High-Resolution Transmission Electron Microscopy of Interfaces between thin Nickel Layers on Si(001) After Nickel Silicide Formation under Various Annealing Conditions

Local structures of nickel silicide formed by heat treatment of a nickel layer sputtered on silicon (100) substrate were observed by high-resolution transmission electron microscopy. In the specimen as-sputtered and after heat treatment at 498K, a thin layer was found at the interface between Ni (Ni₂Si) and the Si substrate. The layer was an initial phase of silicidation and seems to be non-fluorite type NiSi₂. When annealed around 600K, the NiSi₂ phase disappeared and a NiSi phase grew dominantly. At the interface of NiSi/Si, the crystal lattices appeared smooth, because the lattice mismatch between NiSi and Si was absorbed by lattice distortion within a few atomic layers of the interface. The Ni₃Si₂ and Ni₂Si phases remaining in the grown NiSi layer were also identified by Fourier analysis of the lattice fringe