Perpendicular MR pSAF Structure Using Krypton Deposition for Z-Axis Stability

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Solution Overview

Problem

Existing magnetic field sensors, particularly those with z-axis sensing capabilities, face limitations in field stability and range due to insufficient perpendicular magnetic anisotropy and RKKY coupling strength, which affect their performance and usability.

Innovation Solution

Depositing layers of the reference and hard layers in a Krypton atmosphere to enhance perpendicular magnetic anisotropy (PMA) and RKKY coupling strength, resulting in a stiffer pSAF structure that increases the maximum stability field and usable range of z-axis magnetic sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional deposition methods are used for reference and hard layers, then manufacturing process is simpler, but perpendicular magnetic anisotropy and RKKY coupling strength are insufficient

Engineering Contradiction:

Improveperpendicular magnetic anisotropy and RKKY coupling strengthVSAvoiddeposition process complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent changes the deposition atmosphere parameter from conventional Argon to Krypton gas. This parameter change results in enhanced perpendicular magnetic anisotropy (PMA) and stronger RKKY coupling in the pSAF structure, thereby increasing the maximum stability field and improving sensor performance without adding significant process complexity

Inventive Principle:

Principle #35Parameter changes

2Reliability

If pSAF structure is stiffened by Kr deposition, then field stability range increases, but deposition process becomes more complex

Engineering Contradiction:

Improvefield stability rangeVSAvoiddeposition process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs Krypton, an inert noble gas, as the deposition atmosphere. This inert environment enables the formation of a stiffer pSAF structure with improved perpendicular magnetic anisotropy and RKKY coupling, expanding the field stability range up to 250 mT while maintaining process feasibility through standard sputtering techniques

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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 enhanced PMA and RKKY coupling strength improve the field stability and range of z-axis sensors, providing improved performance and thermal stability, with increased Hc1, Hc2, and Hcpl values, and a broader AFmin range.

Implementation Method 1

layers in the reference layer and/or hard layer are deposited in a Krypton atmosphere

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

forming a hard layer having a fixed reference magnetization layer opposite to that of the reference layer due to a metallic layer in between the hard layer and the reference layer

Methodology Applied

Scientific EffectRKKY coupling:

Data Source

PatentUS20250372300A1Perpendicular MR SAF

Publication Date: 2025.12.04 ALLEGRO MICROSYSTEMS LLC

AI summary

Method for forming a magnetoresistive element by forming a sense layer having a free sense magnetization, a reference layer having a fixed reference magnetization, wherein the reference layer is formed by deposition in a Krypton atmosphere, a tunnel barrier layer between the reference layer and the sense layer, and a hard layer having a fixed reference magnetization layer opposite to that of the reference layer. The magnetoresistive element may be configured to measure an external magnetic field oriented substantially perpendicular to the plane of the reference layer. The reference magnetizations of the reference and hard layers may be oriented substantially perpendicularly to the plane of the reference and hard layers. The sense magnetization may have a vortex configuration in the absence of an external magnetic field.