Slotted MEMS Vibration Membrane for Air Damping Reduction
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Solution Overview
Problem
Current MEMS microphones, particularly capacitance-type, face challenges in enhancing sensitivity due to air damping and stiffness limitations, which affect detection area and signal-to-noise ratio.
Innovation Solution
A microphone design featuring a vibration membrane with slots covering a penetration hole, where ions are injected into specific parts to increase stiffness, and a fixed electrode with protrusions and air inlets to reduce air damping, improving sensitivity and detection area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the vibration membrane area is increased to improve detection area, then sensitivity improves, but air damping increases which reduces sensitivity
Solution Approach 1:
The vibration membrane is designed with a porous structure containing multiple through-holes that extend from one surface to the other. This porous configuration allows air to pass through the membrane rather than being blocked, significantly reducing air damping effects while preserving the membrane's detection area and sensitivity.
Solution Approach 2:
The vibration membrane exhibits non-uniform thickness distribution, with the central region being thinner than the peripheral region. This local variation in thickness optimizes the membrane's vibrational characteristics, allowing the thinner central area to be more responsive to sound waves while the thicker edges provide structural support and reduce overall air damping.
2Measurement precision
If the vibration membrane is made thinner to improve sensitivity, then detection capability improves, but stiffness decreases which affects performance
Solution Approach 1:
The vibration membrane features non-uniform thickness distribution, with the central region being thinner than the peripheral region. This local variation in thickness optimizes the membrane's vibrational characteristics, allowing the thinner central area to be more responsive to sound waves while the thicker edges provide structural support and reduce overall air damping.
Solution Approach 2:
The vibration membrane is constructed as a composite structure combining multiple materials with different properties. This composite configuration allows the membrane to achieve both high sensitivity in the detection region and adequate stiffness for structural integrity, resolving the contradiction between thinness and strength.
3Strength
If ions are injected into the vibration membrane to increase stiffness, then structural strength improves, but manufacturing complexity increases
Solution Approach 1:
Ions are injected into the vibration membrane during the manufacturing process, before the membrane is assembled into the final device. This preliminary ion implantation step pre-establishes the desired stiffness characteristics in the membrane, simplifying subsequent assembly and calibration processes while ensuring consistent performance.
Solution Approach 2:
The ion injection process modifies the physical and chemical parameters of the vibration membrane material, altering its stiffness and other properties. By controlling ion type, energy, and dosage, the membrane's mechanical properties can be precisely tuned to meet performance requirements without requiring complex post-processing.
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 design enhances sensitivity by reducing air damping and increasing stiffness, resulting in improved signal-to-noise ratios and detection capabilities, with sensitivity increased by approximately 4.7 times compared to conventional microphones.
Implementation Method 1
the piezoelectric-type MEMS microphone includes only a vibration membrane. When the vibration membrane is deformed by external sound pressure, an electrical signal is generated due to a piezoelectric effect.
Implementation Method 2
The capacitance-type MEMS microphone includes a fixed electrode and a vibration membrane. When an external sound pressure is applied to the vibration membrane, a capacitance value is changed because the distance between the fixed electrode and the vibration membrane is changed.
Data Source
AI summary
A microphone includes a substrate including a penetration hole; a vibration membrane disposed over the substrate and covering the penetration hole; a fixed electrode disposed over the vibration membrane and spaced apart from the vibration membrane; a fixed plate disposed over the fixed electrode; and a plurality of air inlets disposed in the fixed electrode and the fixed plate. The vibration membrane includes a plurality of slots positioned over the penetration hole, and an entire area of the plurality of slots is approximately 8% to approximately 19% of an entire area of the vibration membrane.