Acoustic Wave Resonator Edge Mass Loading for Transverse Mode Reduction
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Solution Overview
Problem
Acoustic wave devices with multiple resonators often face challenges in reducing transverse modes effectively, which can lead to reduced productivity due to the need for individual adjustments of each resonator.
Innovation Solution
The acoustic wave device incorporates a first and second acoustic wave resonator sharing a piezoelectric substrate, with specific apodization areas and mass-adding films in the edge areas of the IDT electrodes, allowing for controlled acoustic velocity and reduced transverse modes without compromising productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If individual adjustments are made for each acoustic wave resonator to reduce transverse modes, then the transverse mode reduction is effective, but productivity is reduced
Solution Approach 1:
The IDT electrode is divided into a center area and edge areas, with different structural characteristics in each region. The edge areas have wider electrode fingers or additional mass-adding films compared to the center area, allowing localized control of acoustic velocity to suppress transverse modes while maintaining uniform manufacturing processes for multiple resonators
Solution Approach 2:
Different regions of the IDT electrode are given different local properties: the center area has standard electrode finger width for primary acoustic wave generation, while the edge areas have increased width or mass-adding films to create low acoustic velocity regions that specifically target transverse mode suppression without affecting the overall resonator performance
2Reliability
If mass-adding films are added to reduce transverse modes, then transverse mode reduction is achieved, but device complexity increases
Solution Approach 1:
The mass-adding films are integrated into the existing IDT electrode structure rather than being added as separate components. The films are positioned in the edge areas of the IDT and form a unified structure with the electrode fingers, reducing manufacturing steps and device complexity while achieving transverse mode suppression
Solution Approach 2:
The mass-adding films serve multiple functions: they increase the mass in edge areas to create low acoustic velocity regions for transverse mode suppression, and can also serve as part of the electrode structure itself, combining mass loading and electrical functionality in a single element
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 configuration enables reliable reduction of transverse modes in acoustic wave devices, enhancing their performance without the need for individual adjustments of each resonator, thus maintaining productivity.
Implementation Method 1
an acoustic wave resonator including a piezoelectric substrate, and an IDT electrode including a plurality of electrode fingers located on the piezoelectric substrate
Implementation Method 2
at least one first mass-adding film located in at least one of the first edge area and the second edge area, and overlapping the plurality of electrode fingers of the first IDT electrode in a plan view
Data Source
AI summary
An acoustic wave device includes first and second acoustic wave resonators with first and second IDT electrodes on a common piezoelectric substrate. A first apodization area in the first IDT electrode includes first and second edge areas with a first center area therebetween. A second apodization area in the second IDT electrode includes third and fourth edge areas with a second center area therebetween. At least one first mass-adding film is located in at least one of the first and second edge areas and overlaps the electrode fingers of the first IDT electrode, and at least one second mass-adding film is located in at least one of the third and fourth edge areas and overlaps the electrode fingers of the second IDT electrode. A thickness of the at least one first mass-adding film is equal to a thickness of the at least one second mass-adding film.