Pt-Cu Electrode Elastic Wave Device for Bandwidth and Temperature Trade-off
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing elastic wave devices face a trade-off between frequency temperature characteristic and fractional bandwidth, where increasing the film thickness of the Al layer to lower electrical resistance deteriorates the frequency temperature characteristic and does not substantially widen the fractional bandwidth.
Innovation Solution
The use of a piezoelectric substrate with a Pt-based first electrode layer and a Cu-based second electrode layer, where the film thickness ratio of the second electrode layer to the wavelength is optimized to improve the trade-off relationship between frequency temperature characteristic and fractional bandwidth, and the total film thickness of both electrode layers is kept low to enhance productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the film thickness of the Al layer is increased to lower the electrical resistance of the IDT electrode, then the electrical resistance is reduced, but the frequency temperature characteristic deteriorates and the fractional bandwidth is not substantially widened
Solution Approach 1:
The patent applies composite materials by replacing the single-layer Al electrode with a multi-layer electrode structure consisting of Pt, Ru, and Al layers. This composite structure combines the advantages of different materials: Pt provides low electrical resistance and good adhesion, Ru offers intermediate properties with moderate resistance and thermal stability, and Al contributes to low cost and acceptable resistance. The synergistic effect of these layered materials resolves the contradiction by achieving lower overall electrical resistance while maintaining frequency temperature characteristics through the distributed mass and impedance matching effects of the multiple layers.
2Stability of the object's composition
If the film thickness of the dielectric film made of silicon oxide is increased, then the frequency temperature characteristic is improved, but the fractional bandwidth is narrowed
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the dielectric film and the electrode layers to achieve a balance between frequency temperature characteristic and fractional bandwidth. Specifically, the patent sets the dielectric film thickness to 0.03λ to 0.07λ and the electrode layer total thickness to 0.02λ to 0.06λ, where λ is the wavelength. These parameter optimizations allow the system to achieve acceptable frequency temperature characteristics while maintaining adequate fractional bandwidth, resolving the trade-off through precise dimensional control rather than extreme values.
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 widens the fractional bandwidth while maintaining or improving the frequency temperature characteristic, and reduces the electrical resistance of the IDT electrode, thereby improving the trade-off relationship and manufacturing efficiency.
Implementation Method 1
the piezoelectric substrate is made of lithium niobate and uses Rayleigh waves
Implementation Method 2
the dielectric film is made of silicon oxide and covers the IDT electrode
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate, an IDT electrode including a first electrode layer which is provided on the piezoelectric substrate and contains Pt as a main component and a second electrode layer which is laminated on the first electrode layer and contains Cu as a main component, and a dielectric film that is provided on the piezoelectric substrate and covers the IDT electrode. The piezoelectric substrate is made of lithium niobate. The dielectric film is made of silicon oxide. The elastic wave device uses Rayleigh waves propagating along the piezoelectric substrate.