Influence of Additives on Copper Electrodeposition on Physical Vapor Deposited (PVD) Copper Substrates

Cross-sectional scanning electron microscopy (SEM), secondary-ion mass spectrometry (SIMS), atomic force microscopy (AFM), and electrochemical measurements are utilized to examine the effect of additives on the morphology and nature of Cu electrodeposited on Cu substrates. The additives used here include 4,5-dithiaoctane-1,8-disulfonic acid (SPS), polyethylene glycol (PEG), and SIMS results show that SPS is always included into Cu electrodeposits, while PEG is never included. is included in deposits only when SPS is present. SEM measurements show that one consequence of this inclusion is the formation of an internal grain structure, which is not evident in the surface morphology measured by AFM alone. The growth of deposits is discussed in terms of cross-sectional and scaling analysis of AFM images.