Through silicon via filling by copper electroplating in acidic cupric methanesulfonate bath

Copper electrodeposition in acidic cupric methanesulfonate bath with organic additives is discussed in this paper. The influence of poly(ethylene glycol) (PEG) and bis-(3-sodiumsulfopropyl disulfide) (SPS) on copper deposition were studied by means of linear sweep voltammetry, cyclic voltammetry and chronoamperometry. These electrochemical analysises revealed a competition of PEG and SPS on electrode surface site. The swiftness of SPS chemisorption and the subsequent displacement by the passivating film of PEG exerted an extra wave at small overpotential on the negative-going sweep. The following polarization curve indicated the firmness of the passivating film. All these features of additives in acidic cupric methanesulfonate bath suggested a novel method to achieve superconformal or bottom-up filling which was proved by actual TSV plating.