Metamagnetic Tunnel Junction with Ferroelectric Layer for Low-Power Memory

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Solution Overview

Problem

Magnetoresistive memory devices, such as STT-MRAM, require high switching power to flip the magnetization direction of the free layer, which is inefficient.

Innovation Solution

Incorporating a ferroelectric or multiferroic material layer with a metamagnetic tunnel junction, comprising a metamagnetic material layer, an insulating barrier layer, and a reference magnetization layer, allowing for electrical field-induced switching without generating a tunneling current, thereby reducing the power required to change the resistivity state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If STT-MRAM uses tunneling current to flip magnetization direction, then magnetization switching is achieved, but switching power becomes excessively high

Engineering Contradiction:

Improveswitching powerVSAvoidmagnetization switching reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent introduces a ferroelectric layer as an intermediary between the reference layer and free layer. This ferroelectric layer mediates the magnetization switching process by utilizing electric field-induced polarization switching to control the magnetic state, thereby avoiding the need for high-current tunneling while maintaining reliable switching.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the spin-transfer torque mechanism (which requires high current) with an electric field-based mechanism. By using voltage-controlled ferroelectric polarization switching instead of current-driven spin transfer, the system achieves magnetization switching with significantly reduced power consumption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Use of energy by moving object

If high tunneling current is applied to program memory, then magnetization state changes, but energy consumption increases

Engineering Contradiction:

Improveprogramming energyVSAvoidprogramming efficiency

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent changes the fundamental programming parameter from current magnitude to voltage polarity. Instead of varying current strength to achieve switching, the system uses bipolar voltage pulses applied to the ferroelectric layer, which induces polarization switching and subsequently controls magnetization state with minimal energy dissipation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent exploits the phase transition特性 of ferroelectric materials, where applying an electric field induces a reversible switch between positive and negative polarization states. This phase transition in the ferroelectric layer directly controls the magnetic state of the free layer, enabling energy-efficient programming without requiring high current flow.

Inventive Principle:

Principle #36Phase transitions

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 approach reduces the switching power needed to change the resistivity state of the memory cell, achieving efficient and deterministic programming with high tunneling magnetoresistance ratios, unlike prior art STT MRAMs which require higher energy and non-deterministic programming.

Implementation Method 1

Methodology Applied

Scientific EffectElectrical field-induced switching: Electric Field

Implementation Method 2

A magnetoresistive memory device can store information employing the difference in electrical resistance of a first configuration in which a free magnetization layer has a magnetization direction that is parallel to the magnetization of a reference magnetization layer and a second configuration in which the free magnetization layer has a magnetization direction that is antiparallel to the magnetization of the reference magnetization layer

Methodology Applied

Scientific EffectTunneling magnetoresistance: Magnetoresistance

Data Source

PatentUS11200934B2Tunneling metamagnetic resistance memory device and methods of operating the same

Publication Date: 2021.12.14 SANDISK TECHNOLOGIES LLC

AI summary

A magnetoresistive memory device includes a first electrode, a second electrode, and a layer stack located between the first electrode and the second electrode. The layer stack may include a ferroelectric material layer and a metamagnetic tunnel junction containing a metamagnetic material layer, an insulating barrier layer, and a metallic material layer. Alternatively, the layer stack may include a multiferroic material layer, the metamagnetic material layer, the insulating barrier layer, and a reference magnetization layer.