Magnetic Sensor Bridge Using Dual Free Layer for Resistance Differentiation
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Solution Overview
Problem
Conventional GMR or TMR based Wheatstone bridge sensors face challenges in achieving different resistances for resistors, which is costly and time-consuming due to the need for specialized annealing and different sensor stacks, increasing production complexity and time.
Innovation Solution
The use of a dual free layer (DFL) structure with different magnetic structures adjacent to the DFL sensors, such as permanent magnets, antiferromagnetic layers, and synthetic antiferromagnetic structures, allows for the differentiation of resistors without the need for complex annealing processes, simplifying production and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If different sensor stacks and specialized annealing are used to obtain different pinning directions for resistors, then the Wheatstone bridge can achieve different resistance values, but production time increases and manufacturing complexity increases
Solution Approach 1:
The patent changes the magnetic configuration parameter by using different magnetic structures (permanent magnet vs. antiferromagnetic layer) adjacent to the DFL sensors instead of changing the sensor stacks themselves. This allows achieving different pinning directions and resistance values while maintaining the same sensor stack design, thereby reducing production time and manufacturing complexity
Solution Approach 2:
The patent uses identical or substantially similar DFL sensor stacks for all resistors in the Wheatstone bridge, copying the same sensor design. The differentiation is achieved through adjacent magnetic structures rather than modifying each sensor stack individually, which simplifies fabrication and reduces production time
2Manufacturing precision
If different sensor stacks and specialized annealing are used to obtain different pinning directions for resistors, then the Wheatstone bridge can achieve different resistance values, but device complexity increases
Solution Approach 1:
The patent changes the magnetic structure parameter adjacent to the sensors rather than changing the sensor stacks themselves. By using different magnetic configurations (permanent magnet vs. antiferromagnetic layer), the patent achieves different resistance values while maintaining uniform sensor stacks, thereby reducing device complexity
Solution Approach 2:
The patent makes the DFL sensor stack universal by using the same design for all resistors in the Wheatstone bridge. The differentiation function is transferred to the adjacent magnetic structures, allowing a single sensor stack design to serve multiple purposes and reducing overall device complexity
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 decreases production time and costs by simplifying the fabrication process while maintaining the accuracy of the Wheatstone bridge measurements, enabling efficient production of magnetic field sensors with reduced complexity.
Implementation Method 1
The TMR sensor has very high sensitivity compared to other magnetic sensors
Implementation Method 2
a first antiferromagnetic (AFM) layer; and a synthetic antiferromagnetic (SAF) structure disposed over the first AFM layer
Data Source
AI summary
The present disclosure generally relates to sensor device, such as a magnetic sensor bridge, that utilizes a dual free layer (DFL) structure. The device includes a plurality of resistors that each includes the same DFL structure. Adjacent the DFL structure is a magnetic structure that can include a permanent magnet, an antiferromagnetic (AFM) layer having a synthetic AFM (SAF) structure thereon, a permanent magnetic having a SAF structure thereon, or an AFM layer having a ferromagnetic layer thereon. The DFL structures are aligned with different layers of the magnetic structures to differentiate the resistors. The different alignment and/or different magnetic structures result in a decrease in production time due to reduced complexity and, thus, reduces costs.