MTJ Triaxial Magnetic Sensor Orthogonal Integration
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Solution Overview
Problem
Current triaxial magnetic field sensors, such as those using GMR technology, face challenges with excessive size, high packaging cost, lower sensitivity, and higher power consumption due to the need for multiple sensor chips on different substrates, making them impractical for compact and efficient geomagnetic field measurements.
Innovation Solution
A compact triaxial Magnetic Tunnel Junction (MTJ) sensor design is implemented, where X-axis, Y-axis, and Z-axis sensors are orthogonally integrated onto a single ASIC chip with acutely or obtusely angled MTJ magnetic sensor chips, connected using gold wire bonds or solder bumps, enhancing sensitivity and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensor chips are integrated in the package to provide vector measurement capability, then measurement precision is improved, but device complexity and packaging cost increase
Solution Approach 1:
The patent combines multiple sensor chips (X-axis, Y-axis, and Z-axis sensors) onto a single package substrate, integrating them into one cohesive unit. This merging approach maintains the vector measurement capability while simplifying the packaging structure and reducing overall device complexity compared to separate packaging of multiple chips.
Solution Approach 2:
The package substrate serves multiple functions: it provides mechanical support for all sensor chips, enables electrical interconnection between different axis sensors, facilitates signal routing to external circuits, and maintains proper spatial orientation. This multi-functional design reduces the need for additional components and simplifies the overall packaging system.
2Measurement precision
If multiple sensor chips are used for triaxial measurement, then measurement precision is improved, but the size of the sensor increases
Solution Approach 1:
The patent arranges the X-axis, Y-axis, and Z-axis sensor chips in a compact nested configuration on the package substrate. The sensors are positioned to utilize vertical and lateral space efficiently, with each sensor chip occupying a minimized footprint while maintaining proper orthogonal orientation for triaxial measurement capability.
3Ease of manufacture
If GMR materials are deposited on the same wafer for different sensor axes, then manufacturing simplicity is improved, but magnetic moment alignment becomes difficult
Solution Approach 1:
The patent applies different magnetic field orientations and annealing conditions to specific regions of the wafer corresponding to different sensor axes. By controlling the local magnetic field direction during deposition and post-deposition annealing, the pinned layer magnetization can be precisely aligned for each axis (X, Y, and Z) while maintaining single-wafer fabrication simplicity.
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 solution achieves a high level of integration, higher sensitivity, lower power consumption, good linearity, wide dynamic range, and low noise performance, addressing the limitations of existing triaxial sensors.
Implementation Method 1
Magnetic Tunnel Junctions (MTJ) have begun finding acceptance in industrial applications as a new type of magnetoresistive sensor, using the Tunneling Magnetoresistance (TMR) Effect of magnetic multilayer materials. In this effect the magnitude and direction of a magnetic field applied to the multilayered film changes of the resistance of the multilayer film.
Data Source
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AI summary
The present invention discloses a MTJ triaxial magnetic field sensor, comprising an X-axis bridge sensor that has a sensing direction along an X-axis, a Y-axis bridge sensor that has a sensing direction along a Y-axis, a Z-axis sensor that has a sensing direction along a Z-axis, and an ASIC chip connected with and matched to the X-axis, Y-axis, and Z-axis sensor chips. The Z-axis sensor includes a substrate and MTJ magnetoresistive elements deposited on the substrate. The Z axis magnetic field sensor is attached to the ASIC chip along an attachment edge, and an angle is formed between the sensor side of the Z axis magnetic field sensor and the adjacent attachment edge. The attachment edge angle is an acute angle or an obtuse angle. The resulting X, Y, and Z axes are mutually orthogonal. The above design provides a highly integrated sensor with high sensitivity, low power consumption, good linearity, wide dynamic range, excellent thermal stability, and low noise.