Boundary Acoustic Wave Layer Structure for Stronger Interface Coupling
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Solution Overview
Problem
Conventional boundary acoustic wave devices fail to concentrate acoustic waves effectively at the interface between LiNbO3 and SiO2 layers, limiting their electro-mechanical coupling coefficient due to differences in displacement areas and wave propagation speeds.
Innovation Solution
A boundary acoustic wave device structure with a first medium layer of LiNbO3, a second medium layer of SiO2, and a third medium layer formed by doping elements in the LiNbO3 base material, where the transverse wave propagation speeds are adjusted to concentrate displacement at the interface between the second and third layers, enhancing the electro-mechanical coupling coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional boundary acoustic wave device uses LiNbO3 and SiO2 layers with IDT electrode at their interface, then the device structure is simple and easy to manufacture, but the acoustic wave displacement area in SiO2 is larger than in LiNbO3, preventing the acoustic wave from concentrating at the interface and limiting the electro-mechanical coupling coefficient
Solution Approach 1:
The patent introduces a third medium layer with specifically controlled acoustic wave propagation speed parameters. This layer's propagation speed is designed to be between that of LiNbO3 and SiO2, creating a gradient that concentrates acoustic wave displacement at the LiNbO3-SiO2 interface. This parameter-based approach enhances the electro-mechanical coupling coefficient without complicating the overall device structure
Solution Approach 2:
The patent creates a composite multi-layer structure combining LiNbO3, SiO2, and a third medium layer with intermediate acoustic properties. This composite structure leverages the complementary characteristics of each layer: LiNbO3 provides strong piezoelectric effect, SiO2 provides acoustic isolation, and the third layer provides gradient transition, collectively achieving superior electro-mechanical coupling
2Device complexity
If the acoustic wave displacement area in SiO2 is larger than in LiNbO3, then the device structure is straightforward, but the acoustic wave cannot concentrate at the interface, reducing the electro-mechanical coupling coefficient and device performance
Solution Approach 1:
By introducing a third medium layer with intermediate acoustic propagation speed, the patent creates a controlled parameter gradient that redirects acoustic wave energy concentration to the LiNbO3-SiO2 interface. This parameter optimization enhances the electro-mechanical coupling coefficient while maintaining a relatively simple five-layer device structure
Solution Approach 2:
The third medium layer acts as an intermediary between LiNbO3 and SiO2, providing a transition zone with intermediate acoustic properties. This intermediary layer guides the acoustic wave energy flow and concentrates displacement at the desired interface, thereby enhancing device performance without requiring complex structural modifications
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 achieves a large electro-mechanical coupling coefficient, improving the performance of boundary acoustic wave devices by concentrating wave displacement at the interface, thereby enhancing their efficiency and sensitivity, particularly in electronic applications like mobile telephones.
Implementation Method 1
an SH type boundary acoustic wave as a main mode propagates along interface 501A between medium layers 1 and 2
Data Source
AI summary
A boundary acoustic wave device includes a first medium layer made of piezoelectric material, a second medium layer provided on the first medium layer, a third medium layer provided on the second medium layer, and an electrode provided at an interface between the second and third medium layers. The electrode drives the third medium layer to generate a transverse wave. A propagation speed of the transverse wave in the third medium layer is lower than a propagation speed of the transverse wave in the first medium layer. A propagation speed of the transverse wave in the second medium layer is lower than the propagation speed of the transverse wave in the first medium layer. This boundary acoustic wave device has a large electro-mechanical coupling coefficient.