Wide Cross Hall Effect Element for Sensitivity and Resistance Trade-off
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Solution Overview
Problem
Hall effect magnetic field sensing elements face challenges in achieving a balance between area size, sensitivity, resistance, and response time, with conventional square elements offering high sensitivity but high resistance, and cross-shaped elements providing lower capacitance and faster response but reduced sensitivity.
Innovation Solution
A Hall effect element with a unique shape, featuring a 'wide cross' perimeter and electrical contact arrangement, optimized for a substrate with a selected Miller index, which reduces area while maintaining high sensitivity and low resistance, and minimizing offset voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional square Hall effect element is used, then high sensitivity is achieved, but high resistance occurs between opposing electrical contacts
Solution Approach 1:
The Hall plate is segmented into a cross-shaped configuration with four arms extending from a central region. This segmentation creates multiple current paths between opposing electrical contacts, effectively reducing the overall resistance while maintaining the sensing area for high sensitivity magnetic field detection.
Solution Approach 2:
The design transitions from a two-dimensional square planar structure to a cross-shaped structure that effectively utilizes dimensional optimization. By extending arms in perpendicular directions and optimizing the aspect ratio of the arms, the design achieves lower resistance through increased effective conduction paths while maintaining sensitivity through optimized active sensing regions.
2Speed
If a cross-shaped Hall effect element is used, then lower capacitance and faster response time are achieved, but sensitivity is reduced
Solution Approach 1:
Different regions of the Hall plate are optimized for different functions: the central region and arm structures are designed with specific aspect ratios to minimize capacitance and reduce response time, while the active sensing regions at the ends of the arms are optimized to maintain high sensitivity for magnetic field detection.
Solution Approach 2:
The design optimizes specific geometric parameters including the aspect ratio of the cross arms (with longest sides parallel and orthogonal to the <011> direction), the dimensions of the central core region, and the spacing between arms. These parameter optimizations simultaneously achieve lower capacitance for faster response while maintaining sufficient sensing area for high sensitivity.
3Area of stationary object
If the Hall effect element size is reduced, then area is minimized, but offset voltages increase
Solution Approach 1:
The cross-shaped design introduces controlled asymmetry in the form of four distinct arms with specific orientation relative to the substrate crystallographic directions. This asymmetric configuration, with arms aligned parallel and orthogonal to the <011> direction, helps cancel out offset voltages through geometric compensation while maintaining a compact area.
Solution Approach 2:
The symmetric cross configuration with arms of equal length and identical geometry relative to the substrate orientation creates equipotential conditions that balance out offset voltages. The geometric symmetry ensures that offset errors generated in one arm are compensated by equal and opposite effects from other arms, minimizing net offset voltage despite reduced overall area.
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 achieves superior performance characteristics, including high sensitivity and low resistance, resulting in a higher signal-to-noise ratio and faster operation, while avoiding the limitations of smaller sizes that increase offset voltages.
Implementation Method 1
Hall effect magnetic field sensing elements are known. As is known, a Hall effect element includes a so-called 'Hall plate,' which is most often an epi region (i.e., layer) upon a substrate.
Data Source
AI summary
A Hall effect element includes a Hall plate having geometric features selected to result in a highest ratio of a sensitivity divided by a plate resistance. The resulting shape is a so-called “wide-cross” shape.