Formation and characterization of ultra-thin Ni silicides on strained and unstrained silicon

Ultra thin Ni-silicides were formed on silicon-on-insulator (SOI) and biaxially tensile strained Si-on-insulator (SSOI) substrates. Epitaxial NiSi₂ layers were formed with a 3 nm Ni layer at T > 400°C, while a polycrystalline NiSi layer was with a 5 nm thick Ni layer. The NiSi₂ layer quality advances with increasing temperature. A very thin Pt interlayer, to incorporate Pt into NiSi, forming Ni_1-xPt_xSi, improves the thermal stability, the interface roughness and lowers the contact resistivity. The Schottky barrier heights (SBH) of these silicides were measured on n-Si(100). Ni_1-xPt_xSi shows the highest SBH. The SBH of NiSi₂ layers decreases by improving the layer interface. Surprisingly, the contact resistivity of epitaxial NiSi₂ is about one order of magnitude lower than that of NiSi on both, As and B doped SOI and SSOI, The lowest value of 7 × 10^-8 Ω cm² was measured on B doped SSOI.