Spin-Orbit Torque Wiring with Low-Resistivity Insertion Layers

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Solution Overview

Problem

Existing magnetoresistance effect elements face challenges in reducing the voltage required for writing data, particularly due to the high electrical resistance of heavy metals used in spin-orbit torque wiring.

Innovation Solution

The introduction of a magnetization rotational element with a spin-orbit torque wiring that includes multiple spin generation layers and insertion layers with lower electrical resistivity, such as Mg, Al, Si, Ti, Cr, Fe, Co, Cu, Ga, Ge, and Ag, to reduce the overall resistance and voltage required for writing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If heavy metals (Ta, W) are used for spin-orbit torque wiring to generate significant SOT, then spin injection efficiency is improved, but electrical resistance increases and writing voltage increases

Engineering Contradiction:

Improvespin injection efficiencyVSAvoidwriting voltage

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent employs a composite wiring structure consisting of a spin-orbit torque wiring layer (heavy metal for spin injection) and a conductive wiring layer (low-resistance material) formed in a groove within the spin-orbit torque wiring. This composite configuration allows the heavy metal to generate spin-orbit torque while the conductive layer provides a low-resistance current path, thereby reducing overall electrical resistance and writing voltage without compromising spin injection efficiency

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The wiring is segmented into functional zones: a spin-orbit torque wiring layer for spin injection, a groove region, and a conductive wiring layer for current transport. This segmentation separates the spin generation function from the current transport function, allowing optimization of each layer independently - the heavy metal layer for spin-orbit interaction and the conductive layer for low resistance

Inventive Principle:

Principle #1Segmentation

2Reliability

If heavy metals are used for spin-orbit torque wiring, then spin Hall angle is increased, but electrical resistance increases

Engineering Contradiction:

Improvespin Hall angleVSAvoidelectrical resistance

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent creates a composite wiring system where the spin-orbit torque wiring layer (heavy metal with high spin Hall angle) is combined with a conductive wiring layer (low-resistance material) in a groove within the spin-orbit torque wiring. This composite structure enables the heavy metal to provide high spin Hall angle while the conductive layer compensates for the high electrical resistance

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The conductive wiring layer acts as an intermediary that provides a low-resistance current path between the spin-orbit torque wiring layer and the magnetoresistance effect element. This intermediary layer allows current to flow with lower resistance while the spin-orbit torque wiring layer maintains its high spin Hall angle property for efficient spin injection

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 effectively reduces the voltage needed for writing data by improving the electrical conductivity of the spin-orbit torque wiring, while maintaining the efficiency of spin injection into the ferromagnetic layers.

Implementation Method 1

A spin-orbit torque (SOT) is induced by means of a spin current generated due to a spin-orbit interaction or a Rashba effect in an interface between materials of different kinds

Methodology Applied

Scientific EffectSpin-orbit interaction:

Implementation Method 2

A spin-orbit torque (SOT) is induced by means of a spin current generated due to a spin-orbit interaction or a Rashba effect in an interface between materials of different kinds

Methodology Applied

Scientific EffectRashba effect:

Implementation Method 3

the insertion layer has a lower electrical resistivity than the spin generation layers

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS12290002B2Magnetization rotational element, magnetoresistance effect element, semiconductor element, magnetic recording array, and method for manufacturing magnetoresistance effect element

Publication Date: 2025.04.29 TDK CORP

AI summary

A magnetization rotational element includes a spin-orbit torque wiring, and a first ferromagnetic layer which is located in a first direction with respect to the spin-orbit torque wiring and in which spins are injected from the spin-orbit torque wiring. The spin-orbit torque wiring has a plurality of spin generation layers and insertion layers located between the plurality of spin generation layers in the first direction. The insertion layers have a lower electrical resistivity than the spin generation layers.