Research On The Bath Of Super-filling Electroless Copper

â… Determination of chloric ions in acidic copper platingWith a development of electronic products toward more light,thin,and fast transmission, void-free and seamless electroplated copper filling microvia-hole is challenging for printed circuit boards(PCBs) fabrication.Additives are very essentional for plating copper bath to fill micro-holes with bottom-up filling.Turbidimetry was used to determinate the concentration of Cl~- after via filling plating.Microamounts of chloride ion in acidic copper electroplating solution was determined directly by the silver chloride turbidimetric method in the presence of the organic additive(SPS and PEG)with glycol as solubilizing agent and silver nitrate as precipitating agent.Measurement method of Cl~- in copper electroplating bath whiout organic additives or containing SPS and PEG was studied.The effects of measurement time,Cl~- concentration on the absorbance were investigated.Absorbance of the sample containing highter concentration changes largely with the time.And so,it was not proper to deterninate the concentration of Cl~- highter than 10 mg/L.To enhance the accuracy,absorbance of the sample were been determined after the sample was prepaired for 21,23,25 min.Concentration of Cl~- after via filling plating was determined for two times.The filling situation of the micro-via and its relation with the concentration were also analysised.Effect of different Mw of PEG on cathodic polarization behavior of electrolyt was studied and the inhibitting effect of PEG increased with the increasing Mw.â…¡Research on the bath of super-filling electroless copperBecause of its low resistivity and high reliability against electromigration,bottom-up copper filling is widely used in Ultra Large Scale Integrated Circuits(ULSIs).However,with the rapid shrinkage in interconnection dimensions,it is difficult to filling of trenches and holes by electroplating,and so,electroless bottom-up copper filling is studied.Deposition rates of electroless copper bath with concertration and molecular weight(Mw) of polyethylene glycol(PEG) were measured.The deposition rates decreased with the increases of PEG.concentration and Mw.The result of liner sweep voltammetry measurement showed that PEG inhibited the electroless copper deposition and the inhibiting effect increase with an increase of PEG Mw.Bottom-up filling of trenches was achieved by assition of PEG-6000) or PEG-8000 which has concentration degrace from the top to the bottom.The hottom-up filling is not only indenpent upon the concentration and Mw of PEG,but also upon the sizes of trenches.A new system of super-filling electroless copper plating was investigated.Though bottom-up filling of the trenches was not achieved,signs of bottom-up filling were observed at 0.5mg/LSPS.The effects SPS,SPS-2,2'-dipyridine,SPS-PEG-4000 on the copper electroless deposition rate were investigated.When it was added alone,SPS acted as an accelerator,but when it was added together with 2,2'-dipyridine or PEG-4000,it acted an inhibitor.The influnces of SPS and PEG-6000 on surface topography and crystallinity of copper deposited film were also studied.In addition,the effect of PEG-6000 on the deposition rate of the bath containing TEA was investigated.PEG-6000 inhibited the deposition rate,but the inhibitiion effect became very weak when the concentration was more than 1mg/L.