Double-level spiral inductors with multiple-via interconnects on GaAs substrates

In this letter, we report the electromagnetic characteristics of on-chip double-level square spiral inductors. The inductors are unique in that the double-level spirals are interconnected by multiple vias with one air bridge, instead of the usual "single-via-at-center" interconnect. Two double-level (DL) spiral inductors synthesized using multiple vias interconnect embedded in the polyimide layer on GaAs substrates are characterized based on their S-parameters measured using the de-embedding technique. Such double-level spiral structures are different from the usual "single-via-at center" interconnect between two neighboring metal levels. The inductance and Q-factor each of these inductors are extracted and also compared with those of single-level (SL) cases. We show that, in spite of a decrease in resonant frequency, inductance as well as Q factor are greatly improved over those of single-level spiral geometries, and this could be due to the enhancement of electromagnetic coupling between double spirals.