Magnetic Sensor Permanent Magnet with AFM Barrier
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Solution Overview
Problem
Magnetic sensors with permanent magnets face performance degradation due to external influences like high temperatures, especially when these sensors are designed to measure changes in multiple directions, as the magnets' orientation can be affected by the earth's magnetic field and high processing temperatures.
Innovation Solution
The use of permanent magnets with alternating ferromagnetic and antiferromagnetic layers, where a barrier layer is disposed between the FM and AFM layers, allows for magnetization in specific directions at temperatures higher than the blocking temperature of the AFM layer, ensuring stability and maintaining desired magnetic properties even after exposure to external magnetic fields and high processing temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If permanent magnets are magnetized in different directions to measure changes in multiple directions, then the measurement capability in multiple directions is improved, but the sensitivity to external magnetic fields and temperature effects increases
Solution Approach 1:
The patent uses composite magnetic structures combining ferromagnetic and antiferromagnetic layers with specific barrier layers. This composite approach allows the magnet to maintain stable magnetization in multiple directions while resisting external magnetic field interference and temperature effects, thus improving reliability without sacrificing multi-directional measurement capability
Solution Approach 2:
The patent utilizes blocking temperature as a critical parameter to control the magnetic properties. By ensuring the operating temperature remains below the blocking temperature of the antiferromagnetic layer, the magnetization direction is stabilized. This parameter control allows the sensor to maintain reliable performance across multiple measurement directions while resisting external field interference
2Ease of manufacture
If permanent magnets are subjected to high processing temperatures during device fabrication, then the manufacturing process is completed, but the magnetic orientation and performance of the sensors deteriorate
Solution Approach 1:
The patent applies magnetic field treatment to establish the desired magnetization direction before the high-temperature processing step. This preliminary action ensures that the magnetic orientation is set while the material is still in a controllable state, and the subsequent high temperature processing does not disrupt the established magnetization due to the protective barrier layers and antiferromagnetic pinning
Solution Approach 2:
The barrier layer acts as an intermediary between the ferromagnetic and antiferromagnetic layers, protecting the magnetic orientation during high-temperature processing. This intermediary structure allows the device to withstand fabrication temperatures while maintaining the precision of magnetic orientation established during earlier stages
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 configuration maintains the magnetic orientation and properties of the permanent magnets across various temperatures and magnetic field ranges, enhancing the reliability and accuracy of magnetic sensors in multi-axis measurements.
Implementation Method 1
The first permanent magnet is magnetized in a first direction at a temperature higher than a blocking temperature of the AFM layer
Implementation Method 2
with a barrier layer disposed between the FM layer and the AFM layer
Implementation Method 3
Magnetic sensors with movable permanent magnets embedded in a device may be configured to measure change in the orientation of the device, based on the change in the position of the movable permanent magnet with reference to the earth's magnetic field
Implementation Method 4
the plurality of device pads are selectively eutectic bonded to the plurality of IC pads at a bonding temperature greater than the blocking temperature of the AFM layer
Data Source
AI summary
A device with a magnetic sensor includes a substrate with a device layer. A magnetic sensor is formed on the device layer and includes a first permanent magnet. The first permanent magnet has at least one alternating ferromagnetic (FM) layer and antiferromagnetic (AFM) layer, with a barrier layer disposed between the FM layer and the AFM layer. The first permanent magnet is magnetized in a first direction at a temperature higher than a blocking temperature of the AFM layer. A plurality of device pads are coupled to the magnetic sensor. An integrated circuit substrate with a plurality of IC pads, wherein the plurality of device pads are selectively eutectic bonded to the plurality of IC pads at a bonding temperature greater than the blocking temperature of the AFM layer of the first permanent magnet.