Monolithic Three-Axis Magnetic Sensor Using Trench and Bump Structures
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Solution Overview
Problem
Current three-axis magnetic sensors require complex geometric arrangements and additional packaging steps, leading to increased manufacturing costs and thickness, as they struggle to simultaneously detect magnetic flux in all three axes with high accuracy and low profile.
Innovation Solution
Fabricating two magnetic sensor Wheatstone bridges with barber pole AMR structures on opposite sides of a bump structure at a predetermined angle on a silicon substrate, allowing for the detection of Y and Z axis signals, with the X axis signal provided on a level surface, enabling a low-profile, cost-effective, high-performance three-axis magnetic sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three sensors are encapsulated separately and soldered on a PCB as a module with the Z axis sensor mounted vertically, then three-axis sensitivity is achieved, but manufacturing cost increases significantly and product thickness increases
Solution Approach 1:
The patent combines three magnetic field sensing devices into a single integrated sensor unit on one substrate, eliminating the need for separate packaging and soldering operations. The X and Y axis sensors are positioned on the substrate surface while the Z axis sensor is positioned in a trench, creating a unified three-axis sensing system that reduces manufacturing complexity and cost.
Solution Approach 2:
The patent transitions from a planar two-dimensional sensor arrangement to a three-dimensional configuration by positioning the Z axis sensor in a trench below the substrate surface. This vertical dimensionality allows the Z axis sensor to detect magnetic fields perpendicular to the substrate while sharing the same package footprint with the X and Y axis sensors.
2Adaptability or versatility
If three sensors are encapsulated separately and soldered on a PCB as a module with the Z axis sensor mounted vertically, then three-axis sensitivity is achieved, but the thickness of the final product increases
Solution Approach 1:
The patent positions the Z axis sensor in a trench that extends vertically below the substrate surface, utilizing the depth dimension rather than increasing the topological thickness. This allows the Z axis sensing capability to be integrated without adding significant height to the sensor package, as the vertical component is accommodated within the trench structure rather than extending the overall product thickness.
3Adaptability or versatility
If a Z axis magnetic field sensor is mounted vertically to detect magnetic flux perpendicular to the device plane, then Z axis detection capability is achieved, but positioning angle variation introduces cross-talk signals from the XY plane
Solution Approach 1:
The patent divides the sensing function into three separate sensor elements, each optimized for a specific axis: the X and Y axis sensors are positioned on the substrate surface for in-plane detection, while the Z axis sensor is positioned in a trench for out-of-plane detection. This spatial segmentation allows each sensor to be optimized for its specific detection direction, reducing cross-talk between axes.
Solution Approach 2:
The trench structure serves as an intermediary that positions the Z axis sensor at a controlled depth below the substrate surface. This intermediary structure provides a stable mounting platform that maintains the vertical orientation of the Z axis sensor, preventing angle variation and the associated cross-talk signals while allowing the sensor to detect magnetic flux perpendicular to the device plane.
4Adaptability or versatility
If sensors are positioned on a sloped surface to achieve multi-axis sensitivity, then three-axis detection is achieved, but manufacturing precision is compromised due to difficulty in creating uniform inclined angles
Solution Approach 1:
Instead of creating a single sloped surface, the patent segments the sensing arrangement into three distinct positions: two sensors on the flat substrate surface for X and Y axis detection, and one sensor positioned in a trench for Z axis detection. This segmentation eliminates the need for precise inclined angles while achieving three-axis sensitivity through vertical positioning.
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 simplifies the manufacturing process, reduces costs, and enhances accuracy by averaging out angle variations, allowing for precise detection of magnetic fields in all three axes without significant cross-talk signals.
Implementation Method 1
Known magnetoresistive (MR) sensors, such as AMR (anisotropic MR) sensors, GMR (giant MR) sensors, TGMR (tunneling GMR) sensors, and the like, however, can only detect magnetic flux that is parallel to the device plane
Implementation Method 2
Hall-effect sensors can sense magnetic flux that is perpendicular to the device plane, i.e., along the Z axis
Data Source
AI summary
A three-axis magnetic sensor or magnetometer is provided. Two magnetic sensor Wheatstone bridges using barber pole AMR structures are fabricated on opposite sides of a bump structure formed on a substrate to provide surfaces that are at a predetermined angle with respect to the flat surface of the substrate. The bridge assembly is oriented along the Y axis and the bridges are interconnected such that Y and Z channel signals can be produced by processing of the bridge signals. The X channel signals are provided by an X axis sensor provided on the level surface of the substrate.