Capacitive Pressure Sensor Segmented Electrode Design
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Solution Overview
Problem
Differential pressure sensors with one-piece conductive base bodies suffer from low measurement accuracy due to the large outer electrode area, leading to small differential capacitance changes and non-linear pressure measurement dependencies, and their complex production processes.
Innovation Solution
The design incorporates a recess on the base body with a conductive coating and electrode connections on lateral surfaces, allowing for a simpler construction with one-piece base bodies and improved mechanical stability, while maintaining measurement accuracy through precise layer thickness control and wire bonding connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one-piece conductive base bodies are used as electrodes, then the construction is simpler and mechanical stability is improved, but measurement accuracy deteriorates due to large outer electrode area causing small differential capacitance changes
Solution Approach 1:
The base body is segmented into multiple functional layers: a first base body layer, an insulating layer, and a second base body layer. The electrode is segmented into an inner electrode area and an outer electrode area, with the outer area connected to the measuring membrane edge. This segmentation allows the simple one-piece construction to maintain both mechanical stability and measurement accuracy by separating the electrode into functional zones.
Solution Approach 2:
Different areas of the electrode are given different electrical connections and functions. The inner electrode area is electrically isolated and forms the measurement capacitor, while the outer electrode area is connected to the measuring membrane edge and serves as a reference. This local differentiation of electrical properties allows the large electrode area to not degrade measurement precision.
2Ease of manufacture
If one-piece conductive base bodies with large electrode area are used, then manufacturing is simpler, but measurement accuracy deteriorates due to non-linear pressure measurement dependency
Solution Approach 1:
The electrode is divided into inner and outer areas with different electrical connections. The inner electrode area forms the measurement capacitor with the measuring membrane, while the outer electrode area is connected to the measuring membrane edge. This segmentation enables the capacitance change to be primarily determined by the inner area's deflection, improving linearity while maintaining simple one-piece base body construction.
Solution Approach 2:
The insulating layer acts as an intermediary between the first base body layer and the second base body layer, allowing electrical isolation of the inner electrode area while maintaining mechanical structural integrity. This enables the simple one-piece construction to achieve the complex electrical configuration needed for linear pressure measurement.
3Measurement precision
If multi-layer base body structures with trenches are used, then measurement accuracy is improved, but production complexity increases
Solution Approach 1:
Instead of creating trenches in the base body to separate electrode areas (as in prior art), the patent inverts the approach by using layers applied to the base body surface. The insulating layer and conductive coating are applied in sequence to create the electrode structure, eliminating the need for complex trench structuring while achieving the same electrical separation.
Solution Approach 2:
The mechanical trench structure is replaced by applied functional layers. Rather than physically cutting or structuring the base body to create electrode separation, the patent uses deposited insulating and conductive layers to achieve the same electrical isolation, simplifying the mechanical structure while maintaining measurement accuracy.
4Measurement precision
If multi-layer base body structures are used, then measurement accuracy is improved, but production complexity and manufacturing difficulty increase
Solution Approach 1:
Complex mechanical structuring processes (trenches, multiple base body layers) are replaced by standard semiconductor deposition processes. The insulating layer is applied by oxidation or deposition, and the conductive coating is applied by sputtering or CVD, using well-established wafer-level manufacturing techniques that simplify production.
Solution Approach 2:
The patent changes the manufacturing parameters from mechanical structuring to material deposition. By controlling layer thicknesses (insulating layer 1-10 μm, conductive coating 0.1-10 μm) and using standard deposition processes, the patent achieves the required electrical isolation and electrode configuration through material properties rather than complex mechanical structures.
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 enables accurate differential pressure measurement without the need for complex multi-layer base body structures, enhancing mechanical stability and reducing production complexity, while maintaining measurement precision.
Implementation Method 1
forms a capacitor with a capacity that varies as a function of a deflection of the measuring membrane that is dependent on the pressure acting on the measuring membrane
Implementation Method 2
capacitive electromechanical converter, which detects a deflection of the measuring membrane that is dependent on the pressure acting on the measuring membrane, and converts it into an electrical signal
Data Source
Figure 1~3
Figure 4~5
Figure 6a~6h
AI summary
The invention relates to a pressure sensor which has a simple structure and is economical to produce using a method according to the invention. The pressure sensor has a main part (1), an electrically conductive measurement membrane (5) to which a pressure (Δρ) can be applied and which is connected to the main part (1) such that it encloses a pressure chamber (3), and an electrode (13), which is spaced apart from the measurement membrane (5) and electrically insulated from said measurement membrane (5). Together with the measurement membrane (5) the electrode forms a capacitor, the capacitance of which can vary with a deflection of the measurement membrane (5) that depends on a pressure (Δρ) acting on said measurement membrane (5). The pressure sensor is characterized in that the main part (1) has an inner surface which delimits the pressure chamber (3) and is opposite the measurement membrane (5), an insulating layer (15), in particular an insulating layer (15) made of silicon dioxide (SiO2) being applied to the inner surface, and the electrode (13) being a conductive coating, especially a coating of doped polysilicon, applied to the insulating layer (15) on the inner surface.