Dual-Ferromagnetic Memory Cell with Insulating Spacer

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Solution Overview

Problem

Magnetic memory cells face challenges with increased coercivity as they shrink, leading to higher operating currents, reduced thermal stability, and interference from fringe magnetic fields, which affect data integrity and increase power consumption and cost.

Innovation Solution

A multi-layered magnetic memory structure comprising a first ferromagnetic layer, a second ferromagnetic layer separated by a non-magnetic insulating layer, and a reference layer, where the first ferromagnetic layer has higher coercivity than the second, allowing for reduced write currents and improved thermal stability by demagnetizing field coupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If magnetic memory cells are made smaller, then device density and integration are improved, but coercivity increases leading to higher operating currents

Engineering Contradiction:

Improvememory cell areaVSAvoidoperating current

Core Design Contradiction:

Area of moving objectVSUse of energy by moving object

Solution Approach 1:

The data layer is segmented into two separate ferromagnetic layers (first and second ferromagnetic layers) with different coercivities, allowing independent optimization of thermal stability and write current requirements

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the magnetic structure have different coercivity properties - the first ferromagnetic layer has higher coercivity for thermal stability while the second has lower coercivity for easier writing, creating local quality variations that resolve the contradiction

Inventive Principle:

Principle #3Local quality

2Use of energy by moving object

If ferromagnetic layer thickness is reduced, then coercivity decreases enabling lower write currents, but thermal stability deteriorates

Engineering Contradiction:

Improvewrite currentVSAvoidthermal stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The data layer is divided into two ferromagnetic layers with different thicknesses and coercivities, allowing the system to benefit from both low write current (thin layer) and high thermal stability (thick layer) simultaneously

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The composite data layer structure combines ferromagnetic materials with different coercivity characteristics, creating a multi-layered composite that achieves both low coercivity for writing and high thermal stability

Inventive Principle:

Principle #40Composite materials

3Reliability

If reference layer size is increased to reduce fringe fields, then data integrity is improved, but device area increases

Engineering Contradiction:

Improvedata integrityVSAvoiddevice area

Core Design Contradiction:

ReliabilityVSArea of moving object

Solution Approach 1:

The harmful fringe field effect is extracted and isolated to a specific region (between the data layers), allowing the reference layer to be optimized for area while the fringe field management is handled by the dual-layer data structure

Inventive Principle:

Principle #2Taking out (Extraction)

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 solution reduces coercivity and enhances thermal stability, enabling efficient data storage with lower operating currents and reduced risk of data corruption, while maintaining data integrity and lowering power consumption and fabrication complexity.

Implementation Method 1

a second ferromagnetic layer spaced apart from the first ferromagnetic layer by a non-magnetic insulating layer and being magnetically coupled to the first ferromagnetic layer by demagnetizing fields from the first ferromagnetic layer

Methodology Applied

Scientific EffectDemagnetizing fields: Magnetic Field

Implementation Method 2

The write operation is typically accomplished via a write current that sets the orientation of the magnetic moment in the data layer to a predetermined direction

Methodology Applied

Scientific EffectMagnetic moment orientation: Ferromagnetism

Implementation Method 3

The degree of parallelism affects the resistance of the cell, and this resistance can be determined by sensing an output current or voltage produced by the memory cell in response to the read current

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS7457153B1Integrated circuit memory devices having magnetic memory cells therein that utilize dual-ferromagnetic data layers

Publication Date: 2008.11.25 SAMSUNG ELECTRONICS CO LTD

AI summary

An exemplary memory array including a plurality of memory cells, each of the memory cells comprises a first ferromagnetic layer, a second ferromagnetic layer spaced apart from the first ferromagnetic layer by a non-magnetic insulating layer and being magnetically coupled to the first ferromagnetic layer by demagnetizing fields from the first ferromagnetic layer, a spacer layer above the second ferromagnetic layer, and a reference layer above the spacer layer. The first ferromagnetic layer, non-magnetic insulating layer, and second ferromagnetic layer in combination function as a data layer of the memory cell.