Single-Chip Push-Pull Magnetic Sensor With Uniform Pinning Layers
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Solution Overview
Problem
Existing single chip push-pull bridge-type magnetic field sensors face challenges in manufacturing complexity, high cost, reduced sensitivity, and difficulty in achieving precise alignment of magnetization directions, leading to offset voltage issues and reduced performance in high-intensity magnetic fields.
Innovation Solution
The use of GMR or TMR magnetoresistance sensing elements with perpendicular free layer magnetization directions, achieved through permanent magnet biasing, double exchange interaction, or shape anisotropy, and the implementation of elongated flux concentrators made of soft ferromagnetic alloys, allows for identical pinning layer magnetization directions and parallel sensing elements, reducing manufacturing complexity and enhancing sensitivity and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two-step film forming process or local laser assisted magnetic annealing is used to set opposite magnetization directions of pinning layers, then single chip bridge-type sensor can be achieved, but fabrication process becomes complicated and manufacturing precision deteriorates
Solution Approach 1:
Instead of making adjacent pinning layers have opposite magnetization directions, the invention makes them have the same magnetization direction. The push-pull effect is achieved by tilting the free layer magnetization directions differently in adjacent arms, while keeping pinning layers uniform. This inversion of the approach simplifies the fabrication process and improves film consistency.
Solution Approach 2:
The invention changes the parameter being controlled from pinning layer magnetization direction to free layer magnetization direction. By maintaining uniform pinning layers and introducing controlled variations in free layer orientation (through shape anisotropy or stress), the invention achieves the push-pull effect while avoiding complex fabrication processes.
2Adaptability or versatility
If magnetization directions of pinning layers in adjacent arms are set oppositely, then push-pull bridge-type sensor function is achieved, but device complexity increases
Solution Approach 1:
The invention inverts the conventional approach by making pinning layers have the same magnetization direction and achieving the push-pull effect through free layer orientation differences. This reduces device complexity while maintaining the desired sensor function.
Solution Approach 2:
The invention applies local quality by creating different free layer orientations only in specific regions (adjacent bridge arms) while keeping the pinning layers uniform across the entire device. This is achieved through local shape anisotropy or stress applied to specific free layers, reducing overall device complexity.
3Measurement precision
If multi-chip packaging with 180 degree rotation is used, then detection sensitivity and temperature compensation are improved, but packaging size increases and production cost increases
Solution Approach 1:
The invention merges multiple sensor chips into a single chip by fabricating all magnetoresistance sensing elements on one substrate with identical pinning layer magnetization directions. The push-pull bridge configuration is achieved through controlled free layer orientations, eliminating the need for multi-chip packaging and reducing overall size.
Solution Approach 2:
The invention segments the sensor into multiple magnetoresistance sensing elements on a single chip, each with appropriately oriented free layers to create push and pull arms. This segmentation allows the bridge configuration to be achieved on one chip rather than requiring multiple chips.
4Ease of manufacture
If free layer magnetization directions are tilted to achieve single chip bridge-type sensor, then manufacturing is simplified, but sensor response to magnetic field and sensitivity are reduced
Solution Approach 1:
The invention applies local quality by creating different free layer orientations only where needed (in adjacent bridge arms) while maintaining optimal orientations for magnetic field detection. This localized differentiation achieves the push-pull effect without compromising overall sensor sensitivity.
Solution Approach 2:
The invention uses composite magnetic layer structures with carefully engineered free and pinned layers. By optimizing the magnetic properties and thickness of each layer, the invention achieves both the desired free layer orientation control and high sensor sensitivity simultaneously.
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 results in a smaller, cost-effective, high-sensitivity, and linear single chip push-pull bridge-type magnetic field sensor with a wider dynamic range and reduced noise, suitable for high-intensity magnetic fields without the need for complex two-step processes or multi-chip packaging.
Implementation Method 1
The sensor utilizes the tunnel magnetoresistance effect of a magnetic multilayer film material to sense a magnetic field, which is mainly manifested in: in a magnetic multilayer film material, wherein the resistance of a magnetic multilayer film changes, as the magnitude and direction of an external magnetic field changes.
Implementation Method 2
Prior art push-pull bridge-type magnetic field sensors use a permanent magnet to bias the magnetization directions of the magnetoresistance elements
Implementation Method 3
the implementation of elongated flux concentrators made of soft ferromagnetic alloys, allows for identical pinning layer magnetization directions and parallel sensing elements, reducing manufacturing complexity and enhancing sensitivity and linearity
Data Source
Figure 1~2
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Figure 4
AI summary
A single chip push-pull bridge-type magnetic field sensor. The sensor comprises a substrate (1), bonding pads (6-9), magnetoresistance sensing elements (10, 11), and flux concentrators (12, 13), wherein the magnetoresistance sensing elements (10, 11) are positioned in the clearances (14, 15) of the adjacent flux concentrators (12, 13), and the directions of the pinning layers of the magnetoresistance sensing elements (10, 11) are identical. The flux concentrators (12, 13) are divided into a push arm type and a pull arm type, the included angle between one type and an X-axis forward direction is positive, and the included angle between the other type and the X-axis forward direction is negative. The working principle of the sensor is that the magnetic field along the X-axis direction in the clearances (14, 15) of the flux concentrators (12, 13) are oppositely oriented. The sensor has the advantages of small size, low cost, simplicity in manufacturing, high sensitivity, good linearity, high sensitivity, wide working dynamic range, and the like.