ON THE FORMATION OF MOLYBDENUM SILICIDES IN MO-SI MULTILAYERS - THE EFFECT OF MO THICKNESS AND ANNEALING TEMPERATURE

The present work deals with the formation of molybdenum silicides in all-sputtered a-Si/Mo/a-Si/Mo/a-Si/c-Si(100) multilayers. The structures were prepared without breaking the vacuum and the substrates were not intentionally heated during the sputtering. After deposition, the multilayers were annealed at 500 or 700-degrees-C. Grazing incidence X-ray diffraction and XPS techniques were used to characterize the Mo/a-Si and a-Si/Mo structures first and then the a-Si/Mo/a-Si/Mo/a-Si/c-Si(100) multilayers. The essential results can be summarized as follows: (1) The nature of the interface formed in the unannealed structures depends strongly on the order of the deposits: if Si is sputtered onto sputtered Mo films, the a-Si/Mo interface is found to be abrupt while in the reverse order the deposit leads to a diffuse Mo/a-Si interface. (2) The thermal treatment has a significant effect only if the temperature is of the order of 700-C. In this case, the result depends on the a-Si and Mo thicknesses: for thicknesses lower than approximately 200 angstrom only MoSi2 is formed, with predominance of the hexagonal phase, while for thicknesses greater than approximately 200 angstrom, we simultaneously observe the tetragonal phases MoSi2 and Mo5Si3.