Record Q symmetrical inductors for 10-GHz LC-VCOs in 0.18-μm gate-length CMOS

We report a single-loop inductor suitable for integration in a differential voltage-controlled oscillator (LC-VCO) with 0.6-nH inductance and record quality factors of 18 at 10 GHz and 20 at 15 GHz fabricated in an industrial CMOS process on a 10 /spl Omega/cm substrate. A new lumped element model which accurately describes the inductor performance without the need for frequency-dependent elements is presented. During the course of this work, we found that a patterned ground shield significantly improves the inductor performance at these frequencies, but only when the polysilicon bars are connected from the center of the inductor.