Symmetric BAW Frame Structure for Spurious Mode Suppression
Find Innovative SolutionsGenerate Solutions
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, which includes symmetric frame layers on opposing sides of the piezoelectric layer, helps in reducing lateral energy leakage and suppressing undesirable raised 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 frame structure is segmented into multiple discrete layers (first frame layer, second frame layer, third frame layer) positioned at different locations around the active region. Each layer serves as an independent acoustic reflector, allowing the system to suppress spurious modes through distributed reflection rather than a single complex structure, thereby improving Q factor while managing complexity through modular design
Solution Approach 2:
The frame layers are nested within the overall device structure, with the first frame layer positioned between the piezoelectric layer and acoustic reflector, the second frame layer positioned at a different elevation, and the third frame layer completing the nested arrangement. This nesting allows multiple reflective surfaces to be integrated within the device footprint without proportionally increasing complexity
2Reliability
If frame layers are positioned on opposing sides of the piezoelectric layer, then spurious modes are suppressed, but manufacturing precision requirements increase
Solution Approach 1:
The frame structure employs asymmetric positioning of frame layers relative to the piezoelectric layer, with the first frame layer positioned between the piezoelectric layer and acoustic reflector, while the second and third frame layers are positioned at different elevations and locations. This asymmetric arrangement creates unequal acoustic path lengths for potential spurious modes, disrupting their formation through destructive interference while allowing more flexible manufacturing tolerances compared to perfectly symmetric designs
Solution Approach 2:
The frame layers are positioned in multiple dimensions including lateral displacement and vertical elevation differences. The second frame layer is laterally offset from the first frame layer, and the third frame layer is positioned at a different elevation than both the first and second frame layers. This multi-dimensional positioning suppresses spurious modes through three-dimensional acoustic reflection paths while distributing manufacturing precision requirements across multiple degrees of freedom rather than requiring precise two-dimensional alignment
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 the first electrode and the second electrode are on opposing sides of the piezoelectric layer over the acoustic reflector in the active region
Data Source
AI summary
Aspects of this disclosure relate to a bulk acoustic wave device. The bulk acoustic wave device can include an active region in which a first electrode and a second electrode overlap and are on opposing sides of a piezoelectric layer in an active region. The bulk acoustic wave device can also include a symmetric frame structure positioned in a frame region and outside the active region. Related filters, multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, and methods are disclosed.