INTERFACIAL REACTION BETWEEN A NI/GE BILAYER AND SILICON (100)

The sequential formation and dissociation of compounds in the Ni/Ge/Si(100) system have been studied by using Rutherford backscattering spectroscopy, Auger depth profiling, x-ray diffraction, and cross-sectional transmission electron microscopy. Ni2Ge phase is formed first on the Si substrate at 250 °C. A layered structure of NiGe/NiSi/Si(100) is formed after thermal annealing at 350 °C. Upon annealing from 350 to 425 °C, the NiGe phase dissociates, inducing further growth of NiSi phase at the nickel germanide/Si(100) interface. The NiSi phase grows with a (time)1 /2 dependence and with an activation energy of 2.1 eV. Marker experiment shows that Ni is a dominant moving species. The dissociation of NiGe lead to an extensive redistribution of Ge and Ni with a configuration of Ge66Si17Ni1 7/NiSi/Si(100) and this layered structure remains stable until 680 °C. Cross-sectional transmission electron microscopy results show that there are polycrystalline Ge plus a ternary NiSiGe phase on the top layer. High-temperature annealing (>680 °C) induces the inward diffusion of Ge to form a Ge-rich layer on the Si substrate.