FBAR Electrode Layout for Lower Parasitic Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing film bulk acoustic resonator (FBAR) structures face challenges in minimizing parasitic capacitance and achieving precise electrode patterning due to the overlapping areas outside the lower cavity, which affects the resonator's performance and quality factor.
Innovation Solution
The FBAR structure includes a bottom cap wafer with a piezoelectric layer and electrodes, where the electrodes are patterned to minimize overlap outside the lower cavity, and a method of fabrication that involves forming a sacrificial layer, bonding a bottom cap wafer, removing the substrate, and patterning the electrodes to create a lower cavity, thereby minimizing parasitic capacitance and improving the Q factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If traditional FBAR fabrication methods are used, then the manufacturing process is simpler, but parasitic capacitance increases due to electrode overlap outside the lower cavity
Solution Approach 1:
The sacrificial layer is formed and positioned before the final electrode patterning step. This preliminary structure enables subsequent precise patterning of electrodes to minimize overlap outside the lower cavity, while the sacrificial layer itself is removed after serving its positioning function. This approach allows achieving low parasitic capacitance through careful preliminary structuring without permanently increasing device complexity.
2Manufacturing precision
If electrode patterning is performed early in the process, then the manufacturing process is simpler, but precise control of electrode alignment and overlap is difficult
Solution Approach 1:
The sacrificial layer serves as an intermediary structure that facilitates precise electrode patterning. It provides a temporary reference structure that enables accurate alignment and positioning of electrodes during the patterning process. After the electrodes are precisely patterned, the sacrificial layer is removed, having served its purpose as a patterning aid. This intermediary approach achieves high manufacturing precision without leaving permanent complex structures.
3Ease of manufacture
If the substrate is removed early, then subsequent processing is easier, but the piezoelectric layer and electrodes lack support during critical patterning steps
Solution Approach 1:
The sacrificial layer is formed and used for positioning and support before the substrate is removed. This preliminary structuring provides the necessary mechanical support during critical patterning steps. After the electrodes are precisely patterned using the sacrificial layer as a reference, the substrate is then removed. This sequencing ensures structural reliability during processing while ultimately achieving ease of manufacture.
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 allows for precise control of electrode patterning, reducing parasitic capacitance and enhancing the quality factor of the FBAR, while also simplifying the manufacturing process and improving thermal conductivity and reliability.
Implementation Method 1
A film bulk acoustic resonator (FBAR) is a device including a thin film that is made of a piezoelectric material and disposed between two electrodes
Implementation Method 2
removing a portion of the sacrificial layer to form a lower cavity
Data Source
AI summary
A method for fabricating a film bulk acoustic resonator (FBAR) structure includes: sequentially forming a top electrode material layer, a piezoelectric layer, and a bottom electrode material layer on a substrate; patterning the bottom electrode material layer to form a bottom electrode; forming a sacrificial layer above the bottom electrode; bonding a bottom cap wafer onto the sacrificial layer; removing the substrate; patterning the top electrode material layer to form a top electrode; and removing a portion of the sacrificial layer to form a lower cavity.