Properties of contactless and contacted charging in MEMS capacitive switches

Abstract

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

Induced charging phenomena on SiNx dielectric films used in RF MEMS capacitive switches

“…Fig. 4 presents the shift of CV characteristics of a MEMS capacitive switch to more negative voltages after successive contact-less charging with +16 V. This shift represents the compensation procedure which takes place during contact-less charging that is analytically described in [4,5].…”

“…The induced contact-less charging has been shown to have polarity opposite to the contacted one [4,5] thus giving rise to a compensation mechanism. The contribution of each process to the total polarization of the dielectric film has been recently investigated in [5] but the properties of induced charging mechanisms are not yet fully understood.…”

“…The contribution of each process to the total polarization of the dielectric film has been recently investigated in [5] but the properties of induced charging mechanisms are not yet fully understood. The induced charging and the degree of polarization's compensation are expected to depend on the material properties and therefore on the deposition conditions.…”

A MIM capacitor study of dielectric charging for RF MEMS capacitive switches

“…Regarding the dielectric charging, three major modes are acknowledged as responsible up to date. Two of them are usually referred as contactless charging and arise by either redistribution of internal charges and/or dipoles orientation [2][3][4], or by injection of electrons emitted by asperities at the bottom of the metal bridge due to field emission [5,6]. Such effects occur in the non contact areas that are formed between the dielectric film and the bridge in the down state condition due to surface roughness but also in the up state before the device actuation.…”

Assessment of dielectric charging in micro-electro-mechanical system capacitive switches

“…The trapped charge gives rise to shift of pull-in and pull-out voltages and finally to device failure due to stiction [4], [8]. Another charging mechanism is the induced charging that under certain conditions that can be large enough to give rise to compensation [9], [10].…”