A CMOS-MEMS magnetic thin-film inductor for radio frequency and intermediate frequency filter circuits

RF/IF filter circuits rely on high quality passive devices such as inductors and capacitors. We propose a novel process to integrate magnetic thin-film inductors using CMOS-MEMS and magnetic film processing technologies. When used in IF filters, great power saving and a high degree of integration can be achieved compared with conventional SAW or Gm-C filters at IF. Magnetic thin-film inductors are much more compact than conventional inductors. Since the electromagnetic field is well confined in the magnetic film, cross-coupling is greatly reduced. With thin film (∼1 μm) and thus less eddy current loss it is capable of frequency up to GHz. Prototype CMOS-MEMS inductors with 0.2 μm permalloy (NiFe) thin-film were fabricated and tested. A 10X increase in both inductance and Q was observed, and the peak Q was sustained up to 200 MHz.