Phononic Crystals with Adiabatic Transitions for Full Acoustic Confinement in MEMES Resonators
This technology has applications in:
- Communications and radio frequency (RF)
- Electronic systems needing sharp and monolithically integrated filters
- Solid state high-Q MEMS resonators
- Timing and clocks
- Modulating lasers for on-chip optical waveguides
- Narrow-band lasers and optical filters
Researchers
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apparatus, systems, and methods of acoustic energy confinement with phononic crystals
Patent Cooperation Treaty | Published application
Figures
Fig. 1: (a) Cross-section SEM of a CMOS-MEMS resonators showing PnC patterned in metal stack and FEOL resonant cavity (b) details of resonant cavity showing driving and sensing transducers.
Fig. 2: (a) Unit cell of the PnC implemented in this design (b) Irreducible Brillouin zone showing directions of k-vector scan. (c) COMSOL simulation of the PnC unit cell showing bandgap a bandgap between 2.80 GHz and 6.27 GHz. wide bandgap centered at 4.5 GHz (Fig. 2(c)). Upper metal levels have a different thickness which causes them to break the periodicity of the PnC. To simplify design, these upper metals were excluded using CMP fill exclusi
Fig. 3: Top view of PnC resonator showing driving and sensing transistors, gates, modified contacts, first metal level and bulk ties. Metals layers are excluded for clarity of underlying structure.
Technology
The invention is a novel way of guiding elastic waves and confining mechanical vibrational energy using phononic crystals and adiabatic (slow) transitions in a completely solid-state commercial CMOS stack. This requires that phonons, quanta of sound, are completely contained within the CMOS die. The result is a 35 times improvement in the Q-factor of the phononic crystal CMOS resonant body transistors (PnC-CMOS RBTs). The invention can also be used as a phononic trap or coupled with on-chip micro- and nano-photonics to achieve on-chip opto-mechanical coupling. The invention is applicable in all operational frequencies which can be fabricated by current CMOS technologies.
Problem Addressed
MEMS resonators are high-Q, narrow-band filters are used in communications and RF applications. The high-Q, narrow-band filters lead to a more selective filter and the oscillators have a lower phase noise over conventional designs. However, current designs are not fully solid-state and require post processing which cannot be fully integrated.
Advantages
- 35x quality factor improvement over phononic crystal CMOS resonant body transistors
- Low-phase noise oscillators eliminate the need for bulky Quartz crystals
Publications
B. Bahr, R. Marathe, and D. Weinstein. "Phononic Crystals for Acoustic Confinement in CMOS-MEMS Resonators." In 2014 IEEE International Frequency Control Symposium (FCS), 1-4. Taipei, Taiwan, 2014. doi: 10.1109/FCS.2014.6859980.
S. Mohammadi and A. Adibi. "Waveguide-Based Phononic Crystal Micro/Nanomechanical High-Q Resonators." Journal of Microelectromechanical Systems 21, no. 2 (April 2012): 379-384. doi: 10.1109/JMEMS.2011.2174426.
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