Magnetic Memory Device Reference Layer Stabilization

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Solution Overview

Problem

In magnetic memory devices, the refinement of magnetoresistive elements leads to an increased probability of magnetization direction reversal in the reference layer due to spin torque, making normal operation difficult, as the magnetization direction of the reference layer is not sufficiently stable.

Innovation Solution

A magnetic memory device configuration with a storage layer having a variable magnetization direction and a reference layer with a fixed magnetization direction, where the storage layer includes sub-magnetic layers with antiparallel magnetization and reduced saturation magnetization, and an intermediate layer to stabilize the antiferromagnetic coupling, reducing the stray magnetic field and preventing magnetization reversal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the magnetoresistive element is refined to improve integration density, then productivity increases, but the stability of the reference layer deteriorates due to increased spin torque effects causing magnetization reversal

Engineering Contradiction:

Improveintegration densityVSAvoidreference layer stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The storage layer is divided into multiple sub-magnetic layers (first sub-magnetic layer, second sub-magnetic layer, third sub-magnetic layer) with alternating magnetization directions. This segmentation allows the stray magnetic fields from individual layers to cancel each other out, reducing the overall spin torque effect on the reference layer while maintaining the element's functionality for high-density integration

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the magnetization parameters of the storage layer by creating alternating up/down magnetization directions in adjacent sub-layers. This parameter modification reduces the net stray magnetic field and spin torque applied to the reference layer, thereby improving reference layer stability even as device dimensions are scaled down for higher integration density

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If a current is passed through the magnetoresistive element to reverse the storage layer magnetization, then the storage layer magnetization direction changes, but the reference layer magnetization direction may reverse due to spin torque reaction

Engineering Contradiction:

Improvemagnetization reversal capabilityVSAvoidreference layer stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The invention converts the harmful spin torque reaction that causes reference layer magnetization reversal into a beneficial effect by using alternating magnetization directions in the storage layer sub-layers. The opposing magnetic fields from adjacent sub-layers cancel each other's spin torque effects on the reference layer, allowing magnetization reversal operation while protecting reference layer stability

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 stabilizes the reference layer, preventing its magnetization reversal and ensuring stable operation of the magnetoresistive element even as the device is refined, by reducing the stray magnetic field and maintaining a sufficiently large Hoff value.

Implementation Method 1

an STT (spin transfer torque) type magnetoresistive element using a spin transfer torque effect (spin transfer torque magnetization reversal) has been proposed. In the STT type magnetoresistive element, the magnetization direction of the storage layer is reversed by passing a current perpendicular to the film surface of each layer constituting the magnetoresistive element

Methodology Applied

Scientific EffectSpin transfer torque effect:

Implementation Method 2

A magnetic memory device (semiconductor integrated circuit device) in which a magnetoresistive element and a transistor are integrated on a semiconductor substrate has been proposed

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS11322189B2Magnetic memory device

Publication Date: 2022.05.03 KIOXIA CORP

AI summary

According to one embodiment, a magnetic memory device includes a first magnetic layer having a variable magnetization direction, a second magnetic layer having a fixed magnetization direction, and a nonmagnetic layer between the first magnetic layer and the second magnetic layer, wherein the first magnetic layer includes a first sub-magnetic layer, a second sub-magnetic layer, and a first intermediate layer between the first sub-magnetic layer and the second sub-magnetic layer, and the first sub-magnetic layer is provided between the nonmagnetic layer and the second sub-magnetic layer and has a magnetization direction antiparallel to a magnetization direction of the second sub-magnetic layer and has a magnetization amount smaller than that of the second sub-magnetic layer.