Investigation of organics adsorption and inclusion at the growing interfaces during the Damascene process

Copper electroplating is now established as the mainstream process for filling vias and trenches in advanced interconnections schemes. A specific chemistry has been developed to achieve a complete and void free filling of the structures through “bottom-up” growth, also called “superfilling”. The acidic copper electrolyte generally contains three different organic additives (suppressor, accelerator and leveler) and chloride ions [T.P. Moffat, D. Wheeler, M. Edelstein, D. Josell, IBM J. Res. Dev. 49 (2005) 19], which play a key role for the additives adsorption and activation at the wafer surface [W.P. Dow, H.S. Huang, J. Electrochem. Soc. 152 (2005) C67]. However this chemistry leads to a rise in contamination levels incorporated within the copper films, specifically in carbon, sulfur and chlorine [A. Meunier, C. Bondoux, L. Omnès, F. Jomard, A. Etcheberry, Mater. Res. Soc. Symp. Proc. AMC (2006) 137], due to incorporation and/or degradation mechanisms. These inclusions have effects upon the film microstructure (grain size) with some time an increase of the copper film resistivity [A. Preusse, M. Nopper, AMD, Dresden, Germany, Semiconductor Fabtech 26th Edition, Wafer Processing, p. 123].Here we present a correlation studies with electrochemical quartz crystal microbalance (EQCM) measurements to provide a further insight of the adsorption of these surfactants prior and during the plating process. A study by secondary ion mass spectrometry (SIMS) which aims at better understanding the inclusion of organic by-products in the copper matrix during the plating process will also be presented. A particular emphasis will be put on the mechanisms of segregation of these species at the growing interfaces with respect to the deposition parameters.