Multi-Layer Raised Frame for BAW Filters With Lower Gamma Loss
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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 piezoelectric layer, 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 and reduce lateral energy leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a raised frame structure is used to block lateral energy leakage, then the quality factor is improved, but spurious modes are generated that cause Gamma degradation
Solution Approach 1:
The raised frame 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 energy reflection, blocking lateral energy leakage while suppressing spurious mode generation, thereby improving quality factor without causing Gamma degradation.
Solution Approach 2:
The acoustic impedance parameter is varied across different raised frame layers. By positioning a lower acoustic impedance layer closer to the piezoelectric layer and a higher acoustic impedance layer farther away, the patent optimizes the acoustic parameter distribution to achieve effective energy confinement while minimizing spurious mode effects.
2Device complexity
If the raised frame mode is close to the main resonant frequency, then the structure is simple, but Gamma loss increases in carrier aggregation bands
Solution Approach 1:
The multi-layer raised frame structure segments the acoustic impedance profile, enabling independent optimization of each layer's thickness and material properties. This allows the raised frame mode to be positioned away from the main resonant frequency, reducing Gamma loss in carrier aggregation bands while maintaining manageable structural complexity.
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 significantly increases the quality factor (Q) and reflection coefficient, reducing Gamma loss and ensuring the raised frame mode is outside carrier aggregation bands, thereby improving the performance of bulk acoustic wave filters.
Implementation Method 1
The first raised frame layer has a lower acoustic impedance than the first electrode. The first raised frame layer can move a frequency of a raised frame mode away from a main resonant frequency of the bulk acoustic wave device.
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.
Implementation Method 4
BAW filters include BAW resonators. Example BAW resonators include film bulk acoustic wave resonators (FBARs) and solidly mounted resonators (SMRs).
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.