CoFeB Memory Layer Perpendicular Anisotropy Thermal Stability

Solution Overview

Problem

Magnetic random access memory (MRAM) devices face challenges in maintaining thermal stability and reducing write current while miniaturizing, as the coercive force and thermal stability of magnetization inversion by spin injection are compromised due to the small volume of memory elements, leading to potential writing errors and increased power consumption.

Innovation Solution

A memory element with a layered structure comprising a magnetization-perpendicular memory layer, a magnetization-fixed layer, and a non-magnetic insulating layer, where spin-polarized electrons are injected to invert magnetization, utilizing a Co—Fe—B magnetic layer and oxide interfaces to enhance coercive force and thermal stability without increasing write current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the volume of memory elements is reduced for miniaturization, then the density of the memory device is improved, but the coercive force and thermal stability are compromised

Engineering Contradiction:

Improvevolume of memory elementVSAvoidthermal stability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent changes the magnetic anisotropy parameter from in-plane to perpendicular magnetization by modifying the interface structure between the CoFeB layer and oxide layers. This parameter change enables thermal stability to be maintained even at reduced volume by exploiting perpendicular magnetic anisotropy which provides stronger stabilization against thermal fluctuations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite structure consisting of CoFeB (cobalt-iron-boron) magnetic layer combined with oxide layers (such as MgO or Al2O3). This composite material system provides both the necessary magnetization properties and perpendicular magnetic anisotropy at the interface, enabling high thermal stability in miniaturized memory elements.

Inventive Principle:

Principle #40Composite materials

2Volume of moving object

If the volume of memory elements is reduced for miniaturization, then the density of the memory device is improved, but writing errors increase due to insufficient coercive force

Engineering Contradiction:

Improvevolume of memory elementVSAvoidwriting accuracy

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent changes the magnetic anisotropy parameter from in-plane to perpendicular magnetization by modifying the interface structure between the CoFeB layer and oxide layers. This parameter change enables thermal stability to be maintained even at reduced volume by exploiting perpendicular magnetic anisotropy which provides stronger stabilization against thermal fluctuations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The oxide layers (MgO or Al2O3) serve as intermediary layers that induce perpendicular magnetic anisotropy at the interface with the CoFeB layer. These intermediary oxide layers are crucial for providing the enhanced coercive force needed to prevent writing errors in miniaturized memory elements.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Use of energy by moving object

If spin injection is used for magnetization inversion, then the write current can be reduced, but thermal stability is compromised due to small volume

Engineering Contradiction:

Improvewrite currentVSAvoidthermal stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent changes the magnetic anisotropy parameter from in-plane to perpendicular magnetization by modifying the interface structure between the CoFeB layer and oxide layers. This parameter change enables thermal stability to be maintained even at reduced volume by exploiting perpendicular magnetic anisotropy which provides stronger stabilization against thermal fluctuations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite structure consisting of CoFeB (cobalt-iron-boron) magnetic layer combined with oxide layers (such as MgO or Al2O3). This composite material system provides both the necessary magnetization properties and perpendicular magnetic anisotropy at the interface, enabling high thermal stability in miniaturized memory elements.

Inventive Principle:

Principle #40Composite materials

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 effectively diminishes the write current while securing thermal stability and coercive force, enabling reliable information retention with reduced power consumption and improved magnetic anisotropy, suitable for high-density memory applications.

Implementation Method 1

an electron that is spin-polarized is injected in a lamination direction and thereby the magnetization direction of the memory layer is changed

Methodology Applied

Scientific EffectSpin injection:

Implementation Method 2

at least an interface that comes into contact with the memory layer is formed of an oxide film... the magnetization direction is perpendicular to a film face

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy: Anisotropy

Data Source

PatentUS9515254B2Storage element, memory and electronic apparatus

Publication Date: 2016.12.06 SONY GROUP CORP

AI summary

A storage element is provided. The storage element includes a memory layer having a first magnetization state of a first material; a fixed magnetization layer having a second magnetization state of a second material; an intermediate layer including a nonmagnetic material and provided between the memory layer and the fixed magnetization layer; wherein the first material includes Co—Fe—B alloy, and at least one of a non-magnetic metal and an oxide.