Bulk Acoustic Resonator Thickness Tuning for High-Q Miniaturization
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Solution Overview
Problem
Existing acoustic wave devices using piezoelectric layers face challenges in maintaining a high Q value and adjusting resonant frequency while being miniaturized, particularly when reducing the number of electrode fingers.
Innovation Solution
The acoustic wave device employs a bulk wave of a thickness slip first-order mode with first and second electrodes facing each other in a direction crossing the thickness direction of the piezoelectric layer, featuring first and second resonators with different thicknesses and a cavity beneath the resonator to enhance electromechanical coupling, allowing for miniaturization without compromising Q value and resonant frequency adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of electrode fingers is reduced to miniaturize the device, then the device size is reduced, but the Q value is lowered
Solution Approach 1:
The invention transitions from surface wave propagation to bulk wave propagation in the thickness direction of the piezoelectric layer. By utilizing the thickness dimension for wave propagation and introducing thickness variations in the piezoelectric layer, the device achieves miniaturization in the planar direction while maintaining high Q values through the bulk wave resonance mechanism that is less sensitive to electrode finger count reduction.
Solution Approach 2:
The invention changes the resonance mode from surface waves to bulk waves of thickness slip mode, and introduces thickness variation as a key parameter for resonator differentiation. This parameter change enables the device to maintain high Q values with fewer electrode fingers by exploiting the thickness dimension for wave confinement and resonance.
2Volume of moving object
If the number of electrode fingers is reduced to miniaturize the device, then the device size is reduced, but the resonant frequency adjustment becomes difficult
Solution Approach 1:
The invention introduces local thickness variations in the piezoelectric layer for different resonators. Each resonator has a specific thickness setting portion that locally modifies the wave propagation characteristics, enabling independent resonant frequency adjustment for each resonator without affecting other parts of the device. This local quality approach allows frequency tuning while maintaining the miniaturized structure.
Solution Approach 2:
The invention uses thickness variation as the primary parameter for resonant frequency control. By changing the thickness of the piezoelectric layer in specific regions, the resonant frequency of each resonator can be adjusted independently. This parameter change mechanism provides versatility in frequency adjustment without requiring changes in the number of electrode fingers or overall device size.
3Adaptability or versatility
If resonators with different thicknesses are introduced to adjust resonant frequency, then the resonant frequency is adjustable, but the device complexity increases
Solution Approach 1:
The invention segments the piezoelectric layer into multiple resonators with different thicknesses in the thickness direction. Each resonator is defined by its specific thickness setting portion, creating vertically segmented functional units. This segmentation approach allows frequency adjustment through thickness variation while maintaining a relatively simple planar structure and electrode configuration, thus limiting the increase in overall device complexity.
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 increased Q value and adjustable resonant frequency even in a miniaturized form, improving the performance of acoustic wave devices.
Implementation Method 1
acoustic wave devices using plate waves propagating through piezoelectric layers made of LiNbO3 or LiTaO3
Implementation Method 2
The acoustic wave device utilizes a bulk wave of a thickness slip first-order mode
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer and first and second electrodes facing each other in a direction crossing a thickness direction of the piezoelectric layer. The acoustic wave device utilizes a bulk wave of a thickness slip first-order mode. The acoustic wave device includes first and second resonators. Each of the first and second resonators includes the first and second electrodes, and a setting portion including a setup region where the first and second electrodes are provided in the piezoelectric layer. The thickness of each of the first and second resonators excludes the thickness of the first and second electrodes included in the resonator. The thickness of the first resonator is different from the thickness of the second resonator.