Process strain induced by nickel germanide on (100) Ge substrate

Nickel germanides was formed on crystalline n-Ge (100) substrate by conventional RTA annealing at temperatures ranging from 300°C to 600°C. The XRD result reveals that only the NiGe phase is observed during this process temperature range. The orthorhombic structure of NiGe also induces epitaxial tensile strain on Ge substrate (i.e., NiGe itself is compressively strained) due to the difference in the lattice constants. The nickel-germanide/n-Ge Schottky contacts also reveals the slightly increasing electron barrier height (¿_bn) with the increasing annealing temperature which confirms the Ge substrate is under tensile strain. The compressively strained NiGe, like compressive contact-etching-stop-layer (CESL), is beneficial for PMOS mobility enhancement.