Ni-Zn Ferrite Film Coated on-Chip RF Inductor Fabricated by A Novel Powder-Mixed-Photoresist Coating Technique

This paper reports fabrication and characterization of on-chip RF inductors with integrated Ni-Zn ferrite films using a novel powder-mixed-photoresist coating technique. Well crystallized Ni0.3Zn0.6Cu0.1Fe₂O₄ powders are mixed into photoresist and then coated on top of RF inductor spirals for performance improvement. This new low-temperature fabrication method is developed to eliminate any damage introduced by conventional high temperature process (>600degC) used in fabricating ferrite-integrated RF IC inductors. Measurement results show that, compared with air-cored inductor, the inductance (L) of ferrite film inductors increases by 14-27% across 0.1-4GHz range. This work demonstrates a promising way to fabricate ferrite-integrated high-performance on-chip RF inductors in CMOS technology for RF SoC designs.