Capacitive Differential Pressure Sensor Trench Segmentation
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Solution Overview
Problem
Capacitive differential pressure sensors with one-piece base bodies suffer from low measurement accuracy due to the large outer partial capacitor area, which affects the sensitivity and linearity of pressure measurements, especially in semiconductor sensors with square base areas.
Innovation Solution
A differential pressure sensor design featuring a conductive disk divided by a trench into an inner region serving as an electrode and an outer region electrically insulated from it, with the inner area forming capacitors that are sensitive to differential pressure, and the trench minimizing the outer partial capacitor area, allowing for higher measurement accuracy and simpler production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If one-piece base bodies are used as counter-electrodes with a large electrode area, then the device structure is simple and manufacturing is easier, but the measurement precision deteriorates due to the large outer partial capacitor area reducing the proportion of differential pressure-dependent capacitance change
Solution Approach 1:
The electrode area is segmented into an inner area and an outer area by introducing a trench. The inner area forms the measuring capacitor sensitive to differential pressure, while the outer area forms a reference capacitor that is compensated. This segmentation allows the measuring capacitor to have a smaller effective area, increasing the proportion of its capacitance change in the total measurement, thereby improving measurement precision while maintaining a simple one-piece base body structure for ease of manufacture.
2Measurement precision
If the electrode area is reduced to increase measurement sensitivity, then the measurement precision improves, but the manufacturing complexity increases due to the need for additional structuring steps
Solution Approach 1:
The electrode is segmented into inner and outer areas using a trench structure. This segmentation reduces the effective measuring electrode area to increase sensitivity and measurement precision, while the trench itself is integrated into the base body structure rather than requiring separate complex assembly steps, thus limiting the increase in device complexity.
Solution Approach 2:
The geometry parameters of the electrode (area, shape, position) are optimized by defining the trench dimensions and depth. By adjusting these parameters, the electrode area is reduced to achieve the desired measurement precision, while the changes are implemented through standard fabrication process parameters rather than fundamentally changing the device architecture.
3Measurement precision
If a trench is introduced to divide the electrode into inner and outer areas, then the measurement precision improves by increasing the proportion of differential pressure-dependent capacitance, but the device complexity increases due to additional structuring requirements
Solution Approach 1:
A trench is introduced to segment the electrode into inner and outer areas. The inner area forms the measuring capacitor with higher differential pressure sensitivity, while the outer area forms the reference capacitor. This segmentation improves measurement precision by increasing the proportion of the measuring capacitor's capacitance change in the total signal, while the trench is designed to be integrated into the base body structure to minimize additional complexity.
Solution Approach 2:
The trench parameters (width, depth, position) are optimized to achieve the desired electrode area reduction and sensitivity improvement. By controlling these geometric parameters within standard fabrication capabilities, the measurement precision is enhanced without requiring fundamentally complex device structures or additional manufacturing process categories.
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 significantly increases the proportion of partial capacitance change relative to the total capacitance, enhancing measurement accuracy and allowing for cost-effective production with flexible geometry selection, including square base areas for wafer assembly advantages.
Implementation Method 1
the resulting deflection of the measuring diaphragm, which is dependent on the difference between the two pressures, is recorded by means of a capacitive electromechanical converter and converted into an electrical signal
Implementation Method 2
Semiconductor sensors regularly have measuring membranes made of silicon, which can be used directly as the electrode of the capacitive converter due to their conductivity
Data Source
Figure 1~2e
Figure 3a~3g
Figure 4
AI summary
A differential pressure sensor which is of simple design and can be produced cost-effectively is described, comprising a first and a second counterelectrode (1, 3), a conductive plate (5) arranged between the two counterelectrodes (1, 3), a first insulating layer (7), via which an outer edge of the plate (5) is connected to an outer edge of the first counterelectrode (1) to form a first pressure chamber (9), a second insulating layer (11), via which an outer edge of the plate (5) is connected to an outer edge of the second counterelectrode (3) to form a second pressure chamber (9), a cutout (13) which is provided in the first counterelectrode (1) and via which a first pressure (p1) can be applied to the first pressure chamber (9), and a cutout (13) which is provided in the second counterelectrode (3) and via which a second pressure (p2) can be applied to the second pressure chamber (9), which sensor is distinguished by the fact that the plate (5) is subdivided by a trench (17) into an inner region (19) serving as electrode and an outer region (21) electrically insulated therefrom by the trench (17), the inner region (19) comprises a measuring membrane (15) arranged between the two pressure chambers (9) and an edge region (23) enclosing the measuring membrane (15) and clamped in between the inner edges (25) of the insulating layers (7, 11), and the inner region (19) forms with each of the counterelectrodes (1, 3) in each case a capacitor having a capacitance (C1, C3) dependent on a differential pressure (Δρ) acting on the measuring membrane (15).