MR Sensor Free-Layer Dusting for Out-of-Plane Anisotropy Control
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Solution Overview
Problem
Existing magnetic field sensors face challenges in achieving optimal out-of-plane sensing sensitivity due to limitations in controlling the magnetic anisotropy of the free layer.
Innovation Solution
The solution involves manipulating the thickness of the CoFeB layer and using a textured metallic oxide dusting layer, such as MgO, to achieve defined perpendicular magnetic anisotropy, thereby controlling the out-of-plane sensitivity of the magnetic sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the CoFeB layer is increased, then the out-of-plane sensitivity is improved, but the magnetic anisotropy control becomes difficult
Solution Approach 1:
The patent applies parameter changes by systematically varying the thickness of the CoFeB layer (from 0.5 nm to 2.0 nm in different embodiments) to optimize the balance between out-of-plane sensitivity and magnetic anisotropy control. This parameter adjustment allows the free layer to achieve the desired perpendicular magnetic anisotropy while maintaining high sensitivity for out-of-plane magnetic field detection.
Solution Approach 2:
The patent uses composite material structures by combining CoFeB with MgO layers in a magnetoresistive element stack. This composite structure enables the CoFeB free layer to exhibit enhanced perpendicular magnetic anisotropy and improved out-of-plane sensitivity simultaneously, resolving the contradiction between sensitivity enhancement and anisotropy control.
2Measurement precision
If a dusting layer is added to control magnetic anisotropy, then the sensitivity is improved, but the device complexity increases
Solution Approach 1:
The patent introduces a MgO dusting layer as an intermediary element between the CoFeB free layer and the surrounding environment. This thin oxide layer serves as a mediator that provides perpendicular magnetic anisotropy through interfacial effects, enabling sensitivity control without requiring complex additional structures or mechanisms.
Solution Approach 2:
The patent applies local quality by placing the MgO dusting layer specifically at the interface with the CoFeB free layer where it is needed for anisotropy control. This localized approach allows sensitivity optimization at the critical interface region without adding complexity to the entire device structure, maintaining simplicity elsewhere in the stackup.
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 allows for precise tuning of the magnetic anisotropy, enhancing the out-of-plane sensitivity and linearity of the magnetic sensor, leading to improved performance in magnetic field detection.
Implementation Method 1
controlling a thickness of a dusting layer of an oxide material on the free layer to achieve perpendicular magnetic anisotropy for an interface of the oxide material and the CoFeB
Implementation Method 2
the perpendicular magnetic anisotropy occurs as a result of hybridization between 2p and 3d orbitals of Oxygen in the oxide layer and Fe in the CoFeB
Implementation Method 3
magnetic field sensors include magnetoresistance elements which have an electrical resistance that changes in the presence of an external magnetic field
Data Source
AI summary
Methods and apparatus for a magnetoresistive (MR) sensor a free layer with a thickness of the CoFeB material to produce out-of-plane sensing for the sensor and a reference layer magnetically coupled to the free layer. A dusting layer of an oxide material is disposed on the free layer to achieve perpendicular magnetic anisotropy for an interface of the oxide layer and the free layer for a desired sensitivity for the sensor.