Raman spectroscopic study of the formation of t‐MoSi₂ from Mo/Si multilayers

We have used Raman spectroscopy, large‐ and small‐angle x‐ray diffraction spectroscopy of sputter‐deposited, vacuum‐annealed, soft x‐ray Mo/Si thin‐film multilayers to study the physics of silicide formation. Two sets of multilayer samples with d‐spacing 8.4 and 2.0 nm have been studied. Annealing at temperatures above 800 °C causes a gradual formation of amorphous MoSi₂ interfaces between the Si and Mo layers. The transition from amorphous to crystalline MoSi₂ is abrupt. The experimental results indicate that nucleation is the dominant process for the early stage and crystallization is the dominant process after nucleation is well advanced. In the thicker multilayer, a portion of the silicon crystallizes during annealing and a strong Raman signal is observed. An advantage of Raman spectroscopy is that the Raman signal of the silicide is observed even before the presence of MoSi₂ can be seen using x‐ray diffraction. This study indicates that Raman spectroscopy is an effective technique for characterizing the formation of crystalline silicides.