BAW RF Filter Circuit Using Crystalline Piezoelectric Films Above 5 GHz
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Solution Overview
Problem
Current bulk acoustic wave resonators using polycrystalline piezoelectric thin films face degradation in quality at frequencies above 5 GHz due to thickness limitations, necessitating the development of high-quality single crystalline or epitaxial piezoelectric thin films for improved performance in RF filters.
Innovation Solution
The use of single crystalline or epitaxial piezoelectric thin films, such as aluminum nitride, grown on compatible crystalline substrates, with advanced transfer processes and structures to enhance the quality factor and electro-mechanical coupling for high-frequency bulk acoustic wave resonators, overcoming the limitations of polycrystalline film degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polycrystalline piezoelectric thin films are used in bulk acoustic wave resonators, then manufacturing is easier and cost is lower, but quality factor degrades at frequencies above 5 GHz due to thickness limitations
Solution Approach 1:
The patent changes the fundamental material parameter from polycrystalline to single crystalline structure, enabling the resonators to maintain high quality factor at frequencies above 5 GHz where polycrystalline films degrade due to thickness limitations
Solution Approach 2:
The patent introduces an intermediary transfer process that enables single crystalline piezoelectric thin films to be grown on compatible crystalline substrates and then transferred to resonator structures, bridging the gap between high-quality material growth and practical device fabrication
2Reliability
If single crystalline piezoelectric thin films are used to maintain quality at high frequencies, then performance improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent uses an intermediary transfer process with compatible crystalline substrates to grow single crystalline films, then transfers them to the final resonator structure, managing the complexity of single crystal fabrication while achieving high-quality devices
Solution Approach 2:
The patent develops universal transfer processes and compatible crystalline substrate platforms that can be applied across multiple resonator designs and frequency ranges, reducing overall manufacturing complexity despite the advanced material requirements
3Power
If polycrystalline piezoelectric films are used, then production cost is lower, but electro-mechanical coupling and performance degrade at frequencies around 5 GHz and above
Solution Approach 1:
The patent changes the material parameter from polycrystalline to single crystalline structure, which fundamentally improves electro-mechanical coupling and maintains performance at frequencies around 5 GHz and above where polycrystalline films degrade
Solution Approach 2:
The patent employs composite structures combining single crystalline piezoelectric thin films with compatible crystalline substrates and resonator structures, optimizing both electro-mechanical coupling and frequency performance
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-quality RF filters with improved performance and cost-efficiency, capable of operating at frequencies up to 5 GHz and beyond, meeting the demands of contemporary data communication standards.
Implementation Method 1
Bulk acoustic wave resonators (BAWR) using crystalline piezoelectric thin films
Implementation Method 2
acoustic wave resonator RF filter circuit
Data Source
AI summary
An RF filter system including a plurality of BAW resonators arranged in a circuit, the circuit including a serial configuration of resonators and a parallel shunt configuration of resonators, the circuit having a circuit response corresponding to the serial configuration and the parallel configuration of the plurality of bulk acoustic wave resonators including a transmission loss from a pass band having a bandwidth from 5.490 GHz to 5.835 GHz. Resonators include a support member with a multilayer reflector structure; a first electrode including tungsten; a piezoelectric film including aluminum scandium nitride; a second electrode including tungsten; and a passivation layer including silicon nitride. At least one resonator includes at least a portion of the first electrode located within a cavity region defined by a surface of the support member.