Superfilling When Adsorbed Accelerators Are Mobile

Bottom-up superconformal feature filling during electrodeposition, called "superfilling," that is used for industrial processing of damascene copper interconnects has also been demonstrated during electrodeposition of silver and gold. The curvature enhanced accelerator coverage (CEAC) mechanism has been proposed to underlie all three processes and has been used to quantitatively predict observed filling of patterned features. The key feature of the CEAC mechanism is redistribution of adsorbed additives through changes of local surface area as dictated by mass conservation and the relative strengths of adsorption. Previous studies of CEAC-mediated superfilling have neglected adsorbate diffusion along the surface that might arise during deposition due to the CEAC-induced gradients in surface coverage. This paper extends the CEAC model to include such diffusion, applying the resulting formulation to understand differences in the geometries of experimental superfilling systems.