The effect of annealing on the properties of silicidized molybdenum thin films

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Abstract
The effect of isothermal and isochronal annealing on the structural and electrical properties of silicidized Mo thin films is reported. The silicidation of Mo with SiH4 resulted in Mo films with increasing hexagonal MoSi2 content as the reaction time increased. Post-reaction annealing was performed in various ambients (hydrogen, nitrogen, and vacuum) at temperatures from 800 to 1000 °C for times up to 1 h. Annealing in H2 at 1000 °C for only 5 min results in the virtual disappearance of the original components and the formation of intermediate silicide phases (Mo5Si3 and Mo3Si) and the tetragonal MoSi2 phase. This structural transformation leads to a significant increase in resistivity. The reaction kinetics are considerably slower in the case of N2 ambient, where even after a 60-min anneal at 1000 °C a substantial percentage of Mo remains. This slower rate of phase change is reflected in a more gradual increase in the sheet resistance. The characteristics of vacuum-annealed films followed the N2 case for short-term anneals (t≲10 min), but resembled the H2 case longer-term anneals (t≳15 min). The dependence of reaction mechanisms on various ambients is discussed.

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