MEMS Chip With Dual Plate Capacitors for Linear Distortion
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Solution Overview
Problem
Traditional MEMS chips with a single back-electrode structure exhibit low linearity, high harmonic distortion, and adhesion issues between the diaphragm and back electrode, affecting performance, particularly during vibration and drop tests.
Innovation Solution
A MEMS chip design featuring dual plate capacitor structures with diaphragms and back electrodes, incorporating air leakage structures and restraining portions to mitigate distortion, prevent adhesion, and enhance equipotential connections to improve performance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single back-electrode structure is used, then the device complexity is low, but the linearity is poor and harmonic distortion is high
Solution Approach 1:
The patent divides the single back-electrode structure into multiple back-electrode segments (first back electrode, second back electrode, third back electrode) with different capacitance values. This segmentation allows each electrode to contribute differently to the overall capacitance, improving linearity and reducing harmonic distortion while maintaining manageable device complexity.
Solution Approach 2:
The patent applies local quality by creating back-electrode segments with different capacitance characteristics at different locations. The first, second, and third back electrodes have specifically designed capacitance values (C1, C2, C3) that differ from each other, allowing each region to contribute optimally to the overall performance, thereby improving linearity without uniformly increasing complexity.
2Measurement precision
If the diaphragm vibrates with large amplitude, then the sensitivity is improved, but adhesion between the diaphragm and back electrode occurs
Solution Approach 1:
The patent introduces a restraining portion that protrudes from the back electrode toward the diaphragm before adhesion can occur. This restraining portion acts as a mechanical stop that prevents the diaphragm from contacting the back electrode even during large-amplitude vibrations, thereby cushioning against adhesion beforehand and maintaining reliability while allowing high sensitivity.
Solution Approach 2:
The restraining portion serves as an intermediary element between the diaphragm and the back electrode. It mediates the interaction by providing a physical barrier that prevents direct contact between the diaphragm and back electrode, thus preventing adhesion while still allowing the diaphragm to vibrate with sufficient amplitude for high sensitivity.
3Measurement precision
If the gap between diaphragm and back electrode is reduced, then the capacitance sensitivity is improved, but the risk of adhesion increases
Solution Approach 1:
The restraining portion acts as an intermediary that allows the gap between diaphragm and back electrode to be reduced for improved capacitance sensitivity, while simultaneously preventing adhesion by providing a mechanical stop before contact occurs.
Solution Approach 2:
The restraining portion provides beforehand cushioning by establishing a mechanical limit that prevents the diaphragm from reaching the back electrode, allowing the initial gap to be smaller for improved sensitivity without increasing adhesion risk.
4Manufacturing precision
If multiple plate capacitor structures are added, then the linear distortion is reduced, but the device complexity increases
Solution Approach 1:
The patent segments the back-electrode structure into multiple electrodes (first, second, third back electrodes) with different capacitance values, creating multiple plate capacitor structures that work together to reduce linear distortion through differential capacitance while maintaining a relatively compact and manageable device architecture.
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 dual plate capacitor structure with air leakage and restraining portions reduces linear distortion, prevents adhesion, enhances acoustic properties, and expands application range to include differential pressure sensors.
Implementation Method 1
The diaphragm and the back electrode have a certain gap therebetween. The diaphragm and the back electrode constitute a capacitor
Implementation Method 2
the first plate capacitor structure and the second plate capacitor structure provided by the MEMS chip of the present disclosure can form a differential capacitance to mitigate the linear distortion
Implementation Method 3
Vibration of the diaphragm changes a distance between the diaphragm and the back electrode, thereby converting a sound signal into an electrical signal
Implementation Method 4
converting a sound signal into an electrical signal
Implementation Method 5
The first diaphragm and/or the second diaphragm of the MEMS chip provided by the present disclosure is provided with an air leakage structure, can excellently buffer the high-pressure airflow received by the first diaphragm and/or the second diaphragm
Implementation Method 6
reduce the acoustic impedance of the first diaphragm and/or the second diaphragm, thereby improving the acoustic properties
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Disclosed is a MEMS chip. The MEMS chip includes: a substrate with a back cavity, and a plate capacitor bank provided on the substrate; the plate capacitor bank at least includes a first plate capacitor structure and a second plate capacitor structure located below the first plate capacitor structure and arranged in parallel with the first plate capacitor structure; the first plate capacitor structure includes a first diaphragm and a first back electrode; and the second plate capacitor structure includes a second diaphragm and a second back electrode. The first plate capacitor structure and the second plate capacitor structure provided by the MEMS chip of the present disclosure can form a differential capacitance to mitigate the linear distortion, improving the ability to suppress the linear distortion and enhancing the performance of the MEMS chip.