Record Q spiral inductors in standard CMOS

Abstract

High-Q spiral inductors, either realized as discrete elements in thin-film technologies, or as integrated components in IC processes, are essential to realize key RF circuitry like VCO's and LNA's. We have demonstrated for the first time that by dividing a spiral inductor into four parallel current paths of equal resistance and inductance current crowding can be suppressed, allowing a record Q of 15 for a 2 GHz 5 nH inductor in standard CMOS, representing a 40 % improvement over previous art. The proposed division into parallel current paths can be realized without process modifications, reduces CMP dishing, and is expected to provide even larger performance gains in terms of quality factor Q and inductor area for IC and thin-film processes employing thicker metal layers and low-K materials.