MTJ Stacks with Anisotropy Enhancing and Crystallization Barrier Layers

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Solution Overview

Problem

Perpendicular magnetic tunnel junction (MTJ) structures face challenges in achieving both high TMR ratio and thermal stability, with perpendicular magnetic anisotropy leading to thermal instability and low TMR ratio due to crystal mismatch.

Innovation Solution

Incorporating a magnetic anisotropy enhancing layer and a crystallization barrier layer in the MTJ structure, where the crystallization barrier layer improves crystal alignment between the free magnetic layer and the tunneling layer, and the magnetic anisotropy enhancing layer promotes out-of-plane alignment, while the crystallization barrier layer reduces templating effects and enhances thermal stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If perpendicular magnetic anisotropy is achieved through coupling to a strongly perpendicular film, then thermal stability is improved, but TMR ratio tends to be low due to crystal mismatch

Engineering Contradiction:

Improvethermal stabilityVSAvoidTMR ratio

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

A crystallization barrier layer is introduced as an intermediary between the magnetic anisotropy enhancing layer and the free magnetic layer. This barrier layer prevents direct crystal templating while allowing magnetic coupling, thereby resolving the crystal mismatch problem that causes low TMR ratio while maintaining the thermal stability provided by the perpendicular film structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The structure is segmented into distinct functional layers: a magnetic anisotropy enhancing layer for thermal stability, a crystallization barrier layer to prevent crystal mismatch, and a free magnetic layer for TMR performance. This segmentation allows each layer to optimize its specific function without compromising the others

Inventive Principle:

Principle #1Segmentation

2Reliability

If perpendicular magnetic anisotropy is achieved with a thin free magnetic layer, then TMR ratio is improved, but thermal instability increases significantly

Engineering Contradiction:

ImproveTMR ratioVSAvoidthermal stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The magnetic anisotropy enhancing layer acts as a counterweight to the thermal instability of the thin free magnetic layer. By providing strong perpendicular magnetic anisotropy through magnetic coupling, it compensates for the thermal instability that would otherwise result from the thin layer configuration, enabling both high TMR ratio and thermal stability

Inventive Principle:

Principle #8Anti-weight (Counterweight)

3Shape

If the free magnetic layer is made sufficiently thin to achieve perpendicular magnetic anisotropy, then perpendicular alignment is achieved, but thermal instability shortens non-volatile lifetime

Engineering Contradiction:

Improvemagnetic alignmentVSAvoidnon-volatile lifetime

Core Design Contradiction:

ShapeVSDuration of action of stationary object

Solution Approach 1:

The crystallization barrier layer serves as a mediator that allows the thin free magnetic layer to maintain perpendicular magnetic alignment while protecting it from thermal degradation. The barrier layer blocks harmful crystal templating effects from the enhancing layer, enabling the thin structure to achieve both perpendicular alignment and extended non-volatile lifetime through improved thermal stability

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 enhances the TMR ratio and thermal stability of the MTJ, improving the non-volatile lifetime of the memory device while maintaining a high TMR ratio, enabling more reliable bit storage.

Implementation Method 1

the crystallization barrier layer improves crystal alignment between the free magnetic layer and the tunneling layer

Methodology Applied

Scientific EffectCrystal alignment: Epitaxy

Implementation Method 2

PMA can also be achieved through coupling to a strongly perpendicular film disposed adjacent to the free layer

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy: Anisotropy

Implementation Method 3

Polarization states of one ferromagnetic layer are switched relative to a fixed polarization of the second ferromagnetic layer via the spin transfer torque phenomenon

Methodology Applied

Scientific EffectSpin transfer torque: Angular Momentum

Implementation Method 4

STTM devices are non-volatile memory devices that utilize a phenomenon known as tunnelling magnetoresistance (TMR)

Methodology Applied

Scientific EffectTunneling magnetoresistance: Magnetoresistance

Data Source

PatentUS8836056B2Perpendicular MTJ stacks with magnetic anisotropy enhancing layer and crystallization barrier layer

Publication Date: 2014.09.16 INTEL CORP

AI summary

Magnetic tunnel junctions (MTJ) suitable for spin transfer torque memory (STTM) devices, include perpendicular magnetic layers and one or more anisotropy enhancing layer(s) separated from a free magnetic layer by a crystallization barrier layer. In embodiments, an anisotropy enhancing layer improves perpendicular orientation of the free magnetic layer while the crystallization barrier improves tunnel magnetoresistance (TMR) ratio with better alignment of crystalline texture of the free magnetic layer with that of a tunneling layer.