Irregular Diaphragm MEMS Microphone for Sensitivity and Stiction Control
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Solution Overview
Problem
Condenser MEMS microphones face challenges in increasing sensitivity without risking diaphragm and backplate contact, which can lead to signal degradation and stiction issues.
Innovation Solution
A microphone design featuring a diaphragm with protrusions aligned with holes in the backplate, increasing capacitance while mitigating stiction by maintaining a controlled distance and reducing contact area, utilizing surface micromachining techniques and insulator layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the diaphragm is formed as close to the backplate as possible to increase sensitivity, then the capacitance increases and sensitivity improves, but the risk of diaphragm and backplate contact increases, leading to signal degradation and stiction
Solution Approach 1:
The diaphragm is designed with non-uniform thickness, featuring a thinner central region and thicker peripheral region. This local variation in thickness allows the central portion to approach closer to the backplate for increased capacitance and sensitivity, while the thicker edges maintain adequate spacing to prevent contact and stiction, thus resolving the contradiction between sensitivity and signal quality
Solution Approach 2:
The invention changes the geometric parameter of the diaphragm from uniform thickness to non-uniform thickness distribution. By controlling the thickness profile (with the center being thinner and edges thicker), the system optimizes the balance between capacitance (sensitivity) and minimum spacing (signal quality prevention), directly addressing the technical contradiction
2Quantity of substance
If the diaphragm and backplate are positioned close together to increase capacitance, then sensitivity improves, but contact between the diaphragm and backplate can occur, causing stiction and signal degradation
Solution Approach 1:
The diaphragm employs local quality variation through non-uniform thickness distribution, with the central region being thinner to maximize capacitance and the peripheral regions being thicker to prevent contact with the backplate. This spatially varying thickness profile allows the system to achieve high capacitance without incurring stiction problems
Solution Approach 2:
The thicker peripheral regions of the diaphragm act as a preventive cushion against contact with the backplate. By designing the edges to be thicker before contact can occur, the invention preemptively prevents stiction and signal degradation while allowing the thinner central region to maximize capacitance
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
Enhances signal-to-noise ratio and reduces stiction problems by increasing capacitance while maintaining a controlled distance between the diaphragm and backplate, effectively addressing sensitivity and signal quality issues.
Implementation Method 1
Condenser MEMS microphones typically have a diaphragm that forms a capacitor with an underlying backplate. Among other things, the sensitivity of the microphone is a function of this capacitance.
Data Source
AI summary
A microphone is formed to have a diaphragm that is configured to improve signal to noise ratio. To that end, the microphone has a backplate having a hole therethrough, and a diaphragm movably coupled with the backplate. The diaphragm has a bottom surface (facing the backplate) with a convex portion aligned with the hole in the backplate.