MgO Interlayer TMR Sensor Stack for Higher Sensitivity and Linear Range
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Solution Overview
Problem
Magnetoresistive sensors, particularly TMR sensors, face challenges in enhancing sensitivity and linear range while maintaining accuracy, and in reducing angle errors, due to limitations in magnetic anisotropy and interlayer effects.
Innovation Solution
Incorporating a magnesium oxide interlayer between ferromagnetic layers in the magnetoresistive sensor stack to increase perpendicular magnetic anisotropy and TMR effect through interlayer exchange coupling, which allows for thicker sensor layers and improved performance in both linear and angle sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetoresistive sensor structures are used, then manufacturing is simpler, but sensitivity and TMR effect are limited
Solution Approach 1:
The patent employs composite material structures by integrating multiple ferromagnetic layers (CoFeB, CoFe) with non-magnetic spacer layers (Ru, Ta) and oxide layers (MgO) to create a magnetically free system. This composite approach enables enhanced perpendicular magnetic anisotropy and interlayer exchange coupling, achieving higher sensitivity and TMR effect while managing the complexity through systematic material composition
2Measurement precision
If thicker sensor layers are used to improve performance, then sensitivity increases, but magnetic anisotropy control becomes more difficult
Solution Approach 1:
The patent systematically varies critical parameters including the thickness of ferromagnetic layers (CoFeB: 0.5-2.0 nm, CoFe: 1.0-3.0 nm), spacer layers (Ru: 0.3-0.8 nm, Ta: 0.1-0.5 nm), and oxide layers (MgO: 0.5-2.0 nm) to optimize perpendicular magnetic anisotropy. By controlling these parameters within specific ranges, the patent achieves both thicker effective sensor layers for improved sensitivity and precise magnetic anisotropy control
3Measurement precision
If conventional interlayer structures are used, then device complexity is lower, but angle errors increase
Solution Approach 1:
The patent introduces non-magnetic spacer layers (Ru, Ta) and oxide layers (MgO) as intermediary elements between ferromagnetic layers. These intermediary layers serve multiple functions: they provide precise thickness control for magnetic coupling, reduce magnetic dead layers that cause angle errors, and enable independent optimization of each ferromagnetic layer's magnetization direction, thereby improving angle sensor accuracy
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 magnesium oxide interlayer enhances sensitivity and linear range of magnetoresistive sensors by increasing magnetic anisotropy and TMR effect, while minimizing angle errors and magnetic dead layers, thereby improving overall sensor performance.
Implementation Method 1
Incorporating a magnesium oxide interlayer between ferromagnetic layers in the magnetoresistive sensor stack to increase perpendicular magnetic anisotropy and TMR effect through interlayer exchange coupling
Implementation Method 2
increase perpendicular magnetic anisotropy and TMR effect through interlayer exchange coupling
Implementation Method 3
TMR stands for Tunnel MagnetoResistance (TMR), which is a magnetoresistive effect that occurs in a magnetic tunnel junction (MTJ)
Implementation Method 4
The barrier layer is arranged between the reference layer and the magnetically free system and includes magnesium oxide
Data Source
AI summary
Exemplary embodiments are directed to magnetoresistive sensors and corresponding fabrication methods for magnetoresistive sensors. One example of a magnetoresistive sensor includes a layer stack, wherein the layer stack includes a reference layer having a fixed reference magnetization, wherein the fixed reference magnetization has a first magnetic orientation. The layer stack furthermore includes a magnetically free system of a plurality of layers, wherein the magnetically free system has a magnetically free magnetization, wherein the magnetically free magnetization is variable in the presence of an external magnetic field, and wherein the magnetically free magnetization has a second magnetic orientation in a ground state. The magnetically free system has two ferromagnetic layers and an interlayer, wherein the interlayer is arranged between the two ferromagnetic layers and includes magnesium oxide. The layer stack furthermore includes a barrier layer, which is arranged between the reference layer and the magnetically free system and includes magnesium oxide.