Bulk Acoustic Wave Resonator Air Edge for Horizontal Wave Reflection
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Solution Overview
Problem
Bulk acoustic wave resonators (BAWRs) face limitations in bandwidth and Q-factor due to losses from horizontal acoustic waves, which affect the Acousto-electric coupling coefficient and overall performance in RF communication systems.
Innovation Solution
The introduction of an air edge formed by etching a predetermined portion of the BAWR's edge, creating a steep slope and air gap structure, which reflects horizontal acoustic waves and enhances the Acousto-electric coupling coefficient by minimizing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the BAWR operates with conventional electrode and piezoelectric layer configurations, then the device structure is simple, but the Acousto-electric coupling coefficient is low resulting in limited bandwidth
Solution Approach 1:
The patent applies segmentation by dividing the electrode structure into multiple layers (first electrode layer, second electrode layer) and introducing intermediate layers (first intermediate layer, second intermediate layer) between them. This multi-layer segmentation enables better acoustic wave coupling and increases the Acousto-electric coupling coefficient, thereby expanding bandwidth without excessive complexity
Solution Approach 2:
The patent employs composite material structures by combining different materials in the electrode and piezoelectric layers. Specifically, it uses combinations such as metal layers with different acoustic impedances, and integrates these with the piezoelectric layer to create a composite structure that optimizes acoustic coupling and electrical performance, achieving higher bandwidth
2Adaptability or versatility
If the BAWR uses standard electrode and piezoelectric layer film characteristics, then the manufacturing process is straightforward, but the Acousto-electric coupling coefficient remains low
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness, material composition, and acoustic impedance of each layer in the multi-layer structure. By carefully controlling these parameters during manufacturing, the design achieves enhanced Acousto-electric coupling coefficient while maintaining compatibility with standard fabrication processes
Solution Approach 2:
The patent introduces intermediate layers between the electrodes and piezoelectric layer that act as mediators to improve acoustic coupling. These intermediate layers facilitate better energy transfer between the electrical and acoustic domains, increasing the Acousto-electric coupling coefficient without requiring complex manufacturing steps
3Reliability
If no air edge is formed, then the device structure is simpler, but horizontal acoustic wave losses reduce the Q-factor
Solution Approach 1:
The patent applies the taking out principle by removing material to create an air edge structure at the periphery of the BAWR device. This extracted air region acts as an acoustic reflector that prevents horizontal acoustic wave losses, thereby improving the Q-factor. The air edge is formed by selectively removing material around the active device area
Solution Approach 2:
The patent converts the potentially harmful effect of horizontal acoustic wave propagation into a beneficial reflection mechanism. By introducing the air edge structure, the acoustic waves that would otherwise be lost are reflected back into the active region, converting energy loss into useful acoustic energy that enhances the Q-factor
4Reliability
If the air edge is formed by etching the entire edge thickness, then the acoustic wave reflection is maximized, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies partial action by forming the air edge structure to etch only a portion of the total edge thickness rather than the entire thickness. This partial etching approach provides sufficient acoustic reflection to improve Q-factor while significantly reducing the stringency of manufacturing precision requirements compared to full-thickness etching
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 improves the Q-factor and bandwidth of BAWRs, enabling their use in RF filters and duplexers with reduced band gaps, effectively utilizing frequency resources and enhancing data transmission capabilities.
Implementation Method 1
The piezoelectric layer oscillates in response to a high frequency electric potential applied to the electrodes
Implementation Method 2
an air gap, disposed below the bulk acoustic wave resonance unit and on a substrate that reflects a vertical acoustic wave generated from the bulk acoustic wave resonance unit
Implementation Method 3
creating a steep slope and air gap structure, which reflects horizontal acoustic waves and enhances the Acousto-electric coupling coefficient by minimizing losses
Data Source
AI summary
Disclosed is a bulk acoustic wave resonator (BAWR). The BAWR includes a bulk acoustic wave resonance unit with a first electrode, a second electrode, and a piezoelectric layer. The piezoelectric layer is disposed between the first electrode and the second electrode. An air edge is formed at a distance from a center of the bulk acoustic wave resonance unit.