BAW RF Filter Lattice Topology With Single-Crystal Resonators
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Solution Overview
Problem
Conventional 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 crystalline or epitaxial piezoelectric thin films, employing techniques like sacrificial layers and transfer processes to achieve high-quality factor and electro-mechanical coupling, facilitating the production of high-frequency RF filters with enhanced performance and cost-efficiency.
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 frequencies above 5 GHz
Solution Approach 1:
The patent changes the material parameter from polycrystalline to single crystalline piezoelectric thin films, fundamentally altering the crystalline structure to maintain high-quality factor and electro-mechanical coupling at frequencies up to 7 GHz while enabling effective manufacturing through developed transfer processes
2Reliability
If single crystalline piezoelectric thin films are used, then crystalline quality and electro-mechanical coupling are maintained at high frequencies, but manufacturing and transfer processes become more challenging
Solution Approach 1:
The patent employs preliminary actions by growing single crystalline piezoelectric thin films on sacrificial substrate structures before transfer, ensuring high crystalline quality is established beforehand. The sacrificial layers are prepared in advance to facilitate controlled release and transfer of the thin films to final device substrates
Solution Approach 2:
The patent introduces sacrificial substrate structures and sacrificial layers as intermediary elements that enable the manufacturing of single crystalline devices. These intermediaries provide a controlled environment for growing high-quality thin films and facilitate their subsequent transfer to final devices through controlled release mechanisms
3Device complexity
If conventional bulk acoustic wave resonator structures are used, then manufacturing is simpler, but device complexity increases for high-frequency applications above 5 GHz
Solution Approach 1:
The patent changes the fundamental material parameter to single crystalline piezoelectric thin films, which inherently provide the high-quality factor and electro-mechanical coupling needed for high-frequency operation, thereby simplifying the overall device design while maintaining reliability at frequencies up to 7 GHz
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 creation of high-performance RF filters with ultra-small form factors, high rejection, and low insertion loss, suitable for frequencies up to 7 GHz, addressing 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
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.