Power and Radio Frequency Inductors Using a Hybrid Ferrite-Flex Foil Technology

Abstract

AbstractWe present a hybrid technology for the realization of three-dimensional miniaturized power inductors and RF inductors on silicon. The power inductors consist of planar Cu coils on polyimide substrates, and mm-size ferrite magnetic cores, obtained by three-dimensional micro-patterning of ferrite wafers using powder blasting. The coils are realized using an in-house developed high-resolution polyimide spinning and Cu electroplating process. Winding widths down to 5 μm have been obtained and total device volumes are ranging between 1.5 and 10 mm3. Inductive and resistive properties are characterized as a function of frequency; inductance values in the 100 μH range have been obtained. We also have realized millimetre-size RF inductors on silicon using the same polyimide mould - Cu electroplating coil technology. Subsequently the coils are assembled with magnetic cover plates of commercially available bulk Ni-Zn ferrites of high resistivity. Using the magnetic flux-amplifying ferrite plates, we obtain a 40 % enhancement of the inductance and a 25 % enhancement of the quality factor (Q=10-20) for frequencies up to 0.2 GHz.