Amorphous Metaluc Alloys: a New Advance in Thin-film Diffusion Barriers for Copper Metallization

To overcome these problems, very effective diffusion barriers need to be developed. These barriers should have a low diffusivity for copper, a high thermal stability, and should lack a driving force for chemical reactions with Cu, silicon or silicides. Unlike aluminum, copper does not form stable intermetallic compounds with the transition metals of the V and Cr groups, and the mutual solid solubilities of these metals with Cu are low, so that these metals would seem th be a logical choice for barrier applications. It has long been known, however, that these arguments are misleading[1]. Previous studies have indeed shown Cu diffuses through grain boundaries and defects in a tantalum layer and inth silicon at a relatively low temperature (450°C) causing a failure of devices[2,3].