Temperature effects on the bulk discharge current of dielectric films of MEMS capacitive switches

Kelvin probe method has been directly applied to capacitive MEMS switches in order to investigate temperature activated mechanisms in PECVD Silicon Nitride (SiNx) films. The bulk discharge current of MEMS capacitive switches has been determined for different charging and discharging temperatures, in the range of 300–400 K. The increase of discharging temperature leads to an increase of the magnitude of the bulk discharge current and the relaxation time of the discharging process is found to be thermally activated. Finally, it is shown that the increase of charging temperature assists trapping at centers characterized by time constants even longer than the time window of observation, i.e. 10^4 s

Determination of bulk discharge current in the dielectric film of MEMS capacitive switches

The present work presents a new method to calculate the discharge current in the bulk of dielectric films of MEMS capacitive switches. This method takes into account the real MEMS switch with non uniform trapped charge and air gap distributions. Assessment of switches with silicon nitride dielectric film shows that the discharge current transient seems to obey the stretched exponential law. The decay characteristics depend on the polarization field’s polarity, a fact comes along with experimental results obtained from thermally stimulated depolarization currents (TSDC) method used in MIM capacitors

Charging and Discharging Processes in AlN Dielectric Films Deposited by Plasma Assisted Molecular Beam Epitaxy

In the present work the electrical properties of AlN polycrystalline films deposited at low temperatures by plasma-assisted molecular beam epitaxy (PA-MBE) are investigated. The polarization build-up during constant current injection as well as the depolarization process after the current stress have been investigated through monitoring voltage transients in Metal – Insulator – Metal (MIM) capacitors, in temperature range from 300 K to 400 K. Moreover, current – voltage characteristics obtained at different temperatures revealed that charge collection at low fields in these films occurs through variable range hopping

Properties of contactless and contacted charging in MEMS capacitive switches

The dielectric charging in MEMS capacitive switches is a complex effect. The high electric field during pull-down causes intrinsic free charge migration and dipole orientation as well as charge injection. The macroscopic dipole moment of the first two mechanisms is opposite to the one arising from charge injection. This causes partial compensation hence mitigates the overall charging and increases the device lifetime. The charging due to intrinsic free charge migration and dipole orientation can be monitored under contactless electric field application in the pull-up state. The paper investigates the characteristics of contactless charging and compares them with the ones of contacted charging. The characteristics of the discharging process that follows each charging procedure are also presented

Determination of long time discharge current in microelectromechanical system capacitive switches

An improved method to study the long term discharge current through the dielectric film in microelectromechanical system capacitive switches is presented. The method allows the detection of currents in the sub-fempto-Ampere range by monitoring the decay of the bias for minimum capacitance in the pull-up state. The method has been applied for time interval in excess of 10 000 s. Finally, it is shown that in carefully designed devices the method allows the calculation of the current that arises from the charge fluctuation decay. © 2011 American Institute of Physics

Temperature effects on the bulk discharge current of dielectric films of MEMS capacitive switches

Kelvin probe method has been directly applied to capacitive MEMS switches in order to investigate temperature activated mechanisms in PECVD Silicon Nitride (SiN x) films. The bulk discharge current of MEMS capacitive switches has been determined for different charging and discharging temperatures, in the range of 300-400 K. The increase of discharging temperature leads to an increase of the magnitude of the bulk discharge current and the relaxation time of the discharging process is found to be thermally activated. Finally, it is shown that the increase of charging temperature assists trapping at centers characterized by time constants even longer than the time window of observation, i.e. 10 4s. © 2012 Elsevier Ltd. All rights reserved

A novel method for the assessment of surface charge density variance in capacitive RF-MEMS switches

The present paper provides a novel, inexpensive and non-destructive method to assess the surface charge density variance in capacitive RF-MEMS switches. The charge variance evolution can be monitored during charging and discharging processes by measuring the up-state capacitance, in addition to the mean value, providing results directly related to charging failure mechanisms and the prediction of the devices lifetime for unipolar/bipolar actuation. Also, the experimental results can be used to engineer the dielectric film electrical properties in order to control the surface and bulk conductivities according to needed application. © 202

A study of material stoichiometry on charging properties of SiNx films for potential application in RF MEMS capacitive switches

This work presents an in depth investigation regarding the effect of PECVD silicon nitride (SiNx) stoichiometry on its charging mechanisms. The investigation took place in SiNx dielectric films with different Si-content (x = 0.47–1.04) with the aid of Metal-Insulator-Metal capacitors. The experimental assessment involved a single-point Kelvin probe System, the monitoring of Current – Voltage characteristics and the employment of Thermally Stimulated Depolarization Currents technique. The results indicate that when Si-content increases the injected charge distribution is expected to extend deeper in the dielectric films and charges are displaced faster through the bulk material and towards the bottom electrode. The effective temperature is used in order to investigate hopping conduction that dominates charge transport in the bulk material and thus a more realistic approach of the discharging process is presented. Finally, the increase of Si-content seems to introduce defect states in SiNx, which are probably associated to Si-dangling bonds, and the presence of discrete depolarization mechanisms are investigated, the characteristics of which are analytically described taking into consideration the effect of stoichiometry. These results that can be useful in material engineering in order to improve the lifetime of RF MEMS capacitive switches. © 2020 Elsevier Lt