Influence of polymer additive molecular weight on surface and microstructural characteristics of electrodeposited copper

Electrodeposition of copper was done with different molecular weight (MW) polyethylene glycol (PEG) as an additive in the plating bath. The adsorbed layer formed of PEG and chloride ion (Cl − ) in the presence of copper ions has a definite role in controlling the deposition mechanism and the coating characteristics. The adsorption behaviour and suppressor nature of PEG with different MW (200–20000) on the physicochemical and the surface morphological features of the copper deposit were characterized. The results reveal that depending on the adsorption capacity of the intermediate complex, the deposit properties show gradation. There is a range of morphology with particular grain structure for different MW PEG addition. Grain size and the roughness decreased with increase in PEG MW. The concentration of Cl − ion in the plating bath is also significant in determining the deposit mechanism of the bath as revealed from the shift in cathodic potential. The adsorbing power of the complex depends not only on PEG MW but also on Cl − ion concentration. XRD analysis of the copper deposit obtained with low MW PEG showed (220) as the major plane and with high MW PEG the prominent orientation was (111) and (200).