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Micromachined acoustic wave resonator isolated from substrate
Wei Pang1, Hao Zhang, Eun Sok Kim
1Department of Electrical Engineering-Electrophysics, University of Southern California, Los Angeles, CA 90089-0271, USA. pangwei20000@yahoo.com
Summary
This study presents novel free-standing film bulk acoustic-wave resonators (FBARs) using silicon micromachining. These enhanced FBARs achieve high quality factors and improved electromechanical coupling for advanced applications.
Area of Science:
- Microelectromechanical Systems (MEMS)
- Acoustic Wave Devices
- Materials Science
Background:
- Film Bulk Acoustic-Wave Resonators (FBARs) are crucial for RF filtering.
- Minimizing energy leakage is key to improving FBAR performance.
- Existing FBAR designs face limitations in quality factor (Q) and coupling.
Purpose of the Study:
- To develop high Q, free-standing FBARs using silicon micromachining.
- To investigate methods for enhancing resonator sturdiness and reducing energy loss.
- To explore the impact of support layer removal on FBAR performance.
Main Methods:
- Fabrication of FBARs using metal/ZnO/metal/Si(x)Ny composite layers.
- Suspension of resonators using narrow Si(x)Ny/metal beams.
- Application and patterning of a parylene layer for structural enhancement.
- Comparative analysis of air-backed FBARs versus those with support layers.
Main Results:
- Achieved Q factors of 1,587 at 2.7 GHz and 769 at 5.1 GHz.
- Demonstrated enhanced sturdiness of free-standing structures with parylene.
- Reported a significant increase in electromechanical coupling (Kt2) from 3.2% to 6.8% by removing the silicon-nitride support layer.
Conclusions:
- The novel free-standing FBAR design significantly enhances Q factors.
- Parylene deposition effectively improves structural integrity.
- Air-backed FBARs offer superior electromechanical coupling, paving the way for improved device performance.