A method of forming electrical connections to a semiconductor wafer. A semiconductor wafer comprising an insulation layer is provided. The insulation layer has a surface. A patterned mask layer is formed over the surface of the insulation layer. The patterned mask layer exposes portions of the surface of the insulation layer through a plurality of holes. The portions of the plurality of holes are filled with a metal material comprising copper to form elongated columns of the metal material. The elongated columns of the metal material have a sidewall surface. The patterned mask layer is removed to expose the sidewall surface of the elongated columns of the metal material. A protection layer is formed on the exposed sidewall surface of the elongated columns of the metal material.