Defforge et al. Nanoscale Research Letters 2012, 7:375 http://www.nanoscalereslett.com/content/7/1/375 Page 4 of 7 Figure 3 Selective TSV formation by local seed layer deposition. (a) Electrochemical etching of silicon leading to through-silicon macropore array formation. (b) Local deposition of the seed layer on one side of the sample. (c) The macropores sealed by the seed layer are selectively filled with copper. Figure 4 Selective TSV formation by local opening of almost through-silicon macropores. (a) Electrochemical etching of silicon leading to high aspect ratio structures. (b) Selective opening of the backside oxide mask followed by alkaline etching. This leads to local formation of through-silicon macropores. (c) Seed layer deposition on the backside. (d) Copper electrochemical deposition into the through-silicon macropores.