Elastic Wave Device Multilayer Electrode Trade-off
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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 in the IDT electrode deteriorates the frequency temperature characteristic and does not substantially increase the fractional bandwidth.
Innovation Solution
The elastic wave device incorporates a piezoelectric substrate made of lithium niobate with an IDT electrode comprising a first electrode layer of Mo or W and a second electrode layer of Cu, where the film thicknesses of these layers are optimized to improve the trade-off relationship between frequency temperature characteristic and fractional bandwidth, with specific equations and combinations of film thicknesses and Euler Angles of the substrate to enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the film thickness of the Al layer in the IDT electrode is increased to lower electrical resistance, then the electrical resistance decreases, but the frequency temperature characteristic deteriorates and the fractional bandwidth is not substantially increased
Solution Approach 1:
The patent applies composite materials by using a multilayer electrode structure consisting of Mo/W layer and Cu layer instead of a single Al layer. The Mo/W layer provides good frequency temperature characteristics while the Cu layer provides low electrical resistance, achieving a combination of properties that neither material alone could provide.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different layers of the electrode structure. The Mo/W layer (first electrode layer) is optimized for frequency temperature characteristic with specific thickness ratios, while the Cu layer (second electrode layer) is optimized for electrical conductivity, allowing each layer to excel at its specific function.
2Reliability
If the film thickness of the dielectric film made of silicon oxide is increased to improve frequency temperature characteristic, then the frequency temperature characteristic improves, but the fractional bandwidth is narrowed
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness ratio of the Mo/W layer relative to the dielectric film thickness. By controlling the first electrode layer thickness to be 0.03λ≤h1/λ<0.07 and the second electrode layer thickness to be 0.02λ≤h2/λ<0.05, the patent achieves a balance where the fractional bandwidth is effectively increased while maintaining good frequency temperature characteristics.
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 increases the fractional bandwidth while maintaining or improving the frequency temperature characteristic, reducing electrical resistance and preventing damage to the piezoelectric substrate, and minimizes spurious SH waves.
Implementation Method 1
the elastic wave device utilizes Rayleigh waves propagating along the piezoelectric substrate
Implementation Method 2
the piezoelectric substrate is made of lithium niobate, an IDT electrode is provided on the piezoelectric substrate
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate, an IDT electrode including a first electrode layer located on the piezoelectric substrate and including one of Mo and W as a main component and a second electrode layer laminated on the first electrode layer and including Cu as a main component, and a dielectric film located on the piezoelectric substrate and covering the IDT electrode. The piezoelectric substrate is made of lithium niobate. The dielectric film is made of silicon oxide. The elastic wave device utilizes Rayleigh waves propagating along the piezoelectric substrate.