Divided Acoustic Wave Resonators for High-Q Miniaturization
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Solution Overview
Problem
Acoustic wave devices using piezoelectric layers face challenges in maintaining a high Q factor and strength when the size is reduced, as decreasing the number of electrode fingers leads to decreased Q factor and reduced substrate strength.
Innovation Solution
The acoustic wave device employs a bulk wave in a thickness shear primary mode with a piezoelectric layer of lithium niobate or lithium tantalate, featuring a configuration with first and second divided resonators connected in series or parallel, and a support substrate with energy confinement layers to maintain strength and increase Q factor, even when the device size is reduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of electrode fingers is decreased to reduce device size, then the device size is reduced, but the Q factor decreases
Solution Approach 1:
The resonator is divided into multiple divided resonators (first divided resonator, second divided resonator, etc.) that are connected in series or parallel. Each divided resonator contains electrode portions that collectively provide the necessary Q factor while allowing compact arrangement. This segmentation enables maintaining high Q factor through multiple resonant elements rather than requiring a large number of electrode fingers in a single resonator structure.
Solution Approach 2:
The patent utilizes the thickness direction of the piezoelectric layer to arrange multiple divided resonators vertically stacked or closely spaced. By exploiting the thickness dimension, the device achieves compact planar size while maintaining adequate Q factor through multiple resonant elements arranged in the thickness direction rather than spreading them out in the planar direction.
2Volume of moving object
If the piezoelectric substrate is made thin to reduce device size, then the device size is reduced, but the strength is not ensured
Solution Approach 1:
The patent employs a composite structure consisting of the piezoelectric layer, support substrate, and energy confinement layers. This composite construction provides mechanical strength through the support substrate and energy confinement layers while maintaining thin piezoelectric layer thickness for miniaturization. The combined structure ensures adequate strength despite the thin piezoelectric substrate.
Solution Approach 2:
The support substrate acts as an intermediary element that provides mechanical strength and stability to the thin piezoelectric layer. The energy confinement layers also serve as intermediary structures that both confine acoustic energy and provide structural support. These intermediary elements enable the thin piezoelectric substrate to maintain adequate strength without requiring increased thickness.
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 allows for a higher Q factor and maintained strength in acoustic wave devices, even when the size is minimized, by dispersing ripples and improving linearity through the use of energy confinement layers and specific electrode arrangements.
Implementation Method 1
The acoustic wave device uses a bulk wave in a thickness shear primary mode. A material for the piezoelectric layer is lithium niobate or lithium tantalate.
Data Source
AI summary
An acoustic wave device further includes a piezoelectric layer and first and second electrodes, first and second divided resonators, and a support substrate. The support substrate includes first and second energy confinement layers. The first energy confinement layer overlaps at least a portion of a first region of the piezoelectric layer. The second energy confinement layer overlaps at least a portion of a second region of the piezoelectric layer. The support substrate includes a wall portion between the first and second energy confinement layers.