The all-wet process for TSV-fill utilizing electroless barrier and seed technologies prior to electroplating of Cu is promising methods to realize low-cost and highly reliable Cu-filled TSVs for 3-D integration of Si. Although there have been numerous studies to form electroless barrier layers such as Co- and Ni- alloys, poor adhesion of these barrier layers have been a serious problem. In this study, we studied effect of various additives on the adhesion strength of electroplated CoWB film. It is shown that addition of saccharine, which has both sulfone- and amino- groups, significantly improved adhesion strength.