BAW RF Filter Topologies Using Single-Crystal Resonators Above 5 GHz
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Solution Overview
Problem
Current bulk acoustic wave resonators using polycrystalline piezoelectric thin films face degradation at frequencies above 5 GHz due to poor crystalline quality, limiting their performance in high-frequency applications, while single crystalline films maintain quality but are challenging to manufacture and transfer effectively.
Innovation Solution
The development of a method and structure for bulk acoustic wave resonator devices using single crystal piezoelectric materials like aluminum nitride (AlN) or gallium nitride (GaN) with a manufacturing process that includes a sacrificial layer transfer and multilayer mirror structures to enhance the quality factor and electro-mechanical coupling, enabling high-frequency operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polycrystalline piezoelectric thin films are used in bulk acoustic wave resonators, then the manufacturing process is simpler and cost is lower, but the crystalline quality degrades at frequencies above 5 GHz limiting high-frequency performance
Solution Approach 1:
The patent changes the material parameter from polycrystalline to single-crystal piezoelectric films, fundamentally altering the crystalline structure to maintain high-quality performance at frequencies above 5 GHz while accepting increased manufacturing complexity
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary element in the manufacturing process. This sacrificial layer facilitates the transfer and integration of single-crystal piezoelectric films onto the resonator structure, enabling complex material integration while managing the manufacturing complexity through a temporary mediating structure
2Reliability
If single crystal piezoelectric films are used to maintain crystalline quality at high frequencies, then performance above 5 GHz is improved, but the manufacturing complexity and transfer difficulty increase significantly
Solution Approach 1:
The patent segments the manufacturing process into distinct modules: growing single-crystal piezoelectric films on separate sacrificial layer structures, fabricating resonator components independently, and then integrating them through controlled transfer processes. This modular segmentation manages overall manufacturing complexity by breaking down the challenging single-crystal integration into manageable steps
Solution Approach 2:
The sacrificial layer serves as a critical intermediary that simplifies the transfer of single-crystal piezoelectric films. The film is grown on the sacrificial layer, which then acts as a temporary substrate facilitating handling and integration, reducing the direct complexity of transferring fragile single-crystal films onto final resonator structures
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-performance RF filters with ultra-small form factor, low insertion loss, and high power rating, suitable for 5G and Wi-Fi frequency bands, overcoming the limitations of polycrystalline films and simplifying the manufacturing process.
Implementation Method 1
a piezoelectric material configured overlying the upper surface region and the bottom electrode
Implementation Method 2
Acoustic wave resonator RF filter circuit device
Data Source
AI summary
An RF circuit device using modified lattice, lattice, and ladder circuit topologies. The devices can include a plurality of resonator devices and a plurality of 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.