MTJ Diffusion Barrier Layer for Low Resistance and High TMR

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Solution Overview

Problem

Magnetic tunnel junction (MTJ) elements face performance degradation due to oxygen diffusion during high-temperature annealing, affecting their resistance and tunnel magnetoresistance coefficient, primarily because of the diffusion of oxygen atoms to elements with high affinity like tantalum, tungsten, or molybdenum, leading to increased resistance and decreased TMR coefficient.

Innovation Solution

Incorporating a diffusion barrier cap layer made of an amorphous, nonmagnetic film such as Co-Hf, which prevents oxygen diffusion and the migration of metallic atoms, thereby maintaining the crystalline structure and improving the MTJ element's performance by reducing resistance and enhancing the TMR coefficient.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high-temperature annealing is performed to improve crystalline structure, then magnetic properties are enhanced, but oxygen diffusion occurs causing performance degradation

Engineering Contradiction:

Improvemagnetic propertiesVSAvoidoxygen diffusion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A diffusion barrier layer is introduced as an intermediary between the MTJ element and the surrounding environment. This barrier layer specifically blocks oxygen diffusion while allowing the high-temperature annealing process to proceed, thus protecting the MTJ element from oxygen contamination during the crystalline structure formation process

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates an oxygen-free or low-oxygen environment around the MTJ element by using diffusion barrier layers made of materials with low oxygen permeability. This inert environment approach prevents oxygen from reaching the MTJ element during high-temperature annealing, allowing the process to improve magnetic properties without causing oxygen diffusion damage

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

2Reliability

If diffusion barrier layer is added to prevent oxygen diffusion, then resistance is reduced and TMR coefficient increases, but device complexity increases

Engineering Contradiction:

Improvetunnel magnetoresistance coefficientVSAvoidlayer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent optimizes the parameters of the diffusion barrier layer, including thickness (typically 1-10 nm), material composition, and deposition conditions, to achieve effective oxygen blocking with minimal impact on device performance. By carefully controlling these parameters, the barrier layer provides protection while maintaining reasonable device complexity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The diffusion barrier layer is constructed using composite material structures, such as alternating layers of different materials (e.g., TaN/WN combinations or CoFeB/MgO structures), which provide enhanced oxygen blocking capability while managing the overall device complexity through functional integration

Inventive Principle:

Principle #40Composite materials

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 use of a Co-Hf diffusion barrier cap layer results in a lower resistance area product (RA) and higher tunnel magnetoresistance (TMR) coefficient, enabling better low-power write performance and a broader read window for MTJ elements, thus improving their overall performance and reliability.

Implementation Method 1

Incorporating a diffusion barrier cap layer made of an amorphous, nonmagnetic film such as Co-Hf, which prevents oxygen diffusion and the migration of metallic atoms

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 2

Magnetic tunnel junctions (MTJs) can be used in hard disk drives and/or RAM... a magnetic random access memory (MRAM) device... In each MRAM cell, a magnetic tunnel junction (MTJ) element

Methodology Applied

Scientific EffectTunnel magnetoresistance: Magnetoresistance

Data Source

PatentUS20230337547A1Magnetic tunnel junction (MTJ) element and its fabrication process

Publication Date: 2023.10.19 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A magnetic tunnel junction (MTJ) element is provided. The MTJ element includes a reference layer, a tunnel barrier layer disposed over the reference layer, a free layer disposed over the tunnel barrier layer, and a diffusion barrier layer disposed over the free layer. The MTJ element in accordance with the present disclosure exhibits a low resistance desired for a low-power write operation, and a high TMR coefficient desired for a low bit-error-rate (BER) read operation.