Ultrathin epitaxial Ni-silicide contacts on (1 0 0) Si and SiGe: Structural and electrical investigations

Abstract

The formation of epitaxial NiSi2 and NiSiGe layers is investigated. On Si(100) epitaxial NiSi2 is obtained at T>400^oC with a Ni layer thickness below 3nm, while polycrystalline NiSi layer is produced with a 5nm thick Ni layer. With increasing silicidation temperature, epitaxial NiSi2 layers show a higher single crystalline quality, a lower resistivity and a lower Schottky barrier height to electrons. We highlight the extremely low contact resistivity of epitaxial NiSi2, which is about one order of magnitude lower than that of NiSi on both, As and B doped SOI. Epitaxial NiSiGe is also obtained on (100) SiGe employing an Al interlayer mediated epitaxy growth method. The Al atoms from the original 3nm interlayer diffused towards the surface during annealing. The incorporation of some Al increases the transition temperature from the Ni-rich germano-silicide phase to the mono-germano-silicide phase. The formed epitaxial NiSi0.7Ge0.3 shows an orthorhombic structure with a (101) base plane rotated by 45^o with respect to the (100) Si0.7Ge0.3 substrate.