Piezoelectric MEMS Acoustic Sensor Structure for Deep-Water Pressure
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Solution Overview
Problem
Existing piezoelectric MEMS acoustic sensors with a double-electrode bimorph structure face limitations in thickness due to manufacturing processes, leading to inadequate pressure resistance and sensitivity, especially in high-pressure environments.
Innovation Solution
A piezoelectric MEMS acoustic sensor design incorporating upper and lower support layers made of silicon-based materials, along with a symmetric distribution of piezoelectric layers and electrodes, enhances film thickness and stress distribution to improve pressure resistance and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a double-electrode bimorph structure with Mo/AlN/Mo/AlN/Mo is used to achieve high sensitivity, then the piezoelectric layer thickness can be increased, but the structure cannot withstand high pressure due to excessive deformation
Solution Approach 1:
The sensor structure is divided into multiple functional layers including upper and lower support layers, piezoelectric layers, and electrode layers. This segmentation allows each layer to perform its specific function - support layers provide mechanical strength for pressure resistance, while piezoelectric layers generate electrical signals for sensitivity, resolving the contradiction between strength and measurement precision
Solution Approach 2:
The patent uses composite material structure combining Mo (molybdenum), AlN (aluminum nitride), and silicon-based materials in specific layer configurations. This composite approach enables the structure to simultaneously achieve high piezoelectric sensitivity from the AlN layers and high pressure resistance from the Mo and silicon support layers, overcoming the limitation of single-material structures
2Measurement precision
If the piezoelectric layer thickness is increased to improve sensitivity, then more charge can be generated, but the film becomes too thick to be manufactured with existing processes
Solution Approach 1:
The piezoelectric function is segmented into multiple thinner piezoelectric layers (upper and lower piezoelectric layers) rather than using one thick layer. This segmentation enables each layer to be within the manufacturable thickness range while collectively providing sufficient piezoelectric effect for high sensitivity
Solution Approach 2:
Multiple piezoelectric layers are merged in a stacked configuration with alternating electrode layers, creating a bimorph structure where the combined piezoelectric effect of multiple thin layers achieves the sensitivity equivalent to or greater than a single thick layer, while remaining manufacturable
3Strength
If a single-layer piezoelectric structure with support layer is used to improve pressure resistance, then the sensor can withstand higher pressure, but the acoustic pressure sensitivity becomes insufficient
Solution Approach 1:
The sensor employs a composite multi-layer structure where silicon-based support layers provide mechanical strength for pressure resistance, while distributed piezoelectric layers (upper and lower) and Mo electrode layers provide electrical sensitivity. This composite design ensures both high pressure resistance and high acoustic pressure sensitivity simultaneously
Solution Approach 2:
The patent transitions from a single-layer piezoelectric structure to a multi-layer stacked structure in the vertical dimension. By adding upper and lower piezoelectric layers with corresponding electrodes, the structure gains enhanced pressure resistance from the distributed support while maintaining sensitivity through multiple piezoelectric active regions
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 enhanced design increases the sensor's ability to withstand hydrostatic pressure and improve sensitivity, allowing operation in deeper water or harsher environments, with charge aggregation techniques increasing sensitivity up to four times that of single-layer sensors.
Implementation Method 1
a piezoelectric layer of an existing piezoelectric MEMS acoustic sensor with high sensitivity can be made of AlN material
Implementation Method 2
the inner electrode area, the outer electrode area, and the upper support layer and the lower support layer where the inner electrode area and the outer electrode area are located all generate a stress deformation of a convex or a concave in a same direction
Data Source
AI summary
Provided is a piezoelectric MEMS acoustic sensor, comprising a substrate, an inner electrode area, and an outer electrode area; the outer electrode area is located at the periphery of the inner electrode area; a lower support layer is provided on the top of the substrate, the inner electrode area and the outer electrode area are located on the lower support layer, and an upper support layer made of silicon-based material is provided on the top surfaces of the inner electrode area and the outer electrode area. The piezoelectric MEMS acoustic sensor has high sensitivity, strong resistance to hydrostatic pressure, and satisfies application requirements of different pressure resistance and operating water depth.