Modified Double Magnetic Tunnel Junction for Low Current Switching

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Solution Overview

Problem

The existing double magnetic tunnel junction (DMTJ) structure reduces switching current but also decreases tunnel magnetoresistance (TMR), making it difficult to achieve efficient switching and speedy readout in spin-transfer torque (STT) MRAM.

Innovation Solution

A modified double magnetic tunnel junction (mDMTJ) structure is introduced, which includes a non-magnetic, spin-conducting metallic layer sandwiched between the magnetic free layer and the first tunnel barrier layer, along with a second tunnel barrier layer and a second magnetic reference layer, allowing for efficient switching at low current and high TMR.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a double magnetic tunnel junction (DMTJ) structure is used, then switching current is reduced, but tunnel magnetoresistance (TMR) is also reduced

Engineering Contradiction:
Improveswitching currentVSAvoidtunnel magnetoresistance (TMR)
Core Design Contradiction:
Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

A non-magnetic, spin-conducting metallic layer is introduced as an intermediary between the magnetic free layer and the first tunnel barrier layer. This intermediary layer enables efficient spin transport while preserving high TMR signals, resolving the contradiction between reduced switching current and maintained measurement precision

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a composite structure combining magnetic layers, tunnel barrier layers, and a non-magnetic spin-conducting metallic layer. This composite material approach allows simultaneous optimization of switching current reduction and TMR preservation through carefully selected material properties and layer configurations

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 mDMTJ structure enables efficient switching at low current (less than 20 to 50 μA) and high TMR (up to 100-200%), improving memory performance by reducing spin-torque disturbances and preserving high TMR signals.

Implementation Method 1

a non-magnetic, spin-conducting metallic layer sandwiched between a magnetic free layer and a first tunnel barrier layer

Methodology Applied
Scientific EffectSpin transport:

Implementation Method 2

tunnel magnetoresistance (TMR), making it difficult to achieve efficient switching and speedy readout

Methodology Applied
Scientific EffectTunnel magnetoresistance (TMR): Magnetoresistance

Data Source

PatentUS11171283B2Modified double magnetic tunnel junction structure suitable for BEOL integration
Publication Date: 2021.11.09 INTERNATIONAL BUSINESS MACHINE CORPORATION
  • US11171283B2 patent drawing
  • US11171283B2 patent drawing
  • US11171283B2 patent drawing

AI summary

A modified double magnetic tunnel junction (mDMTJ) structure is provided which includes a non-magnetic, spin-conducting metallic layer sandwiched between a magnetic free layer and a first tunnel barrier layer; the first tunnel barrier layer contacts a first magnetic reference layer. A second tunnel barrier layer is located on the magnetic free layer and a second magnetic reference layer is located on the second tunnel barrier layer. The mDMTJ structure of the present application exhibits efficient switching (at a low current) and speedy readout (high TMR).