Piezoelectrically driven silicon beam force sensor

Abstract

A resonant silicon beam force sensor with piezoelectric excitation and detection is being developed. The realization is based on IC and thin-film technology with ZnO as the piezoelectrical layer. The theory, realization and measurements of a bent-frame sensors are described. A frequency shift of about 3.3 times the unloaded resonance frequency f0 (fO N 6 kHz) is measured with an external load force up to 0.4 N. The absohite sensitivity of the force sensor is 64 kHz/N and the full-scale sensitivity is 29 kHz/N. Using a simple model for the load-force transduction from external to sensor force, the measurements are in good agreement with the theory. electrical excitation and detection of the vibration of the sensor beam using the piezoelectrical effect of a ZnO layer [ 1, 31. The bottom electrode is a highly boron doped (p++-)silicon layer and the top one is an aluminium layer. In order to improve the efficiency of the electromechanical transduction of the ZnO at low frequencies, a p + +-ZnO structure is used. This structure will have a better efficiency than the pi + SiO,-ZnO (MOS) structure presented in ref. 4 because of the complete depletion of the ZnO layer [5] and the absence of a voltage drop across the oxide layer in the MOS structure.

Micro‐ and nano‐electromechanical resonators based on SiC and group III‐nitrides for sensor applications

“…flexural and longitudinal modes). The implementation of a magnetomotive 25–27 or a piezoelectric transduction Scheme 28–30 allows for an all‐electrical actuation and detection of the mechanical motion. For resonant operation, electrical signals in the rf range are necessary to match the resonant frequencies f res of the micro‐/nanometre scale devices.…”

“…Different electromechanical coupling schemes as electrostatic 22–24, magnetomotive 25–27 and piezoelectric 28–30 transduction can be applied for the electrical actuation and sensing of the mechanical motion in resonant MEMS and NEMS. In our work, the magnetomotive scheme was used for SiC and AlN resonator structures, and piezoelectrically coupled resonators were realized from AlGaN/GaN heterostructures.…”

Determination of the Drain Saturation Voltage of a Metal–Oxide–Semiconductor Field-Effect Transistor by the Capacitance–Voltage Method

“…We will discuss piezoelectric actuation using ZnO as a thin film layer on top of silicon which is not piezoelectric in itself [12], electrothermal actuation using diffused or deposited (polysilicon) heating resistors [13], and electrostatic excitation [14]. Piezoelectric actuators can be used up to very high frequencies of several 100 MHz in some SAW applications, whilst electrothermal actuation is restricted in frequency to an upper limit of 500 kHz-1 MHz.…”

Test Methods for Characterizing Piezoelectric Thin Films

“…The piezoelectric effects may be employed for strain sensing [1], actuating [2], or both in the same device [3]. The piezoelectric effects may be employed for strain sensing [1], actuating [2], or both in the same device [3].…”