Acoustic Wave Resonator Mass Loading for Transverse Mode Suppression
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Solution Overview
Problem
Existing acoustic wave devices, particularly piezoelectric MEMS resonators, face challenges in suppressing transverse modes, which can lead to inaccurate oscillations, unstable sensors, and poor filter performance due to passband ripples and limited rejection.
Innovation Solution
The implementation of a multi-layer mass loading strip with a higher density than the temperature compensation layer, positioned to overlap the edge portions of the interdigital transducer electrode's fingers, effectively suppresses transverse modes by creating a border region with a different velocity from the central active region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer mass loading strip is used, then the structure is simple, but transverse mode suppression is insufficient
Solution Approach 1:
The patent applies composite materials by using a multi-layer mass loading strip structure where each layer has different density characteristics. The first layer has lower density and the second layer has higher density, creating a composite structure that provides superior transverse mode suppression compared to single-layer designs. This composite approach allows optimization of both mechanical properties and acoustic performance.
Solution Approach 2:
The patent transitions from a single-layer to a multi-layer vertical structure, adding the dimension of layering in the vertical direction. This dimensional change enables independent optimization of each layer's density and thickness, providing enhanced control over acoustic wave propagation and transverse mode suppression while maintaining a compact form factor.
2Ease of manufacture
If the mass loading strip is positioned close to the piezoelectric layer, then the adhesion requirement is high, but manufacturing is easier
Solution Approach 1:
The patent applies local quality by assigning different density characteristics to different layers of the mass loading strip. The first layer has lower density and the second layer has higher density, allowing each layer to be optimized for its specific function. This local differentiation enables the structure to meet both adhesion requirements and manufacturing constraints by distributing functional requirements across multiple layers with localized properties.
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 solution enhances the accuracy and stability of oscillators and sensors while improving the performance of acoustic filters by effectively suppressing transverse modes, thereby reducing passband ripples and increasing rejection.
Implementation Method 1
The mass loading strip is arranged to suppress a transverse mode by creating a border region with a different velocity from a central active region of the interdigital transducer electrode
Implementation Method 2
Piezoelectric microelectromechanical systems (MEMS) resonators can process electrical signals using mechanically vibrating structures
Implementation Method 3
temperature compensation layer disposed over the interdigital transducer electrode
Data Source
AI summary
Aspects of this disclosure relate to an acoustic wave device with transverse mode suppression. The acoustic wave device can include a piezoelectric layer, an interdigital transducer electrode, a temperature compensation layer, and a multi-layer mass loading strip. The mass loading strip has a density that is higher than a density of the temperature compensation layer. The mass loading strip can overlap edge portions of fingers of the interdigital transducer electrode. The mass loading strip can include a first layer for adhesion and a second layer for mass loading. The mass loading strip can suppress a transverse mode.