INTERNAL-STRESS IN FERRITE PLATED THIN-FILMS

Internal stress in ferrite plated films of Fe3O4 and Ni-ferrite was ev aluated, and its dependence on the plating conditions was investigated . The internal stress was estimated to be 0.5 similar to 1.7x10(9) dyn /cm(2) in tension. For Ni-ferrite films, the stress increased with inc reasing the atomic ratio of Ni/Fe in reaction solution. The plated fil ms were composed of columnar-shaped grains of 0.2 similar to 0.3 mu m in size near the top surface as observed by SEM. Crystallinity of the films degraded with increasing Ni/Fe, and peaks of spinel structure we re not observed by X-ray diffraction diagram for Ni/Fe=0.83. These res ults suggest that excess Ni ions in the reaction solution increase imp urities in the films, which may increase the tensile internal stress. We found that the internal stress can be reduced by adjusting layout o f sprays (i.e. changing the height of the nozzles from the table) in t he spin-spray ferrite plating.