Coupled MEMS Membrane Structure for Higher SNR Microphones
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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, necessitating improved mechanical, operational, and electrical characteristics.
Innovation Solution
A MEMS device with a bridge design featuring mechanically coupled deflectable membrane structures and a rigid electrode structure, anchored along spaced perimeter regions to a carrier element, enhancing mechanical compliance and SNR without increasing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the transducer element is mechanically anchored along the entirety of its perimeter (conventional SDM design), then the mechanical stability is improved, but the mechanical compliance is reduced
Solution Approach 1:
The continuous perimeter anchor structure is segmented into discrete clamping structures positioned at spaced perimeter regions. This segmentation allows the membrane to remain stable at anchor points while maintaining compliance in the unclamped regions between anchors, resolving the contradiction between stability and compliance.
Solution Approach 2:
Different regions of the membrane perimeter are treated differently: some regions have clamping structures providing mechanical stability, while other regions remain unclamped to maintain mechanical compliance. This local differentiation allows both stability and compliance to coexist in different parts of the same structure.
2Stability of the object's composition
If the transducer element is mechanically anchored along the entirety of its perimeter (conventional SDM design), then the mechanical stability is improved, but the sensitivity and SNR are reduced
Solution Approach 1:
By segmenting the anchor structure into spaced clamping regions, the membrane can vibrate more freely in the unclamped regions, increasing sensitivity to acoustic pressure changes while maintaining stability at the discrete anchor points, thus improving SNR.
Solution Approach 2:
The mechanical boundary conditions are changed from continuous clamping to discrete clamping, altering the membrane's vibrational characteristics and increasing its sensitivity to acoustic signals, which directly improves measurement precision and SNR.
3Volume of moving object
If the MEMS device is continuously miniaturized to reduce size, then the device dimensions are reduced, but the signal-to-noise ratio is degraded
Solution Approach 1:
By changing the clamping configuration from continuous to discrete spaced regions, the membrane maintains higher compliance and sensitivity even at reduced dimensions, allowing miniaturization without sacrificing SNR performance.
Solution Approach 2:
The discrete clamping allows the membrane to have more dynamic freedom of movement, enhancing its response to acoustic signals in miniaturized devices and maintaining high SNR despite reduced physical size.
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 MEMS device achieves approximately three times higher mechanical compliance and improved sensitivity, thereby increasing the SNR and overall performance of MEMS microphones or loudspeakers.
Implementation Method 1
MEMS devices, such as MEMS sound transducers (MEMS microphones or MEMS loudspeakers) function essentially as a transducer element capacitively converting an acoustic pressure wave into an analog electrical signal
Implementation Method 2
the deflectable portion of the first deflectable membrane structure and the deflectable portion of the second deflectable membrane structure are mechanically coupled by means of mechanical connection elements (e.g. pillars or columns) to each other
Data Source
Figure 1a~1c
Figure 2a~2d
Figure 3a~3b
AI summary
MEMS device (10) comprising a transducer element (12) having a first deflectable membrane structure (14), a rigid electrode structure (16) and a second deflectable membrane structure (18) in a vertically spaced configuration, wherein the rigid electrode structure (16) is arranged between the first (14) and second (18) deflectable membrane structures, wherein the first (14) and second (18) deflectable membrane structures each comprises a deflectable portion (14-1, 18-1), and wherein the deflectable portion (14-1) of the first deflectable membrane structure (14) and the deflectable portion (18-1) of the second deflectable membrane structure (18) are mechanically coupled by means of mechanical connection elements (20) to each other and are mechanically decoupled from the rigid electrode structure (16); a carrier element (22) for supporting the transducer element (12) and a plurality of clamping structures (24-1, ..., 24-#) for mechanically connecting the transducer element (12) to the carrier element (22) along spaced perimeter regions of the transducer element (12).