5.6 GHz BAW RF Filter Topologies Using Single-Crystal Thin Films
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Solution Overview
Problem
Conventional RF technologies face limitations in achieving high-performance filters for frequencies around 5 GHz and above, as polycrystalline piezoelectric thin films degrade quickly at thinner thicknesses required for such frequencies, while single crystalline films maintain quality but are challenging to manufacture and transfer effectively.
Innovation Solution
The development of manufacturing processes and structures for bulk acoustic wave resonators using single crystalline or epitaxial piezoelectric thin films, which provide enhanced quality factor and electro-mechanical coupling, enabling high-frequency RF filter performance by employing techniques like thin film transfer and sacrificial layer processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polycrystalline piezoelectric thin films are used for BAWR, then the manufacturing process is simpler and cost is lower, but the quality factor degrades quickly at thinner thicknesses required for frequencies around 5 GHz and above
Solution Approach 1:
A sacrificial layer is introduced as an intermediary element during the manufacturing process. This sacrificial layer enables the transfer and release of single crystal piezoelectric thin films onto the BAWR structure, facilitating the use of high-quality single crystal materials while managing the manufacturing complexity through a structured process approach
Solution Approach 2:
The patent changes the material parameter from polycrystalline to single crystal piezoelectric thin films, which fundamentally improves the quality factor and electro-mechanical coupling at high frequencies. This parameter change is achieved through modified manufacturing processes including thin film transfer techniques
2Reliability
If single crystalline piezoelectric thin films are used for BAWR, then the quality factor and electro-mechanical coupling are enhanced at high frequencies, but the manufacturing and transfer processes become more challenging
Solution Approach 1:
The sacrificial layer serves as a temporary intermediary structure that holds the single crystal piezoelectric thin film during manufacturing and enables its subsequent release and transfer to the final BAWR configuration, making the complex transfer process more manageable
Solution Approach 2:
The single crystal piezoelectric thin film is grown and prepared on a separate substrate in advance using epitaxial growth techniques, allowing the film to be pre-formed with high crystalline quality before being transferred to the final device structure
3Speed
If thinner piezoelectric thin films are used to achieve frequencies around 5 GHz and above, then the resonant frequency increases, but the quality of polycrystalline films degrades quickly
Solution Approach 1:
The patent changes the material structure parameter from polycrystalline to single crystal, which maintains high film quality even at thinner thicknesses required for higher resonant frequencies around 5 GHz and above
Solution Approach 2:
The sacrificial layer enables the precise placement and release of thin single crystal films, ensuring that the thin films required for high-frequency operation maintain their structural integrity and quality
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 high-quality RF filters with improved performance and cost-efficiency, capable of operating effectively at frequencies around 5 GHz, addressing the limitations of polycrystalline films and simplifying the manufacturing process for single crystalline films.
Implementation Method 1
Bulk acoustic wave resonators (BAWR) using crystalline piezoelectric thin films are leading candidates for meeting such demands
Implementation Method 2
Single crystalline or epitaxial piezoelectric thin films grown on compatible crystalline substrates exhibit good crystalline quality and high piezoelectric performance even down to very thin thicknesses
Implementation Method 3
Bulk acoustic wave resonators (BAWR) using crystalline piezoelectric thin films
Data Source
AI summary
An RF circuit device using modified lattice, lattice, and ladder circuit topologies. The devices can include four resonator devices and four shunt resonator devices. In the ladder topology, the resonator devices are connected in series from an input port to an output port while shunt resonator devices are coupled the nodes between the resonator devices. In the lattice topology, a top and a bottom serial configurations each includes a pair of resonator devices that are coupled to differential input and output ports. A pair of shunt resonators is cross-coupled between each pair of a top serial configuration resonator and a bottom serial configuration resonator. The modified lattice topology adds baluns or inductor devices between top and bottom nodes of the top and bottom serial configurations of the lattice configuration. These topologies may be applied using single crystal or polycrystalline bulk acoustic wave (BAW) resonators.