Polygon TMR Sensor Layout for Low Hysteresis at High Fields
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Solution Overview
Problem
Magnetoresistive sensor elements exhibit hysteresis and performance degradation under high magnetic fields and high temperature conditions, requiring frequent redesigns of sensor layouts and additional hard magnetic layers for stability.
Innovation Solution
A magnetic sensor design comprising magnetoresistive sensor elements with a stable vortex configuration and polygon shapes, where adjacent elements are rotated by 360°/2n relative to each other, eliminating the need for layout redesigns and additional hard magnetic layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetoresistive sensor element uses a vortex configuration in the sense layer to achieve wide magnetic field range and good linearity, then the sensor provides wider magnetic field range and better linearity, but the sensor exhibits hysteresis and perming offset effect after subjected to high magnetic field or high temperature heat treatment
Solution Approach 1:
The patent applies asymmetry by introducing a specific geometric asymmetry in the sense layer structure (e.g., asymmetric shape or asymmetric magnetic layer configuration) that creates a preferred magnetization direction, stabilizing the vortex configuration and preventing chirality switching under high magnetic fields and temperature, thereby eliminating hysteresis and perming offset effects
Solution Approach 2:
The patent changes physical parameters such as the thickness of magnetic layers, the geometry of the sense layer, or material composition to optimize the vortex stability. By adjusting these parameters, the sensor maintains stable vortex configuration and eliminates hysteresis while preserving wide magnetic field range and linearity
2Stability of the object's composition
If additional hard magnetic layers are added to prevent chirality switching and reduce perming offset, then the stability under heat treatment and high magnetic fields is improved, but the device complexity and manufacturing process are increased
Solution Approach 1:
The patent extracts or removes the additional hard magnetic layer from the structure, achieving chirality switching prevention through the inherent properties of a simplified structure, such as through geometric confinement or interfacial effects in a single-layer or reduced-layer configuration
Solution Approach 2:
The patent makes a single layer or structure perform multiple functions: it provides both the sensing function and the stability against chirality switching, eliminating the need for separate hard magnetic layers. The sense layer itself is designed to be both sensitive and stable through its specific geometry or material properties
3Measurement precision
If the thickness of the sense layer or sense magnetization is varied to optimize performance, then the sensor performance is improved, but the lithography mask and sensor layout must be redesigned
Solution Approach 1:
The patent segments the sensor into modular units with standardized geometries that can be reused. By creating a library of standardized sense layer patterns, performance optimization can be achieved through selection and combination of modules without requiring complete redesign of lithography masks
Solution Approach 2:
The patent performs preliminary design work by establishing a set of standardized lithography masks and layout patterns that can accommodate different sense layer thicknesses and magnetization configurations. This preliminary standardization allows performance optimization without subsequent mask redesigns
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 sensor achieves low hysteresis and maintains wide linear response under high magnetic fields and temperatures, enhancing robustness and simplifying manufacturing by avoiding layout adjustments and additional hard magnetic layers.
Implementation Method 1
A magnetic sensor comprising a plurality of magnetoresistive sensor elements, such as tunnel magnetoresistance TMR based elements
Implementation Method 2
The sense magnetization can comprise a vortex configuration whereby the magnetization curls in a circular path along the edge of the sense layer
Implementation Method 3
a sense magnetization comprising a vortex configuration exhibits a hysteresis after the magnetoresistive sensor element has been subjected to a high magnetic field or/and a high temperature heat treatment
Data Source
AI summary
The present disclosure concerns a magnetic sensor (100) for sensing an external magnetic field, comprising a plurality of magnetoresistive sensor elements (10), each comprising a reference layer (21) having a reference magnetization (210), a sense layer (23) having a sense magnetization (230) comprising a stable vortex configuration, and a tunnel barrier layer (22). In a layer plane (PL) of the layers (21, 22, 23), each magnetoresistive sensor element (10) has a regular polygon shape comprising n vertices and has a lateral size (D) in the layer plane (PL) between 0.2 pm and 5 pm. Each magnetoresistive sensor element (10) has an aspect ratio of its thickness (ty) to its lateral size (D) between 0.005 and 2. Each magnetoresistive sensor element (10) is rotated in the layer plane (PL) by 36072n relative to an adjacent magnetic sensor element (10). Alternatively, the reference magnetization (210) of each magnetoresistive sensor elements (10) is rotated by 36072n in the layer plane (PL) relative to the reference magnetization (210) of an adjacent magnetoresistive sensor element (10).