Single-Crystal BAW RF Filter Circuits for High-Q 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 thicknesses below 0.5 um, limiting their performance for frequencies above 5 GHz, while single crystalline films maintain high quality even at thin thicknesses but pose challenges in manufacture and transfer.
Innovation Solution
The development of manufacturing processes and structures for high-quality bulk acoustic wave resonators using single crystalline or epitaxial piezoelectric thin films, employing techniques such as thin film transfer and sacrificial layers to produce resonators with enhanced quality factor and electro-mechanical coupling for high-frequency applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polycrystalline piezoelectric thin films are used for bulk acoustic wave resonators, then manufacturing is easier and cost is lower, but quality degrades quickly when thickness decreases below 0.5 um, limiting performance for frequencies above 5 GHz
Solution Approach 1:
The patent changes the material parameter from polycrystalline to single-crystal piezoelectric films, which fundamentally alters the quality-factor-vs-thickness relationship. Single-crystal films maintain high quality factors even at thicknesses below 0.5 um, enabling 5 GHz and above operations while allowing the use of thinner films for higher frequency applications.
Solution Approach 2:
The patent introduces an intermediary process (thin film transfer technique) that enables the use of single-crystal piezoelectric films in standard CMOS manufacturing environments. This intermediary approach bridges the gap between the superior performance of single-crystal films and the manufacturing simplicity of polycrystalline films, allowing high-quality resonators to be produced using established fabrication processes.
2Reliability
If single crystalline piezoelectric thin films are used for bulk acoustic wave resonators, then quality factor remains high even at thin thicknesses below 0.5 um, but manufacturing and transfer processes become more complex
Solution Approach 1:
The patent applies preliminary action by pre-growing single-crystal piezoelectric films on suitable substrates using epitaxial techniques before transfer. This preliminary film formation on a separate substrate allows for optimized crystal growth conditions that would be difficult to achieve in standard CMOS processes, ensuring high quality factors are achieved before the films are transferred to the final device structure.
Solution Approach 2:
The patent uses an intermediary transfer process that decouples the film growth step from the device fabrication step. Single-crystal films are grown on specialized substrates where crystal quality can be optimized, then transferred to CMOS-compatible substrates for integration. This intermediary approach maintains manufacturing simplicity by using standard processes for the actual device fabrication while achieving superior material quality through the transfer technique.
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
These processes enable the production of resonators with improved performance and cost-efficiency, capable of operating effectively at frequencies around 5 GHz and above, addressing the limitations of polycrystalline films and facilitating the demands of contemporary data communication.
Implementation Method 1
Bulk acoustic wave resonators (BAWR) using crystalline 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.