BAW Raised Frame Structure for Spurious Mode Suppression
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Solution Overview
Problem
Existing bulk acoustic wave (BAW) devices face challenges in achieving high quality factor (Q) and suppressing spurious modes while meeting performance specifications.
Innovation Solution
The BAW devices incorporate a frame structure positioned outside the active region, which includes a raised or recessed frame structure symmetric about the piezoelectric layer, to reduce lateral energy leakage and suppress undesirable frame modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a frame structure is added to suppress spurious modes and reduce lateral energy leakage, then the quality factor (Q) increases, but the device complexity increases
Solution Approach 1:
The device is divided into an active region containing the piezoelectric layer and electrodes, and a frame region containing the frame structure. This segmentation allows the frame structure to suppress spurious modes and reduce lateral energy leakage without interfering with the acoustic wave generation and detection functions in the active region, thereby increasing the quality factor while maintaining functional simplicity.
Solution Approach 2:
The frame structure is positioned only in the frame region outside the active region, creating different structural qualities in different areas. The active region maintains its simple electrode-piezoelectric layer configuration for efficient acoustic wave generation, while the frame region incorporates the frame structure to suppress spurious modes and reduce energy leakage, achieving high quality factor without overall device complexity.
2Loss of energy
If the frame structure is positioned between the piezoelectric layer and electrodes, then energy losses are reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The frame structure is positioned in the vertical dimension between the piezoelectric layer and the first electrode, rather than in the lateral plane. This vertical positioning effectively reduces energy losses by confining acoustic waves while allowing lateral manufacturing tolerances to be more relaxed, as the frame structure does not need to align precisely with lateral features of the active region.
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 enhances BAW device performance by increasing quality factor (Q) and reducing energy losses, such as insertion losses and phase noise, while maintaining desired resonant frequencies.
Implementation Method 1
a piezoelectric layer positioned vertically between the first and second electrodes over the acoustic reflector in an active region
Implementation Method 2
an acoustic reflector... In BAW resonators, acoustic waves propagate in the bulk of a piezoelectric layer
Implementation Method 3
a frame structure positioned over the acoustic reflector in the frame region and outside of the active region... to reduce lateral energy leakage and suppress undesirable frame modes
Data Source
AI summary
Aspects of this disclosure relate to a bulk acoustic wave device. The bulk acoustic wave device can include a piezoelectric layer with electrodes positioned on opposing sides and a raised frame structure that includes raised frame layers on opposing sides of the piezoelectric layer. Related filters, multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, and methods are disclosed.