Solid-phase reactions in Ir/(111)Si systems studied by means of x-ray emission spectroscopy
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Solid-phase reactions in Iryy(111)Si systems studied by means of x-ray emission spectroscopy E. Z. Kurmaev, V. R. Galakhov, and S. N. Shamin Institute of Metal Physics, Russian Academy of Science – Ural Division, 620219 Yekaterinburg GSP-170, Russia
T. Rodr´ıguez, A. Almendra, and J. Sanz-Maudes Dept. Tecnolog´ıa Electr´onica, ETSI Telecomunicaci´on – Univ. Polit´ecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
K. G¨oransson and I. Engstr¨om Institute of Chemistry, University of Uppsala, Box 531, S-751 21, Uppsala, Sweden (Received 24 May 1996; accepted 23 September 1997)
High energy resolved x-ray emission spectroscopy with variable electron beam excitation is applied for study of solid-phase reactions in the Iry(111)Si system as a function of annealing temperature. The formation of Ir silicides as a function of depth is studied by measurements of Si L2,3 x-ray emission valence spectra at different electron excitation energies (3–10 keV), and the results are compared with those of Rutherford backscattering.
I. INTRODUCTION
The study of the formation of silicide phases in the IrySi system is of great interest because of applications of Ir1 Si1 -Si Schottky detectors in the 8–14 mm atmospheric window.1,2 In Refs. 3 and 4 iridium films deposited on (111)Si substrates and annealed at 350– 500 ±C were studied by Rutherford backscattering spectrometry and Auger electron spectroscopy, and the possibility to grow iridium silicides Ir1 Si1 and Ir3 Si5 by rapid thermal annealing (RTA) in vacuum was demonstrated. In the present paper the influence of increased annealing temperature (T ann 675 ±C) on the formation of silicide phases as a function of processing time (t 50–710 s) is studied with the help of two different methods: x-ray emission spectroscopy (XES) with highenergy resolution and variable electron excitation and Rutherford backscattering spectrometry (RBS). The application of x-ray emission spectroscopy (XES) for analysis of a solid phase reaction in metal/ silicon systems is based on the great sensitivity of the fine structure of x-ray spectra to the chemical bonding. A Si L2,3 x-ray emission spectrum arises from a radiative transition between the valence states and the Si 2p core level following ionization of the Si 2p electrons by primary excitation. As a result of the dipole selection rules, Si L2,3 spectra reveal the 3s plus 3d partial density of states localized on the silicon atoms. In previous publications5–8 it was shown that these spectra are different in pure Si and transition metal silicides. This allows the determination of the silicide formation in transition metal/silicon systems and the distinguishing of different silicide phases. 1950
http://journals.cambridge.org
J. Mater. Res., Vol. 13, No. 7, Jul 1998
Downloaded: 28 Mar 2015
On the other hand, the x-ray technique can be used as a tool for nondestructive depth profiling analysis because of pronounced dependence of x-ray yield as a function of the electron excitation depth.
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