Spin-Orbit Torque Memory Structure for Reconfigurable PUF Security

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Solution Overview

Problem

Existing physically unclonable function (PUF) technologies for securing vehicle security in autonomous driving systems lack reconfigurability, limiting their effectiveness against environmental variations and external attacks.

Innovation Solution

A magnetic memory device utilizing a spin-orbit torque (SOT) with a triple-layered structure, comprising a lower ferromagnetic layer with horizontal anisotropy, a non-magnetic layer, and an upper ferromagnetic layer with perpendicular anisotropy, where the magnetization orientation of the lower ferromagnetic layer is randomly distributed, enabling reconfigurable switching through demagnetization processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional PUF methods (via-hole etching, spin transfer torque MTJ, perpendicular magnetic anisotropy) are used, then environmental stability and uniqueness are improved, but reconfigurability deteriorates

Engineering Contradiction:

Improveenvironmental stabilityVSAvoidreconfigurability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by making the magnetization orientation of the lower ferromagnetic layer changeable through external magnetic fields. The system transitions from a static, fixed PUF configuration to a dynamic one where the random magnetization distribution can be reconfigured by applying different magnetic field orientations during writing operations, enabling multiple configuration states while maintaining environmental stability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the magnetic anisotropy parameter of the lower ferromagnetic layer from fixed to variable by applying external magnetic fields. By changing the orientation and strength of applied magnetic fields during the writing process, the system can reconfigure the random magnetization distribution, transforming the PUF key without altering the physical structure or environmental conditions

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If spin-orbit torque device with random magnetization distribution is implemented, then reconfigurability is improved, but device complexity increases

Engineering Contradiction:

ImprovereconfigurabilityVSAvoidstructure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the magnetic memory device into distinct functional layers: upper ferromagnetic layer for data storage, nonmagnetic layer for separation, and lower ferromagnetic layer for generating random magnetization distribution. This segmentation allows each layer to perform its specific function independently, simplifying the overall device design while enabling reconfigurability through the lower layer's controllable random magnetization

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The nonmagnetic layer serves as an intermediary between the upper and lower ferromagnetic layers, providing magnetic isolation while allowing spin current transmission. This intermediary structure enables the lower layer to generate random magnetization that influences the upper layer without requiring direct magnetic coupling, reducing the complexity of achieving reconfigurability

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If multiple separate processes and circuits are added to convert Hall signal to digital output, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvesignal conversion accuracyVSAvoidprocess and circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the PUF key generation, storage, and reading functions into a single integrated magnetic memory device structure. The TMR effect provides both the storage mechanism and the reading mechanism, eliminating the need for separate conversion circuits and processes, thereby maintaining measurement precision while reducing overall device complexity

Inventive Principle:

Principle #5Merging (Combining)

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 SOT device provides secure, reconfigurable, and environmentally stable PUF characteristics, resistant to external factors, suitable for hardware-based security applications in autonomous driving systems.

Implementation Method 1

a magnetization orientation of the lower ferromagnetic layer is randomly distributed

Methodology Applied

Scientific EffectRandom magnetization distribution: Magnetism

Implementation Method 2

Spin-orbit torque device and manufacturing method thereof

Methodology Applied

Scientific EffectSpin-orbit torque:

Data Source

PatentUS12439828B2Spin-orbit torque device and manufacturing method thereof

Publication Date: 2025.10.07 HYUNDAI MOTOR CO LTD

AI summary

Disclosed herein is a spin-orbit torque device including a lower ferromagnetic layer, a non-magnetic layer bonded to the lower ferromagnetic layer, and an upper ferromagnetic layer bonded to the non-magnetic layer, wherein a magnetization orientation of the lower ferromagnetic layer is randomly distributed. According to the present disclosure, it is possible to provide a magnetic memory device which cannot be physically duplicated and has reconfigurability using a spin-orbit torque.