Surface Micromachined RF Inductors and Transformers for Advanced Telecommunication Applications

In this paper, Surface micromachined RF inductors and 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 integrated circuitry fabrication. In particular, the relationship of performance characteristics and geometry of these 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 type 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 GHz.