On the Dynamic Range and Resolution of Thermal-Piezoresistive Resonant Mass Sensors

Hemin Zhang,Linlin Wang,Michael Kraft,Aojie Quan,Chen Wang,Chenxi Wang

doi:10.1109/jmems.2022.3141830

Abstract

Thermal-actuation and piezoresistive-detection effects have been employed to pump the effective quality factor of MEMS resonators, targeting better mass sensing performance in air. In this paper, frequency resolution (bias instability) of a thermal-piezoresistive resonator operating in air at room temperature is experimentally investigated. It is found that the dynamic range decreases when increasing the bias direct current whereas the effective quality factor rises. The measurement results indicate a maximum effective quality factor of 169k with a dynamic range of 47.8 dB for a bias current of 6.25 mA, and a minimum effective quality factor of 11.3k with a dynamic range of 70.1 dB for a bias current is 5.8 mA. Our work also shows that the frequency and amplitude bias instabilities are significantly lower due to the dynamic range decrease for a high bias current. [2021-0250]

Highlights

M ICROELECTROMECHANICAL resonators have been employed in various sensing applications, such as mass sensors [1] and resonant accelerometers [2]
To obtain a high mass resolution, MEMS resonant mass sensors need to be designed with a low effective weight (Me f f ) and a high quality (Q) factor, since the mass resolution is defined as [3]: δ M/Me f f ≈ 2δω/ω0 where δ M is the minimum detectable mass and δω/ω0 is the frequency resolution that is normally represented by frequency bias instability
It has been theoretically demonstrated that the frequency stability is determined by two important parameters [1]: the inherent mechanical Q factor and dynamic range (DR): δω/ω0

Summary

INTRODUCTION

M ICROELECTROMECHANICAL resonators have been employed in various sensing applications, such as mass sensors [1] and resonant accelerometers [2]. Thermal-actuation and piezoresistive-detection principles have been demonstrated as beneficial to pump the effective quality factor (Qeff ) [8] in air. The sensor resolution of TPR with pumped Qeff as mass sensors has not been investigated yet. It is not clear whether Idc influences DR, and whether this leads to improved frequency stability/resolution, since it was reported that DR and frequency stability would benefit from a larger damping dissipation [12]. The influences of the thermal-piezoresistive pumping effect on the dynamic range, frequency stability and sensor resolution of a TPR are experimentally investigated

DEVICE DESCRIPTION AND MEASUREMENT SETUP

Thermal-Piezoresistive Principle

Electrical Setup

Dynamic Range Measurements

CONCLUSION