Single-Chip Magnetoresistive Sensor with Laser Annealing
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Solution Overview
Problem
Existing single-axis magnetoresistive linear sensors face challenges in precision due to the need for accurate alignment of two chips and increased complexity in manufacturing multi-layer film structures, which can lead to measurement precision loss and process complexity.
Innovation Solution
A single-chip high-sensitivity magnetoresistive linear sensor is developed, where the magnetic field sensing directions of magnetoresistive sensing units are set by laser-assisted magnetic field annealing, using a soft ferromagnetic flux concentrator array and magnetoresistive sensing units with a shared multi-layer film structure, allowing for precise orientation and alignment on a single chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two magnetoresistive sensing unit chips are flipped and positioned to form a push-pull bridge, then the manufacturing method is simple and only one type of chip structure is required, but two chips need to be accurately positioned within the same plane which increases the possibility of measurement precision loss
Solution Approach 1:
The patent merges two separate magnetoresistive sensing unit chips into a single integrated chip structure. The push-pull bridge is formed by integrating both the push sensing unit and pull sensing unit on the same substrate, eliminating the need for separate chip positioning and alignment operations. This integration maintains manufacturing simplicity while eliminating alignment errors between chips.
Solution Approach 2:
The patent introduces a shared ferromagnetic reference layer as an intermediary element that couples both the push and pull sensing units. This shared reference layer serves as a common reference for both sensing units, enabling the push-pull configuration to be implemented on a single chip without requiring precise positioning of separate chips, thereby maintaining measurement precision.
2Adaptability or versatility
If push and pull magnetoresistive sensing units are manufactured by modifying the ferromagnetic reference layer within a multi-layer film structure, then push and pull sensing units with opposite ferromagnetic reference layers can be manufactured, but the complexity of the process is increased as at least two kinds of multi-layer film structures need to be introduced
Solution Approach 1:
The patent applies local quality by introducing magnetic field annealing treatment to specific regions of the ferromagnetic reference layer. Instead of creating different multi-layer film structures for push and pull sensing units, the same film structure is used for both, and the desired opposite magnetization directions are achieved by applying localized magnetic fields during annealing. This reduces process complexity while maintaining the ability to control sensing directions.
Solution Approach 2:
The patent changes the magnetic state parameter of the ferromagnetic reference layer through magnetic field annealing. By applying external magnetic fields during the annealing process, the magnetization direction of the ferromagnetic reference layer is controlled to achieve the desired push-pull configuration. This parameter change approach avoids the need for complex multi-layer film structures with different layer counts.
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 enhances precision, reduces size, and lowers power consumption while simplifying the manufacturing process by eliminating the need for precise chip alignment and reducing the complexity of multi-layer film deposition.
Implementation Method 1
the external magnetic field is amplified using a soft ferromagnetic flux concentrator
Implementation Method 2
an anti-ferromagnetic layer is rapidly heated to a temperature above the blocking temperature; and meanwhile, a magnetic field can be applied in any direction during the cooling process
Implementation Method 3
magnetic field sensing directions of the magnetoresistive sensing units are set by laser assisted magnetic field annealing
Implementation Method 4
TMR magnetoresistive sensor
Data Source
Figure 1
Figure 2~4
Figure 5(a1)~5(b3)
AI summary
The present invention discloses a single-chip high-sensitivity magnetoresistive linear sensor, which comprises a substrate located in the X-Y plane and a soft ferromagnetic flux concentrator array located on the substrate. The soft ferromagnetic flux concentrator array comprises several soft ferromagnetic flux concentrators, wherein there is a gap between each two adjacent soft ferromagnetic flux concentrators. The +X and -X magnetoresistive sensing unit array respectively comprises +X and -X magnetoresistive sensing units located in the gaps. The +X and -X magnetoresistive sensing units are electrically interconnected to form a push pull X-axis magnetoresistive sensor. Each of the magnetoresistive sensing units that have the same magnetic field sensing direction are arranged in adjacent locations. The magnetoresistive sensing units are all MTJ magnetoresistive sensor elements, and each has the same magnetic multi-layer film structure. Laser magnetic annealing is used to scan and prepare the magnetic sensing array. The invention has the advantages of small size, high precision and low power consumption.