SOT MRAM MTJ Structure for Compact Magnetic Field Sensing

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Solution Overview

Problem

Current magnetic field sensor technologies, such as AMR and GMR sensors, face issues with high chip area, high cost, high power consumption, limited sensitivity, and susceptibility to temperature variations, necessitating an improved device design.

Innovation Solution

A semiconductor device is fabricated using a spin orbit torque (SOT) MRAM structure with a magnetic tunneling junction (MTJ) stack, featuring a first and second channel layer with different etching rates and a curved sidewall, and utilizing a spin orbit torque effect for magnetic moment switching, employing damascene processes for metal interconnections and dielectric layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional magnetic field sensor technologies (AMR, GMR) are used, then magnetic field sensing function is achieved, but chip area is large, cost is high, power consumption is high, sensitivity is limited, and temperature stability is poor

Engineering Contradiction:

Improvetemperature stabilityVSAvoidchip area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The device is segmented into distinct functional regions: a first region containing the MTJ stack for magnetic field sensing, and a second region containing the channel layer for current conduction. This spatial segmentation allows the sensing function and conduction function to be separated, enabling compact integration while maintaining performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The MTJ stack is positioned on top of the channel layer, with the channel layer serving as both the conduction path and the bottom electrode for the MTJ. This nested configuration eliminates the need for separate bottom electrode structures, reducing chip area while maintaining functionality

Inventive Principle:

Principle #7Nested doll (Nesting)

2Reliability

If conventional magnetic field sensor technologies are used, then magnetic field sensing function is achieved, but power consumption is high

Engineering Contradiction:

Improvesensing performanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The invention replaces conventional magnetic field sensing mechanisms (which require complex magnetic circuit structures) with a spin-orbit torque based MTJ structure. The spin current generated through the spin Hall effect in the channel layer directly switches the magnetic state of the MTJ, eliminating the need for large current loops and reducing power consumption significantly

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If conventional magnetic field sensor technologies are used, then magnetic field sensing function is achieved, but sensitivity is limited

Engineering Contradiction:

ImprovesensitivityVSAvoiddevice structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention utilizes parameter changes in the spin Hall angle of the channel layer material to control the efficiency of spin current generation. By selecting materials with optimized spin Hall angles, the sensitivity of the magnetic field sensing is enhanced while maintaining a relatively simple device structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The channel layer is formed as a composite structure with specific material composition designed to exhibit high spin Hall angle. This composite material approach enables enhanced spin current generation efficiency, thereby improving sensing sensitivity without requiring complex device architectures

Inventive Principle:

Principle #40Composite materials

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 MRAM device enhances device endurance, read stability, and write speed by isolating read/write paths and preventing side effects like coercivity reduction and heating, while improving switching efficiency through spin current application.

Implementation Method 1

The physical definition of such effect is defined as a variation in resistance obtained by dividing a difference in resistance under no magnetic interference by the original resistance. Currently, MR effect has been successfully utilized in production of hard disks thereby having important commercial values.

Methodology Applied

Scientific EffectMagnetic tunneling effect: Magnetoresistance

Implementation Method 2

utilizing a spin orbit torque effect for magnetic moment switching

Methodology Applied

Scientific EffectSpin orbit torque effect:

Data Source

PatentUS20250366375A1Semiconductor device and method for fabricating the same

Publication Date: 2025.11.27 UNITED MICROELECTRONICS CORP

AI summary

A method for fabricating a semiconductor device includes the steps of: forming a first inter-metal dielectric (IMD) layer on a substrate; forming a first metal interconnection and a second metal interconnection in the first IMD layer; forming a channel layer on the first metal interconnection and the second metal interconnection; forming a magnetic tunneling junction (MTJ) stack on the channel layer; and removing the MTJ stack to form a MTJ.