MTJ Sensor Stack Fabrication for Compact Low-Power Magnetic Sensing

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Solution Overview

Problem

Current magnetic field sensor technologies, such as AMR, GMR, and MTJ sensors, face challenges including high chip area, high cost, high power consumption, limited sensitivity, and susceptibility to temperature variations.

Innovation Solution

A method for fabricating a semiconductor device, specifically a MRAM device, involving the formation of a magnetic tunneling junction (MTJ) with a pinned layer, a barrier layer, a free layer, and a top electrode layer, along with a spacer and inter-metal dielectric layers, to enhance performance and reduce limitations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

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

Engineering Contradiction:

Improvechip areaVSAvoidsensing function

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The magnetic field sensor is segmented into distinct functional layers including pinned layer, barrier layer, free layer, and cap layer, allowing compact integration while maintaining sensing functionality. The sensor array is divided into multiple sensor elements that can be independently configured

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements a nested structure where the magnetic field sensor is integrated within a semiconductor device substrate, with interconnect layers and isolation structures nested around the sensitive elements. The pinned layer, barrier layer, and free layer are nested in sequential order to form the complete MTJ structure

Inventive Principle:

Principle #7Nested doll (Nesting)

2Ease of manufacture

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

Engineering Contradiction:

Improvemanufacturing costVSAvoidsensing function

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent combines multiple sensor elements and functional layers into a single integrated semiconductor device structure, sharing common substrates, interconnect layers, and fabrication processes. The pinned layer, barrier layer, and free layer are formed using standard semiconductor deposition techniques, reducing manufacturing complexity and cost

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The semiconductor device structure is designed to support multiple sensor elements with different orientations and configurations on the same substrate, allowing a single fabrication process to produce versatile sensor arrays that can detect magnetic fields in multiple directions and applications

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Use of energy by moving object

If conventional magnetic field sensor technologies are used, then magnetic field 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 magnetic sensing mechanisms with magnetoresistive tunneling junctions that detect magnetic fields through resistance changes rather than mechanical or electromagnetic induction methods. This solid-state approach reduces power consumption while maintaining sensing sensitivity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes changes in electrical resistance parameters of the magnetic tunneling junction in response to magnetic field variations. By monitoring resistance changes in the free layer relative to the pinned layer, the sensor achieves low-power operation through passive detection mechanisms

Inventive Principle:

Principle #35Parameter changes

4Measurement precision

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:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent employs composite magnetic layer structures including pinned layer, barrier layer, and free layer with specific magnetic properties. The combination of these layers creates a magnetoresistive tunneling junction with enhanced sensitivity to magnetic field changes while maintaining a manageable device structure

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes vertical layering of magnetic layers to enhance sensitivity, with the pinned layer, barrier layer, and free layer stacked in the vertical dimension. This layered structure increases the effective sensing area and magnetic field interaction without increasing planar device footprint

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

5Temperature

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

Engineering Contradiction:

Improvetemperature stabilityVSAvoidsensing function

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent implements local quality control through isolation structures and interconnect layers that are specifically designed to thermally isolate the sensitive magnetic tunneling junction from temperature variations in the surrounding environment. The barrier layer and cap layer provide localized thermal management for the sensitive regions

Inventive Principle:

Principle #3Local quality

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 proposed solution effectively reduces chip area, cost, and power consumption while improving sensitivity and robustness against temperature variations, thereby addressing the shortcomings of existing magnetic field sensor technologies.

Implementation Method 1

Magnetoresistance (MR) effect has been known as a kind of effect caused by altering the resistance of a material through variation of outside magnetic field. 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.

Methodology Applied

Scientific EffectMagnetoresistance effect: Magnetoresistance

Data Source

PatentUS12310258B2Semiconductor device and method for fabricating the same

Publication Date: 2025.05.20 UNITED MICROELECTRONICS CORP

AI summary

A method for fabricating semiconductor device includes the steps of: forming a first inter-metal dielectric (IMD) layer on a substrate; forming a metal interconnection in the first IMD layer; forming a bottom electrode layer and a pinned layer on the first IMD layer; forming a sacrificial layer on the pinned layer; patterning the sacrificial layer, the pinned layer, and the bottom electrode layer to form a first magnetic tunneling junction (MTJ); forming a second IMD layer around the first MTJ; removing the sacrificial layer to form a recess; forming a barrier layer and a free layer in the recess; forming a top electrode layer on the free layer; and patterning the top electrode layer and the free layer to form a second MTJ.