In order to investigate the copper gap-filling during micro electroplating process with additive (N’,N’-diethylthiourea), the electrochemical behavior of different electrolyte (without additive, with thiourea or N’,N’-diethylthiourea additive) were studied by LSV, CV and SEM, and the electrode kinetics parameters was studied by the Tafei equation. The results show that when N’,N’-diethylthiourea was used during the micro electroplating copper process, activation polarization was generated; metal ion discharge rate was lowered, the overgrowth of fast plating area such as micro-trench edges was restrained; at the same time, activation polarization was increased, thus the crystal nucleus molding speed on the electrode was accelerated; the crystal growth speed was decreased, the plating became flat, and the leveling ability was increased about 50% than that without additive. Furthermore, some micro trenches in the silicon wafer, and the width of 10 μm and aspect ratio of 4∶1, were filled by the micro electroplating process with the additive N’,N’-diethylthiourea, however, the electroplating layer had no voids or seams.

Key words: micro-electrodeposition process, N’,N’-diethylthiourea, activation polarization, electrochemical behavior