Investigation of carrying agents on microstructure of electroplated Cu films

Abstract

Adding high molecular-weight polyethylene glycol (PEG) as a carrying agent benefits Cu electroplating from the viewpoint of an increase in both filling capability and films' conductivity, when plated in a lower current-density region. On electroplating in a higher current-density region, a gradually decreasing grain size from the top to bottom of Cu films occurs in the electrolyte without PEG or with PEG200. In comparison, sharp grains are formed for the mentioned multi-domain crystallization for those films deposited by the electrolyte containing PEG2000 or PEG6000 due to its lower surface tension which facilitates grain growth along the higher electric field. The used concentration of PEG was flexible due to the fact that the surface morphology, resistivity and deposition rate of deposited films remained almost unchanged over a wide PEG concentration range.