Multi-Layer Raised Frame Layout for Spurious-Mode BAW Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bulk acoustic wave filters face challenges in achieving low insertion loss and low Gamma loss, with raised frame structures often generating spurious modes that cause Gamma degradation in carrier aggregation bands.
Innovation Solution
A multi-layer raised frame structure is introduced, comprising a first raised frame layer with low acoustic impedance, such as silicon dioxide, positioned between electrodes and a second raised frame layer with higher density, overlapping with the first layer to move the raised frame mode away from the main resonant frequency, thereby reducing lateral energy leakage and increasing the quality factor (Q) of the bulk acoustic wave device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a raised frame structure is used to block lateral energy leakage, then insertion loss is reduced, but spurious modes are generated that cause Gamma degradation
Solution Approach 1:
The raised frame structure is divided into multiple layers with different acoustic impedances. The first raised frame layer has lower acoustic impedance than the piezoelectric layer, while the second raised frame layer has higher acoustic impedance. This segmentation allows each layer to contribute differently to blocking lateral energy leakage while suppressing spurious modes, resolving the contradiction between reducing insertion loss and preventing Gamma degradation.
Solution Approach 2:
The raised frame structure uses composite material design with at least two different materials having different acoustic impedances. This composite structure creates a more effective acoustic barrier that blocks lateral energy leakage without generating harmful spurious modes, as the impedance mismatch between layers interferes with the formation of single-frequency spurious resonances.
2Ease of manufacture
If a single-layer raised frame is used, then manufacturing is simpler, but the quality factor (Q) is insufficient and lateral energy leakage occurs
Solution Approach 1:
The raised frame is segmented into multiple layers with different acoustic properties. This segmentation improves the quality factor by creating a more effective acoustic barrier against lateral energy leakage, while still maintaining manufacturability through standard semiconductor fabrication processes that can handle multi-layer deposition.
Solution Approach 2:
The acoustic impedance parameter is varied across different layers of the raised frame structure. By changing the acoustic impedance from one layer to another, the structure achieves superior performance in blocking lateral energy leakage and enhancing quality factor, while the layers can be formed using conventional fabrication techniques.
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
The multi-layer raised frame structure effectively reduces insertion loss and Gamma loss by positioning the raised frame mode outside carrier aggregation bands, enhancing the reflection coefficient and quality factor, leading to improved performance in multiplexers and other acoustic wave filters.
Implementation Method 1
The first raised frame layer has a lower acoustic impedance than the piezoelectric layer
Implementation Method 2
The multi-layer raised frame structure can block lateral energy leakage from the active region to a passive region of the bulk acoustic wave device
Implementation Method 3
In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer
Data Source
AI summary
Aspects of this disclosure relate to a bulk acoustic wave device that includes a multi-layer raised frame structure. The multi-layer raised frame structure includes a first raised frame layer positioned between a first electrode and a second electrode of the bulk acoustic wave device. The first raised frame layer has a lower acoustic impedance than the first electrode. The first raised frame layer and the second raised frame layer overlap in an active region of the bulk acoustic wave device. Related filters, multiplexers, packaged modules, wireless communication devices, and methods are disclosed.