Composite Free Layer MRAM Reduces Switching Field

Solution Overview

Problem

In high-density magnetic random access memory (MRAM) applications, there is a need to reduce switching fields and current applied to conductive lines while maintaining a high magnetoresistance (MR) ratio and achieving uniform switching behavior across memory units.

Innovation Solution

The MRAM structure incorporates a composite free layer with a first magnetic layer, a spacer layer, and a second magnetic layer sequentially stacked over a barrier layer, allowing parallel coupling between the magnetic layers, which reduces switching fields and currents while maintaining a high MR ratio and improving switching uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If memory unit size is reduced to increase density, then storage capacity is improved, but switching field increases and current consumption increases

Engineering Contradiction:

Improvestorage capacityVSAvoidswitching field

Core Design Contradiction:

Quantity of substanceVSForce

Solution Approach 1:

The free layer is segmented into multiple magnetic sub-layers (first magnetic layer and second magnetic layer) with different magnetization directions. This segmentation allows the switching operation to be distributed across multiple layers rather than requiring a single high-field switch, thereby reducing the overall switching field while maintaining high storage density

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs a composite magnetic layer structure where the first magnetic layer and second magnetic layer are made of different magnetic materials or have different thicknesses. This composite structure creates favorable magnetic anisotropy and reduces the switching field through magnetic coupling effects, enabling high-density storage without proportionally increasing switching requirements

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If memory unit size is reduced to increase density, then storage capacity is improved, but current applied to conductive lines increases

Engineering Contradiction:

Improvestorage capacityVSAvoidcurrent consumption

Core Design Contradiction:

Quantity of substanceVSUse of energy by moving object

Solution Approach 1:

The free layer is segmented into multiple magnetic sub-layers (first magnetic layer and second magnetic layer) with different magnetization directions. This segmentation allows the switching operation to be distributed across multiple layers rather than requiring a single high-field switch, thereby reducing the overall switching field while maintaining high storage density

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs a composite magnetic layer structure where the first magnetic layer and second magnetic layer are made of different magnetic materials or have different thicknesses. This composite structure creates favorable magnetic anisotropy and reduces the switching field through magnetic coupling effects, enabling high-density storage without proportionally increasing switching requirements

Inventive Principle:

Principle #40Composite materials

3Force

If switching field is reduced for high density applications, then current consumption is reduced, but switching uniformity deteriorates

Engineering Contradiction:

Improveswitching fieldVSAvoidswitching uniformity

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

Different regions of the free layer are assigned different magnetic properties through the multi-layer structure. The first magnetic layer and second magnetic layer have different magnetization directions and material compositions, creating localized magnetic characteristics that collectively improve switching uniformity across the entire memory unit while maintaining reduced switching fields

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs a composite magnetic layer structure where the first magnetic layer and second magnetic layer are made of different magnetic materials or have different thicknesses. This composite structure creates favorable magnetic anisotropy and reduces the switching field through magnetic coupling effects, enabling high-density storage without proportionally increasing switching requirements

Inventive Principle:

Principle #40Composite materials

4Measurement precision

If MR ratio is maintained high for data storage, then reading accuracy is improved, but switching field increases

Engineering Contradiction:

Improvereading accuracyVSAvoidswitching field

Core Design Contradiction:

Measurement precisionVSForce

Solution Approach 1:

The patent employs a composite magnetic layer structure where the first magnetic layer and second magnetic layer are made of different magnetic materials or have different thicknesses. This composite structure creates favorable magnetic anisotropy and reduces the switching field through magnetic coupling effects, enabling high-density storage without proportionally increasing switching requirements

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The free layer is segmented into multiple magnetic sub-layers (first magnetic layer and second magnetic layer) with different magnetization directions. This segmentation allows the switching operation to be distributed across multiple layers rather than requiring a single high-field switch, thereby reducing the overall switching field while maintaining high storage density

Inventive Principle:

Principle #1Segmentation

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 achieves a balanced MR ratio of 40-45% with reduced switching fields (25-35 Oe) and improved switching uniformity, suitable for high-speed and high-density MRAM applications, ensuring efficient data storage and reading performance.

Implementation Method 1

the spacer layer allows parallel coupling between the first and second magnetic layers

Methodology Applied

Scientific EffectExchange coupling:

Implementation Method 2

a bit status of the stored data can be obtained by distinguishing the magnetoresistance (MR) thereof

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS7583529B2Magnetic tunnel junction devices and magnetic random access memory

Publication Date: 2009.09.01 IND TECH RES INST

AI summary

A magnetic random access memory (MRAM) is disclosed. The MRAM includes a first electrode, an antiferromagnetic layer formed over the first electrode, a pinned layer formed over the antiferromagnetic layer, a barrier layer formed over the pinned layer, a composite free layer formed over the barrier layer, and a second electrode formed over the composite free layer. The composite free layer includes a first magnetic layer, a spacer layer and a second magnetic layer sequentially stacked over the barrier layer and the spacer layer allows parallel coupling between the first and second magnetic layers. A magnetic tunnel junction (MTJ) device suitable for a memory unit of a magnetic memory device is also provided.