Acoustic Resonator Structure for High-Frequency Low-Loss RF Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF communication systems face challenges in achieving high resonance frequencies with FBAR and SMR devices due to limitations in film thickness control and quality factor (Q) degradation at higher frequencies, leading to increased insertion loss and reduced power handling capabilities.
Innovation Solution
The proposed acoustic resonator design incorporates a piezoelectric layer between electrodes, with multiple layers of high and low acoustic impedance materials, including diamond, to enhance resonance frequency and quality factor, while using tethers and phononic crystals to improve power handling and frequency stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the film thickness of the resonant body is reduced to increase resonance frequency, then the resonance frequency increases, but the quality factor (Q) decreases
Solution Approach 1:
The resonant body is divided into multiple thin film layers (first thin film layer, second thin film layer, third thin film layer) with different functions. The first layer provides piezoelectric effect, the second layer provides acoustic reflection, and the third layer provides additional piezoelectric coupling. This segmentation allows each layer to be optimized independently, enabling high resonance frequency while maintaining high Q factor through the acoustic reflector layer that prevents energy loss.
Solution Approach 2:
The patent uses composite material structure combining piezoelectric materials (AlN, ScAlN) with acoustic reflector materials. The composite structure of multiple functional layers creates a resonant body that achieves both high resonance frequency (through thin total thickness) and high quality factor (through acoustic reflection at interfaces between layers with different acoustic impedances).
2Manufacturing precision
If ion-milling trimming is used to achieve high level thickness uniformity, then the manufacturing precision improves, but the productivity decreases and cost increases
Solution Approach 1:
The patent designs the resonant body with predetermined thicknesses for each layer that are calculated to achieve the target resonance frequency without requiring post-fabrication trimming. The first, second, and third thin film layers are deposited with specific thicknesses in advance, and the acoustic reflector layer is designed to provide the necessary acoustic reflection. This preliminary design approach eliminates the need for ion-milling trimming, thereby maintaining high manufacturing precision while significantly improving productivity and reducing costs.
3Speed
If the resonance frequency is doubled to meet future RF communication requirements, then the frequency coverage improves, but the quality factor is reduced by half
Solution Approach 1:
The resonant body is divided into multiple thin film layers (first thin film layer, second thin film layer, third thin film layer) with different functions. The first layer provides piezoelectric effect, the second layer provides acoustic reflection, and the third layer provides additional piezoelectric coupling. This segmentation allows each layer to be optimized independently, enabling high resonance frequency while maintaining high Q factor through the acoustic reflector layer that prevents energy loss.
Solution Approach 2:
The patent uses composite material structure combining piezoelectric materials (AlN, ScAlN) with acoustic reflector materials. The composite structure of multiple functional layers creates a resonant body that achieves both high resonance frequency (through thin total thickness) and high quality factor (through acoustic reflection at interfaces between layers with different acoustic impedances).
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 design achieves higher resonance frequencies, improved quality factor, and reduced insertion loss, enabling efficient power handling and robust frequency stability across a wide temperature range.
Implementation Method 1
an acoustic resonator can comprise a piezoelectric layer disposed between a pair of electrodes
Implementation Method 2
one or a plurality of acoustic wave reflectors, each of which can include a layer of a high acoustic impedance material and, optionally, a layer of a low acoustic impedance material
Data Source
AI summary
An acoustic resonator includes a piezoelectric stack including a piezoelectric layer having a top surface and a bottom surface, a top electrode layer disposed above the top surface, and a bottom electrode layer disposed below the bottom surface. A number of acoustic wave reflectors are disposed on a side of the bottom electrode layer opposite the piezoelectric layer. Each acoustic wave reflector includes a high acoustic impedance layer and may include a low acoustic impedance layer. The acoustic resonator may include a tether that extends laterally to a stacking direction of the layers of the piezoelectric stack. A supporting structure may be coupled to the tether opposite the acoustic resonator for anchoring the acoustic resonator. A mirror, one or more phononic crystals, or both may be positioned on proximate the tether opposite the acoustic resonator to avoid resonant waves from exiting the acoustic resonator in use.