Capacitive Pressure Sensor with Integrated Reference Chamber
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Solution Overview
Problem
Piezo-resistive pressure sensors are susceptible to changes in ambient temperature, leading to deviations in detection precision, and their 3D structure with bonded substrates results in high costs and increased size.
Innovation Solution
A capacitive pressure sensor with a reference pressure chamber formed within a single semiconductor substrate, featuring a diaphragm with ring-like and central through holes, and insulating layers to form a capacitor structure that detects pressure changes in capacitance without relying on piezo-resistive elements, thus minimizing temperature effects and eliminating the need for substrate bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezo-resistive element is used for pressure detection, then the pressure sensor can detect pressure through resistance variation, but the detection precision deviates under varying ambient temperature
Solution Approach 1:
The patent replaces the piezo-resistive detection mechanism with a capacitive detection mechanism. Instead of measuring resistance changes in a piezo-resistive element, the invention uses a capacitive sensor that measures capacitance changes between a diaphragm and a reference electrode. This substitution eliminates temperature sensitivity because capacitive measurements are not affected by temperature variations, thereby resolving the contradiction between measurement precision and temperature sensitivity.
Solution Approach 2:
The patent changes the detection parameter from electrical resistance to electrical capacitance. By measuring capacitance changes rather than resistance changes, the system achieves temperature-independent pressure detection. The capacitance between the diaphragm and reference electrode varies with pressure-induced diaphragm displacement, providing accurate pressure measurement without temperature interference.
2Reliability
If a 3D structure with at least two substrates bonded to each other is used, then the pressure sensor can be formed with a reference pressure chamber, but the costs increase and the size increases
Solution Approach 1:
The patent merges the reference pressure chamber formation process into a single substrate manufacturing step. Instead of bonding separate substrates to create the reference pressure chamber, the invention forms the reference pressure chamber directly within a single substrate using standard semiconductor fabrication techniques. This integration eliminates the need for substrate bonding, reducing device complexity and manufacturing costs while maintaining the reliability of the reference pressure chamber.
Solution Approach 2:
The patent extracts the reference pressure chamber formation from the multi-substrate bonding process and implements it as an integrated feature within a single substrate. By taking out the bonding step and incorporating the reference chamber directly into the substrate structure, the invention simplifies the overall device architecture, reduces manufacturing complexity, and lowers costs while preserving the functional reliability of the reference pressure chamber.
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 reduces detection precision deviations, lowers costs, and downsizes the pressure sensor by eliminating the need for substrate bonding and using temperature-sensitive piezo-resistive elements, while maintaining high detection precision and simplicity in manufacturing.
Implementation Method 1
a capacitor structure can be formed by the upper electrode and the opposing rear surface (lower electrode) of the semiconductor substrate with the reference pressure chamber (cavity) interposed therebetween. When the diaphragm is subjected to a pressure, the diaphragm is deformed due to a difference in pressure between the interior and exterior of the reference pressure chamber, thereby changing a distance between the upper electrode and the lower electrode. As a result, a capacitance between the upper electrode and the lower electrode is changed. The pressure applied to the diaphragm can be detected by detecting the change in capacitance.
Data Source
AI summary
A capacitive pressure sensor includes: a semiconductor substrate having a reference pressure chamber formed therein; a diaphragm which is formed in a front surface of the semiconductor substrate and has a ring-like peripheral through hole penetrating between the front surface of the semiconductor substrate and the reference pressure chamber and defining an upper electrode and a plurality of central through holes; a peripheral insulating layer which fills the peripheral through hole and electrically isolates the upper electrode from other portions of the semiconductor substrate; and a central insulating layer which fills the central through holes.