Electroplated micro-inductors and micro-transformers for wireless applications

In this paper, solenoid-type RF micro-inductors and micro-transformers have been newly designed, fabricated, and characterized by using electroplating techniques, multi-layer thick photoresist, and low temperature processes which are compatible with semiconductor circuitry fabrication. In. particular, relationship of Performance characteristics and geometry of per try 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. The micro-inductors have inductance between 1 nH and 7 nH, maximum quality factor of 31 at 6 GHz, an inductance of 2.7 nH, and a self resonant frequency of 15.8 GHz. Two types of solenoid micro-transformers with turn ratios of 1:1 and n:1 have been fabricated and characterized. They have the minimum insertion loss of about 0.6 dB and the wide. bandwidth of a few GBz.