AMR Angle Sensor Shape Anisotropy Compensation
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Solution Overview
Problem
Anisotropic magneto-resistive (AMR) angle sensors face reduced accuracy due to shape anisotropy in the disposition of serpentine resistors, which affects the angular displacement measurement.
Innovation Solution
The solution involves reducing shape anisotropy by narrowing the etched isolation between resistors and adding an outer perimeter of electrically isolated anisotropic magneto-resistive material surrounding the Wheatstone bridges, which helps in minimizing the width of the etched isolation and disposing additional anisotropic magneto-resistive material between the resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If serpentine resistors are disposed in Wheatstone bridges for AMR angle sensing, then the sensor can measure angular position, but shape anisotropy in the resistor disposition reduces measurement accuracy
Solution Approach 1:
The patent applies asymmetry by intentionally introducing an outer perimeter of anisotropic magneto-resistive material that is electrically isolated from the serpentine resistors. This asymmetric addition compensates for the shape anisotropy caused by the conventional Wheatstone bridge configuration, thereby improving angular position measurement accuracy to about ±0.1 degree
2Measurement precision
If additional anisotropic magneto-resistive material is added to reduce shape anisotropy, then measurement accuracy improves, but device area increases
Solution Approach 1:
The patent utilizes the planar dimension by disposing the outer perimeter of anisotropic magneto-resistive material in substantially the same plane as the serpentine resistors. This approach adds the necessary material for shape anisotropy compensation without requiring vertical stacking or three-dimensional expansion, thereby minimizing the increase in device area while improving measurement accuracy
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 enhances the accuracy of angular displacement measurement by reducing shape anisotropy, allowing for more precise determination of angular position to about ±0.1 degree.
Implementation Method 1
Anisotropic magneto-resistive material changes the value of its electrical resistance in response to a change in an externally applied magnetic field, for example in response to a change in direction of the externally applied magnetic field
Data Source
AI summary
Some embodiments are directed to an anisotropic magneto-resistive (AMR) angle sensor. The sensor comprises a first Wheatstone bridge comprising a first serpentine resistor, a second serpentine resistor, a third serpentine resistor, and a fourth serpentine resistor. The sensor also comprises a second Wheatstone bridge comprising a fifth serpentine resistor, a sixth serpentine resistor, a seventh serpentine resistor, and an eighth serpentine resistor. The serpentine resistors comprise anisotropic magneto-resistive material that changes resistance in response to a change in an applied magnetic field. The sensor also includes a surrounding of anisotropic magneto-resistive material disposed in substantially a same plane as the serpentine resistors, enclosing the serpentine resistors, and electrically isolated from the serpentine resistors. The first Wheatstone bridge, the second Wheatstone bridge, and the surrounding of anisotropic magneto-resistive material are part of a sensor die.