SAW Piezoelectric Layer Thickness Layout to Limit Wave Leakage
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Solution Overview
Problem
Existing surface acoustic wave (SAW) devices face challenges in achieving high quality factor (Q), large effective electromechanical coupling coefficient (k2), and high-power durability while reducing device size, particularly when the interdigital transducer (IDT) electrode is embedded, leading to wave leakage and degraded performance.
Innovation Solution
The SAW device incorporates an IDT electrode with partially buried fingers and bus bars, where the fingers are positioned below the surface of the piezoelectric layer in the active region, and bus bars are on the surface, with varying thicknesses and recessed patterns to mitigate wave leakage and improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the IDT electrode is fully embedded in the piezoelectric layer, then the device size is reduced, but wave leakage occurs and performance degrades
Solution Approach 1:
The patent applies local quality by differentiating the positioning of different IDT electrode components: fingers are embedded below the surface in the active region to reduce device size, while bus bars remain on the surface to prevent wave leakage. This localized differentiation resolves the contradiction by optimizing each component's position for its specific function.
Solution Approach 2:
The IDT electrode is segmented into distinct functional parts (fingers and bus bars) with different positioning strategies. The fingers are embedded while the bus bars are not, allowing the structure to simultaneously achieve size reduction and performance maintenance through functional segmentation.
2Volume of moving object
If the IDT electrode is fully embedded in the piezoelectric layer, then the device size is reduced, but the quality factor decreases due to wave leakage
Solution Approach 1:
By making the bus bars surface-level rather than embedded, the patent locally modifies the electrode structure where wave generation occurs. This prevents wave leakage and maintains high quality factor while the embedded fingers still achieve size reduction.
3Volume of moving object
If the IDT electrode is fully embedded in the piezoelectric layer, then the device size is reduced, but the electromechanical coupling coefficient decreases
Solution Approach 1:
The patent optimizes electromechanical coupling by positioning fingers embedded in the piezoelectric layer where the acoustic wave interacts with the piezoelectric material, maximizing coupling efficiency. The surface-level bus bars maintain this coupling while preventing wave leakage.
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 design enhances the quality factor (Q) and effective electromechanical coupling coefficient (k2) while maintaining high-power durability and reducing device size, effectively addressing the performance degradation issues associated with embedded IDT electrodes.
Implementation Method 1
a piezoelectric layer having a first surface and a second surface opposite the first surface; and an interdigital transducer electrode in electrical communication with the piezoelectric layer, the interdigital transducer electrode including a bus bar and fingers extending from the bus bar, the fingers being at least partially positioned below the first surface and at least partially positioned over the first surface
Data Source
AI summary
A surface acoustic wave device and a method of forming the surface acoustic wave device are disclosed. The surface acoustic wave device can include a piezoelectric layer with a bus bar region having a first thickness and a finger region having a second thickness less than the first thickness. The surface acoustic wave device can include an interdigital transducer electrode in electrical communication with the piezoelectric layer. The interdigital transducer electrode includes a bus bar and fingers that extend from the bus bar. The bus bar is positioned in the bus bar region and the fingers are positioned in the finger region.