Electroless thin film CoNiFe-B alloys for integrated magnetics on Si

Electroless magnetic thin films have been deposited from borane-based baths suitable for use in integrated magnetics on Si applications. The baths were developed for compatibility with standard photoresist for microfabrication of integrated magnetics on Si. The specific formulations, which differ from those reported previously, yield uniform, high saturation magnetisation (up to 2.15 T) deposits with low coercivity (<2 Oe). The resistivity of the film can be increased to minimise eddy current losses by using higher dimethylamine borane (DMAB) content or the inclusion of a second reducing agent, hypophosphite, to facilitate phosphorus codeposition of up to 7 at.%. The Ni content in the plating bath has been shown to exert significant influence over the composition, deposition rate and coercivity. XRD analysis suggests that the deposits consist of nanocrystalline phase with grains <20 nm. Such small grains are consistent with the observed low coercivity of the deposits.