MEMS Piezoelectric Resonator With Concentric Acoustic Confiners
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Solution Overview
Problem
Microelectromechanical system (MEMS) resonators face challenges in integrating with integrated circuit chips due to lateral acoustic energy leakage, which affects the quality factor and stability of resonators, especially at parallel resonance frequencies.
Innovation Solution
The use of patterned resonant confiners with dimensions equivalent to λ/2, placed around the electrode of MEMS resonators, effectively attenuates lateral acoustic energy leakage by confining the propagating waves, improving the quality factor and minimizing energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MEMS resonators are integrated with integrated circuit chips, then the device functionality is improved, but lateral acoustic energy leakage occurs which degrades the quality factor and stability
Solution Approach 1:
The patent introduces resonant confiners as intermediary structures between the piezoelectric member and the surrounding medium. These confiners act as acoustic barriers that mediate the interaction between the resonator and the substrate, preventing lateral acoustic energy leakage while allowing the resonator to be integrated with the circuit chip. The confiners are positioned at a specific distance from the piezoelectric member and have dimensions tuned to the resonant frequency to maximize their acoustic blocking effect.
2Reliability
If concentric resonant confiners are added to attenuate lateral acoustic waves, then the quality factor is improved, but the device complexity increases
Solution Approach 1:
The resonant confiner structure is segmented into multiple concentric rings with progressively increasing diameters. This segmentation allows the acoustic attenuation function to be distributed across multiple discrete elements rather than requiring a single complex continuous structure. Each ring segment contributes to the overall acoustic confinement, and the segmented design simplifies fabrication while maintaining effective attenuation of lateral acoustic waves.
Solution Approach 2:
The confiner structures are positioned at specific locations around the piezoelectric member, with each confiner having optimized dimensions (width, spacing) tailored to its local position. The confiners closer to the piezoelectric member have different dimensions compared to those farther away, creating a gradient structure that optimizes acoustic confinement locally while reducing overall complexity compared to a uniform thick barrier.
3Loss of energy
If the confiners are placed close to the piezoelectric member to maximize attenuation, then lateral energy leakage is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The confiners are designed with preliminary positioning features and reference structures that align with corresponding features on the piezoelectric member. The concentric geometry provides self-alignment during fabrication, where each successive confiner ring automatically centers on the previous ones. This preliminary geometric constraint reduces the need for high-precision active positioning during assembly, as the structure itself guides correct placement.
Solution Approach 2:
The patent optimizes the dimensional parameters of the confiners (width, spacing, diameter) to achieve effective acoustic attenuation at practical distances from the piezoelectric member. By tuning these parameters, the confiners maintain their acoustic blocking effectiveness even when positioned at larger distances, thereby reducing the stringent positioning precision requirements while still minimizing lateral energy loss.
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 approach enhances the quality factor and stability of MEMS resonators by reducing lateral energy leakage, leading to improved performance and reduced spurious modes near parallel resonance frequencies.
Implementation Method 1
A piezoelectric member is attached to the base substrate. The piezoelectric member has a first electrode attached to a bottom surface of the piezoelectric member and a second electrode attached to a top surface of the piezoelectric member
Implementation Method 2
Concentric periodically spaced confiners are attached to the first surface of the piezoelectric member and are concentric with the first electrode and spaced from the perimeter edge of the first electrode by a distance. By using concentric resonant confiners, the propagating acoustic wave is attenuated.
Data Source
AI summary
A MEMS resonator is operated at its parallel resonance frequency. An acoustic wave is propagated laterally away from a central region of the MEMS resonator through a piezoelectric layer of the MEMS resonator. The propagating acoustic wave is attenuated with concentric confiners that surround and are spaced apart from a perimeter of an electrode that forms the MEMS resonator.