Title :
Phononic crystals for acoustic confinement in CMOS-MEMS resonators
Author :
Bahr, Bichoy ; Marathe, Radhika ; Weinstein, D.
Author_Institution :
EECS, Massachusetts Inst. of Technol., Cambridge, MA, USA
Abstract :
This work presents the first implementation of phononic crystals (PnCs) in a standard CMOS process to realize high-Q RF MEMS resonators at GHz frequencies without the need for any post-processing or packaging. An unreleased acoustic resonant cavity is defined using a PnC comprising back-end of line (BEOL) materials such as routing metals and low-k intermetal dielectric. A CMOS-MEMS resonant body transistor (RBT) with electrostatic driving and piezoresistive sensing is implemented within this cavity. This results in a 10× enhancement in Q at resonance and improved suppression of spurious modes off-resonance as compared to first-generation CMOS-integrated devices. The first PnC-confined RBT is demonstrated in IBM´s 32 nm SOI process at 2.8 GHz with Q of 252, spanning a footprint of 5 μm × 7 μm.
Keywords :
CMOS integrated circuits; acoustic resonators; low-k dielectric thin films; micromechanical resonators; microwave resonators; phononic crystals; silicon-on-insulator; BEOL materials; CMOS process; CMOS-MEMS resonators; GHz frequencies; IBM; PnC-confined RBT; SOI process; acoustic confinement; acoustic resonant cavity; back-end of line; electrostatic driving; first-generation CMOS-integrated devices; frequency 2.8 GHz; high-Q RF MEMS resonators; low-k intermetal dielectric; phononic crystals; piezoresistive sensing; resonant body transistor; routing metals; size 32 nm; size 5 mum; size 7 mum; spurious modes off-resonance; Acoustics; Cavity resonators; Logic gates; Metals; Resonant frequency; Sensors; Transistors;
Conference_Titel :
Frequency Control Symposium (FCS), 2014 IEEE International
Conference_Location :
Taipei
DOI :
10.1109/FCS.2014.6859980
