Influence of Molecular Weight of Polyethylene Glycol on Microvia Filling by Copper Electroplating

The influence of the molecular weight (Mw) of polyethylene glycol (PEG) on the microvia filling by copper electroplating was demonstrated and examined by cross-sectional images using an optical microscope. The electrochemical behavior of PEG of different molecule weights in the copper electroplating was characterized by galvanostatic measurement. In the presence of excess , the surface coverage of PEG of various Mw adsorbed on the copper surface was characterized by observing the size and distribution of CuCl precipitates using a scanning electron microscope. As PEG Mw was increased, the best filling performance of plating formula was obtained when the PEG Mw ranged from . Only large PEG amounts whose Mw exceeds can effectively polarize the cathode, in turn inducing the catalytic effect of bis(3-sulfopropyl) disulfide on copper deposition, resulting in a synergistic interaction between the suppressor and accelerator on the microvia filling.