Dual-Sided IDT Acoustic Wave Layout With Asymmetric Dielectric Loading
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Acoustic wave devices with interdigital transducer electrodes on both surfaces of a piezoelectric film often generate spurious higher-order modes due to asymmetric stress distribution and mass loads, which affect the coupling coefficient and impedance characteristics.
Innovation Solution
The implementation of an acoustic wave device with energy confinement layers and dielectric films on specific surfaces of the piezoelectric film, where the dielectric films have bulk wave acoustic velocities either lower or higher than the piezoelectric film, and the total product of density and film thickness of electrode fingers is adjusted to minimize higher-order mode occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If IDT electrodes are provided on both surfaces of a piezoelectric film, then the coupling coefficient is improved, but spurious higher-order modes are generated due to asymmetric stress distribution and mass loads
Solution Approach 1:
The patent applies asymmetry by providing different dielectric film configurations on the first and second main surfaces of the piezoelectric film. Specifically, a first dielectric film is provided on the first main surface while a second dielectric film with different properties (acoustic velocity, density, or thickness) is provided on the second main surface. This asymmetric configuration balances the stress distribution and mass loads, suppressing spurious higher-order modes while maintaining the dual-surface IDT electrode structure for high coupling coefficient
Solution Approach 2:
The patent utilizes parameter changes by carefully selecting and adjusting the acoustic velocity, density, and thickness parameters of the dielectric films on either side of the piezoelectric film. By controlling these parameters such that the product of density and film thickness differs between the two surfaces, the patent optimizes the stress and mass load distribution to eliminate higher-order modes while preserving the beneficial coupling effects of the dual-surface IDT configuration
2Object-generated harmful factors
If energy confinement layers are added to suppress higher-order modes, then spurious responses are reduced, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by designing the dielectric films to serve dual purposes: they provide electrical insulation for the IDT electrodes and simultaneously function as stress-balancing layers that suppress higher-order modes. This eliminates the need for separate energy confinement layers, reducing device complexity while still achieving spurious response suppression
Solution Approach 2:
The patent merges the insulation function and the stress-balancing function into a single integrated structure. The dielectric films on the first and second main surfaces are configured to simultaneously provide electrical isolation and control stress distribution, combining multiple functions that could otherwise require separate components into one unified design
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 suppresses higher-order modes, improving the symmetry of stress distribution and reducing the coupling coefficient, thereby enhancing the acoustic wave device's performance by minimizing spurious responses and maintaining efficient energy confinement.
Implementation Method 1
a piezoelectric film (3) that includes a first main surface (3a) and a second main surface (3b) that face each other
Implementation Method 2
the first and second dielectric films have a bulk wave acoustic velocity lower than an acoustic velocity of the acoustic wave propagating through the piezoelectric film or a bulk wave acoustic velocity higher than the acoustic velocity of the acoustic wave propagating through the piezoelectric film
Data Source
AI summary
An acoustic wave device includes a piezoelectric film on an energy confinement layer, an IDT electrode and a first dielectric film on a first main surface of the piezoelectric film, a second IDT electrode and a second dielectric film on the second main surface. When a product of a density and a film thickness of the second dielectric film on a side of the second main surface is larger than that of the first dielectric film on the first main surface side, a total sum of a product of a density and a film thickness of an electrode finger of the first IDT electrode covered with the first dielectric film is smaller than a total sum of a product of a density and a film thickness of an electrode finger of the second IDT electrode.