Magnetic Pre-conditioning of MTJ Sensors
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Solution Overview
Problem
Micro-magnetic sensors, such as magnetic tunnel junction (MTJ) sensors, face challenges in maintaining stability and accuracy due to spurious magnetic effects from external ferromagnetic sources, leading to degraded performance and noise levels.
Innovation Solution
Applying a magnetic pre-conditioning field along the long axes of the flux guides after fabrication but before testing, using a magnetic yoke or handler system to align and expose the sensors to a field of sufficient magnitude, typically around 100 Gauss, to align magnetic domains and eliminate rogue states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If magnetic sensors are manufactured using conventional micro-electronic manufacturing techniques, then manufacturing precision and scalability are improved, but spurious magnetic effects from external ferromagnetic sources cause degraded sensor performance and increased noise levels
Solution Approach 1:
The patent applies preliminary magnetic pre-conditioning to the flux guide before the sensor is put into service. A magnetic field is applied along the long axis of the flux guide to align magnetic domains and establish a known initial magnetic state, thereby eliminating spurious effects from external ferromagnetic sources and ensuring stable sensor performance from the start
Solution Approach 2:
The patent changes the magnetic field parameters (applying a strong conditioning field of sufficient magnitude along the long axis of the flux guide) to transform the magnetic state of the flux guide from an unknown/unstable state to a known/stable state, thereby resolving the performance degradation caused by spurious magnetic effects
2Measurement precision
If magnetic pre-conditioning is applied after fabrication but before testing, then sensor response stability and calibration accuracy are improved, but additional processing time and complexity are introduced
Solution Approach 1:
The patent merges the magnetic pre-conditioning step with the existing fabrication and testing workflow by integrating it into the handler system that already handles sensors after fabrication. The conditioning field is applied in situ during normal handling operations, combining multiple functions into a unified process flow
Solution Approach 2:
The patent uses a magnetic yoke or handler system with integrated magnets as an intermediary device to apply the conditioning field. This intermediary structure enables efficient magnetic field application during normal sensor handling without requiring separate dedicated equipment or complex setup procedures
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 method stabilizes the sensor response, reduces noise, and ensures accurate calibration by purging spurious effects, thereby enhancing the responsiveness and reliability of the micro-magnetic sensors.
Implementation Method 1
exposing the fabricated sensor device to a magnetic field having a component aligned along a long axis of the flux guide, the component having a magnitude along the long axis of the flux guide sufficient to place the flux guide into a known magnetic state
Implementation Method 2
Magnetic tunnel junction (MTJ) sensors, for example, detect the presence of magnetic fields using tunnel magnetoresistance (TMR) effects
Data Source
AI summary
Methods, systems and apparatus are provided to apply a magnetic pre-conditioning to magnetic tunneling junction (MTJ) sensors and other micro-magnetic devices after fabrication but before testing, trimming or other subsequent processing. The fabricated sensor device is passed through a magnetic field that has a known direction and orientation relative to the device so that the device is placed into a known state prior to final testing and trimming. Various embodiments allow the field to be applied in situ by a permanent magnet or electromagnet as the devices are being processed by a conventional device handler or similar processing system.