Coplanar passive circuits on surface micromachined silicon and thick polymer layers for millimeter-wave applications

In this paper, we report a novel technological issue for the realization of low loss coplanar passive circuits on low resistivity (LR-20 Ω.cm) silicon substrates using simultaneously a silicon surface micromachining in the slots and a thick polymer layer (BCB). The silicon etching into the coplanar slots leads indeed to a noticeable decrease of the losses, whereas filling the coplanar gaps with the low loss polymer minimizes the field interaction with the lossy silicon substrate and results in a much higher quality factor.