Abstract: AES study of the silicide formation in 85%Ni–15%Pt alloy films

Abstract

Metal silicides such as NiSi and PtSi have important applications in integrated circuit technology, particularly in the fabrication of Schottky barrier diodes with reproducible barrier heights. The barrier heights of PtSi–nSi and NiSi–nSi are 0.85 and 0.65 eV, respectively. With a view to obtaining a barrier height in between those of PtSi and NiSi, Ni–Pt alloy films were sputter deposited on n‐type silicon from a single‐alloy target of composition 85wt %Ni–15wt% Pt and sintered at 475 °C for 20 min to form a silicide. The surface composition and the depth‐compositional profile were determined by Auger electron spectroscopy (AES) coupled with Ar+ ion sputtering. The characteristic Auger spectra from PtSi and NiSi showed significant chemical effects. The LVV Auger spectrum from silicon in PtSi revealed pronounced line‐shape changes from that characteristic of elemental silicon. In the case of NiSi, however, no pronounced line‐shape changes in the Si LVV Auger spectrum could be observed, while strong characteristic energy‐loss peaks associated with the Ni Auger peaks were evident. Comparing the Pt and Ni Auger peak heights from the corresponding silicides with those from the standards, it appeared that the stoichiometry was Pt2Si or Ni2Si. A thin layer of SiO2 was formed at the surface of all samples after the heat treatment. Platinum, which was uniformly distributed in depth in the as‐deposited Ni–Pt alloy films, on sintering, was found to accumulate at two regions close to the silicide–vacuum interface and close to but not at the silicide–silicon interface. The composition of the silicide–silicon interface appeared to be essentially nickel silicide. The barrier height φB of the alloy silicide on n‐type Si was measured by fabricating guard ring Schottky diodes and measuring the I–V characteristics and was found to be 0.7 eV. The increase in φB from that characteristic of NiSi could not be explained by the compositional changes at the silicide–silicon interface.