MEMS Diaphragm Intersecting Structure for Noise Reduction
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Solution Overview
Problem
MEMS-based capacitive and acoustic sensors face challenges with signal-to-noise ratio degradation due to Brownian motion and sensitivity reduction from air escape, especially under varying pressures or loud sounds, and are prone to diaphragm displacement and stress concentration.
Innovation Solution
A MEMS structure with a diaphragm secured by anchors and a fixed membrane over a slit, where the diaphragm protrudes toward the anchors, creating an intersecting structure that minimizes noise from Brownian motion and maintains overlap with the substrate to prevent excessive displacement, while the fixed membrane maintains acoustic resistance and prevents air escape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the diaphragm and silicon substrate overlap when viewed along the normal to the diaphragm, then Brownian motion of air is minimized, but acoustic resistance is reduced and sensitivity is degraded
Solution Approach 1:
The patent divides the diaphragm structure into two functional regions: a central overlapping region with the silicon substrate to minimize Brownian motion noise, and a peripheral non-overlapping region that provides acoustic resistance. This segmentation allows each region to fulfill its specific function without compromising the other, resolving the contradiction between noise reduction and acoustic resistance maintenance.
2Reliability
If a fixed membrane is secured to the substrate via an anchor formed by oxidized film, then acoustic resistance is maintained, but the anchor may be lost due to production process variations causing the fixed membrane to separate
Solution Approach 1:
The patent removes the oxidized film anchor from the structure and replaces it with a mechanical anchor formed by protruding supports. This extraction of the problematic oxidized film connection and substitution with a more reliable mechanical structure eliminates the issue of anchor loss due to production variations while maintaining the fixed membrane's acoustic resistance function.
3Length of moving object
If the diaphragm is made extremely small using MEMS processing techniques, then sensor size is reduced, but Brownian motion of air creates acoustic noise that degrades signal-to-noise ratio
Solution Approach 1:
The patent applies different structural characteristics to different regions of the diaphragm: the central region overlaps with the silicon substrate to minimize Brownian motion noise, while the peripheral region maintains acoustic resistance. This local differentiation allows the extremely small sensor to achieve both miniaturization benefits and acceptable noise performance.
4Reliability
If the diaphragm protrudes toward the anchors creating an intersecting structure, then robustness to input pressure is improved, but device complexity increases
Solution Approach 1:
The patent merges the diaphragm structure with the support anchors by making the diaphragm protrude toward and intersect with the anchor points. This integration creates a unified structure where the supports serve both mechanical anchoring and structural reinforcement functions, improving robustness to input pressure while minimizing the addition of separate complex components.
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 enhances the signal-to-noise ratio and robustness of the sensors to input pressure, reducing stress concentration and maintaining sensitivity by controlling diaphragm displacement and air flow.
Implementation Method 1
capacitive sensor manufactured using microelectromechanical systems (MEMS) techniques outperform the ECM in terms of digitization and small size
Implementation Method 2
The diaphragm vibrates due to pressure
Implementation Method 3
air escapes from the gap between the diaphragm and the silicon substrate, reducing the acoustic resistance
Implementation Method 4
a plurality of anchors securing the diaphragm to the substrate or to another component
Data Source
AI summary
A MEMS structure that includes: a substrate having an opening; a diaphragm arranged opposite the opening in the substrate; a plurality of anchors securing the diaphragm to the substrate or to another component; and a fixed membrane surrounding the diaphragm over a slit. The outline of the diaphragm protrudes toward the anchors and includes a predetermined intersecting structure that when viewed from the normal to the diaphragm, the diaphragm protrudes toward the anchors in at least one location on the diaphragm between two intersection points of the outline of the diaphragm and the outline of the opening in the substrate. The intersecting structure is configured such that the distance between the two intersection points is greater than the width of the diaphragm at a location closest to an anchor.