Metal–semiconductor interfacial reactions: Ni/Si system

Abstract

Interfacial reactions between Si and deposited metals have been investigated by x-ray photoelectron spectroscopy (XPS) and channeling measurements with MeV 4He ions. This paper is concerned with reactions of Ni deposited at 10−10 Torr on clean Si and with the structure of the interface in the Si/Ni2Si/Ni structure. Both XPS and channeling measurements show that reactions occur where Ni is deposited at 10−10 Torr on Si: Si atoms are displaced from lattice sites, the Ni atoms are in an Si-rich environment, and the Ni/Si interface is graded in composition. Composition gradients are present at both interfaces in the Si/Ni2/Si/Ni system: at the Si/Ni2Si interface Ni atoms are in a more Si-rich environment than that found for Ni in Ni2Si or NiSi and at the Ni/Ni2Si interface Si atoms are in more Ni-rich environment than that found for Si in Ni2Si. In both deposited Ni on Si and the Si/Ni2Si/Ni structures, Ni atoms are found at the tetrahedral interstitial site in Si. For the Ni–Si system, cooling the substrate to ∠100 K slows down the reaction rate. The temperature dependence of the interfacial reactivity indicates the kinetic nature of metal–semiconductor interfaces.