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 5 GHz 90 nm RF-CMOS VCO with a core current consumption of only 430 mu A from a 1.2 V supply, a phase noise of -112 dBc/Hz at 1 MHz offset and a tuning range of 530 MHz.

A novel low-power 90 nm CMOS 5.8 GHz voltage-controlled oscillator using a high quality thin-film post-processed inductor is presented. This 5.8 GHz VCO has a power consumption of 328 muW with a supply voltage of 0.82 V, and a phase noise of -115 dBc/Hz at 1 MHz offset over a 148 MHz tuning range. To the authors' knowledge, this VCO is the lowest power dissipated 5 GHz CMOS VCO reported.