MEMS Microphone Membrane Slit Layout for Stress-Stable Sensitivity
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Solution Overview
Problem
The sensitivity of MEMS microphones is affected by parasitic capacitance and variations in internal stress from materials like the spacer and insulating film, leading to inconsistent performance.
Innovation Solution
The MEMS element design includes slits in the vibrating membrane's peripheral portion, with the backplate having etching holes positioned outside the acoustic holes, and the insulating film under the membrane is etched to minimize stress transmission, ensuring the membrane is held with a minimal width and separated from the spacer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the vibrating membrane is made to vibrate freely, then sensitivity is improved, but the membrane becomes unstable due to stress from surrounding structures
Solution Approach 1:
The patent divides the insulating film into multiple segments by forming slits in the vibrating membrane, which segment the stress transmission paths. The insulating film is separated into regions: a first insulating film region between the slits, and a second insulating film region at the periphery, creating distinct zones that manage stress differently to maintain both sensitivity and stability.
Solution Approach 2:
The patent extracts or removes portions of the insulating film by forming slits that extend through the vibrating membrane and into the insulating film. This extraction creates gaps that reduce the mechanical coupling between the membrane and the substrate, thereby reducing stress transmission while maintaining the membrane's vibrational freedom for high sensitivity.
2Stability of the object's composition
If the insulating film is completely removed under the vibrating membrane, then stress influence is reduced, but the membrane loses support and becomes unstable
Solution Approach 1:
The patent applies local quality by differentiating the insulating film structure into regions with different functions. The first insulating film region (between slits) provides mechanical support and stability, while the second insulating film region (at the periphery near slits) is minimized or removed to reduce stress transmission. This localized differentiation allows the membrane to have both support and stress reduction simultaneously.
3Stability of the object's composition
If the vibrating membrane is tightly fixed to the substrate, then stability is improved, but stress from the substrate is transmitted to the membrane
Solution Approach 1:
The patent introduces an intermediary structure by forming the slits to extend into the insulating film, creating a gradual transition zone between the membrane and substrate. This intermediary insulating film region acts as a stress buffer, allowing the membrane to be firmly fixed for stability while the slit extensions reduce the direct stress transmission path from the substrate to the membrane.
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 design stabilizes the vibrating membrane's performance by reducing stress influence, allowing for a more sensitive and consistent microphone operation.
Implementation Method 1
The vibrating membrane 30 vibrates by a sound pressure propagated through this acoustic hole 50b, changing capacitance between the backplate 50 and the vibrating membrane 30.
Data Source
AI summary
A MEMS element comprises a substrate 1 with an opening 1a, a vibrating membrane 3 formed on the substrate 1 through an insulating film 2, and a backplate 5 fixed to a spacer 4 on the substrate 1. The vibrating membrane 3 has intermittent slits 3a along its edge 3d. The backplate 5 has acoustic holes 5b in the center, and etching holes 5c in the periphery thereof and closer to the edge side than the outermost peripheral end of the slits of the vibrating membrane 3 in planar view. The edge 3d of the vibrating membrane 3 and portion of the insulating film 2 under the vibrating membrane 3 are spaced apart from the bottom end of the spacer 4. The insulating film is etched from the edge 3d of the vibrating membrane 3 and the slits 3a to under the vibrating membrane 3.