Via-filling by Copper Electroplating using Stepwise Current Control

抄録

Complete via-filling by conventional direct electroplating becomes difficult with increasing hole diameter and aspect ratio. To achieve complete filling, various stepwise current controls were evaluated using the copper electroplating bath in the presence of additives. We found that there were two important factors necessary to produce complete filling of the wide opened via holes with a high aspect ratio. One factor was the suppression of the preferential deposition around the open area at the top of the holes and the other one was to effectively carry the copper ions into the bottom of the holes. Complete filling was achieved by applying the high current density for several seconds at the onset. Next a low current was applied followed by a stepwise increase back to the original level. This method provided complete filling of the via-holes. In addition, the influence of additives on the copper deposition and the effectiveness of stepwise current control were evaluated by electrochemical measurements.