Acoustic Wave Resonator Layout for Bandwidth Tuning in Limited Area
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Solution Overview
Problem
Acoustic wave devices with existing technologies face challenges in adjusting frequency characteristics and relative bandwidth without increasing device size due to the need for additional capacitances formed on the piezoelectric layer surface.
Innovation Solution
The acoustic wave device incorporates a conductor positioned inside a cavity on the piezoelectric layer's second main surface, facing a busbar with a different electric potential, allowing adjustment of frequency characteristics and relative bandwidth without enlarging the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wiring lines are formed on the piezoelectric layer surface to provide additional capacitances, then frequency characteristics and relative bandwidth can be adjusted, but the device size increases
Solution Approach 1:
The patent moves the additional capacitance structure from the piezoelectric layer surface (2D plane) to the support substrate (3D space below), utilizing the vertical dimension to resolve the area constraint. The conductor is positioned in a cavity within the support, below the piezoelectric layer, allowing capacitance adjustment without occupying surface area.
Solution Approach 2:
The conductor is nested within a cavity in the support substrate, which is itself nested below the piezoelectric layer. This nested configuration allows the additional capacitance structure to be contained within the existing device footprint, eliminating the need to increase device area while providing the required capacitance for frequency adjustment.
2Adaptability or versatility
If wiring lines are formed on the piezoelectric layer surface to provide additional capacitances, then relative bandwidth can be adjusted, but the device size increases
Solution Approach 1:
The patent relocates the bandwidth adjustment mechanism from the surface plane to the vertical dimension by positioning the conductor in a cavity within the support substrate. This allows relative bandwidth adjustment through capacitor coupling without expanding the device footprint.
Solution Approach 2:
The piezoelectric layer acts as an intermediary between the IDT electrode and the conductor in the support cavity. This intermediary structure enables the conductor to provide additional capacitance for bandwidth adjustment while remaining spatially separated from the surface wiring, thus avoiding area increase.
3Area of stationary object
If a conductor is positioned inside a cavity in the support below the piezoelectric layer, then frequency characteristics can be adjusted without increasing device size, but the structure becomes more complex
Solution Approach 1:
The support substrate serves multiple functions: it provides mechanical support for the piezoelectric layer and simultaneously houses the conductor in its cavity to provide additional capacitance. This multi-functionality reduces the need for separate components, thereby limiting the increase in structural complexity despite the three-dimensional configuration.
Solution Approach 2:
The support substrate and the additional capacitance structure are merged into a single integrated component. The cavity in the support both supports the piezoelectric layer and contains the conductor, combining structural and electrical functions into one element to minimize overall device complexity.
4Area of stationary object
If a conductor is positioned inside a cavity in the support below the piezoelectric layer, then relative bandwidth can be adjusted without increasing device size, but the structure becomes more complex
Solution Approach 1:
The support substrate performs dual functions as both the mechanical support structure and the housing for the bandwidth-adjustment capacitor. This universal design allows relative bandwidth adjustment without additional surface area while keeping the overall structural complexity manageable through functional integration.
Solution Approach 2:
The conductor is nested within the support cavity, which is itself nested in the overall device structure. This nested arrangement efficiently utilizes the vertical space within the existing device footprint, enabling bandwidth adjustment without increasing device area while maintaining relatively compact and organized structure.
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 frequency characteristics and relative bandwidth without increasing the device size, while also improving heat dissipation through conductor wiring connections.
Implementation Method 1
a piezoelectric layer including a first main surface and a second main surface that face each other, an IDT electrode on the first main surface of the piezoelectric layer... Thickness-shear mode bulk waves are excited by applying an AC voltage between the electrodes
Implementation Method 2
a conductor on the second main surface of the piezoelectric layer and facing the first busbar with the piezoelectric layer interposed therebetween... An electric potential of the conductor is different from an electric potential to which the first busbar is connected
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer including first and second main surfaces facing each other, an IDT electrode on the first main surface and including first and second busbars facing each other and electrode fingers, a first conductor on the second main surface and facing the first busbar with the piezoelectric layer therebetween, and a support on the second main surface and supporting the piezoelectric layer. A cavity that opens towards the piezoelectric layer is provided in the support, and the first conductor is positioned inside the cavity. An electric potential of the first conductor is different from an electric potential to which the first busbar is connected.