MEMS Microphone Diaphragm Grid Structure for SNR
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Solution Overview
Problem
High-performance MEMS microphones face challenges in achieving a high signal-to-noise ratio (SNR) and large frequency bandwidth due to diaphragm warping and nonlinear signal relationships at higher sound pressures, which are exacerbated by the trade-off between resonant frequency and stiffness in thin diaphragms.
Innovation Solution
The implementation of a diaphragm layer structure comprising a thin closed layer and a thick structured layer with a grid structure covering the entire diaphragm area, allowing for independent layer structuring and targeted stiffness control, enhances the resonant frequency and SNR by reducing noise at higher frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a thin homogeneous diaphragm is used, then the resonant frequency is high, but the diaphragm warps and exhibits nonlinear signal relationship at higher sound pressures
Solution Approach 1:
The diaphragm is segmented into a composite structure with a thin homogeneous layer and a thick structured layer containing a grid pattern. The grid structure is divided into multiple struts that can be independently optimized, allowing the diaphragm to maintain high resonant frequency while preventing warping through the distributed structural support.
Solution Approach 2:
The diaphragm employs a composite structure combining a thin homogeneous layer (for mass reduction and high resonant frequency) with a thick structured layer containing a grid pattern (for stiffness and warping prevention). This composite approach allows simultaneous optimization of both resonant frequency and signal linearity.
2Speed
If the diaphragm thickness is reduced to increase resonant frequency, then the mass decreases, but the stiffness also decreases leading to increased warping
Solution Approach 1:
The diaphragm structure is segmented into two functional layers: a thin homogeneous layer for mass reduction and a thick structured layer with grid pattern for stiffness provision. This segmentation allows the thin layer to contribute to high resonant frequency while the thick structured layer compensates for stiffness loss through its geometric reinforcement.
Solution Approach 2:
The grid structure introduces geometric curvature and three-dimensional form to the diaphragm plane, creating arch-like and truss-like structures that provide mechanical stiffness without increasing planar thickness. This geometric reinforcement allows the diaphragm to maintain high resonant frequency while preventing warping.
3Reliability
If a thick diaphragm layer is used to increase stiffness, then warping is reduced, but the mass increases and resonant frequency decreases
Solution Approach 1:
The diaphragm is segmented into a thin homogeneous layer and a thick structured layer, where each layer performs its primary function. The thin layer minimizes mass for high resonant frequency, while the thick structured layer provides stiffness through its grid pattern. This functional segmentation resolves the trade-off between mass and stiffness.
Solution Approach 2:
The thick structured layer with grid pattern is strategically positioned and configured to provide stiffness only where needed for warping prevention, while the majority of the diaphragm area maintains thin construction for low mass. This localized structural reinforcement optimizes the balance between stiffness and resonant frequency.
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 approach enables the creation of MEMS microphone elements with high sensitivity and a broad frequency bandwidth, maintaining a linear relationship between diaphragm deflection and capacitance change while reducing noise, particularly at higher frequencies.
Implementation Method 1
The diaphragm and the counter element are each equipped with at least one capacitor electrode, so that the 'out-of-plane' deflections of the microphone diaphragm are detectable as changes in capacitance of the capacitor system
Data Source
AI summary
A concept is provided which permits the implementation of MEMS microphone elements having a very good SNR, high microphone sensitivity and a large frequency bandwidth. The microphone structure of the MEMS element is implemented in a layer structure and includes at least one sound pressure-sensitive diaphragm (210), an acoustically permeable counter element (220) and a capacitor system for detecting the diaphragm deflections, the diaphragm (210) and the counter element (220) being situated on top of each other and a distance apart from one another in the layer structure and each bring equipped with at least one electrode of the capacitor system. According to the invention, the layer structure of the diaphragm (210) includes at least one thin closed layer (1) and at least one thick structured layer (2), a grid structure (100) covering the entire diaphragm area being provided in the thick layer (2), which determines the stiffness of the diaphragm (210).