Germanium-induced texture and preferential orientation of NiSi_(1-x)Ge_x layers on Si_(1-x)Ge_x

摘要

NiSi_(1-x)Ge_x films on compressively strained as well as relaxed undoped Si_(1-x)Ge_x epitaxially grown substrates with x=0.06-0.30 on Si(001) wafers have been studied with respect to the relative orientation of film and substrate after annealing at temperatures in the range 400-850℃. Using x-ray diffraction, transmission electron microscopy, and pole-figure measurements, it was found that only the monogermanosilicide phase formed above 450℃ and was the only phase still at 850℃. New information regarding the effects of Ge on the silicidation of Ni was also found. Thus, the preferred plane parallel to the surface is (013). Compared to NiSi, Ge suppresses the development of the other planes parallel to the surface except (013). Within this plane, the orientations of the grains pile up in such a way that the configuration NiSi_(1-x)Ge_x[100]//Si_(1-x)Ge_x[100] is avoided, which in the pole-figures leads to broad peaks in-between the substrate [100] and [010]. In addition, peaks indicating the epitaxial alignment NiSi_(0.8)Ge_(0.2)(±21-1) or (±2-11)//Si_(0.8)Ge_(0.2)(±2±20) coupled with NiSi_(0.8)Ge_(0.2)(±100) ≈ //Si_(0.8)Ge_(0.2)(±100) or (0±10) were found. Fine structure in the broad peaks is found to be due to lateral epitaxial alignments between grains along their common grain boundary. Based on the nonex- istence of NiGe_2, the observations are interpreted in terms of Ge preventing the formation of certain Ni-Ge bonds at the interface between NiSi_(1-x)Ge_x and the Si_(1-x)Ge_x substrate.