Epitaxial silicide formation by multi-shot irradiation of Ni thin films on Si with Nd laser

Abstract

Uniform and epitaxial NiSi2 layers were obtained by consecutive irradiation of a Ni thin layer deposited onto Si with Nd-glass laser irradiation, 30-ns pulse duration, using up to 15 shots. The best quality epitaxial NiSi2 layer, for a 50-nm-thick Ni layer deposited on Si(111), was obtained with 10 shots of 1.3 J/cm2 energy density. The normalized minimum yield of the Ni signal amounted to 25%. The stability of the formed compound was investigated by furnace annealing in the 300–800 °C temperature range. After annealing at 300 °C-1 h backscattering and channeling analysis indicated a worsening of the epitaxial quality of the compound. X-ray diffraction patterns showed the presence of the NiSi silicide in addition to the NiSi2 silicide. At 500 °C-1 h annealing the reaction occurred over long distance and a large amount of NiSi was formed at the expense of the NiSi2 and the unreacted Ni. At 800 °C the epitaxial quality of the NiSi2 improved and the Ni minimum yield reached 10%. The NiSi2 was the only silicide present after irradiation and 800 °C-1 h annealing. Channeling analysis established also that the NiSi2 was b type: i.e., the silicide layer was rotated 180° about the surface normal 〈111〉 axis of the Si substrate.