Film Bulk Acoustic Resonator Electrode Isolation for Higher Q
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Solution Overview
Problem
The quality (Q) factor of currently fabricated cavity-type film bulk acoustic resonators cannot be further improved to meet the requirements of high-performance RF systems, particularly for 5G communication applications.
Innovation Solution
A film bulk acoustic resonator design that includes a first substrate with a support layer containing a cavity, a piezoelectric stacked layer with an effective and parasitic working region, and separation structures that insulate the electrodes in the parasitic region, enhancing the quality factor by reducing parasitic parameters and improving device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cavity-type film bulk acoustic resonator is fabricated using conventional methods, then the basic resonator structure is achieved, but the quality factor cannot be further improved to meet high-performance RF system requirements
Solution Approach 1:
The electrode structures are segmented into effective working region electrodes and parasitic working region electrodes by introducing separation structures (trenches or insulating layers). This segmentation isolates the parasitic resonance sources from the effective working region, preventing harmful parasitic effects while maintaining the desired resonator performance and quality factor.
Solution Approach 2:
The parasitic working region electrodes are extracted and separated from the effective working region electrodes using separation structures. By physically removing or isolating the parasitic electrode portions, the harmful parasitic resonance is eliminated while the effective working region continues to function normally, thereby improving the quality factor.
2Reliability
If separation structures are introduced to insulate electrodes in the parasitic working region, then parasitic resonance is reduced and quality factor increases, but device structure becomes more complex
Solution Approach 1:
Separation structures are introduced only in the parasitic working region where they are needed to insulate the electrodes, while the effective working region maintains its original simple structure. This localized approach improves quality factor by reducing parasitic resonance only where necessary, without unnecessarily complicating the entire device structure.
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
The proposed design increases the quality factor of the film bulk acoustic resonator, leading to improved device performance by reducing parasitic resonance and maintaining the effective working region flat, thus enhancing the acoustic wave loss and overall performance.
Implementation Method 1
The piezoelectric film layer is used to generate vibration under an alternating electric field; the vibration excites the bulk acoustic wave propagating along the thickness direction of the piezoelectric film layer
Implementation Method 2
such acoustic wave may be reflected back from the interface between the air and each of the two film electrodes, and then be reflected back and forth inside the film layer to form an oscillation. When the acoustic wave propagates in the piezoelectric film layer having exactly an odd multiple of the half wavelength, a standing wave oscillation is formed
Data Source
AI summary
The present disclosure provides a film bulk acoustic resonator and its fabrication method. The film bulk acoustic resonator includes a first substrate, a first support layer containing a first cavity, a piezoelectric stacked layer, and a first separation structure and/or a second separation structure. The piezoelectric stacked layer includes an effective working region and a parasitic working region; and in the parasitic working region, a first electrode and a second electrode have a corresponding region along a thickness direction. The first separation structure separates the first electrode, and the first electrode of a portion of the parasitic working region is insulated from the first electrode of the effective working region; and the second separation structure separates the second electrode, and the second electrode of a portion of the parasitic working region is insulated from the second electrode of the effective working region.