Dielectric Engineering of Nanostructured Layers to Control the Transport of Injected Charges in Thin Dielectrics
Résumé
A new concept concerning dielectric engineering is presented in this study aiming at a net improvement of the performance of dielectric layers in RF MEMS capacitive switches with electrostatic actuation and an increase of their reliability. Instead of synthesis of new dielectric materials, we have developed a new class of dielectric layers that gain their performance from design rather than from composition. Two kinds of nanostructured dielectrics are presented. They consist of 1) silicon oxynitride layers (SiOxNy:H) with gradual variation of their properties (discrete or continuous) and 2) organosilicon (SiOxCy:H) and/or silica (SiO 2) layers with tailored interfaces; a single layer of silver nanoparticles (AgNPs) is embedded in the vicinity of the dielectric free surface. The nanostructured dielectric layers were deposited in a plasma process. They were structurally characterized and tested under electrical stress and environmental conditions typical for RF MEMS operation. The charge injection and decay dynamics were probed by Kelvin force microscopy. Modulation of the conductive properties of the nanostructured layers over seven orders of magnitude is achieved. Compared to dielectric monolayers, the nanostructured ones exhibit much shorter charge retention times. They appear to be promising candidates for implementation in RF MEMS capacitive switches with electrostatic actuation, and more generally for applications where surface charging must be avoided.
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