Showing papers by "Roozbeh Tabrizian published in 2014"
TL;DR: In this paper, a dual-mode AlN-on-silicon micromechanical resonators for self-temperature sensing were proposed, which provides a 50× improvement in temperature coefficient of beat frequency (TCfb) compared with single-mode temperature measurement and eliminates the need for additional frequency multipliers to generate fb from its constituents.
Abstract: In this paper, we present dual-mode (DM) AlN-on-silicon micromechanical resonators for self-temperature sensing. In-plane width-shear (WS) and width-extensional (WE) modes of [110]-oriented silicon resonators have been used as alternatives to first- and third-order modes to enhance DM temperature sensitivity by engineering device geometry, which reduces inherent beat frequency fb between the two modes. This configuration provides a 50× improvement in temperature coefficient of beat frequency (TCfb) compared with single-mode temperature measurement and eliminates the need for additional frequency multipliers to generate fb from its constituents. [100]-oriented WS/WE resonators provide 4× larger TCF difference between modes (ΔTCF) than first and third width-extensional resonators, which further contributes to TCfb enhancement. WS/WE mode resonators also demonstrate the capability of operating as a temperature-stable reference fb. The proposed modes for DM operation have high Q and low motional resistance, and are 180 ° out-of-phase when operated in two-port configuration, thus enabling mode-selective low-power oscillator interfacing for resonant temperature sensing.
44 citations
13 Mar 2014
TL;DR: In this paper, a dual-mode resonant pressure sensor operating based on mass loading of air molecules on transversely resonating vertical silicon membranes is presented, where two SiBARs are acoustically coupled through thin vertical membranes, resulting in two high-g resonance modes with small frequency split, but large difference in pressure sensitivity.
Abstract: This paper presents a novel dual-mode resonant pressure sensor operating based on mass loading of air molecules on transversely resonating vertical silicon membranes. Two silicon bulk acoustic resonators (SiBAR) are acoustically coupled through thin vertical membranes, resulting in two high-g resonance modes with small frequency split, but large difference in pressure sensitivity. The membranes are designed to couple 180° out-of-phase vibrations of piezoelectrically-transduced SiBARs through pressure-insensitive extensional Lamb waves and without changing their resonance frequency. The in-phase vibrations, on the other hand, induce a high-order pressure-sensitive transverse flexural resonance in vertical membranes while slightly changing the resonance frequency of SiBAR due to stiffness and mass loading. A combinatorial of the two modes is used as a pressure sensor with an amplified sensitivity. A proof-of-concept device implemented on a 20 μm silicon substrate and activated by a thin aluminum nitride film shows a combinatorial beat frequency (fb) of 1.3 MHz with a linear pressure sensitivity of 346 ppm/kPa over 0-100kPa range.
10 citations
30 May 2014
TL;DR: In this paper, an energy-trapped resonance mode is synthesized from acoustic coupling of evanescent and propagating phonons with opposite temperature sensitivity trends in a <100>-aligned engineered waveguide (phonon trap).
Abstract: This paper reports on a novel temperature-compensated single-crystal silicon resonator that has a quadratic temperature characteristic with a high turn-over temperature. An energytrapped resonance mode is synthesized from acoustic coupling of evanescent and propagating phonons with opposite temperature sensitivity trends in a <100>-aligned engineered waveguide (phonon trap). A 77MHz device implemented in AlN-on-silicon platform shows a Q of 13,000 and a turn-over temperature of 87°C facilitating implementation of an oven-controlled frequency reference. An oscillator implemented using this device, while selfovenized by a DC current passing through its body, exhibits a consistent phase-noise of -106 dBc/Hz at 1kHz offset from carrier.
1 citations