HIGH PERFORMANCE SILICON-BASED INDUCTORS FOR RF INTEGRATED PASSIVE DEVICES

High-Q inductors are realized on a 3–8Ω · cm silicon substrate in the buildup of BCB/Cu. Anisotropic wet etching is utilized to remove the silicon in the cavities underneath the spirals from the backside. Examples of 3.5-turn spiral inductors with and without cavity are compared, and their parameter extractions are accomplished with an equivalent circuit model. Compared to the inductor without cavity, the measured peak quality factor of a 8.19-nH inductor with cavity increases from 24 at 0.8GHz to 39 at 2.5 GHz by 67%, and the inductor with cavity has a wider bandwidth using the same equivalent model. The inductors utilizing this technique have a potential wide application in hand-held RF modules either as part of an off-chip device or as an integrated passive in a silicon interposer.