High-Q on-chip inductors using thin-film wafer level packaging technology demonstrated on a 90 nm RF-CMOS 5 GHz VCO

High-Q inductors are important for the realization of high-performance, low-power RF-circuits. In this work, on-chip inductors with Q-factors above 40 have been realized above the passivation of a 90 nm RF-CMOS process using wafer-level packaging (WLP) techniques. The influence of a patterned polysilicon and metal ground shield on the inductor-Q is compared and the influence of highly doped active area underneath the inductors is shown. A 5-15 GHz WLP balun has been realized. The technology is demonstrated by a low-power 5GHz 90nm RF-CMOS VCO with a core current consumption of only 430 μA from a 1.2 V supply, a phase noise of -112dBc/Hz at 1MHz offset and a tuning range of 530MHz.