A method for fabricating a copper pillar. The method includes forming a layer of titanium tungsten (TiW) over a semiconductor wafer, forming a layer of zinc (Zn) over the layer of TiW, and forming a copper pillar over the via. In addition, the method includes performing an anneal to diffuse the layer of Zn into the copper pillar. A semiconductor device that includes a layer of TiW coupled to a via of a semiconductor wafer and a copper pillar coupled to the layer of TiW. The copper pillar has interdiffused Zn within its bottom portion. Another method for fabricating a copper pillar includes forming a layer of TiW over a semiconductor wafer, forming a first patterned photoresist, forming a layer of Zn, and then removing the first patterned photoresist. The method further includes forming a second patterned photoresist and forming a copper pillar.