BAW Resonator Raised Frames for Lower Lateral Energy Leakage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Achieving high performance specifications in bulk acoustic wave (BAW) devices is challenging due to issues with lateral energy leakage and mass loading, which affect the quality factor (Q) and frequency response.
Innovation Solution
Incorporating multi-layer and gradient raised frame structures in BAW resonators, such as dual-layer and multi-gradient designs, to enhance acoustic reflection and reduce lateral energy leakage, thereby improving the quality factor (Q) at different frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer raised frame structure is used in BAW resonators, then the device complexity is reduced and manufacturing is easier, but the quality factor (Q) is insufficient due to lateral energy leakage
Solution Approach 1:
The raised frame structure is divided into multiple layers (first raised frame layer and second raised frame layer) positioned at different heights above the piezoelectric layer. This segmentation allows each layer to reflect acoustic waves at different stages, progressively reducing lateral energy leakage and improving the quality factor without requiring excessive complexity in a single structure
Solution Approach 2:
The frame structure extends into the vertical dimension with multiple layers at different heights rather than relying solely on horizontal expansion. This multi-layer vertical arrangement creates additional acoustic reflection planes, enhancing energy confinement in the lateral direction while maintaining a compact horizontal footprint
2Reliability
If mass loading is increased in the frame region to improve frequency response, then the quality factor improves, but the device becomes more sensitive to manufacturing variations
Solution Approach 1:
Different raised frame layers are positioned at different locations and heights above the piezoelectric layer, with each layer providing localized mass loading and acoustic reflection. This distributed local quality approach improves frequency response and quality factor while reducing sensitivity to manufacturing variations compared to concentrated mass loading
Solution Approach 2:
The raised frame structure uses composite material layers (oxide layer and metal layer) with different acoustic impedances. The oxide layer provides acoustic isolation while the metal layer provides mass loading, creating a composite structure that achieves improved frequency response and quality factor with reduced sensitivity to manufacturing tolerances
3Loss of energy
If a multi-layer raised frame structure with oxide and metal layers is used, then acoustic reflection is enhanced and lateral energy leakage is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The acoustic impedance of the frame structure is optimized by selecting specific materials (oxide with lower acoustic impedance, metal with higher acoustic impedance) and controlling their thicknesses. This parameter optimization enhances acoustic reflection and reduces lateral energy leakage while maintaining compatibility with standard semiconductor manufacturing processes
Solution Approach 2:
The oxide layer acts as an intermediary between the piezoelectric layer and the metal raised frame layer. This intermediate oxide layer provides acoustic isolation and stress management, enabling the metal layer to provide effective mass loading and acoustic reflection while reducing the overall sensitivity to manufacturing variations
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 multi-layer and gradient raised frame structures significantly enhance the quality factor (Q) of BAW devices, achieving low insertion loss and improved frequency response across resonant and anti-resonant frequencies.
Implementation Method 1
the raised frame structure can be configured to reflect the acoustic waves laterally, away from the active region of the BAW device
Implementation Method 2
acoustic waves propagate in a bulk of a piezoelectric layer
Data Source
AI summary
A filter is disclosed. The filter can be a band pass filter or a band rejection filter. The filter can have bulk acoustic wave resonators. The filter can include a shunt bulk acoustic wave resonator and a series bulk acoustic wave resonator. The shunt bulk acoustic wave resonator and the series bulk acoustic wave resonator include different raised frame structures. The different raised frame structures contribute to one of the shunt bulk acoustic wave resonator or the series bulk acoustic wave resonator to have a higher quality factor below a resonant frequency than the other.