AC Impedance Investigation of Copper in Acid Solution: II. Effect of Bath Additives on Copper Electrodeposition

Abstract

As demonstrated earlier in Part I of this work [ L. D. Burke and R. Sharna , J. Electrochem. Soc. , 155 , D83 (2008) ], the electrochemistry of copper in an acid solution is complicated by the involvement of an active surface state of the metal, which undergoes an interfacial redox transition within the double-layer region, at ca. vs saturated mercury/mercury(1) sulfate electrode. Commonly used bath additives in this area, e.g., PEG, , SPS, JGB, and thiourea, are assumed to influence the plating reaction by coordinating to the oxidized form of the active state couple. The nature of such interactions was explored, over an extended range of potentials in the plating region, for single additives and a limited range of mixed additives, using ac impedance. The involvement of the active surface state of the metal has received little attention in plating electrochemistry to date; its possible involvement in trench superfilling (or damascene copper plating) is outlined.