Piezoelectric MEMS Sensor Hinge Element Stress Distribution
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Solution Overview
Problem
Piezoelectric MEMS microphones inefficiently utilize peripheral piezoelectric regions due to central-focused stress distribution, leading to underutilization of sensitive material and reduced detection efficiency.
Innovation Solution
Converting transverse forces into uniform longitudinal tensile forces applied across the entire sensitive piezoelectric region, utilizing a hinge element and compliant regions to enhance stress distribution and prevent warping, thereby increasing detection efficiency and voltage generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric material is concentrated in the central position of the membrane, then maximum deformation and stress are achieved at the sensitive region, but the peripheral portions of the piezoelectric regions are not utilized efficiently
Solution Approach 1:
The piezoelectric membrane is segmented into multiple discrete piezoelectric elements arranged in a matrix pattern across the membrane surface. This segmentation allows different regions of the membrane to be independently activated and contributes to the overall output signal, ensuring that both central and peripheral portions of the piezoelectric material are effectively utilized.
Solution Approach 2:
The invention transitions from a single central sensitive region to a two-dimensional matrix arrangement of piezoelectric elements distributed across the membrane. This dimensional expansion allows the piezoelectric material to be utilized throughout the entire membrane area, converting the inefficient single-point stress concentration into a distributed multi-point stress distribution that engages the full piezoelectric material.
2Loss of energy
If piezoelectric material is distributed across the entire membrane, then material utilization is improved, but the stress distribution becomes non-uniform and peripheral regions deflect less than central regions
Solution Approach 1:
Different regions of the membrane are assigned different functions: the central region serves as the primary sound reception area, while the peripheral regions are configured as hinge portions with reduced piezoelectric material or different structural properties. This local differentiation ensures that stress is concentrated where needed for sound detection while allowing peripheral regions to fulfill their mechanical function without generating spurious signals.
Solution Approach 2:
Hinge elements are introduced as intermediary structures connecting the central membrane region to the substrate. These hinge elements act as mechanical mediators that transmit forces uniformly to the piezoelectric elements while maintaining proper stress distribution, preventing both warping and non-uniform stress concentration.
3Ease of operation
If the membrane is made compliant to allow deflection, then sound wave detection is enabled, but warping occurs that reduces detection efficiency
Solution Approach 1:
The hinge elements function as counterbalancing structures that oppose warping forces. By providing a rigid mechanical connection to the substrate at strategic locations, the hinge elements counteract the warping tendency of the compliant membrane, maintaining flatness in peripheral regions while allowing controlled deflection in the central sound-receiving region.
Solution Approach 2:
The membrane is segmented into a central compliant region for sound detection and peripheral rigid hinge regions for structural stability. This segmentation allows different portions of the same membrane structure to have different mechanical properties, enabling simultaneous achievement of compliance for detection and rigidity for preventing warping.
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 solution enables improved detection efficiency and increased voltage generation by uniformly applying stress across the sensitive region, reducing capacitance and enhancing the sensitivity of the sensor.
Implementation Method 1
piezoelectricity, i.e., the capacity of some materials of generating a voltage when subjected to a deformation
Data Source
AI summary
A MEMS sensor, in particular a microphone, of a piezoelectric type, formed in a membrane of semiconductor material accommodating a compliant portion, which extends from a first surface to a second surface of the membrane. The compliant portion has a Young's modulus lower than the rest of the membrane. A sensitive region having piezoelectric material extends on the first surface, over the compliant portion and is fixed at its ends to the membrane on opposite sides of the compliant portion. A third area of the membrane, arranged between the compliant portion and the second surface, forms a hinge element.