Acoustic Wave Electrode Structure for Stable Characteristics
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Solution Overview
Problem
Acoustic wave devices using LiNbO3 substrates experience shape changes when excited, leading to fluctuations in electrical characteristics and the inability to sufficiently reduce higher-order modes.
Innovation Solution
The acoustic wave device incorporates a support substrate with a piezoelectric layer and embedded second IDT electrode, where the dielectric film thickness is less than or equal to 0.15λ, and the second IDT electrode is embedded in the support substrate, enhancing stability and reducing higher-order modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a LiNbO3 substrate is used to provide piezoelectric properties, then the acoustic wave can be excited, but the shape of the substrate changes significantly during excitation causing fluctuations in electrical characteristics
Solution Approach 1:
The patent applies local quality by using different materials with different mechanical properties in different regions of the support structure. The support substrate uses a material with high elastic modulus to maintain shape stability, while the piezoelectric layer provides the necessary piezoelectric properties for acoustic wave excitation. This localized differentiation allows the support to resist deformation while the piezoelectric layer generates the acoustic waves.
Solution Approach 2:
The patent employs composite materials by combining a support substrate made of a material with high elastic modulus (such as silicon or silicon carbide) with a piezoelectric layer (such as lithium niobate or lithium tantalate). This composite structure leverages the mechanical stability of the support substrate and the piezoelectric properties of the piezoelectric layer to achieve both acoustic wave excitation and shape stability.
2Object-affected harmful factors
If the dielectric film thickness is increased to cover the IDT electrode, then the electrode is protected, but higher-order modes cannot be sufficiently reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the dielectric film to be 0.05λ or less. This specific thickness parameter achieves an optimal balance: it is thick enough to provide adequate coverage and protection of the IDT electrode, yet thin enough to allow the acoustic energy to penetrate through and suppress higher-order modes effectively.
Solution Approach 2:
The patent uses partial action by applying a dielectric film with thickness that is intentionally kept minimal (0.05λ or less) rather than providing complete thick coverage. This partial coverage is sufficient to protect the electrode while avoiding the excessive thickness that would trap higher-order modes.
3Reliability
If the second IDT electrode is embedded in the support, then shape stability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the second IDT electrode embedded in the support substrate before forming the piezoelectric layer. This sequence allows the embedded electrode structure to be established early in the manufacturing process, providing shape stability from the outset, and subsequent layers are built upon this stable foundation.
Solution Approach 2:
The patent uses segmentation by dividing the device into distinct functional layers: the support substrate with embedded second IDT electrode, the piezoelectric layer, and the first IDT electrode on top. This segmented structure allows each layer to be optimized and manufactured separately with specific functions, making the overall complex structure manageable through modular fabrication.
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 stabilizes the electrical characteristics and effectively reduces higher-order modes, improving the device's performance and reliability.
Implementation Method 1
a piezoelectric layer provided on the support substrate and including a first principal surface and a second principal surface facing each other, a first IDT electrode provided on the first principal surface and including a plurality of electrode fingers, and a second IDT electrode provided on the second principal surface
Data Source
AI summary
To provide an acoustic wave device capable of reducing or preventing fluctuations in electrical characteristics and reducing or preventing higher-order modes. An acoustic wave device of the present invention includes a support including a support substrate, a piezoelectric layer provided on the support and having a first principal surface and a second principal surface facing each other, a first IDT electrode provided on the first principal surface and including a plurality of electrode fingers, and a second IDT electrode provided on the second principal surface and including a plurality of electrode fingers. The second IDT electrode is embedded in the support. A dielectric film is provided on the first principal surface of the piezoelectric layer to cover the first IDT electrode. When a wavelength defined by an electrode finger pitch of the first IDT electrode is represented by λ, a thickness of the dielectric film is equal to or less than 0.15λ.