Electroless deposition of NiMoP films using alkali-free chemicals for capping layers of copper interconnections

NiMoP films were electrolessly deposited on copper substrates in a bath containing alkali-free chemicals. The film characteristics such as composition, thickness (or deposition rate), and microstructure were investigated by varying the concentration of the electrolyte. The film thickness increased with nickel ion concentration and decreased with increasing concentrations of either molybdate or hypophosphite ions. The nickel, molybdenum, and phosphorous content of the film increased as the concentrations of their corresponding precursors increased in the bath. Microstructural analysis showed that amorphous films formed when the combined content of molybdenum and phosphorous in the film was sufficiently high. Higher combined contents of molybdenum and phosphorous also improved the corrosion resistance of the film.