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 (on-chip wiring¹) to micrometers (through-silicon-vias²) to millimeters (printed circuit boards) 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 scanning tunneling microscopy (STM) and surface-enhanced infrared absorption spectroscopy (SEIRAS) are being used to investigate additive function. This lecture will focus on recent SERIAS experiments that reveal the important role of adsorbate water interactions, i.e. hydrophilicity, in the design and operation of additives used for superconformal film growth.