CMOS-compatible integration of thin ferromagnetic films

We report on a new process technology for integration of ferromagnetic layers up to about 500 nm thick in a commercial 1.5 mym double-metal CMOS process allowing enhanced process temperatures up to 400 degree C. The nickel-iron structure is placed between two metallization levels, separated by SiO2, interlayer dielectric films. Pattern definition is done with an aluminium mask, which can withstand the high temperature stress during nickel-iron deposition. We have fabricated nickel-iron structures with widths down to 4 mym. The three-metal-level process sequence presented here enables three-dimensional integrated coils with a ferromagnetic core to be fabricated.