Barrier metal

From Wikipedia, the free encyclopedia

A barrier metal is a material used in integrated circuits to chemically isolate semiconductors from soft metal interconnects, while maintaining an electrical connection between them. For instance, a layer of barrier metal must surround every copper interconnection in modern copper-based chips, to prevent diffusion of copper into surrounding materials.

As the name implies, a barrier metal must have high electrical conductivity in order to maintain a good electronic contact, while maintaining a low enough copper diffusivity to chemically isolate the copper conductor from the silicon below. The thickness of the film is also quite important; with too thin a layer, the copper contacts poison the very devices that they supply with energy and information; with too thick a layer, the stack of two barrier metal films and a copper conductor have a greater total resistance than a traditional aluminum interconnection would have, eliminating the benefit of the new technology.

Some materials that have been used as barrier metals include cobalt, ruthenium, tantalum, tantalum nitride, indium oxide, and titanium nitride (the last three being conductive ceramics, but "metal"s in this context).

See also diffusion barrier.