IDT Electrode Width Layout for Low-Spurious Acoustic Wave Devices
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Solution Overview
Problem
Existing acoustic wave devices face issues with uneven membrane strength due to varying electrode finger widths, leading to potential deflection and destruction of the piezoelectric layer under heat or stress, and excessive spurious emissions.
Innovation Solution
The acoustic wave device incorporates a piezoelectric layer with interdigitated transducer (IDT) electrodes featuring electrode fingers of varying widths arranged in specific groups to optimize strength distribution and reduce spurious emissions, utilizing a configuration where the first group has the largest width, the second group the smallest, and the third group a width intermediate between the first and second, arranged in a specific order to manage stress and prevent deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the widths of electrode fingers differ significantly between central region and end portion region to suppress spurious emissions, then spurious emissions are reduced, but the strength of the piezoelectric layer becomes uneven leading to deflection or destruction
Solution Approach 1:
The patent applies local quality by making different parts of the electrode fingers have different widths. Specifically, the electrode fingers are designed with a first width in the central region and a second width at the end portions, where the widths are different. This local variation in geometry allows the central region to suppress spurious emissions while the end portions maintain structural strength and prevent deflection of the piezoelectric layer.
2Ease of manufacture
If the thickness of piezoelectric layer and film thickness of electrode fingers are substantially the same, then manufacturing is simplified, but the influence of width variation becomes more significant causing deflection or destruction
Solution Approach 1:
The patent applies parameter changes by carefully controlling the relationship between the thickness of the piezoelectric layer and the film thickness of the electrode fingers. The thickness of the piezoelectric layer is set to be greater than the film thickness of the electrode fingers, which reduces the influence of width variation on the overall structure. This parameter adjustment maintains manufacturing simplicity while preventing deflection and destruction of the piezoelectric layer.
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 reduces or prevents deflection and destruction of the piezoelectric layer while minimizing spurious emissions, maintaining resonance characteristics and increasing the coupling coefficient.
Implementation Method 1
a piezoelectric layer (2) made of lithium niobate or lithium tantalate
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer, and an IDT electrode including first and second electrodes each including electrode fingers extending in a second direction intersecting a first direction and facing each other. The IDT electrode includes first, second, and third groups of electrode fingers continuously arranged in a third direction. The first group of electrode fingers has a largest first width, the second group of electrode fingers has a smallest second width, and the third group of electrode fingers has a third width that is larger than the second width. The third group of electrode fingers, the second group of electrode fingers, the first group of electrode fingers, the second group of electrode fingers, and the third group of electrode fingers are arranged in this order as viewed in the third direction.