SAW Filter Electrode Stack for Power Handling and Spurious Wave Suppression
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Solution Overview
Problem
Existing surface acoustic wave devices face challenges in maintaining excellent electric power handling capability and linearity while effectively suppressing unnecessary waves, particularly due to stress applied to auxiliary conductive layers and inadequate suppression of unnecessary waves.
Innovation Solution
The surface acoustic wave device incorporates a piezoelectric substrate of θ° rotated Y-cut X-propagation LiNbO3 with an IDT electrode structure that includes a main electrode layer with Pt, Au, or W as the main component, positioned closer to the piezoelectric substrate than the auxiliary conductive layer. The film thickness of the main electrode layer is optimized within specific ranges to satisfy certain mathematical relationships, ensuring reduced stress on the auxiliary conductive layer and effective suppression of unnecessary waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the auxiliary conductive layer is arranged on the side of the piezoelectric substrate to lower electric resistance, then the electric resistance of the IDT electrode is reduced, but the electric power handling capability and linearity deteriorate due to stress applied to the auxiliary conductive layer
Solution Approach 1:
The patent inverts the conventional layer arrangement by placing the main electrode layer (Pt, Au, or W) closer to the piezoelectric substrate and the auxiliary conductive layer (Al) farther away. This inversion resolves the contradiction by protecting the auxiliary conductive layer from stress while maintaining its resistance-lowering function, thereby improving electric power handling capability and linearity
2Reliability
If a metal film with relatively high density is arranged on the side of the piezoelectric substrate, then the electromechanical coupling coefficient increases, but unnecessary waves are not sufficiently suppressed due to incorrect distance from the substrate
Solution Approach 1:
The patent applies parameter changes by optimizing the film thickness of the main electrode layer within specific ranges (0.05λ≤h/λ≤0.15 for Pt, 0.06λ≤h/λ≤0.16 for Au, 0.07λ≤h/λ≤0.17 for W) and positioning it at a specific distance from the piezoelectric substrate. This resolves the contradiction by achieving both high electromechanical coupling coefficient and effective suppression of unnecessary waves through precise parameter control
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 enhances the electric power handling capability and linearity of the surface acoustic wave device while effectively reducing or preventing unnecessary waves, thereby improving the device's performance and reliability.
Implementation Method 1
a piezoelectric substrate made of θ° rotated Y-cut X-propagation LiNbO3
Data Source
AI summary
A surface acoustic wave device includes a piezoelectric substrate made of θ° rotated Y-cut X-propagation LiNbO3 having a cut angle θ, an IDT electrode on the piezoelectric substrate and including a plurality of electrode fingers, and a dielectric film on the piezoelectric substrate and covering the IDT electrode. The IDT electrode includes a main electrode layer and an auxiliary conductive layer. The main electrode layer is, compared to the auxiliary conductive layer, closer to a side of the piezoelectric substrate. The main electrode layer includes Pt as a main component. Where the film thickness of the main electrode layer is denoted as h, the film thickness of the dielectric film is denoted as H, and a wavelength determined by the electrode finger pitch of the IDT electrode is denoted as λ, the relationship in Formula (1) and Equation (2A) to Equation (2D) is satisfied.