Single-Chip Magnetic Sensor Bridge Offset Compensation
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Solution Overview
Problem
Current methods for producing low-cost magnetic field sensor bridges using standard semiconductor processes are limited, particularly for MTJ and GMR sensors, as they require complex manufacturing techniques and high costs due to the difficulty in aligning pinned layer magnetization directions and achieving temperature compensation.
Innovation Solution
A single-chip half-bridge or full-bridge magnetic field sensor design where all magnetoresistive elements have their pinned layer magnetization aligned in the same direction, with the free layer magnetization of opposite polarity between adjacent elements, utilizing integrated magnets or current to bias the free layer, and employing Neel-coupling or antiferromagnetic coupling for biasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a bridge magnetic field sensor is integrated into a semiconductor chip, then the miniaturization and integration of the sensor is improved, but the sensor output signal becomes unstable and contains large offsets
Solution Approach 1:
The semiconductor substrate is divided into multiple doped regions including first doped regions, second doped regions, third doped regions, and fourth doped regions. These segmented regions form complementary bridge structures that separately sense magnetic field components and compensate for each other's deficiencies, thereby maintaining signal stability in a miniaturized configuration.
Solution Approach 2:
The patent employs composite doped structures combining different doping types (n-type and p-type) and doping concentrations to create bridge structures with complementary characteristics. This composite approach enables the miniaturized sensor to maintain stable output signals by leveraging the complementary properties of different doped regions.
2Area of stationary object
If the sensor structure is miniaturized for integration, then the chip area is reduced, but the offset voltage increases and signal stability deteriorates
Solution Approach 1:
Different regions of the chip are doped with different types and concentrations of dopants to create local quality variations. The first and second doped regions have different doping characteristics from the third and fourth doped regions, enabling each local area to contribute specifically to offset compensation and signal stabilization within the miniaturized chip structure.
Solution Approach 2:
The patent utilizes parameter changes in doping concentration and doping type across different regions to control and compensate for offset voltages. By adjusting these doping parameters locally, the miniaturized sensor achieves stable output signals despite the reduced chip area.
3Device complexity
If conventional sensor integration methods are used, then manufacturing complexity is reduced, but the signal-to-noise ratio decreases due to large offsets
Solution Approach 1:
The patent merges the sensing function and the compensation function into a single integrated bridge structure on the semiconductor chip. The complementary bridge structures combine multiple doped regions that simultaneously perform magnetic field sensing and offset compensation, achieving improved signal-to-noise ratio without significantly increasing integration complexity.
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 design simplifies the manufacturing process, reduces costs, and maintains high sensitivity and temperature stability, eliminating the need for multi-chip packaging and exotic techniques like local laser heating, while ensuring effective temperature compensation and performance matching.
Implementation Method 1
a first doped region and a second doped region are formed in a semiconductor substrate, the first doped region and the second doped region form a bridge structure
Data Source
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AI summary
The present invention discloses a design and manufacturing method for a single-chip magnetic sensor bridge. The sensor bridge comprises four magnetoresistive elements. The magnetization of the pinned layer of each of the four magnetoresistive elements is set in the same direction, but the magnetization directions of the free layers of the magnetoresistive elements on adjacent arms of the bridge are set at different angles with respect to the pinned layer magnetization direction. The absolute values of the angles of the magnetization directions of the free layers of all four magnetoresistive elements are the same with respect with their pinning layers. The disclosed magnetic biasing scheme enables the integration of a push-pull Wheatstone bridge magnetic field sensor on a single chip with better performance, lower cost, and easier manufacturability than conventional magnetoresistive sensor designs.