Role of additives for copper damascene electrodeposition experimental study on inhibition and acceleration effects

The role of copper Damascene additives is discussed based on electrodeposit morphology on a through-mask cathode, field emission-Auger (FE-Auger), quartz crystal microbalance (QCM), and electrochemical measurements. Adsorbed particles, several tens of nanometers in diameter were observed on copper-electrodeposited surfaces by field emission-scanning electron microscopy (FE-SEM). These particles show a stronger oxygen intensity peak by FE-Auger spectrum than bare electrodeposited surfaces. The QCM frequency deviation did not increase with time in the CuSO4 and H2SO4 bath without polyethylene glycol (PEG) and chloride ion (Cl-) additives. When the substrates were immersed in the bath with these additives, the deviation markedly increased with time. Numerous PEG molecules were observed by FE-SEM immersed after 1000 s. The current density remained constant at a low value for the bath with PEG and Cl- additives. The current density started to increase markedly with time just after adding 1 ppm of bis(3-sulfopropyl) disulfide (SPS). Numerous PEG molecules were present on the electrodeposits before adding SPS. No PEG molecules, however, remained on the surface once SPS was added to the bath. The current density increased with narrower opening widths of the through-mask cathode. Despite this increase, the deposit cross sections on narrower opening widths of 2 and 10 mum were flat and no curvatures were found. Hence, the deposit curvature is not the origin of the acceleration effect. (C) 2004 The Electrochemical Society.