BAW Resonator Gap Frame Structure for Lower Lateral Energy Leakage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current bulk acoustic wave (BAW) devices face challenges in achieving high quality factor (Q) values and low insertion loss due to lateral energy leakage, which affects their performance in radio frequency filters.
Innovation Solution
The introduction of a raised and/or suspended frame structure with a low acoustic impedance material, such as silicon dioxide, under the BAW device, which reduces lateral energy leakage and enhances the quality factor by creating a gap that elevates the frame structure, thereby improving the electromechanical coupling coefficient and reducing spurious modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional BAW device structure is used, then the device is simple to manufacture, but lateral energy leakage occurs which reduces the quality factor
Solution Approach 1:
The frame structure is divided into multiple segments including an inner raised frame portion, an outer raised frame portion, and a suspended frame portion. This segmentation allows each portion to serve specific functions: the inner and outer raised frames provide structural support and acoustic isolation, while the suspended frame portion creates a gap to reduce lateral energy leakage, collectively improving the quality factor without requiring complete structural redesign
Solution Approach 2:
The frame structure is elevated in the vertical dimension to create a gap between the frame and the piezoelectric layer. This dimensional change transforms a planar frame into a three-dimensional suspended structure, effectively blocking lateral energy leakage paths while maintaining manufacturing feasibility through standard layering techniques
2Reliability
If the frame structure is elevated to create a gap, then lateral energy leakage is reduced and quality factor increases, but the device structure becomes more complex
Solution Approach 1:
The frame is segmented into inner and outer raised portions connected by suspended sections, allowing the gap to be formed only where needed for acoustic isolation while maintaining structural integrity and simplifying manufacturing compared to a completely redesigned structure
Solution Approach 2:
The raised frame structure serves multiple functions simultaneously: it provides mechanical support, creates the acoustic gap to reduce lateral energy leakage, and defines the active region boundaries. This multi-functionality reduces the need for additional separate components, offsetting the complexity increase
3Object-generated harmful factors
If a raised frame structure is added, then spurious modes are reduced, but manufacturing complexity increases
Solution Approach 1:
The raised frame structure is formed as part of the initial device fabrication process using standard semiconductor manufacturing techniques. By incorporating the frame structure into the base fabrication sequence rather than adding it as a separate post-processing step, manufacturing complexity is minimized while still achieving the goal of reducing spurious modes
Solution Approach 2:
The frame structure uses materials and dimensions optimized to change acoustic impedance parameters, creating acoustic isolation that suppresses spurious modes. By adjusting material composition and geometric parameters within standard manufacturing capabilities, the desired acoustic performance is achieved without requiring complex manufacturing processes
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 results in higher Q values, lower insertion loss, and reduced spurious noise, making the BAW devices suitable for wide pass band filters and improving their performance in radio frequency applications.
Implementation Method 1
a piezoelectric layer between the first electrode and the second electrode
Implementation Method 2
The raised frame structure can include a raised frame layer that extends over at least a portion of the gap. The raised frame layer can have a lower acoustic impedance than at least one of the first electrode, the second electrode, and the piezoelectric layer
Data Source
AI summary
Aspects of this disclosure relate to bulk acoustic wave devices that have a piezoelectric layer between a first electrode and a second electrode and a suspended frame structure that is suspended over a gap. The gap can be between the first electrode and the piezoelectric layer or between the second electrode and the piezoelectric layer. The bulk acoustic wave devices can have an inner raised frame portion inside of the suspended frame. The gap can be disposed between portions of the first and second electrodes that extend past an end of the piezoelectric layer. A conductive material can extend through an opening in a passivation layer at a location directly above the gap.