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Superconformal electrodeposition is explained by the curvature enhanced adsorbate coverage (CEAC) mechanism. A CEAC model is used to quantitatively explain shape evolution during bottom-up “superfill” of trenches and vias. The bottom-up filling dynamic is seen to be a consequence of competitive adsorption between a rate suppressing polyethylene glycol-chloride layer (PEG-Cl) and a depassivating or rate accelerating species comprised of sulfonate-terminated propane thiol/disulfide and chloride (SPS-Cl). The SPS is the stronger surfactant and it adsorbs concurrently with displacement of the more rapidly formed PEG-Cl layer; growth on non-planar geometries thus leads to enrichment of SPS on advancing concave surfaces and dilution on convex sections. Because the metal deposition rate rises monotonically with the local accelerator (SPS-Cl) surface coverage, this yields positive feedback that naturally …