Effect of Saccharin on Crystallization Behavior of Electroless Cobalt Plating

In the process of electroless cobalt plating, the saccharin additive can significantly change the surface morphology, texture orientation, and conductivity of the cobalt coating layer. When the amount of saccharin was 3 mg·L–1, the cobalt coating transformed from disordered large grains to a honeycomb structure, with a preferred orientation of (002) facet on hexagonal close-packed (HCP) cobalt crystals. The resistivity of the cobalt film decreased to 14.4 μΩ·cm, and further decreased to 10.7 μΩ·cm after the annealing treatment. When the concentration of saccharin was increased, the grain size was gradually refined and a “stone forest” structure was observed, with the preferred orientation remaining unchanged. The addition of saccharin also slightly improves the purity of cobalt coating to a certain extent. Through the study of the crystallization behavior of cobalt electroless plating, saccharin molecules can adsorb to specific c-sites on the cobalt dense crystal plane, inhibiting the growth of abc stacking arrangement and inducing the crystal growth in ab stacking mode, thereby achieving optimal growth of HCP (002) texture.