Alternatively, the seed layer 252 b, such as copper, can be sputtered, electroless plated or electroplated on the adhesion/barrier layer 252 a formed by first sputtering a chromium layer and then sputtering a chromium-copper-alloy layer on the chromium layer, and then the single metal layer 282 comprising copper is electroplated or electroless plated on the seed layer 252 b.