Monolithic high-Q overhang inductors fabricated on silicon and glass substrates

We have investigated the RF performance of the micromachined integrated spiral inductors overhanging several tens of microns from the substrate, having at least 10 /spl mu/m in copper thickness. From the experiments, it can be speculated that once the inductor is overhung by at least 30 /spl mu/m, the substrate coupling can be eliminated almost completely, even in the standard silicon substrate, as long as there is no additional support. The inductor overhanging 30 /spl mu/m from the standard silicon substrate has shown an inductance of 1.8 nH with the unprecedented peak Q-factor of 50 at 7 GHz.