Capacitive Pressure Sensor with Monocrystalline Cavity
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Solution Overview
Problem
Existing pressure sensors using piezoresistive measuring techniques are temperature-dependent and power-consuming, limiting the effectiveness of capacitive measuring techniques with tight cavities.
Innovation Solution
A pressure sensor design featuring a capacitive measuring technique with a tight, monocrystalline cavity and substrates having through holes for communication with the surrounding environment, allowing for deformation-based pressure measurement while preventing gas leakage and using semiconductor materials for durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoresistive measuring techniques are used with monocrystalline cavity designs, then measurement capability is achieved, but temperature dependence and power consumption increase
Solution Approach 1:
The patent replaces the piezoresistive measuring technique with a capacitive measuring technique. Instead of using piezoresistive elements that convert mechanical stress directly to electrical resistance changes, the invention uses a capacitive sensor where the membrane deformation changes the capacitance between two electrodes. This substitution eliminates the need for power-consuming piezoresistive heating and reduces temperature dependence while maintaining pressure measurement capability.
2Reliability
If a tight monocrystalline cavity is used, then long-term stability is improved by preventing gas leakage, but manufacturing complexity increases
Solution Approach 1:
The patent implements a nested structure where the membrane is formed by an epitaxial layer that grows over and encapsulates the cavity opening. The cavity is formed within the substrate, and the epitaxial layer is deposited to seal the cavity, creating a nested configuration where one structure (epitaxial layer) encloses another (cavity). This nested approach achieves a tight seal preventing gas leakage while using standard semiconductor manufacturing processes.
Solution Approach 2:
The patent utilizes parameter changes in the manufacturing process, specifically employing epitaxial growth parameters to form the sealing membrane. By controlling the epitaxial layer formation parameters (temperature, pressure, gas flow), the cavity is effectively sealed. This parameter-based approach transforms the manufacturing process into a more controllable and less complex procedure while achieving the desired tight cavity seal.
3Measurement precision
If through holes are added to enable gap communication with surrounding, then pressure sensing accuracy is improved, but cavity sealing reliability may worsen
Solution Approach 1:
The patent segments the substrate into distinct functional regions using through holes. The through holes are strategically positioned to separate the cavity region from the surrounding substrate, creating isolated zones. This segmentation allows the cavity to remain sealed while the through holes provide controlled access pathways for pressure equalization between the gap and the surrounding environment, thus maintaining both sealing integrity and pressure sensing accuracy.
Data Source
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AI summary
The Invention relates to a pressure sensor for sensing a pressure, comprising: a first substrate (1) comprising a cavity (41) and a deformable membrane (42) that is configured to be deformed by a pressure acting on the membrane (42), wherein said membrane separates said cavity (41) from a gap (6) of the pressure sensor (P), which gap (6) communicates with a surrounding (S) of the pressure sensor (P) so that the pressure in said gap (6) corresponds to the pressure in said surrounding (S), a first electrode (43) comprised or formed by said membrane (42), wherein the first electrode (43) is moveable with the membrane (42), and a stationary second electrode (243) (particularly arranged on a second substrate (2)) which second electrode (243) faces said first electrode (43), wherein said gap (6) is arranged between the second electrode (243) and said membrane (42) comprising the first electrode (43), so that a distance (D) between the first electrode (43) and the second electrode (243) depends on the pressure in said gap (6). Further, the invention relates to a method for producing a pressure sensor (P).