Microphone Fixing Layer Dome Shape for Sensitivity
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Solution Overview
Problem
Capacitive MEMS microphones face challenges in improving sensitivity due to the rigidity of the vibration membrane, which affects the distance between the vibrating and fixed electrodes, impacting capacitance changes and signal output.
Innovation Solution
A microphone design featuring a substrate with an acoustic hole, a vibrating electrode bonded to the substrate with an oxide layer, and a fixing layer with a dome-shaped central portion that maintains a uniform distance between the vibrating and fixed electrodes, enhancing sensitivity through controlled capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the vibration membrane is made rigid to improve structural stability, then structural stability is improved, but sensitivity deteriorates due to increased distance between electrodes
Solution Approach 1:
The fixing layer is designed with non-uniform thickness, featuring a first thickness in the first region and a second thickness in the second region. This local variation in thickness allows different regions to have different mechanical properties, enabling the membrane to maintain structural stability in some areas while achieving the required flexibility and electrode proximity in other areas, thereby resolving the contradiction between structural stability and sensitivity
Solution Approach 2:
The invention changes the physical parameter of the fixing layer by varying its thickness across different regions. By controlling the thickness parameter spatially, the membrane achieves optimal balance between structural rigidity and vibrational flexibility, allowing both structural stability and sensitivity to be satisfied simultaneously
2Reliability
If the distance between vibrating and fixed electrodes is increased to reduce capacitance interference, then interference is reduced, but sensitivity deteriorates due to smaller capacitance changes
Solution Approach 1:
The fixing layer has different thicknesses in different regions, creating local variations in the distance between electrodes. The first region has a smaller distance for high sensitivity, while the second region has a larger distance for reduced interference, allowing both requirements to be satisfied in different spatial locations
Solution Approach 2:
The membrane structure is segmented into different regions with different characteristics. The first region is optimized for sensitivity with smaller electrode spacing, while the second region is optimized for interference resistance with larger spacing, allowing the system to achieve both goals simultaneously through spatial segmentation
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 improves sensitivity by maintaining a uniform distance between the vibrating and fixed electrodes, resulting in increased capacitance changes and signal output, with sensitivity enhanced by approximately 3.1 dB compared to prior art, or 1.4 times greater, as demonstrated in the analysis.
Implementation Method 1
An edge of the vibrating electrode may be bonded to the substrate with an oxide layer therebetween
Implementation Method 2
When the vibration membrane is deformed by an external sound pressure, an electrical signal is generated due to a piezoelectric effect
Implementation Method 3
When external sound pressure is applied to the vibration membrane, a capacitance value thereof is changed as an interval between the fixing layer and the vibration membrane is also changed. In this case, the changed capacitance is outputted as a voltage signal
Data Source
AI summary
The present disclosure provides a microphone including: a substrate having an acoustic hole; a vibrating electrode disposed on the substrate; and a fixing layer disposed on the vibrating electrode, wherein a central portion of the fixing layer corresponding to the acoustic hole of the substrate is formed upwardly convex.