| abstract |
Solder bump structures, which comprise a solder bump on a UBM structure, are provided for operation at temperatures of 250° C. and above. According to a first embodiment, the UBM structure comprises layers of Ni—P, Pd—P, and gold, wherein the Ni—P and Pd—P layers act as barrier and/or solderable/bondable layers. The gold layer acts as a protective layer. According to second embodiment, the UBM structure comprises layers of Ni—P and gold, wherein the Ni—P layer acts as a diffusion barrier as well as a solderable/bondable layer, and the gold acts as a protective layer. According to a third embodiment, the UBM structure comprises: (i) a thin layer of metal, such as titanium or aluminum or Ti/W alloy; (ii) a metal, such as NiV, W, Ti, Pt, TiW alloy or Ti/W/N alloy; and (iii) a metal alloy such as Pd—P, Ni—P, NiV, or TiW, followed by a layer of gold. Alternatively, a gold, silver, or palladium bump may be used instead of a solder bump in the UBM structure. |