SOT-MTJ MRAM Cap Layer Layout for Smaller, Lower-Power Cells

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing magnetoresistive random access memory (MRAM) devices face issues such as high chip area, high cost, high power consumption, limited sensitivity, and susceptibility to temperature variations.

Innovation Solution

A method for fabricating MRAM devices involving the formation of a spin orbit torque (SOT) layer, a magnetic tunneling junction (MTJ), and multiple cap layers with specific surface configurations to enhance device performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If conventional magnetic field sensor technologies (AMR, GMR, MTJ sensors) are used, then sensing function is achieved, but chip area is large and cost is high

Engineering Contradiction:

Improvechip areaVSAvoidsensing function

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

The patent merges the reference layer and free layer into a single magnetic tunneling junction structure, eliminating the need for separate sensor elements. The MTJ device integrates both the reference magnetization layer and free magnetization layer in one compact structure, achieving sensing function while reducing chip area compared to conventional AMR or GMR sensors that require separate component arrangements.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The magnetic tunneling junction serves multiple functions simultaneously: it acts as both the sensing element and the memory storage element. The same MTJ structure that provides magnetoresistive sensing also enables non-volatile data storage through magnetic state retention, eliminating the need for separate sensor and memory components, thus reducing overall chip area and cost.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Use of energy by moving object

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

Engineering Contradiction:

Improvepower consumptionVSAvoidsensing function

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent replaces conventional current-based magnetic field sensing mechanisms with a voltage-based readout mechanism. Instead of requiring large currents to generate magnetic fields for sensing (as in AMR or GMR sensors), the MTJ structure enables sensing through voltage measurement across the tunnel junction, significantly reducing power consumption while maintaining sensing functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The magnetic tunneling junction utilizes its own inherent magnetoresistive effect to provide sensing functionality without requiring external magnetic field generation coils or additional actuation mechanisms. The device senses magnetic fields through its intrinsic resistance changes based on relative magnetization orientations, eliminating the need for separate power-intensive field generation systems.

Inventive Principle:

Principle #25Self-service

3Measurement precision

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

Engineering Contradiction:

ImprovesensitivityVSAvoidtemperature variation sensitivity

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent utilizes the TMR effect which provides significantly higher magnetoresistive ratio (exceeding 100%) compared to conventional AMR or GMR effects. This parameter change in the underlying physical mechanism enables enhanced sensitivity to magnetic field changes. Additionally, the symmetric magnetic tunneling junction structure with pinned and free layers allows for differential measurement approaches that improve temperature stability by compensating for thermal drift effects.

Inventive Principle:

Principle #35Parameter changes

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 method improves insulation capabilities and reduces chip area, cost, and power consumption while maintaining sensitivity, addressing the limitations of existing MRAM technologies.

Implementation Method 1

first forming a spin orbit torque (SOT) layer on a substrate

Methodology Applied

Scientific EffectSpin orbit torque:

Implementation Method 2

the characterization of utilizing GMR materials to generate different resistance under different magnetized states could also be used to fabricate MRAM devices

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS20260032921A1Semiconductor device and method for fabricating the same

Publication Date: 2026.01.29 UNITED MICROELECTRONICS CORP

AI summary

A method for fabricating a magnetoresistive random access memory (MRAM) device includes the steps of first forming a spin orbit torque (SOT) layer on a substrate, forming a magnetic tunneling junction (MTJ) on the SOT layer, forming a first cap layer adjacent to the MTJ, and then forming a second cap layer adjacent to the first cap layer. Preferably, a top surface of the second cap layer is lower than a top surface of the first cap layer.