(Invited) Superconformal Electrodeposition

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. Two distinct processes associated with the prerefential filling of recessed surface features, namely, curvature enhanced accelerator coverage and critical phenomena related to supressor induced negative differential resistance. Quantitative chemical process models based on the above processes 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. The lecture will detail 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. The talk will conclude with a discussion of the lesson learned and their application to the deposition of other metals.