Magnetoresistive Element with Crystallization Promoting Layer

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Solution Overview

Problem

In magnetoresistive random access memories (MRAMs), the current-field write method requires high currents for magnetization reversal, making it difficult to use low current and small-sized memory cells with capacities larger than 256 Mbits, and the spin-injection writing method faces challenges in achieving low current magnetization reversal due to the size of the MR elements.

Innovation Solution

A magnetoresistive element with a magnetization reference layer and a magnetization free layer, separated by an intermediate layer, where at least one of the layers includes an interfacial magnetic layer crystallized from an amorphous structure and a crystallization promoting layer, allowing for magnetization direction change with a low current via spin-injection writing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the current-field write method is used for magnetization reversal, then the magnetization can be reversed, but high current is required which limits scalability to large capacities

Engineering Contradiction:

Improvemagnetization reversalVSAvoidscalability

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent replaces the current-field write method (which uses magnetic field generated by current) with a spin-injection write method that utilizes spin transfer torque. This substitution allows magnetization reversal through direct spin angular momentum transfer from spin-polarized electrons, eliminating the need for high magnetic fields and enabling lower operating currents for scalable MRAM designs

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent modifies the magnetic layer structure by introducing an amorphous magnetic layer with specific composition (CoFeB or CoFeSiB) and controlling its thickness (1-5 nm). By adjusting the composition ratio and thickness parameters, the coercive force is reduced to enable low-current spin-injection writing while maintaining thermal stability for data retention

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the spin-injection writing method is used, then lower current can be applied, but the resistance of the TMR element must be reduced to achieve effective writing

Engineering Contradiction:

Improvewriting currentVSAvoidTMR element resistance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent employs composite material structures including amorphous magnetic layers (CoFeB or CoFeSiB), crystalline magnetic layers (CoFeB, CoFe, or Co), and oxide barrier layers (MgO or Al2O3). This composite structure optimizes both the TMR ratio and the resistance characteristics, enabling low-resistance operation while maintaining effective spin-injection writing capability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent introduces local quality variations by creating an amorphous magnetic layer with specific composition and thickness (1-5 nm) between the crystalline magnetic layers. This localized amorphous region with tailored properties reduces the overall resistance of the TMR element while maintaining the spin-polarization necessary for spin-injection writing

Inventive Principle:

Principle #3Local quality

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 enables magnetization reversal with a low current, improving scalability and reducing the resistance of the MRAM, thus enabling efficient low-resistance spin-injection writing in MRAMs.

Implementation Method 1

an interfacial magnetic layer formed in contact with the intermediate layer, and having a crystalline phase crystallized from an amorphous structure

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Implementation Method 2

a crystallization promoting layer formed in contact with the interfacial magnetic layer on the opposite side from the intermediate layer, and promoting crystallization of the interfacial magnetic layer

Methodology Applied

Scientific EffectCrystallization promotion: Crystallisation

Implementation Method 3

magnetoresistive random access memories (hereinafter also referred to as MRAMs) that take advantage of tunneling magneto resistance (hereinafter also referred to as TMR)

Methodology Applied

Scientific EffectTunneling magnetoresistance: Magnetoresistance

Implementation Method 4

a write method that utilizes spin momentum transfers (SMT) (a spin-injection writing method or spin-transfer-torque writing method) has been suggested

Methodology Applied

Scientific EffectSpin transfer torque:

Data Source

PatentUS8154915B2Magnetoresistive element and magnetoresistive random access memory including the same

Publication Date: 2012.04.10 KIOXIA CORP

AI summary

The present invention provides a low-resistance magnetoresistive element of a spin-injection write type. A crystallization promoting layer that promotes crystallization is formed in contact with an interfacial magnetic layer having an amorphous structure, so that crystallization is promoted from the side of a tunnel barrier layer, and the interface between the tunnel barrier layer and the interfacial magnetic layer is adjusted. With this arrangement, it is possible to form a magnetoresistive element that has a low resistance so as to obtain a desired current value, and has a high TMR ratio.