BAW Resonator Recessed Frame Structure for Spurious Mode Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bulk acoustic wave (BAW) resonators face challenges in achieving high quality factor (Q) and suppressing spurious modes while meeting performance specifications.
Innovation Solution
The BAW resonator design incorporates a recessed frame structure in the acoustically active region with a piezoelectric layer having a lower effective piezoelectric coefficient in the peripheral region, along with engineered thickness variations in electrodes and potential recessed or raised frame structures to balance mass loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional BAW resonator structure is used, then the device can be manufactured with standard processes, but the quality factor (Q) is limited and spurious modes are not sufficiently suppressed
Solution Approach 1:
The resonator structure is segmented into distinct regions: an acoustically active region with full electrode and piezoelectric layer thickness, and a peripheral region with reduced thickness. This segmentation allows independent optimization of each region's acoustic properties, enabling high Q factor through controlled mass loading in the peripheral region while maintaining standard manufacturing processes
Solution Approach 2:
The patent applies local quality by creating spatially varying thickness profiles for electrodes and piezoelectric layers. The peripheral region has reduced thickness compared to the acoustically active region, creating localized mass loading effects that suppress spurious modes without compromising the overall Q factor. This local modification allows tailored acoustic impedance in different zones of the resonator
2Reliability
If the piezoelectric layer and electrodes have uniform thickness, then manufacturing is simplified, but mass loading cannot be optimized to suppress frame and lateral modes
Solution Approach 1:
The patent introduces dynamic thickness variation in the electrode and piezoelectric layer structures. The thickness is not static and uniform but varies spatially to create the desired mass loading profile. This dynamic structural design enables suppression of frame and lateral modes through controlled acoustic impedance variations while remaining compatible with standard semiconductor manufacturing processes
Solution Approach 2:
The patent changes the physical parameter of thickness across different regions of the resonator. By varying the thickness of electrodes and piezoelectric layers from the acoustically active region to the peripheral region, the mass loading is optimized to suppress spurious modes. This parameter change is achieved through controlled deposition or etching processes that can create gradual or stepped thickness transitions
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 enhances Q factor and suppresses frame and lateral modes, improving overall BAW resonator performance and reducing energy losses.
Implementation Method 1
a piezoelectric layer positioned between the first electrode and the second electrode
Data Source
AI summary
Aspects of this disclosure relate to a bulk acoustic wave resonator having an acoustically active region and a peripheral region. The bulk acoustic wave resonator can include a first electrode, a second electrode, a piezoelectric layer positioned between the first electrode and the second electrode, and a recessed frame structure at least partially in the acoustically active region. The piezoelectric layer can have an effective piezoelectric coefficient with a lower magnitude in the peripheral region than in the acoustically active region. Other embodiments of bulk acoustic wave resonators are disclosed. Related filters, multiplexers, radio frequency modules, radio frequency systems, wireless communication devices, and methods are disclosed.