FBAR Peripheral Film Frame for Spurious Mode Suppression
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Solution Overview
Problem
Film bulk acoustic wave resonators face degradation in frequency response due to spurious acoustic waves generated by transverse waves perpendicular to the main acoustic wave propagation, which degrades their performance.
Innovation Solution
The introduction of recessed and raised frame portions on the top electrode and piezoelectric film, respectively, controls the resonant frequency by varying the thickness of the acoustic wave propagation path, thereby suppressing transverse acoustic waves and reducing spurious mode generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional film bulk acoustic wave resonator structure is used, then the device is simple to manufacture, but spurious acoustic waves are generated that degrade frequency response
Solution Approach 1:
The patent applies local quality by creating frame portions with different heights (first frame portion at a first height, second frame portion at a second height) at specific locations around the piezoelectric film's active region. This local structural variation suppresses spurious acoustic waves at the boundaries without affecting the overall simple resonator design, thereby improving frequency response while maintaining manufacturing simplicity.
Solution Approach 2:
The patent segments the frame structure into multiple distinct frame portions (first frame portion and second frame portion) with different heights and positions. This segmentation allows each frame portion to independently control specific aspects of acoustic wave propagation, effectively suppressing spurious modes while keeping the overall device structure manageable and manufacturable.
2Measurement precision
If the piezoelectric film thickness is increased to control resonant frequency, then the resonant frequency is adjusted, but transverse acoustic waves are generated that create spurious modes
Solution Approach 1:
Instead of uniformly increasing the piezoelectric film thickness throughout, the patent uses localized frame portions of different heights positioned around the active region. The first frame portion at a first height and the second frame portion at a second height locally modify the acoustic boundary conditions, enabling resonant frequency control while suppressing the generation of transverse acoustic waves that cause spurious modes.
3Reliability
If frame structures are added to suppress transverse waves, then spurious mode generation is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent implements frame portions with different heights only at specific locations around the piezoelectric film's active region rather than throughout the entire structure. This localized approach suppresses spurious modes effectively while minimizing the additional manufacturing complexity, as the frame structure can be integrated into existing fabrication processes with minimal modification.
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 configuration significantly suppresses spurious mode generation, enhancing the frequency response and performance of film bulk acoustic wave resonators by controlling the resonant frequency and reducing transverse acoustic wave interference.
Implementation Method 1
a piezoelectric film supported to oscillate in a direction opposite to a main surface of the substrate
Implementation Method 2
controls the resonant frequency by varying the thickness of the acoustic wave propagation path
Implementation Method 3
suppressing transverse acoustic waves and reducing spurious mode generation
Data Source
AI summary
A film bulk acoustic wave resonator (FBAR) is disclosed with recessed and raised frame portions in the piezoelectric film. The FBAR can include a substrate, the piezoelectric film supported to oscillate in a direction opposite to a main surface of the substrate, and a pair of top and bottom electrodes formed respectively on top and bottom surfaces of the film. The recessed frame portion and the raised frame portion can be formed in the film to extend adjacent to each other along a periphery of an active region of the film oscillating during an operation of the film on a top surface of the top electrode.