Monolithically integrated 3-D micro-inductors and micro-transformers for RF applications

To meet requirements in mobile communications and microwave integrated circuits, miniaturization of the passive components that many of these systems require is of key importance. In this paper, spiral and solenoid-type RF micro-inductors and micro-transformers with 3-D structures have been newly designed, fabricated, and characterized on GaAs and silicon substrates by using electroplating techniques, multi-layer thick photoresist, and low temperature processes. The applied processing techniques are also compatible with MMIC, RFIC, and CMOS circuitry fabrication due to their simple fabrication steps. In particular, relationship of performance characteristics and geometry of spiral and solenoid micro-inductors and micro-transformers is deeply investigated such as windings, cross-sectional area of core, spacing between windings, and turn ratio. The microwave characteristics of the fabricated micro- inductors and micro-transformers have been measured in the frequency range of 0.5 to 40 GHz for RF applications