Vertical Hall Effect Sensor Retrograde Dopant Profile
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Solution Overview
Problem
Existing vertical Hall effect sensors face challenges in achieving high output and linearity in detecting magnetic fields, particularly due to limitations in current flow depth and dopant profiles in semiconductor wafers.
Innovation Solution
The design incorporates a semiconductor wafer with interdigitated vertical Hall effect sensors featuring electrically floating semiconductor fingers and N-type blankets with higher charge carrier density, along with a retrograde dopant profile, to enhance current flow depth and linearity of signal output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional vertical Hall effect sensors are used with standard dopant profiles, then the device structure is simple, but the current flow depth is limited and signal output is reduced
Solution Approach 1:
The patent applies local quality by implementing a retrograde dopant profile where the doping concentration varies with depth - higher at the surface and lower at deeper regions. This localized variation in dopant concentration optimizes the current flow path, allowing deeper current penetration while maintaining high signal output at the sensing electrodes, thereby resolving the contradiction between signal output and structural simplicity.
Solution Approach 2:
The patent changes the dopant concentration parameter as a function of depth, creating a retrograde profile instead of a uniform or conventional gradient profile. This parameter change enables deeper current flow paths while maintaining sufficient carrier density at the surface for strong signal generation, thus improving signal output without requiring fundamentally more complex device structures.
2Length of stationary object
If the semiconductor wafer thickness is increased to allow deeper current flow, then current flow depth improves, but the device dimensions and manufacturing complexity increase
Solution Approach 1:
Rather than uniformly increasing wafer thickness, the patent uses local quality by varying the dopant concentration at different depths. The retrograde profile creates regions of high and low carrier density at specific depths, guiding current flow to penetrate deeper into the wafer without requiring the entire wafer to be thicker, thus avoiding increased manufacturing complexity while achieving deeper current flow.
Solution Approach 2:
The patent addresses the depth limitation by transitioning from a two-dimensional surface-based sensing approach to a three-dimensional current flow path controlled by depth-varying dopant profiles. The retrograde dopant profile creates vertical current flow components that penetrate deeper into the wafer thickness direction, enabling deeper current flow without increasing the lateral dimensions or overall wafer thickness.
3Measurement precision
If multiple Hall effect sensors are placed on a single substrate to improve detection accuracy, then measurement precision improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies segmentation by dividing the sensing function across multiple interdigitated electrode pairs (source, sense, and drain electrodes arranged in alternating pattern) on a single wafer. Each electrode pair functions as an independent sensing element, and their combined outputs provide enhanced measurement precision through differential sensing, while maintaining a unified fabrication process that avoids the complexity of assembling separate sensor devices.
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 configuration results in increased signal levels and improved linearity, allowing for more accurate and precise measurements of magnetic fields, as demonstrated by the deeper current flow and enhanced output characteristics.
Implementation Method 1
The Hall effect is a phenomenon whereby moving charged particles are deflected by a magnetic field within a charge carrier. This phenomenon has been put to practical use in Hall effect sensors utilizing a current through a semiconductor.
Implementation Method 2
The width of each electrically floating semiconductor finger is between 5% and 12% of the semiconductor wafer thickness. The first depth is less than a depth of depletion regions beneath the semiconductor fingers.
Data Source
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AI summary
In one aspect, a vertical Hall effect sensor (14) includes a semiconductor wafer (12) having a first conductivity type and a plurality of semiconductive electrodes (118,120A,120B,122A,122B) disposed on the semiconductor wafer. The plurality of semiconductive electrodes have the first conductivity type and include a source electrode (118), a first sensing electrode (120A) and a second sensing electrode (120B), arranged such that the source electrode is between the first sensing electrode and the second sensing electrode and a first drain electrode (122A) and a second drain electrode (122B), arranged such that the first sensing electrode, second sensing electrode, and source electrode are between the first drain electrode and the second drain electrode. The vertical Hall effect sensor also includes a plurality of semiconductor fingers (124A,124B,124C,124D) disposed on the semiconductor wafer and interdigitated with the plurality of semiconductive electrodes, the semiconductor fingers having a second conductivity type.