Desorption of Polyethylene Glycol During Copper Electrodeposition: Effects of Potential and SPS

Polyethylene glycol (PEG) is an important additive to electroplating baths used in the damascene process for the fabrication of copper interconnects on semiconductor wafers. When used in combination with chloride ions, PEG promotes filling of submicron cavities by suppressing deposition on surfaces outside the cavities (1-3). Suppression is considered to be due to an adsorbed polymer layer. Deposition at the cavity bottom is activated by a third additive, sulfopropyl sulfonate (SPS). The location of activation has been explained on the basis of curvature effects on adsorption (2,3), but the chemical mechanism of activation is yet unclear. It is possible that activation is be controlled by the effect of SPS on the desorption kinetics of the polymer. The present investigation undertook to characterize the desorption o