Feature-scale simulation of resist-patterned electrodeposition

A numerical simulation of resist-patterned or “through-mask” electroplating has been performed to investigate shape evolution at the scale of small lithographic features. Shape evolution and step coverage have a significant influence on the shapes of such microelectronic structures as conductor lines, vias, and magnetic pole pieces. The simulation and associated analysis are based on a model for the rate distribution of the electrodeposition reaction that includes the depletion of the depositing metal ions and the inhibiting action of leveling agents. A stagnant boundary layer is assumed to be present, and the diffusion theory of leveling with a one-parameter description of kinetic inhibition is employed. The results show that when the geometry of a feature cavity makes possible the occurrence of concentration-field effects (such as radial diffusion), an uneven metal-ion flux should cause nonuniform growth at high fractions of the limiting current, and leveling agents should exert an opposing effect, even causing a strong reverse nonuniformity in some cases.