Magnetic Memory with Boron-Graded Storage Layer for Low Write Current

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Solution Overview

Problem

Miniaturization and low electric current challenges in magnetic random access memory (MRAM) devices, particularly in magnetic tunnel junction (MTJ) elements, where reducing element size increases coercivity and write current, and spin injection write schemes face difficulties with decreasing spin polarized electron injection.

Innovation Solution

A magnetic memory structure comprising a substrate with a magnetoresistive element featuring a first and second magnetic layer with varying boron content regions, and a tunnel barrier layer, where annealing processes create crystalline regions closer to the tunnel barrier, optimizing magnetism and reducing boron content to achieve efficient magnetization reversal with lower electric currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If element size is reduced in magnetic-field write scheme, then miniaturization is achieved, but coercivity increases and write current increases

Engineering Contradiction:

Improveelement sizeVSAvoidwrite current

Core Design Contradiction:

Volume of moving objectVSUse of energy by moving object

Solution Approach 1:

The storage layer is divided into regions with different boron concentrations: a first region with higher boron content and a second region with lower boron content. This local variation in composition allows different parts of the storage layer to have different magnetic properties, enabling reduced write current while maintaining stability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the chemical composition parameter by varying boron concentration within the storage layer. By controlling the boron content distribution (higher in first region, lower in second region), the magnetic anisotropy and coercivity are optimized to achieve both miniaturization and low write current operation.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If element size is reduced in spin injection write scheme, then miniaturization is achieved, but spin polarized electron injection decreases

Engineering Contradiction:

Improveelement sizeVSAvoidspin polarized electrons

Core Design Contradiction:

Volume of moving objectVSQuantity of substance

Solution Approach 1:

The storage layer incorporates regions with different boron concentrations to optimize spin polarization. The first region with higher boron content provides stable magnetization, while the second region with lower boron content enhances spin injection efficiency, compensating for the reduced element volume.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The storage layer is constructed as a composite structure with varying boron concentrations, combining regions with different magnetic and spin transport properties. This composite approach maintains sufficient spin polarized electron injection even as the overall element size is reduced for miniaturization.

Inventive Principle:

Principle #40Composite materials

3Use of energy by moving object

If boron content is reduced in storage layer, then magnetization reversal efficiency improves, but magnetic stability may deteriorate

Engineering Contradiction:

Improvemagnetization reversal efficiencyVSAvoidmagnetic stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

Different regions of the storage layer have different boron concentrations to balance stability and reversibility. The first region with higher boron content maintains magnetic stability, while the second region with lower boron content facilitates efficient magnetization reversal, resolving the trade-off between these two requirements.

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

The proposed structure enables efficient miniaturization and low electric current operation in MRAM devices by optimizing magnetism and crystallinity, facilitating reliable information storage with reduced parasitic capacitance and improved write performance.

Implementation Method 1

a magnetic memory comprising a magnetoresistive element... storing '1' or '0' information in a memory cell by using a magnetoresistive effect... resistance of the MTJ element varies depending on the magnetization directions

Methodology Applied

Scientific EffectMagnetoresistive effect: Magnetoresistance

Implementation Method 2

annealing processes create crystalline regions closer to the tunnel barrier, optimizing magnetism and reducing boron content

Methodology Applied

Scientific EffectAnnealing: Annealing

Data Source

PatentUS9130143B2Magnetic memory and method for manufacturing the same

Publication Date: 2015.09.08 KIOXIA CORP

AI summary

According to one embodiment, a magnetic memory is disclosed. The magnetic memory includes a substrate, and a magnetoresistive element provided on the substrate. The magnetoresistive element includes a first magnetic layer, a tunnel barrier layer on the first magnetic layer, and a second magnetic layer on the tunnel barrier layer. The first magnetic layer or the second magnetic layer includes a first region, second region, and third region whose ratios of crystalline portion are higher in order closer to the tunneling barrier.