Hall Sensor Deep Trench Isolation for JFET Effect Reduction
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Solution Overview
Problem
Conventional Hall effect sensors experience instability and variations in magnetic gain and offset due to the JFET effect caused by common mode feedback regulation, which modulates the terminal voltages and affects the depletion regions, leading to temperature-dependent drift and manufacturing inconsistencies.
Innovation Solution
The implementation of deep trench isolation structures to isolate the p-type layer within the Hall element, ensuring that the p-type layer is coupled to the lowest potential terminal, thereby maintaining a constant depletion region depth and reducing variations in resistance and offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common mode feedback regulation is used to stabilize the Hall voltage, then temperature-dependent drift is reduced, but the JFET effect causes variability in magnetic gain and offset
Solution Approach 1:
The patent divides the Hall element into distinct regions: an active region for Hall effect measurement and a separate p-type layer for potential control. This segmentation allows independent optimization of each region's function, preventing the p-type layer from interfering with the Hall voltage measurement while maintaining stability.
Solution Approach 2:
The patent extracts and isolates the p-type layer from the active Hall measurement region by introducing deep trench isolation structures. This separation removes the source of the JFET effect (the p-type layer) from the active region, eliminating its harmful influence on magnetic gain and offset while preserving the common mode feedback regulation benefits.
2Device complexity
If the p-type layer is not isolated, then the Hall element structure is simple, but the depletion region depth varies causing offset drift
Solution Approach 1:
The patent introduces a vertical dimension to the isolation structure by implementing deep trenches that extend through the substrate. This three-dimensional isolation approach effectively separates the p-type layer from the active region in the vertical direction, maintaining structural simplicity on the surface while achieving precise offset stability through deep isolation.
3Manufacturing precision
If deep trench isolation is implemented to eliminate JFET effect, then magnetic gain variability is reduced, but device complexity increases
Solution Approach 1:
The patent applies local quality by implementing deep trench isolation only in specific locations where the p-type layer interfaces with the active region. Rather than isolating the entire structure, the trenches are strategically placed at critical interfaces, providing precise control where needed while maintaining simplicity elsewhere in the device.
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 significantly reduces the variability in magnetic gain and offset by eliminating the JFET effect, providing stable performance across temperature and manufacturing variations.
Implementation Method 1
In the presence of a magnetic field orthogonal to the direction of current through Hall element 100, in this example into or out of the page of FIG. 1, the Lorentz force acts on the majority carriers in the semiconductor material of Hall element 100 (e.g., electrons in n-type silicon) to produce a 'Hall voltage,' namely the differential of voltages VH+ and VH− at terminals T2 and T4, respectively.
Implementation Method 2
This common mode feedback circuit includes amplifier 150, which receives a common mode reference voltage VCM generated by reference voltage circuit 152 at a negative input. Amplifier 150 is configured to produce an output signal corresponding to the difference between the common mode voltage of terminals T2 and T4 and common mode reference voltage VCM from reference voltage circuit 152. This output signal is applied as a control signal to current source 126 so that the common mode voltage at terminals T2 and T4 matches common mode reference voltage VCM, regardless of manufacturing and temperature variations in Hall effect sensor 110.
Implementation Method 3
The implementation of deep trench isolation structures to isolate the p-type layer within the Hall element, ensuring that the p-type layer is coupled to the lowest potential terminal, thereby maintaining a constant depletion region depth and reducing variations in resistance and offset.
Data Source
AI summary
A Hall effect sensor including a Hall element disposed at a surface of a semiconductor body, including a first doped region of a first conductivity type disposed over and abutted by an isolated second doped region of a second conductivity type. First through fourth terminals of the Hall element are in electrical contact with the first doped region, and a fifth terminal in electrical contact with the second doped region. A Hall effect sensor includes a first current source coupled to the first terminal of the Hall element, and common mode feedback regulation circuitry. The common mode feedback regulation circuitry has an output coupled to the third terminal and a ground node, and having an input coupled to the second and fourth terminals of the Hall element, and an output coupled to the third terminal and a ground node, where the second doped region is coupled to the third terminal.