Embedded-Electrode Acoustic Wave Structure for High Q and Capacitance
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Solution Overview
Problem
Existing acoustic wave devices face challenges in achieving size reduction while maintaining high Q-value and capacitance, particularly when reducing the number of electrode fingers in piezoelectric substrates like LiNbO3 or LiTaO3.
Innovation Solution
The acoustic wave device incorporates a piezoelectric layer made of lithium niobate or lithium tantalate, with electrodes embedded within the layer, and utilizes a bulk wave in a thickness-shear primary mode, featuring an acoustic reflection layer to enhance wave confinement and increase Q-value and capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the number of first electrode fingers and second electrode fingers is decreased to achieve size reduction, then the device size is reduced, but the Q-value is decreased
Solution Approach 1:
The patent transitions from planar surface electrodes to three-dimensional embedded electrodes within the piezoelectric layer. By embedding electrodes in the thickness direction of the piezoelectric layer, the device achieves size reduction in the planar dimensions while maintaining effective electrode interaction with the acoustic wave, thereby preserving Q-value despite reduced device footprint.
Solution Approach 2:
The electrodes are nested within the piezoelectric layer rather than being placed on the surface. This nesting approach allows the electrodes to be integrated into the bulk of the piezoelectric material, reducing the overall device size while maintaining the necessary electrode-piezoelectric interaction for high Q-value operation.
2Volume of moving object
If the number of first electrode fingers and second electrode fingers is decreased to achieve size reduction, then the device size is reduced, but the capacitance is decreased
Solution Approach 1:
By moving electrodes from surface mounting to embedded positioning within the piezoelectric layer thickness, the patent increases the effective capacitance-generating interface area without increasing planar device dimensions. This dimensional transition allows capacitance to be maintained or increased while achieving size reduction.
Solution Approach 2:
The patent changes the geometric parameter of electrode positioning from surface-level to embedded depth within the piezoelectric layer. This parameter change increases the effective interaction volume between electrodes and piezoelectric material, thereby increasing capacitance while reducing overall device size.
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 increased Q-value and capacitance while achieving size reduction, improving acoustic wave device performance.
Implementation Method 1
a bulk wave in a thickness-shear primary mode is utilized. A material of the piezoelectric layer is lithium niobate or lithium tantalate.
Implementation Method 2
The acoustic wave device further includes an acoustic reflection layer. The piezoelectric layer is on the acoustic reflection layer.
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer and first and second electrodes facing each other in a direction intersecting a thickness direction of the piezoelectric layer. The acoustic wave device utilizes a bulk wave in a thickness-shear primary mode. A material of the piezoelectric layer is lithium niobate or lithium tantalate. At least a portion of each of the first and second electrodes is embedded in the piezoelectric layer.