Magnetic Memory Adjustment Layer for Leakage Field Reduction

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Solution Overview

Problem

Magnetic random access memory (MRAM) using Magnetic Tunnel Junction (MTJ) elements faces issues with increased leakage magnetic fields from the reference layer, which affect the magnetic coercive force and thermal stability of the memory layer, especially as micropatterning advances, leading to higher switching currents and reduced stability.

Innovation Solution

Incorporating an adjustment layer with a multilayered structure, including an interface layer and a magnetic layer with perpendicular magnetic anisotropy, positioned between the reference and memory layers to reduce leakage magnetic fields, while maintaining magnetic stability and allowing for efficient micropatterning by optimizing the thickness and saturation magnetization of the adjustment layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a magnetic layer with high magnetic anisotropic energy is used as the reference layer, then the magnetization is fixed and stable, but the leakage magnetic field from the reference layer increases

Engineering Contradiction:

Improvemagnetization stabilityVSAvoidleakage magnetic field

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

A nonmagnetic layer is introduced as an intermediary between the reference layer and the memory layer. This nonmagnetic layer acts as a magnetic field shield that blocks the leakage magnetic field from the reference layer while allowing the magnetic tunnel junction functionality to operate normally. The nonmagnetic layer has high perpendicular magnetic anisotropy energy density that creates a magnetization configuration which suppresses the stray field extending toward the memory layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If micropatterning of the MTJ element is advanced to reduce device size, then integration density increases, but the leakage magnetic field from the reference layer increases

Engineering Contradiction:

Improveintegration densityVSAvoidleakage magnetic field

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The nonmagnetic layer serves as a mediator that decouples the magnetic interaction between reference and memory layers. This allows the reference layer to maintain high magnetic anisotropic energy for stability while the nonmagnetic layer prevents the leakage field from affecting the memory layer, enabling continued micropatterning and scaling without proportional increases in leakage field effects.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If the leakage magnetic field acts on the memory layer, then the magnetic coercive force shifts, but a larger current is required for switching

Engineering Contradiction:

Improvemagnetic coercive force controlVSAvoidswitching current

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

The nonmagnetic layer blocks the leakage magnetic field from reaching the memory layer, thereby preventing shifts in the magnetic coercive force. This maintains the original switching characteristics of the memory layer, allowing switching to occur at the designed current level without requiring additional current to compensate for coercive force shifts.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 reduces the leakage magnetic field, decreases the magnetization switching current, enhances thermal stability, and facilitates easier micropatterning of the MTJ element, maintaining low resistance states for data storage while preventing shifts in magnetic coercive force.

Implementation Method 1

an adjustment layer provided on the second nonmagnetic layer and configured to reduce a leakage magnetic field from the reference layer

Methodology Applied

Scientific EffectMagnetic field shielding: Magnetic Field

Implementation Method 2

an MTJ (Magnetic Tunnel Junction) element using the magnetoresistive effect by which a resistance value changes in accordance with the direction of magnetization

Methodology Applied

Scientific EffectMagnetoresistive effect: Magnetoresistance

Implementation Method 3

the magnetization in the memory layer reverses due to torque externally given by a write operation

Methodology Applied

Scientific EffectMagnetic torque: Torque

Data Source

PatentUS8634238B2Magnetic memory element having an adjustment layer for reducing a leakage magnetic field from a reference layer and magnetic memory thereof

Publication Date: 2014.01.21 KIOXIA CORP

AI summary

According to one embodiment, a magnetic memory element includes a memory layer, a first nonmagnetic layer, a reference layer, a second nonmagnetic layer, and an adjustment layer which are stacked. The adjustment layer is configured to reduce a leakage magnetic field from the reference layer. The adjustment layer is formed by stacking an interface layer provided on the second nonmagnetic layer, and a magnetic layer having magnetic anisotropy perpendicular to a film surface. Saturation magnetization of the interface layer is larger than that of the magnetic layer.