| abstract |
A copper pad surface 14 of an IC chip is first prepared, e.g. cleaned by an acid solution, a protection layer 16 of a phosphorus or boron-containing metal alloy is then deposited on the copper pad surface, and then an adhesion layer 18 of a noble metal is deposited on top of the protection layer. The protection layer 16 may be a single layer, or two or more layers intimately joined together formed of a phosphorus or boron-containing metal alloy such as Ni-P, Co-P, Co- W-P, Co-Sn-P, Ni-W-P, Co-B, Ni-B, Co-Sn-B, Co-W-B and Ni-W-B. A suitable thickness for the protection layer is between about 1,000 Ñ and about 10,000 Ñ, and preferably between about 3,000 Ñ and about 7,000 Ñ. The adhesion layer 18 can be formed of a noble metal such as Au, Pt, Pd and Ag to a thickness between about 500 Ñ and about 4,000 Ñ, and preferably between about 1,000 Ñ and about 2,000 Ñ. A nucleation layer of Pd may be deposited between the copper conductive pad surface 14 and the protection layer 16 prior to the electroless deposition of the protection layer. An additional noble metal layer may be deposited on top of the adhesion layer 18 by an electroless Au deposition process to increase the thickness of the final noble metal layer to about 2,000 Ñ 12,000 Ñ, and preferably between about 4,000 Ñ and about 6,000 Ñ. The pad is suitable for a wireband or solder bump connection |