MEMS Microphone Sub-diaphragm Layout Area Reduction
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Solution Overview
Problem
MEMS microphones require multiple devices with different specifications to sense a wide range of sound pressures, increasing the layout area due to their design limitations in sensing both low and high sound pressures with specific diaphragm characteristics.
Innovation Solution
A MEMS device with multiple sub-diaphragms of varying rigidities and sensitivities fixed on the same supporter, over a shared cavity, and an anchor structure to increase the rigidity of the back plates, allowing for a reduced layout area while sensing a wide range of sound pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple microphones with different specifications are used to sense a wide range of sound pressures, then the sensing capability is improved, but the layout area increases
Solution Approach 1:
The patent combines multiple diaphragms with different rigidities into a single integrated structure that shares a common back plate and cavity. This merging approach allows the device to sense both low and high sound pressures simultaneously while occupying a single footprint area, resolving the contradiction between sensing capability and layout area.
Solution Approach 2:
The diaphragm is segmented into multiple regions with different rigidities (first diaphragm region with lower rigidity for low sound pressure, second diaphragm region with higher rigidity for high sound pressure). This segmentation allows each region to specialize in detecting specific sound pressure ranges while being part of a unified structure, improving sensing capability without increasing overall device area.
2Manufacturing precision
If a single diaphragm is designed for specific sound pressure sensing, then the diaphragm characteristics are optimized, but the ability to sense wide range of sound pressures is limited
Solution Approach 1:
Different regions of the diaphragm are assigned different local qualities (rigidities) to optimize their performance for specific sound pressure ranges. The first diaphragm region has lower rigidity optimized for low sound pressure sensing, while the second diaphragm region has higher rigidity optimized for high sound pressure sensing. This local differentiation allows each region to maintain optimized characteristics while collectively expanding the overall sensing 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
Enables efficient sensing of a wide range of sound pressures with reduced layout area by utilizing sub-diaphragms with different characteristics and an anchor structure to enhance capacitance variation and sensitivity.
Implementation Method 1
When the diaphragm is actuated to vibrate relative to the back plate(s) by sound pressure
Implementation Method 2
a distance from the diaphragm to the back plate is changed, and as a result, the capacitance value of the capacitor is accordingly changed, by which voice waves are converted into electrical signals
Data Source
AI summary
A MEMS device includes a substrate, a supporter, a first back plate, a second back plate and a diaphragm. The substrate has a cavity. The supporter is over the substrate. The first back plate is over the cavity and fixed on the supporter. The second back plate is over the cavity and fixed on the supporter. The diaphragm is between the first back plate and the second back plate. The diaphragm includes a first sub-diaphragm and a second sub-diaphragm over the cavity and fixed on the supporter.