BAW Resonator 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 introduction of a frame structure positioned outside the active region of BAW devices, which includes a raised or recessed frame structure symmetric about the piezoelectric layer, reduces lateral energy leakage and suppresses 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 quality factor (Q) is improved, but device complexity increases
Solution Approach 1:
The device is divided into distinct functional regions: an active region containing the piezoelectric layer and electrodes for acoustic wave generation, and a frame region containing the frame structure for suppressing spurious modes. This segmentation allows each region to perform its specific function optimally without interfering with the other, resolving the contradiction by spatially separating the quality enhancement function from the active resonator structure.
Solution Approach 2:
The frame structure is positioned only in the frame region outside the active region, applying suppression functionality locally where spurious modes occur at the boundaries. The active region maintains its original simple structure for optimal resonator performance, while the frame region introduces the necessary complexity only where needed to suppress lateral energy leakage and improve quality factor.
2Loss of energy
If a frame structure is positioned outside the active region, then lateral energy leakage is reduced, but manufacturing complexity increases
Solution Approach 1:
The frame structure is extracted and positioned outside the active region, separating the energy suppression function from the active resonator structure. This allows the frame structure to be designed and manufactured independently, potentially using different materials or processes optimized for suppression functionality without complicating the fabrication of the active piezoelectric resonator structure.
Solution Approach 2:
The frame structure extends in the lateral dimension outside the active region boundary, creating a spatial separation between the active resonator volume and the suppression structure. This dimensional arrangement allows the frame structure to intercept and suppress lateral energy leakage without interfering with the vertical acoustic wave propagation in the active region, simplifying the manufacturing process by avoiding complex three-dimensional integration.
3Object-generated harmful factors
If the frame structure is symmetric about the piezoelectric layer, then spurious mode suppression is improved, but structural complexity increases
Solution Approach 1:
The frame structure is designed with asymmetric positioning relative to the piezoelectric layer, with the frame structure located outside the active region boundary rather than symmetrically enclosing it. This asymmetric arrangement effectively suppresses spurious modes by breaking the symmetry that would otherwise support these unwanted resonances, while maintaining simpler overall device architecture compared to fully symmetric enclosures.
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, in which acoustic waves propagate in the bulk of the piezoelectric layer
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... reduces lateral energy leakage and suppresses undesirable frame modes
Data Source
AI summary
Aspects of this disclosure relate to a bulk acoustic wave device having an active region and a frame region outside of the active region. The bulk acoustic wave device can include an acoustic reflector, electrodes including a first electrode and a second electrode, a piezoelectric layer, and a frame structure positioned over the acoustic reflector in the frame region and outside of the active region. The first electrode and the second electrode can be on opposing sides of the piezoelectric layer over the acoustic reflector in the active region. Related filters, multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, and methods are disclosed.