A study of field emission process in electrostatically actuated MEMS switches

Abstract

a b s t r a c tA study of field emission process in MEMS-based capacitor/switch-like geometries is presented. High resolution current-voltage characteristics up to breakdown have been obtained across micro-gaps in fixedfixed Metal-Air-Metal and Metal-Air-Insulator-Metal structures. In metallic devices the I-V dependence reveals Fowler-Nordheim theory effects. In the presence of insulator the process is found to be limited by the film conductivity following Poole-Frenkel dependence. The data analysis reveals the major importance of surface asperities on the onset of the field emission process while it is also presented that charge transfer may occur between metal and insulator surfaces even in the presence of micrometer scale gaps.

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

“…Among these, the dominant ones are the space charge and the dipolar polarization mechanisms that occur simultaneously, while the contribution from field emission processes is also significant for strong applied electric fields [6].…”

“…Charge injection gives rise to "contacted" charging, thus producing an additional charge density σ fe in the dielectric film, while the moving armature is still in the pull-up state [6,7]. It is important to notice that both mechanisms, contact-less and contacted charging, occur during the pull-down state.…”

Properties of contactless and contacted charging in MEMS capacitive switches

“…In the specific case of capacitive switches with stiff bridge and therefore with large pull-down voltage, the case of power devices operating at bias levels close but below pull-down, field emission may occur. Then charges may be injected into dielectric film and give rise to ''contacted'' charging, thus producing an additional charge density r 0 ext in the dielectric film, while the moving armature is still in the pull-up state [12,13]. Here it must be pointed out that this condition can be achieved by the superposition of power RF signal, the different work functions of the moving armature metal and the dielectric film composition.…”

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.…”