MEMS Chip Back Cavity Trapezoidal Wall Resonance
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Solution Overview
Problem
MEMS chips face limitations in increasing resonance frequency and signal noise ratio (SNR) due to fixed package structure, where higher membrane stiffness reduces sensitivity and volume reduction increases noise and lowers SNR.
Innovation Solution
The MEMS chip design includes a substrate with a back cavity and a capacitance system featuring a membrane and back plate with a trapezoidal inner wall projection, varying opening widths, and through holes on the back plate to enhance resonance frequency and SNR without increasing the overlapped area between the membrane and substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the membrane stiffness is increased to improve resonance frequency, then the resonance frequency is improved, but the sensitivity and signal noise ratio (SNR) reduce
Solution Approach 1:
The patent changes the geometric parameters of the back cavity by creating a trapezoidal inner wall structure with varying opening widths. The first opening near the membrane has a larger width while the second opening away from the membrane has a smaller width, optimizing the acoustic compliance and volume distribution without increasing membrane stiffness
2Speed
If the volume of the back cavity is decreased to improve resonance frequency, then the resonance frequency is improved, but the overlapped area between the membrane and substrate increases, resulting in more noise and lower SNR
Solution Approach 1:
The patent applies local quality by creating non-uniform distribution of the back cavity volume through the trapezoidal inner wall structure. The varying width along the vertical direction creates different acoustic compliance zones, concentrating the volume reduction away from the membrane area while maintaining adequate spacing between the membrane and substrate to reduce noise
Solution Approach 2:
The patent introduces a dimensional variation by creating a trapezoidal cross-section in the back cavity inner wall. This transforms the uniform cylindrical/spherical cavity into a structured cavity with varying cross-sectional area, allowing independent optimization of volume and membrane-substrate spacing through the width variation along the vertical dimension
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 effectively improves resonance frequency and maintains high signal noise ratio by optimizing the back cavity volume and reducing noise, achieving dual advantageous effects.
Implementation Method 1
A sound hole is provided on the shell communicating the back cavity, thus allowing the membrane to move under external pressure wave
Implementation Method 2
the MEMS chip includes a substrate with a back cavity and a capacitance system disposed on the substrate. The capacitance system includes a membrane and a back plate arranged at an interval
Data Source
AI summary
The present disclosure discloses a MEMS chip including a capacitance system and a substrate with a back cavity. The capacitance system includes a back plate and a membrane; the substrate is located on one side of the membrane away from the back plate, including a first surface opposite to the membrane, a second surface opposite to the first surface, and an inner wall connecting the first surface and the second surface and enclosing the back cavity; the inner wall includes a first opening close to the membrane, having a first width along a first direction perpendicular with a vibration direction of the membrane, and a second opening away from the membrane, having a second width smaller than the first width along the first direction. The resonance frequency of the MEMS chip has been effectively improved and the SNR is simultaneously high.