Multilayer SAW Piezoelectric Structure for Multi-Band k2 and TCF Tuning
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Solution Overview
Problem
Current multilayer piezoelectric substrate (MPS) surface acoustic wave (SAW) devices face challenges in achieving optimal electrical properties such as coupling factor k2 and temperature coefficient of frequency (TCF) across multiple frequency bands, due to the limitations of single piezoelectric layer configurations.
Innovation Solution
The implementation of a multilayer piezoelectric substrate with multiple piezoelectric layers of varying thicknesses and cut angles, including a sloped region between regions of different thicknesses, enhances the electrical properties by optimizing the coupling factor k2 and TCF, and reduces unwanted acoustic reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single piezoelectric layer configuration is used, then the device structure is simple, but the electrical properties (coupling factor k2 and TCF) cannot be optimized across multiple frequency bands
Solution Approach 1:
The piezoelectric layer is segmented into multiple distinct layers (first piezoelectric layer and second piezoelectric layer) with different thicknesses and/or materials. Each layer can be independently optimized for specific frequency bands, enabling multi-band operation while maintaining manageable structural complexity through systematic layering
Solution Approach 2:
Different regions of the piezoelectric structure have different local properties - the first piezoelectric layer and second piezoelectric layer have different thicknesses and/or material compositions tailored for different frequency ranges. This local differentiation allows each layer to contribute optimally to specific frequency bands, achieving versatile electrical properties across multiple bands
2Reliability
If the piezoelectric layer thickness is increased to improve coupling factor, then the coupling factor k2 improves, but acoustic reflections increase
Solution Approach 1:
The piezoelectric layer is divided into multiple segments (first piezoelectric layer and second piezoelectric layer) with different thicknesses. This segmentation allows the total piezoelectric thickness to be distributed across layers, maintaining high coupling factor while reducing unwanted acoustic reflections that would occur with a single thick layer
Solution Approach 2:
The thickness parameter of the piezoelectric layer is changed and differentiated across multiple layers. By having the first piezoelectric layer with a first thickness and the second piezoelectric layer with a second thickness, the structure optimizes coupling factor while controlling acoustic reflections through parameter variation rather than uniform thickness
3Reliability
If multiple piezoelectric layers with varying thicknesses are implemented, then electrical properties are optimized and acoustic reflections are reduced, but the manufacturing complexity increases
Solution Approach 1:
The piezoelectric structure is segmented into multiple manufacturable layers that can be fabricated using standard semiconductor processing techniques. Each layer can be deposited, patterned, and etched independently, allowing complex multi-layer structures to be manufactured through sequential processing steps that are already established in the industry
Solution Approach 2:
The manufacturing process accommodates local quality variations by enabling different thicknesses and material properties in different layers. Standard fabrication techniques such as selective epitaxial growth, chemical vapor deposition, and controlled etching allow precise local thickness control in each piezoelectric layer, making the complex structure manufacturable with existing technology
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 approach allows for improved electrical properties and reduced size in multi-band SAW filters, enabling efficient signal separation across multiple frequency bands while minimizing acoustic reflections.
Implementation Method 1
a piezoelectric structure including a first region having a first thickness, a second region having a second thickness different from the first thickness, and a third region sloped between the first region and the second region; a first surface acoustic wave element positioned in the first region; and a second surface acoustic wave element positioned in the second region
Data Source
AI summary
A surface acoustic wave device is disclosed. The surface acoustic wave device can include a support substrate structure, a first piezoelectric layer over the support substrate structure, a second piezoelectric layer over the first piezoelectric layer, a first acoustic wave element in electrical communication with the first piezoelectric layer, and a second acoustic wave element in electrical communication with the second piezoelectric layer.