Characteristics of Three-Dimensional Resonant Vibration in a MEMS Silicon Beam Resonator

In this paper we report significant improvements for microelectromechanical system (MEMS) resonators. In our previous work, the reduction in gap between a driving electrode (DE) and a resonant plate was achieved by sliding DEs, showing a clear resonance at 12 MHz. However, it needed a large pull-in voltage and an elaborate measurement technique. In this study, we design soft springs for DEs and evaluate a two-port configuration to cancel feedthrough current. Measurement results show that the pull-in voltage is successfully decreased by one-third that for the previous resonator and a resonance is observed in a fabricated two-port circuit. Such a pull-in voltage can be sufficiently generated from a 2.5 V source in combination with a charge pump circuit. These results are useful for adopting the MEMS resonators to real applications.

Section: Pull-in Voltagecontrasting

confidence: 53%

Evaluation on two-port configuration of a Lamé-mode octagonal microelectromechanical systems resonator driven by sliding driving electrodes

Tsujishita

Tanigawa

Furutsuka

et al. 2015

“…Next, the device layer is anisotropically etched by ICP-RIE, and the resonator structure is formed [Fig. 6(d)], followed by the second ICP-RIE process of the substrate layer to make a trench hole for restraining the out-of-plane vibration 28) [Fig. 6(e)].…”

Section: Fabrication Processmentioning

confidence: 99%

“…In both mechanical and electrical measurements, the resonators are operated in a vacuum chamber (20-40 Pa) to decrease the air damping effect. 30)…”

Section: Measurement Setupmentioning

confidence: 99%

Lamé-Mode Octagonal Microelectromechanical System Resonator Utilizing Slanting Shape of Sliding Driving Electrodes

Okamoto¹,

Tanigawa²,

Suzuki³

2012

For high-resonant-frequency microelectromechanical system (MEMS) resonators, the reduction of the gap between the driving electrode (DE) and the resonant plate is very important, because the electromechanical coupling coefficient greatly increases to compensate for the output signal decrease. In this paper, we describe a new technique for forming a submicron narrowed gap by sliding a DE with a slanting shape. The slant gap helps to avoid the pattern size dependence in the fabrication, because each gap length is the same. By adapting the sliding DE, a Lamé-mode octagonal MEMS resonator was investigated. The fabricated resonator has the Lamé-mode resonance at 12.48 MHz. After narrowing the gap, the mechanical displacement amplitude was directly measured using a laser-Doppler vibrometer. The results show that the narrowed gap yields a great improvement (92 times) in the amplitude, compared with that before narrowing the gap. A large decrease in the absolute impedance and a large phase transition around the resonant frequency have also been observed. The influence of the experimentally obtained gap length asymmetry on the degradation of the resonators is also discussed.

“…Microelectromechanical systems (MEMS) resonators have been focused on recently, since they can achieve a high directly vibrating frequency, 1,2) a wide bandwidth, integration with peripheral circuits on the same die, 3) and flexibility in resonant frequency tuning. 4) Various types of MEMS resonators utilizing bending modes, [5][6][7] torsional modes, 8,9) and bulk modes [10][11][12][13][14][15][16][17][18][19] have been reported. The resonant frequency for torsional modes mostly depends on only beam length.…”

Section: Introductionmentioning

confidence: 99%

High Quality Factor 80 MHz Microelectromechanical Systems Resonator Utilizing Torsional-to-Transverse Vibration Conversion

Kiso¹,

Okada²,

Fujiura³

et al. 2012

A silicon microelectromechanical systems (MEMS) resonator utilizing torsional-to-transverse vibration conversion with quarter-wavelength torsional support beams is designed, fabricated, and evaluated. The resonant frequency for torsional modes mostly depends only on beam length, providing a large tolerance in the fabrication process. However, the following have remained critical issues: the increase in the quality factor (Q-factor) and the reduction in the motional resistance. We propose a new beam structure, in which the MEMS resonator utilizing torsional-to-transverse vibration conversion is anchored by four quarter-wavelength torsional support beams. First, the fabricated resonators are measured with a laser-Doppler (LD) vibrometer. The measured resonant frequency of 78.224 MHz has been in good agreement with the simulated one. The Q-factor has also been measured to be as high as 3.0×104 in vacuum. Then, the electrical characteristic is evaluated with an impedance analyzer. The Q-factor has been electrically measured to be as high as 3.1×104 in vacuum, which agrees well with the mechanically measured one of 3.0×104. The Q-factor has also been electrically measured to be as high as 1.3×104 at atmospheric pressure. In the measurement, a spring softening effect has been clearly observed. By increasing the DC bias voltage from 20 to 40 V, the resonant frequency has decreased by 640 Hz. The extracted motional resistance for a 0.1-µm-gap resonator has been greatly reduced to 0.039 MΩ at 5 V DC, owing to the narrow-gap effect, from that of a 0.25-µm-gap resonator. The tolerance in the fabrication process has also been evaluated and successfully verified from the measurement of the fabricated MEMS resonators.