Glass Polarization Induced Drift of a Closed-Loop Micro-Accelerometer.

Wu Zhou ,Bei Peng,Xiaoping He,Huijun Yu,Junpeng He

doi:10.3390/ma11010163

Abstract

The glass polarization effects were introduced in this paper to study the main cause of turn-on drift phenomenon of closed-loop micro-accelerometers. The glass substrate underneath the sensitive silicon structure underwent a polarizing process when the DC bias voltage was applied. The slow polarizing process induced an additional electrostatic field to continually drag the movable mass block from one position to another so that the sensing capacitance was changed, which led to an output drift of micro-accelerometers. This drift was indirectly tested by experiments and could be sharply reduced by a shielding layer deposited on the glass substrate because the extra electrical filed was prohibited from generating extra electrostatic forces on the movable fingers of the mass block. The experimental results indicate the average magnitude of drift decreased about 73%, from 3.69 to 0.99 mV. The conclusions proposed in this paper showed a meaningful guideline to improve the stability of micro-devices based on silicon-on-glass structures.

Highlights

Drift issue is considered as a big obstacle to developing highly-precise microelectromechanical systems (MEMS) products
The glass polarization effect induced by the DC bias voltage which was used to form a feedback
The glass polarization effect induced by the DC bias voltage which was used to form a feedback force in the closed-loop system was considered as one of the main causes of turn-on drift of force in the closed-loop system was considered as one of the main causes of turn-on drift of micromicro-accelerometers in this paper

Summary

Introduction

Drift issue is considered as a big obstacle to developing highly-precise microelectromechanical systems (MEMS) products. It does not seem reasonable to consider the thermal drift as the underlying mechanism in explaining the long-term drift phenomenon in closed-loop micro-accelerometers during the turn-on period, since the time scale of the drift, from tens of minutes to a few hours, is much longer than the preheating process, normally under a few minutes Such a long-time drift observed in experiments might result from the dielectric charging of dielectric materials in the micro-accelerometer, because the charging effects of dielectrics, such as oxide silicon, nitride silicon, and glass involved a slow process of charge movement and took a long time to finish.

Materials and Structure

Polarization

Glass polarization mechanism mechanismunder underan an appliedDC

Findings

Experiment and Discussion

Conclusions