Stacked MEMS Microphone Structure for High-SNR Miniaturization
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Solution Overview
Problem
Existing MEMS silicon microphones face challenges in achieving high sensitivity and Signal-to-Noise Ratio (SNR) performance while maintaining miniaturization and reducing manufacturing complexity, with current solutions either contradicting miniaturization trends or involving complex fabrication processes.
Innovation Solution
A MEMS microphone design with dual diaphragms and dual backplates is created by bonding two microphone structures, each with a single diaphragm and backplate, forming a common vibrating diaphragm, which increases capacitance and allows for single-ended ultra-large capacitance output and differential capacitive signal generation, improving sensitivity and SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of the MEMS device is increased to enhance sensitivity and SNR, then sensitivity and SNR are improved, but device miniaturization is compromised
Solution Approach 1:
The patent divides the single diaphragm structure into multiple diaphragms (first diaphragm, second diaphragm, third diaphragm) that work together in a segmented configuration. Each diaphragm contributes to the overall capacitive signal, enabling enhanced sensitivity and SNR without requiring a single large diaphragm, thus maintaining device miniaturization while improving measurement precision.
Solution Approach 2:
The patent transitions from a single-plane diaphragm configuration to a multi-layer stacked configuration with diaphragms arranged at different heights (first cavity between first and second diaphragms, second cavity between third and fourth diaphragms). This dimensional arrangement increases the effective capacitive area without increasing the device footprint, resolving the contradiction between sensitivity enhancement and miniaturization.
2Measurement precision
If new structures are designed to realize differential signal output, then noise reduction and high SNR are achieved, but fabrication complexity increases
Solution Approach 1:
The patent merges multiple diaphragms and backplates into a single integrated stacked structure where the second backplate serves as a common reference for both first and second cavities. This unified design enables differential signal output from multiple diaphragms simultaneously, achieving noise reduction and high SNR while avoiding the need for separate complex fabrication processes for each differential pair.
Solution Approach 2:
The second backplate performs multiple functions: it serves as the backplate for the second cavity, provides a common reference electrode for differential signaling, and enables both single-ended and differential output modes. This multi-functionality achieves high SNR performance without requiring additional specialized structures or complex fabrication steps.
3Measurement precision
If multiple diaphragms and backplates are integrated to increase capacitance, then sensitivity and SNR are improved, but manufacturing complexity increases
Solution Approach 1:
The patent forms the first and second cavities between the diaphragms and backplates during the same fabrication process step, rather than creating them sequentially. The cavities are defined by etching through support layers before the diaphragms are released, which simplifies the manufacturing process compared to forming cavities after diaphragm assembly, thereby reducing manufacturing complexity while achieving increased capacitance through multiple diaphragms.
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 and SNR performance while reducing manufacturing complexity, achieving a compact MEMS microphone with improved signal processing capabilities.
Implementation Method 1
bonding the second vibrating diaphragm and the fourth vibrating diaphragm directly to form a common vibrating diaphragm
Implementation Method 2
When sound pressure is applied to the sensor, the diaphragm vibrates in response to sound, changing the distance between the backplate and the diaphragm
Implementation Method 3
the MEMS sensor is a variable capacitor with a fixed backplate and a vibrating diaphragm... changing the distance between the backplate and the diaphragm, thereby altering the capacitance of the variable capacitor
Data Source
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AI summary
A MEMS microphone and a manufacturing method therefor are provided. The MEMS microphone includes a first microphone structure (110), a second microphone structure (120) and a common vibrating diaphragm (130). The first microphone structure (110) includes a first vibrating diaphragm (111), a first backplate (112) and a second vibrating diaphragm (113) arranged at intervals from bottom to top. A first cavity (114) is formed between the first vibrating diaphragm (111) and the second vibrating diaphragm (113). The first backplate (112) is arranged parallel to the first vibrating diaphragm (111) and the second vibrating diaphragm (113) and extends through the first cavity (114). The second microphone structure (120) includes a third vibrating diaphragm (121), a second backplate (122) and a fourth vibrating diaphragm (123) arranged at intervals from top to bottom. A second cavity (124) is formed between the third vibrating diaphragm (121) and the fourth vibrating diaphragm (123). The second backplate (122) is arranged parallel to the third vibrating diaphragm (121) and the fourth vibrating diaphragm (123) and extends through the second cavity (124). The common vibrating diaphragm (130) is formed by directly bonding the second vibrating diaphragm (113) and the fourth vibrating diaphragm (123). In the MEMS microphone and the manufacturing method therefor, a microphone structure having three diaphragms and two backplates is formed by means of forming the common vibrating diaphragm (130), thus improving the performance of the MEMS microphone, and reducing the process difficulty of manufacturing the MEMS microphone.