MRAM Memory Cell Ferrimagnetic Shielding for Magnetization Saturation

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Solution Overview

Problem

Conventional toggle-type magnetic random access memory (MRAM) faces challenges in preventing composite magnetization from approaching saturation and suppressing switching between magnetization states of ferromagnetic layers due to thermal disturbances, which affects data reliability and manufacturing yields.

Innovation Solution

A memory cell design incorporating a laminated ferrimagnetic structure with a free layer and a fixed layer, where a nonmagnetic layer is interposed between them, adjusts the magnetic field magnitude to prevent saturation and includes a laminated ferrimagnetic structure substance that acts as a shield or keeper to control the magnetic field, ensuring stable magnetization states during write operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a laminated ferrimagnetic structure is used in the free layer to enable toggle operations, then write operation selectivity is improved, but composite magnetization approaches saturation making the system vulnerable to thermal disturbances

Engineering Contradiction:

Improvewrite operation selectivityVSAvoidmagnetization saturation state

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

A laminated ferrimagnetic structure substance is introduced as an intermediary element between the write word line and the magneto-resistive element. This substance mediates the magnetic field interaction by absorbing excess magnetic flux during write operations, preventing the free layer's composite magnetization from reaching saturation while maintaining effective write selectivity through controlled magnetic coupling.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the magnetic parameters of the system by introducing a laminated ferrimagnetic structure with specific magnetization characteristics. This structure modifies the magnetic field distribution and intensity reaching the free layer, adjusting the effective magnetic field parameters to prevent saturation while preserving toggle operation functionality.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the magnetic field magnitude is increased to ensure reliable write operations, then write operation reliability is improved, but thermal disturbance-induced switching between magnetization states occurs

Engineering Contradiction:

Improvewrite operation reliabilityVSAvoidthermal disturbance sensitivity

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The laminated ferrimagnetic structure substance acts as a magnetic cushioning element positioned beforehand in the magnetic field path. It absorbs and distributes excess magnetic energy before it reaches the free layer, providing protective cushioning against magnetic field over-saturation while allowing sufficient field strength for reliable write operations.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The invention converts the potentially harmful effect of strong magnetic fields causing saturation into a beneficial effect by using the laminated ferrimagnetic structure to channel and regulate the magnetic flux. The structure transforms excessive magnetic field intensity into controlled magnetic coupling, turning what would be a harmful saturation effect into a controlled write mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 design effectively prevents composite magnetization from reaching saturation, enhances data reliability, and improves manufacturing yields by suppressing thermal disturbance-induced switching, thereby ensuring reliable and cost-effective toggle operations in MRAM.

Implementation Method 1

adjusts the magnetic field magnitude which acts on the free layer

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

composite magnetization from approaching saturation

Methodology Applied

Scientific EffectMagnetization: Magnetism

Implementation Method 3

a tunnel magneto-resistive element which includes a free layer having a laminated ferrimagnetic structure, a fixed layer, and a nonmagnetic layer interposed between the free layer and the fixed layer

Methodology Applied

Scientific EffectTunneling:

Implementation Method 4

a magnetization direction of the laminated ferri-fixed layer 103 is fixed by the antiferromagnetic layer 104

Methodology Applied

Scientific EffectAntiferromagnetism:

Data Source

PatentUS7916520B2Memory cell and magnetic random access memory

Publication Date: 2011.03.29 NEC CORP

AI summary

A memory cell is used which includes a plurality of magneto-resistive elements and a plurality of laminated ferrimagnetic structure substances. The plurality of the magneto-resistive elements are placed corresponding to respective positions where a plurality of first wirings extended in a first direction intersects with a plurality of second wirings extended in a second direction which is substantially perpendicular to the first direction. The plurality of the laminated ferrimagnetic structure substances corresponds to the plurality of the magneto-resistive elements, respectively, is placed to have a distance of a predetermined range from the respective plurality of the magneto-resistive elements, and has a laminated ferrimagnetic structure. The magneto-resistive element includes a free layer having a laminated ferrimagnetic structure, a fixed layer, and a nonmagnetic layer interposed between the free layer and the fixed layer.