Resonator Control Layer with Uneven Surface for Transverse Wave Trapping
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Solution Overview
Problem
Bulk acoustic wave resonators (BAWRs) face energy loss and reduced Q-factor due to the generation of transverse acoustic waves in addition to longitudinal waves, despite the use of high-quality reflectors, leading to spurious resonance and reduced performance.
Innovation Solution
A resonator design incorporating a control layer with an uneven surface, such as a frame with circular or polygonal concave portions, is used to reflect and trap transverse acoustic waves, preventing energy loss and enhancing the Q-factor and electromechanical coupling coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflector is provided at the bottom of the resonator to minimize longitudinal acoustic wave loss, then the longitudinal wave reflection is improved, but transverse acoustic waves are still generated causing energy loss and reduced Q-factor
Solution Approach 1:
The control layer is selectively positioned only at specific locations (bottom and/or side walls) rather than uniformly throughout the resonator. This localized placement allows the reflector to minimize longitudinal wave loss while the control layer specifically targets transverse wave generation at critical interfaces, resolving the contradiction by addressing different wave types with different structures at different locations.
Solution Approach 2:
The control layer acts as an intermediary structure between the reflector and the acoustic waves. While the reflector handles longitudinal wave reflection, the control layer with its uneven surface intercepts and redirects transverse waves before they can cause energy loss, thereby protecting the Q-factor without interfering with the reflector's primary function.
2Reliability
If a reflector of high quality and performance is used, then longitudinal acoustic wave reflection is minimized, but transverse acoustic waves are generated due to film characteristics resulting in energy loss
Solution Approach 1:
Instead of attempting to create a perfect reflector that handles all wave types uniformly, the solution uses a high-performance reflector for longitudinal waves and adds a localized control layer with uneven surface at specific positions to handle transverse waves. This division of labor allows each component to optimize its specific function without compromise.
Solution Approach 2:
The control layer introduces asymmetric uneven surfaces (protrusions or recesses) at specific locations rather than symmetric uniform structures. This asymmetry creates directional scattering effects that specifically target transverse wave paths while leaving longitudinal wave propagation unaffected, thereby reducing transverse wave energy loss without diminishing reflector performance.
3Reliability
If transverse acoustic waves are generated due to film characteristics, then resonance occurs, but spurious resonance and reduced performance result
Solution Approach 1:
The uneven surface of the control layer converts the harmful transverse wave energy into beneficial scattered reflections. By introducing protrusions or recesses, the transverse waves that would normally cause spurious resonance are scattered in multiple directions, dissipating their energy harmlessly and preventing them from forming coherent spurious resonance patterns, thereby improving overall resonator performance.
Solution Approach 2:
The control layer changes the surface geometry parameter (introducing unevenness with specific protrusion or recess dimensions) to alter how transverse waves interact with the resonator boundaries. This parameter change transforms the wave scattering characteristics, converting potentially harmful spurious resonance into controlled energy dissipation while maintaining the desired primary resonance 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
The resonator effectively suppresses spurious resonance and improves the Q-factor and bandwidth filtering characteristics, leading to enhanced performance in filtering and data transfer applications.
Implementation Method 1
a piezoelectric layer disposed on the first electrode... configured to convert an electrical energy input from the first electrode into an acoustic wave
Implementation Method 2
a control layer disposed on the second electrode and comprising a frame with an uneven surface... configured to control the acoustic wave
Data Source
AI summary
Provided are a resonator and a method of fabricating the same. The resonator may include a first electrode disposed on a substrate, a piezoelectric layer disposed on the first electrode, a second electrode disposed on the piezoelectric layer, and a control layer disposed on the second electrode and having a frame with an uneven surface.