An alkaline, tartrate-complexed copper electrolyte containing additives that provide bottom-up fill is described. Bottom-up fill is achieved using a mixture of two additives: bis-(3-sulfopropyl) disulfide (SPS) and polyethyleneimine (PEI). Chronopotentiometric studies indicate that, unlike in conventional acidic electrolytes, SPS acts as a 'suppressor' and PEI acts as an 'anti-suppressor' in the alkaline medium. Partial-fill experiments on patterned structures confirm a SPS-PEI interaction leading to bottom-up fill from the tartrate-complexed copper electrolyte. (C) 2013 The Electrochemical Society. All rights reserved.