MTJ Magnetic Field Angle Sensor with Annealed Synthetic Layers
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Solution Overview
Problem
Current magnetic field angle sensors face challenges in providing a single-chip, cost-effective solution for measuring a magnetic field angle over a 360° range with high accuracy, as existing solutions often require multiple components and are prone to errors.
Innovation Solution
The development of magnetic tunnel junction elements with pinned synthetic multiple layers, annealed under specific conditions to achieve large anisotropies and oriented at multiple angles, forming Wheatstone bridges that generate differential voltage levels proportional to sine and cosine functions of the magnetic field angle, allowing for precise angle measurement using a single chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple Wheatstone bridge sensors and Hall effect sensors are combined to achieve 360° rotational position sensing, then the measurement range is extended to 360°, but the device complexity increases and cost increases
Solution Approach 1:
The patent combines multiple MTJ elements with different magnetic anisotropy orientations (in-plane and perpendicular magnetization) into a single integrated sensor device. This merging approach enables the sensor to measure magnetic field angles across the full 360° range while maintaining a compact single-chip structure, avoiding the need for multiple separate sensors
Solution Approach 2:
The sensor device achieves multi-functionality by incorporating MTJ elements that can respond to magnetic fields from any direction in three-dimensional space. The combination of in-plane and perpendicular magnetization elements allows the single device to perform both linear and angular position sensing across the complete 360° range
2Measurement precision
If multiple Wheatstone bridge sensors are combined to extend measurement range to 360°, then the measurement range is improved, but manufacturing cost increases
Solution Approach 1:
The patent integrates multiple functional MTJ elements onto a single chip substrate, combining what would traditionally require multiple separate sensors into one manufacturable unit. This approach reduces component count, assembly complexity, and overall manufacturing cost while achieving 360° measurement capability
Solution Approach 2:
The patent utilizes different magnetic anisotropy parameters (in-plane vs. perpendicular magnetization) of the MTJ elements to achieve diverse sensing capabilities from a single integrated structure. By controlling the magnetic properties during fabrication, the sensor can measure fields from any direction without requiring multiple physical sensors
3Measurement precision
If AMR elements are used in Wheatstone bridge configuration to measure magnetic field angle, then angle measurement is achieved, but the measurement range is limited to +/-45°
Solution Approach 1:
The patent changes the magnetic anisotropy parameter of the MTJ elements from traditional in-plane magnetization to include perpendicular magnetization components. This parameter change enables the sensing elements to respond to magnetic fields from any direction in 3D space, extending the measurement range beyond the limited +/-45° range of conventional AMR sensors
Solution Approach 2:
The sensor employs a composite magnetic structure combining ferromagnetic layers with different anisotropy characteristics. This composite approach creates MTJ elements that can simultaneously exhibit in-plane and perpendicular magnetization responses, enabling full 360° angular measurement capability
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 enables accurate measurement of magnetic field angles over a 360° range with reduced errors and cost, eliminating the need for multiple components and Hall sensors, while maintaining high production yield and stability.
Implementation Method 1
The MTJ device has a tunneling magneto-resistance response, as a function of applied magnetic field that is substantially symmetric about zero field
Implementation Method 2
The magnetic tunnel junction elements are then annealed for a first time in the presence of a strong magnetic field in a direction of the reference axis. The magnetic tunnel junction elements are annealed at a temperature of from approximately 200°C to approximately 300°C for a period of between 5 minutes and 100 minutes
Implementation Method 3
The magnetic tunnel junction elements are then annealed in the presence of a strong magnetic field in a direction of the reference axis. The very large magnetic field is oriented in the direction (X)
Implementation Method 4
Each magneto-resistive element possesses an ability to change resistance in a COS 2(M) vector and the current flow
Data Source
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AI summary
A magnetic tunnel junction element formed on a substrate responsive to a magnetic field angle perpendicular to a sensing current passing through said magnetic tunnel junction, comprising: - a plurality of magnetic tunnel junction elements formed on a substrate, each magnetic tunnel junction element comprising: - an anti-ferromagnetic material deposited on a bottom electrode formed on said substrate; and - a pinned synthetic multiple layer formed on said antiferromagnetic material; wherein said plurality of magnetic tunnel junction elements are annealed for a first time in the presence of a strong magnetic field in a direction of the reference axis; wherein said plurality of magnetic tunnel junction elements are then patterned such that each magnetic tunnel junction element has a large dimensional aspect ratio and has large anisotropies in each of said pinned synthetic multiple layer of said plurality of magnetic tunnel junction elements; and said plurality of magnetic tunnel junction elements is annealed for a second time with no external magnetic field so that exchange pinning is reduced during said annealing and strong stress induced anisotropies of said pinned synthetic multiple layer align magnetization of said pinned synthetic multiple layer align a long axis of each of said plurality of magnetic tunnel junctions.