Forming low resistivity hillock free conductors in VLSI devices

Particularly for use in MOS (metal-oxide-semiconductor) VLSI (very large scale integrated) circuits, an aluminum conductor coated with a layer of refractory metal or refractory metal silicide has the advantages of being resistant both to electromigration and to hillock growth. By this invention, to reduce the resistivity of this composite conductor and to eliminate hillock formation, the conductor is subjected to an ion implantation step to cause interface mixing between the aluminum and the adjacent refractory metal or refractory metal silicide.