Nonvolatile Memory Cell With Heating Layer for Magnetization Control

Solution Overview

Problem

Conventional spin transfer torque based magnetic random access memory (STT-MRAM) experiences reduced drive current during information writing due to asymmetry in the selection transistor, leading to increased cell area and power consumption, as the drive capacity changes based on the direction of current flow.

Innovation Solution

A nonvolatile memory cell configuration with a layered structure including a storage layer and a magnetization fixed layer, where a heating layer controls the magnetization direction of the magnetization fixed layer, allowing information to be written by heating the magnetization fixed layer without bidirectional current flow in the selection transistor, utilizing the magnetic field for magnetization reversal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bidirectional current flow is used in the selection transistor for information writing, then magnetization reversal can be achieved, but drive current is reduced and cell area increases

Engineering Contradiction:

Improvemagnetization reversalVSAvoiddrive current

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent inverts the conventional approach by using a heating layer to thermally assist magnetization reversal instead of relying solely on spin transfer torque from bidirectional current flow. The heating layer is positioned adjacent to the magnetic tunnel junction and provides thermal energy to facilitate magnetization switching, allowing unidirectional or reduced-magnitude current flow through the selection transistor while achieving reliable write operations.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the physical state parameters of the magnetic layers by introducing controlled heating. The heating layer raises the temperature of the magnetization fixed layer and storage layer temporarily during write operations, reducing the coercive force and enabling magnetization reversal at lower current densities. This parameter change (temperature) directly addresses the drive current reduction problem.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If bidirectional current flow is used in the selection transistor for information writing, then magnetization reversal can be achieved, but cell area increases

Engineering Contradiction:

Improvemagnetization reversalVSAvoidcell area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent inverts the conventional approach by using a heating layer to thermally assist magnetization reversal instead of relying solely on spin transfer torque from bidirectional current flow. The heating layer is positioned adjacent to the magnetic tunnel junction and provides thermal energy to facilitate magnetization switching, allowing unidirectional or reduced-magnitude current flow through the selection transistor while achieving reliable write operations.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the physical state parameters of the magnetic layers by introducing controlled heating. The heating layer raises the temperature of the magnetization fixed layer and storage layer temporarily during write operations, reducing the coercive force and enabling magnetization reversal at lower current densities. This parameter change (temperature) directly addresses the drive current reduction problem.

Inventive Principle:

Principle #35Parameter changes

3Power

If the selection transistor is upsized to maintain drive capacity, then drive current is maintained, but device complexity increases

Engineering Contradiction:

Improvedrive capacityVSAvoidtransistor size

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent introduces a heating layer as an intermediary component between the current source and the magnetic tunnel junction. This heating layer acts as a mediator that converts electrical energy into thermal energy, which then assists the magnetization reversal process. By using this intermediary thermal assistance, the selection transistor does not need to be oversized to provide sufficient drive current, as the heating layer supplements the energy required for magnetization switching.

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 approach enables efficient information writing with reduced power consumption and minimized cell area by using the magnetic field for magnetization reversal, avoiding the need for upsizing the selection transistor and maintaining high drive capacity.

Implementation Method 1

a heating layer that heats the magnetization fixed layer to control a magnetization direction of the magnetization fixed layer

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

utilizing the magnetic field for magnetization reversal

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Data Source

PatentUS10706903B2Nonvolatile memory cell, memory cell unit, and information writing method, and electronic apparatus

Publication Date: 2020.07.07 SONY GROUP CORP

AI summary

A nonvolatile memory cell includes a layered structure body formed by layering a storage layer that stores information in accordance with a magnetization direction and a magnetization fixed layer that defines a magnetization direction of the storage layer; and a heating layer that heats the magnetization fixed layer to control a magnetization direction of the magnetization fixed layer.