Dielectric Film Acoustic Wave Structure for Bulk Wave Suppression
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Solution Overview
Problem
Existing acoustic wave devices using piezoelectric films of LiNbO3 or LiTaO3 suffer from unwanted bulk waves that cause ripples in frequency characteristics due to reflections and extractions by support bodies and facing wires, leading to degraded performance.
Innovation Solution
Incorporating a dielectric film between at least one of the first and second electrode films and the piezoelectric layer to alter the electromechanical coupling coefficient, thereby reducing or preventing the influence of unwanted bulk waves and ripples in frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric substrate is used to generate Lamb waves, then acoustic wave resonance is achieved, but unwanted bulk waves are excited and cause ripples in frequency characteristics
Solution Approach 1:
A dielectric film is introduced as an intermediary layer between the piezoelectric substrate and the electrode films. This dielectric film acts as a mediator that modifies the electromechanical coupling coefficient, thereby suppressing the excitation of unwanted bulk waves while maintaining the desired Lamb wave resonance. The dielectric film with specific permittivity and thickness controls the electric field distribution to prevent bulk wave generation.
Solution Approach 2:
The invention changes the electromechanical coupling coefficient by introducing a dielectric film with specific material parameters (permittivity, thickness). This parameter modification alters the wave propagation characteristics, suppressing bulk waves while maintaining Lamb wave resonance. The dielectric film's physical and electrical parameters are optimized to achieve the desired filtering effect.
2Ease of manufacture
If wires connected to different potentials face each other, then electrical connection is achieved, but signals of unwanted bulk waves are extracted causing ripples in frequency characteristics
Solution Approach 1:
The dielectric film serves as an intermediary that prevents the direct extraction of bulk wave signals by the facing wires. By modifying the electric field distribution and electromechanical coupling, the dielectric film ensures that the wires primarily detect desired Lamb wave signals while minimizing sensitivity to unwanted bulk waves, thus eliminating ripples in frequency characteristics.
3Reliability
If busbars are used for electrical connection, then conductivity is achieved, but unwanted bulk wave signals are extracted causing frequency characteristic degradation
Solution Approach 1:
The dielectric film acts as a mediator between the busbars and the piezoelectric substrate, controlling the interaction between the electrical fields and acoustic waves. This intermediary layer modifies the electromechanical coupling to prevent busbars from extracting unwanted bulk wave signals, thereby maintaining clean frequency characteristics while preserving necessary electrical conductivity.
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
The dielectric film effectively minimizes the impact of unwanted bulk waves on frequency characteristics, resulting in improved reflection and resonance performance by altering the propagation and extraction of these waves.
Implementation Method 1
Incorporating a dielectric film between at least one of the first and second electrode films and the piezoelectric layer to alter the electromechanical coupling coefficient, thereby reducing or preventing the influence of unwanted bulk waves
Data Source
AI summary
An acoustic wave device includes a support substrate, a piezoelectric layer on the support substrate, a functional electrode on the piezoelectric layer, first and second electrode films on the piezoelectric layer, facing each other, and having different electric potentials from each other, and a dielectric film between at least one of at least a portion of the first electrode film and the piezoelectric layer and at least a portion of the second electrode film and the piezoelectric layer.