Effects of additive elements on the phase formation and morphological stability of nickel monosilicide films

Alloying elements can substantially affect the formation and morphological stability of nickel monosilicide. A comprehensive study of phase formation was performed on 24 Ni alloys with varying concentrations of alloying elements. Silicide films have been used for more than 15 years to contact the source, drain and gate of state-of-the-art complementary-metal-oxide-semiconductor (CMOS) devices. In the past, the addition of alloying elements was shown to improve the transformation from the high resistivity C49 to the low resistivity C54-TiSi 2 phase and to allow for the control of surface and interface roughness of CoSi 2 films as well as produce significant improvements with respect to agglomeration of the films. Using simultaneous time-resolved X-ray diffraction (XRD), resistance and light scattering measurements, we follow the formation of the silicide phases in real time during rapid thermal annealing. Additions to the Ni–Si system lead to modifications in the phase formation sequence at low temperatures (metal-rich phases), to variations in the formation temperatures of NiSi and NiSi 2, and to changes in the agglomeration behavior of the films formed. Of the 24 elements studied, additions of Mo, Re, Ta and W are amongst the most efficient to retard agglomeration while elements such as Pd, Pt and Rh are most efficient to retard the formation of NiSi 2.