Vertical Hall Sensor Offset Reduction via Segmented Symmetry
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Solution Overview
Problem
Vertical Hall Effect sensors face challenges in accurately measuring magnetic fields parallel to the chip surface due to voltage offset caused by fabrication imperfections and environmental conditions, which complicates the use of the spinning current technique for offset compensation, especially in asymmetric devices.
Innovation Solution
A vertically symmetric Hall Effect sensor design with a specific arrangement of contacts and conductive regions, allowing for minimal spacing between inner contacts, enabling effective offset compensation and high sensitivity through a spinning current scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear arrangement of four contacts is used in a vertical Hall Effect device, then a high degree of symmetry between bias modes is achieved which allows the spinning current technique to cancel offset, but a large pre-spinning systematic offset is exhibited which degrades the signal to noise ratio
Solution Approach 1:
The device is segmented into multiple conductive regions (first conductive region, second conductive region, third conductive region, fourth conductive region) with specific contact arrangements. This segmentation allows different regions to contribute differently to the overall symmetry and offset characteristics, enabling both high symmetry for offset cancellation and reduced pre-spinning offset through optimized regional contributions.
Solution Approach 2:
Different conductive regions are assigned specific properties and contact configurations. The first and second conductive regions have different spacing characteristics compared to the third and fourth regions. This local quality differentiation allows the device to achieve both high overall symmetry and minimized systematic offset by optimizing each region's contribution.
2Object-affected harmful factors
If five or six contacts are used in a linear arrangement to reduce pre-spinning offset voltage, then the offset is reduced, but the device becomes highly asymmetric between bias modes which results in the ineffectiveness of the spinning current technique to cancel offset
Solution Approach 1:
The invention deliberately introduces asymmetric elements (different spacing in different conductive regions) to achieve a symmetric overall response. By making the asymmetric spacing systematic and controlled, the device achieves both reduced pre-spinning offset and maintained symmetry between bias modes, resolving the contradiction between these two requirements.
Solution Approach 2:
The spacing parameters between contacts are optimized to achieve the desired balance. Specifically, the spacing between first and second contacts differs from the spacing between third and fourth contacts, with at least one spacing being less than 5 micrometers. This parameter optimization enables both offset reduction and symmetry maintenance.
3Measurement precision
If adequate spacing between contacts is provided to achieve nominally zero offset and maximum sensitivity, then optimal sensor performance is achieved, but deeper wells are required which increase sensor size
Solution Approach 1:
The invention transitions from a simple linear arrangement to a multi-dimensional conductive region structure. By arranging contacts and conductive regions in a complex geometric pattern rather than a simple line, the device achieves adequate effective spacing for optimal performance while maintaining a compact footprint, thus reducing the required well depth and sensor size.
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 design achieves optimal performance in terms of offset reduction and sensitivity, maintaining a high degree of symmetry between bias modes and minimizing systematic offset, thereby improving the signal-to-noise ratio and dynamic range.
Implementation Method 1
In the presence of a magnetic field, the carriers that are moving along the path are deflected by a Lorentz force and a Hall electric field is formed.
Implementation Method 2
Hall Effect devices are used in sensor applications for contactless sensing of magnetic fields.
Data Source
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AI summary
A vertical Hall Effect sensor is provided having a high degree of symmetry between its bias modes, can be adapted to exhibit a small pre-spinning systematic offset, and complies with the minimal spacing requirements allowed by the manufacturing technology (e.g., CMOS) between the inner contacts. These characteristics enable the vertical Hall Effect sensor to have optimal performance with regard to offset and sensitivity.