Silicide-phase evolution and platinum redistribution during silicidation of Ni 0.95Pt 0.05/Si(100) specimens

Praneet Adusumilli, David N. Seidman*, Conal E. Murray

*Corresponding author for this work

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

We investigated the temporal evolution of nickel-silicide phase-formation and the simultaneous redistribution of platinum during silicidation of a 10 nm thick Ni 0.95Pt 0.05 film on a Si(100) substrate. Grazing incidence x-ray diffraction (GIXRD) and atom-probe tomography (APT) measurements were performed on as-deposited films and after rapid thermal annealing (RTA) at 320 or 420 °C for different times. Observation of the Ni 2Si phase in as-deposited films, both with and without platinum alloying, is attributed to surface preparation. RTA at 320 °C for 5 s results in the formation of the low-resistivity NiSi intermetallic phase and nickel-rich phases, Ni 2Si and Ni 3Si 2, as demonstrated by GIXRD measurements. At 420 °C for 5 s, the NiSi phase grows outward from the silicide/Si(100) interface by consuming the nickel-rich silicide phases. On increasing the annealing time at 420 °C to 30 min, this reaction is driven towards completion. The nickel-silicide/silicon interface is reconstructed in three-dimensions employing APT and its chemical root-mean-square roughness, based on a silicon isoconcentration surface, decreases to 0.6 nm with the formation of the NiSi phase during silicidation. Pt redistribution is affected by the simultaneous reaction between Ni and Si during silicidation, and it influences the resulting microstructure and thermal stability of the NiSi phase. Short-circuit diffusion of Pt via grain boundaries in NiSi is observed, which affects the resultant grain size, morphology, and possibly the preferred orientation of the NiSi grains. Pt segregates at the NiSi/Si(100) heterophase interface and may be responsible for the morphological stabilization of NiSi against agglomeration to temperatures greater than 650 °C. The Gibbsian interfacial excess of Pt at the NiSi/Si(100) interface after RTA at 420 °C for 5 s is 1.2 ± 0.01 atoms nm -2 and then increases to 2.1 ± 0.02 atoms nm -2 after 30 min at 420 °C, corresponding to a decrease in the interfacial free energy of 7.1 mJ m -2.

Original languageEnglish (US)
Article number064307
JournalJournal of Applied Physics
Volume112
Issue number6
DOIs
StatePublished - Sep 15 2012

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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