Oxide Raised-Frame BAW Resonator for Spurious Mode Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bulk acoustic wave resonators suffer from spurious signals due to transverse acoustic waves generated perpendicular to the main acoustic wave, degrading their frequency response and performance, particularly in ultrawide bandwidth applications.
Innovation Solution
Incorporating a raised frame structure with a thinner dielectric layer and potentially a thicker metal layer in the recessed frame region and a thicker metal layer in the raised frame region to scatter and reflect transverse acoustic waves, thereby suppressing spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bulk acoustic wave resonator structure is used, then the device is simple to manufacture, but spurious signals are generated due to transverse acoustic waves
Solution Approach 1:
The resonator structure is modified by creating a raised frame region with different material composition (oxide layer) and geometry compared to the central active region. This local differentiation allows the raised frame to specifically target and suppress transverse acoustic waves without affecting the main acoustic wave propagation in the central region, thereby reducing spurious signals while maintaining the overall simple resonator structure
Solution Approach 2:
The solution introduces a vertical dimension by creating a raised frame structure that extends upward from the substrate surface. This three-dimensional feature allows the oxide layer to be positioned at a different height than the piezoelectric film, creating an acoustic impedance mismatch that reflects transverse waves without interfering with the primary acoustic mode in the central active region
2Reliability
If the raised frame structure with oxide layer is implemented, then spurious signals are suppressed, but the manufacturing process becomes more complex
Solution Approach 1:
The oxide layer formation for the raised frame is integrated into the existing semiconductor fabrication process by utilizing standard deposition and etching techniques. The raised frame region is created by selectively depositing oxide material and patterning it to match the desired frame geometry, which can be combined with other device fabrication steps rather than requiring entirely new manufacturing processes
Solution Approach 2:
The manufacturing complexity is managed by controlling the oxide layer thickness and raised frame dimensions as adjustable parameters. By optimizing these geometric parameters, the structure achieves effective spurious signal suppression while maintaining compatibility with standard fabrication tolerances and 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
The raised frame structure effectively suppresses spurious signals, improving the frequency response and quality factor of the resonators, especially in ultrawide bandwidth applications, while maintaining or enhancing conductance and return loss parameters.
Implementation Method 1
scatter and reflect transverse acoustic waves
Implementation Method 2
scatter and reflect transverse acoustic waves
Implementation Method 3
each of the plurality of series arm bulk acoustic resonators and the plurality of shunt bulk acoustic resonators including a piezoelectric film
Data Source
AI summary
A ladder filter comprises series arm bulk acoustic wave resonators electrically connected in series between an input port and an output port and shunt bulk acoustic wave resonators electrically connected between adjacent ones of the series arm bulk acoustic wave resonators and ground, each of the arm bulk acoustic resonators including a central active region and a raised frame region outside of the central active region, each of the series arm bulk acoustic resonators including a piezoelectric film, at least one of the series arm bulk acoustic wave resonators including a layer of oxide disposed directly on the piezoelectric film in the raised frame region, and a metal layer disposed directly on the piezoelectric film in the central active region and on the layer of oxide in the raised frame region, the metal layer having a thickness in the raised frame region no greater than in the central active region.