Clamped Beam Resonators Research Articles

Resonance frequency and quality factor tuning in electrostatic actuation of nanoelectromechanical systems

In an electro statically actuated nanoelectromechanical system (NEMS) resonator, it is shown that both the resonance frequency and the resonance quality (Q) factor can be manipulated. How much the frequency and quality factor can be tuned by excitation voltage and resistance on a doubly—clamped beam resonator is addressed. A mathematical model for investigating the tuning effects is presented. All results are shown based on the feasible dimension of the nano resonator and appropriate external driving voltage, yielding up to 20 MHz resonance frequency. Such parameter tuning could prove to be a very convenient scheme to actively control the response of NEMS for a variety of applications.

Voltage-tunable piezoelectrically-transduced single-crystal silicon micromechanical resonators

Abstract This paper reports on a new class of high-Q single-crystal silicon (SCS) resonators that are piezoelectrically actuated and sensed, and have voltage-tunable center frequencies. The resonating element is made out of the SCS device layer of a SOI wafer. In a unique manner, piezoelectric transduction was integrated with capacitive fine-tuning of the resonator center frequencies to compensate for any process variations. Quality factor as high as 6200 was measured for the 1.7 MHz first resonance mode of a clamped–clamped beam resonator in 50 mTorr vacuum. Higher order modes of the fabricated resonators were also successfully actuated and demonstrated quality factors larger than 2000 (under vacuum) at frequencies approaching 17 MHz. A 6 kHz tuning range was measured for a 719 kHz resonator by applying a dc voltage in the range of 0–20 V.

Released submicrometer Si microstructures formed by one-step dry etching

Microstructures with submicrometer gaps in Si were fabricated by etching with Cl2 and F-based gases in inductively coupled plasma systems. Released cantilevered beams with a 0.1 μm gaps and 4 μm thick were fabricated using Cl2 etching. Etching in Cl2 provides vertical profile and smooth morphology for submicrometer trenches. It has been applied to form a clamped–clamped beam resonator with 0.2 μm gaps between the resonating beam and electrodes. For trenches with 0.1 μm openings, the F-based etching resulted in tapered etch profile and the top of the trenches was eventually closed due to polymer deposition. Based on faster lateral etch rate for n++ Si in Cl2 etching, a one step dry etching process was used to pattern and release microstructures from the substrate. Residues on the surface after F-based etching can be removed by overetching and the charging effect can be avoided by etching in Cl2.