Amorphous Alloy Mediator for Magnetoresistive Stack Growth

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Solution Overview

Problem

Existing magnetoresistive stack structures face challenges in maintaining reliable and thermally stable columnar growth, leading to inefficiencies in magnetic tunnel junctions and magnetoresistive memory devices due to columnar growth of seed regions on conductive materials.

Innovation Solution

Incorporating an amorphous alloy region, such as an iron boron alloy with a boron concentration greater than 40%, between the seed region and electrically conductive materials to suppress columnar growth, improve magnetic properties, and enhance thermal endurance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a seed region is grown directly on electrically conductive material, then the magnetoresistive stack can be manufactured with simpler structure, but columnar growth occurs leading to reduced reliability and thermal stability

Engineering Contradiction:

Improvethermal stabilityVSAvoidstack structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

An amorphous alloy region is introduced as an intermediary layer between the electrically conductive material and the seed region. This intermediate layer suppresses columnar growth of the seed region while maintaining electrical conductivity, thereby improving thermal stability and reliability without requiring fundamental changes to the stack structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The amorphous alloy region changes the physical and chemical parameters at the interface between the conductive material and seed region. By controlling the composition (e.g., boron concentration ≥40%) and structural state (amorphous vs. crystalline) of this region, columnar growth is suppressed while maintaining desired electrical and thermal properties.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional seed regions are used on conductive materials, then manufacturing process is simpler, but columnar growth reduces magnetoresistance properties

Engineering Contradiction:

ImprovemagnetoresistanceVSAvoiddeposition process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The amorphous alloy region serves as a mediator that improves magnetoresistance properties by preventing columnar growth. This intermediate layer can be deposited using standard sputtering or evaporation techniques, maintaining ease of manufacture while significantly improving the magnetic tunnel junction performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention uses a composite structure combining the amorphous alloy region with conventional seed region materials (nickel, chromium, cobalt, iron). This composite approach leverages the benefits of amorphous materials (suppressed columnar growth) with well-established seed region compositions, improving magnetoresistance without requiring entirely new material systems.

Inventive Principle:

Principle #40Composite materials

3Reliability

If seed region thickness is increased to improve coverage, then better electrical contact is achieved, but columnar growth becomes more pronounced reducing thermal endurance

Engineering Contradiction:

Improvethermal enduranceVSAvoidseed region thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The amorphous alloy region acts as a mediator that allows for thinner seed regions while maintaining good electrical contact. By suppressing columnar growth, it enables reduced seed region thickness without compromising thermal endurance, actually improving it compared to conventional thicker seed regions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Changing the structural parameter from crystalline to amorphous state in the alloy region fundamentally alters the growth morphology. This parameter change allows for optimized seed region thickness that improves thermal endurance while maintaining adequate electrical contact through the amorphous region's inherent properties.

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 amorphous alloy region facilitates the growth of a nickel-chrome seed region with reduced columnar characteristics, resulting in improved reliability, thermal stability, and magnetoresistance properties, thereby enhancing the performance and longevity of magnetoresistive memory stacks.

Implementation Method 1

the amorphous alloy region is formed or deposited, via ion-beam deposition, sputtering and/or evaporation techniques, on an electrically conductive metal material

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

the magnetic region disposed on or in physical contact with the seed region maintains or includes improved properties (for example, magnetoresistance (MR) and resistance-area product (RA) of the stack/structure)

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS10622552B2Magnetoresistive stacks and methods therefor

Publication Date: 2020.04.14 EVERSPIN TECHNOLOGIES INC

AI summary

A magnetoresistive stack includes a seed region formed above a base region, a fixed magnetic region formed above the seed region and an intermediate region positioned between the fixed magnetic region and a free magnetic region. The base region may be formed of a material having a lower standard free energy of oxidation than iron.