MEMS Microphone Diaphragm Superimposed Layer for Sensitivity
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Solution Overview
Problem
Capacitive MEMS microphones face a reduction in sensitivity when the chip area is reduced, as the sensitivity is determined by the diaphragm's size, deformation extent, and shape, and existing designs struggle to maintain sensitivity without increasing the chip area.
Innovation Solution
A capacitive MEMS microphone design that includes a substrate with an opening, a lower polar plate, a supporting portion, an upper polar plate, and a superimposed layer forming an accommodating cavity, where the superimposed layer increases the thickness of the diaphragm's central region, limiting deformation and enhancing capacitance change, thereby increasing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the chip area is reduced, then the miniaturization is improved, but the sensitivity is reduced
Solution Approach 1:
The patent applies local quality by adding a superimposed layer specifically to the central region of the diaphragm rather than uniformly across the entire structure. This localized reinforcement increases the thickness and stiffness precisely where needed (central region) to maintain sensitivity, while leaving other areas unchanged to preserve miniaturization benefits. The selective application of material properties resolves the contradiction between small size and high sensitivity.
Solution Approach 2:
The patent resolves the area-sensitivity contradiction by transitioning from a two-dimensional planar diaphragm to a three-dimensional structured diaphragm with varying thickness. The superimposed layer creates a non-uniform thickness profile (thinner at edges, thicker at center), effectively using the thickness dimension to enhance sensitivity without increasing the chip's planar area. This dimensional approach allows maintaining small footprint while achieving high sensitivity.
2Measurement precision
If the diaphragm deformation is increased, then the sensitivity is improved, but the frequency response becomes distorted
Solution Approach 1:
The patent controls deformation characteristics by applying the superimposed layer only to the central region of the diaphragm. This localized thickening restricts excessive deformation in the central area while allowing controlled movement at the edges. The result is a balanced deformation pattern that maintains linearity across different frequencies, preventing distortion while preserving sensitivity enhancement from the capacitance changes.
Solution Approach 2:
The patent modifies the physical parameters of the diaphragm by changing its thickness distribution through the superimposed layer. This parameter change (increased central thickness) alters the mechanical properties to achieve optimal deformation characteristics - sufficient movement for sensitivity while maintaining structural integrity for frequency stability. The parameter modification resolves the contradiction between deformation extent and frequency response quality.
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 effectively increases sensitivity by maintaining a flatter diaphragm central region during vibration, resulting in a greater capacitance change for the same displacement, without reducing the chip area.
Implementation Method 1
the sensitivity of the silicon-based microphone is determined by the size of the diaphragm, the extent of deformation and the shape of the deformation
Implementation Method 2
The back plate and the diaphragm cooperatively form a plate capacitor, the sound drives the flexible diaphragm to vibrate by the air, thereby changing the capacitance value of the plate capacitor
Data Source
AI summary
An MEMS microphone comprises a substrate (100), a support portion (200), a superimposed layer (600), an upper plate (300) and a lower plate (400). The substrate (100) is provided with an opening (120) penetrating the middle thereof; the lower plate (400) is arranged above and spanning the substrate (100); the support portion (200) is fixed on the lower plate (400); the upper plate (300) is attached on the support portion (200); an accommodation cavity (500) is formed from the support portion (200), the upper plate (300) and the lower plate (400); the superimposed layer (600) is attached on an central region of the upper plate (300) or the lower plate (400), and insulation is achieved between the upper plate (300) and a lower plate (400).