Piezoelectric MEMS Acoustic Sensor Structure for High-Pressure Sensitivity
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Solution Overview
Problem
Existing piezoelectric MEMS acoustic sensors with a double-electrode bimorph structure made of Mo/AlN/Mo/AlN/Mo have a maximum thickness of 2µm, which limits their ability to withstand high pressures and requires additional support layers, but these structures fail to achieve satisfactory acoustic pressure sensitivity for high-pressure environments.
Innovation Solution
A piezoelectric MEMS acoustic sensor design incorporating upper and lower support layers made of silicon-based materials, with a symmetric distribution of piezoelectric layers and electrodes, and controlled stress deformations to enhance thickness and sensitivity, allowing the sensor to operate under higher pressures and depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a double-electrode bimorph structure of Mo/AlN/Mo/AlN/Mo is used, then the sensor achieves high acoustic pressure sensitivity, but the thickness is limited to about 2μm and cannot withstand high pressure
Solution Approach 1:
The sensor structure is segmented into multiple functional layers including upper and lower support layers, upper and lower piezoelectric layers, and multiple electrodes. This segmentation allows each layer to contribute specifically to either sensitivity or pressure resistance, resolving the contradiction between the two requirements
Solution Approach 2:
The patent uses composite material structures combining Mo/ScAlN/Mo piezoelectric layers with silicon-based support layers. The composite structure leverages the high piezoelectric coefficient of ScAlN for sensitivity while the silicon-based support layers provide mechanical strength for pressure resistance
2Strength
If the thickness of the piezoelectric film is increased to improve pressure resistance, then the sensor can withstand higher pressure, but the acoustic pressure sensitivity decreases
Solution Approach 1:
Different regions of the sensor structure have different thicknesses and material properties optimized for their specific functions. The piezoelectric layers are thin for high sensitivity, while the support layers are thicker for pressure resistance. The ScAlN composition is specifically used in the piezoelectric layers to maximize local piezoelectric response
Solution Approach 2:
The patent transitions from a single-layer structure to a multi-layer stacked structure, adding the dimension of layering. This allows the sensor to achieve both thin piezoelectric regions for sensitivity and thick support regions for pressure resistance simultaneously in different spatial dimensions
3Strength
If a single-layered piezoelectric structure with a support layer is used, then pressure resistance is improved, but the acoustic pressure sensitivity remains unsatisfying
Solution Approach 1:
The patent merges multiple piezoelectric layers (upper and lower ScAlN layers) with multiple support layers and electrodes into a unified bimorph structure. This combined structure achieves both pressure resistance from the support layers and high sensitivity from the piezoelectric layers working together
Solution Approach 2:
The sensor structure is designed to dynamically respond to pressure changes with optimized stress distribution across the multiple layers. The upper and lower piezoelectric layers experience complementary stresses that enhance the overall piezoelectric output signal while the support layers provide static mechanical strength
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 structure increases the sensor's resistance to hydrostatic pressure and improves sensitivity by up to four times, enabling reliable operation in deeper water or harsher environments.
Implementation Method 1
piezoelectric MEMS acoustic sensor
Data Source
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AI summary
Provided is a piezoelectric MEMS acoustic sensor, comprising a substrate (1), an inner electrode area (13), and an outer electrode area (12); the outer electrode area (12) is located at the periphery of the inner electrode area (13), and each of the inner electrode area (13) and the outer electrode area (12) comprises a top electrode (9, 6), an upper piezoelectric layer (4), a middle electrode (10, 7), a lower piezoelectric layer (3), and bottom electrode (11, 8); the top electrode (9), middle electrode (10), and bottom electrode (11) in the inner electrode area (13) and the top electrode (6), middle electrode (7), and bottom electrode (8) in the outer electrode area (12) are separated from each other; a lower support layer (2) is provided on the top of the substrate (1), the inner electrode area (13) and the outer electrode area (12) are located on the lower support layer (2), and an upper support layer (5) made of silicon-based material is provided on the top surfaces of the inner electrode area (13) and the outer electrode area (12). 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.