nonmagnetic MgO layer, where the CoFeB layer is crystallized using the MgO layer as a template, and an amorphous intermediate layer is used to improve crystal growth and spin polarization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the entire device size is reduced to improve density, then the density of nonvolatile memories is improved, but the thermal stability of ferromagnetic materials is degraded

Engineering Contradiction:

ImprovedensityVSAvoidthermal stability

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent changes the magnetic anisotropy parameter from in-plane to perpendicular magnetization, and modifies the material composition parameters by introducing specific interface layers (CoFeB, Ta, W) to achieve high thermal stability in miniaturized devices

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite multilayer structures combining different ferromagnetic materials (CoFeB, CoFe, CoNb) with nonmagnetic spacer layers (Ta, W, Ru) to create synthetic antiferromagnetic coupling that enhances thermal stability while maintaining small device footprint

Inventive Principle:

Principle #40Composite materials

2Area of moving object

If spin transfer torque magnetization switching is employed to reduce cell size, then the cell size is reduced, but the current density increases

Engineering Contradiction:

Improvecell sizeVSAvoidcurrent density

Core Design Contradiction:

Area of moving objectVSQuantity of substance

Solution Approach 1:

The patent changes the magnetization switching parameter by utilizing perpendicular magnetic anisotropy instead of in-plane magnetization, which reduces the critical current density required for switching while enabling smaller cell sizes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces localized interface magnetic anisotropy at specific layer interfaces (CoFeB/MgO, CoFe/Ta) to create regions of perpendicular magnetization that facilitate efficient spin transfer torque switching with reduced current density

Inventive Principle:

Principle #3Local quality

3Reliability

If materials with crystalline magnetic anisotropy are selected to achieve perpendicular magnetic anisotropy, then perpendicular magnetic anisotropy is achieved, but the manufacturing complexity increases

Engineering Contradiction:

Improveperpendicular magnetic anisotropyVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent introduces intermediate nonmagnetic spacer layers (Ta, W, Ru) between ferromagnetic layers to mediate the magnetic coupling and induce perpendicular magnetic anisotropy through interface effects, avoiding the need for complex crystalline material processing

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the need for mechanically aligning crystalline structures with a simpler layering approach where perpendicular magnetic anisotropy is induced by the interface structure and composition rather than bulk crystal orientation

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 configuration results in a magnetoresistive element with high perpendicular magnetic anisotropy and magnetoresistive ratio, enabling efficient magnetization switching with low current density and improved thermal stability, thus enhancing the performance of MRAMs.

Implementation Method 1

A number of MTJ elements including an MgO tunnel barrier layer and a layer with interface perpendicular magnetic anisotropy, such as a layer of CoFeB, are reported.

Methodology Applied

Scientific EffectInterface magnetic anisotropy: Anisotropy

Implementation Method 2

The MTJ elements are known to have a tunneling magnetoresistive (TMR) effect, and used as storage elements of memory cells in magnetic random access memories (MRAMs).

Methodology Applied

Scientific EffectTunneling magnetoresistive effect: Magnetoresistance

Implementation Method 3

The cell size of the MRAMs may be reduced by employing spin transfer torque magnetization switching, in which the magnetizations are controlled by means of spin polarized currents.

Methodology Applied

Scientific EffectSpin transfer torque:

Data Source

PatentUS9793469B2Magnetoresistive element and magnetic memory

Publication Date: 2017.10.17 KIOXIA CORP

AI summary

A magnetoresistive element according to an embodiment includes: a first magnetic layer; a second magnetic layer; a first nonmagnetic layer disposed between the first magnetic layer and the second magnetic layer; a third magnetic layer disposed between the first magnetic layer and the first nonmagnetic layer; and a layer having an amorphous structure, the layer containing two or more elements that are contained in the first magnetic layer, the layer being disposed between the first magnetic layer and the third magnetic layer.