Air-Gap FBAR Void Structure for Lower Lateral Energy Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing air-gap type film bulk acoustic resonators (FBARs) face challenges in minimizing energy loss through side surfaces and improving the quality factor due to lateral energy release and structural stability issues.
Innovation Solution
The design incorporates a piezoelectric layer with strategically formed void portions, including piezoelectric cavities that vary in thickness and acoustic impedance, to minimize lateral energy release and enhance resonator performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a membrane type FBAR is used to reduce dielectric loss, then power loss is reduced, but the device area increases and structural stability decreases
Solution Approach 1:
The device is divided into two main types: membrane type FBAR for low power loss applications and air-gap type FBAR for high stability applications. This segmentation allows each type to be optimized for its specific function without compromising the other.
Solution Approach 2:
The air-gap type FBAR extracts the piezoelectric layer from direct contact with the substrate by introducing an air gap, thereby eliminating the need for a membrane structure while maintaining low power loss and improving structural stability.
2Volume of moving object
If the piezoelectric layer is made thinner to reduce device size, then miniaturization is achieved, but the quality factor decreases due to increased energy loss
Solution Approach 1:
The air gap is strategically positioned only in regions where it provides maximum benefit for reducing energy loss while maintaining compact device dimensions. This local modification optimizes the balance between size and energy efficiency.
3Loss of energy
If a Bragg reflector type FBAR is used to improve resonation efficiency, then energy reflection is enhanced, but manufacturing complexity and cost increase
Solution Approach 1:
The air-gap type FBAR uses a simple air gap instead of complex Bragg reflector structures, achieving comparable resonation efficiency with much lower manufacturing complexity and cost. The air gap acts as an effective acoustic reflector without requiring multiple alternating layers.
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 effectively reduces energy loss through side surfaces, increases the quality factor, and improves the skirt property and insertion loss of the FBAR, while maintaining structural stability.
Implementation Method 1
causes resonation due to a piezoelectric property. That is, the FBAR generates resonance by depositing a piezoelectric film between both electrodes and causing a bulk acoustic wave.
Implementation Method 2
the piezoelectric layer includes a void portion having a piezoelectric cavity between the lower electrode and the upper electrode
Data Source
AI summary
Disclosed is an air-gap type film bulk acoustic resonator (FBAR) including a substrate including an air-gap portion with a top surface in which a substrate cavity is formed, a lower electrode formed above the substrate while surrounding the air-gap portion, a piezoelectric layer formed above the lower electrode, and an upper electrode formed above the piezoelectric layer corresponding to a virtual area formed according to a vertical projection of the air-gap portion. Here, the piezoelectric layer includes a void portion having a piezoelectric cavity between the lower electrode and the upper electrode, and the void portion is formed below an edge portion corresponding to an end part of the upper electrode.