Dual-Membrane MEMS Microphone Bridge Structure for Higher SNR
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Solution Overview
Problem
Conventional MEMS sound transducers face challenges in achieving high signal-to-noise ratio (SNR) and mechanical compliance due to continuous miniaturization, particularly in sealed dual-membrane (SDM) microphones, where the transducer element is anchored along its entire perimeter.
Innovation Solution
A MEMS device with a bridge design featuring mechanically coupled first and second deflectable membrane structures, anchored along spaced perimeter regions, and decoupled from a rigid electrode structure, enhancing mechanical compliance and SNR without increasing size or manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the transducer element is anchored along the entirety of its perimeter, then mechanical stability is improved, but mechanical compliance deteriorates
Solution Approach 1:
The continuous perimeter anchor structure is segmented into multiple discrete clamping structures positioned at spaced locations around the perimeter. This segmentation allows different regions to have different mechanical properties: clamped regions provide stability while unclamped regions maintain compliance. The bridge structure with spaced clamping structures embodies this segmentation principle by dividing the anchor into separate points rather than a continuous attachment.
2Volume of moving object
If the transducer element is miniaturized, then device size is reduced, but signal-to-noise ratio deteriorates
Solution Approach 1:
The invention changes the mechanical parameters of the transducer element by introducing a bridge structure with specific compliance characteristics. This bridge structure has optimized mechanical properties that allow small-sized devices to maintain high compliance, thereby preserving signal-to-noise ratio despite miniaturization. The compliant bridge design compensates for the size reduction through enhanced mechanical flexibility.
3Adaptability or versatility
If mechanical compliance is increased, then sensitivity is improved, but mechanical stability deteriorates
Solution Approach 1:
The bridge structure implements local quality by having different mechanical characteristics in different regions: the central bridge portion has high compliance to enable sensitivity, while the anchor regions provide stability. This spatial variation in mechanical properties allows the structure to simultaneously achieve both compliance and stability, with each region optimized for its specific function.
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 bridge design achieves approximately three-times higher mechanical compliance and improved SNR in SDM microphones, leading to enhanced sensitivity and operational performance.
Implementation Method 1
a first deflectable membrane structure (14), a rigid electrode structure (16) and a second deflectable membrane structure (18) in a vertically spaced configuration
Implementation Method 2
function essentially as a transducer element capacitively converting an acoustic pressure wave into an analog electrical signal
Data Source
AI summary
In an embodiment a MEMS device includes a transducer element having a first deflectable membrane structure, a rigid electrode structure and a second deflectable membrane structure in a vertically spaced configuration, wherein the rigid electrode structure is arranged between the first and second deflectable membrane structures, wherein each of the first and second deflectable membrane structures comprises a deflectable portion, and wherein the deflectable portion of the first deflectable membrane structure and the deflectable portion of the second deflectable membrane structure are mechanically coupled by mechanical connection elements to each other and are mechanically decoupled from the rigid electrode structure, a carrier element for supporting the transducer element, and a plurality of clamping structures mechanically connecting the transducer element to the carrier element along spaced perimeter regions of the transducer element.