FBAR Seed Layer Structure for Higher Bandwidth Without Q Loss
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Solution Overview
Problem
Film bulk acoustic resonators (FBARs) face a trade-off between increasing the electro-mechanical coupling coefficient (kt2) and maintaining a high quality factor (QF), limiting their bandwidth and data transfer rate in miniaturized wireless communication devices.
Innovation Solution
The introduction of a plurality of seed layers with specific crystalline properties, such as aluminum nitride and titanium, between the electrodes of the acoustic resonator, enhances the crystallinity of the piezoelectric layer, thereby improving the kt2 value without compromising the QF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electro-mechanical coupling coefficient (kt2) is increased to improve bandwidth, then the quality factor (QF) decreases, limiting overall performance
Solution Approach 1:
The patent segments the resonator structure by introducing a suspended membrane configuration that separates the piezoelectric layer from the substrate, creating an air gap. This segmentation allows independent optimization of coupling coefficient and quality factor, as the membrane structure reduces energy loss to the substrate while maintaining strong electromechanical coupling in the piezoelectric layer.
Solution Approach 2:
The patent applies local quality by creating a suspended membrane structure with specific material properties in the piezoelectric layer, while the substrate and air gap provide different local characteristics. The membrane region is optimized for high coupling, while the air gap region minimizes energy loss, achieving both high kt2 and high QF through spatially differentiated properties.
2Volume of moving object
If device miniaturization is pursued for portable communications, then manufacturing precision and performance maintenance become more difficult
Solution Approach 1:
The patent employs preliminary action by pre-forming the piezoelectric layer with optimized thickness and crystal orientation on the substrate before creating the air gap and final resonator structure. This preliminary preparation ensures that even in miniaturized devices, the critical piezoelectric properties are established early, maintaining manufacturing precision despite size reduction.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the thickness of the piezoelectric layer and the dimensions of the air gap to optimize performance in miniaturized devices. By scaling these parameters appropriately, the resonator maintains high coupling coefficient and quality factor even as overall device size decreases, addressing the manufacturing precision challenge in miniaturization.
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 approach increases the kt2 value of the acoustic resonator, enhancing its performance and bandwidth, while maintaining a high quality factor, thus improving data transfer rates in miniaturized wireless communication devices.
Implementation Method 1
a piezoelectric layer disposed between the first electrode and the second electrode
Implementation Method 2
a plurality of seed layers disposed on one side of the resonating part
Data Source
AI summary
An acoustic resonator and a method of manufacturing the same are provided. The acoustic resonator includes a resonating part including a first electrode, a second electrode, and a piezoelectric layer; and a plurality of seed layers disposed on one side of the resonating part.