Doped SOT Induction Structure for Field-Free MRAM Switching

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Solution Overview

Problem

X-type SOT-MRAM devices require external assistant magnetic fields for switching the free magnetic layer, complicating the cell structure and potentially reducing performance.

Innovation Solution

A SOT induction structure with a metal doped with at least one dopant, such as Co, Ru, Pt, CoFeB, or Ta, is used to increase the spin-hall angle and maintain thermal stability, allowing for improved resistance changes and reduced resistivity, thereby simplifying the cell structure and enhancing performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the SOT induction structure is formed with pure metal, then the phase stability is improved, but the spin Hall angle is reduced and resistivity increases

Engineering Contradiction:

Improvephase stabilityVSAvoidspin Hall angle and resistivity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent uses composite material structure by doping tungsten with multiple elements (Co, Ru, Pt, CoFeB, or Ta) to create a doped SOT induction structure. This composite approach maintains the β-W phase stability while enhancing the spin Hall angle and reducing resistivity through the synergistic effects of different dopant elements.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the compositional parameters of the SOT induction structure by introducing controlled amounts of dopant elements (0.1-5 at%). This parameter change transforms the material properties, maintaining phase stability while optimizing electrical and magnetic characteristics for improved device performance.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If multiple interfaces are created in the SOT induction structure, then material properties can be optimized, but thermal stability is reduced

Engineering Contradiction:

Improvematerial propertiesVSAvoidthermal stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent merges the metal layer and dopant layers into a single doped structure through simultaneous sputtering or alternating layer deposition followed by thermal annealing. This merging process minimizes the number of interfaces while maintaining the beneficial material properties, thereby preserving thermal stability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent applies local quality by creating dopant regions within the metal structure through controlled doping. The dopants are locally distributed to optimize specific material properties (spin Hall angle, resistivity) while the overall structure maintains thermal stability through minimized interfaces.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If the SOT induction structure uses conventional materials, then the manufacturing process is simple, but the device performance is limited

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoiddevice performance

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent changes the material parameters by introducing dopant elements into the SOT induction structure using existing sputtering techniques. This approach maintains the simplicity of the manufacturing process while significantly improving device performance through enhanced spin Hall angle and reduced resistivity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials (doped tungsten with multiple element combinations) that can be manufactured using conventional sputtering processes. The composite structure achieves superior device performance without requiring fundamentally new manufacturing methods, thus maintaining ease of manufacture.

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 doped SOT induction structure enhances the spin-hall angle and reduces resistivity, improving the thermal stability and performance of the magnetic memory device while minimizing the need for external magnetic fields, thus simplifying the cell structure and increasing reliability.

Implementation Method 1

the magnetic moment of the free magnetic layer of an MTJ film stack is switched using the spin-orbit interaction effect generated by a current flowing adjacent to the free magnetic layer of the MTJ film stack

Methodology Applied

Scientific EffectSpin-orbit interaction:

Implementation Method 2

The SOT induction structure may be formed by sputtering a metal material and a dopant material simultaneously

Methodology Applied

Scientific EffectSputtering: Sputtering

Data Source

PatentUS20230389440A1Magnetic memory device and manufacturing method thereof

Publication Date: 2023.11.30 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A magnetic memory device includes a substrate, a spin-orbit torque (SOT) induction structure, and a magnetic tunnel junction (MTJ) stack. The SOT induction structure is disposed over the substrate. The SOT induction structure includes a metal and at least one dopant. The MTJ stack is disposed over the SOT induction structure.