A metal structure for a contact pad of a wafer or substrate (101), which
have copper interconnecting traces (102) surrounded by a barrier metal
layer (103). The wafer or substrate is protected by an insulating
overcoat (104). In the structure, the barrier metal layer is selectively
exposed by a window (110) in the insulating overcoat. A layer of copper
(105), adherent to the barrier metal, conformally covers the exposed
barrier metal. Preferably, the copper layer is deposited by sputtering
using a shadow mask. A layer of nickel (106) is adherent to the copper
layer and a layer of noble metal (106) is adherent to the nickel layer.
The noble metal may be palladium, or gold, or a palladium layer with an
outermost gold layer. Preferably, the nickel and noble metal layers are
deposited by electroless plating.