A comparison between thermal annealing and ion mixing of alloyed Ni-W films on Si. I

The reactions between Ni-W alloys and Si〈100〉 substrates induced by thermal annealing and ion mixing were investigated and compared. Samples were prepared by sputtering of Ni-W alloys, both Ni-rich and W-rich, onto the Si〈100〉 substrates, and followed by either furnace annealing (200–900 °C) or ion mixing (2×1015– 4×1016 86Kr+ ions/cm2). The reactions were analyzed by Rutherford backscattering and x-ray diffraction (Read camera). In general, thermal annealing and ion mixing lead to similar reactions. Phase separation between Ni and W with Ni silicides formed next to the Si substrate and W silicide formed on the surface was observed for both Ni-rich and W-rich samples under thermal annealing. Phase separation was also observed for Ni-rich samples under ion mixing; however, a Ni-W-Si ternary compound was possibly formed for ion-mixed W-rich samples. These reactions were rationalized in terms of the mobilities of various atoms and the energetics of the systems.