FORMATION OF C54 TiSi2 ON Si(100) USING Ti/Mo AND Mo/Ti BILAYERS

Abstract

The effect of Mo on the formation of C54 TiSi 2 on Si (100) substrates is studied using cross-section transmission electron microscopy. For a Ti/Mo bilayer on Si, the interfacial Mo film reacts with Ti and Si to form C40 (Mo,Ti)Si 2 at 550°C. Crystal grains of metastable C40 TiSi 2 and equilibrium C54 TiSi 2 are found in the region near the interfacial (Mo,Ti)Si 2 layer due to the template phenomenon. Increasing the temperature to 600°C leads to the growth of C54 TiSi 2 throughout the film. No C49 grains can be detected. The findings confirm that the usual sequence for the formation of C54 TiSi 2, i.e. the C49 TiSi 2 forms first followed by a phase transition to the C54 TiSi 2, is altered by the interposed Mo layer. For a Mo/Ti bilayer on Si , the surface Mo layer is found to be present sequentially in (Mo,Ti) 5 Si 3 at 550°C, C49 (Mo,Ti)Si 2 at 600°C and C54 (Mo,Ti)Si 2 at 650°C. The bulk Ti beneath forms the C54 TiSi 2 following the usual route through the C49-C54 phase transition. However, this transition is now enhanced, in comparison with the C54 TiSi 2 formation with pure Ti , by the C54 (Mo,Ti)Si 2 atop that plays the role as a template precisely as the interfacial C40 (Mo,Ti)Si 2.