Superparamagnetic, nanocrystalline cobalt ferrite thin films as magnetic core of integrated RF inductors

Using microwave-assisted synthesis in the solution medium, superparamagnetic, nanocrystalline cobalt ferrite thin films have been deposited on integrated inductors to increase inductance density. Cobalt ferrite thin films (CFTF), ∼820 nm thick, can be deposited in 10 min at ∼190°C, making the process CMOS-compatible. The as-prepared CFTF has a saturation magnetization (MS) of 238 emu/cc and coercivity (Hc) of 32 Oe at room temperature for a particle size of ∼ 8 nm. The inductance of an on-chip inductor increased from 7.1 nH to 9.9 nH at 5 GHz when the CFTF was deposited on it, an enhancement of nearly 40%.