Semiconductor Magnetic Field Sensor With Biased Gate Terminals
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Solution Overview
Problem
Semiconductor magnetic field sensors suffer from imperfections such as material asymmetries and low sensitivity due to fabrication issues, leading to offset and reduced accuracy in detecting magnetic fields.
Innovation Solution
A semiconductor magnetic field sensor design featuring a semiconductor well with MOS structures and heavily doped contact regions, which enhances current deflection perpendicular to the sensor plane, improving sensitivity by preventing leakage currents and material imperfections through proper biasing of gate terminals and PN junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Shallow Trench Isolations (STI) are used to isolate semiconductor device components, then current leakage between adjacent components is prevented, but material asymmetries are introduced causing offset in detection
Solution Approach 1:
The patent extracts and removes the STI isolation structures from the sensor design. By eliminating these isolations, the source of material asymmetries and detection offset is removed, while the sensor maintains proper current isolation through its inherent symmetric structure and substrate connections.
Solution Approach 2:
The patent addresses the asymmetry introduced by STI by designing a completely symmetric sensor structure. The symmetric arrangement of collectors, emitters, and base regions ensures that no preferential direction or material asymmetry exists, thereby eliminating detection offset while maintaining reliability.
2Ease of manufacture
If lateral semiconductor magnetic field sensors are fabricated with conventional structures, then manufacturing is simplified, but sensitivity is reduced due to parasitic current loss through lightly doped substrate
Solution Approach 1:
The patent moves the current paths into the vertical dimension by having currents flow perpendicular to the substrate surface through heavily doped contact regions. This dimensional change prevents parasitic current loss through the lightly doped substrate while maintaining lateral sensor geometry for easy manufacturing.
Solution Approach 2:
The patent changes the doping parameter of the contact regions to heavily doped, which creates low-resistance paths for current flow. This parameter change reduces parasitic current loss and improves sensitivity while maintaining compatibility with conventional fabrication processes.
3Manufacturing precision
If material asymmetries are present in fabrication, then manufacturing tolerances are relaxed, but offset in magnetic field detection increases
Solution Approach 1:
The patent employs symmetric design principles where all critical components (collectors, emitters, base regions) are arranged symmetrically. This symmetry ensures that even if material asymmetries exist due to relaxed manufacturing tolerances, their effects cancel out, preventing detection offset.
Solution Approach 2:
The patent uses homogeneous doping concentrations and geometric dimensions for corresponding components throughout the sensor structure. This homogeneity ensures uniform electrical properties and symmetric current distribution, making the sensor insensitive to variations within relaxed manufacturing tolerances.
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 increases the sensitivity and accuracy of magnetic field detection by effectively deflecting currents perpendicular to the sensor plane, reducing the impact of material imperfections and leakage currents, thereby enhancing the response to applied magnetic fields.
Implementation Method 1
wherein, in operation, the first gate terminal and the second gate terminal are biased for increasing a deflection length of a first current and a second current, wherein the deflection length is perpendicular to a plane defined by a surface of the semiconductor magnetic field sensor and parallel to a magnetic field
Implementation Method 2
an insulation layer between the substrate layer and the semiconductor well
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
A semiconductor magnetic field sensor includes a semiconductor well (PW) on top of a semiconductor layer (Pepi). An insulation layer (ISO2) is located between the semiconductor layer (Pepi) and the substrate (SUB). The semiconductor well (PW) contains a lateral NPN bipolar magnetotransistor having two base contact regions (5) and (10) contacting the semiconductor well (PW). The semiconductor well (PW) further comprises two heavily n-type doped regions acting as collector regions (20) and (25) for the lateral NPN bipolar magnetotransistor. The semiconductor well (PW) further comprises a heavily doped n-type region acting as an emitter region (15) for the lateral NPN bipolar magnetotransistor and placed in between the two collector regions (20) and (25). A first MOS structure, having a first gate terminal (G1), is located between the first collector region (20) and the emitter region (15). A second MOS structure, having a second gate terminal (G2), is located between the emitter region (15) and the second collector region (25). By having the emitter region (15) placed between the first and the second collector regions (20) and (25), and by having properly biased MOS structures between the emitter region (15) and the collector regions (20) and (25), a first and a second collector current flowing in the semiconductor well (PW) generated during operation of the semiconductor magnetic field sensor are deflected down in a perpendicular direction from a plane defined by a surface (S) of the semiconductor magnetic field sensor and parallel to a direction of the magnetic field (Bx). The increase of the effective vertical deflection (Leff) of the collector currents enhances the response of the semiconductor magnetic field sensor to an applied magnetic field (Bx) for a given emitter input bias current thus sensing with better accuracy also small values of the applied magnetic field (Bx). Furthermore the use of MOS structures ensures clean interfaces between the emitter region (15), the collector regions (20) and (25) and the MOS structures, avoiding the formation of material imperfections, defects, or interface states that cause an imbalance in the first and the second collector currents even in absence of a magnetic field (Bx).