Developing plating baths for the production of cobalt-molybdenum films

A set of plating baths for obtaining soft-magnetic cobalt-molybdenum (Co-Mo) films with 5-11 wt.% Mo was tested. Free Co2+ concentration in solution seemed to determine the quality of the electrodeposited films. Coherent, compact Co-Mo films were obtained under a current efficiency up to ∼70% in baths with ∼40% free Co2+. By contrast, low concentrations of free Co2+ reduced current efficiency in the preparation of the deposits, while excess concentrations of free Co2+ resulted in cracked films. Backscattered electron images demonstrated that good-quality Co-Mo films grew layer by layer. Such growth was linked to both structural and magnetic properties. The coatings presented a crystallographic direction parallel to the substrate. Moreover, a high uniaxial anisotropy constant and an angle of the resulting anisotropy of 62° were determined by magnetic measurements. The selectivity of deposition was verified on photolithographed silicon-based substrates.