Acoustic Wave Layer Stack Using LiTaO3 Film for Bandwidth Control
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Solution Overview
Problem
Existing acoustic wave devices face challenges in adjusting fractional band width without increasing device size due to insufficient dielectric constant of materials like silicon nitride, silicon oxide, tantalum oxide, and silicon oxynitride used in insulating layers.
Innovation Solution
Incorporating a dielectric film with materials such as lithium tantalate (LiTaO3) or lithium niobate (LiNbO3) between the piezoelectric layer and IDT electrodes, where the dielectric film and piezoelectric layer differ in material composition, polarization direction, or both, allowing for adjustable fractional band width without increasing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dielectric film with high dielectric constant (such as lithium tantalate or lithium niobate) is introduced between the piezoelectric layer and IDT electrodes, then the fractional band width can be adjusted without increasing device size, but the device structure becomes more complex
Solution Approach 1:
The dielectric film is nested within the existing layered structure between the piezoelectric layer and IDT electrodes, integrating the high dielectric constant material into the existing device architecture without requiring external additions or significant structural reconfiguration
Solution Approach 2:
The dielectric film is selectively positioned only at specific locations where it is most effective for adjusting fractional band width, rather than uniformly throughout the entire device structure, thereby minimizing overall complexity while achieving the desired electrical characteristics
2Adaptability or versatility
If the thickness of the insulating layer is increased to adjust the fractional band width, then the band width can be controlled, but the device size increases
Solution Approach 1:
Instead of changing the physical thickness parameter of the insulating layer, the invention changes the dielectric constant parameter by introducing a material with higher dielectric constant (lithium tantalate or lithium niobate), thereby achieving the same electrical effect with reduced physical dimensions
Solution Approach 2:
The invention uses a composite structure combining the original insulating layer material with a high dielectric constant material (lithium tantalate or lithium niobate), creating a multi-material system that achieves superior electrical performance in a compact form factor
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 enables easy adjustment of fractional band width while maintaining electrostatic capacitance, reducing unwanted Rayleigh waves, and preventing higher order mode generation, thus optimizing device performance without size increments.
Implementation Method 1
a dielectric film at least provided at one of a position between the first principal surface of the piezoelectric layer and the first IDT electrode and a position between the second principal surface of the piezoelectric layer and the second IDT electrode
Implementation Method 2
the dielectric constant of the above-described materials is not sufficiently high. Because of this, in the acoustic wave device disclosed in International Publication No. 2022/202917, the size of the acoustic wave device is increased when it is attempted to obtain a desired electrostatic capacitance
Implementation Method 3
a piezoelectric layer on the support substrate and including a first principal surface and a second principal surface opposing each other
Data Source
AI summary
An acoustic wave device includes a support substrate, a piezoelectric layer on the support substrate and including first and second principal surfaces, first and second IDT electrodes respectively on the first and second principal surfaces, and a dielectric film at least provided at one of a position between the first principal surface and the first IDT electrode, and a position between the second principal surface and the second IDT electrode. Each of the dielectric film and the piezoelectric layer includes one of Li, Ta, and O or Li, Nb, and O. At least one of a polarization direction, an element included in a material, and a composition of the material is different between the dielectric film and the piezoelectric layer.