High Q Ni-Zn-Cu Ferrite Inductor for On-Chip Power Module

Abstract

We fabricated 3 times 3 array of 1 mum thick Ni-Zn-Cu ferrite and air-core planar inductors (5 times 5 mm2 in size; 2.5, 3.5, and 4.5 turns of Cu coil) on 4 inch bare Si wafer and 300 nm thick SiO2/Si wafer, respectively. The ferrite inductor showed higher Q than that of air-core inductor in the range of 7 to 100 MHz. The Q (= 19.5) of 4.5 turn ferrite inductor is 3.3 times higher than that (= 5.9) of 4.5 turn air-core inductor at 10 MHz, and inductance (L) increased by 10%. The Q-factors were found to be about 50 at 2.3 MHz and 20 at 10 MHz, respectively, for the ferrite inductor.