Perpendicular MTJ Structure With Dual Oxide Caps for Stable STT-MRAM

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Solution Overview

Problem

Spin transfer torque magnetic random access memory (STT-MRAM) devices face challenges in achieving thermal stability and cost-effective manufacturing, particularly as the size of perpendicular magnetic tunnel junctions (MTJs) are miniaturized, leading to degraded thermal stability and increased power consumption.

Innovation Solution

Incorporating a magnetic tunnel junction (MTJ) structure with a magnetic free layer and a magnetic reference layer separated by an insulating tunnel junction layer, along with a perpendicular enhancement layer (PEL) made of materials like cobalt, iron, and boron, and an anti-ferromagnetic coupling layer to enhance perpendicular anisotropy and thermal stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the size of perpendicular magnetic tunnel junctions is miniaturized, then device scalability is improved, but thermal stability deteriorates

Engineering Contradiction:

Improvedevice scalabilityVSAvoidthermal stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent employs composite material structures including CoFeB magnetic layers combined with MgO tunnel barriers, and introduces perpendicular enhancement layers comprising alternating ferromagnetic and non-magnetic metal layers. These composite structures provide both the miniaturization needed for scalability and the enhanced perpendicular magnetic anisotropy required to maintain thermal stability at smaller dimensions.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies material composition parameters by incorporating boron in CoFeB layers to enhance perpendicular anisotropy, and adjusts the thickness and composition of perpendicular enhancement layers. These parameter changes enable the maintenance of thermal stability as device size is reduced, resolving the contradiction between scalability and thermal stability.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the size of perpendicular magnetic tunnel junctions is miniaturized, then device scalability is improved, but power consumption increases

Engineering Contradiction:

Improvedevice scalabilityVSAvoidpower consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The use of CoFeB composite material with high spin polarization and the perpendicular enhancement layer structure enables more efficient spin transfer torque switching. This reduces the current density required for magnetization switching, thereby lowering power consumption while maintaining scalability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

By optimizing the composition and thickness parameters of the CoFeB magnetic layers and perpendicular enhancement layers, the patent achieves higher perpendicular magnetic anisotropy and lower damping coefficients. These parameter optimizations reduce the switching current density, enabling scalable devices with reduced power consumption.

Inventive Principle:

Principle #35Parameter changes

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 proposed solution improves the thermal stability and reduces power consumption of STT-MRAM devices by maintaining high perpendicular anisotropy and scalability, while being cost-effectively manufactured.

Implementation Method 1

enhance perpendicular anisotropy and thermal stability

Methodology Applied

Scientific EffectPerpendicular magnetic anisotropy: Anisotropy

Implementation Method 2

perpendicular enhancement layer (PEL) made of materials like cobalt, iron, and boron

Methodology Applied

Scientific EffectMagnetic interaction: Magnetism

Implementation Method 3

anti-ferromagnetic coupling layer to enhance perpendicular anisotropy and thermal stability

Methodology Applied

Scientific EffectAnti-ferromagnetic coupling: Magnetism

Implementation Method 4

Spin transfer torque magnetic random access memory (STT-MRAM) device

Methodology Applied

Scientific EffectSpin transfer torque:

Implementation Method 5

insulating tunnel junction layer separated by an insulating tunnel junction layer

Methodology Applied

Scientific EffectQuantum tunneling:

Data Source

PatentUS12133471B2Magnetic memory element including perpendicular enhancement layers and dual oxide cap layers

Publication Date: 2024.10.29 AVALANCHE TECHNOLOGY INC

AI summary

A magnetic memory element including first and second magnetic free layers having a variable magnetization direction substantially perpendicular to layer planes thereof; a first perpendicular enhancement layer (PEL) interposed between the first and second magnetic free layers; first and second magnetic reference layers having a first invariable magnetization direction substantially perpendicular to layer planes thereof; a second PEL interposed between the first and second magnetic reference layers; an insulating tunnel junction layer formed between the first magnetic free layer and reference layer; an anti-ferromagnetic coupling layer formed adjacent to the second magnetic reference layer; a magnetic fixed layer formed adjacent to the anti-ferromagnetic coupling layer and having a second invariable magnetization direction substantially opposite to the first invariable magnetization direction; a non-magnetic layer comprising oxygen and a transition metal and formed adjacent to the second magnetic free layer; and a magnesium oxide layer formed adjacent to the non-magnetic layer.