State of the art manufacturing of semiconductor devices involves electrodeposition of copper for device wiring and chip stacking. The success of the electroplating process depends on electrolyte additives that affect the local deposition rate to yield void-free superconformal, or bottom–up filling of trenches and vias that comprise 3D interconnects. Quantitative chemical process models have been shown to be effective in describing the filling of high aspect ratio features that range from nanometers to millimeters in scale. Nevertheless, much remains to be known about the molecular nature of the additives and the competitive, co-adsorption dynamics involved in both suppression and acceleration of metal deposition. Accordingly, a variety of surface science tools, such as STM and SEIRAS, are being used to investigate additive function. These studies point to controlling interface hydrophilicity as a key principle in the design and operation of additives used for superconformal film growth.