INFLUENCE OF IMPURITIES ON ION-BEAM-INDUCED TISI2 FORMATION

For silicide formation, ion beam induced silicidation seems to be supe rior to thermal silicidation because the mixing destroys contaminants at the metal/Si interface resulting in reproducible, homogeneous silic ide formation. However, it is not known if a high,impurity content in the metal film has an influence on ion beam induced silicidation. Ther efore, we studied the effect of oxygen and arsenic on TiSi2 formation by ion beam mixing and subsequent rapid thermal annealing (RTA). For t his purpose, Ti layers containing two different oxygen contents were p repared by sputtering. Then, mixing with As and Ge ions at different e nergies and doses and a subsequent two-step RTA treatment were perform ed. By RBS and cross-sectional TEM analysis, it could be detected that only Ge mixing with a maximum implanted concentration in the substrat e and thermal reaction of pure Ti films resulted in lateral homogeneou s TiSi2 layers. All other mixing conditions led to inhomogeneous, high -resistivity silicide layers consisting of large TiSi2 grains embedded in TiSi. Therefore, it can be concluded that impurities which have a high affinity to Ti can strongly affect ion beam induced silicidation.