MEMS Transducer Dual Membrane Capacitance Enhancement
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Solution Overview
Problem
MEMS transducers, particularly capacitive microphones, face a challenge in maintaining sensitivity and signal quality as they shrink in size, leading to reduced sensor capacitance and increased electronic noise, which deteriorates performance and increases cost due to larger footprints required for fabrication.
Innovation Solution
The introduction of a secondary membrane coupled to a primary membrane via a rigid structure enhances capacitance without increasing the device footprint, maintaining sensitivity by ensuring the secondary membrane's movement is driven by the primary membrane's response to sound waves, thus limiting stiffness and flexibility alterations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the device footprint is reduced to shrink MEMS transducer size, then manufacturing cost is reduced and integration is improved, but sensor capacitance decreases and electronic noise increases, deteriorating performance
Solution Approach 1:
The patent introduces a second membrane layer stacked vertically above the first membrane, transitioning from a single-plane capacitive structure to a multi-layer three-dimensional structure. This vertical dimensionality change increases the effective capacitance-generating area without expanding the horizontal footprint, thereby improving signal quality while maintaining compact device size
Solution Approach 2:
The patent implements a nested structure where the second membrane is positioned within the vertical space above the first membrane, with both membranes sharing the same lateral footprint. The coupling structure connects the second membrane to the first, creating a compact nested arrangement that maximizes capacitance within a minimal volume
2Manufacturing precision
If a second membrane is added to increase capacitance, then capacitance per unit area increases, but device complexity and fabrication difficulty increase
Solution Approach 1:
The coupling structure serves multiple functions simultaneously: it mechanically connects the second membrane to the first membrane, provides structural support for the stacked configuration, and maintains the vertical spacing between membranes. This multi-functionality reduces the need for additional separate components, simplifying the overall device complexity despite the added membrane layer
Solution Approach 2:
The patent merges the functions of multiple structural elements into the coupling structure, which integrates mechanical coupling, structural support, and spacing maintenance. The stacked membrane configuration also merges the capacitance-generating function into a compact vertical arrangement, reducing the overall structural complexity compared to horizontal expansion
3Reliability
If the second membrane is rigidly coupled to the first membrane, then sensitivity is maintained, but stiffness increases which may reduce flexibility
Solution Approach 1:
The patent optimizes the coupling structure's mechanical parameters, including its dimensions, material properties, and connection geometry, to achieve the right balance between stiffness and flexibility. By carefully controlling these parameters, the coupling structure provides sufficient rigidity to maintain sensitivity while preserving the necessary flexibility for membrane response to acoustic signals
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
This configuration significantly increases capacitance per unit area while maintaining sensitivity and robustness, protecting the transducer from high-pressure events and reducing noise, thereby improving performance and reducing fabrication costs.
Implementation Method 1
pressure differences generated by sound waves
Implementation Method 2
measuring the capacitance between a pair of electrodes which will vary as the distance between the electrodes changes
Data Source
AI summary
The application describes a MEMS transducer comprising:a substrate; a primary membrane supported in a fixed relation relative to the substrate and a secondary membrane provided in a plane overlying the primary membrane. The secondary membrane is mechanically coupled to the primary membrane by a substantially rigid coupling structure. A rigid support plate may be interposed between the primary and secondary membranes.