The Adsorption Structure of Polyethylene Imine on Copper Surfaces for Electrodeposition

Challenging copper electrodeposition processes for semiconductor applications require in depth understanding of the mode of operation of the organic plating additives. For this purpose, polyethylene imine (PEI) as a prototypical leveler additive is investigated by simulations, including adsorption at the interface between copper as well as chloride-covered copper and water. Conformational analysis of the dihedral angles along the polymer chain allows insights into structural changes upon adsorption of the molecules in comparison with the bulk electrolyte. Distribution of the respective atoms of the polymeric molecules sorted by elements along the surface normal further provides information about the orientation. Both conformational changes and orientation depend on the degree of protonation, i.e., the pH value or acid concentration of the electrolyte. The results are compared with electrochemical and spectroelectrochemical data to confirm the accuracy of the simulations and to allow correlation to the performance in the actual deposition process.