A Study of On-Chip Stacked Multiloop Spiral Inductors

This paper proposes a new differential topology that features a stacked multiloop inductor. Comparative studies of stacked one- to four-loop spiral inductors with and without patterned ground shields (PGSs) for silicon-based radio-frequency integrated circuits (RFICs) were conducted, and lumped-element circuit models were developed for these inductors. The partial-element equivalent-circuit method that can accurately analyze mutual inductive couplings among different spirals in these multiloop geometries was employed for capturing the frequency-dependent inductances and resistances of inductors at low frequencies. A good agreement between numerical results and measurements is obtained. It is demonstrated that a stacked multiloop spiral inductor with differential topology and PGS has a larger inductance and a higher Q-factor as compared with the same inductor without differential topology and PGS. This hybrid methodology could provide a promising technique for developing new silicon-based passive devices used in RFICs.