Magnetoresistive Sensor Stress Layer for Reference Magnetization Alignment
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Solution Overview
Problem
Magnetoresistive sensors, particularly TMR sensors, experience increased sensing errors and reduced sensitivity due to mechanical stress during fabrication or integration, leading to a weaker reference layer system and faster degradation.
Innovation Solution
A stress inducing layer is coupled to the layer stack of the magnetoresistive sensor to apply mechanical stress along a specific axis, aligning the magnetization axis of the reference layer system in a desired direction, thereby stabilizing the reference layer system and enhancing the TMR effect and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical stress is applied during fabrication or integration, then the sensor can be manufactured and integrated, but the reference layer system becomes weaker and more unstable, leading to increased sensing errors and reduced sensitivity
Solution Approach 1:
A stress inducing layer is added to the sensor structure that applies a counteracting mechanical stress to compensate for the stress generated during fabrication and integration. This preliminary anti-action prevents the reference layer system from becoming unstable, maintaining magnetization alignment and sensor performance throughout the manufacturing and integration process.
2Device complexity
If the magnetization axis of the reference layer system is not properly aligned, then the sensor structure can be simpler, but sensing errors increase and sensitivity decreases
Solution Approach 1:
The stress inducing layer changes the mechanical stress parameter in the sensor structure to achieve proper alignment of the magnetization axis in the reference layer system. By controlling the stress state, the patent ensures that the magnetization axis aligns with the desired sensing direction, improving measurement precision without significantly increasing device complexity.
3Productivity
If the reference layer system is unstable, then the sensor can be manufactured faster, but the TMR effect is reduced and sensitivity decreases
Solution Approach 1:
The stress inducing layer is incorporated into the sensor structure during manufacturing to preliminarily establish stable magnetization alignment in the reference layer system. This preliminary action ensures that the TMR effect is maximized and sensitivity is enhanced from the outset, allowing for faster manufacturing without compromising performance.
Solution Approach 2:
The patent uses a composite structure combining the reference layer system with a stress inducing layer made of appropriate material. This composite structure provides both mechanical stability and magnetic properties needed to maintain strong TMR effect and high sensitivity throughout the sensor's operational life.
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
This approach increases the TMR effect by up to 20%, reduces sensing errors, and extends the lifetime of the sensing element by maintaining a more stable reference layer system, resulting in higher signal amplitudes and improved angular sensor performance.
Implementation Method 1
the stress inducing layer is configured to apply a force to the layer stack to induce a mechanical stress in the layer stack along a mechanical stress axis such that the magnetization axis is aligned parallel with the mechanical stress axis or perpendicular with the mechanical stress axis
Implementation Method 2
a GMR effect is a quantum mechanical magnetoresistance effect that is observed in thin-film structures comprising of alternating ferromagnetic and non-magnetic conductive layers
Implementation Method 3
A TMR effect occurs in a magnetic tunnel junction (MTJ), wherein the magnetic tunnel junction occurs at a thin insulator that separates two ferromagnets from one another
Implementation Method 4
An AMR effect is a property of a material in which a dependence of the electrical resistance on an angle between a direction of an electric current (e.g., a sensing axis) and a magnetization direction is observed
Data Source
AI summary
A magnetoresistive sensor includes a sensing element and a stress inducing layer. The sensing element has a layer stack that includes a reference layer having a fixed reference magnetization aligned with a magnetization axis; a magnetic free layer having a magnetically free magnetization, wherein the magnetically free magnetization is variable in a presence of an external magnetic field; and a non-magnetic layer arranged between the reference layer and the magnetic free layer. The stress inducing layer is coupled to the layer stack and is configured to apply a force to the layer stack to induce a mechanical stress in the layer stack along a mechanical stress axis such that the magnetization axis is aligned parallel with the mechanical stress axis or perpendicular with the mechanical stress axis.