Pores with diameters of about 5 mu m were formed in n-type Si(100) wafers by wet etching using aggregated Au particles, each about 1 mu m, as catalysts. The pores were as deep as 100 mu m after etching for 5 h. In the pores of the Si wafers, which were almost perpendicular to the Si surface, Cu was electrochemically deposited from an aqueous solution of CuSO4 using Au particles remaining at the bottom of the pores as seeds for deposition. When a potential of about - 0.275 V vs Ag/AgCl was applied to the Si wafer, Cu deposition started from the bottom of each pore and continued to fill the whole pore with a depth of about 70 mu m in 16 h. The selective Cu deposition in the pores is due to an electrocatalytic effect of Au/Cu for Cu plating. In these processes, therefore, Au particles acted as catalysts for pore formation and also as seeds for Cu electrodeposition, making it possible to fabricate connections through wafers by a simple method. However, it was difficult to increase the deposition rate by applying potentials more cathodic than - 0.40 V vs Ag/AgCl because Cu was deposited on the Si surface at these potentials. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3237139] All rights reserved.