Thermal expansion and stress development in the first stages of silicidation in Ti/Si thin films

The structural evolution in fiber-textured Ti/Si thin films has been investigated by in situ x-ray diffraction, in a temperature range preceding the formation of silicide compounds. At low temperature, thermoelastic behavior of the metallic film was observed. Abnormal thermal behavior of both 002 and 101 diffraction profiles was observed at 360 and 450degreesC, which could be understood in terms of Si diffusion, first in Ti grain boundaries, then, into the grains. By combining ex situ strain studies with analysis of the Si local environment in the whole Ti silicide family from Ti5Si3 to TiSi2, it was possible to determine the stress-free lattice parameters of annealed films. They are significantly higher than the bulk parameters, and indicate that nearly 4.5 at. % Si is present in the Ti grains.