Magnetic Tunnel Junction Diffusion Barrier for MRAM

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Solution Overview

Problem

The existing magnetic tunnel junction (MTJ) devices face issues with diffusion of materials from synthetic antiferromagnetic (SyAF) layers and capping layers, which deteriorate the crystallinity and magnetoresistance ratio, leading to reduced operation speed and increased processing costs.

Innovation Solution

A memory device is designed with a diffusion barrier between the magnetic tunnel junction and the capping layer, using materials like tungsten for the capping layer and iron for the diffusion barrier, and platinum for the seed layer to promote FCC (111) growth of SyAF layers, ensuring perpendicular magnetization and maintaining high magnetoresistance ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If SyAF layers and capping layers are formed on the magnetic tunnel junction, then the device structure is completed and protected, but material diffusion occurs which deteriorates the crystallinity and magnetoresistance ratio

Engineering Contradiction:

Improvedevice structure completenessVSAvoidcrystallinity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

A diffusion barrier layer is introduced as an intermediary between the SyAF layers/capping layers and the magnetic tunnel junction. This barrier layer prevents material diffusion from the SyAF and capping layers into the MTJ, thereby preserving the crystallinity and magnetoresistance ratio while still allowing the device structure to be completed and protected.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If diffusion barrier is added to prevent material diffusion, then crystallinity and magnetoresistance ratio are maintained, but device structure complexity increases

Engineering Contradiction:

ImprovecrystallinityVSAvoidlayer structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The device structure is segmented into distinct functional layers with the diffusion barrier as a separate, dedicated component. This segmentation allows the barrier to perform its specific function of preventing material diffusion without interfering with the other layers, maintaining crystallinity while organizing the complexity into manageable, functionally-separated segments.

Inventive Principle:

Principle #1Segmentation

3Ease of manufacture

If conventional materials are used for SyAF layers, then processing is simpler, but material diffusion deteriorates the magnetic tunnel junction properties

Engineering Contradiction:

Improveprocessing simplicityVSAvoidmagnetoresistance ratio

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The diffusion barrier layer serves as a mediator that enables the use of conventional SyAF layer materials without compromising the magnetoresistance ratio. The barrier intercepts and prevents material diffusion before it can reach and deteriorate the magnetic tunnel junction, thus maintaining reliability while allowing processing simplicity to be preserved.

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

The solution prevents material diffusion, preserves the BCC (100) crystal structure, enhances operating speed, and reduces processing costs by maintaining high magnetoresistance ratio and perpendicular magnetic anisotropy even at elevated temperatures.

Implementation Method 1

A memory device is designed with a diffusion barrier between the magnetic tunnel junction and the capping layer

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 2

magnetic random access memory (MRAM) that uses resistance changes in a magnetic tunnel junction (MTJ) depending on the magnetization state of a ferromagnetic material

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Implementation Method 3

a spin-transfer torque (STT) phenomenon generated by electron injection

Methodology Applied

Scientific EffectSpin-transfer torque:

Implementation Method 4

platinum for the seed layer to promote FCC (111) growth of SyAF layers

Methodology Applied

Scientific EffectEpitaxial growth: Epitaxy

Data Source

PatentUS10854254B2Memory device

Publication Date: 2020.12.01 INDUSTRY UNIVERSITY COOPERATION FOUNDATION HANYANG UNIVERSITY

AI summary

The present invention provides a memory device in which a lower electrode, a seed layer, synthetic antiferromagnetic layers, a separation layer, a magnetic tunnel junction, a capping layer, and an upper electrode are formed on a substrate in a laminated manner, wherein a diffusion barrier is formed between the magnetic tunnel junction and the capping layer. In addition, the present invention provides a memory device in which a lower electrode, a seed layer, synthetic antiferromagnetic layers, a separation layer, a magnetic tunnel junction, a capping layer, and an upper electrode are formed on a substrate in a laminated manner, wherein the seed layer is formed of a material that allows the synthetic antiferromagnetic layers to grow in the FCC (111) direction.