Dynamic Valve Layer for MEMS Microphone Sensitivity
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Solution Overview
Problem
Existing MEMS microphones face challenges in achieving a wide dynamic range, as they struggle to simultaneously maintain high acoustic overload point (AOP) and sensitivity, especially at low frequencies, due to the trade-off between diaphragm stiffness and harmonic distortion.
Innovation Solution
The design incorporates a dynamic valve layer with flap portions that deform to relieve air pressure and enhance sensitivity, while maintaining structural integrity through a combination of dielectric layers, vent holes, and rib structures, allowing for improved air pressure handling and sensitivity at low frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the diaphragm has a lower elastic modulus (lower stiffness), then sensitivity is improved, but total harmonic distortion (THD) increases and acoustic overload point (AOP) is reduced
Solution Approach 1:
The invention divides the acoustic sensing function into two separate components: the diaphragm for sensing acoustic pressure and the valve layer for controlling air flow. This segmentation allows each component to be optimized independently - the diaphragm can be designed with lower stiffness for high sensitivity while the valve layer handles the mechanical stress and distortion control
Solution Approach 2:
The valve layer acts as an intermediary between the diaphragm and the acoustic environment. It mediates the air flow through the vent hole, allowing the diaphragm to operate in a controlled pressure environment that reduces harmonic distortion while maintaining sensitivity
2Measurement precision
If the diaphragm has a lower elastic modulus (lower stiffness), then sensitivity at low frequency is enhanced, but total harmonic distortion (THD) increases
Solution Approach 1:
By separating the sensing function (diaphragm) from the flow control function (valve layer), the invention allows the diaphragm to be optimized for low-frequency sensitivity without being constrained by the need to handle high mechanical stresses that cause harmonic distortion
Solution Approach 2:
The invention changes the mechanical parameters of the system by introducing a compliant valve layer that can deform in response to pressure changes. This alters the overall system behavior, allowing the diaphragm to operate with lower stiffness while the valve layer absorbs the nonlinear mechanical effects that cause harmonic distortion
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 enables MEMS microphones to achieve a wider dynamic range by effectively managing air pressure and reducing harmonic distortion, thereby enhancing sensitivity and reliability across varying acoustic pressures.
Implementation Method 1
the flap portion deforms when air flows through the vent hole
Implementation Method 2
variations in acoustic pressure force the diaphragm to deform correspondingly, and the deformation of the diaphragm induces a capacitance variation
Data Source
AI summary
A micro-electro-mechanical system (MEMS) device is provided. The MEMS device includes a substrate, a backplate disposed on a side of the substrate, a diaphragm, and a dynamic valve layer. The substrate forms an opening. The diaphragm is disposed on the side of the substrate and extends across the opening of the substrate, wherein the diaphragm forms a vent hole. The dynamic valve layer is disposed on the side of the substrate and includes a flap portion, wherein the flap portion covers at least a part of the vent hole when viewed in a direction perpendicular to the diaphragm, and the flap portion deforms when air flows through the vent hole.