An electrostatic charge sensor based on micro resonator with sensing scheme of effective stiffness perturbation

Abstract

A resonant electrostatic charge sensor with high sensitivity based on micro electromechanical systems (MEMS) technology is proposed to measure electric charge. Input charge produces lateral electrostatic force to change effective stiffness of double-ended tuning forks resonator, and leads to a resonant frequency shift. The sensitivity of the charge sensor is 4.4 × 10 −4 Hz fC −2 . The proposed sensing scheme of effective stiffness perturbation has higher sensitivity than the traditional axial strain sensing methods. Experimental results show that the frequency modulation has better resolution and stability than the amplitude modulation. The proposed sensing scheme also creates additional energy transmission paths inside the device to improve quality factor and stabilize frequency fluctuation. The instability of resonant frequency induced by mechanical nonlinearity are investigated.

On the response of MEMS resonators under generic electrostatic loadings: experiments and applications

“…The quadratic responsivity of the electrometer is found out to be ~10 -5 Hz fC -2 after polynomial fitting of the measured data. The responsivity reported here is one of the lowest reported in MEMS based electrometers [40][41][42][43]. This shows that such a technique is potentially capable of detecting very small charges.…”

“…This effect can be used for applications where the detection of a very small increase in the DC bias is desired. One such application can be in charge sensing or MEMS electrometer [40][41][42][43]. Shift in 6.…”

“…Furthermore, a minimum detectable frequency shift of the resonator needs to be determined, which can be calculated by measuring the frequency fluctuation at the point of interest using Alan deviation technique [38]. It usually lies within a few Hz range for the MEMS beam resonators [40][41][42][43]48]. It is important to note here that for demonstration purpose the bifurcation point is used for monitoring the input charge, however frequency fluctuations due to noise near the bifurcation point maybe large.…”

“…Furthermore, an AC excitation based device that can detect small amount of charge is also desired for applications in MEMS electrometers [40][41][42][43]. Different dynamics phenomenon that respond to an input charge in terms of frequency shift via stiffness perturbation [40][41][42], and amplitude shift through principles like mode localization [43] have been used to demonstrate these electrometers.…”

Room-Temperature Sensing of Single Electrons Using Vibrating-Reed Electrometer in Silicon-on-Glass Technology

“…By selecting a lower voltage noise opamp, the further reduction of the noise floor of the readout circuit could be possible for improving charge resolution to subelectrons. The high charge sensitivity of SOG-MEMS electrometer Transistor -Ambient -63k 2014 [18] Transistor -Ambient -6.3k 2017 [6] Resonator SOI 33 mTorr 4.4×10 −4 Hz/f C 2 203k 2015 [4] Resonator SOI 40 mTorr 1.3×10 −3 Hz/f C 2 131k 2008 [3] Resonator SOI 4 mTorr 1.2×10 −3 Hz/f C 2 25k 2018 [7] Resonator SOI Vacuum 7.86×10 −3 Hz/f C 2 16k 2016 [5] Resonator SOI 20 mTorr 6.3×10 −4 Hz/f C 2 7.9k 2018 [8] Resonator shows the potential in low-cost, portable instrumentation systems. The temperature sensitivity, long-term output drift and system integration of the sensor will be investigated in our future work.…”