Influence of fabrication tolerances on the reliability of RF-MEMS capacitive switches

In this paper the comparison between ideal mechanical and electrical performances and measured ones is presented for one of the most common type of switch typology, the RF-MEMS clamped-clamped capacitive switch. The main sources of deviation from design assumptions and ideal behavior occurring during fabrication are found and examined in detail. They can be summarized in a measurable deviation from planarity and thickness non-uniformity of the membrane, a low contact force even for a capacitive switch and a mismatch in the thicknesses of the structural layers, which might be considered an advantage in the design phase, but is an intrinsic weakness in the real device.