MPSA effects on copper electrodeposition: Understanding molecular behavior at the electrochemical interface.

摘要

In this work the structure of the electrochemical metal-liquid interface is determined through use of quantum mechanics, molecular simulation, and experiment. Herein are profiled the molecular dynamics details and results of solid-liquid interfaces at flat non-specific solid surfaces and copper metal electrodes. Ab initio quantum-mechanical calculations are reported and define the interatomic potentials in the simulations. Some of the quantum-mechanical calculations involve small copper clusters interacting with 3-mercaptopropanesulfonic acid (MPSA), sodium, chloride, bisulfate and cuprous ions. In connection with these I develop the electrode charge dynamics (ECD) routine to treat the charge mobility in a metal. ECD bridges the gap between small-scale metal-cluster ab initio calculations and large-scale simulations of metal surfaces of arbitrary geometry.; As water is the most abundant surface species in aqueous systems, water determines much of the interfacial dynamics. In contrast to prior simulation work, simulations in this work show the presence of a dense 2D ice-like rhombus structure of water on the surface that is relatively impervious to perturbation by typical electrode charges. I also find that chloride ions are adsorbed at both positive and negative electrode potentials, in agreement with experimental findings. Including internal modes of vibration in the water model enhances the ion contact adsorption at the solid surface.; In superconformal filling of copper chip interconnects, organic additives are used to bottom-up fill high-aspect ratio trenches or vias. I use molecular dynamics and rotating-disk-electrode experiments to provide insight into the function of MPSA, one such additive. It is concluded that the thiol head group of MPSA inhibits copper deposition by preferentially occupying the active surface sites. The sulfonate head group participates in binding the copper ions and facilitating their transfer to the surface. Chloride ions reduce the work function of the copper electrode, reduce the binding energy of MPSA to the copper surface, and attenuate the binding of copper ions to the sulfonate head group of MPSA.