BAW Resonator Release-Hole Layout for Compact Low-Parasitic Filters
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Solution Overview
Problem
Existing bulk acoustic wave filters face challenges in achieving a smaller size while maintaining performance due to the limitations of bulk acoustic resonator design and fabrication processes.
Innovation Solution
The design incorporates a bulk acoustic wave resonator with a polygon-shaped cavity and strategically positioned release holes in the piezoelectric layer, allowing for efficient etching and minimizing parasitic capacitance, which enables a more compact filter structure by sharing boundary structures between adjacent resonators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional bulk acoustic resonator design is used, then device performance is maintained, but chip size cannot be reduced further
Solution Approach 1:
The resonator structure is segmented by introducing release holes through the piezoelectric layer, dividing the cavity into multiple regions. This segmentation allows for optimized acoustic wave propagation paths while reducing the overall resonator footprint, enabling smaller chip size without compromising performance
Solution Approach 2:
The invention transitions from traditional planar resonator design to a three-dimensional structure with release holes penetrating through the piezoelectric layer. This dimensional change enables vertical acoustic wave paths and improves quality factor while reducing horizontal space requirements, achieving smaller chip size
2Volume of moving object
If resonator spacing is reduced to decrease chip size, then chip size is reduced, but parasitic capacitance increases
Solution Approach 1:
Release holes are strategically positioned to extract acoustic energy from specific regions of the piezoelectric layer. This extraction creates acoustic isolation zones that reduce parasitic capacitance between adjacent resonators, allowing closer spacing without performance degradation
Solution Approach 2:
The release holes act as intermediary acoustic isolation structures between adjacent resonators. These holes serve as acoustic barriers that prevent unwanted coupling and parasitic capacitance effects, enabling resonators to be placed closer together
3Reliability
If cavity shape is changed to optimize performance, then acoustic wave propagation is improved, but manufacturing complexity increases
Solution Approach 1:
The cavity design employs asymmetric shapes with release holes positioned at specific non-uniform locations within the piezoelectric layer. This asymmetric configuration optimizes acoustic wave propagation paths and resonance characteristics while maintaining compatibility with standard semiconductor fabrication processes
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 approach results in a smaller chip size with improved performance by reducing parasitic capacitance and allowing for closer resonator spacing, while maintaining the high-frequency capabilities of bulk acoustic wave filters.
Implementation Method 1
a bulk acoustic resonator is a device including a thin film that is made of a piezoelectric material and disposed between two electrodes
Data Source
AI summary
A bulk acoustic wave resonator includes a substrate, a support layer disposed on the substrate, the support layer including a cavity having a polygon shape with more than three sides in a plane crossing a first direction from the substrate to the support layer, a piezoelectric layer disposed on the support layer, a bottom electrode disposed below the piezoelectric layer, partially overlapping the cavity, and extending across a first side of the cavity, and a top electrode disposed above the piezoelectric layer, partially overlapping the cavity, and extending across a second side of the cavity. The bulk acoustic wave resonator further includes at least one release hole formed in the piezoelectric layer and overlapping a portion of the cavity.