Magnetoresistive Sensor Wafer Layout for Laser-Defined Magnetic Orientation
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Solution Overview
Problem
Existing magnetoresistive sensor technologies face challenges in accurately measuring magnetic fields over 0 to 360 degrees due to mechanical alignment errors, complexity in die placement, and the introduction of soft ferromagnetic flux concentrators, which affect linearity and increase manufacturing complexity.
Innovation Solution
A magnetoresistive sensor wafer layout with spatially-isolated orientation groups and a laser scanning method that magnetically orients antiferromagnetic layers in magnetoresistive sensing units, allowing for efficient production of single-axis or double-axis push-pull sensors without mechanical alignment and soft ferromagnetic flux concentrators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical alignment of dice is used to create push-pull magnetoresistive sensors, then the sensors can be manufactured with multiple orientation angles, but angle errors occur that degrade sensor performance
Solution Approach 1:
The patent replaces the mechanical alignment system with a laser-based magnetic field orientation system. Instead of physically rotating and aligning dice mechanically, the invention uses laser irradiation to heat the antiferromagnetic layer and apply magnetic fields to orient the magnetization direction precisely along desired axes (X, Y, or both). This substitution eliminates mechanical alignment errors while achieving the same multi-directional sensing capability.
Solution Approach 2:
The patent changes the control parameter from mechanical rotation angle to laser heating temperature and magnetic field strength. By controlling the laser irradiation parameters (power, duration, scanning pattern) and magnetic field parameters (strength, direction, timing), the magnetization orientation can be precisely adjusted to achieve accurate X-axis, Y-axis, or combined axis orientations without mechanical intervention.
2Adaptability or versatility
If multiple dice are used to achieve push-pull sensing units with different orientations, then the sensing coverage is improved, but the process complexity increases due to die placement and connection
Solution Approach 1:
The patent merges multiple sensing units with different orientations into a single integrated sensor chip. Instead of using separate dice that need to be placed and connected, the invention creates multiple magnetoresistive sensing units on one chip, each with magnetization oriented along different axes (X, Y, or both) through selective laser writing. This integration eliminates the complexity of mechanical die placement and electrical interconnections while maintaining the push-pull sensing capability across multiple axes.
Solution Approach 2:
The patent creates a universal sensor chip that can function as X-axis, Y-axis, or two-axis magnetoresistive sensor depending on the magnetization orientation pattern. By controlling the laser writing process to create different magnetization directions in different regions of the same chip, a single device can provide multi-directional sensing coverage that previously required multiple separate components.
3Ease of operation
If soft ferromagnetic flux concentrators are introduced to steer magnetic field direction, then the magnetic field direction can be controlled, but the process complexity increases and linearity is affected by hysteresis
Solution Approach 1:
The patent extracts and removes the soft ferromagnetic flux concentrator component from the sensor structure. Instead of using these additional magnetic steering components, the invention directly controls the magnetization orientation of the antiferromagnetic layer through laser-induced heating and magnetic field application. This extraction eliminates the need for complex flux concentrator fabrication and assembly processes while maintaining precise magnetic field direction control through the oriented magnetization layers themselves.
4Manufacturing precision
If comprehensive laser scanning is performed on all magnetoresistive sensing units, then complete coverage is achieved, but the scanning time increases significantly
Solution Approach 1:
The patent segments the wafer into multiple zones corresponding to different magnetization orientation groups (X-axis oriented, Y-axis oriented, or combined). Instead of scanning the entire wafer uniformly, the laser scanning is segmented into targeted regions based on the required orientation groups. This allows parallel or sequential processing of different orientation zones, reducing total scanning time while maintaining precise magnetization control in each segment.
Solution Approach 2:
The patent applies partial action by scanning only the necessary portions of the wafer for each orientation group rather than performing exhaustive scanning of all areas. The laser scanning parameters (power, speed, pattern) are optimized to achieve sufficient magnetization orientation with minimal exposure, avoiding excessive scanning that would waste time without adding benefit. This partial action approach maintains manufacturing precision while significantly improving productivity.
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 solution reduces the time required for laser scanning and improves the efficiency of the laser writing process while producing high-quality push-pull bridge magnetic sensors with reduced errors and increased manufacturing simplicity.
Implementation Method 1
the multilayer film structures of the magnetoresistive sensing units, the magnetoresistive sensing units such as TMR or GMR spin-valve magnetoresistive sensing units are heated to a temperature above the blocking temperature of the antiferromagnetic layer by scanning a laser
Implementation Method 2
applying an external magnetic field in the direction of X or −X, Y or −Y as well as the direction at a (−90,+90) extended angle is applied along a particular direction in the cooling process, and thus push-pull single-axis or double-axis magnetoresistive sensors can also be produced, so that the magnetization direction of the antiferromagnetic layer can be changed by laser thermal annealing
Data Source
AI summary
A magnetoresistive sensor wafer layout scheme used for a laser writing system and laser scanning method are disclosed. The layout scheme comprises a magnetoresistive multilayer film including an antiferromagnetic pinning layer arranged into a rectangular array of sensor dice on the wafer surface. Pinning layers of magnetoresistive sensing units are magnetically oriented and directionally aligned by the laser writing system. Sensing units are electrically connected into bridge arms electrically connected into a magnetoresistive sensor. Magnetoresistive sensing units in the dice are arranged into at least two spatially-isolated magnetoresistive orientation groups. In the magnetoresistive orientation groups, pinning layers of the sensing units have an angle of magnetic orientation of 0-360 degrees. Angles of magnetic orientation of two adjacent magnetoresistive orientation groups are different. Each orientation group is adjacent to an orientation group with the same angle of magnetic orientation in at least one adjacent die.