Selective tungsten silicide formation by ion-beam mixing and rapid thermal annealing

Smooth layers of tungsten silicide have been formed on silicon substrates by deposition of a tungsten film, As+ ion implantation through the film to produce ion-beam mixing, and rapid thermal annealing. This process has been used to form tungsten silicide selectively in patterned openings etched in the SiO2 film on oxidized Si wafers, without lateral silicide growth. Rapid thermal annealing results in the activation of the As implanted in the Si substrate, without significant redistribution, to form shallow n+-p junctions with good electrical properties.