High Q broadband copper spiral inductors with Q=45 on proton-bombarded semi-insulating silicon substrate

This paper reports the highest Q-factor inductor on silicon substrate. A local semi-insulating region under the 3mum-thick copper spiral inductor is created by high-energy proton bombardment. For a single-layer spiral 1.5 nH inductor, we obtained Q-factor greater than 25 over broad frequency band from 5-19 GHz and with the highest value being 45. Modeling of the inductor equivalent circuit shows that indeed the improvement of q-factor realists from the increase in the substrate resistivity.