KINETICS OF THE FORMATION OF C49 TISI2 FROM TI-SI MULTILAYERS AS OBSERVED BY IN-SITU STRESS MEASUREMENTS

The formation of C49 TiSi2 from sputter-deposited amorphous Ti-Si mult ilayers on Si(100) substrates was studied during isochronal and isothe rmal heat treatment. The formation process was analyzed for multilayer periodicities (i.e., the thickness of one Ti and one Si layer) of 1, 5, and 12 nm, respectively, by in situ stress measurements and differe ntial scanning calorimetry (DSC). A strong correlation between the evo lution of the stress and the formation of the C49 TiSi2 phase was foun d. During heat treatment an abrupt change of the stress in the film wa s observed. DSC and x-ray diffraction experiments revealed that this c hange of the stress coincides with the formation process of the C49 Ti Si2 phase. The transition temperature of the Ti-Si multilayer to the C 49 TiSi2 phase shifts from approximately 295 to approximately 550-degr ees-C with increasing multilayer periodicity. From kinetic analysis of the experiments the activation energy of the C49 TiSi2 phase formatio n process was acquired. For the smallest periodicity of 1 nm an effect ive activation energy of 170+/-25 kJ/mol was found, for multilayers wi th 12 nm periodicity the activation energy was 280+/-40 kJ/mol. The di fference in activation energy is explained by different rate-limiting steps during silicide formation as a function of the multilayer period icity. DSC measurements revealed two processes during the formation of the C49 TiSi2 phase: mixing and crystallization. The enthalpy for mix ing for Ti-Si multilayers with periodicities of 1 and 12 nm was -38 an d -33 kJ/mol, respectively. The crystallization enthalpy was comparabl e for both periodicities: -5 kJ/mol.