MEMS Microphone Diaphragm Stiffness Resonant Frequency
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Solution Overview
Problem
MEMS microphones face a trade-off between increasing resonant frequency and maintaining sensitivity, as higher diaphragm stiffness enhances resonant frequency but decreases signal-to-noise ratio.
Innovation Solution
The design includes a substrate with a back cavity and a capacitive system featuring a back plate and diaphragm with protrusions and a sacrificial layer, where the diaphragm is positioned close to the substrate, and the back cavity opening size varies along the substrate length, increasing resonant frequency while minimizing damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If diaphragm stiffness is increased, then resonant frequency is improved, but sensitivity deteriorates
Solution Approach 1:
The patent applies local quality by differentiating the stiffness characteristics of different diaphragm regions. The first region (peripheral area) has higher stiffness to increase resonant frequency, while the second region (central area) maintains lower stiffness to preserve sensitivity for sound wave detection. This spatial differentiation of mechanical properties resolves the contradiction between resonant frequency and sensitivity.
Solution Approach 2:
The diaphragm is segmented into two distinct regions with different stiffness characteristics. The first region (peripheral) and second region (central) are structurally divided, allowing independent optimization of each zone's mechanical properties. This segmentation enables the diaphragm to simultaneously achieve high resonant frequency through the stiff peripheral region and high sensitivity through the compliant central region.
2Speed
If diaphragm stiffness is increased, then resonant frequency is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
By applying local quality to the diaphragm structure, the patent creates a peripheral region with high stiffness for elevated resonant frequency while maintaining a central region with appropriate compliance for optimal signal detection. This localized differentiation ensures that the signal-to-noise ratio is preserved in the detection region while achieving the desired resonant frequency enhancement.
3Measurement precision
If gap between back plate and diaphragm is reduced, then sensitivity is improved, but damping increases
Solution Approach 1:
The patent applies local quality to the gap structure by creating different gap distances in different regions. The first gap (in the first region) has a different distance characteristic than the second gap (in the second region). This allows the peripheral area to provide structural support with appropriate damping while the central area maintains optimal gap distance for sensitivity without excessive damping losses.
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 enhances the resonant frequency of the MEMS microphone while maintaining sensitivity by reducing damping and adjusting the gap structure, thereby improving signal-to-noise ratio.
Implementation Method 1
A micro-electro-mechanical system (MEMS) microphone is an electroacoustic transducer produced by micro-mechanical technology
Implementation Method 2
a capacitive system located on the substrate, comprising a back plate and a diaphragm opposite to the back plate
Data Source
AI summary
A MEMS microphone, includes a substrate with a back cavity, and a capacitive system including a back plate and a diaphragm located on the substrate, the back plate includes a body portion and a first protrusion, the diaphragm includes a main portion and a second protrusion, the first protrusion is corresponding to the second protrusion, the substrate includes an upper end close to the capacitive system and a lower end away from the capacitive system, an opening of the back cavity at the upper end of the substrate is larger than an opening at the lower end of the substrate. Compared with the related art, the MEMS microphone disclosed by the present disclosure could improve the resonant frequency.