MEMS Microphone Diaphragm Slots for Dynamic Range
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Solution Overview
Problem
Existing MEMS microphones face challenges in achieving a wide dynamic range due to the trade-off between acoustic overload point (AOP) and sensitivity, as a diaphragm with lower elastic modulus enhances sensitivity but reduces AOP, making it difficult to achieve both high AOP and high sensitivity simultaneously.
Innovation Solution
A MEMS microphone design featuring a diaphragm with a substrate, backplate, and a plurality of slots arranged in concentric circles, where the slots have non-constant widths to relieve residual stress and enhance stiffness, allowing for increased AOP while maintaining high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the diaphragm has a lower elastic modulus (lower stiffness), then sensitivity is improved, but the acoustic overload point (AOP) is reduced
Solution Approach 1:
The diaphragm is segmented by forming multiple slots (radial slots and circumferential slots) that divide the diaphragm structure into multiple regions. This segmentation allows different portions of the diaphragm to have different effective stiffness characteristics, enabling the center region to remain compliant for sensitivity while the overall structure gains strength to handle higher acoustic pressures
Solution Approach 2:
The slots are designed with varying widths (non-uniform width) to create local variations in stiffness. The width of slots may vary along their length or around the circumference, allowing specific regions to have optimized mechanical properties - some areas more compliant for sensitivity while others provide structural support for higher AOP
2Measurement precision
If the diaphragm has a lower elastic modulus (lower stiffness), then sensitivity is improved, but the dynamic range is limited
Solution Approach 1:
By segmenting the diaphragm through strategically placed slots, the structure can accommodate a broader range of acoustic pressures. The segmented design prevents excessive deformation at high pressures while maintaining adequate compliance at low pressures, thus expanding the operational dynamic range
Solution Approach 2:
The elastic modulus distribution is changed by introducing slots with specific geometries. The parameters of the slots (width, length, position, orientation) are optimized to achieve the desired balance between sensitivity and dynamic range, allowing the diaphragm to operate effectively across a wider acoustic pressure range
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 achieves a wider dynamic range by balancing diaphragm stiffness and sensitivity, effectively addressing the limitations of existing MEMS microphones by relieving stress and improving the microphone's ability to detect a broader range of acoustic pressures.
Implementation Method 1
variations in acoustic pressure (i.e. local pressure deviation from the ambient atmospheric pressure caused by sound waves) force the diaphragm to deform correspondingly, and the deformation of the diaphragm induces a capacitance variation
Data Source
AI summary
A MEMS microphone includes a substrate, a backplate disposed on a side of the substrate, a diaphragm movably disposed between the substrate and the backplate, and a plurality of slots formed on the diaphragm. The slots are spaced apart from each other and have a non-constant width to relieve the residual stress on the diaphragm.