Integrated FBAR-SAW Filter Layout for Compact Multi-Band Resonance
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Solution Overview
Problem
Existing filters for mobile communication devices, which combine Film Bulk Acoustic Resonators (FBARs) and Surface Acoustic Wave (SAW) resonators, face challenges in achieving compact size and wide frequency band usage due to complex connection processes and increased size from separate resonator connections.
Innovation Solution
An integrated filter is developed, comprising a substrate with stacked electrodes and piezoelectric layers, including inter-digital transducer electrodes in comb structures, and cavities to enhance resonance characteristics, allowing for both FBAR and SAW resonator integration on a single substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If FBAR and SAW resonators are separately fabricated and connected, then the filter can operate in various frequency bands, but the connection process becomes complicated and yield is reduced
Solution Approach 1:
The patent merges FBAR and SAW resonators into a single integrated structure on one substrate. The FBAR resonator includes a lower electrode, piezoelectric layer, and upper electrode, while the SAW resonator includes IDT electrodes on the same substrate. This integration eliminates the need for separate fabrication and connection processes, reducing complexity while maintaining multi-frequency band operation capability
2Adaptability or versatility
If multiple resonators are separately fabricated and connected, then various frequency bands can be utilized, but the entire filter size increases
Solution Approach 1:
The patent combines multiple resonators (FBAR and SAW) into a single integrated filter structure on one substrate, reducing the overall filter size compared to separate resonator assemblies
Solution Approach 2:
The patent implements a nested structure where the FBAR resonator and SAW resonator are positioned in different areas on the same substrate, with the first piezoelectric layer extending to surround portions of the second piezoelectric layer. This nested arrangement maximizes space utilization and minimizes the overall filter footprint
3Area of stationary object
If FBAR and SAW resonators are integrated on a single substrate, then compactness is achieved, but the fabrication process must be simplified
Solution Approach 1:
The patent segments the piezoelectric material formation into distinct stages: first forming the first piezoelectric layer with the FBAR electrodes, then forming the second piezoelectric layer with the SAW IDT electrodes. This segmentation allows each resonator type to be optimized independently while maintaining a unified fabrication process on a single substrate
Solution Approach 2:
The patent uses a universal substrate and piezoelectric material system that supports both FBAR and SAW resonator fabrication. The same piezoelectric material (e.g., AlN or ZnO) is used for both resonator types, allowing a single fabrication process to produce multi-functional resonators for different frequency bands
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
The integrated filter achieves compactness and improved manufacturing yield by enabling operation across various frequency bands while reducing the complexity of connection processes.
Implementation Method 1
an electric energy is applied to the lower and upper electrodes to induce an electric field varying with time in the piezoelectric layer, and the electric field generates a bulk acoustic wave in a direction toward which the resonance part vibrates, in the piezoelectric layer so as to produce a resonance
Implementation Method 2
the SAW filters include inter-digital transducer (IDT) electrodes fabricated in comb structures on piezoelectric substrates
Data Source
AI summary
An integrated filter including a film bulk acoustic resonator (FBAR) and a surface acoustic wave (SAW) resonator and a method of fabricating the integrated filter. The integrated filter includes: a substrate; a first electrode positioned in a predetermined first area on an upper surface of the substrate; a first piezoelectric layer positioned on the first electrode; a second electrode positioned on the first piezoelectric layer; a second piezoelectric layer positioned in a predetermined second area on the upper surface of the substrate; and at least one inter-digital transducer (IDT) electrode positioned on the second piezoelectric layer. The IDT electrode includes: a first IDT electrode formed in a comb structure on the second piezoelectric layer; and a second IDT electrode formed in a comb structure on the second piezoelectric layer so as to mesh with the first IDT electrode. The first and second piezoelectric layers are formed of an identical material. Thus, an integrated filter which operates in various frequency bands can be made compact.