Novel substrate contact structure for high-Q silicon-integrated spiral inductors

The general effects of a substrate contact near a spiral inductor on a silicon substrate are investigated. It is found that a string of substrate contacts enclosing the inductor can have beneficial or detrimental effects, depending if the inductor is configured as a one-port or a two-port structure. A 40% increase of the quality factor is found for an inductor in which the substrate contact is connected to ground. The general guidelines for an optimum inductor implementation in an integrated RF circuit are highlighted.