Influence of impurities on ion beam induced TiSi 2 formation

Abstract

For silicide formation, ion beam induced silicidation seems to be superior to thermal silicidation because the mixing destroys contaminants at the metal/Si interface resulting in reproducible, homogeneous silicide formation. However, it is not known if a high impurity content in the metal film has an influence on ion beam induced silicidation. Therefore, we studied the effect of oxygen and arsenic on TiSi 2 formation by ion beam mixing and subsequent rapid thermal annealing (RTA). For this purpose, Ti layers containing two different oxygen contents were prepared by sputtering. Then, mixing with As and Ge ions at different energies and doses and a subsequent two-step RTA treatment were performed. By RBS and cross-sectional TEM analysis, it could be detected that only Ge mixing with a maximum implanted concentration in the substrate and thermal reaction of pure Ti films resulted in lateral homogeneous TiSi 2 layers. All other mixing conditions led to inhomogenous, high-resistivity silicide layers consisting of large TiSi 2 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.