In situ study of the growth properties of Ni-rare earth silicides for interlayer and alloy systems on Si(100)

摘要

We report on the solid-phase reaction of thin Ni-rare earth films on a Si(100) substrate, for a variety of rare earth (RE) elements (Y, Gd, Dy, and Er). Both interlayer (Ni/RE/(Si)) and alloy (Ni-RE/(Si)) configurations were studied. The phase sequence during reaction was revealed using real-time x-ray diffraction whereas the elemental diffusion and growth kinetics were examined by real-time Rutherford backscattering spectrometry. All RE elements studied exert a similar influence on the solid phase reaction. Independent of the RE element or its initial distribution a ternary Ni_2Si_2RE phase forms, which ends up at the surface after NiSi growth. With respect to growth kinetics,- the RE metal addition hampers the Ni diffusion process even for low concentrations of 2.5 at. %, resulting in the simultaneous growth of Ni-rich silicide and NiSi. Moreover, the formation of Ni_2Si_2RE during NiSi growth alters the Ni diffusion mechanism in the interlayer causing a sudden acceleration of the Ni silicide growth. Besides a significant effect on the silicide growth, we have found that adding 5 at. % Er (relative to Ni) lowers the NiSi Schottky barrier height on n-type Si(100) by approximately 0.1 eV for the interlayer and alloy configuration.