Single-Crystal BAW Resonator for 5.9 GHz RF Filter
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Solution Overview
Problem
Current bulk acoustic wave resonators using polycrystalline piezoelectric thin films face degradation at frequencies above 3 GHz due to poor crystalline quality at thin thicknesses, limiting their performance in high-frequency applications.
Innovation Solution
The use of single crystalline or epitaxial piezoelectric thin films grown on compatible substrates, combined with advanced manufacturing processes, to create high-quality bulk acoustic wave resonators with enhanced electro-mechanical coupling and quality factor for RF filters operating at frequencies around 5 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polycrystalline piezoelectric thin films are used in bulk acoustic wave resonators, then manufacturing is easier and cost is lower, but crystalline quality degrades at thin thicknesses required for frequencies above 3 GHz
Solution Approach 1:
The patent changes the fundamental parameter of crystalline structure from polycrystalline to single-crystalline. This parameter change enables the resonator films to maintain high crystalline quality at thin thicknesses (below 0.5 um) required for frequencies above 3 GHz, while still allowing for manufacturing through epitaxial growth processes on compatible substrates
Solution Approach 2:
The patent employs composite material structures by growing single-crystalline piezoelectric films on compatible crystalline substrates. This composite approach allows the piezoelectric layer to achieve the necessary thin thicknesses for high-frequency operation while maintaining superior crystalline quality that polycrystalline films cannot achieve at the same thickness
2Manufacturing precision
If single crystalline piezoelectric thin films are used, then crystalline quality and electro-mechanical coupling are improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the manufacturing process into distinct stages: growing the single-crystalline piezoelectric film on a compatible crystalline substrate, then transferring the film to the final resonator device. This segmentation allows the complex single-crystalline growth to be performed separately under controlled conditions, then integrated into the device fabrication process
Solution Approach 2:
The patent uses a compatible crystalline substrate as an intermediary medium during the film growth process. This substrate serves as a temporary host that enables the epitaxial growth of high-quality single-crystalline piezoelectric films, which can then be transferred to the final device structure, thereby managing the complexity of single-crystalline manufacturing
3Device complexity
If polycrystalline piezoelectric films are used, then device complexity is reduced, but quality factor and acoustic wave control deteriorate at high frequencies
Solution Approach 1:
The patent changes the crystalline structure parameter from polycrystalline to single-crystalline, which fundamentally improves the quality factor and acoustic wave control at high frequencies. This parameter change enables the resonators to operate reliably above 3 GHz with enhanced electro-mechanical coupling, while the complexity is managed through established epitaxial growth and transfer 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 enables the production of high-performance RF filters with improved quality factor and acoustic wave control, overcoming the limitations of polycrystalline films and meeting the demands of modern data communication systems.
Implementation Method 1
bulk acoustic wave resonators using polycrystalline piezoelectric thin films
Implementation Method 2
Single crystalline or epitaxial piezoelectric thin films grown on compatible crystalline substrates exhibit good crystalline quality and high piezoelectric performance
Implementation Method 3
bulk acoustic wave resonators (BAWR)
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.