High- Q UHF Spoke-Supported Ring Resonators

• Published in: Journal of microelectromechanical systems Vol. 25; no. 1; pp. 11 - 29
• Main Authors: Naing, Thura Lin, Rocheleau, Tristan O., Zeying Ren, Sheng-Shian Li, Nguyen, Clark T.-C
• Format: Journal Article
• Language: English
• Published: IEEE 01.02.2016
• Subjects: bandpass filter; Capacitance; Couplings; diamond; Electrodes; high-<italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <inline-formula> <tex-math notation="LaTeX"> Q </tex-math> </inline-formula>; Microelectromechanical systems (MEMS); micromechanical resonator; Optical ring resonators; polysilicon; quarter-wavelength; Radio frequency; Resonant frequency; Structural rings; ultra-high frequency (UHF); ultra-high frequency (UHF); quarter-wavelength; diamond; bandpass filter; micromechanical resonator; Microelectromechanical systems (MEMS); high- Q; polysilicon
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2015.2480395

A vibrating micromechanical spoke-supported ring resonator employing a central peg-anchor, balanced non-intrusive quarter-wavelength extensional support beams, and notched support attachments attains high Q-factor in vacuum, posting 10000 at 441 MHz when made of polysilicon structural material and 42900 at 2.97 GHz when made of microcrystalline diamond. The latter marks the highest f · Q of 1.27×10 14 for any acoustic resonator at room temperature, besting even macroscopic bulk-mode devices. Very high Q values like these in a device occupying only 870 μm 2 pave a path toward on-chip realizations of RF channelizers and ultra-low phase-noise gigahertz oscillators for secure communications. With frequency determined by lithographically defined ring-width rather than radius, a capacitive transducer with a 75-nm gap allows this 2.97-GHz version to achieve a series motional resistance of 81 kQ. Though still higher than desired, this marks a 30× improvement over previous pure polysilicon surface-micromachined solid disk resonators in the gigahertz range, and if predicted performance-scaling holds true, seven such resonators constructed in a mechanically coupled array with 30-nm gap spacing, could lower this to only 300 Ω. Confidence in a prediction like this stems from the confirmed accuracy of the electrical equivalent circuit described herein that models not only the ring and its transducers, but also its supports.