Non-volatile Associative Memory Cell Segmentation for Lifespan

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Solution Overview

Problem

In spin transfer torque-type magnetoresistance effect elements, the frequent change in resistance values leads to a shortened lifespan due to the necessity of a spin-polarized current flowing in the stacking direction of ferromagnetic layers, which can degrade the associative memory device's performance.

Innovation Solution

A non-volatile associative memory cell design incorporating a magnetoresistance effect element with a first ferromagnetic layer for magnetization change and a second ferromagnetic layer with fixed magnetization, utilizing match lines with specific voltages to control the magnetoresistance effect element's resistance value changes without continuous current flow through the second member.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a spin-polarized current flows in the stacking direction of ferromagnetic layers to change resistance values, then the magnetoresistance effect element can store and rewrite data, but the lifespan of the magnetoresistance effect element is shortened

Engineering Contradiction:

Improvedata rewriting capabilityVSAvoidlifespan of magnetoresistance effect element

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The magnetoresistance effect element is divided into two separate members: a first member containing the first ferromagnetic layer with switchable magnetization direction, and a second member containing the second ferromagnetic layer with fixed magnetization direction. This segmentation allows the first member to handle all magnetization switching operations while the second member remains static, thereby resolving the contradiction by isolating the wear-inducing current flow to only the first member.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of having both ferromagnetic layers stacked together with current flowing through both, the patent inverts the conventional structure by separating them into two members connected in series. The current flows only through the first member to switch its magnetization, while the second member's magnetization remains fixed, thus protecting it from degradation.

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If the magnetoresistance effect element is used in an associative memory device, then data storage and retrieval functions are achieved, but frequent resistance value changes degrade device performance

Engineering Contradiction:

Improvedata storage functionVSAvoiddevice performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

By segmenting the magnetoresistance effect element into two functional members with distinct roles, the patent enables reliable data storage while minimizing degradation. The first member handles all dynamic operations (magnetization switching for data writing), while the second member provides a stable reference, thus maintaining device performance despite frequent operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first member acts as an intermediary that absorbs all the stress of magnetization switching. By placing the second ferromagnetic layer in a separate second member with fixed magnetization, it serves as a stable mediator that does not participate in switching operations, thereby preventing performance degradation while maintaining data storage functionality.

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 design inhibits the shortening of the magnetoresistance effect element's lifespan by minimizing the need for continuous current flow, thereby enhancing the longevity and performance of the associative memory device.

Implementation Method 1

the magnetoresistance effect element has a resistance value that changes in accordance with a giant magnetoresistance effect, a tunnel magnetoresistance effect, or the like as a magnetoresistive resistance effect

Methodology Applied

Scientific EffectMagnetoresistance effect: Magnetoresistance

Implementation Method 2

a non-volatile associative memory device including a spin transfer torque (STT) type magnetoresistance effect element using a spin transfer torque

Methodology Applied

Scientific EffectSpin transfer torque:

Data Source

PatentUS12009019B2Non-volatile associative memory cell, non-volatile associative memory device, monitoring method, and non-volatile memory cell

Publication Date: 2024.06.11 TDK CORP

AI summary

A non-volatile associative memory cell includes: one magnetoresistance effect element including first and second ferromagnetic layers and a non-magnetic layer; first and second match lines connected to the magnetoresistance effect element in accordance with predetermined first and second search line voltages. The magnetoresistance effect element includes: first and second members. The first member includes first and second electrodes disposed at opposite ends. The first ferromagnetic layer is in the first or second member, the non-magnetic layer is stacked in the first direction, and the direction of internal magnetization of the first ferromagnetic layer changes in a case in which a current flows between the first and second electrodes. The non-magnetic and the second ferromagnetic layers are in the second member. A magnetoresistance effect element resistance value changes. An electric potential corresponding to an second ferromagnetic layer electric potential is applied to each of the first and second match lines.