The most widely used materials in metalization are aluminium, tungsten and recently also copper. Deposition of metals is performed by physical vapor deposition. Originally, evaporation methods were used, but they have been displaced in modern technologies. This resulted from problems in alloy formation and an extremely low step coverage, that prevent evaporation methods to fabricate good contacts in submicron lines. It is, however, still used in technologies using III-V semiconductors, where the interconnect needs are relaxed.
Sputtering is the primary metalization technique for modern silicon technologies. It involves the bombardment of the material to deposit with high energy ions which dislodge their molecules to reattache reattache on the wafer surface. Besides presenting better step coverage, sputtering works equally well when material compounds are used. This is important as alloys (e.g. TiN, TiW, ...) are normally used to enhance the reliability of contacts and vias.
In very high performance applications buried stacked contacts and vias are utilized to increase the wiring density. This demands a step coverage that for deep-submicron technologies it is not attainable with sputtering. In these cases metal CVD, a topic still under research, seems to be promising.