Lowering the formation temperature of the C54-TiSi₂ phase using a metallic interfacial layer

Abstract

We demonstrate that the formation temperature of the C54 TiSi₂ phase from the bilayer reaction of Ti on Si is lowered by approximately 100 °C by placing an interfacial layer of Mo or W between Ti and Si. Upon annealing above 500 °C, the C49 TiSi₂ phase forms first, as in the reaction of Ti directly on Si. However, the temperature range over which the C49 phase is stable is decreased by approximately 100 °C, allowing C54 TiSi₂ formation below 700 °C. Patterned submicron lines (0.25−1.0 μm wide) fabricated without the Mo layer contain only the C49 TiSi₂ phase after annealing to 700 °C for 30 s. With a Mo layer less than 3 nm thick between Ti and Si, however, a mixture of C49 and C54 TiSi₂ was formed, resulting in a lower resistivity. The enhanced formation of the C54 TiSi₂ is attributed to an increased density of nucleation sites for the C49-C54 phase transformation, arising from a finer grained precursor C49 phase.