MEMS Transducer Membrane Anchoring Structure for Noise Reduction
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Solution Overview
Problem
MEMS electroacoustic transducers face challenges with low signal-to-noise ratio and sensitivity due to turbulent air flow and dependence on process spread, which affects the size and frequency response of the membrane.
Innovation Solution
A fully clamped MEMS transducer design with a membrane anchored along its periphery and a membrane anchoring structure that controls the size of the vibrating portion, reducing turbulence through linear air flow paths and allowing independent optimization of electrical, mechanical, and acoustic structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the membrane is anchored only on part of its perimeter (semi-clamped type), then the manufacturing process is simplified, but the signal-to-noise ratio deteriorates due to turbulent air flow in the ventilation hole
Solution Approach 1:
The membrane anchoring structure is segmented into multiple discrete anchor points distributed along the peripheral portion of the membrane, rather than continuous anchoring. This segmentation maintains manufacturing simplicity while the distributed anchor points collectively provide sufficient constraint to eliminate turbulent air flow noise.
Solution Approach 2:
The membrane anchoring structure acts as an intermediary element between the membrane and the substrate. It provides the necessary mechanical constraint to stabilize air flow while maintaining the beneficial properties of the semi-clamped configuration, effectively mediating between manufacturing simplicity and noise reduction requirements.
2Ease of manufacture
If the membrane size is controlled by process spread, then the manufacturing process is simpler, but the frequency response and sensitivity deteriorate due to dependence on process variations
Solution Approach 1:
The membrane anchoring structure is formed in advance during the manufacturing process, establishing precise geometric constraints before final device completion. This preliminary action defines the exact size and shape of the vibrating membrane portion, eliminating subsequent dependence on process spread variations.
Solution Approach 2:
The design transitions from controlling membrane size through process parameters to controlling it through geometric design parameters of the anchoring structure. By changing the control mechanism from process-based to geometry-based, precise membrane size control is achieved independently of process spread.
3Object-affected harmful factors
If the membrane is fully clamped along its periphery, then the signal-to-noise ratio is improved by reducing turbulence, but the device complexity increases
Solution Approach 1:
The full peripheral anchoring is segmented into discrete anchor points distributed around the membrane perimeter. This segmentation achieves the noise reduction benefits of full clamping while maintaining the structural simplicity and manufacturability of partial anchoring, effectively resolving the contradiction between noise reduction and device complexity.
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 solution enhances the signal-to-noise ratio and sensitivity by minimizing turbulence and process spread dependence, enabling precise control of membrane size and frequency response, leading to improved acoustic characteristics.
Implementation Method 1
The membrane 2 and the back plate 5 are, at least in part, of conductive material or carry conductive regions so as to form the plates of a sensing capacitor. In use, acoustic waves impinging upon the membrane 3 cause bending thereof and thus bring about a variation of the distance of the membrane from the back plate and a consequent capacitance variation of the sensing capacitor
Implementation Method 2
MEMS techniques of micromachining semiconductor devices enable production of micrometric structures within layers of semiconductor material, deposited (for example, polycrystalline silicon layers) or grown (for example, epitaxial layers) over sacrificial layers and/or other semiconductor or insulating layers, which are at least partially removed through chemical etching to form mobile or flexible regions
Data Source
AI summary
An electroacoustic MEMS transducer, having a substrate of semiconductor material; a through cavity in the substrate; a back plate carried by the substrate through a plate anchoring structure, the back plate having a surface facing the through cavity; a fixed electrode, extending over the surface of the back plate; a membrane of conductive material, having a central portion facing the fixed electrode and a peripheral portion fixed to the surface of the back plate through a membrane anchoring structure; and a chamber between the membrane and the back plate, peripherally delimited by the membrane anchoring structure.