Acoustic Wave Resonator Structure for Lower Passband Spuriouss
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Solution Overview
Problem
Acoustic wave devices face issues with frequency characteristics deterioration due to large spurious emissions in the pass band, as seen in existing technologies.
Innovation Solution
The acoustic wave device incorporates a support substrate with an intermediate layer having a void portion and a surface roughness of at least 0.0055 μm, along with a piezoelectric layer and IDT electrodes, to reduce spurious emissions by utilizing bulk waves of the first-order thickness-shear mode and optimizing the center-to-center distance and metallization ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional acoustic wave device structures are used, then device simplicity is maintained, but spurious emissions in the pass band increase causing frequency characteristics deterioration
Solution Approach 1:
The intermediate layer is designed with a void portion that extends from the surface toward the support substrate, creating a porous structure. This porous configuration reduces spurious emissions by modifying acoustic wave propagation characteristics while maintaining device functionality.
Solution Approach 2:
The void portion in the intermediate layer is positioned at a specific depth from the surface, creating a three-dimensional structure that affects acoustic wave behavior. By controlling the depth and dimensions of the void, the invention reduces spurious emissions through spatial configuration rather than material composition changes.
2Volume of moving object
If device size is reduced, then integration density improves, but Q factor may decrease
Solution Approach 1:
The invention optimizes specific parameters including the void portion depth (0.5-2.0 μm), surface roughness (0.003-0.03 μm), and piezoelectric layer thickness to maintain high Q factor while reducing overall device size. These parameter adjustments enable miniaturization without compromising resonator performance.
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 effectively reduces spurious emissions in the pass band, maintains good resonance characteristics, and allows for device size reduction without decreasing the Q factor.
Implementation Method 1
a piezoelectric layer on the intermediate layer, and an IDT electrode including a first electrode finger at the piezoelectric layer in the first direction
Implementation Method 2
The intermediate layer includes a void portion at least partially overlapping the IDT electrode in plan view, and a surface roughness of an inner sidewall of the intermediate layer is about 0.0055 μm or more
Data Source
AI summary
An acoustic wave device includes a support substrate with a thickness in a first direction, an intermediate layer on the support substrate, a piezoelectric layer on the intermediate layer, and an IDT electrode including a first electrode finger at the piezoelectric layer in the first direction and extending in a second direction intersecting the first direction, a first busbar electrode connected to the first electrode finger, a second electrode finger facing the first electrode finger in a third direction orthogonal or substantially orthogonal to the second direction and extending in the second direction, and a second busbar electrode connected to the second electrode finger. The intermediate layer includes a void portion at least partially overlapping the IDT electrode in plan view, and a surface roughness of an inner sidewall of the intermediate layer is about 0.0055 μm or more.