FERRITE MAGNETIC-ANISOTROPY FIELD EFFECTS ON INDUCTANCE AND QUALITY FACTOR OF PLANAR GHZ INDUCTORS

Planar gigahertz (GHz) inductors were fabricated based on high crystalline-anisotropy Zn0.13Co0.04Ni0.63Fe2.2O4 (Zn-Co-Ni ferrite) and Ba3Co2Fe24O41 (Co2Z hexaferrite) and characterized for inductance (L) and quality (Q) factor. The planar ferrite inductors show an L of 4.5 nH (Zn-Co-Ni), 5.6 nH (Zn-Co-Ni + low Hk and fFMR Co2Z:), and 4.8 nH (Zn-Co-Ni + high Hk and fFMR Co2Z:) at 2GHz. The corresponding L-densities are 18.0, 22.4, and 19.2 nH/mm2, which are greater than 16.8 nH/mm2 of the air-core inductor. With respect to the Q factor, the air-core and ferrite inductors exhibit Q factors of 6.7 (air-core), 4.8 (Zn-Co-Ni), 2.8 (Zn-Co-Ni + low Hk Co2Z), and 4.0 (Zn-Co-Ni + high Hk Co2Z) at 2GHz. The tan δμ of the ferrites caused a reduction in the Q factor. Nevertheless, the high Hk and fFMR Co2Z ferrite inductor demonstrates a higher Q factor than that of the low Hk and fFMR Co2Z inductor. It is, therefore, suggested that high resistivity, anisotropy, magnetization ferrite can produce large L density and Q factor GHz inductors.