LiNbO3 SAW Element Structure for Stable Band Width Ratios
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Solution Overview
Problem
Variations in band width ratios occur in surface acoustic wave elements due to manufacturing process variations in dielectric layer thickness, affecting their performance in mobile communication devices.
Innovation Solution
A surface acoustic wave element using a LiNbO3 piezoelectric single crystal substrate with a Y-cut angle between 100° and 160°, a thin first dielectric layer, and a thicker second dielectric layer, propagating high-frequency signals as Rayleigh waves to reduce variations in band width ratios, with the maximum amplitude generation position spaced away from the substrate and first dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dielectric layer is provided on the substrate to adjust the electromechanical coupling coefficient, then the band width ratio can be determined, but variations in the thickness of the dielectric layers during manufacturing cause variations in the band width ratio
Solution Approach 1:
The patent extracts the function of band width adjustment from the first dielectric layer by introducing a second dielectric layer. The first dielectric layer is made extremely thin (1-10 nm) and primarily serves as an adhesion layer, while the second dielectric layer (50-200 nm) provides the actual band width adjustment function. This separation allows the first dielectric layer's thickness variations to have minimal impact on band width ratio, as the critical function is transferred to the second layer where thickness control is less critical.
Solution Approach 2:
The patent changes the thickness parameter of the first dielectric layer to an extremely thin range (1-10 nm), making it insensitive to typical manufacturing variations. By making the layer so thin that it primarily functions as an adhesion layer rather than a functional dielectric layer, the design eliminates the sensitivity to thickness variations that plagues conventional designs with thicker first dielectric layers.
2Manufacturing precision
If the first dielectric layer is made thinner to reduce thickness variations, then the electromechanical coupling coefficient adjustment capability is reduced
Solution Approach 1:
The patent extracts the electromechanical coupling coefficient adjustment function from the first dielectric layer and assigns it to the second dielectric layer. The first dielectric layer is reduced to a thin adhesion layer (1-10 nm) that does not significantly affect the coupling coefficient, while the second dielectric layer (50-200 nm) provides the necessary coupling adjustment through its greater thickness and dielectric properties.
Solution Approach 2:
The patent uses a composite dielectric layer structure where the first dielectric layer (1-10 nm) provides adhesion and the second dielectric layer (50-200 nm) provides electromechanical coupling adjustment. This composite structure combines the advantages of both thin layers (good adhesion, minimal thickness variation impact) and thick layers (adequate coupling coefficient adjustment) in a single integrated design.
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 variations in band width ratios, enhancing the stability and performance of surface acoustic wave elements by increasing the electromechanical coupling coefficient and positioning the maximum amplitude generation away from the substrate and first dielectric layer, thereby minimizing the impact of manufacturing thickness variations.
Implementation Method 1
a substrate including a LiNbO3 piezoelectric single crystal
Implementation Method 2
a high-frequency signal is propagated on the substrate using a Rayleigh wave
Data Source
AI summary
A surface acoustic wave element includes a substrate including a LiNbO3 piezoelectric single crystal, a first dielectric layer provided on the substrate, and an IDT electrode provided on the first dielectric layer, and propagates a high-frequency signal on the substrate using a Rayleigh wave.