Oxygen behavior during titanium silicide formation by rapid thermal annealing

Abstract

Sputtered titanium thin films on 〈100〉 Si wafers were exposed to rapid thermal annealing (RTA) in argon at temperatures of 600–900 °C. Auger depth profiling shows that when exposed to air the Ti films takes in 3×1016 oxygen atoms cm−2 independently of Ti thickness. During RTA the oxygen tends to redistribute uniformly and a snowplow effect, due to the O solubility difference between Ti and TiSi2, confines it to the unreacted titanium layer. Early on, silicon is observed at the Ti surface and a second silicide layer starts growing. All of the oxygen is finally fixed in the C54 TiSi2 where the two silicide fronts meet (at around 50 nm from the surface). This reproducible effect is associated with RTA and is not observed in classical furnace annealing.