| abstract |
A method is provided for providing a conductive pad for electrical connection with improved diffusion barrier and adhesion properties. In this method, a copper pad face which is first cleaned in an acidic solution is provided. A protective layer of phosphorus or boron-containing metal alloy is then deposited on the copper pad face, and an adhesive layer of noble metal is deposited on top of the protective layer. The protective layer may be a single layer, and Ni-P, Co-P, Co-WP, Co-Sn-P, Ni-WP, Co-B, Ni-B, Co-Sn-B, Co-WB, and Ni It may be two or more layers closely bonded to each other formed of a phosphorus or boron-containing rapid alloy such as -WB. Suitable thicknesses for the protective layer are about 1000 kPa to 10000 kPa, preferably about 3000 kPa to 7000 kPa. The adhesive layer may be formed of precious metals such as Au, Pt, Pd, and Ag, having a thickness of about 500 kPa to about 4000 kPa and preferably of about 1000 kPa to 2000 kPa. Alternatively, a nucleation layer of Pd is deposited between the copper conductive pad surface and the protective layer prior to electroless deposition of the protective layer. Alternatively, an additional precious metal layer is deposited on top of the adhesive layer by an electroless Au deposition process to increase the thickness of the final precious metal layer to about 2000 kPa to 12000 kPa, preferably about 4000 kPa to 6000 kPa. The present invention also discloses a conductive pad comprising a copper pad face, a protective layer made of a phosphorus or boron-containing metal alloy, and an adhesive layer of a noble metal deposited on top of the protective layer, and for forming an electrical connection thereon. Furthermore, the present invention also relates to an electrical structure comprising an electrical connection integrally formed on top of the adhesive layer, ie, a conductive pad having wire bonding or solder bumps. |