In this experiment, metal (Mo/Cu) seed layers with an aspect ratio of 10:1 were deposited by a conventional sputtering method and then copper filling by electroplating was followed in order to fabricate through silicon vias with a high aspect ratio. With increasing the aspect ratio, it is critical to carefully control the reduction of via's hole size before filling the bottom seed layer. By changing sputtering time, pressure, and power, changes in the thickness of the metal seed layers were investigated. It was found that optimizing the sputtering conditions improved the quality of the seed layer and retarded the speed of the hole size reduction. As a result, a metal seed layer with a via's opening percentage of about 62% and a bottom seed layer thickness of 46.7nm was fabricated by conventional sputtering. Using this seed layer, Cu filling was successfully carried out by electroplating. (C) 2013 Elsevier Ltd. All rights reserved.