Alternatively, the adhesion/barrier layer 24 may be formed by sputtering a titanium-tungsten-alloy layer with a thickness of between 0.01 and 0.7 ??m, and preferably of between 0.03 and 0.7 ??m, on the passivation layer 14 and on the pad 16, principally made of copper, exposed by the opening 14 a.